Testing IEC-61850 Sampled Values-Based Transformer Differential Protection Scheme

Following the successful implementation of IEC 61850 at station level over the last decade and enough user-experience on the standard, the significance of process-oriented communication using process bus is on an exponential rise. One of the key components of a process bus is information exchange among the devices through Sampled Values. Sampled Values (SV) are used for transmitting digitized values of currents and voltages on ethernet frames. With increase in industry acceptance of SV compliant protective relays, there is a crucial need for testing these relays and systems to ensure they meet operational and commissioning standards. Functional testing of SV-based protective relays with the help of a test equipment that can publish SV streams can be seen as a first step. This paper will discuss in detail on how to test through fault conditions, pick-up, slope characteristics, and harmonic restraints on a transformer differential relay that utilizes process bus to subscribe to current samples. Additionally, this paper will also discuss the effect of network anomaly and the importance of time synchronization in a process bus-based transformer differential scheme.