A QIP Course on Smart Grid Technology: Smart Grid Protocols
Ankush SharmaAssistant Professor
Dept. of EE, IIT KanpurE-mail: [email protected]
Contents
Various Smart Grid Protocols
IEC 61850 Protocol
Tele-Control Protocols
DLMS/COSEM Protocols
Smart Grid Protocols and Standards- IEEE C37.118:IEEE Standard for SynchrophasorMeasurements for Power Systems- IEC 61970: Common Information Model (CIM) / Energy Management- IEC 60870-6: Inter-Control CenterCommunications Protocol- IEC 60870-5-104: Network access for IEC 60870-5-101 using standard transport profiles
- IEC 61850: Power Utility Automation- IEC 61968: Common Information Model (CIM) / Distribution Management- IEC 62056: Data exchange for meter reading, tariff and load control- DNP 3.0: Interoperability between substation computers, RTUs, IEDs and master stations
- IEC 62325: Deregulated energy market communications standards- AS 4777: Grid connection of energy systems via inverters- AS 4577: Framework for the control of electrical devices for DRM
- IEC 62351: Security- IEC 61508: Functional safety of electrical/electronic/ programmable electronic safety-related systems- IEEE 1588: Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems
Major Smart Grid Protocols/
Standards
Smart Grid Protocols and StandardsOther Smart Grid Protocols/ Standards –
Green Button - Initiative to provide utility customers with easy and secure access to their energy usage information in
a consumer-friendly and computer-friendly format
MultiSpeak -The specification is a standard for the exchange of data among enterprise application software commonly
applied in utilities
SunSpec - Open interoperability specifications and information models to achieve plug-and-play
interoperability between Distributed Energy Resource (DER) components and smart grid applications
SEP 2.0 - Standard for applications that enable home energy management via wired and wireless devices that support
Internet Protocol
IEC61850
IEC 61850Before IEC 61850 - Power substations were mostly managed by substation
automation systems that - Utilize simple, straightforward and highly specialized communication
protocols Less concerned about the semantics of the exchanged data
Devices from different manufacturers used different substation automation protocols, disabling them to talk to each other
Utilities were paying enormous money and time to configure the devices to work together in a substation
Hence, device manufacturers recognized the need for a unified international standard to support seamless cooperation among products from different vendors
The IEC 61850 international standard, drafted by substation automation domain experts from 22 countries
IEC 61850 Takes advantage of a comprehensive object-oriented
data model and the Ethernet technology Part 1 to Part 3 - general ideas about the standard Part 4 – defining the project and management
requirements in an IEC 61850 enabled substation Part 5 - specifying the required parameters for physical
implementation Part 6 - defining an XML based language for IED
configuration Part 7 - elaborating on the logical concepts Part 8 – mapping of the internal objects to the
presentation layer and to the Ethernet link layer Part 9 - mapping from sampled measurement value
(SMV) to point-to-point Ethernet
IEC 61850 – Substation ArchitectureIEC 61850 based Substation Architecture
IEC 61850 – System Overview
Source: ABB
IEC 61850 - VirtualizationLogical Representation of Device in IEC 61850-
IEC 61850 – Object Naming
Physical Device(network address)
Logical Device(e.g. Relay1)
MMXU1 MMXU2
MXMX
AV
Logical Nodes
Functional Constraint
“MMXU2$MX$A” =Feeder #2 Current Measurements
Anatomy of an IEC61850 Object Name
IEC 61850 – Object Naming
L System LN
P Protection
R Protection related
C Control
G Generic
I Interfacing and archiving
A Automatic control (4)
M Metering and measurement
S Sensor and monitoring
X Switchgear
T Instrument transformers
Y Power transformers
Z Further power system equipment
Examples:
PDIF: Differential protection
RBRF: Breaker failure
XCBR: Circuit breaker
CSWI: Switch controller
MMXU: Measurement unit
YPTR: Power transformer
Logical node groups
IEC 61850 – Communication ProfileC
omm
unic
atio
n St
ack
App
licat
ion
Dom
ain
IEC 61850 Communication Profile
IEC 61850 – Communication Profile
IEC 61850 Communication
Source: ABB
IEC 61850 Interface Model
Source: ABB
IEC 61850 - ACSIAbstract Communications Service Interface - ACSI
Defines a set of Objects
Defines a set of Services to manipulate and access those objects
Defines a base set of data types for describing objects
Example ACSI services – GetDataSetValue, CreateDataSet, DetDataDirectory
IEC 61850 - SMVSampled Measured Values (SMV)
IEC 61850 - GOOSEIEC61850 Generic Object Oriented Substation Event - GOOSE
Device to multi-device communication – Local or Wide Area
Bridgeable but Non-routable User-defined Dataset sent in an
Ethernet Multicast message Message sent on change of state as
well periodically to enable detection of device failure
Reliability effected through message repeat
GOOSE Header:• Multicast Address• Name• Time Until Next GOOSE• Etc.
