Treatment Plant Design

Information & Technology Group Operational Technology

STANDARD DESIGN DS 45-06

Treatment Plant Design

VERSION 1

REVISON 0

May 2021

Standard Design No. DS45-06 Treatment Plant Design

Uncontrolled if Printed Ver 1 Rev 0

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© Copyright Water Corporation 2021-2024

FOREWORD

Operational Technology Standard Designs are prepared in order to ensure that assets are delivered efficiently and

perform in a consistent manner. Having standard designs simplifies the delivery process considerably thereby

reducing costs and decreasing delivery times.

The Standard Design has been developed as a collaborative effort involving Water Corporation and industry

experts. Any deviation from this design must be justifiable and must be approved by the Head of Operational

Technology.

Users are invited to forward submissions for continuous improvement to the Principal SCADA Engineer who will

consider these for incorporation into future revisions.

Head of Operational Technology

This document is prepared without the assumption of a duty of care by the Water Corporation. The document is

not intended to be nor should it be relied on as a substitute for professional engineering design expertise or any

other professional advice.

It is the responsibility of the user to ensure they are using the current version of this document.

© Copyright – Water Corporation: This standard and software is copyright. With the exception of use permitted

by the Copyright Act 1968, no part may be reproduced without the written permission of the Water Corporation.



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DISCLAIMER

Water Corporation accepts no liability for any loss or damage that arises from anything in the

Standards/Specifications including any loss or damage that may arise due to the errors and omissions of any person.

Any person or entity which relies upon the Standards/Specifications from the Water Corporation website does so at

their own risk and without any right of recourse to the Water Corporation, including, but not limited to, using the

Standards/Specification for works other than for or on behalf of the Water Corporation.

The Water Corporation shall not be responsible, nor liable, to any person or entity for any loss or damage suffered

as a consequence of the unlawful use of, or reference to, the Standards/Specifications, including but not limited to

the use of any part of the Standards/Specification without first obtaining prior express written permission from the

CEO of the Water Corporation.

Any interpretation of anything in the Standards/Specifications that deviates from specific Water Corporation Project

requirements must be referred to, and resolved by, reference to and for determination by the Water Corporation’s

Project Manager and/or designer for that particular Project.



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REVISION STATUS

The revision status of this standard is shown section by section below:

REVISION STATUS

SECT. VER.

/REV. DATE

PAGES

REVISED

REVISION DESCRIPTION

(Section, Clause, Sub-

Clause)

RVWD. APRV.

1 1/0 27/05/2021 All New document CM JGB

2 1/0 27/05/2021 All New document. Migrated

from DS28 1/7, Appendix 1

with updates.

CM JGB



with updates.

CM JGB



with updates.

CM JGB



with updates.

CM JGB



with updates.

CM JGB

App. A 1/0 27/05/2021 All New document. Migrated


with updates.

CM JGB

App. B 1/0 27/05/2021 All New document. Migrated


with updates.

CM JGB



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STANDARD DESIGN DS 45-06


CONTENTS

Section Page

1 INTRODUCTION ................................................................................................................... 8

1.1 Purpose ..................................................................................................................................... 8

1.2 Scope ......................................................................................................................................... 8

1.3 References ................................................................................................................................. 8

1.4 Definitions ................................................................................................................................. 9 1.4.1 Plant Control System (PCS) .................................................................................................... 10 1.4.2 Plant Safeguarding ................................................................................................................... 10 1.4.3 Supervisory Control and Data Acquisition (SCADA) System ................................................ 11

1.5 Abbreviations ......................................................................................................................... 11

2 DESIGN .................................................................................................................................. 13

2.1 Design Process ........................................................................................................................ 13

2.2 System Architecture .............................................................................................................. 13 2.2.1 General ..................................................................................................................................... 13 2.2.2 Plant Control System ............................................................................................................... 15 2.2.2.1 SCADA System ......................................................................................................................... 16

2.3 Control Philosophy ................................................................................................................ 17 2.3.1 Control Mode Selection ........................................................................................................... 17 2.3.2 Control Location Selection ...................................................................................................... 17 2.3.3 Control Hierarchy .................................................................................................................... 17 2.3.4 Equipment Status, Faults and Alarms ...................................................................................... 18

2.4 Communications .................................................................................................................... 18 2.4.1 General ..................................................................................................................................... 18 2.4.1.1 SCADA Communications ......................................................................................................... 18

2.4.1.2 Peer to Peer Communications ................................................................................................. 19

2.4.1.3 Local Area Networking ............................................................................................................ 19

2.4.1.4 I/O Networking and Fieldbuses ............................................................................................... 20

2.4.2 PCS Communications with Process Equipment ...................................................................... 20 2.4.3 Communications with Field Instruments and Control Devices ............................................... 20

2.5 Plant Control .......................................................................................................................... 21 2.5.1 General ..................................................................................................................................... 21 2.5.1.1 Remote Terminal Units ............................................................................................................ 21

2.5.1.2 Programmable Logic Controllers ............................................................................................ 21

2.5.2 Selection .................................................................................................................................. 23

2.6 Monitoring and Control ........................................................................................................ 24 2.6.1 General ..................................................................................................................................... 24 2.6.1.1 Utility Wide SCADA System (SCADA) .................................................................................... 24

2.6.1.2 Local Area Replication Server ................................................................................................. 24

2.6.1.3 Local Area Standalone Server ................................................................................................. 24



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Section Page

2.6.1.4 Site Operator Interface Panel and Local Display Panels........................................................ 24

2.6.2 Selection .................................................................................................................................. 24 2.6.2.1 LARS vs LASS .......................................................................................................................... 24

2.6.2.2 OIPs ......................................................................................................................................... 26

2.7 Process Instrumentation ........................................................................................................ 26

2.8 Sub-Systems ............................................................................................................................ 26 2.8.1 Vendor Equipment Packages ................................................................................................... 26 2.8.2 Small Vendor Equipment Control Cubicles ............................................................................ 27 2.8.3 Ancillary Systems .................................................................................................................... 28 2.8.3.1 Security Access Control Systems ............................................................................................. 28

2.8.3.2 CCTV ....................................................................................................................................... 28

2.9 Access and Privileges ............................................................................................................. 28

2.10 Power Supply ......................................................................................................................... 28 2.10.1 General ..................................................................................................................................... 28 2.10.1.1 AC UPS Systems ...................................................................................................................... 28

2.10.1.2 DC UPS / Battery Charger Systems......................................................................................... 28

2.10.2 Selection .................................................................................................................................. 29

3 INSTALLATION SPECIFICATION .................................................................................. 30

3.1 General .................................................................................................................................... 30 3.1.1 Network Cabling ...................................................................................................................... 30 3.1.2 Communications Cabling ........................................................................................................ 30 3.1.3 Field Instrument Cabling ......................................................................................................... 30 3.1.4 Instrument Installation ............................................................................................................. 31 3.1.5 Instrument Junction Boxes ....................................................................................................... 31 3.1.6 Switchrooms and Control Rooms ............................................................................................ 31

4 APPROVED EQUIPMENT LIST........................................................................................ 32

5 HAZARDOUS AREAS ......................................................................................................... 33

5.1.1 General ..................................................................................................................................... 33 5.1.2 Competency Requirements ...................................................................................................... 33 5.1.3 Area Classification ................................................................................................................... 33 5.1.4 Equipment Selection ................................................................................................................ 33 5.1.4.1 Use of Certified Equipment ...................................................................................................... 33

5.1.4.2 Explosion-Protection Techniques ............................................................................................ 33

5.1.4.3 Corrosive Environments .......................................................................................................... 34

5.1.5 Installation ............................................................................................................................... 34 5.1.6 Documentation ......................................................................................................................... 34 5.1.7 Testing and Inspection ............................................................................................................. 34

6 WORK ON EXISTING TREATMENT PLANTS ............................................................. 35

6.1.1 General ..................................................................................................................................... 35 6.1.1.1 Site Survey ............................................................................................................................... 35

6.1.1.2 Standards and Regulations ...................................................................................................... 35

6.1.1.3 Safety and Environmental Issues ............................................................................................. 35

6.1.1.4 Numbering ............................................................................................................................... 36

6.1.2 Plant Control Systems .............................................................................................................. 36 6.1.3 Programmable Controllers ....................................................................................................... 36 6.1.4 Data communications .............................................................................................................. 36 6.1.5 Field Instrumentation ............................................................................................................... 36



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Section Page

6.1.6 Hazardous Areas ...................................................................................................................... 37

APPENDIX A TYPICAL CONTROL SYSTEM BLOCK DIAGRAMS .................................................. 38

APPENDIX B LARS & LASS ....................................................................................................................... 42



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1 INTRODUCTION

1.1 Purpose

This document describes the standard design practice for the Operational Technology (OT) component

of treatment plants. It shall be used when implementing OT elements on new and existing Water

Corporation treatment plants.

1.2 Scope

This standard covers the design of the control and monitoring equipment. It does not cover the design

of the electrical installation. Electrical design is described in electrical standards available from Water

Corporation’s Engineering business unit.

This standard design practice shall apply to all treatment plant projects.

