Contents A. 220/132 KV & 400 KV SUB-STATION

1. Definition

2. Introduction

B. About the substation

B.1 Construction –Site Selection & Layout

C. Equipment in a 220KV & 4 0 0 K V Substation

1) Bus- bar 2) Insulators

a) Pin type insulators

b) Suspension type insulators

c) Strain type insulators

3) Isolating Switches 4) Circuit breaker

a) SF6 Circuit breaker

b) Air Circuit breaker

c) Oil Circuit breaker

5) Protective relay

6) Instrument Transformer

i. Current Transformer

ii. Voltage Transformer

7) Metering and Indicating Instrument

8) Miscellaneous equipment

9) Power Transformer

a) autotransformer

10) Lightening arrestors

11) Line isolator

12) Conductors

I. Bundled conductors

II. Ground wires

13) Wave trap

14)Communication in power system

A) Telecommunication

I. Microwave Communication System

II. Fibre Optic Communication System

III. Power Line Carrier Communication System

B) SCADA system

A.1) Definition of sub -station : -

“The assembly of apparatus used to change some

characteristics (e.g. Voltage ac t o d c freq. p.f.

etc) of electric supply is called sub-station”.

A .2 ) Introduction : -

The present day electrical power system is a.c. i.e.

electric

power is generated, transmitted and distributed in

the form of Alternating current. The electric power is

produce at the power station, which are located at

favorable places, generally quite away from the

consumers. It is delivered to the consumer through a

large network of transmission and distribution. At

many place in the line of power system, it may be

desirable and necessary to change some characteristic

(e.g. Voltage, ac to dc, frequency p.f. etc.) of electric

supply. This is accomplished by suitable apparatus

called sub-station for example, generation voltage

(11KVor 6.6 KV) at the power station is stepped up

to high voltage (Say220KVto 132 KV) for

transmission of electric power. Similarly near the

consumer’s localities, the voltage may have to be

stepped down to utilization level. This job is again

accomplished by suitable apparatus called sub-

station.

B) About the substat ion : -

Panki Thermal Power Station is located at Panki in Kanpur district

in the Indian state of Uttar pradesh , about 16 km from Kanpur . It

has an installed capicity of 220 Mega Watts.

The Central government has commissioned a 210 MW unit at Panki

Power Station.

At PTPS, 2x110 MW BHEL made coal fired turbo generating units

are presently in operation. These 110 MW machines were

manufactured, supplied and commissioned by M/s BHEL, during

1976-77 with features of reheating and regenerative feed heating.

The Steam Generator is balanced draft, radiant, dry bottom, single

drum, natural circulation, vertical water tube type construction with

skin casing and semi direct type of firing system. Apart from the

above 110 MW units, 2x32 MW Russia made turbo generating units

were also installed at PTPS in 1967-68, however these units have

become obsolete and permanently closed now after running for

about 30 years.

The most important of any substation is the grounding

(Earthing System) of the instruments, transformers etc.

used in

the substation for the safety of the operation personnel as

well as

for proper system operation and performance of the protective

devices.

An earthes system comprising of an earthing mat buried at a

suitable depth below ground and supplemented with ground

rods

at suitable points is provided in the substations. These

ground the

extra high voltage to the ground. As it is dangerous to us

to go

near the instrument without proper earth. If the

instruments are not ground properly they may give a huge

shock to anyone who would stay near it and also it is

dangerous for the costly

instrument as they may get damaged by this high voltage.

B.1) Site Select ion & Layout 220KV & 400 KV

Substat ion : -

220KV Sub -Station forms an important link

between

Transmission network and Distribution network. It

has a vital influence of reliability of service. Apart

from ensuring efficient transmission and

Distribution of power, the sub-station configuration

should be such that it enables easy maintenance of

equipment and minimum interruptions in power

supply. Sub-Station is constructed as near as possible

to the load center. The voltage level of power

transmission is decided on the quantum of power to

be transmitted to the load center.

