Complex Faults: Using High-Quality Waveform Data to Understand Faults that Misbehave

Oscillography provides users data which can be used to analyze fault behavior. In digital relays, fault recording is often an “add-on” function that supplements the core mission of protection, rather than an integral component. For well-behaved faults, recordings from relays may provide sufficient information to determine a reliable sequence of events. Many faults, however, are not well-behaved, and it is these faults which are often the most important to analyze. It is not uncommon for faults on distribution systems to show substantial dynamic behavior over many seconds, including significant changes in fault current magnitude and/or phase involvement. In these cases, fault recordings from relays often have severe limitations in their ability to help utilities diagnose the root cause of underlying events and/or determine a reliable sequence of events.