Protection of Double-circuit Transmission Line Using Superimposed Current

Abstract

This article presents a differential protection scheme for a double-circuit transmission line using a superimposed component of current. The proposed scheme is based on the ratio of directional current difference setting value to directional current bias setting value of the respective phase at both ends. These two quantities are derived based on the difference and the summation of the superimposed currents of the respective phase. The proposed scheme provides proper discrimination between in-zone faults and out-of-zone faults during complete loss of generation at one of the buses. Further, it is highly sensitive toward high-resistance faults and provides instantaneous operation to the entire line. Moreover, the relay provides reliability and selectivity for discriminating cross-country faults and internal faults and remains stable against external faults. The proposed scheme has been tested under different fault conditions with varying fault resistance between 0-200 . A series of tests using test signals generated by PSCAD/EMTDC (Manitoba HVDC Research Centre Inc., Winnipeg, Manitoba, Canada) on realistic data of a part of the Indian 400-kV power transmission system network have proved the accuracy and effectiveness of the proposed scheme.

Transverse differential protection scheme for double‐circuit lines with single‐pole tripping and reclosing

“…All algorithms using current from the past as polarizing quantity, [9][10][11][12][13] including selected ones, would be inapplicable in this case. After SPT event, the current measured at both ends of line 1 becomes equal to 0 (i 11 = 0 and i 12 = 0), meaning that corresponding current samples also become equal to 0.…”

“…The main goal of this article is to solve considered protection selectivity problem for algorithms using only current signals. [9][10][11][12][13]…”

“…However, there is no yet widely available information about the usage of transverse differential protection based only on current signals in the field applications. According to the conclusion in Bhalja and Purohit, which states that there is no perfect algorithm of this type developed in the last decades, it can be only assumed that industry still mainly uses voltages as polarizing quantities.…”

“…The solution was proposed in the same article in the form of a new algorithm with directional element using current samples from the past for calculation of polarizing quantities. Bhalja and Purohit 12 highlighted transverse differential protection sensitivity problem in the case of faults when total generating capacity at one circuit end is out of service. According to research results from previously published article, 13 it is shown that algorithm proposed in article 11 fails to provide sensitive protection in the case of faults in singly fed double‐circuit lines with low consumption.…”

“…The key advantage of algorithms proposed in previous studies 11‐13 is that voltage signals are not required as polarizing quantities for determination of differential current direction, which reduces protection costs and keeps its simplicity. However, there is no yet widely available information about the usage of transverse differential protection based only on current signals in the field applications.…”