1.3 References

DS 20 Design Process for Electrical Works

DS 21 Design Standard – Large Pump Stations

DS 22 Design Standard – Ancillary Plant and Small Pump Stations

DS 26-30 Type Specification for Double Conversion Low Voltage Uninterruptible Power Supply

DS 26-31 Type Specification for Line Interactive Low Voltage Uninterruptible Power Supply

DS 40 Design Process for SCADA Works

DS 40-01 Control Philosophy

DS 40-02 Naming Convention

DS 40-03 IO Addressing

DS 40-04 IO Lists

DS 40-05 Scheme Control

DS 40-06 Software Change Control

DS 40-07 Electrically Actuated Valve Control

DS 40-08 Standard for the Control of Chemical Dosing

DS 40-09 Field Instrumentation

DS 42-01 VSAT Installation Standard

DS 42-02 SCADA Radio Network Design

DS 42-03 Scheme SCADA Equipment and Installation

DS 42-04 Communications Power Supply

DS 42-05 SCADA 4G Design and Measurements

DS 43-01 DNP3 Polling

DS 43-04 Profinet and Profibus Network Design and Installation

DS 43-05 IP Network Design

DS 43-06 Fibre Optic Network Design and Installation



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FS00 Electrical Standard Drawings – Major Pump Station

FS01 Electrical Standard Drawings – Small Pump Station

NE94 Field Instrumentation Drawings

MN01 Electrical Standard Switchboard Designs – Small Pump Stations

DS 45-01 Standard Design – Bores

DS 45-02 Standard Design – Wastewater Pump Stations

DS 45-03 Standard Design – Booster and Transfer Pump Stations

DS 45-04 Standard Design – Drainage Pump Stations

DS 45-07 Standard Design – Chlorinators

DS 45-09 Standard Design - Vacuum Pump Stations

59086142 LARS Assessment Table

1.4 Definitions

For the purposes of this standard, the following definitions shall apply:

Term Definition

Complex Plant A plant that features multiple process areas necessitating dedicated

controllers.

Corporation Water Corporation

Critical Plant

A plant where significant HSE risks may arise from failure in

operation therefore demanding higher availability. A simple or

complex plant may classify as a critical plant.

Critical

Safeguards

Instrumented safeguards that monitor for abnormal process

conditions or release of hazardous materials from the process and

initiate appropriate alarms and/or control actions to prevent serious

incidents or limit the consequences of a process event.

HMI

Human Machine Interface is a generic term for referencing a

monitoring and control facility. This term is used to refer to both

the SCADA System and OIP where present on the plant.

IED Intelligent Electronic Device. A microprocessor-based controller of

power system equipment.

OC Operations Centre – located in the John Tonkin Centre, Leederville

OIP Operator Interface Panel. An industrial touch screen panel used for

the purpose of local site monitoring and emergency control.

OT Operational Technology

Vendor

Equipment

Package

A package of equipment that is designed and supplied by a vendor,

often on a skid or module. Vendor equipment packages often offer

variable (optional) capabilities for alarm and controls interfacing

with the PCS

Process Area

Control

Cubicle

(PACC)

The cubicle which houses the Process Area Control System (PACS)

automation equipment.

Process Area

Control

System

(PACS)

The PLC(s) and associated ancillary equipment which form an

autonomous controlling system for a particular treatment process

area.

Plant Control

System (PCS)

The combination of all Process Area Control Systems (including

RTU/s) in the treatment plant.

https://nexus.watercorporation.com.au/otcs/cs.exe/app/nodes/59086142



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1.4.1 Plant Control System (PCS)

The function of the PCS is to control and protect the plant to meet the parameters set by operators. It

does this by:

(a) Monitoring inputs from sensors and instruments in the field;

(b) Responding to commands from the field and from the SCADA system;

(c) Directly controlling equipment and processes in response to field inputs and operator commands

according to logic programmed into its Programmable Logic Controllers (PLC(s)) and Remote

Terminal Units (RTU(s)).

1.4.2 Plant Safeguarding

The function of the safeguarding systems are to prevent, or limit the consequences of, abnormal process

conditions or the release of hazardous materials. Plant safeguarding is a separate design consideration

from process control as it must also consider the potential impacts of failures in the PCS. Therefore

individual plant safeguards may require different levels of independence from the PCS (eg. a separate

and dedicated field instrument (sensor) as input to a safeguarding function that is implemented within

the PLC where a hazardous event might be caused by a failure of the primary process control sensor.

Plant safeguarding functions are a separate design consideration from the plant control system and shall

be documented as per DS81 (e.g. Functional Control Description/Specification and P&ID Drawings).

PLC Programmable Logic Controller. A key element of the PCS.

Process “Process” refers to a specific operation or a stage of the treatment

carried out at the plant.

RTU

Remote Terminal Unit. A key element of the PCS with primary

function of being the DNP3 gateway device between the PCS and

the SCADA System.

Simple Plant

A plant that features a limited number of processes where a main

controller oversees the entire treatment provided by the plant.

These are typically smaller plants located in regional locations.

SCADA

System

The SCADA System is a software application running on standard

Water Corporation servers which monitors and controls the

operation of the various PACSs which make up the PCS. It

provides the capability to manually issue commands and setpoints to

the treatment plant either locally or remotely from the Operations

Centre. However, all automatic control functions shall be executed

within the various PACSs.

The SCADA System includes the primary and standby servers, on-

site and off-site workstations, data storage and retrieval systems,

and associated equipment including connections to the

Corporation’s corporate network. The current SCADA System used

by Water Corporation is Schneider Electric’s ClearSCADA.

Local Area

Replication

Server

Simple plants with local server installations will also have their

SCADA database hosted on the UWSS; with the local server

featuring a replicated site database from UWSS

Local Area

Standalone

Server

Complex plants with localised servers will also have remotely

hosted permanent standby servers accessible via the SCADA WAN;

the localised servers operate as stand-alone servers that

communicate with the PCS via OPC protocols



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1.4.3 Supervisory Control and Data Acquisition (SCADA) System

The SCADA system is the operator’s interface to the Plant Control System and Plant Safeguarding. It

shall be designed so as to provide a “window” to the plant and to perform the following functions:

(a) Display real-time operating data in a readily comprehensible form;

(b) Allow operators to start and stop equipment and processes, and adjust the process operating

parameters;

(c) Alert operators to abnormal or alarm conditions and allow appropriate actions to be taken

remotely (where practical) to restore normal operation or limit process downtime/loss;

(d) Facilitate on-site and off-site supervision of plant operation;

(e) Enable the preparation of reports;

(f) Collect and store trend and historical data for a period of 6 months;

(g) Enable plant data to be transferred to the Corporation’s corporate data systems;

(h) Via appropriate user privilege management, enable PCS and SCADA system operating

parameters from local and remote facilities (e.g. clients).

It is not the function of the SCADA system to automatically control equipment or processes directly; all

direct automatic process control shall be carried out by the PCS.

A SCADA system may be a locally or remotely hosted system or both. It is distinguished from an OIP

in that it is based on software that runs on desktop/server hardware. The operator interface to the

ClearSCADA system is via the ViewX application which can run on standard Water Corporation SOE

computers.

1.5 Abbreviations

CPU Central Processing Unit

CCB Change Control Board

DTE Data Terminal Equipment

ED Electrostatic Discharge

HMI Human Machine Interface

I/O Input/ Output

LAN Local Area Network

LARS Local Area Replication Server

LASS Local Area Standalone Server

OEM Original Equipment Manufacturer

OIP Operator Interface Panel

OT Operational Technology

PACC Process Area Control Cubicle

PACS Process Area Control System

PC Personal Computer

PCS Plant Control System



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PLC Programmable Logic Controller

RTU Remote Terminal Unit

R/W Read/ Write

SCADA Supervisory Control And Data Acquisition

SOE Standard Operating Environment

UPS Uninterruptible Power Supply

VSD Variable-Speed Drive



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2 DESIGN

2.1 Design Process

The design process to be followed for SCADA projects is described in DS40 Design Process for SCADA

Works which should be consulted before commencing a SCADA Project.

2.2 System Architecture

2.2.1 General

Figure 6-1 and Figure 6-2 in Appendix A show typical PCS block diagrams for a complex treatment

plant and a simple treatment plant respectively. The following description applies to both figures where

appropriate:

(a) The PCS LAN links all components of the PCS. For all but the smaller plants it typically

consists of one or more optic fibre cables. For larger plants it is typically configured as a closed

or self-healing ring to provide increased reliability. In complex plants where combined PCS

and SCADA system traffic may result in unacceptable delays on a single LAN, it may be

necessary to provide separate PCS and SCADA system LANs.

(b) The LAN switch permits connection of one or more devices to the LAN.

(c) The servers shall be Water Corporation SCADA standard servers/computers, running the Water

Corporation SCADA Standard Operating Environment. For complex or critical sites/schemes,

separate server hardware and operator workstations are to be installed at the local operating

location. Combined server and workstation installations are permissible for small sites that

require local servers.

(d) A local primary server is required for every site where local servers have been determined as

required. Refer to section 2.6.2.1 for further details on local server criteria.

(e) A local standby server is generally only required for critical sites/schemes which are primarily

operated on site or remote operation location that is not OC (i.e. regional depot) by workstations

on the LAN. It shall be configured as a hot standby that will take over automatically in the

event that the primary server fails.

(f) All plants shall be connected to the Water Corporation's SCADA WAN, allowing real-time

plant data to be collected and stored by the Corporation’s PI Data Historian. The connection

shall be via the SCADA server/s.

(g) All treatment plants will be connected to the Utility Wide SCADA System (UWSS).

