C37.2-2008 Announcement rev4 for IEEE PES e-News 26 Nov 08

One of the most used IEEE standards – IEEE C37.2 – has just been updated and is now available for purchase. Its new title is IEEE C37.2 – 2008 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations. This was the first revision to IEEE C37.2 since 1996. There are substantial additions in this 2008 revision that will be of particular value to those adding Ethernet communications to substation control and protective relaying systems:-Acronyms are included for the first time - seventeen of them - for functions not previously in C37.2. (An Email survey showed that virtually all the old numbers are still in use and should not be retired.) -Device number 16 and a unique set of suffixes for substation communication networking devices have been added. This new device number and suffixes can be used to describe dual redundant configurations – Ethernet or serial RS232/485.

Other additions include:-Ten new suffix letter combinations to more completely define existing functions-A new “List Box” method of describing contents of a multifunction device.-A “Coordinated Trip & Close Fusing” elementary diagram-A three page cross reference table to IEC 61850 logical nodes

The Standard number (C37.2) may not be familiar to many control and protection engineers, although they have been using the notation methods in this standard for years. It is the documentation language for substation control and protection. When reading an elementary diagram today, there is no need, on the diagram, for a description of the symbols and nomenclature used. Device 52 is well known as an ac circuit breaker; 52a is recognized as a normally open auxiliary contact on an ac circuit breaker; 50 is an instantaneous overcurrent relay; 27 is an undervoltage relay, and 79 is a reclosing relay. These five functions, and almost ninety more, have been defined in IEEE C37.2 for years. It’s not common knowledge, but some of these function numbers date back to the original issue of this standard that began life as AIEE No.26 in 1928.

Over the ensuing years, many function numbers have been added to describe new functions, and by 1996 (the most recent past revision), all the numbers except 16 (labeled “Reserved for future application)” and 95-99 (labeled “are used in individual specific installations if none of the functions assigned to numbers from 1 through 94 are suitable”) had been used. The standard also reserved numbers above 99 as prefix numbers for multiple unit stations, or to use 100 series numbers for primary side functions and 200 series numbers for secondary side functions.

When the Power and Energy Society’s Joint Working Group – with members from PES Substations Committee and the Power System Relaying Committee as well as corresponding members from the Industry Applications Society - began its efforts to update C37.2, there were thought to be just seven new functions that were candidates for addition to C37.2. The first idea was that some of the old function numbers that dated back to the original AIEE No. 26 could be retired and reused. These were function numbers that were used to describe the control systems in “automatic railway substations” such as 10 – unit sequence switch, 22 – equalizing circuit

breaker, and 82 – dc load measuring reclosing relay. Since none of the working group members had any experience with dc traction system “automatic” substations where these numbers were used, the services of IEEE Strategic Planning were utilized to conduct a widely publicized Email survey. When the results were tabulated, it was clear that at least five of these seven function numbers were still in use - and the needs for additional functions had grown. At that point, the decision was made leave all the old function numbers intact. Instead, acronyms would be added for the new functions – and several acronyms already in common usage such as HMI and RTU, but not previously defined in the standard would be included. These seventeen acronyms, with the complete definitions of the functions they represent, are now in C37.2-2008: AFD – Arc Flash DetectorCLK – Clock or timing sourceDDR – Dynamic Disturbance RecorderDFR – Digital Fault RecorderENV – Environmental dataHIZ – High Impedance Fault DetectorHMI – Human Machine InterfaceHST – HistorianLGC – Scheme logic (the function, as in a RAS– not a device like a PLC)MET – Substation MeteringPDC – Phasor Data ConcentratorPMU – Phasor Measurement Unit (the function)PQM – Power Quality MonitorRIO - Remote Input/Output DeviceRTU – Remote Terminal Unit / Data ConcentratorSER – Sequence of Events RecorderTCM – Trip Circuit Monitor (added as a result of a ballot comment)

To further define the function numbers, ten new (to C37.2) suffix letters or combinations have been added:

• BU – Back up• DCB – Directional comparison blocking• DCUB – Directional comparison unblocking• DUTT - Direct underreaching transfer trip• GC - Ground check• POTT - Permissive overreaching transfer trip• PUTT - Permissive underreaching transfer trip• SOTF - Switch on to fault• TD - Time delay• Z - Impedance

