Abstract
Compensating zero-sequence voltage measured is an effective measure to improve the sensitivity of zero-sequence directional overcurrent protections. However, when applied to double circuit power supply system, it may lead to misjudgment of zero-sequence directional elements. In order to avoid this, this paper first quantitatively analyzes the characteristics of the zero-sequence impedance measured by protective devices under such conditions as line-break faults, grounding faults, protection voltage taken from bus voltage transformers or line voltage transformers, etc. Then the safety boundary of compensation under various operation conditions is determined, and a new optimization lean compensation scheme is proposed for zero-sequence directional elements. In addition, simulation results based on PSCAD well verify the correctness and effectiveness of the proposed scheme and its derivation theory.
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