Connections will differ for complex and simple treatment plants. Simple plants with local server

(LARS) installations will also have their SCADA database hosted on the UWSS; with the local

server featuring a replicated site database from UWSS – both the UWSS and the local server

are both DNP3 masters to the site RTU. Complex plants with localised servers (LASS) will

also have remotely hosted permanent standby servers accessible via the SCADA WAN; the

localised servers operate as stand-alone servers that communicate with the PCS via OPC

protocols. Additionally, complex plants may also have critical alarming integrated as part of

the UWSS via the site RTU.

(h) In general, plants shall feature a Remote Terminal Unit (RTU) with a primary function of

being a DNP3 gateway device between the PCS and the UWSS. An RTU may be a separate

device or integrated as part of a PLC. On simple plants, the RTU also may carry out logic

functions and operate as part of the PCS.



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(i) PCS control functions shall be carried out by PLCs that are connected to field I/O.

Implementation of control functions on site RTUs shall generally be avoided except for simple

plants with a limited number of controllers or where standard designs for particular assets

nominate the use of an RTU.

(j) Plant safeguarding functions shall be carried out by the PLCs or independently of the PLCs

(eg. hardwired interlocks or within separate OEM package controllers such as the chlorine gas

emergency shutdown systems commonly used by Water Corporation). The selection of the

control function location shall be as appropriate to the causes of the risk that the safeguarding

function aims to reduce.

(k) Self-contained vendor packages shall communicate with PCS PLCs either via the LAN or

through dedicated PLC networks using industrial communication protocols such as Modbus

(TCP/RS485), Profinet or Profibus (DP/PA).

(l) Local Operator Interface Panels (OIPs) shall be interfaced directly to PCS LAN or vendor-

provided PLCs and shall provide a local operator interface to specific processes or equipment

items.

(m) Ancillary systems tend to be specific to each plant but may typically include such things as

power system monitoring and protection, on-site generation controls, safety systems and the

like. IP telephony, closed-circuit TV, fire detection and access control security systems shall

not be connected to the PCS LAN but shall be provided with separate communication paths

which shall not connect to SCADA WAN.

(n) Workstations shall be desktop PCs running the Water Corporation SCADA Standard Operating

Environment (SOE).

(o) Printers may feature as part of a treatment plant for the purpose of printing reports, trends and

SCADA screenshots.

(p) Routers and modems facilitate secure network access to the PCS by operators and other

authorised personnel via the Water Corporation SCADA WAN.

Treatment plant sites are further classified as follows with respect to SCADA and Corporate WAN

connections to site:

(a) SCADA Site: A Water Corporation operational site that primarily has a SCADA presence, with

operators or SCADA equipment (e.g. RTU, SCADA servers and workstations). Users requiring

access to the OT network primarily to access the SCADA system will need to access corporate

applications via desktop virtualisation software. Generally, there are no corporate devices or

users (with some existing sites having printing and a phone service, which should remain). An

example of a SCADA Site is a simple treatment plant.

(b) Shared Site: A Water Corporation operational site that has both a corporate and SCADA

presence. These sites have both OT and Corporate networks but will be separated (mostly

logical) with users operating both corporate or SCADA workstations to perform functions

respectively. No direct access between each network, even though it is locally present.

Corporate user is defined as a full-time permanent staff member working business hours

undertaking non-operational activities. An example of a Shared Site is a complex treatment

plant.



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2.2.2 Plant Control System

Treatment plants are usually divided into a number of separate physical and/or operational

areas/processes, reflecting the plant’s layout and the stages of the treatment provided by the plant. The

division into areas/processes facilitates design, documentation, operation and maintenance of the plant.

The Plant Control System (PCS) design shall ensure alignment with this characteristic division. Control

of each treatment process area shall be autonomous and independent of other treatment process areas

except where it is necessary to coordinate particular functions between areas.

For the purposes of this standard, Process Area Control System (PACS) shall mean the PLC(s) and

associated ancillary equipment which form an autonomous controlling system for the particular

treatment process area. The scope of PACS includes all instruments and controlling equipment specific

to that particular treatment process area.

Each PACS shall consist of one or more interconnected PLCs installed in Process Area Control Cubicle

(PACC) conforming to Type Specification DS26-26. Ideally, each PACC shall be installed in a secure

indoor area adjacent to the equipment that it controls. Where this is not possible, the PACC shall be

specified to be suitable for the installation environment including consideration of IP rating, hazardous

areas, environmental conditions (e.g. temperature) and weather protection. Allocation of control

functions to PACCs shall reflect the treatment process and the physical plant layout.

As far as possible, all control and monitoring of a particular process or equipment item (excluding self-

contained vendor packages) shall be carried out by one PLC. The Designer shall avoid splitting control

of a process or equipment item between PLCs as this tends to increase the complexity and reduce the

reliability of the control system. Maintaining control of a process or equipment within a single PLC

(with remote I/O for a distributed plant) avoids control dependencies resulting from communication

links. For simple plants, it is anticipated that control of multiple process areas are consolidated within

a single PLC. Where standard designs are used (e.g. Chlorination), inclusion of IO and logic outside of

the standard design to have a single PLC shall be confirmed with Water Corporation SCADA Design

Engineer.

If it is necessary to provide interlocks to or from other PLCs – for example where there are dependent

processes in other areas – the interlocks shall use direct PLC-to-PLC communications over the PCS

LAN unless there is a safety issue involved (where the required operation time is less than the time

associated with detection of communications failure), in which case the interlocks shall be hard-wired.

To ensure the functional independence of each PACS, process interlocking and other PLC-to-PLC

communications shall not depend on the SCADA system.

Interlocks between PLCs shall be continuously supervised. In the event of communications failure, the

PLCs shall attempt to re-establish communications; such attempts shall not interfere with other system

communications. If communications cannot be re-established within a reasonable time, an alarm shall

be raised and the local process or equipment item shall default to a safe mode of operation or, if this

cannot be ensured, shall shut down safely.

Where there are multiple identical process units (e.g. multiple filters, screens, sedimentation tanks and

the like) the Designer shall distribute control of the identical units evenly over two or more I/O racks so

that failure of any one I/O rack will not result in the loss of all process units. This approach should

similarly be applied to duty/standby equipment wherever practical (refer section 2.5.1.2.3) in order to

maximise the plant availability.

Where the units have unusually complex control requirements or are particularly critical to plant

operation, each unit shall be controlled by its own dedicated PLC.



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Availability shall also be a key consideration for critical treatment plants ensuring that the failure of one

PLC will still allow the plant to run at a reduced capacity. The availability figure needs to be determined

based on how long the treatment plant can be shut down for, and the control system needs to be designed

to meet this figure.

The inputs and outputs belonging to each identical process unit shall be allocated to separate I/O racks

or modules where they reside on a single PLC system; except where I/O allocation is nominated as part

of standard designs.

As far as the nature of the process permits, the design of the PCS shall ensure that:

(a) Each PLC will continue to monitor and control the equipment and processes allocated to it

notwithstanding failure of other PLCs, communications or the SCADA system; and

(b) Failure of a single PLC will not necessarily lead to plant shutdown, acknowledging that plant

operation may be limited.

The design of the PCS shall also allow for integration of:

(a) PLCs provided as part of vendor equipment packages;

(b) Local control panels and displays provided as part of an equipment package (for example the

proprietary control panel for a chemical batching plant);

(c) Control stations and display units necessary to facilitate operation, for example to allow testing,

start-up or maintenance of a particular piece of equipment;

(d) Monitoring and alarm inputs from OEM Critical Safeguarding controllers as well as remote

manual initiation of any safety shutdown functions.

As far as possible the interface between the PCS and such equipment shall be by means of an approved

industrial communication link in preference to hard wiring. Refer to section 2.4.2 for further details

regarding PCS communication with process equipment.

2.2.2.1 SCADA System

For complex plants the supervisory control hardware, including local primary server, workstations and

printers, shall be housed in a secure control room in the plant’s administration or operations building.

For simple plants (featuring supervisory control hardware) it is acceptable to locate the equipment in a

plant office or amenities building providing that the area in which it is located is clean, adequately

secured and fit for purpose.

For increased security the local standby server (if applicable) is recommended to be installed in a

separate building or a fire-separated area of the same building.

For complex plants, facilities shall be provided to connect a laptop at each PACC via a spare port on a

network switch.

In complex plants there may be a requirement for local control rooms with permanent workstations in

key process areas. The need for, and location of, local control rooms shall be determined in consultation

with the OT Design Advisor, Engineering Design Manager, process designers and plant operators.

Issues to be considered include:

(a) Physical size and complexity of the plant;

(b) Operational efficiency – the ability to monitor particular processes with minimal distraction and

without interfering with operations in other areas;

(c) Operational convenience – the ability to monitor and make adjustments to processes and

equipment from nearby, without having to go to the main control room;



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(d) Security and redundancy – in the event of failure of either the main control room or local control

room equipment, supervisory control is still available from the other control room.

All local control rooms housing supervisory control hardware, whether central or local, shall be air-

conditioned (with sufficient air flow to cool housed equipment to within the optimum operating

temperature and humidity control to maintain 40% - 60% rH. ), provided with dust filters and, where

necessary to ensure a non-corrosive environment, provided with activated carbon filters and ED

flooring. Raised flooring with distributed cooling is to be considered where the Designer is unable to

achieve sufficient air flow to cool server racks to optimum operating temperatures. The location of the

workstation area shall comply with DS20. Alarming shall be included should the cooling system fail

(e.g. analog temperature with temperate high alarm). The Designer shall confirm the operating

temperature for the equipment (e.g. air conditioner settings) and alarming for the local control rooms.

