Idaho Power is an electric utility engaged in the generation, transmission, distribution, sale and purchase of electric energy in the United States of America. Idaho Power serves more than 545,000 customers across a service area spanning an estimated 24,000 square miles in Eastern Oregon and Southern Idaho.

When a circuit breaker fails, it demands swift action to identify the root cause and rule out serious issues like faults in the system. When one of their breakers failed, Idaho Power understood the importance of investigating the cause of failure. As specialists in power system modeling and simulation, PSC was able to help Idaho Power examine the cause of breaker failure to ensure the utility could maintain the safe, reliable delivery of electric power.

PSC North America recently completed a study for Idaho Power to investigate the root causes for a breaker failure incident. A phase to ground flashover occurred in one of the phases of the said breaker after it was closed in order to energize the connected 345/230 kV autotransformer. PSC modeled the substation in detail using data provided by Idaho Power, and ran numerous electromagnetic transient (EMT) simulations on PSCAD™/EMTDC™ to determine if inrush, prestrike, or current chopping phenomenon could have caused extremely high voltages to compromise the insulating properties of the dielectric medium of the circuit breaker.

These tests found that none of the simulated scenarios produced large enough transient over-voltages to exceed the switching insulation withstand level of the circuit breaker because of switching transients. PSC also performed energization based on the synchronous closing logic for the transformer, concluding it was suitable as no excessive inrush current or over-voltage would be produced.

Based on PSC’s analysis, Idaho Power was able to rule out any lingering system issues that could cause problems when energizing the transformer with a new breaker with synchronized closing.

“PSC worked closely with Idaho Power to develop a holistic understanding of our system context,” said Orlando Ciniglio, System Planning Lead at Idaho Power.

“PSC’s expertise in power system simulation gave us the confidence to proceed with transformer energization, when system issues were ruled out.”

Following best practices for root cause analysis allowed Idaho Power to quickly replace the lost breaker while ensuring safe, reliable service for their customers.