IEC TR 61850-90-2, published in 2016, describes how to use IEC 61850 between the substation and the control or maintenance center: use cases, communication requirements, use of the SCL language, choice of services and architectures, engineering workflow and the proxy or gateway concept. Today most control centers still receive IEC 60870-5-104 or DNP3 from a gateway; end-to-end IEC 61850 is chosen when the operator supports it and wants a single data model.
The problem it solves
Inside the substation, IEC 61850 is the standard: IEDs are described in SCL files, exchange GOOSE and serve clients over MMS. But at the boundary with the control center the information almost always changes language. A gateway or RTU translates the logical nodes into IEC 60870-5-104 or DNP3 (IEEE 1815) addresses, and in that step names, quality and part of the context are lost.
The technical report IEC TR 61850-90-2, Using IEC 61850 for communication between substations and control centres, first edition February 2016, describes how to extend IEC 61850 to the control center or the maintenance center.
What the report contains
According to the scope published by IEC, the report covers:
- Use cases and communication requirements of the exchange between substation and control center: supervision, control, measurements, events, files and maintenance.
- Use of the IEC 61850-6 configuration language to describe that exchange.
- Guidance for choosing services and architectures.
- An engineering workflow between the substation and the control center.
- The proxy or gateway concept.
It is a technical report (TR), not a standard: it gives guidance, not mandatory requirements. How it is applied depends on what the substation owner and the control center operator agree on.
The IEC 61850 proxy or gateway
The control center does not connect to each relay. In the substation, one device acts as a proxy: inwards it is a client of the IEDs; outwards it is an IEC 61850 server and presents the control center with an image of the substation data.
The difference from a protocol gateway is that the proxy does not translate to another model. The data are still IEC 61850 logical nodes and data objects, with their names, quality and time stamp. What the proxy adds is concentration (a few outward connections instead of one per IED), selection of what is published and a single point of access control.
- 01Protocol gatewayTranslates logical nodes into 104 or DNP3 addresses with a mapping table
- 02IEC 61850 proxyKeeps the data model and presents it to the control center over MMS
- 03Wide area networkLink protected by a firewall, with channel redundancy
- 04Control centerReceives flat addresses or the full IEC 61850 model, depending on the path
Services that travel
The IEC 61850 services that make sense toward the control center are the client-server services over MMS:
- Reports, buffered or unbuffered, for status, alarms and measurements, which the proxy sends on change, on deadband or periodically.
- Controls, with select-before-operate and enhanced security, for breakers, disconnectors and tap changers.
- File transfer, for example fault records in COMTRADE (IEEE C37.111) format and event logs, useful for the maintenance center.
- Logs and queries of historical data when the devices support them.
GOOSE and sampled values are not part of this exchange: they are time-critical layer 2 messages between IEDs. Their use between substations has its own report, IEC TR 61850-90-1.
Engineering with SCL
With a protocol gateway, the control center database is built by hand from a mapping table. With end-to-end IEC 61850, the report proposes describing the interface in SCL, so that the control center imports what the substation publishes. This reduces transcription and naming errors, which are one of the causes of rework during integration. We explain SCL files in IEC 61850 SCL files.
Why 104 dominates today
- Installed base. Control center SCADA and EMS systems were built on IEC 60870-5-101/104, DNP3 or ICCP, and their databases and procedures are organized that way.
- Agreements with the operator. The supervision requirements of the system operator and of the utilities are usually expressed in those protocols.
- Boundary of responsibility. The gateway marks a clear line between substation engineering and control center engineering.
- Known cybersecurity. The security architectures for those links are already proven in each utility.
That is why most projects follow the gateway route with careful mapping, and keep end-to-end IEC 61850 for utilities that control both ends and want to unify the data model.
When end-to-end IEC 61850 makes sense
- Does the control center support IEC 61850 as a client?
- NoGateway to IEC 60870-5-104 or DNP3 with a documented mapping table
- YesDoes the same company control both the substation and the control center engineering?
- YesEnd-to-end IEC 61850 proxy with the interface described in SCL
- NoGateway, or a proxy agreed with the control center operator
In every case, the link leaves the substation behind an industrial router and firewall and with the protocol protection provided by IEC 62351.
We help with the integration
Tiza Group does the communications engineering of high and extra-high voltage substations and industrial plants: the full architecture toward the control center over IEC 60870-5-104, DNP3 or IEC 61850, the gateway mapping and the signal list. Gateway and IED settings can be configured or reviewed through remote relay configuration. Contact us.
Related guides
- IEC 61850: what it is, parts of the standard and data model
- IEC 61850 MMS: reports, SBO controls and files
- IEC 60870-5-104: what it is, how it works and how it is tested
- Substation RTU and gateway
- ICCP / TASE.2: link between control centers
- Substation communication network
- Mapping IEC 61850 to IEC 104 and DNP3 in the gateway
- Redundant gateway and dual links to the control center
- Substation communications by voltage level
- Substation signal list for SCADA
References
- IEC TR 61850-90-2:2016, Communication networks and systems for power utility automation – Part 90-2: Using IEC 61850 for communication between substations and control centres.
- IEC TR 61850-90-1:2010, Use of IEC 61850 for the communication between substations.
- IEC 61850-7-2: abstract communication service interface (ACSI).
- IEC 61850-8-1: mapping to MMS.
- IEC 60870-5-104: network access for IEC 60870-5-101.
Frequently asked questions
Does the control center connect directly to each relay over IEC 61850?
Usually not. IEC TR 61850-90-2 proposes a proxy or gateway in the substation that presents an image of the IED data to the control center. That way the control center keeps few connections and the substation network stays protected behind a single access point.
Why do almost all control centers still use IEC 60870-5-104 or DNP3?
Because that is what the installed SCADA and EMS systems support and what the supervision agreements with grid operators require. Moving to end-to-end IEC 61850 means changing the control center front end, its database and its way of doing engineering, not just the substation.
What does a utility gain by using IEC 61850 all the way to the control center?
A single data model and a single configuration language from the IED to the control center, with no intermediate mapping tables, signal names that are preserved and the possibility of generating part of the control center database from the SCL files.