With the growing popularity of IEC 61850, there is a mistaken belief by some that office grade Ethernet devices may be used with impunity in an electric utility substation. But there are substantial differences between these two environments that cannot be ignored. As a starter, substation control houses are usually not air conditioned, insulated, or forced ventilated. So the equipment in those house must withstand temperatures never seen in an office.

Then when high voltage disconnect switches are opened (not a fault, just a switching operation), transients are generated that couple on to the control wiring that runs from the high voltage yard into the control house. And in the control house, the simple act of de-energizing an auxiliary dc relay (one designed to have a low battery drain) will create fast rising transients in the control wiring. The vital equipments, that must operate during loss of station power, are supplied by DC from the station battery. Roving operators are still using five watt transceivers (walkie-talkies) in close proximity to critical equipment that can cause malfunctions. And new substation control houses have floor coverings that will produce high levels of electrostatic discharges.

The industry's protective relay engineers recognized these environmental hazards to critical equipment in a substation control house, and developed a series of standards addressing each of the issues. IEEE Std? C37.90 defines control power voltage ratings and tolerances, insulation testing, altitude and derating factors for altitude. The latest update (2005) includes a requirement that the temperature ratings be achieved without fans or forced ventilation. The switching surge and fast transient immunity is defined in IEEE Std C37.90.1. RF immunity to hand held walkie-talkies is defined in IEEE Std C37.90.2. Electrostatic discharge immunity is defined in IEEE Std C37.90.3. All of these are appropriate for protective relays interconnected by direct wiring. The criteria for passing these tests is, in essence, no physical damage and no false trips.

Then along came communications networks in substations. Some early installations used Ethernet devices from commercial suppliers - which were only designed for pristine office environments - and there were failures. The electric utility industry and its suppliers recognized the need for a substation oriented standard and formed a task force in 2002 within the IEEE Power Engineering Society's Substations Committee. The goal of that task force was to develop a standard for communications networking devices (hubs, switches, routers, modems, firewalls, etc.) in substations by building on the work done in the IEEE C37.90 series of existing protective relay standards. But since this was to be a standard for communications devices, the major challenges were 1) to define the communications that were to be ongoing during the C37.90 series defined tests, and 2) to define the criteria for passing the tests.

The result was the publication in 2003 of IEEE 1613 Standard Environmental and Testing Requirements for Communications Networking Devices in Electric Power Substations.

That standard defines these two performance classes for these devices:

"Class 1. This performance class is for communications devices used for general purpose substations communications where temporary loss of communications and/or communications errors can be tolerated during the . . . . . transients. All devices shall meet Class 1 requirements unless Class 2 is specified by the user or manufacturer.

"Class 2. This performance class is for communications devices used in substations communications where it is desired to have error-free, uninterrupted communications during the occurrence of the . . . . . transients."  The . . . . . transients include switching surges, fast transients, RF immunity from five watt walkie-talkie transceivers, and from electrostatic discharges.

The standard also defines the method of capacitive coupling the switching surge and fast transient voltages to the comm lines during the tests. Given the severity of these transient tests, the net effect of this Class 2 requirement (error-free, uninterrupted communications during the occurrence of the . . . . . transients) is that only fiber optic comm lines will pass the test. The only exclusion is from this test is "Connections that, as stated by the manufacturer, shall be less than 2 m in length".

In addition, IEEE 1613 states:  "The following conditions are to be met by both Class 1 and Class 2 devices:

• No hardware damage occurs.
• No loss or corruption of stored  memory or data, including active  or stored settings, occurs.
• Device resets do not occur, and  manual resetting is not required.
• No changes in the states of  the electrical, mechanical, or communication status outputs occur. These outputs include
• alarms, status outputs, or targets.
• No erroneous, permanent change of state of the visual,  audio, or message outputs  results. Momentary changes of  
• these outputs during the tests   are permitted.
• No error outside normal tolerances of the dat communication signals  (e.g., SCADA analogs) occurs."

Due to an oversight, IEEE Std 1613-2003 does not include the altitude and altitude derating factors that are a part of IEEE Std C37.90. So work is now underway on an amendment to add those requirements to IEEE 1613. No other changes have been proposed. It has been a very stable standard. As one can see, the requirements in IEEE 1613 are comprehensive (and soon to be more so).  For the utility, compliance with IEEE 1613 is the best way to specify equipment expected to not only survive, but to operate correctly, in a substation environment.

Since its publication in 2003, IEEE Std 1613 has been regularly cited by major manufacturers of substation communications equipment (modems, Ethernet routers, switches, etc.) and by many specifying utilities. When a manufacturer states their equipment is "substation hardened", one should ask "Does it meet IEEE 1613?" To this writer's knowledge, this is the only standard for substation communications devices that requires transient immunity testing while communications are underway.