Selection of site :- Main points to be considered while selecting the site for

Grid

Su b-Station are as follows:

i) The site chosen should be as near to the load center as

possible.

ii) It should be easily approachable by road or rail for

transportation of equipments.

iii) Land should be fairly leveled to minimize development

cost.

iv) Source of water should be as near to the site as possible.

This is

because water is required for various construction activities

(especially civil works), earthing and for drinking purposes

etc.

v) T h e s u b -station site should be as near to the town / city

but

should be clear of public places, aerodromes, and Military /

police

installations.

vi) The land should be have sufficient ground area to

accommodate

substation equipments, buildings, staff quarters, space for

storage

of material, such as store yards and store sheds etc. with

roads

and space for future expansion.

vii) Set back distances from various roads such as National

Highways, State Highways should be observed as per the

regulations in force.

Viii While selecting the land for the Substation preference

to be

given to the Govt. land over private land.

ix) The land should not have water logging problem.

x) Far away from obstructions, to permit easy and safe

approach

/ termination of high voltage overhead transmission lines.

B . 2 ) Equipment in 220KV&400KV Sub - Station : -

The equipment required for a transformer Sub-

Station depends upon the type of Sub-Station,

Service requirement and the degree of protection

desired.

220KV EHV Sub-Station has the following major

equipments.

1 ) Bus - bar :-When a no. of lines operating at the same voltage have to

be directly connected electrically, bus-bar are used, it is made

up of

copper or aluminum bars (generally of rectangular X-Section)

and

operate at constant voltage.

The bus is a line in which the incoming feeders come into

and get into the instruments for furtherstep up or step

down. The first bus is used for putting the incoming feeders

inLAsingleline.There may be double line in the bus so that if

any fault occurs in the one the other can still havethe

current and the supply will not stop. The two lines in the

bus are separated by a little distanceby a Conductor having a

connector between them. This is so that one can work at a

time and theother works only if the first is having any fault.

Bus bars :-

b

2 ) I n s u l a t o r s : -The insulator serves two purpose. They support the

conductor (or bus bar) and confine the current to the

conductor.

The most commonly used material for the manufactures of

insulators is porcelain. There are several type of insulator

(i.e. pine type, suspension type etc.) and there used in Su b-

Station will depend upon the service requirement.

Ceramic insulators

Glass insulators

a) PIN INSULATOR:-

Offering an extensive range of 11KV, 22KV and 33 KV pin insulators that

are fabricated from high grade raw material as per the demand of various

electrical industries. Pin insulators it is supported on a pin and provide a

means to hold the insulator to the pin and provide a means to secure the

conductor to the insulator. We offer these pin insulators at varied

standard and customized specifications at cost efficient rates.

11 KV PIN INSULATORSOur range of 11KV pin insulators encompasses RR / PN / 1105, RR /

PN / 1103, RR / PN / 1104 and RR / PN / 1102 which are available in

different technical specifications. These highly efficient pin

insulators are less vulnerable to damage and can normally

withstand the line voltage for a considerable time with ease.

RR / PN / 1105 RR / PN / 1103

RR / PN / 1104 RR / PN / 1102

VOLTAGE CLASS 22 KV

AND 33 KVPin insulators in voltage class 22KV and 33KV have found application in

varied industries and are widely used in low cost distribution lines. Our

pin insulator is designed to secure the conductor to itself. Top quality pin

insulator includes RR / PN / 2201, RR / PN / 3301, RR / 004 / 22 PIN and

RR / 003 / 33 PIN.

RR / PN / 2201 RR / PN / 3301

RR / 004 / 22 PIN RR / 003 / 33 PIN

b) SUSPENSION INSULATORS:-

Suspension insulators are made of multiple units, with the number

of unit insulator disks increasing at higher voltages. The number of

disks is chosen based on line voltage, lightning withstand

requirement, altitude, and environmental factors such as fog,

pollution, or salt spray. Longer insulators, with longer creepage

distance for leakage current, are required in these cases.