User-Defined Dataset• Status Information• Analog Values• Data Quality• Time
IEC 61850 – GOOSE Messaging
IEC 61850 – GSSE/MMSGeneric Substation State Events (GSSE)
Only Status data can be exchanged through GSSE and it uses a status list (string of bits) rather than a dataset as is used in GOOSE
GSSE messages are transmitted directly over IEC/ISO 8802-2 and 8802-3 (IEEE 802.3) using a similar mechanism to GOOSE messages
As the GSSE format is simpler than GOOSE it is handled faster in some devices.
GSSE is being progressively superseded by the use of GOOSE and support for it may eventually disappear
Manufacturing Message Specification (MMS)
It is a messaging system for transferring real time process data and supervisory control information between networked devices and/or computer applications. MMS Defines the following -
A set of standard objects which must exist in every device, on which operations like read, write, event signaling etc. can be executed.
A set of standard messages exchanged between a client and a server stations for the purpose of monitoring and/or controlling these objects.
A set of encoding rules for mapping these messages to bits and bytes when transmitted.
IEC 61850 - SCLSCL – Substation Configuration Language
Description language for communication in electrical substations related to the IEDs
XML based language that allows a formal description of -– Substation automation system and the switchyard and the
relation between them– IED configuration– IEC 61850 language used in the XML files is called SCL
language
IEC 61850 - SCLSCL File Types
SSD: System Specification Description.
XML description of the entire system.
SCD: Substation Configuration Description.
XML description of a single substation.
ICD: IED Capability Description.
XML description of items supported by an IED.
CID: Configured IED Description.
XML configuration for a specific IED.
IEC 61850 - SCLSCL File Sample
SSD: System Specification Description.
XML description of the entire system.
SCD: Substation Configuration Description.
XML description of a single substation.
ICD: IED Capability Description.
XML description of items supported by an IED.
CID: Configured IED Description.
XML configuration for a specific IED.
IEC 61850: The SCL language (IED Modelling)
Bay Unit (IED)
PTRC (Trip, Operate)
SCL
Bay A
IEC 61850: The SCL language (IED modelling)
SCLSCL
IEC 61850: The SCL language (IED modelling)It is possible to “structure” the Logical Nodes, and group them under different Logical Devices.The “rules” of this structure are described in the XML file.