2.3 Control Philosophy

This section shall be read in conjunction with DS40-01 Control Philosophy Section 2.

2.3.1 Control Mode Selection

In general, each process and equipment item shall be capable of being controlled automatically (AUTO

control mode) and manually (MANUAL control mode).

Refer to DS40-01 Control Philosophy Section 2 for required modes of operation and how these operating

modes are selected (i.e. physical switched, HMI buttons etc.).

2.3.2 Control Location Selection

In some cases, it may also be necessary to be able to control an item locally, i.e. adjacent to the item

itself. This is typically the case with motorised valves, penstocks and particular drives. In such cases a

LOCAL/REMOTE selector shall be provided in the field, on or adjacent to the item itself; in the absence

of a selector being provided as part of the equipment (e.g. valve/penstock actuator).

2.3.3 Control Hierarchy

Emergency stops and primary protection devices shall take precedence over all other controls and shall

not be capable of being overridden.

Control location selection shall override control mode selection from the SCADA system.

The control hierarchy is illustrated diagrammatically in Figure 2-1.



Page 18 of 45


Figure 2-1: PCS control hierarchy

2.3.4 Equipment Status, Faults and Alarms

The state/status of each process or equipment item shall be continuously monitored and reported to the

PCS regardless of which control mode is selected. Information to be reported shall include

“AVAILABLE”, “RUNNING”, the current control mode selection (AUTO/ MANUAL), the current

control location selection (LOCAL/ REMOTE – typically limited to drives) and, where applicable,

information such as position, level, speed, stage in a process sequence and the like.

All faults occurring in any process or equipment item shall be automatically reported to the PCS

regardless of which control mode is selected. Each fault condition for which a separate sensor or

protective device is provided shall be reported separately so that the cause of the problem can be readily

identified remotely; grouping of multiple faults under general descriptions such as “fault” shall be

avoided except for an overall equipment summary fault. Guidance for condition fault for different types

of equipment can be found in G 40-01 ClearSCADA Database – How to Manual.

Fault conditions shall generate alarms with severity as described in DS40-05 Scheme Control – Section

2. 2. 5.

The PCS shall allow alarms to be acknowledged from the HMI but it shall not be possible to reset a PCS

alarm unless the cause has been removed and where applicable the alarm reset in the field.

2.4 Communications

2.4.1 General

2.4.1.1 SCADA Communications

SCADA communications comprise those links between the treatment plant site and the UWSS or

remotely hosted servers. These are to be IP links enabling site connection to the SCADA WAN. Backup

(secondary) communication links may be required dependent on the criticality of the treatment plant

(refer Critical Assets section of DS40).

Implementation on site will involve a suitable modem for the connection technology and a router in the

case where backup (secondary) communication links are nominated. The modem and/or router will

connect directly to the PCS LAN facilitating connection to the site RTU and local servers (if applicable).

SCADA System

Command

Control Mode Selection

(from SCADA system)

Control Location Selection (in field,

where provided)

Process or

Equipment Item Auto

Manual

Remote

Local

Emergency Stop

Pushbutton

Run (from configured

program)

Manual Start

(from operator

workstation)

Manual Start

(from field)

Item starts or runs

Setpoint (from

configured program)

Manual Start

(from operator

workstation)

Manual Start

(from field)

Item setpoint



Page 19 of 45


2.4.1.2 Peer to Peer Communications

Peer to peer communications comprises those links where the PCS has a requirement to communicate

with a related asset control system for the purpose of control and interlocking (e.g. bore sites supplying

a treatment plant, or tank site supplied by the treatment plant). Ideally, these shall comprise IP links

with similar options as is available for SCADA communication links with the addition of connections

by optic fibre or copper cabling. IP links for peer to peer communications shall preference

communication links that are not provided by a third party service provider.

2.4.1.3 Local Area Networking

The PCS LAN links all components of the SCADA system and PCS down to the PCS PLC level. The

LAN is based on Ethernet communications and employs network switches as part of the implementation.

All PCS PLCs shall feature an Ethernet communications interface.

The LAN shall be designed such that the maximum volume of traffic expected under worst-case

conditions shall equate to 60% of the designed load to allow for anticipated future expansion.

Momentary overloads, due for example to the occurrence of large numbers of simultaneous alarms and

events, shall not result in system shutdown or malfunction. It shall be possible to extend the LAN and

to connect and configure additional equipment with the PCS on-line and without interrupting system

operation.

The LAN backbone shall consist of one or more optic fibre cables where it traverses between plant

locations. The optic fibre cable shall be specified and installed in accordance with the requirements of

DS43-06. Critical plants shall feature a LAN arrangement comprised of a self-healing ring so a cable

break at any one point will not result in isolation of any nodes and an alarm is raised to notify Operators

of the break in the ring. Network switch units in a self-healing ring shall be of the managed variety

(supporting SNMP monitoring) and shall provide two Ethernet LAN backbone connections and at least

four twisted-pair and/or fibre optic ports to suit the connected network elements.

Monitoring and alarming of devices that facilitate LAN connections shall be included on local and

remote SCADA systems. These devices shall be displayed on a separate network communication

overview. The overview arrangement shall ensure operators and maintenance can easily identify failures

which impact redundancy and availability of each process area.

Cabling within buildings may be twisted pair cable, providing the total route distance does not exceed

80m. Twisted-pair cable used in LAN applications shall be, at a minimum, Category 6 shielded twisted

pair (UTP) cable to IEC 11801 e.g. SYSTIMAX. Sheath colour shall be grey. To avoid confusion with

cables of intrinsically-safe circuits, blue-sheathed UTP cable shall not be used.

For complex plants where there is a high volume of traffic on the LAN, it may be necessary to provide

separate PCS and SCADA LANs in order to keep transmission delays to an acceptable level.

For increased security in critical plants, physically-separated dual redundant LANs may be nominated,

with automatic transfer from the failed LAN to the healthy LAN. This also requires duplication of

network switches, PC and PLC interface cards and other equipment. An alarm shall also be raised to

notify operators of the failed primary LAN. This alarming to operators shall apply for any redundant

path or redundant equipment failure

In special circumstances the use of radio links or of a complete wireless LAN may be considered. Where

the Designer believes that the use of wireless technology is appropriate, the matter shall be referred to

the Principal SCADA Engineer.



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2.4.1.4 I/O Networking and Fieldbuses

I/O communications comprises links between PLCs and remote I/O systems. The communication links

may be implemented by various industrial protocols including fieldbuses.

The Water Corporation currently supports the use of Modbus RTU, Modbus TCP, Profinet and Profibus

protocols. Preference is to have Ethernet based fieldbus communications where practical.

Refer to DS43-04 Profinet and Profibus Network Design and Installation.

2.4.2 PCS Communications with Process Equipment

The types of process equipment likely to be encountered in treatment plants which require an interface

to the PCS include:

(a) IED units (e.g. VSDs, Soft starters etc.)

(b) PLCs included in vendor equipment packages

(c) Proprietary controllers (including those within Critical Safeguarding equipment)

(d) HMI

Wherever possible, interfaces between PCS PLCs and process equipment shall utilise a widely-

supported open fieldbus communications interface rather than hard-wired I/O. Hard-wired interfaces

shall be avoided due to their greater complexity, higher cost of installation and maintenance and poorer

reliability due to the larger number of connections. Preference is to have Ethernet based fieldbus

communications where practical.

The software in the PCS shall monitor all process equipment communications links. If a

communications failure is detected, then alarms shall be generated at the SCADA system. The relevant

PACSs shall automatically cause the equipment to revert to a safe mode of operation or, if this cannot

be ensured, shall shut it down safely.

Where possible, process equipment shall incorporate facilities to detect loss of communication with the

PCS and shall be configured to revert to a safe state automatically if communications fails.

Note that the PCS PLCs with which the process equipment communicates will need to be fitted with the

appropriate communications interface modules.

2.4.3 Communications with Field Instruments and Control Devices

The most suitable type of communications to be used between field instruments and control devices will

depend on the type and complexity of the instrument or device.

For on-off devices such as limit, proximity, level, temperature and flow switches, solenoid valves and

the like, hard-wired I/O is generally the most appropriate choice.

For basic analogue instruments such as flowmeters and pressure, differential pressure, level, temperature

and analyser transmitters a widely-supported open standard fieldbus connection shall be used if readily

available as specified in DS40-09 Field Instrumentation. Preference is to use the same fieldbus

throughout the plant. Use of conventional 4-20 mA hard-wired I/O shall be confirmed with Water

Corporation SCADA Design Engineer.

The type of fieldbus shall be selected from those supported by the Water Corporation SCADA Design

Standards. Fieldbus systems that are not covered by Water Corporation SCADA Design Standards shall

only be used with the approval of the Principal SCADA Engineer.

Note that the controllers or PLCs to which the devices are connected will need to be fitted with the

appropriate communications interface modules.



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2.5 Plant Control

2.5.1 General

2.5.1.1 Remote Terminal Units

2.5.1.1.1 Type

RTUs shall be selected from the Operational Technology Approved Equipment List.

2.5.1.1.2 Hardware

RTUs shall support expansion modules where additional I/O is required. All modules shall incorporate

operational status indicators.

RTUs may also take the form of a communications module residing within a PLC.

