Method of determining probability of unsymmetrical failure occurrence points in electrical networks and monitoring system intended for carrying out the method

摘要

The present invention relates to a method of determining probability of unsymmetrical failure occurrence points in electrical networks, where a backward chart of monitored distribution system is created, a coordination time of a failure occurrence is evaluated based on exceeding a change limit of a current negative phase-sequence component, records of change of a voltage negative phase-sequence component recorded on secondary sides of the distribution transformers (VN/NN) and records of negative phase-sequence components of currents withdrawn from feeding transformers (VVN/VN) are collected for the given coordination time of the failure occurrence. Subsequently, values of maximum change in the current and voltage negative phase-sequence components, corresponding to the instant at which the sum of all the recorded changes in the voltage negative phase-sequence components is maximal are determined. The values of the maximum change in the voltage negative phase-sequence components are converted to the primary side of a corresponding distribution transformer (VN/NN). Individual deviations of absolute values of the calculated changes of the voltage negative phase-sequence component and recorded values of the maximum change in the voltage phase-sequence component at the individual measuring nodes (MU) are then calculated from the converted maximum changes in the voltage phase-sequence components and the current phase-sequence components. Then total deviations of the absolute values of the calculated changes in voltage phase-sequence components and recorded values of the maximum changes in the voltage phase-sequence components for the individual nodes are calculated, and finally, a probability of occurrence of the asymmetry source in individual points of the monitored system is calculated.