Analysis of a New Fault Location Method for Medium Voltage Cable Networks

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Supervisor:
Dr. Raisz Dávid Márk
Department of Electric Power Engineering

Many methods have been developed for detecting single phase to ground faults appearing in medium voltage grids. Based on the fault detection method developed at the Department of Electric Power Engineering used on overhead networks, the opportunity arose to develop a similar method used on cable grids. In the case of cables, a possible fault is more severe because the insulation cannot regenerate, causing even more failures if the faulty part is not mended.

The aim of our investigation is to develop an algorithm which can immediately provide information about the place of a possible fault and the section that needs to be repaired. This is especially crucial for cable networks because the failure just like the whole grid is usually is especially crucial for cable networks because the failure just like the whole grid is usually invisible to the naked eye.

The basic problem is that there are more influencing factors affecting the value of electric parameters of power cables than of overhead lines and these factors are still under investigation. Further problems are that

1. the parameters of cables can deviate from the original values as the shield of the shielded cables corrodes during the course of time

2. the effect of closely placed cables on each other is not exactly known

3. the symmetry of cables in entire length of the line is not guaranteed, etc.

Therefore a possible solution could be that by means of measurements on the existing network, the cable parameters can be determined.

The method discussed in the present dissertation is based on detecting failures with the help of simulations carried out in a MATLAB environment. The investigation was carried out with existing types of cables on existing cable grids where the examined types of cables are in use.

The present work also discusses and evaluates results of international research on fault locations in medium voltage networks.

During the preparation of this paper, the author had the opportunity to examine the method using the results of a sequence of real measurements carried out on an existing medium voltage network.

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