The SCL file also describes what the IED can do (services). In this case it seems that the IED cannot offer upload of disturbance recorder file, as the “FileHandling Service” is not listed:
IEC 61850: Services (IED modelling)
While this IED allows to upload the disturbance recorder files(FileHandling Service” is listed):
IEC 61850 - CIDCID File Generation
IEC 61850 - CIDCID File Generation
IEC 61850 - SSDSSD File
IEC 61850-90-5: Mapping with C37.118
IEC 61850-90-5: Mapping with C37.118
IEC 61850Benefits of IEC 61850
• IEC 61850 normally uses the approach of common information model (CIM) of real devices in terms of logical nodes (LN) for standardization
• High‐level services enable self‐describing devices & automatic object discovery saving money and effort in configuration and maintenance
• Standardized naming conventions with power system context eliminates device dependencies and tag mapping
• Standardized configuration file formats enables seamless exchange of device configuration
• Higher performance multi‐cast messaging for inter‐relay communications enables functions not possible with hard wires
• Multi‐cast messaging enables sharing of transducer (CT/PT) signals
Tele‐ControlProtocols
IEC 60870‐5‐101 protocol (Serial mode communication from RTUto Control Center)
IEC 60870‐5‐104 protocol (network mode communication fromRTU to Control Center)
IEC 60870‐6‐502 ( ICCP) protocol (between two Control Canters)
IEC 60870‐5‐103 protocol (for communication between IEDs in aSubstation)
DNP 3.0 Protocol (Serial)
DNP 3.0 Protocol (TCP/IP)
Tele-Control Protocols for SCADA
Area-LDC
SLDC
RLDC
SLDC
Area-LDC
RTU RTU
Wide Band /PLCC Commn
Wide Band Commn
Wide Band Commn
(MW / FO)
RTU
Wide Band Commn
Wide Band Commn
(MW / FO)
Three of the most important part of a SCADA system: Master Station, Remote Terminal (RTU, PLC, IED), and communication between them
Communication Channel for Information flow
A microprocessor‐controlled electronic device that interfacesobjects in the physical world to an SCADA system
Transmits telemetry data to a master SCADA system, and controlconnected objects based on SCADA Command.
SCADA master station gets status of a certain circuit breaker fromthe mapped status point of an RTU.
SCADA protocols consist of two message sets or pairs –
Master protocol, containing the valid statements for master stationinitiation or response
RTU protocol, containing the valid statements an RTU can initiate andrespond to
the message pairs are considered a poll or request for informationexchange
Remote Terminal Unit
RTU Dataflow
Standard polling The master station continuously requests the real‐time data values.
Exception reportingThe RTU is polled but only reports values that have changed since the prior poll
Push CommunicationsThe RTU initiates messages on an event or time basis.
Peer to peer communicationsRTUs can communicate with the master station and also with each other if there is a communication path.
RTU Communication
CFE
S
M
M
RTU
CFE CFE
M M
M M
RTU
Normal RTU
CFE
Critical RTU
LAN-ALAN-A
LAN-B LAN-B
RTU Connectivity Options
Based on the reduced communication reference model called Enhanced Performance Architecture (EPA)
Companion standards IEC 60870‐5‐101 and IEC 60870‐5‐104 are derived from the IEC 60870‐5 protocol standard definition
EPA includes three layers of the OSI model – Application layer Data Link layer Physical layer
* The ITU ( International Telecommunication Union ) Telecommunication Standardization (ITU-T)
IEC 60870-5 Protocol
101104
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Data Link
Physical
OSI EPA
7‐Layer 3‐Layer
Reason for 3‐Layered Structure of EPA ‐1) Short Reaction Time2) Reduced Transmission Bandwidth
Protocol Structure
Supports unbalanced (master initiated message) & balanced (master/slave initiated message) modes of data transfer
supports point‐to‐point and multidrop communication links carrying serial‐bit low‐bandwidth data communications
Link address and application service data unit (ASDU) addresses are provided for classifying the end station and sectors under same n/w
Data is classified into different information objects and each information object is provided with a specific address
Facility to classify the data into high priority (class‐1) and low priority (class‐2) and transfer the same using separate mechanisms
Possibility of classifying the data into different groups (1‐16) to get the data according to the group by issuing specific group interrogation commands from the master
