Risk Assessment for 11kV Unsecured Rings in Distribution Utilities in UAE Based on Probabilistic Approach

摘要

This paper presents an alternative probabilistic approach to address a real concern of distribution utilities where reinforcements with high investments are required to meet a deterministic (N-1) criterion at medium voltage level rings. Currently, unsecured 11kV rings are decided in most Distribution Companies where the total load should not exceed (N-1) criterion at any time of the year. Once the load summation of both sides of the ring crosses the (N-1) the ring is considered unsecured and raised to the network planners for strategic reinforcement plans that require considerable budget and time for implementation. In this paper, a probabilistic approach as a decision-making process for evaluating unsecured 11kV rings is proposed that aims to balance the capital spending and risk of supply interruption. Two main methods (Risk Matrix and Monte Carlo Simulation) are explored and presented in brief to evaluate other possible efforts in moving towards cost-effective evaluation and decision-making. Accordingly, this paper builds a risk assessment matrix for 11kV unsecured rings and presents a model based on historical data for several rings to evaluate the possible risks. A cost comparison with and without reinforcement schemes is discussed. The data is illustrating a real case study based on actual load measurements and real network parameters in one of the distribution utilities in the UAE (the name of the utility is not declared for confidentiality). The final decision-making process shall consider the findings to enhance the security of the supply of unsecured 11 kV rings with minimal spending. Finally, the investment of roof-top PV for a specific unsecured ring along with DSM solution is investigated and considered as a special model for critical unsecured rings that require reinforcement.