Abstract
A thyristor-controlled series capacitor (TCSC) is employed to a transmission line in order to enhance the usable capacity of the present as well as upgraded lines, improve system stability, reduce losses, and improve power flow control capability. However, in an abnormal situation, the TCSC may transit from the existing operation mode to the other mode according to its control system and protection strategy. There is much difference in the impedance of the TCSC between each mode. This threatens the reliability of the conventional protection system, especially the distance relay, that works based on the measurement of line impedance. In this paper, we suggest a new protection scheme for a distance relay of a transmission line equipped with a TCSC. In the suggested method, in order to mitigate the effect of the TCSC in the fault loop, the TCSC injected voltage is subtracted from the measured phase voltage before supplying the voltage signal to the distance relay. The suggested scheme was verified by a real time digital simulator (RTDS)-based closed-loop test bed of a protective relay. The effect of the TCSC in the fault loop was completely mitigated. The distance relay works properly with the suggested scheme.
Highlights
In recent years, the increase in power demands requires the expansion of power generation and transmission
In this paper, we suggest a new protection scheme named as the voltage compensator scheme for a transmission line equipped with a thyristor-controlled series capacitor (TCSC)
In order to demonstrate the effectiveness of the proposed scheme, the operating characteristics of the protection relay RA1 with both the conventional and proposed schemes were analyzed with different fault types and fault location along line AB and line BC
Summary
The increase in power demands requires the expansion of power generation and transmission. The expansion meets the limit due to environment and resource restriction. To overcome this problem, flexible alternating current transmission system (FACTS) technology, such as thyristor-controlled series capacitors (TCSC) and high voltage alternating current (HVDC), is one of the possible solutions because it enhances the usable capacity of the transmission facilities and system reliability. By compensating the transmission line impedance, the TCSC enhances the power transfer capability and opens up the power control capability for the present and upgraded lines [1,2,3]. A TCSC consists of a capacitor (C) connected in parallel with a thyristor-controlled reactor (TCR)
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