Parallel Operation for 11 kV Ring System with Normally Open Point at Distribution Networks in AADC

Abstract

Currently, Al Ain Distribution Company (AADC) 11 kV distribution circuits are electrically split by Normal Open Points (NOP)s. NOPs can be closed for load restoration in case of planned or unplanned outages. Also, changing the NOP locations helps in load shifting to achieve network optimization between adjacently located 33/11 kV primary substations. This paper discusses a new operation mode in medium voltage distribution power network of AADC at Al Ain area in the United Arab Emirates by introducing closed loops of parallel 11 kV feeders from different busbars or substations. This operation mode is intended to end the continuous debate of optimal NOP locations in addition to expected reduction in the required time for load restoration in case of failures at distribution (11/0.4 kV) substations. A detailed case study is performed to explore the achieved benefits and enhancements on load balancing, voltage profile, and power factor in medium voltage networks. On the other hand, the impact on load flow, protection scheme, and loading violation are evaluated. Furthermore, the proposed model is in line with the regulations of the Department of Energy (DoE), regulatory body in Abu Dhabi Emirate, and should fully comply with Electricity Distribution Code (EDC) of Security of Supply Standards. Accordingly, while the current used operation mode is still valid, it is found that closed loops arrangement can be only allowed for rings from same 33/11 kV substations feeding from same source with considerable protection limitations. Moreover, it was concluded that closed loops from different 33/11 kV Substations will result in load flow problems.