Circuit Breaker Testing

Circuit breakers constitute an important and critical component in the electric power system. Because of their key role, circuit breakers are periodically tested.


Our services for Circuit breaker inspections are as follows:

A. Operation times testing of Circuit Breaker

Important parameters describing the technical quality of a three-phase circuit-breaker are the so-called operation times characterising the processes of the contacts opening and closure.  The quantitative description of the switching on  and off process is usually made with the help of the mentioned below time parameters:

  • time discrepancy between the contacts td - interval time characterising  the divergence from coincidence of connection or disconnection of the breaker contacts (non-simultaneous switching).
  • closing time tc – the interval of time between energizing the closing circuit, the circuit breaker being in the open position, and the instant when the contacts touch the poles
  • opening time to of the breaker -. the interval of time between the instant of energizing the opening release, the circuit breaker being in the closed position, and the instant when the contacts have separated in all poles.


B. Contact Resistance Measurement

Stationary and moving contacts are built from alloys that are formulated to endure the abuse of electrical arcing.  However, if contacts are not maintained on a regular basis, their electrical resistance due to repeated arcing builds up.  This resistance build-up results in a significant decrease in the contact’s ability to carry current.  Excessive corrosion of contacts is detrimental to the breaker performance.  One way to check contacts is to apply dc current and measure the contact resistance or voltage drop across the closed contacts.  The breaker contact resistance should be measured from bushing terminal to bushing terminal with the breaker in the closed position.  It is recommended that for medium and high voltages the resistance test be made with 100-Amps (or higher) direct current.


C. Insulation Resistance Test

This test should be performed phase-to-phase and phase-to-ground (i.e., case, if applicable) with the breaker closed, as well as across the open contacts for each phase. For medium-voltage breakers, the manufacturer should provide the testing voltages and acceptance values for this test. When not available or where no recommendations are provided, the following abbreviated table from ANSI/NETA MTS-2007 may be used.


We have experience in testing Generator Circuit Breaker as well as low, medium and high voltage circuit breaker (6.3 – 150 kV Circuit breaker).