Assessment of component criticality in customer delivery systems

The customer delivery system (CDS) is defined as the component of the bulk transmission system which delivers power from the bulk transmission system to large municipalities, large industrial customers and the retail (distribution) system. The delivery system can be simple or complicated and redundancy may or may not be provided depending on the size of the load and the needs of customers connected to the system. The CDS is made up of different components such as lines, transformers, buses, breakers, etc. and these components are electrically connected together to transport electrical energy from the bulk transmission system to various load points. Depending on system planning criteria used, a single component failure may or may not affect the reliability of supply to customers. All components of the system are important and some components are more critical than others. In a competitive electricity market, owners of these systems are required by regulatory rules to maintain their systems to specific performance standards. Meeting these standards could be a challenging task for transmission owners or providers particularly if they want to maintain a good investment rate of return for their shareholders. One approach of tackling this problem is to rank components of the system in terms of their importance or criticality with respect to supply reliability. Such a ranking list can be used for various planning, operational and maintenance purposes. One of the more important purposes is to establish the most effective areas of the system to invest in to meet reliability targets. In this way, money could be spent in a more effective and efficient way on various projects. The purpose of this paper is to describe the recent study that has been performed at Hydro One to assess the component criticality in the CDS and to show how the study findings can be used in supporting investment decisions.