Search

Evolving fault adversely affects the performance of the fault phase selector based on the differential superimposed phase currents (DSIPC), which is widely used in practical relay. It is because that this phase selector is designed only for simple fault, whereas the evolving fault is more complex in nature, comprising primary fault and secondary fault. In order to analyze the impact of the evolving fault on this phase selector, two new concepts are proposed, namely, the secondary fault network and the secondary fault component. The later is just the superimposed current utilized by the phase selector after evolving fault occurs. With the secondary fault network and secondary fault component, the performance of the phase selector under evolving fault is studied deeply. Analysis results show that source condition, fault type, fault position and fault resistance might cause the phase selector operates incorrectly.

This paper proposes a novel directional comparison protection. At its core is a directional element based on travelling waves. The directional element determines fault direction by the ratio of initial voltage and current travelling waves. In theory, if the ratio is equal to the surge admittance of the protected line, the fault is a reverse one; if the ratio is not equal to surge admittance of protected line, the fault is a forward one. In practice, appropriate thresholds are required and can also be set according to the practical situation. Using two directional elements and a proper communication channel, a new protection system can be constructed.

This paper presents a novel traveling wave differential relay based on wavelet transform for series compensated line. By detecting and utilizing the values and their arriving instants of travelling wave heads at both line terminals with wavelet transforms, the presented relay operates sensibly and reliably. The influence of series compensation (SC) is eliminated as SC has no effect on the propagation of travelling wave heads. EMTP simulations to a 500 kV series compensated transmission line demonstrate the performance of the presented relay.

A new adaptive noncommunication protection for double circuit systems is presented in this paper, which can trip the faults near the far end busbar. Two direction relays embedded with the new noncommunication protections are used in the technique. The protection algorithm is based on the comparison of the parallel line directions. Simulation studies show the stability of the protection under different fault conditions and systems.

For realizing the self-adaptive simulation of the whole transient, the class structure of the power system elements is researched by object-oriented modeling (OOM). By taking a generator for example, this paper builds the object-oriented self-adaptive models of elements and realizes the transform of subclasses. The object-oriented technology is also used to implement the simulating program. The simulating results verify that problems caused by the function-oriented method are solved.

Accuracy and reliability are the most important indexes to evaluate a transmission line fault location algorithm. Researchers have been focusing their efforts on the accuracy of the fault location algorithm, and the reliability of the algorithm seems to have been ignored before. In fact, if a fault location algorithm is exact but unreliable, it is of no use! It is necessary to give equal attention to accuracy and reliability. Robustness is one of the important factors to affect the reliability of a fault location algorithm. This paper firstly defines the robustness of fault location algorithm. Then it analyzes the robustness of five kinds of commonly used one-terminal fault location algorithms based on power frequency quantities. The simulation results demonstrate that robustness of algorithm is of much importance for ensuring a correct and trustworthy result of fault location, and the measurement resistance algorithm is the most robust algorithm so far.

When distribution power lines run normally, there is asymmetrical current and voltage component including negative sequence and zero sequence components. So non-communication protection based on sequence components might mal-operate or mis-operate in the cases. The paper proposed a new noncommunication protection scheme based on fault component for distribution line. The protection can be applied to different neutral grounding mode including direct and indirect grounding neutral system and isn't affected by normal running asymmetrical component. According to the fault component (or the incremental quantities of three sequence component), it can assure that one end breaker of fault line trips as quickly as possible and other end breaker is accelerated to trip. Simulation shows that the protection scheme is both correct and effective.

This paper presents a high-speed directional relay for the directional-comparison protection of EHV transmission lines using the power frequency fault components. The relay calculates the compensated voltage and the reference voltage firstly, then the direction of a fault will be determined by comparing the magnitudes of these two voltages. This relay possesses good performance, such as high sensitivity and fast action under various system and fault conditions. A 500 kV transmission system is modeled by EMTP. Simulation results show that the high-speed directional relay is sensible and reliable under different system configurations and fault conditions.

