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New balance ground relay for parallel four‐circuit transmission lines
Author(s) -
Kai Takaaki,
Nomura Shizuo,
Ando Takeshi
Publication year - 1992
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/eej.4391120102
Subject(s) - ground , current (fluid) , relay , electric power transmission , fault (geology) , symmetrical components , protective relay , electrical engineering , resistor , engineering , control theory (sociology) , fuse (electrical) , topology (electrical circuits) , computer science , voltage , physics , transformer , power (physics) , control (management) , quantum mechanics , artificial intelligence , seismology , geology
A 66‐kV network generally is grounded through a neutral grounding resistor. In this network a single‐phase ground‐fault current is limited to as small as 100 to 400 A. There are parallel four‐circuit transmission lines mounted on the same tower in the 66‐kV network. In such transmission lines, the load and the fault currents could induce circulating current that flows through the lines. Since the circulating current has zero‐phase‐sequence and negative‐phase‐sequence components, it could cause unwanted operation of a balance ground relay using zero‐phase‐sequence current. However, it is difficult to compensate for the circulating current by the conventional vector compensation scheme. This paper presents a new balance ground relay to deal with the circulating current. In the relay from the ground‐fault inception until first tripping, the difference current Δ3 I 2 d of negative‐phase‐sequence current 3 I 2 d of the differential current between two protected lines is used as an input current. The Δ3 I 2 d is the difference current of 3 I 2 d between, before and during faults. After the first tripping, the difference current of positive‐phase‐sequence load current and zero‐phase‐sequence current of the forementioned differential current are used as an input current. Consequently, a higher sensitivity of the ground‐fault protection for these lines has been achieved. The correct operation of the new balance ground relay was confirmed when a single‐phase‐ground‐fault occurred in the parallel four‐circuit transmission lines, to which the relay is applied.