Accelerated zone-2 trip algorithm for a non-pilot distance relay

Distance relays use time stepped protection zones for coordination purposes. The time delay introduced by zone-2 distance relays limits the use of these devices for extra high voltage (EHV) applications since the fast fault clearance requirement is not achieved. Transmission lines are normally protected by means of intercommunicated protection schemes that make use of a dedicated channel in order to overcome the delay. However, this channel is also prone to failure. It could be advantageous to provide the line with fast protection coverage for cases when a communication channel is not available. This thesis presents the analysis, simulation, and implementation of an accelerated zone-2 trip algorithm in non-pilot distance relays. This algorithm aims to provide fast fault clearance for transmission lines that significantly reduce the time-delay introduced by zone-2 distance protection. The algorithm can be used in two- or three-terminal lines by changing its setting values. Tests using an electromagnetic transients program (EMTDC/PSCAD) and Matlab are carried out to evaluate the performance of the proposed technique. The results are compared with the results obtained from two other techniques proposed in the literature. The results show the superior performance of the proposed technique over the other two techniques proposed in the literature. The fast fault clearance requirement of this algorithm is validated through its implementation in a DSP board and subsequent testing using signals generated by a real time digital simulator (RTDS) running a power system model. This DSP implementation also includes a simplified model of a distance relay. New developments in microprocessor-based relays (numerical relays) in terms of computing power and speed along with the simplicity of the proposed technique make the implementation of the algorithm possible in modern numerical distance relays. It is proposed that this algorithm be used as a fast backup scheme to protect two- or three-terminal lines in case the main communication channel degrades, fails or is not available.;Keywords: Distance Protection, Numerical Relays, Protective Relays, Relaying Algorithms, Transmission Lines.