Method and device for identifying phase-to-phase faults of excitation windings of AC excited synchronous motors

Abstract

The invention discloses a method and device for judging the inter-phase fault of the excitation winding of an AC excitation synchronous motor. A protection device measures the excitation winding current and the stator side voltage and current of the AC excitation synchronous motor; the harmonic components of the maximum phase current of the excitation winding side and the voltage and current of the stator side are calculated respectively in the frequency range from (fs-2fr.max) to (fs+2fr.max) where the fs frequency is filtered out, wherein the fs is the winding current frequency of the statorside, the fr. Max is the maximum excitation frequency of the excitation winding; and protection is performed with the maximum phase current on the excitation winding side as the main criterion and the harmonic components of the voltage and current of the stator side as an auxiliary criterion. When the maximum phase current of the excitation winding side is greater than the current setting threshold and the harmonic component of the stator side voltage is greater than the voltage floating threshold or the harmonic component of the stator side current is greater than the current floating threshold, the protection of alarming or tripping is performed by the delay t. The method and device can solve the situation that the traditional excitation winding over-current protection in variable speedpumping units is easy to be mis-operated when the stator side fails.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a method and device for judging phase-to-phase faults of excitation windings of an AC excitation synchronous motor. Background technique [0002] Most of the synchronous motors used in China adopt DC excitation, while AC excitation synchronous motors are rarely used, while foreign AC excitation synchronous motors are relatively more used, especially in variable speed pumped storage units. DC excitation synchronous motors have significant advantages in many aspects, such as the ability of deep phase advance operation, which can improve the transient stability of the system and improve the efficiency of unit operation. In the AC excitation synchronous motor, the excitation winding has 3 phases, and there is a possibility of phase-to-phase fault. After analysis, if a fault occurs on the stator side of the motor, the excitation winding of the moto...

AI Technical Summary

Problems solved by technology

In the AC excitation synchronous motor, the excitation winding has 3 phases, and there is a possibility of phase-to-phase fault. After analysis, a fault occurs on the stator side of the motor, and the excitation winding of the motor will also induce a large current. Therefore, the traditional excitation winding overcurrent There is a possibility of false operation of the protection in case of a fault on the stator side

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