Application of transient based methods for improving the selectivity and speed of protection systems used in active distribution networks
Date
2020-04
Authors
Karasin Pathirannahalage, Amila Nuwan Pathirana
Journal Title
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Abstract
The interconnection of distributed energy resources (DER) alters the radial structure of distribution systems and the character of fault currents resulting in delayed operation, reduced sensitivity, or loss of coordination of the traditional protection algorithms that rely on the fundamental frequency current and voltage phasors. Alternative protection techniques that are more immune to problems created by DER can be developed using fault generated transients in the currents and voltages, but they suffer from the lack of security against the transients from normal events, limited bandwidth of instrument transformers, need for hardware with high-frequency sampling and signal processing power. This thesis examine methods to overcome the above concerns with respect to a transient based protection algorithm that relies on a comparison of the polarity of current transients observed at the boundary of a protected zone.
In order to accurately measure current transient polarities without additional digital signal processing resources, a new sensor consisting of a ferrite core coil and analog electronics is proposed. A detailed model of the sensor including frequency-dependent hysteresis characteristics of the ferrite core was developed for simulation studies. The model was implemented in PSCAD electromagnetic transient simulation software and validated against a sensor prototype.
The security of protection against the non-fault related transients is improved through a hybrid protection structure that combines the transient based protection algorithm with traditional overcurrent or distance protection. The application of the proposed hybrid protection scheme in conjunction with overcurrent and distance elements is implemented and the benefits of faster protection achieved with the proposed method was demonstrated using case studies. The proposed protection scheme then applied to a large distribution network and verified its reliability.
The proposed hybrid protection scheme can easily be incorporated into existing commercial relays using the transient polarity sensor developed in this thesis. Special protection relays requiring very high frequency sampling rates is not required for the implemented protection scheme. The performance of such implementation was tested using hardware in the loop simulations carried out with the help of an RTDS real time digital simulator.
Description
Keywords
Distribution network protection, Transient based protection, current transient detection
Citation
A. Pathirana, A. Rajapakse, and N. Perera, “Development of a hybrid protection scheme for active distribution systems using polarities of current transients,” Electric Power Systems Research, vol. 152, pp. 377–389, Nov. 2017.
A.N. Pathirana, A. D. Rajapakse, “Enhancing the transient stability of distributed generators with adaptive time-overcurrent protection augmented with transient based unit protection”, International Conference on Power Systems Transients (IPST), Cavtat, Croatia, pp. 15-18, Jun. 2015.
A. Pathirana, C. K. G. Piyadasa, A. D. Rajapakse “Development and modeling of a new type of sensor for detecting current transients for power system protection,” International Journal of Electrical Power and Energy Systems 101, 243-254, 2018.
A. Pathirana, A. Rajapakse, and A. C. Adewole, “Implementation and Testing of a Hybrid Protection Scheme for Active Distribution Network,” in 2018 IEEE Electrical Power and Energy Conference (EPEC), 2018, pp. 1–6.
A.N. Pathirana, A. D. Rajapakse, “Enhancing the transient stability of distributed generators with adaptive time-overcurrent protection augmented with transient based unit protection”, International Conference on Power Systems Transients (IPST), Cavtat, Croatia, pp. 15-18, Jun. 2015.
A. Pathirana, C. K. G. Piyadasa, A. D. Rajapakse “Development and modeling of a new type of sensor for detecting current transients for power system protection,” International Journal of Electrical Power and Energy Systems 101, 243-254, 2018.
A. Pathirana, A. Rajapakse, and A. C. Adewole, “Implementation and Testing of a Hybrid Protection Scheme for Active Distribution Network,” in 2018 IEEE Electrical Power and Energy Conference (EPEC), 2018, pp. 1–6.