Evaluation of magnetic actuator driven switchgears in TNB

TNB Research (TNBR) carried out a research project to determine the most suitable types of circuit breakers for their 11kV air insulated switchgear (AIS) based on whether the circuit breaker is withdrawable or fixed and whether the operating mechanism is traditional spring or magnetic actuator. Six studies were carried out in this project. The evaluation found that truck circuit breaker is better than cassette circuit breaker due to maintenance, cost and space issues. Fixed switchgear has the advantages in terms of space, safety and cost issues over the withdrawable circuit breakers but have the disadvantages of maintenance and supplier availability in TNB´s context. It was also found that the magnetic actuator is suitable for use as the drive mechanism in 11kV switchgears. The magnetic material will not degrade during the lifetime of the switchgear even at the worst possible operating conditions and requires minimal maintenance. However, it will only be a viable alternative when the electronic components´ reliability is guaranteed; fixed AIS are used as a standard and the price become more competitive. Based on the study, TNBR recommended to its client that a field trial of several brands of fixed switchgear with magnetic actuator mechanism in a substation is required to study their performance in real-life situation.