Positive Sequence Fault Component Research Articles

Design and Evaluation of a Protection Relay for a Wind Generator Based on the Positive- and Negative-Sequence Fault Components

To avoid undesirable disconnection of healthy wind generators (WGs) or a wind power plant, a WG protection relay should discriminate among faults, so that it can operate instantaneously for WG, connected feeder or connection bus faults, it can operate after a delay for inter-tie or grid faults, and it can avoid operating for parallel WG or adjacent feeder faults. A WG protection relay based on the positive- and negative-sequence fault components is proposed in the paper. At stage 1, the proposed relay uses the magnitude of the positive-sequence component in the fault current to distinguish faults requiring non-operation response from those requiring instantaneous or delayed operation responses. At stage 2, the fault type is first determined using the relationships between the positive- and negative-sequence fault components. Then, the relay differentiates between instantaneous operation and delayed operation based on the magnitude of the positive-sequence fault component. Various fault scenarios involving changes in position and type of fault and faulted phases are used to verify the performance of the relay. This paper concludes by implementing the relay on a hardware platform based on a digital signal processor. Results indicate that the relay can successfully distinguish the need for instantaneous, delayed, or non-operation.

Design and evaluation of a directional algorithm for transmission-line protection based on positive-sequence fault components

A directional relay algorithm for EHV transmission lines using positive-sequence fault components is presented. By comparing the phase relationship between the voltage and current measured at the relay point, the algorithm can determine correctly whether a fault is in the forward or backward direction. Specially designed techniques and logic are adopted to solve the difficult problems that exist in a real system. The signal-processing procedure for extracting the required fault components is provided in detail. Extensive simulation studies were conducted on a 500 kV system model using EMTDC. Theoretical analysis and simulation results show that the proposed algorithm provides adequate sensitivity, reliability and a fast operating response under a variety of system and fault conditions. In addition, it provides significant advantages over conventional directional relays, and these are discussed in the paper.