2.5.1.1.3 Inputs and Outputs

Refer to Section 2.5.1.2.3. RTU I/O requirements shall align with those required for PLCs.

2.5.1.2 Programmable Logic Controllers

2.5.1.2.1 Type

PLCs shall be selected from the Operational Technology Approved Equipment List.

2.5.1.2.2 Hardware

PLCs shall be of modular rack-mount construction. Module addresses shall be software selectable so

that it is possible to insert any module in any slot. Ideally, with power applied, it shall be possible to

insert or remove any PLC module without damage to the module.

All modules shall incorporate operational status indicators.

Scan time (the time required to read all inputs, solve all networks and update all outputs) shall not be

more than 50ms and ideally should be less than 20ms. The Designer shall limit the I/O count and amount

of program code per PLC if necessary to achieve this. Counter input modules shall be used for high-

speed counting applications.

Power supply to PLCs and I/O shall be backed up by UPS (AC or DC as relevant to the power supply

interface on the equipment and the use of DC power supply units) and shall be sized to provide at least

25% spare capacity. UPS backup time shall suit the application but in no case shall be less than 0.5

hours at maximum PLC load. In critical applications, duplicate decoupled DC power supply units with

no-break changeover shall be provided and shall be arranged so that either supply can fail and be

replaced on line without affecting PLC operation.

PLC unit spare capacity, including power supply for the spare items, shall provide for 20% for each IO

type and 20% rack capacity for IO modules and including 20% spare space in cubicles to allow for IO

interfacing and line protection.

2.5.1.2.3 Inputs and Outputs

Inputs shall be fuse-protected in groups corresponding to discrete processes or equipment items so that

a fault on any input group will not cause loss of inputs belonging to other processes or equipment items.

Digital outputs shall be voltage-free relay contacts, preferably with no common connections. Care shall

be taken to ensure that the load on each output is consistent with the PLC contact rating and will not

limit contact life unduly. Solid-state outputs shall be provided where high switching rates are involved.

All digital I/O modules shall incorporate status (on/off) indicators for each input and output.



Page 22 of 45


Analogue inputs shall generally be 4-20mA (supporting HART where nominated), but other types of

analogue inputs (e.g. thermocouple, RTD) shall be provided where appropriate.

Resolution of analogue inputs and outputs shall be equivalent to 12-bit with a linearity of ±1 bit and a

repeatability of ± ½ bit. Any analogue input that falls outside the range of the analogue-to-digital

converter shall initiate an alarm.

Calibration of analogue I/O modules shall be carried out in software without the need for any physical

adjustments on the I/O module, so that module replacement shall not require physical re-calibration.

Inputs and outputs shall be allocated so that failure of any I/O module will affect the minimum number

of processes or equipment items. I/Os for duty and standby equipment shall be allocated to different

modules.

Allocation and numbering of I/O points shall follow a logical and consistent pattern. Where there are

several identical processes or equipment items, I/O allocation shall be consistent for each process or

equipment item across multiple PLCs.

2.5.1.2.4 Field Connections

Facilities for connecting field cables to PLC I/O shall meet the following requirements:

(a) They shall enable individual field cable cores to be connected to adjacent terminals sequentially

in core order;

(b) They shall facilitate neat, orderly wiring with ready access to all terminations;

(c) They shall enable field wiring to be easily connected, disconnected and tested without disturbing

adjacent wiring or risking damage to PLC I/O modules or other hardware.

The use of marshalling terminals assists in meeting the above requirements and is preferred. However

subject to the above requirements being met, field cables may be terminated direct to PLC I/O if the I/O

units are of a sufficiently robust design and are specifically intended for this purpose

For PACC with large amounts of hard-wired I/O, it is convenient to provide two sets of marshalling

terminal rails; a PLC rail with terminals connected sequentially to the PLC I/O module terminals and a

field rail to which each field cable is connected sequentially in core order. This arrangement is often

advantageous for fast-track projects because it allows PLC I/O wiring and field cables to be terminated

before PLC I/Os are allocated. Once PLC I/Os have been allocated, the two rails – which shall be

mounted adjacent and parallel to each other – are linked by jumper wires. The Designer shall employ

this method where appropriate.

For smaller PACC a single terminal rail may be provided. In this case the rail terminals shall be arranged

to allow field cables to be connected sequentially in core order, with jumper wires from the rail to the

PLC I/O terminals.

2.5.1.2.5 Diagnostics

PLCs shall include visual alarms to indicate system malfunctions such as watchdog timer fault, faulty

or missing I/O modules, power supply failure or low battery volts.

The CPU shall incorporate self-test diagnostics which shall run at switch-on and periodically during

normal operation. It shall also be possible to initiate a self-test manually. The self-test diagnostic checks

shall typically include:

(a) Power supplies;

(b) Corruption of ROM/RAM contents;

(c) RAM read/write ability;



Page 23 of 45


(d) Correct operation of CPU;

(e) I/O module communications and integrity of interconnections including backplane;

(f) I/O complement (missing/faulty modules).

No false actions, outputs or alarms shall occur as a result of running diagnostic checks.

In addition, the PLC shall continue to report any overrides (“forces”) that have been set until the

overrides are reset.

2.5.1.2.6 Location and Installation

PLC equipment shall be installed in PACCs conforming to DS26-26. PACCs shall be separate from

switchgear or power electronic equipment.

2.5.1.2.7 LAN Communications

All PLCs shall be supplied with standard communications interfaces (e.g. Ethernet, Profibus) to suit the

PCS LAN and field communication requirements of the plant.

It shall be possible to back up to or download, on demand, the programs and configuration of any PLC

connected to the PCS LAN. All the PLCs shall be configurable online via the PCS LAN using an MDT

SOE with PLC software and configurations obtained from MDT Autosave.

2.5.1.2.8 PLCs Supplied with Vendor Equipment

Although PLCs supplied as part of vendor equipment should be selected from the Operational

Technology Approved Equipment List, in practice this is not always achievable. For example, the

vendor may have standardised on a different type of PLC. Substitution of the plant standard PLC would

require the Vendor to rewrite and re-test existing proven software. This should be investigated as a

preferred option. However, substitution may not be feasible. In such cases the Vendor’s PLC may be

accepted by the Principal SCADA Engineer providing it is of acceptable quality, has an adequate

supportability plan, and can communicate with the PCS PLCs via a data link using the same

communication protocol used for wider PCS LAN where possible. The supportability plan, which may

consist of a full spare PLC or service level agreement with the vendor for breakdowns, shall be

confirmed by the Designer and provided to the Principal SCADA Engineer as part of the request to use

the vendor PLC. The vendor shall be made responsible for configuring, commissioning and proving the

link and also for ensuring adequate support mechanisms are available.

The vendor equipment supplier shall provide Water Corporation a means by which configuration and

application software is made available to store in Water Corporation’s MDT Autosave such that in the

event of the non-availability of software replacement from the supplier, configuration and application

software is immediately available from the MDT Autosave. Annotations in the software shall be in

English.

2.5.2 Selection

PLC and RTU make and models shall comply with the Operational Technology Approved Equipment

List. Where multiple options exist, consideration shall be given to:

• Existing plant installation

• Regional preference, training and familiarity



Page 24 of 45


2.6 Monitoring and Control

2.6.1 General

2.6.1.1 Utility Wide SCADA System (SCADA)

The SCADA system shall be based on a software package conforming to the Corporation’s current

standards. The Corporation will arrange corporate licences for its preferred SCADA software. Such

software shall be treated as ‘Principal-Supplied’.

2.6.1.2 Local Area Replication Server

Where the site meets the criteria for LARS described in Section 2.6.2.1 LARS vs LASS, the LARS shall

be stored in the control room. LARS database shall be a replication of the UWSS database.

Typical LARS architecture and data paths can be seen in Appendix B.

2.6.1.3 Local Area Standalone Server

Where the site meets the criteria for LASS described in Section 2.6.2.1 LARS vs LASS, the LASS shall

be stored in the control room. LASS database shall be developed using UWSS templates and mimics.

The specifications of the server would depend on the site and shall be determined by the Water

Corporations Infrastructure Architects. LASS servers will be Principally supplied and configured.

Typical LASS architecture and data paths can be seen in Appendix B.

2.6.1.4 Site Operator Interface Panel and Local Display Panels

OIPs may be provided based on the requirements of the site. There are many factors to consider in

making this decision including: remoteness of the site, communications reliability and site criticality.

Local graphic display and control panels shall be selected from the Operational Technology Approved

Equipment List.

Display and control panels installed in outdoor locations shall be weatherproof and protected against

deterioration due to high temperatures and ultraviolet radiation. Displayed text and graphics shall be

clearly readable in direct sunlight.

Panel size shall be chosen so that the displayed text and graphics are large enough to be clearly readable

from normal viewing distances. Buttons and page layout shall be designed for users with a 20mm wide

index finger.

Display and control panels shall communicate directly with a PLC via an industry-standard

communications link or indirectly via the PCS LAN.

Where OIPs are nominated, their primary use shall be for consolidated instrumentation and equipment

status monitoring independent of the SCADA System. Control via OIPs shall be limited to emergency

control functionality only. Where SCADA System independent local control is required, local server

arrangements are preferred to an OIP.

