The IUP Journal of Electrical and Electronics Engineering
The Impact of UPFC on Operation of Distance Relay

Article Details
Pub. Date : Jul, 2020
Product Name : The IUP Journal of Electrical and Electronics Engineering
Product Type : Article
Product Code : IJEEE40720
Author Name : Gyanender Kumar, Ashish Kumar
Availability : YES
Subject/Domain : Engineering
Download Format : PDF Format
No. of Pages : 9



Distance relays are widely used for the protection of transmission lines. The accuracy of distance relay is affected by many factors like pre-fault system conditions, fault resistance, short-circuit and remote end-a condition which is not measurable at relaying point. These FACTS devices affect the impedance measured at the relaying point, and hence the trip characteristics of the relay is affected. In this paper, the effects of the introduction of Unified Power Flow Controller (UPFC), one of the FACTS devices, on the trip characteristics of the distance relay are studied. A comparison of ideal tripping characteristics with the UPFC-affected tripping characteristics is made and the variation of the tripping characteristics at different installation points of the UPFC is also shown.


FACTS devices help in controlling the reactive power in the power system, thus increasing the transmission capacity and providing the optimized utilization of system capacity. Wind farms are used as alternate source of energy in the grid. The great problem in using wind source is variations of wind speed throughout the day. It results in fluctuating output power; hence the system condition changes due to change in the wind speed. The dynamics of power system is greatly influenced by the introduction of FACTS devices; hence subsystems are affected, including the protection system. The distance relay works on the basis of impedance measured at the relaying point. Short circuit level, line load angle, fault resistance, voltage magnitude, source and grid impedances also affect the measured impedance at relaying point (Xia et al., 1994; and Li and Lai, 1997). Systems' other parameters affect only in the presence of fault resistance. In the absence of fault resistance, power system parameters have negligible effect on the measured impedance. Hence, the quadrilateral characteristics of the distance relay are used. The characteristics are subjected to mal-operation in the form of under-reaching and over-reaching the fault point in the presence of FACTS devices (Carpenter, 2000; Dash et al., 2000; and Dutra et al., 2004).


Distance relay, FACTS devices, Tripping characteristics, Unified Power Flow Controller (UPFC)

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