Lessons learned from commissioning protective relaying systems

Commissioning protective relays has changed with the increased use of microprocessor-based relays. Many relays have multiple functions, and logic that used to be contained in wiring diagrams or control schematics now resides in relay settings. However, the newer relays also provide many advantages in commissioning, including: (1) Event reports that show a precise capture of voltage and current waveforms, inputs and outputs, and relay elements. (2) Sequential Events Recorders (SERs) that show time-stamped assertion and deassertion of relay elements. (3) Metering and synchrophasor data that can be used for instantaneous monitoring of input signals. Using personal experiences and those learned from working with field personnel, we provide a variety of testing examples on transmission, distribution, and plant systems. We show what the expected performance is, what to look for, problems to avoid, and lessons learned from system data taken from relays during commissioning.