Quantitative Evaluation Of Voltage Sag And Load-Loss Cost Allocation

With the rapid development of science and technology, a number of devices such as micro-processor and electronics which are extraordinarily sensitive to voltage sags have been used widely in industry. The problems caused by voltage sags have attracted more attention all over the word. Therefore, many research works about it have been done. Now, under electricity markets, voltage sags must be quantificationally evaluated. The sag'sevaluation shows the quality and price of power for providers and customers.After the definition of voltage sag, load-loss cost is defined according to its economiceffects on customers. Three indices are given through integrating the CBEMA curves with the customer devices. One is Customer Ratio of Drop (CRD), which characterizes the sate of loads under sags. One is Load Drop Frequency (LDF), showing voltage sag's frequency of one single customer. The other is Load-Loss Cost Index (LLCI) for quantitative evaluation of load-loss cost caused by voltage sags. According to the customers' classification and the LLCI, a method for the load-loss cost calculation is presented. Consequentially, this paper gets load-loss cost of bus and of systems. The objects responsible for the load-loss cost, under electricity markets, are then made clear. A principle of loss apportionment is proposed. It is pointed out that the load-loss cost due to voltage sag should be allocated to both sources and loads themselves. Not power, providers but customers share half of load-loss cost. Based on the relationship of power component between sources and loads, a procedure for allocating a particular load-loss cost to individual sources is proposed. Load-loss cost is allocated to each source by the responsibility to loads. The load-loss cost compensation allocated to individual loads is determined considering the LDF of loads. The example at the end of this paper is a 5-bus system. Simulation results of this system show that the proposed methods are effective. The indices of sag's quantitative evaluation and the methods of load-loss cost allocation provide effective references to the economic analysis on voltage sags under deregulation on power market.