2.6.2 Selection

2.6.2.1 LARS vs LASS

LARS or LASS is required when:

1. Reliable continuous plant visibility and operation at site is required during communications

outages

2. Reliable continuous plant visibility and operation is required during disaster events when there

is a prolonged outage to central operations SCADA, (multiple causes – loss of communications,



Page 25 of 45


loss of central severs, loss of IT network (routers, switches, etc. Weather events), in the event

of a cyber attack

3. Quality of communications: latency/ response time is greater than 1. 8 second

4. Quality of communications: available (guaranteed) bandwidth is less than 2 Mbyte/second

Refer to Table 2-1 for LARS vs LASS guidance selection criteria once one or more of above

requirements have been established unless selected option compromises the reliability (i.e.

communications issues). In general, the preferred option will be the one that meets the most criteria in

Table 2-1. Selection of LARS or LASS shall be confirmed with Water Corporation SCADA Design

Engineer and captured in LARS Assessment Table (Nexus 59086142).

Table 2-1: LARS vs LASS Guidance Selection Criteria

Criteria LARS LASS

No. of Local Servers

≤ 1

There will be

degradation in

redundancy moving a

site with dual on-site

servers to a LARS

system and should be

noted for any design

changes.

≥ 2

Total No. of Workstations (including

Corporate Workstations) ≤ 3 ≥ 4

Total No. of SCADA Client Workstations

High number (>3) and high ratio of SCADA

clients/workstations is indicative of the

number of different operator areas within the

asset.

≤ 2 ≥ 3

No. of PLCs

Multiple PLCs is indicative of the complexity

of the asset and number of processes.

Multiple PLCs or processes such as dosing

require visibility of fast data changes that

cannot be supplied at present by the UWSS.

Fast data response required for process/PID

trending is 2sec between updates.

≤ 3 ≥ 4

Server Point Count ≤ 5000 > 5000

Site Architecture

Offsite communications

to OC, Single local

server, operator HMI via

server.

Single operations room,

one SCADA client

Single operations room,

more than one SCADA

client, several operator

workstations, dual local

servers.

Multiple control rooms,

multiple ViewX clients,

distributed process

areas, dual local

servers, site wide

control LAN

Site is an isolated site

Not required to operate within a scheme i.e. it

is an isolated plant other than the product

output

No Yes




Page 26 of 45


Criteria LARS LASS

Site is primarily controlled by Operations

Centre (OC) Yes No

Site has at least one Critical Control Point

(CCP)

Refer to the Water Safety Plan for water

treatment sites or the Process Control Table

for wastewater sites.

No Yes

Business Criticality Classification/Score

(see Nexus 49003342 ) ≤ 2 ≥ 3

Communication to the site

Communication issues are noted for

consideration and mitigation for any agreed

design changes to the architecture. Criteria

may influence architecture decision if it

cannot be mitigated.

There are no known

communication issues.

There are known

communication issues

that cannot be resolved

and the site is locally

controlled.

2.6.2.2 OIPs

Refer to DS40 Design Process for SCADA Works for selection of OIPs.

2.7 Process Instrumentation

Refer to DS40-09 Field Instrumentation.

2.8 Sub-Systems

The sub-systems likely to be encountered in treatment plants can be classified into two general types as

follows.

2.8.1 Vendor Equipment Packages

The term “Vendor Equipment Package” covers equipment that, while it may be of more or less standard

design, is manufactured or assembled to order. The Designer, as specifier, will generally have at least

some control over the type of equipment and control interface provided. Examples include filters,

chemical batching and dosing plants, aeration blowers, gas flares and the like.

Control panels for vendor equipment packages shall comply with DS26-26 where appropriate. Any

RTUs included in the package shall be of a type as specified in the SCADA Approved Equipment List.

Any deviation from this must be approved by the Principal SCADA Engineer. Refer to Section 2.5.1.2.8

for PLCs to be supplied with Vendor Equipment. More complex equipment packages shall be provided

with graphic operator interface panels which shall communicate by data link with the package PLC.

Simple packages may use panel-mounted switches, pushbuttons, indicators, alphanumeric displays and

the like.

Equipment packages shall include a LOCAL/OFF/REMOTE control location selector and shall be

specified with a control interface that will allow the PCS to control them as a unit. The interface shall

typically operate as follows:

(a) The interface shall signal to the PCS that it is available for operation when:

• Power is applied to the package,

• There are no active alarms

• All its subsystems and equipment items are ready

• Its control mode is not set to OFF




Page 27 of 45


(b) If the package’s control mode is set to OFF it shall not be possible to start it under either auto

or manual control. If it is already running it shall shut down. Selection of the OFF mode shall

immediately signal to the PCS that the package is not available.

(c) If the package’s control mode is set to LOCAL it shall be under the exclusive control of its local

control panel or control stations. PCS commands shall have no effect.

(d) If the package’s control mode is set to REMOTE it shall transmit a signal to the PCS to indicate

this. Providing the package is available for operation the PCS shall then be able to initiate or

terminate its operation by issuing or withdrawing a start command.

(e) On receipt of the PCS start command the package’s local controller shall manage all start-up

sequencing and protection functions for the drives and other equipment that make up the

package.

(f) As soon as the package has successfully completed its start-up sequence and is running normally

it shall transmit a RUNNING signal to the PCS.

(g) The package shall continuously monitor itself, whether running or not, and shall transmit

information to the PCS indicating the status of its components. The package controller shall

automatically and independently take appropriate action in the event of a fault and shall transmit

detailed alarm and diagnostic information to the PCS.

(h) Local alarm and status indication shall be provided for each drive or equipment item and for the

package as a whole. Local indication shall typically include status for each drive or equipment

item and alarm indication for each fault condition.

The Contractor undertaking the PCS works shall use an approved Water Corporation SCADA template.

This shall be developed by the Contractor undertaking the PCS works if there is no existing suitable

template. This shall be submitted to Water Corporation CCB for approval.

2.8.2 Small Vendor Equipment Control Cubicles

Vendor equipment packages are supplied with proprietary control systems that must be housed in

suitable enclosures appropriate to the environment where they are to be deployed. Such small control

cubicles:

(a) Shall comply with the requirements of “Type Specification for Low Voltage Switchboards

General Requirements DS26-09” where appropriate.

(b) Shall have a degree of protection rating of not less than IP56 where installed outdoors.

(c) Shall have a degree of protection rating of not less than IP53 where installed indoors.

(d) Equipment located within the cubicle that requires operator access shall have an IP2X rating.

For indoor cubicles this is typically achieved via mounting the equipment on the door. For

outdoor cubicles this is typically achieved via mounting the equipment on an escutcheon plate

within the cubicle.

(e) Shall have all equipment housed behind hinged lockable doors and, where installed outdoors,

with no equipment placed on the external doors of the cubicles. It is permissible to have

equipment mounted on the external door of indoor cubicles provided the degree of protection

rating is suitable for the environment and the operation and maintenance activities performed in

the area and, in any case, is not less than (c) above. All indoor cubicles shall have an electrical

isolator on the front of the door.

(f) Shall be suitably labelled as to describe the function.



Page 28 of 45


2.8.3 Ancillary Systems

2.8.3.1 Security Access Control Systems

Security Access Control Systems typically provide hardwired outputs for the following signals to the

PCS:

• Security armed/disarmed

• Security breached/not breached

• Security system healthy/fault

The security functional scope for the site will nominate the specific signals required.

2.8.3.2 CCTV

CCTV shall operate on a separate network to the PCS LANs. Exceptions will be where CCTV is used

to control or manage a process. The designer shall include this detail when submitting the LTM/PTM

request. See DS 40 Design Process for SCADA Works for details of the LTM/PTM request process.

2.9 Access and Privileges

To maintain security, the PCS shall provide several password-protected levels of access appropriate to

the needs and authority of different users. Refer to DS41-03 ClearSCADA Configuration Section 4. 3.

2.10 Power Supply

2.10.1 General

The power requirement for the site is based on the available power supplies and the site criticality.

If the site is designated as critical then battery backup power will be required and the design shall be

based on DS42-04 Communications Power Supply.

Battery backed power supply may comprise either of AC UPS systems or DC UPS / Battery Charger

Systems.

2.10.1.1 AC UPS Systems

AC UPS systems are typically applied at sites with air-conditioned environments such as switchrooms

and control rooms due to the heat generated by the equipment and associated installed temperature

rating.

AC UPS systems are either floor or rack mounted and may be specified with internal or external

batteries.

Refer to DS 26-30 or DS 26-31 for AC UPS type specifications.

2.10.1.2 DC UPS / Battery Charger Systems

DC UPS systems are also referred to as battery charger systems. They may be specified with or without

integral AC/DC conversion. Generic batteries may be connected however some vendors offer additional

monitoring capability when batteries are matched to DC UPS systems. DC UPS systems must be of the

"no-break" type where there is no delay in switchover.

DC UPS systems and batteries shall be selected from the Operational Technology Approved Equipment

List.



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2.10.2 Selection

The Designer shall aim for all instrument and control systems to be powered by Extra Low Voltage

(ELV) 24VDC supplies. In some cases this is not possible due to the power draw requirement of

particular instrumentation/actuators. Typically, automatic process analysers and valve actuators may

require 240VAC supplies.

Where critical power supply necessitating a UPS is required, the selection of DC UPS over an AC UPS

system is dependent on whether there are 240VAC elements requiring critical power supply.



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3 INSTALLATION SPECIFICATION

3.1 General

3.1.1 Network Cabling

Optic fibre cables shall be installed in accordance with the requirements of DS43-06.