Suspension type insulators:-

C) STRAIN INSULATORS :-A strain insulator is an insulator that provides both large electrical

insulation and a large load-bearing capacity. A typical strain

insulator is a piece of glass or porcelain that is shaped to

accommodate two cables or a cable shoe and the supporting

hardware on the support structure (hook eye, or eyelet on a steel

pole/tower). The shape of the insulator maximizes the distance

between the cables while also maximizing the load-bearing transfer

capacity of the insulator. When the line voltage requires more

insulation than a single insulator can supply, strain insulators are

used in series: A set of insulators are connected to each other using

special hardware. The series can support the same strain as a single

insulator, but the series provides a much higher effective insulation.

Strain type insulators:-

3) I s o l a t i n g S w i t c h e s : -

I n Sub -Station, it is often desired to disconnect a part of the

system for general maintenance and repairs. This is

accomplished by an isolating switchor isolator. An isolator is

essentially a kniff Switch and is design to often open a circuit

under no load, in other words, isolator Switches are operate

only when the line is which they are connected carry no load.

For example, consider that the isolator are connected on both

side of a cut breaker, if the isolators are to be opened, the C.B.

must be opened first .

3 pole switch :-

4 ) C i r c u i t b r e a k e r : -A circuit breaker is an equipment, which can open or close a

circuit under normal as well as fault condition. These circuit

breaker breaks for a fault which can damage other instrument

in the station.It is so designed that it can be operated

manually (or by remote control) under normal conditions and

automatically under fault condition.There are mainly two

types of circuit breakers used for any substations. They are

(a) SF6 circuit breakers;

(b) air circuit breakers;

(c) oil circuit breakers.

For the latter operation a relay wt. is used with a C.B.

generally bulk oil C.B. are used for voltage upto 66 KV while

for high voltage low oil & SF6 C.B. are used. For still higher

voltage, air blast vacuum or

SF6 cut breaker are used.

(a) SF6 CIRCUIT BREAKER :-

The use of SF6 circuit breaker is mainly in the substations

which are having high input kv input, say above 220kv and

more. The gas is put inside the circuit breaker by force i.e.

under high pressure.

When if the gas gets decreases there is a motor connected to

the

circuit breaker. The motor starts operating if the gas went

lower than 20.8 bar. There is a meter connected to the

breaker so that it can be manually seen if the gas goes low.

The circuit breaker uses the SF6 gas to reduce the torque

produce in it due to any fault in the line. The circuit

breaker has a direct link with the instruments in the

station, when any fault occur alarm bell rings.

SF6 ckt breaker diagram :-

(b) AIR CIRCUIT BREAKER :-

These type of breakers employ ‘air blast’ as the quenching

medium.The contacts are opened by air blast produced by the

opening of blast valve.The air blast cools the arc and sweeps away

the arcing products to the atmosphere.This rapidly increases the

dielectric strength of the medium between contacts and prevents

from re-establishing the arc.Consequently the arc is extinguished

and the flow of current is interrupted.

(c ) OIL CIRCUIT BREAKER  :-

A high-voltage AC electrical switch whose main contacts are located

in a space filled with mineral (transformer) oil. Upon interruption of

the electric circuit, an electric arc forms between the contacts of

the circuit breaker. Because of the high temperature of the arc the

oil is evaporated rapidly and oil vapors are partially decomposed,

liberating ethylene, methane, and other gases. A gas bubble is

formed in the arcing zone; the pressure in the bubble may be as

high as several dozen mega newtons per sq m. The arc is then

extinguished, both because of its elongation upon parting of

contacts and because of intensive cooling by the gases and oil

vapor.

Low oil ckt breaker diagram :-

5) P r o t e c t i v e r e l a y :-A protect ive relay is a device that detects the fault and

initiates the operation of the C.B. to isolate the defective

element from the rest of the system”. The relay detects the

abnormal condition in the electrical circuit by constantly

measuring the electrical quantities, which are different under

normal and fault condition. The electrical quantities which

may change under fault condition are voltage, current,

frequency and phase angle. Having detect the fault, the relay

operate to close the trip circuit of C.B.