In addition, device 16 is now defined as a Communication Networking Device with its own unique set of suffixes. The first suffix letter must be either E (Ethernet) or S (Serial RS232/485). Subsequent suffix letter choices are: C – security processing function (VPN, encryption, etc.) F – firewall or message filter function

M – network managed function (e.g configured via SNMP) R – router S – switch (Examples: port switch on a dial up connection is 16SS, an Ethernet switch is 16ES) T – telephone component (Example: auto answer modem)Example combination: 16ERFCM = Ethernet router / firewall / VPN / network managed

This nomenclature can be used to describe dual redundant schemes such as the following illustration:

In the 1996 revision of IEEE C37.2, two drafting methods to describe the contents of a Device 11 – multifunction device were added, but their usage has been sparse. The so- called “Empty Box” method conveyed no information and the “Filled Box” method was too cumbersome. This latest revision includes a “List Box” method. The following example from the Standard illustrates the use of the “List Box” method for System A in a dual redundant scheme for Line 1209 served by bus breaker 108 and mid breaker 118 in a breaker and a half substation configuration. There would be a similar list box for System B. (XXXX below the box indicates manufacturer model number)

The standard also includes a second example dc elementary diagram showing coordinated trip and close fusing, with a circuit breaker’s close circuit downstream of the trip fuses (so that the breaker could not be closed if the trip fusing was not intact). This diagram originally appeared in a Power System Relaying Committee Working Group Report in 1999, and has now been added to C37.2-2008:

Figure 5 Typical DC elementary diagram with coordinated control fusing

Annex D of the standard includes a very comprehensive cross-reference table to IEC 61850 logical nodes. Here is a portion of that three page table:

Functionality IEEE C37.2 ReferenceModelled in IEC61850-7-4

Comments

Transient earth fault PTEF

Directional earth fault

wattmetric protectionPSDE Sensitive ground fault protection

Checking or interlocking relay 3 CILO

Zero speed and under speed 14 PZSU

Security Processing Function 16EC or 16SC VPN, encryption module, etc.

Firewall 16EF Or message filtering function

Network managed function 16EM (e.g. configured via SNMP)

Router 16ER

Switch 16ES or 16SSExample: Ethernet switch is 16ES, Dial up port switch is 16SS

Ethernet Managed Switch 16ESM

Ethernet Router with Firewall, VPN for secure communications

16ERFCM See Annex A.2 Figure 2.2

Serial Encrypting Modem 16SCT See Annex A.2 Figure 2.1

Other serial communications components

16STExample: 16ST = Auto-answer modem or telephone switch

Distance 21PDISPSCH

IEC Use one instance per zone.To build line protection schemes

Volts per Hz 24 PVPH

Synchronism-check 25 RSYN

(Time) Under voltage 27 PTUV

To summarize, this was the first revision to IEEE C37.2 since 1996, and it was long overdue. Substantial additions have been made, but with almost no other changes:

-Added seventeen acronyms for new functions

-Used device #16 and a unique set of suffixes for substation communication networking devices. -Added ten new suffix letter combinations to more completely define functions-Added a “List Box” method to describe the contents of a multifunction device 11-Added a “Coordinated Trip & Close Fusing” elementary diagram-Added a comprehensive three page cross reference table to IEC 61850 logical nodes

This revised standard will be of value to all control and protection engineers.

John T. Tengdin – Life Fellow IEEEChair – Joint PES Substations Committee Working Group C5 / Power System Relaying Committee WG I14

Additional information on this revision is available on the PES Substations Working Group C5 web site: http://grouper.ieee.org/groups/sub/wgc5/index.htm

End Notes:There was a large balloting body for PC37.2, with members from the Power and Energy Society’s Substations Committee, its Power System Relaying Committee, and its Power System Communications Committee, from the Industry Applications Society’s Power System Protection Committee and its Rural Electric Power Committee, and from the IEEE Rail Transit Standards Subcommittee. The balloting process was particularly important to this project, as it was only through ballot comments that the working group received the suggestions to make three additions - the acronym TCM, the “List Box” documentation method, and the “Coordinated Trip and Close Fusing” diagram.

If you are a control and protection engineer who creates or uses elementary diagrams, you will need easy access to a copy of IEEE C37.2-2008 to take full advantage of all the changes and additions in this revision.

To all IEEE members who are not yet members of IEEE SA, we encourage you to join – so that you too can help improve IEEE standards through the balloting process.