Title :
Energy variance criterion and threshold tuning scheme for high impedance fault detection
Author :
Lien, Keng-Yu ; Chen, Shi-Lin ; Liao, Ching-Jung ; Guo, Tzong-Yih ; Lin, Tsair-Ming ; Shen, Jer-Sheng
Author_Institution :
Dept. of Electr. Eng., Nat. Tsing Hua Univ., Hsinchu, Taiwan
fDate :
31 Jan-4 Feb 1999
Abstract :
Summary form only given as follows. This paper presents a new approach to the detection of high impedance fault (HIF). The proposed approach (or detector which implements this approach) has four distinct features. First, the detector input signal is the three-phase unbalanced current (or feeder 3I0), rather than the conventional three individual phase-currents. Secondly, the detector is designed by monitoring the energy variance for the second, fourth and sixth harmonics of 3I0 individually, and by requiring the increment of randomness of all these harmonics to indicate an HIF. Thirdly, a self-tuning scheme based on the statistical confidence is applied to the automatic setting of threshold level for the energy variances monitored. Fourthly, effective counters are designed to detect both persistent and intermittent arcings. The detector has been tested on 51 staged faults and 8 unfaulted feeders. The test results show that the detector can have 100% fault detection rate so long as the arcing current at fault location is not less than 5 A. As to the dependability tests, no false alarm (or tripping) has happened for all of the unfaulted feeders under test. These feeders either supply special (including arc furnace) load, or have leakage current (referring to the intermittent zero-sequence load due to the feeder location along coast), or are under the normal capacitor or load switchings. The test results and the investigation for the high sensitivity and dependability and for the limitation of proposed fault detection method are presented.
Keywords :
electric impedance measurement; fault location; leakage currents; power system faults; power system harmonics; power system measurement; arc furnace load; dependability tests; detector input signal; energy variance criterion; energy variance monitoring; fault detection rate; fault location; feeder location; fourth harmonic; high impedance fault detection; high sensitivity; intermittent arcing; intermittent zero-sequence load; leakage current; load switching; normal capacitor switching; persistent arcing; second harmonic; sixth harmonic; staged faults; statistical confidence; three-phase unbalanced current; threshold level; threshold tuning scheme; unfaulted feeders; Computerized monitoring; Counting circuits; Detectors; Fault detection; Fault location; Impedance; Phase detection; Signal detection; Testing; Tuning;
Conference_Titel :
Power Engineering Society 1999 Winter Meeting, IEEE
Print_ISBN :
0-7803-4893-1
DOI :
10.1109/PESW.1999.747300