Relay diagram :-

6 ) Instrument Trasformer : -

The line in Sub-Station operate at high voltage and

carry current of thousands of amperes. The measuring

instrument and protective devices are designed for low

voltage (generally 110V) and current (about 5A).

Therefore, they will not work satisfactory if mounted

directly on the power lines. This difficulty is overcome

by installing Instrument transformer, on the power

lines. There are two types o f instrument

transformer.

i ) Current Transformer : -

A current transformer is essentially a step-down

transformer which steps-down the current in a

known ratio, the primary of this transformer consist

of one or more turn of thick wire connected in series

with the line, the secondary consist of thick wire

connected in series with line having large number of

turn of fine wire and provides for measuring

instrument, and relay a current which is a constant

faction of the current in the l ine .

Current transformers are basically used to take the

readings of the currents entering the substation.

This transformer steps down the current from 800

amps to1amp. This is done because we have no

instrument for measuring of such a large current.

The main use of his transformer is

(a) distance protection;

(b) backup protection;

(c) measurement.

Current transformer(CT) diagram :-

i i ) V o l t a g e T r a n s f o r m e r : -It is essentially a step– down transformer and step down the

voltage in known ratio. The primary of these transformer

consist of a large number of turn of finewire connected

across the line. The secondary way consist of a few turns and

provides for measuring instruments and relay a voltage

which is known fraction of the line voltage.

Potential transformer(PT) diagram :-

7 ) Metering and Indicating Instrument

:-There are several metering and indicating Instrument (e.g.

Ammeters, Volt- meters, energy meter etc.) installed in a

Substation to maintain which over the circuit quantities. The

instrument transformer are invariably used with them for

satisfactory operation .

8) Miscellaneous equipme nt :-In addition to above, there may be following equipment in a

Substation :

i )Fuses

i i)Carrier -current equipment

i i i )Sub-Station auxiliary supplies

9) Power Transformer : - There are three transformers in the incoming feeders so

that the three lines are step down at the same time. In case

of a 220KV or more KV line station auto transformers are

used. While in case of lower KV line such as less than 132KV

line double winding transformers are used.

a) Autotransformer :

Transformer is static equipment which converts electrical

energy from one voltage to another. As the system voltage

goes up, the techniques to be used for the Design,

Construction, Installation, Operation and Maintenance also

become more and more critical. If propercare is exercised in

the installation, maintenance and condition monitoring of

the transformer, it can give the user trouble free service

throughout the expected life of equipment which of the order

of 25-35 years. Hence, it is very essential that the personnel

associated with the installation, operation or maintenance

of the transformer is through with the instructions

provided by the manufacture.

Autotransformer taping :-

10) Lightening arrestors :-Lightening arrestors with earth switch lightening arrestors

after the current transformer are used so as to protect it

from lightening i.e. from high voltage entering into it. This

lightening arrestor has an earth switch, which can directly

earth the lightening. The arrestor works at 30° to 45° angel

of

the lightening making a cone. The earth switch can be

operated manually, by pulling the switch towards ground.

This also helps in breaking the line entering the station. By

doing so maintenance and repair of any instrument can b

performed.

Different types of lighning arrestors :-

It is a device used on electrical power systems to protect the

insulation on the system from the damaging effet of

lightning. Metal oxide varistors (MOVs) have been used for

power system protection since the mid 1970s. The typical

lightning arrester also known as surge arrester has a high

voltage terminal and a ground terminal. When a lightning

surge or switching surge travels down the power system to

the arrester to the ground.

11) Line isolator :-

The line isolators are used to isolate the high voltage

Flow throughthe line into the bus. This isolator prevents

the instruments to get damaged. It also allows the only

needed voltage andrest is earthed by itself. In electrical

engineering, a disconnector or isolator switch is used to make sure

that an electrical circuit can be completely de-energised for service

or maintenance. Such switches are often found in electrical

distribution and industrial applications where machinery must have

its source of driving power removed for adjustment or repair. High-

voltage isolation switches are used in electrical substations to allow

isolation of apparatus such as circuit breakers and transformers,

and transmission lines, for maintenance.