This paper presents a new principle of fault analyzing based on initial current traveling waves and a new algorithm of fault detection and fault phase selection based on the wavelet transforms. Through comparing the amplitudes of module maxima of wavelet transform in different scales, the fault can be detected. Through matching the characteristics of different fault types, the fault phase can be identified. This new approach of fault detection and fault phase selection, including the new principle and new algorithm, is specially designed for the ultra-high-speed protective relaying, which is based on the traveling waves. The use of the new approach provides an attractive potential solution to the long-standing problems of accurate and fast fault detection and fault phase selection. Extensive theoretical studies and simulations using EMTP have proved that the correctness and effectiveness of the proposed new approach.

This paper describes an assembled transmission line fault location algorithm based on one-terminal electrical quantities. It uses a fault location algorithm based on measurement impedance to calculate a fault section of a transmission line, then it uses a wavelet transform fault location algorithm based on current traveling wave to pinpoint the fault position. This algorithm deals with the conflict between accuracy and robustness of fault location algorithm successfully. The computer simulation demonstrates that the assembled fault location algorithm holds high robustness and high accuracy.

The current travelling wave is utilized to detect the fault position in the transmission lines in this paper. How to identify the incident travelling waves and reflected ones from the fault point when noises exist is discussed and resolved. A fault position relay based on current travelling waves and wavelets theory is designed. The relay's principle is mainly on wavelet theory and modulus maxima of the wavelet transform. By analyzing the distribution of the modulus maxima, different components in the current travelling waves can be distinguished and then the incident and reflected travelling waves are identified and finally useless components are filtered. The incident and reflected travelling wave's time difference arrival time difference indicates the fault position. An EMTP simulation example is illustrated. The relay is been proved correct and effective.

A new signal processing algorithm for arcing faults detection based on the high frequency current transient is presented in this paper. In transient faults, arc current extinguishes and then ignites, and this periodically disturbs fault current. After several cycles, when transient signals by the fault decay a lot, the arc disturbance can be identified by the wavelet transform. The feasibility of this algorithm has been tested by computer simulation.

The authors proposed and implemented a totally new solution for test and evaluation of relay performance. The newly developed testing platform can produce 8-channel synchronous high frequency transient voltage and current output to drive a protective relay and fault locator. It can also receive 8-channel response for recording and measuring operating performance and operating parameters of the relay.

Fault line selection is important to maintenance and normal operation of power distribution system. If a fault does not disappear for a long time, it could develop into a phase to phase fault. Then the fault line should be found out as quickly as possible and the fault should be removed. Thus, to select a good method of fault line selection is necessary. A transient signal may be a selection for fault line selection. A travelling wave is a transient signal. It will be more suitable to analyzing the single phase to ground fault because the fault itself is a transient process. But there are two problems to effect the use of the travelling wave signal: first, it is a high frequency signal, so it is hard to distinguish from noise; and secondly there is lack of a proper method to detect and describe the travelling wave signal. Traditional power signals analysis tools are limited in the presence of nonsteady signals. The travelling wave signal possesses a mutant property. In mathematics, it is the function of not only time but also frequency. These problems are solved with the wavelet transform. The new principle of fault line selection based on travelling waves and wavelet transform is presented.

As one of the most important elements in modern power system, the transformer is responsible for the successful power transmission and distribution. Any unscheduled repair work, especially replacement of a faulty transformer, is very expensive and time consuming. Starting from here, this paper discusses an approach to introduce a wavelet-based view to identify inrush and other transformer faults. Furthermore, by careful cataloging and comparing, the authors found distinct characteristics corresponding to fault and inrush, on the basis of which they proposed a generalized new criterion for inrush identification, that can help to enhance protection reliability. The outcome of numerical simulation shows the effectiveness of the algorithm.

This paper presents extensive studies of the application of wavelet transforms to detecting power system faults and describes a number of new protection principles and techniques based on the wavelet transform. These include a number of novel protection schemes for the protection of transmission lines, distribution feeders, generators and transformers. The significant advantages of these protection schemes are outlined in the paper. Finally the application of the proposed technique to busbar protection is presented to examine the feasibility of new protective algorithm.