Overcurrent Protection in Distribution Systems With Distributed Generation Based on the Real-Time Boundary Wavelet Transform

The protection system has been facing new challenges with the distribution systems with distributed generation (DG), which may be successfully accomplished through the combination of the existing protections, such as overcurrent protection, with modern protections based on emerging technologies. By using conventional and modern protection trends, the aim of this paper is to propose the overcurrent protection based on the boundary discrete wavelet transform. In real time, this transformation decomposes a signal in the boundary scaling and wavelet coefficient energy. Following the conservative trends of power system protection, the instantaneous and time-delay overcurrent elements (phase and neutral units) are reproduced in the wavelet domain by using the boundary scaling coefficient energy, providing similar performance in the fault detection, a faster trip, and less computational burden than the conventional overcurrent protection. Following the modern protection trends, the boundary wavelet coefficient energy provides real-time detection of the fault inception time in order to reduce the relay operating time and minimize the harmful effects of the faults. A distribution system with DG was modeled in a real-time digital simulator, and wavelet-based overcurrent relays were evaluated and compared to conventional overcurrent relays based on the Fourier transform in real-time simulations, and promising results were obtained.