Utility: Breaker Failure Detection
The Background

ACC has been implementing substation automation systems for PECO since the mid-90s. The overall architecture and components have changed over time in order to leverage new technology. The solution designed and implemented by ACC provides both remote and local control with full redundancy. Equipment health data, collected locally, is monitored at a master station.
The Challenge

The purpose of this project was to minimize the time an entire substation bus is down by leveraging information available in the Substation Automation Systems previously implemented by ACC. This information allows the identification of the circuit breaker with “trouble/probably fail” status. As a result, when a technician arrives at the substation, he is already armed with information regarding which circuit breaker is the likely cause of the outage.
The Solution

ACC created an application within the substation HMI that contains the mapping of each circuit breaker to its corresponding bus. The CBF Slow Breaker event detection identifies the probable breaker by evaluating the status of the corresponding breakers on the bus.

The solution consists of a new set of screens containing target history and target bus information were created in the substation HMI. The target bus screens contain the most recent targets with timestamps for all relays in a given bus. As soon as new targets occur for any relay, the target will be stored along with time and date. The application will then send an automatic target reset to that specific relay to clear the existing target so it is ready to receive a new target and detect a possible CBF Slow Breaker condition. Another screen contains the target alarm history including the last 10 targets for each feeder.

The CBF Slow Breaker event detection, which executes every 15 seconds, uses the predefined mapping of circuit breakers to distribution buses to determine when a CBF Slow Breaker event occurred, and to report the ID of the circuit breaker causing the event. The CBF Slow Breaker event detection works in the following way with conditions as noted:
  • When a new feeder target is identified and all of the circuit breakers on its bus open within a configurable time period a bus trip condition exists and a CBF Slow Breaker alarm is asserted
  • When a new feeder target is identified and that feeder remains closed for a configurable time period a CBF Slow Breaker alarm is asserted

  • Breakers already open are not evaluated in the CBF Slow Breaker alarm detection
  • If only one breaker on a given bus is closed then the circuit breaker fail logic will be disabled
Each new relay target is time stamped and stored in the target alarm history and displayed on the bus target screen and the relay target is automatically reset. This prepares the relay to receive a new target and trigger the CBF Slow Breaker event detection.

The CBF Slow Breaker application interfaces with PECO’s host SCADA system to communicate the event and breaker ID providing the dispatcher with the necessary information to allow field team to resolve the event.