Testing High Voltage Circuit Breakers with Both Sides Grounded Using Dynamic Capacitance (DCM) Technology

High voltage circuit breakers have traditionally been tested with at least one side of the contacts disconnected from ground. This has mainly been due to the challenges that arise when trying to test a circuit breaker with both sides grounded. Although this has been the accepted practice for many years, it has always put the test engineers or technicians at an increased safety risk. In order to perform circuit breaker timing under safer conditions, different methods of testing with both sides grounded have been developed using various technologies. This paper will explore Dynamic Capacitance Measurements (DCM) as a method for timing circuit breakers. DCM uses a variable high frequency source to find the path of least impedance within a parallel circuit of the circuit breaker and ground, as well as establishing resonant points that change depending on whether or not the circuit breaker is open or closed. If these resonance points are monitored while the circuit breaker is operated, accurate contact open and close times can be measured safely and efficiently. The basic functionality of dynamic capacitance measurements and how they can be applied to both air insulated and gas insulated switchgear will be explored along with case studies and comparisons to traditional testing.