Publication: Analysis of backup distance protection on t-off configuration at 275KV substation in Malaysia
Date
2025-03-05
Authors
Umi Nadia Martaza
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Abstract
In an ideal case, it is impossible to have such a perfect and ideal configuration of transmission lines. Because of the tower's cost, switchgear such as circuit breakers, disconnectors, and wayleaves acquire more land to build the towers for transmission lines. This limitation may lead to different designs and configurations, like multiple terminals and tapped loads. Regardless of the transmission line configuration, an appropriate relay must protect the protected line. The tripping scheme must be adequate to maintain the system stability and restrict any damage to transformers and other primary equipment that feeds the fault. The transmission line was protected by a device called distance protection. Commonly, distance protection is used as backup protection. However, in specific scenarios, distance will be the primary protection if communication for differential relay fails. Distance protection is faster and more selective than overcurrent protection. It is also less susceptible to changes in the relative source impedance and system conditions. This paper presents the modelling and simulation of numerical distance protection relays. This study was carried out using Computer Aided Protection Engineering (PSSEĀ®CAPE). A sample case of the
existing line configuration, the two terminals (Loop in Loop Out) and proposed three terminal (T-Off configuration) 275 kV transmission lines in Malaysia, has been analyzed. Three-phase and single-line-to-ground faults were simulated on each 275kV transmission line section. The performance of the distance relay and fault clearing time for both configurations will be detailed and presented in this paper. The findings showed that three-terminal protection has been difficult to protect, even with digital communications and microprocessor relays, due to the infeed and outfeed effect. The result shows that elements are prone to underreaching on three-terminal lines due to the current infeed effect. To overcome the underreach problem, the revised setting is one of the suggestions proposed in this study. A performance and fault-clearing time simulation for the revised setting also has to be done. The result showed that with the revised settings proposed, the reach of settings and fault-clearing time could be improved in specific line sections. It is necessary to consider the selectivity of the
protection device and the system's reliability and security to reduce the disruption that occurs in the power system
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2023