IEEE C37.103-2015 pdf free.IEEE Guide for Differential and Polarizing Relay Circuit Testing.
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary On!int’ should be consultcd for terms not dcfined in this clause.
high-impedance scheme: A differential method of bus protection using CTs paralleled on a high-impedance load (a voltage or current relay in series with a stabilizing resistor).
linear coupler (IC): An air-corc instrumcnt transformcr, that like a currcnt transformcr, is intcndcd to havc its primary winding conncctcd in series with thc conductor carrying thc current to be monitorcd. The secondary excitation characteristic is a straight line, without any point of saturation. Hecause so much of the primary magneto- motive force is consumed in the magnetizing core, very little current can be drawn from the secondary; for this reason, linear couplers are connected in voltage. instead of current, differential circuits.
4. Operating considerations for personnel and equipment
A properly trained and equipped relay tester is important tór accident prevention. The tester’s actions can result in the operation of circuit breakers and motorized switches, which can affect the tester’s safety as well as that of others, Therefore, proper communication with all personnel in the area is important.
4.1 Primary testing
Whenever it becomes necessary to work on primary equipment. it is essential to observe all the necessary switching or locking and tagging procedures and to obey thosc procedures in a rigid and formalized manner. Operating and testing procedures should be followed to avoid exposure to substation equipment that has not been properly deenergized.
The primary testing procedures arc included to make this guide historically accurate. Primary testing procedures must be performed in compliance with all appropriate safety practices. The protected equipment must not be in service when primary current injection tests arc performed. The Working Group realizes that some of these procedures may not be possible due to personnel safety considerations, lack of suitable power supplies, and in the case of generators, very large current transformer (CT) ratios.
Modern relaying systems are designed around the use of dead-front relay and control panels and flexible drawout relays. Whenever possible. secondary relay circuit testing should be performed from the front face of (he relay panel through the use of thc relay test switchcs or icst connectors associated with drawout relays. Good cnginccring design practice should take advantage of these features for keeping the relay tester away from the live-rear side of the relay or control panel as much as possible.
At times, it may be necessary for the relay tester to work from the live-rear side of the relay or control panel. When working from that side, all componenis should be clearly labeled including wiring, terminal strips, and fuse blocks.
When ii becomes necessary to test equipment that is in service, care should be taken that the appropriate backup equipment is in operation.
4.3 Alternative to primary and secondary testing
Where primary andor secondary injection testing is not a normal practice, a preparatory test should be completed prior to energizing the equipment and completing the in-service testing. These preparatory tests should include as a minimum: vcrif’ing CT polarity and connections, ringing out circuits from the cquipmcnt to thc panels, verifying correct current paths through all the applicable relays, and verifying polarizing circuits andor voltage connections.
Use the techniques described in Clause 7, Clause 8. Clause 9. and Clause 10: modify the techniques to suit the particular application. Next, conduct the in-service tests, reading all current magnitudes and phase angles to determine correct connections.
4.4 Effect of opening CT circuits
An open-circuited (‘T secondary whose primary circuit is carrying current is hazardous. The soliage of the secondary winding of the CT attempts to rise to a value sufficient drive the proper secondary current through the impedance created by the open circuit (air gap). In the absence of secondary load current, the average voltage will rise to the rated excitation voltage, with peak voltages several times this value.
4.5 CT short-circuiting devices
Most CTs are connected to their burdens through a short-circuiting device located between the CT secondary and the relaying circuit or device under test. By proper use of the CT shorting device, it is possible to work on energized CT secondary wiring circuits without necessarily taking the primary equipment out of service, but there are pitfalls (e.g.,failing to short-currents before beginning of work may result in opening a CT circuit or damage to a relay such as a high- impedance differential relay, shorting currents feeding a differential circuit resuling in an unbalance and false trip).IEEE C37.103 pdf download.