Abstract
Current differential protection is the main protection of transmission lines which include multi-circuit lines on the same tower, and whose sensitivity and reliability of differential protection is mainly affected by the distributed capacitive current. For the four-circuit line on the same tower, due to the influence of coupling between the loop road, the distributed capacitance current increases significantly when compared with ordinary lines, affecting the sensitivity of the current differential protection, especially for different voltage levels throughout the four-circuit lines on the same tower. The relationship of the electrostatic coupling between the circuits is more complex, and increases the difficulty of the compensating the distributed capacitance current. This paper is based on the electrostatic coupling principle of four-circuit lines on the same tower, establishes the distributed parameter model of four-circuit transmission lines on the same tower, and discusses the effect of circuit operation mode on the compensation of capacitance current differential protection when different faults occur on the complex four-circuit transmission lines on the same tower. A new compensation scheme suitable for capacitive current compensation is proposed. Simulation results show that this capacitive current compensation scheme can effectively improve the performance of current differential protection.
Highlights
With the fast development of the domestic economy and power load growth, the need to improve the transmission capacity of the power grid has become more urgent
If we take the first line as an example, C I1 = C I2 = CS1 + Cm1, which is namely the positive and negative-sequence compensation of the capacitance current from the line change of the mode of operation, it is easy to obtain the positive and negative-sequence distribution capacitive current magnitude, that is, the positive and negative-sequence capacitance current compensation is not affected by the change of line operation mode, so it is easy to obtain the positive and negative-sequence distribution capacitance current
Based on the above analysis, for a mixed voltage four-circuit transmission line on the same tower, an approximate assumption of the zero-sequence voltage of another voltage grade line is zero, the zero-sequence capacitance current compensation according to the operation mode of this voltage grade line is in normal operation and the other voltage grade lines are grounded for maintenance
Summary
With the fast development of the domestic economy and power load growth, the need to improve the transmission capacity of the power grid has become more urgent. Current on the linethese current differential protection, and have proposed a corresponding are differential protection, and proposedlines, a corresponding compensation scheme.multi-circuit These mainly aimed at whole transmission but in the actual project the segment linesare on mainly aimed at whole transmission lines, but in the actual project the segment multi-circuit lines the same tower exist, and the relationship of electrostatic coupling between the wires is more on the same tower exist, and the relationship electrostatic the wires is more complicated. The effects of different operation modestransmission (OM) on the compensation of current differential protection of four-circuit linescapacitance on the samecurrent tower compensation of current differential protection of four-circuit transmission lines on the tower were analyzed, through theoretical analysis and simulation calculations.
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