Back To Basics

The testing required and the standards that must be met by a medium voltage power circuit breaker depend on the area of the world where the circuit breaker is applied.

A medium voltage power circuit breaker must meet the requirements of ANSI, IEC, IEEE and NEMA to be considered “world-class” (Figure 24).

Figure 24. Dominant Worldwide Standards

In addition, UL is an important consideration in certain local areas.

Standards and testing to prove compliance are rather stringent. This is because of the voltage and current levels associated with medium voltage equipment under abnormal (and even normal) operating conditions.

The testing goes beyond just testing the circuit breaker itself. Because a medium voltage power circuit breaker must function properly with a compatible housing, it is tested separately and in combination with the structural assembly. For this reason, most circuit breaker manufacturers are also switchgear assembly manufacturers.