Abstract
The identification of faulty feeder for single-phase high impedance faults (HIFs), especially in resonant grounding distribution system (RGDS), has always been a challenge, and existing faulty feeder identification techniques for HIFs suffer from some drawbacks. For this problem, the fault transient characteristic of single-phase HIF is analyzed and a faulty feeder identification method for HIF is proposed. The analysis shows that the transient zero-sequence current of each feeder is seen as a linear relationship between bus transient zero-sequence voltage and bus transient zero-sequence voltage derivative, and the coefficients are the reciprocal of transition resistance and feeder own capacitance, respectively, in both the over-damping state and the under-damping state. In order to estimate transition resistance and capacitance of each feeder, a least squares algorithm is utilized. The estimated transition resistance of a healthy feeder is infinite theoretically, and is a huge value practically. However, the estimated transition resistance of faulty feeder is approximately equal to actual fault resistance value, and it is far less than the set threshold. According to the above significant difference, the faulty feeder can be identified. The efficiency of the proposed method for the single-phase HIF in RGDS is verified by simulation results and experimental results that are based on RTDS.
Highlights
Distribution systems with neutral non-effectively grounding modes, which are ungrounded or grounded with arc-suppression-coil, are widely used in China and continental Europe
It is concluded from (11) and (12) that the transient zero-sequence current of healthy feeder is proportional to the bus transient zero-sequence voltage derivative, and the proportional coefficient is the feeder own capacitance; while, the transient zero-sequence current of faulty feeder is the linear relationship between bus transient zero-sequence voltage and bus transient zero-sequence voltage derivative, and the coefficients are the reciprocal of transition resistance and feeder own capacitance, respectively, under the circumstance of the over-damping state
It is concluded from (22) and (23) that the transient zero-sequence current of healthy feeder is proportional to bus transient zero-sequence voltage derivative, and the proportional coefficient is feeder own capacitance while transient zero-sequence current of faulty feeder is linear relationship between bus transient zero-sequence voltage and bus transient zero-sequence voltage derivative, and the coefficients are the reciprocal of transition resistance and feeder own capacitance, respectively, in the case of the under-damping state
Summary
Distribution systems with neutral non-effectively grounding modes, which are ungrounded or grounded with arc-suppression-coil, are widely used in China and continental Europe. Many research works trying to identify faulty feeder and detect single-phase fault for HIFs have been developed These methods can be divided into two groups: the active methods and the passive methods. Papers [8,9] recognize a faulty feeder on the basis of transient variation component that was caused by adjusting arc-suppression-coil These active methods have high accuracy, the identification requires additional signal injection or a coil adjustment device, which increases the cost. In order to detect HIF sensitivity, Mathematical Morphology [17], fuzzy reasoning [18], and time frequency analysis [19] are considered to extract fault characteristics in regard to HIF These methods almost focus on the directly grounded distribution system and they are not applicable to RGDS.
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