High Impedance Fault Detection Method Research Articles

High-impedance fault detection technology based on transient information in a resonant grounding system

High-impedance faults (HIFs) occur frequently in resonant grounding systems and are difficult to detect. Thus, an effective HIF feeder identification technology is urgently in demand. An HIF equivalent circuit in a resonant grounding system is established. The magnitude and phase relationships of transient zero-sequence currents among the faulty feeder, healthy feeders, detection points, and fault point, as well as the relationships between their projection coefficients with respect to the transient zero-sequence voltage are analysed. A novel HIF detection method based on the comparison of the magnitude and polarity of the transient zero-sequence current's projection coefficient is proposed. The accuracy of the proposed method is verified by simulations and field data.

Straightforward Detection Method for High-Impedance Faults

High-impedance faults (HIFs) caused by fallen energized overhead lines (downed conductors) produce a serious threat for humans, livestock and property. Therefore, correct detection of HIFs is crucial for whole society. HIF current, 0.01-100 A, is in the range of load current and cannot be detected with traditional protection functions. Each HIF is also different, behave randomly and may be difficult to separate from normal network switching events. Therefore, many previous HIF detection methods over past decades have been based on adaptation, learning and on utilization of multiple algorithms. However, many of these methods are not suitable for tripping operation and can be only used as alarming HIF functions due to rather slow or complex decision logics and sensitivity to false detections. In this paper, new HIF detection method is proposed based on extensive PSCAD simulation studies and tests with real-life HIF measurements. The proposed method works in both 50 and 60 Hz networks and doesn’t need voltage measurement. It also works as tripping protection function with sufficiently short operation time, is simple/flexible and has good usability from end user point of view. It is applicable to low-resistance and solidly grounded MV networks.

웨이브렛 계수를 이용한 고저항 지락고장 감시데이터 산출방법 연구

As the increasing HIF(High Impedance Fault) with the arc cannot be easily detected for the low fault current magnitude compared to actual load in distribution line. However, the arcing current shows that the magnitude varies with time and the signal is asymmetric. In addition, discontinuous changes occur at starting point of arc. Considering these characteristics, wavelet transformation of actual current data shows difference between before and after the fault. Althogh raw data(detail coefficient) of wavelet transform may not be directly applied to HIF detection logic in a device, there are several developing methods of HIF monitoring data using the original wavelet coefficients. <BR> In this paper, a simple and effective developing methods of HIF monitoring data were analized by using the signal data through an actual HIF experiment to apply them to economic devices. The methods using the sumation of the wavelet coefficient squares in one cycle of the fundamental frequency as the energies of the wavelet coefficeits and the sumation of the absolute values were compared. Besides, the improved method which less occupies H/W resouces and can be applied to field detection devices was proposed. and also Verification of this HIF detection method through field test on distribution system in KEPCO power testing center was performed.

An adaptive high and low impedance fault detection method

An integrated high impedance fault (HIF) and low impedance fault (LIF) detection method is proposed in his paper. For a HIF detection, the proposed technique is based on a number of characteristics of the HIF current. These characteristics are: fault current magnitude; magnitude of the 3rd harmonic current; magnitude of the 5th harmonic current; the angle of the third harmonic current; the angle difference between the third harmonics current and the fundamental voltage; and the negative sequence current of HIF. These characteristics are identified by modeling the distribution feeders in EMTP. Apart from these characteristics, the above ambient (average) negative sequence current is also considered. An adjustable block out region around the average load current is provided. The average load current is calculated at every 18000 cycles (5 minutes) interval. This adaptive feature will not only make the proposed scheme more sensitive to low fault current, but it will also prevent the relay from tripping during the normal load current. In this paper, the logic circuit required for implementing the proposed HIF detection method is also included. With minimal modifications, the logic developed for the HIF detection can be applied to low impedance fault detection. A complete logic circuit which detects both the HIF and LIF is proposed. Using this combined logic, the need of installing separate devices for HIF and LIF detection can be eliminated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>