Cyclic & Spontaneous data updating schemes are provided Facility for time synchronization schemes for transfer of files
IEC 60870-5-101
Physical Layer : Information (data) bit : 8 bitStart bit:1 , Stop bit : 1Parity bit : Even
Data Link LayerStandard Frame Format : FT 1.2 (frame format
of IEC 101 which is suitable for asynchronous communication)
Data Transmission at Link Layer ( Station address field Length : 1 or 2 bytes )Unbalanced Mode :
Transmitted messages are categorized on two priority classes( Class 1 & Class 2 )Balanced Mode :
All the messages are sent, No categorization of Class 1 and Class 2
Application LayerLength of header fields of data structure are:‐ Station address 1 or 2 byte ( User defined )‐ ASDU Address : 1 or 2 bytes‐ Information Object address : 2 bytes‐ Cause of Transmission : 1 byte
Network Layer : Not defined as 870‐5‐101 as it is not IP based
Selection of ASDUsASDU 1 : Single point informationASDU 2 : Single point information with time tagASDU 3 : Double point informationASDU 4 : Double point information with time tagASDU 9 : Measured value, Normalized valueASDU 10 : Measured value, Normalized value with timetagASDU 11 : Measured Value, Scaled valueASDU 12 : Measured value, Scaled value with time tagASDU 100 : Interrogation CommandASDU 103 : Clock Synchronization CommandASDU 120 ‐ 126 : File transfer Command
IEC 60870-5-101 Layers
IEC 60870-5-101 Data FrameFrame Length
Control Field
Address
• As balanced communications are point‐to‐point the link address is redundant, but may be included for security
• ASDU contains address of the controlling station in the ‘control direction’, and the address of the controlled station in the ‘monitoring direction’
• Unique address for each data element
Link Layer Balanced Transmission Link Layer Unbalanced Transmission
At the link layer, all devices are equal
restricted to point‐to‐point and to multiple point‐to‐point configurations
Collision avoidance by‐ Full duplex point to point connection
(RS232 or four wire RS485) Designated master polls slaves on n/w
Only Master device can transmit primary frames
Collision avoidance is not necessary since slave device cannot initiate exchange
If the slave device responds with NACK: (requested data not available) the master will try again until it gets data, or a response time‐out occurs
IEC 60870-5-101 Data Exchange
Based on data transmission via Ethernet (TCP/IP) An extension of IEC 101 protocol with the changes in transport, network, link &
physical layer services to suit the complete network access Application layer of IEC 104 is same as that of IEC 101 with some of the data
types and facilities not used offers considerable benefits compared with the serial data transmission ‐
Higher level safety Flexible network layout Numerous network utilities Simplified management of connected devices Reduced time and cost for maintenance and servicing
The security of IEC 104, by design has been proven to be problematic
IEC 60870-5-104
Operation of the lower layers of IEC 60870‐5‐104 is completely different from that of the IEC 60870‐5‐101.
These layers correspond to all the layers below the application layer, Architectures of these layers are concerned with how message transports happen.
IEC 60870-5-104
• Inter‐Control Center Communications Protocol (ICCP or IEC 60870‐6‐502)• To provide data exchange over wide area networks (WANs) between utility
control centers, utilities, power pools, regional control centers, and Non‐Utility Generators.
ICCP Protocol
AssociationsAn application Association needs to be established between two ICCP instances before anydata exchange can take place. Associations can be Initiated, Concluded or Aborted by theICCP instances.
Bilateral Agreement and Table for Access ControlA Bilateral Agreement between two control‐centers (say A and B) for data access. ABilateral Table is a digital representation of the Agreement.
Data ValuesData Values are objects that represent the values of control‐center objects includingpoints (Analog, Digital, and Controls) or data structures.
Data SetsData Sets are ordered‐lists of Data Value objects that can be created locally by an ICCPserver or on request by an ICCP client
Information MessagesInformation Message objects are used to exchange text or other data between ControlCenters.
Transfer SetsTransfer Set objects are used for complex data exchange schemes to transfer Data Sets (allelements or a subset of the Data set elements) etc.
DevicesDevices are the ICCP objects that represent controllable objects in the control center.
