IEC 61850 Power Communications Standard - Commercial Ethernet switches need not apply!

IEC 61850 Power Communications Standard - Commercial Ethernet switches need not apply!

 
By Bill Lydon - Editor
 
Standard Requires Reliable Ethernet Switches
 
The Ethernet-based IEC 61850 international standards for communication in power generation facilities and substations sets a high bar for Ethernet switch reliability.  The goal of this standard is to integrate all of the protection, control, measurement, and monitoring functions within a substation. IEC 61850 provides the means for high-speed substation protection applications, interlocking and intertripping using devices generally referred to as Intelligent Electronic Devices (IED). The goal is to lower substation automation system deployment costs with IEC 61850 features; including self-describing IEDs, standardized object definitions, standardized naming conventions, standardized configuration language, and high-performance IED-to-IED communications.
  
IEC 61850 Overview
IEC 61850 uses object-oriented methods to provide logical communications between substations, primary process equipment, and secondary devices. Using object-oriented concepts, IEC 61850 abstracts the information models from the communication details. The protocol is implemented using a producer/consumer model, incorporating Quality of Service (QOS) and multicast to allow any unit to communicate with other units.  IEC 61850 also takes advantage of the Manufacturing Message Specification (MMS), an international standard (ISO 9506) dealing with messaging systems for transferring real time process data and supervisory control information between networked devices and/or computer applications. IEC 61850 also defines engineering process and conformance testing.
 
Part of the IEC 61850 standard is the Substation Configuration Language (SCL). This is a common language which can be used to exchange information, independent of the manufacturer.  The complete SCL representation and its details are specified in the IEC 61850-6 standard document and includes data representation for substation device entities.  All associated functions are represented as logical nodes, communication systems and capabilities. Each proprietary tool must have a function which allows the export of the IED’s description into this common, XML-based language. The ICD file (IED Capability Description) contains all information about the IED, which allows the user to configure a GOOSE message. 
 
The IEC 61850 GOOSE is an advanced version of the UCA GOOSE.  A GOOSE message is used to exchange data between IED’s (Intelligent Electronic Devices). GOOSE is a mechanism for fast transmission of substation events, such as commands and alarms. A single GOOSE message sent by an IED can be received and used by several receivers for fast messaging. One device (sender) publishes information, and only the devices configured as subscribers can receive it.  The reaction of each receiver depends on its configuration and functionality.
 
All ICD files get imported into the IEC 61850 System Configurator and the GOOSE messages can be programmed by specifying the sender (publisher) and the receiver(s) (subscribers) of a message.  The whole description of the system, including the description of the GOOSE messages, is stored in the SCD file (Substation Configuration Description) in XML.  Each proprietary configuration tool must be able to import this SCD file and extract the information needed for the IED.
 
The major advantage of using IEC 61850 is interoperability among IEDs from different vendors. It has a standard data naming convention, self-describing devices, virtualized modeling of logical devices, and a common language to configure devices.
 
Ethernet Switch Requirements
IEC 61850 implementations require Ethernet switches to have the same quality and ruggedness of the IEDs in the system. The IEC 61850-3 standard specifies the hardware design requirements for IEC 61850 devices used in substations.
 
Electrical Noise Immunity
Electrical substation and related applications must function under EMI conditions including inductive load switching, lightening strikes, electrostatic discharges from human contact, radio frequency interference (example: portable radio handsets), and high current fault conditions. IEC 61850-3 Communications Networks and Systems in Substations include the definition of a number of electrical immunity standards including:
  • 61000-4-2 (ESD)
  • 61000-4-3 (Radiated RFI)
  • 61000-4-4 (Electrical Burst Fast Transients)
  • 61000-4-5 (Surge)
  • 61000-4-6 (Conducted RFI)
  • 61000-4-8 (Power Frequency Magnetic Field)
  • 61000-4-11 (Voltage Dips – a.c. Power Supplies)
  • 61000-4-12 (Damped Oscillatory Transients)
  • 61000-4-16 (Mains Frequency Voltage)
  • 61000-4-17 (Ripple on d.c. Power Supplies)
  • 61000-4-29 (Voltage Dips – d.c. Power Supplies)
Operating Temperature Range
The wide temperature requirement is important since substation environments can experience temperatures as high as 75°C and as low as -40°C. The wide temperature requirement can be satisfied with an efficient heat dissipation design for extremely hot surroundings, and an intelligent self-warming system that kicks in when the temperature drops to extremely cold temperatures. The majority of IEDs in substations will be in “Class C” locations. Class C locations are further sub-divided into four classes: C1, C2, C3 and Cx. Operating temperature ranges for each of the classes are as follows:
  • Class C1: -5 to 45°C
  • Class C2: -25 to 55°C
  • Class C3: -40 to 70°C
  • Class Cx: -40 to 85°C
Anti-shock and anti-vibration
IEC 61850 devices must meet a 50G anti-shock and 5-500 Mhz anti-vibration requirement to ensure continued operation after being dropped from a rackmount in a device cabinet.
 
Network Diagram provided by RuggedCom
 
System Reliability
Ethernet switches are a fundamental building block in an IEC 61850 system and must have the same level of reliability as other components to maintain overall system integrity.  More Information.
 
The UCA International Users Group is a not-for-profit corporation - consisting of utility user and supplier companies - dedicated to promoting the integration and interoperability of electric/gas/water utility systems through the use of international standards-based technology. It is a User Group for IEC 61850, the Common Information Model – Generic Interface Definition (CIM/GID as per IEC 61970/61968), advanced metering and demand response via OpenDR.  IEC Website.