Experimental investigations using quadratic‐tripping characteristics based on alienation/coherence coefficients of voltage and current signals for synchronous generators protection

Abstract

Abstract A protection scheme is proposed using alienation method derived from coherence model which is a backup protection method for the differential overcurrent protection of synchronous generators. This scheme which is realized by the computational technique based on the alienation coefficients estimated for generator voltage and current signals is considered to be mounted beside the main differential protection system, which operates in the cases that differential protection is unable to detect the internal faults. This novel protection algorithm operates by adjusting the alienation settings of the suggested relay that sends the trip signal to the three‐phase circuit breaker of the protected generator. In the proposed method, fault occurrences can be determined regardless of variations of terminal voltage and current in different working states of synchronous generator. This is done by designing new quadratic‐tripping characteristics based on alienation limits for the electrical signals. To demonstrate the proposed method, a motor‐synchronous generator set with built instrument transformers, for measuring voltage and current data at the generator terminals, are used. Extensive experimental investigations validate the functionality of this novel protection scheme under different abnormal, unbalance and operating conditions for the generator under test.

Keywords

• Power system protection
• Synchronous machines
• Transformers and reactors
• Switchgear