12) Conductors:-

Aluminium conductors reinforced with steel (known as ACSR) are

primarily used for medium and high voltage lines and may also be

used for overhead services to individual customers. Aluminium

conductors are used as it has the advantage of lower

resistivity/weight than copper, as well as being cheaper.

While larger conductors may lose less energy due to lower electrical

resistance, they are more costly than smaller conductors. An

optimization rule called Kelvin's Law states that the optimum size of

conductor for a line is found when the cost of the energy wasted in

the conductor is equal to the annual interest paid on that portion of

the line construction cost due to the size of the conductors. The

optimization problem is made more complex due to additional

factors such as varying annual load, varying cost of installation, and

by the fact that only definite discrete sizes of cable are commonly

made.

I. Bundle conductors :-

Bundle conductors are used to reduce corona losses and audible

noise. Bundle conductors consist of several conductor cables

connected by non-conducting spacers. For 220 kV lines, two-

conductor bundles are usually used, for 380 kV lines usually three

or even four.

Bundle conductors are used to increase the amount of current that

may be carried in a line. Due to the skin effect, ampacity of

conductors is not proportional to cross section, for the larger sizes.

Therefore, bundle conductors may carry more current for a given

weight.

A bundle conductor results in lower reactance, compared to a single

conductor. It reduces corona discharge loss at extra high voltage

(EHV) and interference with communication systems. It also

reduces voltage gradient in that range of voltage.

Double conductors four

conductors

II. Ground wires :-

Overhead power lines are often equipped with a ground conductor

(shield wire or overhead earth wire). A ground conductor is a

conductor that is usually grounded (earthed) at the top of the

supporting structure to minimise the likelihood of direct lightning

strikes to the phase conductors. Shield wires on transmission lines

may include optical fibers (OPGW), used for communication and

control of the power system.

13) wave trap :-It is also called "Wave trap". It is connected in series with the power

(transmission) line.It blocks the high frequency carrier waves

(24 KHz to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass

through. It is basically an inductor of rating in Milli henry (approx 1 

milli Henry for 220  KV 1250 Amp.).

Wave trap diagram:-

14) Communication in Power System

Following are mainly three inter-related areas of functions in

UPPTCL for management of power system:

A) Telecommunication

B) SCADA- Supervisory Control and Data Acquisition System.

A) TELECOMMUNICATION

There are three different types of telecommunication systems in

UPPTCL i.e.

i. Microwave Communication System,

ii. Fibre-optic Communication System,

iii. PLCC-Power Line Carrier Communication.

Voice Frequency (VF) channels of all these systems have been

integrated/interconnected to make a hybrid communication system.

Microwave & Fibre Optic are multi-channels communication

systems and are also called 'Wideband communication system'.

PLCC is single channel communication system. A brief overview of

these three types of telecommunication system of UPPTCL is as

below:

I. Microwave Communication System

Microwaves travel in 'Space' and any object in the path can obstruct

communication system. Microwave is called 'line-of-sight'

communication system. As such, its antennas are mounted on high

towers so that even trees should not obstruct path of microwaves.

UPPTCL is using frequency band between 2.3 GHz to 2.5 GHz. The

height for antenna are calculated by taking into account many

factors, such as, distance between two locations, path clearance,

height from sea level of these locations, tropical area, reflection

points, and so on. As such, height of towers varies from location to

location. Tower heights at our microwave stations range from 30 to

110 meters. Starting from Muzaffarnagar (220KV substation Nara),

in the north-west, to Rihand (Pipri), in south-east of UP, 33

microwave stations have been established. A list of microwave

stations with height of towers has been given at the end of this

write-up. This covers a route length of over 1000 Km.

