Performance testing of complete digital relays based on ATP-EMTP and IEC61850-9-2

The complete digital relays are used increasing widely in recent years, where the traditional analog, hardwired and interface have been replaced by non-conventional instrument transformers and the digital communication link (process bus) based on IEC 61850-9-2 standard. It is shown that these new techniques will make a strong impact on relay performance testing. General methods of testing protective relays will be reviewed, including static characteristics testing, dynamic simulation and real time digital simulator (RTDS). Approaches for testing IEC 61850 compatible relays based on RTDS offer significant advantages when compared with other methods. However, the RTDS simulator is designed with powerful software and expensive hardware, which is not convenient enough to test complete digital relays. This paper presents the design of new relay performance testing scheme, especially for complete digital relays. At first, power system model is established in ATP-EMTP and fault transient data in accordance with COMTRADE will be obtained by offline simulation. Subsequently, transient data are converted to IEC 61850-9-2 format through the static relay testing instrument. Finally, the complete digital relays directly receive the fault sampled value by process bus and Ethernet switcher, and relays will act or not. The new testing scheme will be applied more efficiently to researching the complete digital relays, as the scale of testing is out of the limitation of simulator´s hardware. A brief example by the new testing system is presented at the end of the paper.