A review of pole slipping protection

With the growing number of small and medium sized synchronous generators embedded in sub-transmission and distribution systems, the probability of pole slipping is growing and therefore pole slipping protection is becoming more important. Machine winding damage, system problems, and shaft failure can all result if adequate protection is not provided. The availability of powerful microprocessor based relay hardware has enabled new techniques to be considered to provide protection against pole slipping. These include a new power based pole slipping protection algorithm. This has been shown to be effective in detecting the onset of pole slipping and hence is able to disconnect the generator before the dramatic current surges can occur. The pole slip used to illustrate the operation of pole slipping protection was not designed to be particularly testing for any technique and considerable effort was put into choosing the most appropriate settings for the impedance based relays so that they provided the effective protection. The results, however, clearly demonstrated the difficulties of using impedance based pole slipping relays and the immediate advantages of the power based algorithm, the setting data for which is normally supplied with the generator. Using power as the basis for the detection of pole slipping proved advantageous