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This paper analyses the formation mechanism of the transmission distortion of electronic voltage transformer, and points out that the integrator will magnify the transient transfer error and superimpose the dynamic additional component on the output signal, which may cause the transfer distortion of voltage signal in serious cases. To restrict the electronic transformer transient variable error effect on distance relay, a distance relay method using instantaneous value after equal transfer processes is proposed. It directly uses output differential signals of the capacitor voltage divider and Rogowski coil. The capacitor voltage divider and Rogowski coil are decomposed into several typical variable link in series. The virtual digital transfer link, which is constructed by the digital filter, is used to compensate for the difference parts of the transfer link, so that the voltage and current signals pass through the same transfer link. It can mitigate the influence of voltage and current signal transfer difference on the calculation accuracy of distance relay. The simulation results show that the proposed distance relay method has fast operation speed and is less affected by abnormal voltage and current signal transfer, and its performance is better than existing distance relay methods. [ABSTRACT FROM AUTHOR]

The capacitance isolation device is a kind of effective suppression of DC bias in transformers caused by HVDC monopolar operation. However, according to the actual operation of the system, the capacitive isolation device at the neutral point of a transformer will probably cause more serious DC bias in other adjacent transformers while inhibiting its internal bias current at the same time. Since autotransformers are applied widely in the high-voltage network, in this paper, we considered the structural characteristics of it and introduced the concept of effective bias current to describe the influence of magnetic bias current on the transformer more accurately. Then, the authors choose the bias current at any substations in the target grid less than the limit value as the constraint condition. Aiming at the minimum number of installed capacitors, the genetic algorithm based on improved niche is used to solve the optimal configuration problem. Taking the Ethiopia power grid as a test case, the authors work out the optimal quantity and installed location of capacitance isolation devices which satisfy the constraint condition. Compared with the traditional method, the cost is greatly reduced. [ABSTRACT FROM AUTHOR]