Protection Systems that verify and supervise themselves

This paper highlights some important design aspects that a Protection and Control system should have when applied to protecting a Smart Grid or Smart Transmission & Distribution Substation. These aspects are aimed at de-risking the designs and, at the same time, reducing overall project cost. The electricity industries of many countries currently only put equipment into service following thorough design checks and detailed site commissioning using highly skilled engineering personnel. Such a thorough and detailed approach increases the overall cost of a project. Although best endeavors are made to identify and resolve all errors at the design and site commissioning stages, it is often not practicable to eliminate them all. This situation triggers a need for designs to be of such a nature that those errors, which may have slipped through during the site commissioning, get automatically detected prior to equipment operating on the live system. Manufacturers currently design Intelligent Electronic Devices (IEDs) that supervise themselves only, i.e. there is insufficient capability built into the designs which would allow verification and supervision of the whole of a protection scheme (protection system). The need for better automatic detection of errors necessitates a need to self verify and supervise the protection system as the whole. This need is reinforced when considering how some utilities now prefer to buy whole Secondary Bay Solutions rather than individual relays. Furthermore, there are continuing pressures to reduce circuit outage times and hence the need to complete site commissioning within given timescales is greater than ever before. These tighter timescales clearly point to a greater need for self verification and supervision of a whole protection system. The principles upon which the above verification and supervision techniques could be based are discussed. Protection systems employing these techniques would be Type Approved when they are introd- ced for the commercial use; hence the anticipation is that the overall cost of a project will be reduced due to lower reliance on design checks and commissioning.