Date Code 20001006 Setting Negative-Sequence Overcurrent Elements F-7
SEL-351 Instruction Manual
Ground Coordination Concerns
If the downstream protective device includes ground overcurrent elements, in addition to phase
overcurrent elements, there should be no need to check the coordination between the ground
overcurrent elements and the upstream negative-sequence overcurrent elements. The downstream
phase overcurrent element, whether it operates faster or slower than its complementary ground
overcurrent element, will operate faster than the upstream negative-sequence overcurrent element
for all faults, including those that involve ground.
OTHER NEGATIVE-SEQUENCE OVERCURRENT ELEMENT REFERENCES
A. F. Elneweihi, E. O. Schweitzer, M. W. Feltis, “Negative-Sequence Overcurrent Element
Application and Coordination in Distribution Protection,” IEEE Transactions on Power Delivery,
Volume 8, Number 3, July 1993, pp. 915-924.
This IEEE paper is the source of the coordination guidelines and example given in this
appendix. The paper also contains analyses of system unbalances and faults and the negative-
sequence current generated by such conditions.
A. F. Elneweihi, “Useful Applications for Negative-Sequence Overcurrent Relaying,” 22nd Annual
Western Protective Relay Conference, Spokane, Washington, October 24-26, 1995.
This conference paper gives many good application examples for negative-sequence
overcurrent elements. The focus is on the transmission system, where negative-sequence
overcurrent elements provide better sensitivity than zero-sequence overcurrent elements in
detecting some single-line-to-ground faults.
Courtesy of NationalSwitchgear.com
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