Zhiqin He

Wide-Area Backup Protection Algorithm Based on Fault Component Voltage Distribution

A new wide-area backup protection algorithm based on the fault component voltage distribution is proposed in this paper. It is helpful to overcome the problems of complex setting and maloperation under flow transfer of conventional backup protection. The measured values of fault component voltage and current at one terminal of the transmission line are applied to estimate the fault component voltage at the other terminal. Then, the fault element can be identified by the ratio between the measured values and the estimated values. In addition, the speed of fault element identification can be accelerated by a faulted area detection scheme. The proposed method has the advantage of easy setting and low requirement for synchronized wide-area data. The studies performed on the IEEE 39-bus system validate the proposed algorithm under various faults and flow transfer.

Wide-Area Protection Fault Identification Algorithm Based on Multi-Information Fusion

Wide-area protection systems can be used to avoid complicated setting coordination of traditional backup relays and effectively prevent cascading trip events. Since they depend on a multisource data of transmission network to identify a faulted element, fault-tolerance capacity of the system is required. This paper proposes a faulted element identification algorithm based on multisource information fusion for wide-area protection. A fault identification encoding method based upon grid topology is presented. Meanwhile, the operation information of traditional primary/backup relays and the status of breakers are utilized to establish fitness function and state expectation function. The fitness of protected elements is used to determine their fault probability; and faulted elements are identified with high fault tolerance. The property of the presented algorithm is validated by simulation tests based on an IEEE 10-generator 39-bus system.

Fault location in distribution networks base on the use of wavelet packet analysis

This paper presents a fault location procedure for distribution networks, based on the use of wavelet packet analysis of the voltage transients associated with the fault-originated traveling waves. The proposed method just needs the measured voltage transients recorded at the observation point without the need of multi-recording nodes and relevant synchronization. Fault-originated traveling waves propagate along the network and will be reflected back and forth between the observation point as mentioned above and the discontinuity points. Therefore, the traveling waves recorded at the observation point contain some characteristic frequencies associated with specific paths in which the fault-originated traveling waves propagate. The fault point can be located while the characteristic frequencies are identified. The effectiveness of the method has been verified by the simulation results in a typical distribution network.

Correction to “Wide-Area Backup Protection Algorithm Based on Fault Component Voltage Distribution” [Oct 11 2752-2760]

In the above titled paper (ibid., vol. 26, no. 4, pp. 2752-2760, Oct. 2011), Figs. 1 and 2 appear incorrectly. The correct figures are presented here.

Improvements for pilot protection in distribution grid with full converter wind turbines

Wind power gradually occupies important proportion in modern power grid. The influence of wind turbine generator (WTG) for protective relays has been studied in recent years, but a very few papers are presented to study relative influence to primary protection. This paper proposes a detailed analysis for the operating characteristic of transmission line primary protection in power network which are connected to wind farms. When fault occurs on tie lines, fault current is fast restricted by the regulating effect of full power converter and the operation of chopper protection. Consequently, indispensable improvements are illustrated to overcome the sensitivity deficiency of primary protection. Simulation tests based on IEEE 34-bus system with high wind penetration demonstrate the validity of presented methods.

Wide-Area Backup Protection Algorithm Based on Multisource Information Fusion

Wide-area backup protection is a novel technique presented in recent years, which uses multisource information to make fault identification decision and availably prevents catastrophic blackouts. However, the property of algorithm will be deteriorated when information error exists. For the sake of improving the property of wide-area backup protection, this paper proposes an information fusion strategy using genetic algorithm to optimize the decision-making function. The operation information from local directional pilot relay and impedance relay is applied to establish the fitness function. Simulation tests based on IEEE 3-generator and 9-bus system validates the presented algorithm under as many as 3 bits information error.

Study on Unbalance Factor of Sequence Impedance for Parallel Multi-circuit Cable Lines

Parallel multi-circuit cable lines are wildly used to improve the transmission capacity of urban power grid, but the study on sequence impedance parameters’ asymmetry of multi-circuit cable lines is not available. To analyze the asymmetry of multi-circuit cable lines’ parameters, a method to measure the unbalance factor is introduced in this paper. Furthermore, take engineering practice as an example, the electromagnetic unbalance factor of two-circuit cable lines under different arrangements are calculated by this method. Finally, a comparison among these unbalance factor is made. The comparative results show that the triangle arrangement has better symmetry than straight-vertical and straight-horizontal arrangement, in which the triangle-vertical arrangement’s symmetry is the best.

Communication Channel Reconstruction Technology of Wide-Area Protection Under Extreme Catastrophe

A new scheme of communication channel reconstruction technology (CCRT) for wide-area protection (WAP) under extreme catastrophe scenarios is proposed for the purpose of safeguarding the safety and reliability of relay protection. The communication hierarchy of WAP based on MPLS VPN is obtained according to the characteristic of communication system. Under the damage of optical communication channel, CCRT based on circuitous way is first realized by sturdy optical fiber, carrier, microwave and telecommunication channels and so on, and then CCRT based on wireless sensor network (WSN) is built when the circuitous path cannot reconstruct communication channel for more channels damaged. The key technology of WSN, such as the supply energy pattern, router algorithm and multi-hops way, are also discussed. The test results of multiple schemes show that CCRT based on WSN can be suitable for WAP.