II. Fibre Optic Communication System

It is new communication system and has been introduced in

UPPTCL since 2001. Optical fibre cable, in the form of 'Optical Fibre

Composite Ground Wire' (OPGW), has been installed on

transmission towers by replacement of earth wire. Earth wires of

following five transmission lines, total route length of 408 Km., have

been replaced:

'Optical Line Terminal Equipment' (OLTE) have been manufactured

by Fujitsu, Japan and have been installed at eight sub-stations

(Muradnagar, Moradabad, C.B.Ganj, Unnao, Panki, Sahupuri,

Sarnath & Azamgarh). The electrical signal of 2Mb/s or 34Mb/s, as

the case may be, from OLTE is connected with Primary Multiplexing

equipment supplied by 'Nokia' Finland. Its NMS provides

operational support for the 'Fibre Optic Transmission System'

(FOTS). For testing, commissioning & maintenance 'FLEXR' and

'FLEXR Plus' computer software programmes have been provided.

'FLEXR' is used for initial settings of OLTEs of fibre optic network.

Similar to microwave NMS, 'FLEXR Plus' helps in remote diagnosis,

operation and maintenance of fibre optic network. For complete

communication control system, a NMS100 system has installed at

NRLDC, New Delhi, which is in position to diagnose faults of whole

northern region.

OPGW has been manufactured by Farukawa, Japan. They have done

replacement work, on live (hot) lines, by using a unique installation

technology. The OPGW in our system has got twelve (12) 'Dual

Window Single Mode' (DWSM) type fibres in it. Optical signals of

1310 or 1550 nanometer (nm) wavelength are being used. Only two

fibres are required for a multi-channel link between two stations.

One fibre is used for transmitting optical signal and second for

receiving from other end. In our system two fibres have been used

for 'Normal' communication path and two fibres for 'protection'

path. Fibre optic communication system has got a wide bandwidth

transmission capability. Two fibres are sufficient for providing more

than one lakh telephone channels on both sides. As such, a high-

speed data, containing large volumes of information can be

transmitted at low cost.

III. Power Line Carrier Communication

System

Power Line Carrier Communication (PLCC) is a single channel

communication system in which its channel (300 to 3400 Hz) is

divided into two parts i.e. speech band is generally kept 300 to

2400Hz or 300 to 2000Hz and rest is used as data band. Due to

narrow speech band in PLCC, voice of poor quality is available in

comparison to wideband communication system. In this system,

signal travels on the transmission line from one end to other end.

Transmitter output (Radio Frequency signal) is fed to the

transmission line through a Coupling Capacitor or CVT. RF power

output is in frequency band from 70 KHz to 500 KHz. Inductors,

called 'Wave Traps' are used at the ends of the signals. PLCC is also

used for line protection signal. Protection signals are transmitted

through PLCC system for tripping circuit breaker of other end of

transmission line. UPPTCL has a wide network of PLCC links.

Presently, its number of PLCC links are about 550.

Plc block diagram:-

B) SCADA SYSTEM

In SCADA system measured values, i.e. analogue (measured value)

data (MW, MVAR, V, Hz Transformer tap position), and Open/Closed

status information, i.e. digital data (Circuit Breakers/Isolators

position i.e. on/off status), are transmitted through

telecommunication channels to respective sub-LDCs. For this

purpose Remote Terminal Units (RTUs) at 400KV, 220KV  and few

important 132KV sub-stations have been installed. System values &

status information below 132 KV have not been picked up for data

transmission, except for 33KV Bus isolator position and LV side of

generators. Secondary side of Current Transformers (CT) and

Potential Transformer (PT) are connected with 'Transducers'. The

output of transducers is available in dc current form (in the range

of 4mA to 20mA). Analogue to digital converter converts this

current into binary pulses. Different inputs are interleaved in a

sequential form and are fed into the CPU of the RTU. The output of

RTU, containing information in the form of digital pulses, is sent to

subLDC  through communication links. Depending upon the type of

communication link, the output of RTU is connected, directly or

through Modem, with the communication equipment. At subLDC

end, data received from RTU is fed into the data servers. In general,

a SCADA system consists of a database, displays and supporting

programmes. In UPPTCL, subLDCs use all major functional areas of

SCADA except the 'Supervisory Control/Command' function. The

brief overview of major 'functional areas' of SCADA system is as

below:

1. Communications - Sub-LDC's computer communicates with all RTU

stations under its control, through a communication system. RTU

polling, message formatting, polynomial checking and message

retransmission on failure are the activities of 'Communications'

functional area.

