Circuit Breaker Failure and Restrike Monitoring Christopher Hutchinson

Lehigh University, Energy Systems Engineering

This project will investigate the current state of the art measurement techniques for assessing the restrike of circuit breakers when used on utility systems for capacitor bank switching, focusing on technologies capable of capturing accurate real time measurements of the restrike voltage wave profile and identifying the triggering event.

• Voltage Measurement • Difficult to measure directly off of capacitor bank due to extremely high voltage (500 kV). • Transformation may disrupt transient signal. • Best course of action is to use PPL’s monitoring line (220 V). It was determined that transience would still be visible. • Additional possible method is using an electric field sensor to detect transient voltages. This method is currently being investigated.

• Current Measurement • Current is constant throughout capacitor bank, so measurement may be take at any point on the structure. • Best course is to use a current transformer installed on the grounding wire of phase A.

• Data Acquisition • Suggested minimum sampling rate of 64 samples/cycle (3,840 samples/sec). • Data acquisition unit will work with a laptop computer housed in the building with the voltage monitoring line.

• Voltage and current measurement techniques were identified and tested in a small scale laboratory setting. • Data measurement system installed at Albertis substation for full scale test. • System installed at Juniata substation for measurement.

I would to thank Dr. Richard Decker (Lehigh University) for working diligently on this project with me. David Soyster (PPL) has been an invaluable resource as well. I would also like to thank PPL engineers Nick Zeyman, David Neff, and Jeff Gilbert.

• This project is currently ongoing.

• A reliable system using a current transformer and a transimpedance amplifier has been designed.

•  Voltage measuring will be accomplished using PPL’s monitoring line.

• A data acquisition device within budget has been identified.

• Satisfactory laboratory testing will result in system being installed at the Albretis substation, followed by the Juniata substation.

• Ideal results will show clear transient voltages (Figure 3) and currents (Figure 4) indicative of a restrike.

• This system could then be used at other substations to monitor the occurrence and frequency of restrikes.

Figure 1: Closed circuit breaker

Figure 2: Partially open circuit breaker with restrike shown

• Restrikes cause poor quality of power, and are damaging to equipment.

• Monitoring of restrikes may provide better quality of power to customers and longer life to equipment

ABSTRACT

INTRODUCTION

METHODS

CONCLUSIONS AND FUTURE WORK

ACKNOWLEDGEMENTS

METHODS (cont)

Picture 1: 500 kV circuit breaker

Figure 3: Restrike voltage wave profile

Figure 4: Restrike current wave profile

Picture 2: Capacitor bank structure

Picture 3: Current measurement location