On efficiency of digital system of power transformer proactive diagnostics

The purpose of the paper is to diagnose the state of a power transformer by determining its equivalent circuit parameters by means of synchronized vector measurements of currents and voltages in the transformer normal operation mode without shutdowns, which makes it possible to increase the reliability of relay protection operation. A cost-effective method for proactive diagnostics of power transformers is proposed. Through monitoring of additional parameters (short circuit resistance, active and inductive resistance of the positive sequence, active and inductive resistance of the negative sequence) it can increase the speed and accuracy of detecting possible internal short circuits arising due to winding damage or high-voltage transformer bushings without diagnosed transformer disconnection from the network. The method allows to estimate the transformer health index and serviceability by the difference between the calculated parameters of the equivalent circuit and the passport values of the parameters. Having conducted the damage cause dependent analysis of the number of power transformer damages, the authors determined total economic losses that include the losses caused by equipment damage and losses caused by the interruptions in consumer power supply. The total economic losses for a power transformer with a rated power of 63 MVA amounted to 10687402 rubles. It is shown that the diagnostic system expands the possibilities of analyzing the transformer state in operating modes, allows to prevent the approaching of the damage moment and occurrence of sudden accidents as well as minimizes the expected damage from shutdowns and equipment failure. A hardware and software complex is proposed for the diagnostics of power transformer internal damage. The given main characteristics of the proposed hardware and software complex include the number of measuring channels, accuracy class, sampling frequency, and others. The results of the work expand the possibilities of analyzing the transformer state in the operating mode and can be used in the world practice of creating various monitoring systems designed to identify the defects developing in transformers caused by winding deformation.

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