2. Data Processing - After receipt of data through communication

system it is processed. Data process function has three sub-

functions i.e. (i) Measurements, (ii) Counters and (iii) Indications.

'Measurements' retrieved from a RTU are converted to engineering

units and linearised, if necessary. The measurement are then placed

in database and are checked against various limits which if

exceeded generate high or low limit alarms.

The system has been set-up to collect 'Counters' at regular

intervals: typically 5 or 10 minutes. At the end of the hour the units

is transferred into appropriate hour slot in a 24-hour

archive/history.

'Indications' are associated with status changes and protection. For

those statuses that are not classified as 'alarms', logs the change on

the appropriate printer and also enter it into a cyclic event list. For

those statuses, which are defined as an 'alarms' and the indication

goes into alarm, an entry is made into the appropriate alarm list, as

well as in the event list and an audible alarm is generated in the

sub-LDC.

3. Alarm/Event Logging - The alarm and event logging facilities are

used by SCADA data processing system. Alarms are grouped into

different categories and are given different priorities. Quality codes

are assigned to the recently received data for any 'limit violation'

and 'status changes'. Alarms are acknowledged from single line

diagram (or alarm lists) on display terminal in LDCs.

4. Manual Entry - There is a  provision of manual entry of measured

values, counters and indications for the important

sub-station/powerhouse, which are uncovered by an RTU or some

problem is going on in its RTU, equipment, communication path,

etc.

5. Averaging of Measured Values - As an option, the SCADA system

supports averaging of all analogue measurements. Typically, the

averaging of measured values over a period of 15 minutes is stored

to provide 24 hours trend.

6. Historical Data Recording (HDR) - The HDR, i.e. 'archive',

subsystem maintains a history of selected system parameters over a

period of time. These are sampled at a pre-selected interval and are

placed in historical database. At the end of the day, the data is

saved for later analysis and for report generation.

7. Interactive Database Generation - Facilities have been provided in

such a way that an off-line copy of the SCADA database can be

modified allowing the addition of new RTUs, pickup points and

communication channels.

8. Supervisory Control/Remote Command - This function enables the

issue of 'remote control' commands to the sub-station/powerhouse

equipment e.g. circuit breaker trip command. Though, there is

provision of this function in this system, yet it is not used in U.P. As

such, related/associated equipment have not been ordered.

9. Fail-over - A 'Fail-over' subsystem is also provided to secure and

maintain a database of devices and their backups. The state of the

device is maintained indicating whether it is 'on-line' or 'failed'.

There is a 'backup' system, which maintains database on a backup

computer and the system is duplicated.

SLDC Lucknow has a large and active 'Mimic Board' in its Control

room. This mimic board displays single line diagram of intra State

transmission system i.e. grid network of 400KV, 220KV and

important 132KV sub-stations, transmission lines, thermal & hydro

powerhouses. Outgoing feeders, shown in the mimic board, have

'achieve' (LED display) colored indications, of three different colors,

to show the range of power flow at any moment i.e. 'Normal',

'Nominal' or 'Maximum' of its line capacity. UPPTCL's transmission

network is expanding rapidly and thereby number of RTUs is also

increasing. For new substations and lines, displays in active and

passive forms are required to be made in the Mimic diagram. But,

Mimic Board has a limitation that it cannot incorporate/add large

volume of displays for substations/power houses/transmission lines

in 'active' form due to space constraint and congestion. Due to this

Mimic Board is going to be supplemented with a Video Projection

System (VPS) at SLDC, Lucknow in near future. Also in SLDC &

subLDCs, displays of single line diagrams of RTU sub-stations/power

house are viewed on VDUs of large size (21").

Transmission & reciver block diagram :-

Scada system diagam :-