Measurements for Adaptive Protection and Control in a Competitive Market

In a competitive market where generating companies compete for loads with open access to the transmission network, the protection and control techniques in use take on a special significance. In this new environment there are two issues which are related to the uses of real-time measurements. First, there is the possibility that the preset control and protection decisions do not necessarily perform optimally when the System State changes, in particular as the generation pattern changes significantly. The real-time measurements can be of great help in adapting the protection and control strategies to the new environment. The second issue deals with the problem of identifying what control processes are at work on the network at any given time. It would be interesting to investigate if precise measurements made on the network in real time could provide definitive assessment of what is happening on the network. The paper will expand on the two ideas described above. 1. Measurement Techniques for Adaptive Protections 1.1 Adaptive Protection Principles Protection system performance considerations are of paramount importance in discussing the operational security of a power network. It has been documented that a majority of major system disturbances (brown-outs, black-outs) are a result of sequential operation of protective equipment in an unanticipated manner [1]. The normal practice is to set the protection systems based upon certain assumed conditions in the power network. As is often the case, the assumed conditions do not always obtain in practice, and indeed very often the networks reach a state which was never anticipated in the planning studies. Add to this the fact that protection systems may go out of calibration, wear out, or develop hidden failures. Considering the very large number of protection systems which actually exist on the power network, it is then not surprising that occasionally unanticipated trips of power equipment are caused by the protection system. When such trips occur while the power system is stressed, major disruption of the power system are the result. It is of course not possible to guarantee that there will never be mis-operations of the protection systems. However, one cause of mis-operations, viz. the protection s b ‘