ICCP Protocol
Conformance Blocks• ICCP divides the entire ICCP functionality into 9 conformance block subsets• Implementations can declare the blocks that they provide support for• Specify the level of ICCP supported by the implementation• Any ICCP implementation must necessarily support Block 1Block 1 – Basic ServicesStatus and analogue points, quality flags, time‐stamp, protection events, association, data setBlock 2 – Extended Data Set Condition MonitoringProvides report on exception of the data types that block 1 is able to transfer periodicallyBlock 3 – Blocked TransfersProvides a means of transferring Block 1 and Block 2 data types as block transfers instead of pointby pointBlock 4 – Information MessageInformation Message objects, Simple text and binary filesBlock 5 – Device ControlControl requests: on/off, trip/close, raise/lower etc. and digital setpointsBlock 6 ‐ Program ControlAllows an ICCP client to remote control programs executing on an ICCP serverBlock 7 ‐ Event ReportingExtended reporting to a client of error conditions and device state changes at a server.Block 8 ‐ Additional User ObjectsScheduling, accounting, outage and other plant information.Block 9 ‐ Time Series DataAllows client to request server a report of historical time series data between start & end date
ICCP Protocol
• Secure ICCP is an extension of the existing standard ICCP.• Transport Layer Security (TLS) is inserted into the appropriate layer of
the standard communications profile• TLS is a certificate‐based cryptographic protocol that provides
encryption and authentication• Secure ICCP provides application layer authentication and message
encryption between ICCP servers.
Secure ICCP Protocol
Distributed Network Protocol (DNP), an open protocol, used between components in process automation systems
Based on Enhanced Performance architecture ( EPA) model Primarily used for communications between a master station and IEDs or
RTUs Supports multiple‐slave, peer‐to‐peer and multiple‐master
communications DNP contains Application and Data Link Layers, with a pseudo‐transport
layer DNP protocol is simply encapsulated within TCP/IP widely used over a variety of physical layers, including RS‐232, RS‐422, RS‐
485, and TCP/IP Supports the operational modes of polled and quiescent operation
DNP 3 Protocol
Pseudo‐transport layer(OSI Layer 4) used to build application data messages larger than a single data link frame
Uses FT3 frame format Can request and respond with multiple data types in single messages segment messages into multiple frames to ensure excellent error detection
and recovery designed to optimize the transmission of data acquisition information and
control commands from one computer to another Respond without request (unsolicited) provides interoperability between different vendor’s equipment provides multiplexing, data fragmentation, error checking, link control,
prioritization, and layer 2 addressing services for user data not designed to be secure from attacks by hackers
DNP 3 Protocol
DNP 3 Protocol Layers
The pseudo‐transport layer• To allow for the transmission of larger blocks of data • Network functions for routing and flow control of data packets over networks. • Transport functions provide network transparent end‐to‐end delivery of messages• Disassembly and reassembly, and error correction of messages.
DNP 3 Message Buildup
DNP 3 Protocol - FT3 frame format
• 10 byte header, followed optionally by up to 16 data blocks• Overall message size limited to 292 bytes, maximum data capacity of 250 bytes• Fully packed frame will comprise the header plus 16 data blocks, with the last
block containing 10 data bytes• START - 2 bytes: Start of frame• LENGTH - Count of user data in bytes• CONTROL - Frame control byte• DESTINATION - 2 byte destination address (LSB, MSB)• SOURCE - 2 byte source address (LSB, MSB)• CRC - 2 byte cyclic redundancy check code
DNP 3 - Message Communication
• In SCADA, some stations may be identified as master stations, and others as slave stations• There may be some devices that act both as slave stations and master stations• Master/slave distinction applies at the application level• At the data link level, the terms balanced and unbalanced • In ‘unbalanced’ systems, only master stations will initiate communications• The DNP3 protocol supports balanced communications at the data link level to provide
greater flexibility by allowing non‐master stations to initiate communications• In DNP3 any station can be an originator or primary station (Not necessary to be master)• Master/Slave used at the link level for setting of a message direction bit, the DIR bit.
