Communication networks and systems in substations

February 2004

Part IEC 61850-5 "Communication requirements" has been published as IEC Standard

Part IEC 61850-6 "Configuration language" has been approved for publication as IEC Standard

Part FDIS IEC 61850-8-1 "Mapping of services (SCSM) to MMS (ISO/IEC 9506 Part 1 and Part 2) over ISO 8802-3" has been approved for publication as IEC Standard

Part FDIS IEC 61850-9-2 "Mapping - Sampled values over ISO/IEC 8802-3" has been approved for publication as IEC Standard

May 2003

The IEC has this week (May 11-17, 2003) published five new parts in the IEC 61850 series of standards (Communication networks and systems in substations):

IEC 61850-7-2 Abstract communication service interface (ACSI)
IEC 61850-7-3 Common data classes
IEC 61850-7-4 Compatible logical node classes and data classes
IEC 61850-9-1 Specific Communication Service Mapping (SCSM) - Sampled values over serial unidirectional multidrop point to point link

Learn first-hand from Karlheinz Schwarz:

Member of IEC TC 57 WG 10 und WG 11, TC 57 SPAG, IEC TC 88 PT 25, ...
Editor of IEC 61850-7-2, IEC 61850-7-1, and IEC 61400-25 (Communications for monitoring and control of wind power plants)
Member of the editor's team IEC 61850
Member of new working Groups on IEC 61850 for Hydro Power Plants and DER
Chairman of several national and international standardization groups

Interested in an inhouse seminar on IEC 61850, IEC 61400-25, ICCP (TASE.2), UCA (R) ?

Introduction IEC 61850

Dealing with automation systems, it offers a seamless communication solution for electric substations and the basis for decentralized power generation, e.g. for wind power plants (standard under preparation: IEC 61400-25).

Deregulation of the energy markets is expanding at an ever faster pace these days, the consequences being increasing competition among utilities. Closed energy management systems are no longer sufficient. Communication and exchange of information with external systems are a necessity for the planning, operation and maintenance of power systems, as well as for the business side dealing with power transmission and distribution. Equipment and systems have to be interoperable, and interfaces, protocols and data models must be compatible to optimize to use of the power system in the energy market.

IEC 61850 provides:

standardized information models like circuit-breaker, transformer, and so forth ,
information exchange methods to access the data of the information models, report sequences-of-events (SoE), log historical data, control devices, sampled value distribution, fast peer-to-peer process data exchange, etc.
an unified system configuration language (XML based) and device online self-description,

for the following applications:

protection and control,
integration of innovative sensor and switch technologies,
metering, supervisory control and data acquisition (SCADA),
remote monitoring and fault diagnosis,
automated dispatch and control,
asset management,
condition monitoring and diagnosis

Thanks to the seamless real-time communication system based on IEC 61850, future power systems will be smart at the top and smart at the bottom and self-regulated by millions of communicating intelligent electronic devices (IED) connected to optimize the complete chain from power generation to customers. All critical information about the power system will be consistently available at any time and anywhere when making control decisions.

Users and vendors benefit from the standard in a similar manner because IEC 61850:

is a global standard,
uses mainstream technologies like Ethernet, TCP/IP, Object modelling, and XML,
is highly flexible and scalable
reduces operation, engineering and maintenance costs,
is a seamless solution for cross-application requirements,
reduces the diversity of solutions to be supported,
is applicable in various other application domains.

IEC 61850 on a page ...

Parts just published (May 11-17, 2003):

IEC 61850-7-2 (2003-05) order information

Communication networks and systems in substations - Part 7-2: Basic communication structure for substation and feeder equipment - Abstract communication service interface (ACSI)

The communication means defined in IEC 61850-7-2 allow the exchange of all process related information (sampled value exchange, fast peer-to-peer process data exchange, edit setting groups, control devices, report events (sequence-of-events), and log events historically) and the online exchange of all configuration information. The services are defined in an abstract way, that means they need to be mapped to a specific application layer protocol (e.g., ISO 9506 - Manufacturing Message Specification, MMS). The mapping to MMS, TCP/IP, and Ethernet is defiend in IEC 61850-8-1. IEC 61850-7-2 provides services for all known and crucial applications in substations. The services are independent of the information models. They can be applied in many other application domains, e.g., in the distributed power generation domain.

IEC 61850-7-3 (2003-05) order information

Communication networks and systems in substations - Part 7-3: Basic communication structure for substation and feeder equipment - Common data classes example CDCs

The several hundred data classes defined in IEC 61850-7-4 are based on a few very common templates (the common data classes, CDC) to specify their content. Some 30 CDC are defined that fall into the following groups: status information, measured information, controllable status information, controllable analogue set point information, status settings, and analogue settings. Each logical node in IEC 61850-7-4 is defined by a name (e.g., XCBR - for circuit breaker) and a list of many data classes. Each data class has a name (e.g., Pos - breaker position of the XCBR). The data have many named attributes defining details of the value like timestamp, quality, substitution, SI unit, deadband, description). These details are defined in the common data class (e.g., DPC - controllabe double point).

The data derived from a specific data class describes the data completly: with regard to all details and the communication services that can be processed by that data. The CDCs link the data defined in IEC 61850-7-4 with the information exchange services contained in IEC 61850-7-2.

Almost all common data classes may be used in many application domains outside the substation domain. IEC 61850-7-3 is a key specification because it is the foundation of the information model (comprises process and meta data).

IEC 61850-7-4 (2003-05) order information

Communication networks and systems in substations - Part 7-4: Basic communication structure for substation and feeder equipment - Compatible logical node classes and data classes list of logical nodes and example: "XCBR" - circuit breaker

Provides a set of modules of a comprehensive substation specific information model (e.g. for Automatic Control, Supervisory control, Metering and Measurement, Protection Functions, Sensors, Monitoring, Instrument Transformer, Switchgear). Some 100 modules (the logical nodes) comprise function related information (so-called data classes) and represent all common semantic intelligent electronic devices (IEDs) used in substations. The standard defines some 500 data classes to support the development of compatible devices - independent of the vendor. The standard will be used - in conjunction with the configuration language (IEC 61850-6) - to design devices that can openly communicate with each other . Devices having implemented these models - in conjunction with the communication means defined in IEC 61850-7-2 - can exchange all function related information (sampled values, fast peer-to-peer process data, editable settings, control commands , event reports (sequence-of-events), and logged information, configuration data) online. All data classes used are based on common data classes (CDC), which are defined in IEC 61850-7-3.

The information model reduces the efforts (time and money) to design, implement, engineer, maintain, and operate IEDs.

IEC 61850-9-1 (2003-05) order information

Communication networks and systems in substations - Part 9-1: Specific Communication Service Mapping (SCSM) - Sampled values over serial unidirectional multidrop point to point link

With IEC 61850-9-1, a global standard for a digital interface especially for non conventional voltage and current transformers is now available. IEC 61850-9-1 describes a serial point to point communication link used to transmit the sampled values from instrument transformers to protection relays, control and metering devices of a substation automation system. The communication link is realised by Ethernet with priority tagging according to IEEE 802.1p/Q.

When using non conventional intrument transformers like rogowski coils or optical sensor systems, digital interfaces according to IEC 61850-9-1 will replace the 100V / 5A analog interface used so far with conventional instrument transformers.

More details ...