Utility reliability is an important measure of the availability of electrical supply to electrical consumers.
Targets are set for the reliability performance of the utility. The targets are based on measurement of the reliability performance against benchmark values set by the regulating authority. The reliability performance is broken down into areas, substations and feeders.
The utility will identify where the reliability performance is not satisfactory and will develop a strategy and policies to improve the performance. Worst performing feeders are identified and reliability improvement plans developed for each feeder. The plan may involve a combination of capital expenditure and operating or maintenance programmes. There are methods which are used to calculate the economic justification of the reliability improvement. The economic values considered include present worth value, benefit cost ratio and payback. The cost of penalties imposed by the regulator for unsatisfactory performance are also considered.
Utility reliability is measured using industry standard indices. Commonly used indices are:
The calculation of the indices for reliability performance requires the collection and recording of the applicable data. The quality of the data is important for accurate calculation of the indices.
One method which is used to improve the reliability performance is to develop self-healing networks. The concept of the self-healing network is that automation is deployed to allow a portion of the network to recover from an unscheduled outage, while isolating only the circuit associated with the outage. In this way the number of consumers affected can be minimised.
In the same way, self-healing circuits may be used in micro-grids. The development of the self-healing design starts with identifying target reliability indices. The design of the micro-grid can then be modelled for reliability and areas of unsatisfactory performance may be identified. Remedial strategies can be developed and the economic value of the strategies can be estimated.
BESST Engineering is able to model the micro-grid, develop reliability indices and to design reliability improvement strategies, such as self-healing networks. BESST Engineering can assist in the economic valuation of the strategies.