Wireless Supervision of a Rotating High-Speed De-excitation System for Brushless SM

The de-excitation process of a synchronous brushless machine takes several seconds. Consequently, in case of internal fault severe damages are produce despite de proper operation of the protection system. Several methods have been developed to solve this problem, some of them based on rotating resistor mounted in the rotor. The incorrect connection of the discharge resistor can produce damages in the resistor and consequently in the rotor of the synchronous machines. In this paper is presented that the loss of excitation protection is not suitable to detect this type of fault. And a new supervision method of brushless de-excitation systems is presented. It is based on the calculation of the theoretical excitation current of the exciter through a healthy machine model. This calculated current is compared to the actual one, which is measured. In case of connection of the discharge resistor in normal operation, the measured current is remarkable larger than the calculated one. This method has been validated by computer simulations.