Protection of the Next Generation of Power Distribution Systems

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Driven by the smart grid and green energy initiatives, new features and technologies are proliferating across the legacy power system. This research program will respond to the rising protective relaying challenges imposed by these emerging developments, thus ensuring the fault resiliency and reliability of next-generation power systems. In the short term, the focus will be on distribution systems, and the following issues will be researched. 1. Microgrid protection: Even though existing distribution relays fail to reliably protect microgrids, no microgrid-specific relay has been manufactured to date. To address this gap, a microgrid relay will be developed by investigating the unconventional sequence components, waveshape properties and magnitude of the fault currents and voltages of distributed generation (DG) units. The main protection units of a relay are controlled by a number of supervising elements, which are critical to successful relay operation. Two relay supervising elements that can be affected in a microgrid will be researched. 2. Photovoltaic (PV) farm protection: Solar PV is a common technology in the DGs connected to distribution systems. PV farms sustain heavy losses due to internal faults. Moreover, malfunction of the existing PV farm protective devices have recently resulted in several fire incidents. This program will develop PV farm protection methods based on correlation analysis of string current waveshapes and string voltage distribution. 3. Phasor measurement for distribution systems: Wide-area measurement systems (WAMS) are being extended to distribution systems, where the voltages and currents include higher levels of pollution. On the other hand, more-precise measurements are required at the distribution level. This research will integrate demodulators in the phasor measurement algorithms and so help to eliminate the effect of signal pollution. 4. Protection of low-voltage (LV) dc systems: While relay communication can address the protection challenges of LV dc systems, a communication network is hard to justify economically for most LV systems. This research will formulate new relay communication schemes for LV systems, using emerging low-cost wireless technologies such as cellular networks. Then, adaptive protection methods will be developed taking into account the properties of the wireless technology adopted. The improved distribution protection methods developed through this program will be essential to (i) realization of microgrids, (ii) higher penetration of renewable-based DGs, (iii) more-accurate WAMS for distribution systems, and (iv) cost-effective distribution relay communication. Fault resilient and sustainable operation of next-generation Canadian distribution utilities are among the contributions of the above projects. Other beneficiaries of this program include relay manufacturers and the solar PV industry.