Permanently-installed Shielded Twisted Pair (STP) cable (i.e. excluding patch leads) shall be installed

in conduit. STP cable shall be separated from other cables by at least 0. 5m where possible. STP cable

shall not be installed out-of-doors or underground except for runs of up to 20m between adjacent

buildings, where it may be installed underground in conduit. Cabling requirements for Ethernet based

communications are covered in section 3.1.2.

Where a ring topology is utilised, a separation of at least 2m within buildings and 6 m elsewhere shall

be maintained between any two cables in the ring configuration.

Where dual redundant LANs are provided, a separation of at least 2m within buildings and 6 m

elsewhere shall be maintained between the two LANs where possible.

3.1.2 Communications Cabling

Serial RS485 communications over route lengths exceeding 150m and Ethernet communications over

route lengths exceeding 80 m shall utilise optic fibre cables where possible.

Ethernet communications not exceeding 80m route length and contained within the one building, or

serial RS485 communications up to 150m route length whether indoor or outdoor, may use either optic

fibre or suitable screened twisted-pair cable. However, in order to reduce susceptibility to surges, optic

fibre cables shall be used for all outdoor data communications where practical.

Where metallic cable runs out-of-doors, whether underground or not, it shall be fitted with surge

suppressors at both ends in accordance with DS40-09. Separation distances between data, control and

power cables shall be in accordance with DS40-09. Cable screens shall connect to a solid ground

(normally, the metal frame of the cubicle/switchboard) with a low impedance at one end and a series

RC network at the other. This arrangement is to prevent the flow of DC ground-loop currents in the

shield.

3.1.3 Field Instrument Cabling

Individual and overall instrument cable screens shall be earthed to an instrument earth bar at the PLC

end only, unless otherwise recommended by the instrument manufacturer.

Where fieldbus communications is used and the total route length exceeds 150 metres or there is a risk

of lightning strike, electrical interference or significant earth potential rise the links shall utilise optic

fibre cable. In other cases, suitable screened twisted pair cable, fitted with surge suppressors at both

ends in accordance with DS40-09, may be used as an alternative.

Redundant or multiple paths shall be provided for multi-drop fieldbus connections to limit the extent of

control loss should one path fail. Where there are duty/standby or multiple units, a separate path shall

be provided for each. The use of a single cable to connect all items creates a serious process control

risk and shall be avoided.

It shall be possible to disconnect and reconnect individual equipment items on multi-drop fieldbus cables

without disrupting communications to other equipment on the same path.

Separation distances between data, control and power cables shall be in accordance with DS40-09.

Screens shall be earthed at the controller or PLC rack end and insulated from earth at the field end.



Page 31 of 45


For further details of instrument connection requirements refer to DS40-09.

3.1.4 Instrument Installation

In addition to the requirements of DS40-09, instruments shall be installed so that they are readily

accessible from ground, floor or walkway level for inspection, adjustment, removal and maintenance.

Special attention shall be given to ensuring that displays are easily readable.

Instruments shall be provided with lightning surge protection as required by DS40-09.

Connections for compressed air and potable water shall be provided adjacent to instruments where

required for maintenance and cleaning. Special consideration shall be given to instruments such as

dissolved oxygen and ORP probes installed through covers on aeration tanks, channels and the like. The

installation shall provide an effective odour seal while allowing the probe to be withdrawn for

inspection, cleaning, maintenance or calibration. There shall also be a temporary means of sealing the

cover penetration when the probe is withdrawn.

3.1.5 Instrument Junction Boxes

Where hard-wiring is used for field instruments, where practical, junction boxes shall be used to marshal

cables from individual instruments and control devices and to connect them to PLC I/O using multi-pair

or multicore cable. Junction boxes shall utilise rail-mounted terminal strips with at least 20% spare

terminals.

Instrument and control junction boxes shall contain ELV wiring only.

3.1.6 Switchrooms and Control Rooms

As a minimum, treatment plant sites shall feature a desk area designated for the installation of a desktop

workstation in either a switchroom or control room environment. The location of the workstation area

shall comply with DS20. Where the SCADA system hardware involves rack mounted servers and

network equipment, consideration shall be given to the installation of a suitable equipment rack in a

switchroom or control room environment at the treatment plant to house this equipment.



Page 32 of 45


4 APPROVED EQUIPMENT LIST

Refer to the Operational Technology Approved Equipment List.



Page 33 of 45


5 HAZARDOUS AREAS

5.1.1 General

A hazardous area is defined as an area in which an explosive atmosphere is present, or may be expected

to be present, in quantities such as to require special precautions for the construction, installation and

use of potential ignition sources. The explosive atmosphere may be caused by the presence of a

flammable liquid, gas or vapour or by the presence of combustible dust in suspension or in layers or a

combination of explosive gas and dust atmospheres.

Water treatment plants do not usually use or produce flammable gases or combustible dusts in sufficient

quantities to constitute an explosion risk. Water treatment examples of flammable gases or combustible

dusts are ammonia gas for chloramination; hydrogen gas as by-product of electrochlorination; and

powdered activated carbon. However, wastewater treatment plants frequently produce significant

quantities of flammable gas either deliberately or unintentionally as a by-product of the treatment

process. Therefore, explosion risks must be considered by the Designer.

The flammables gases produced in wastewater treatment consist mainly of methane and tend to be

concentrated in particular process areas including anaerobic digesters, digester-gas handling plant,

digester-gas fired boilers and generators. However, flammable gases may also accumulate in poorly-

ventilated areas containing sewage or sludge, such as enclosed air spaces above sewers, inlet channels,

screens, primary sedimentation tanks, digested and dewatered sludge storages.

Combustible dusts are generally not a problem in treatment plants, although any dry powder material

produced or used in the plant, such as dried sludge or polyelectrolyte powder, shall be assessed for

flammability and appropriate measures taken.

The Designer shall ensure that area classification, plant design and equipment selection are carried out

in accordance with the requirements of the HA Hazardous Area Classification Standard and the HA-ST-

03: EEHA Selection and Installation Standard.

5.1.2 Competency Requirements The classification of hazardous areas, the selection of electrical equipment to be used in hazardous areas

and the design of electrical installations within hazardous areas shall only be undertaken by those

persons who satisfy the requirements of HA-ST-04: EEHA Competency Standard.

5.1.3 Area Classification

Hazardous Area classification is the first step in designing the electrical installation for hazardous areas

in treatment plants. Hazardous Area classification shall be carried out in accordance with HA-ST-02:

HA Hazardous Area Classification Standard.

5.1.4 Equipment Selection

5.1.4.1 Use of Certified Equipment

All instrumentation used in hazardous areas of treatment plants shall have appropriate certification in

accordance with the requirements of HA-ST-03: EEHA Selection and Installation Standard.

5.1.4.2 Explosion-Protection Techniques

Explosion-protection techniques listed within HA-ST-03: EEHA Selection and Installation Standard are

preferred and shall be adopted in the first instance.

Other techniques maybe considered but their use is subject to approval from the Principal SCADA

Engineer and the EEHA Technical Integrity Custodian (TIC).



Page 34 of 45


5.1.4.3 Corrosive Environments

Where equipment is located in corrosive environments (e.g. hydrogen sulphide, H2S), to prevent

premature equipment failure the designer shall ensure materials for the selected equipment are suitable

for the location or that enclosures with adequate sealing to house equipment is provided.

5.1.5 Installation

Instrumentation installation design in hazardous areas shall conform to the following

(a) AS/NZS 3000:2018, “Wiring Rules”

(b) AS/NZS 60079. 14 Explosive atmospheres Part 14: Electrical installations design, selection and

erection

(c) AS/NZS 60079. 17 Explosive atmospheres Part 17: Electrical installations design, selection and

erection

(d) HA-ST-03: EEHA Selection and Installation Standard.

5.1.6 Documentation

The Designer shall prepare and maintain a hazardous area Verification Dossier in accordance with the

HA-ST-10: EEHA Verification Dossier Standard.

The Verification Dossier shall be kept up to date at all times during the design process.

Following construction and commissioning the Verification Dossier will be used by the Corporation,

maintenance contractors and future designers for maintenance purposes and for the recording of test

results, inspections, equipment overhauls, repairs and modifications and changes to area classifications.

The dossier shall therefore be prepared and maintained by the Designer with the needs of operators,

maintenance staff and future designers in mind.

The Verification Dossier shall be available for inspection by the Principal SCADA Engineer at all times

during the design phase.

5.1.7 Testing and Inspection

All new intrinsically safe circuits shall be tested to prove that there are no unintentional earths prior to

connecting the circuits to the barriers. All new intrinsically safe earth installations shall be tested prior

to commissioning to ensure that their resistance is acceptable, and that they are only connected to earth

at the specified locations.

Prior to energisation, instrumentation installed in hazardous area shall undergo initial inspection at a

detailed grade to ensure that they are correctly installed (AS/NZS 600079. 14 cl. 4.1 and AS/NZS 60079.

17 clause 4.3.1).

The following standards are applicable

(e) HA-ST-05: EEHA Inspection Standard

(f) HA-ST-06: EEHA Testing Standard



Page 35 of 45


6 WORK ON EXISTING TREATMENT PLANTS

6.1.1 General

The design of additions and upgrades to existing treatment plants shall follow the same general

principles as for new plants. However, the Designer needs to be aware of a number of issues that are

likely to arise when working on existing plants.

6.1.1.1 Site Survey

Before commencing work on additions to or upgrades of an existing treatment plant the Designer shall:

(a) Obtain copies of all available drawings and documentation for the plant from the OT Design

Advisor;

(b) Carry out a site survey of the areas affected by the new works in order to confirm the

completeness and accuracy of existing documentation and to determine the condition of the

existing installation.

