Andrzej Kwapisz

Detection of the intermittent earth faults in compensated MV network

The experience acquired from the Polish medium voltage power distribution networks shows the unreliability of the localization criterions applied to the intermittent earth faults. It results from the lack of stability and low power level of the measuring signals falling often down below the protections start-up level. In the paper, a new adaptive algorithm based on the wavelet analysis enabling detection of specific dynamics of the measuring signal during intermittent earth faults is presented. The algorithm was analyzed utilizing the signals generated in the EMTP program package.

A fuzzy logic- based algorithm for discrimination of damaged line during intermittent earth faults

In the paper, the intermittent earth faults and their detection have been discussed. The intermittent fault belong to the most difficult detectable one due to its low and unstable measuring signals. The discussion has been carried out on the true fault recorded in the typical MV distribution network. It is shown that the criterion values applied, up to now, to the ground-fault protections can be ineffective. Therefore, two versions of an original measuring-decisive algorithm based on fuzzy logic have been proposed. With the algorithm, the faults detection referring to both the knowledge base and the member grade can be carried out.

Efficiency of admitance relays during faults with high fault resistance values in MV networks

In this paper efficiency of the different types of the admittance criteria is described during faults with high value of the fault resistance. The two types of fault are considered: high- ohm resistance in the fault loop and unbalance of the phase load caused by discontinuity of the line feeder with simultaneous occurrence of the ground-fault located behind the gap. Values of the zero sequence signals of current and voltage during those types of faults are shown.