Dong Xinzhou

Fault position relay based on current travelling waves and wavelets

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 relays 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 waves time difference arrival time difference indicates the fault position. An EMTP simulation example is illustrated. The relay is been proved correct and effective.

Optimizing solution of fault location

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.

New approach of fault detection and fault phase selection based on initial current traveling waves

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.

Robustness of one-terminal fault location algorithm based on power frequency quantities

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.

New principle of high-speed directional relay

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.

Impact of evolving fault on fault phase selector based on differential superimposed phase currents

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.

Research on the system protection for enhancing the accommodation and transmission of large scale Wind Power

In the light of the operation of Jiuquan wind power base in recent years, the new relaying protection methods for enhancing the accommodation and transmission of large scale wind power are proposed from the system perspective, including the criterion of flow fluctuation based on the statistical analysis, the flow transfer recognition based on the local information, the adaptive overload protection, the fusion of the protection relay and the emergency control. On the basis of theoretical investigation and simulation, a protection device is developed and the correctness of the new methods is tested.

The parameters calculation and simulation research of two-type double-tuned filter

Due to harmonic problems generated by converter device of the high-voltage current system, the high-voltage direct current transmission (HVDC) system should adopt the double-tuned filter to inhibit the harmonics. This paper stated two new structures of double-tuned filter on the basis of the traditional double-tuned filter, that is two inductances paralleled structrue and two capacitances paralleled structure of double-tuned filter. In this paper, it calculated the parameters about new double-tuned filter with equivalent method and parametric method and analyzed the transient performance. At the same time, by use of the PSCAD software, the modeling and simulation of a calculated example of the new type of double-tuned filter which has a good filtering effect.

Real-time pricing of reactive power considering value of reactive power resources

Reactive power service is a significant part of ancillary service in the power market. It is also a necessary condition for ensuring the safety and stability in operation of power system and successful trading of power energy. In this paper, a method of equivalent reactive power compensation (ERC) is improved to measure the difference among reactive power resource value. An average method is proposed to define reactive value factors which are introduced to the optimal power flow (OPF) model. Then the real-time pricing model of reactive power is presented when both reactive power cost and value of reactive power resource are taken into consideration. The simulation results in the Wald-Hale 6-bus system shows that the model makes the system get more reactive power from reactive generations that have larger reactive power resource value and it also improves security and stabilization of power system.

New Algorithm for Fault Superimposed Quantities Based on Superimposed Network

A new algorithm for fault superimposed quantity (FSIQ) is presented and analyzed. The network equations are built up by combining fault superimposed networks (FSIN) with the boundary conditions of FSIQ at the fault point and are solved with the Newton iterative method. The algorithm has clear physical meaning and does not require an intermediate procedure to derive FSIQ. The algorithm is implemented by computer programming, and the results of calculations show that the algorithm is fast and accurate. The method can be used not only to calculate FSIQ in the complex power systems with simple or multiple faults, but also to analyze and evaluate the performance of the protective relays and automatic devices based on FSIQ.