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Short-circuit test

Short-circuit resistance tests or circuit-breaking capacity have the objective of verifying the performance of an MTCB, DCB, DAS in case of a fault, i.e. over-current several times higher than the rated current for periods of less than 1 second, so that the safety of users is guaranteed and the integrity of the equipment connected to it.

  • MTCB: Magneto-thermal Circuit Breaker
  • DCB: Differential Circuit Breakers
  • DAS: Differential Automatic Switch

Test methods

The test method established in the standard is based on performing a set of operation sequences switching power on and off at the same time as simulating a short-circuit. The most characteristic test sequences are as follows:

MTCB and DAS

  • At low currents: The simulated fault in this case is 10 times the rated current of the tested equipment.
  • At the short-circuit trip current when operating: This determines the capability of the device to clear a short-circuit including the ability to withstand 0-85 times the non-trip current for the conventional time.
  • At the short-circuit trip rated current: This determines the capability of the device to clear a short-circuit without including the ability to withstand 0-85 times the non-trip current for the conventional time.

DCB

  • Verification of the rated close and break power: This is to determine the capability of the device to establish, withstand and trip a fault if the differential current causes the circuit-breaker to trip out.
  • Verification of coordination between the DCB and the short-circuit protection device. They determine the capacity of the DCB to withstand damage caused by short-circuit currents up to the values defined by the manufacturer.