DNP 3.0 IEC 60870‐5‐101
Standard Open Standard IEC Standard
Dominant Market North America Europe
Architecture 4‐layer architecture supports TCP/IP
3‐layer EPA architecture
Application Layer function
messages encapsulated in data link frames
Application functions specified in a data link layer message
Frames application layer messageconsist of many data link frames
Single application function require several messages to be sent to complete function
Transmission Only balanced Balanced and unbalanced
DeviceAddressing
pairs of devices may swap master and slave roles
pairs of devices will not swap master and slave roles
Frame Format FT3 FT1.2
DNP 3 Vs. IEC 60870-5-101
SmartMeterProtocols
IS 16444IS 16444 was adopted by the BIS in 2015 and consists of Two parts –
IS 16444 (Part 1): 2015 • Static Watthour direct connected meters consisting of measuring element(s), time of use
register (s), display, load switch, and built in / plug in type bidirectional communication module all integral with the meter housing.
• Smart meter for indoor use & capable of forward (import) or both forward (import) and reverse (export) energy measurement.
• Covers the general requirements and tests for a.c. static direct connected Watthour smart meter, class 1 & 2.
IS 16444 (Part 2): 2017• Transformer operated static watt-hour meters & Var-Hour meters consisting of
measuring element(s), time of use register(s), display and built in / plug in type bidirectional communication module all integral with the meter housing.
• Smart meter for indoor use & capable of forward (import) or import and export energy measurement.
• Covers the general requirements and tests for a.c. Static Transformer operated Watthour & Var-Hour Smart Meters, Class 0.2S, 0.5S & 1.0S.
IEC 62056• Set of Protocols for electricity metering data exchange (IEC TC13WG14)• International version of DLMS (Device Language Message Specification)/COSEM
(Companion Specification for Energy Metering)• COSEM contains set of specifications that define the Transport and Application
layer of DLMS protocol• DLMS users association defines protocol into set of 4 specification documents –
Green Book – DLMS/COSEM Architecture and Protocols Blue Book ‐ COSEM interface classes and OBIS (Object Identification
System) Yellow Book ‐ DLMS/COSEM Conformance Testing Process White Book ‐ Glossary of Terms
• Not only applicable to electricity metering, it is equally applicable to water, gas, and heating metering systems also
• All the data in electronic meters and associated devices are represented by means of mapping them to appropriate classes and attributes
• Specifies an interface model and communication protocols for data exchange with metering equipment
DLMS/COSEMThe DLMS/COSEM specification follows a
three‐step approach:
• Step 1, Modelling: Covers the interface
model of metering equipment and rules
for data identification;
• Step 2, Messaging: Covers the services
for mapping the interface model to
application layer protocol data units
(APDU) and the encoding of this APDUs.
• Step 3, Transporting: Covers the
transportation of the messages through
the communication channel.
Source: DLMS/COSEM Green Book
DLMS/COSEM Communication Model
Source: DLMS/COSEM Green Book
• Uses the concepts of OSI model to model information exchange between meters and data collection systems (DCS)
• Application functions of meters & DCS are modelled by application processes (APs).
• Communication between APs is modelled by communication between application entities (AEs)
• AE represents the communication functions of an AP.
HDLC ‐ High‐level Data Link ControlLLC ‐ Logical Link Control (Sublayer)SAP ‐ Service Access PointMAC ‐ Medium Access ControlUDP ‐ User Datagram ProtocolTCP ‐ Transmission Control Protocol
Client Server Model
Source: DLMS/COSEM Green Book
Connection oriented operation• The DLMS/COSEM AL is connection oriented• A communication session consists of three phases:
First, an application level connection, called Application Association (AA), is established between a client and a server Application Entities (AE)
Once the AA is established, message exchange can take place At the end of the data exchange, the AA is released.
• Servers cannot initiate the establishment of an AA• A COSEM logical device may support one or more AAs, each with a different client• Each AA determines the contexts in which information exchange takes place.
Source: DLM
S/CO
SEM G
reen Book
DLMS/COSEM Server ModelAC
SE ‐Association Co
ntrol Service Elemen
tAS
E ‐A
pplication Service Elem
ent
CO ‐Co
nnectio
n‐oriented
DLMS/COSEM Client Model