Any issues arising from the site survey which may affect the scope or design of the new works shall be

reported to the OT Design Advisor.

It is strongly recommended that the Designer meets with plant operations and maintenance personnel

on a regular basis during the design phase to brief them on the proposed works and to provide an

opportunity for discussion and feedback. Such meetings shall be coordinated through the OT Design

Advisor and any proposed or requested design changes arising from them shall be referred to the OT

Design Advisor for approval.

6.1.1.2 Standards and Regulations

All new work shall conform to current Corporation, Australian and international standards and to current

statutory regulations.

Some of the standards and regulations to which existing plants, particularly older plants, have been

designed may have been superseded. In many cases this may be of little consequence. However, the

Designer will sometimes encounter compatibility or safety issues when interfacing with equipment or

facilities built to superseded standards. This is particularly so when designing additions and upgrades

to older plants that have been subject to several previous upgrades. In such cases the Designer shall

identify the issues and propose solutions for consideration by the Principal SCADA Engineer.

6.1.1.3 Safety and Environmental Issues

The conformance of existing facilities affected by the new works to current statutory requirements shall

be checked. The Designer shall refer any non-conformances, particularly those which relate to safety

or the environment, to the Principal SCADA Engineer with recommendations for resolving them. This

can be done by submitting a Request For Information/Decision that outlines the problem then describes

the potential solution and alternatives with a recommendation based on consideration of balance of

advantages and disadvantages such as practicality, reliability, cost and time impacts.

If the Designer becomes aware of any safety or environmental issues relating to existing plant or

equipment, even though the plant or equipment may not be directly affected by the new works, the issues

shall be referred in writing to the Principal SCADA Engineer.

Such issues may include:

(a) Plant or equipment that does not meet current safety or environmental regulations;

(b) Plant or equipment in poor or unsafe condition.



Page 36 of 45


Where hazardous materials are encountered, the matter shall be brought to the attention of the

Engineering Design Manager and Project Manager.

6.1.1.4 Numbering

Numbering of equipment and instruments for the new works shall be in accordance with this standard

and the equipment numbering convention described in Process Engineering design standard, DS81.

Before allocating any new numbers, the Designer shall check if any blocks of numbers have been

reserved in the existing scheme for future additions. If any such blocks exist they shall be allocated

first. For instance if the plant includes three equipment items of a particular type and a fourth item is to

be installed, numbering for the new item may already have been allocated by a previous designer.

Where numbering has not already been allocated, numbering of new equipment and instruments shall

continue existing sequences. For example if the last number used in an existing area is 1534, the new

equipment numbering could start from 1540. It is recommended that a gap be left between the old and

new numbers.

Equipment numbering in some older plants may have been carried out to older standards not compatible

with the current practice specified in DS81. These conflicts will generally be resolved as part of the

process design (which includes production and/or revision of P&IDs) rather than as part of the SCADA

design, and will resolved in accordance with the guidance provided in DS81’s section regarding

“Conflict with existing sheet numbering”.

6.1.2 Plant Control Systems

All new processes and equipment items shall be integrated into the existing SCADA system, including

all necessary updating of displays, graphics, reports, alarms, data logging, trending, programming and

documentation. For LASS sites, as a minimum equipment and instrumentation required for scheme

operation (i.e. final plant storage level, final pump station and plant outflow), critical alarms and

instrumentation and associated setpoints critical control points shall also be integrated on UWSS.

Where any work is carried out on the existing SCADA system it shall be upgraded in accordance to the

latest standard templates.

6.1.3 Programmable Controllers

Existing controller hardware affected by the new works may need to be upgraded or replaced if it is

obsolete or does not conform to current Water Corporation standards.

The upgrade and selection of controller hardware shall be clarified with Water Corporation SCADA

Design Engineer

6.1.4 Data communications

Existing copper or radio communication networks may need to be upgraded to optic fibre or IP radio as

part of the new works.

The upgrade of data communications shall be clarified with Water Corporation SCADA Design Engineer

6.1.5 Field Instrumentation

Existing field instruments may need to be upgraded or replaced to bring them into conformity with

current Water Corporation standards.

The upgrade or replacement of existing instrumentation shall be clarified with Water Corporation

SCADA Design Engineer



Page 37 of 45


6.1.6 Hazardous Areas

The Designer shall carry out a full review of existing hazardous area classifications for those areas

affected by the new works. Existing areas shall be reclassified where necessary when the hazardous

areas created by the new works overlap existing plant, or the new works are within an area that is already

classified as a hazardous area.

Re-classification shall be undertaken in accordance with HA-ST-02: HA Classification Standard with

the existing site hazardous classification report updated.

When the new works affects the hazardous area classification of existing process areas, the Designer

shall review existing electrical equipment in those areas to ensure they are suitable for the new

classification.

If the Designer becomes aware of any hazardous area non-conformance issues relating to existing plant

or equipment not affected by the new works, the issues shall be referred in writing to the Principal

SCADA Engineer.

The existing Hazardous Area Verification Dossier shall be kept up to date at all times by the addition of

new material from the new works as components and systems are designed, installed and commissioned

and brought online.



Page 38 of 45


Appendix A Typical Control System Block Diagrams

A1.1 Complex Treatment Plant

RTU

NBN

MODEM

ROUTER

CELLULAR

MODEM

FIREWALL

TO UWSS

PLC

R EMOT E I/O

R AC K

PRINTER [1]

CORPORATE

NETWORK

CONNECTION

ALTERNATIVE

CONNECTIONS

FIELD I/O

MAIN CONTROL

ROOM

FIELD I/O VSD

UNITS

MCC

PRIMARY

SERVER [1]

ETHERNET

SWITCH

ETHERNET

SWITCH

WORK

STATION [1]

WORK

STATION [1]

WORK

STATION [1]

STANDBY

SERVER

ETHERNET

SWITCH

FIELD

HMI

PLANT AREA

CONTROL SYSTEM 3

ETHERNET

SWITCH

PLC

R EMOT E I/ O

R AC K

PLANT AREA

CONTROL SYSTEM 1

FIELD I/O

INSTRUMENTS

ACTUATORS

TYPICAL FIELD IO

VSD

UNITS

MCC

FIE

LD

BU

S

ETHERNET

SWITCH

PLC

PLANT AREA

CONTROL SYSTEM 2

FIELD I/O

VSD

UNITS

MCC

VENDOR PACKAGE

FIELD

HMIPLC

VENDOR PACKAGE

FIELD

HMIPLC

ETHERNET

SWITCH

INTERCONNECTION TO ANCILLARY

SYSTEMS (ELECTRICAL PROTECTION,

POWER GENERATION, SECURITY ETC.)

IF APPLICABLE

1. PART OF SCADA SYSTEM

2. TYPICAL FIELD IO – SHOWS SOME OF THE FEATURES WHICH

MIGHT BE FOUND IN A MINOR TREATMENT PLANT PCS

NOTES:

PORTABLE

WORKSTATION

Figure 6-1: Typical Control System Block Diagram for a Complex Treatment Plant



Page 39 of 45


BLANK PAGE



Page 40 of 45


A1.2 Simple Treatment Plant

RTU

NBN

MODEM

ROUTER

CELLULAR

MODEM

FIREWALL

TO UWSS

ETHERNET

SWITCH

PLC

REMOTE

I/O RACK

PRINTERSCADA SERVER

AND

WORKSTATION

CORPORATE

NETWORK

CONNECTION

ALTERNATIVE

CONNECTIONS

FIELD I/O

SCADA SYSTEM

(CONTROL ROOM)

AUTOMATIC

CONTROL SYSTEM

FIELD I/O

INSTRUMENTS

ACTUATORS

TYPICAL FIELD IO

VSD

UNITS

MCC

INTERCONNECTION TO

ANCILLARY SYSTEMS

(SECURITY ETC.) IF

APPLICABLE

1. TYPICAL FIELD IO – SHOWS SOME OF THE FEATURES WHICH

MIGHT BE FOUND IN A MINOR TREATMENT PLANT PCS

NOTES:

FIE

LD

BU

S

Figure 6-2: Typical Control System Block Diagram for a Simple Treatment Plant



Page 41 of 45


BLANK PAGE

Standard Design DS 45-06



Page 42 of 45


Appendix B LARS & LASS

B1.1 LASS Typical Architecture

Figure 6-3: Local Area Site Server (LASS) Typical Architecture




Page 43 of 45


B1.2 LARS Typical Architecture

Figure 6-4: Local Area Replication Server (LARS) Typical Architecture




Page 44 of 45


B1.3 Data Transmission Paths

LASS

JTWC SCADA Network

Permanent StandbyUWSS

Site Server (S)

JWTC / OpsClients

Local Client(s)

RTU

PLC

Router

UWSS

RemoteCommunications

LARS

JTWC SCADA Network

Permanent StandbyUWSS

Site Server (S)

JWTC / OpsClients

Local Client(s)

RTU

PLC

Router

UWSS

RemoteCommunications

Communications Path Key

Green = UWSS data

Purple = Site Server data

Orange = JTWC Client

Red = Local Client

Brown = PLC to RTU

Blue = Synchronise data to permanent standby

The only differences are:

Where the Site Server gets its data from (Purple)

Synchronising data across the Telecoms (Blue)




Page 45 of 45


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