Dynamic interlocking for fault-level limiting

The purpose of dynamic interlocking for fault-level limitation is to replace hardwired interlocks with more flexible computer-based systems. An early version of dynamic interlocking was implemented at Drax power station in the UK a number of years ago using a purpose-built microprocessor system, running software with the network model hard-coded into it. This dynamic interlocking system could not be applied to another power system without redesigning both the hardware and software. To overcome the dedicated nature of the first system, a new dynamic interlocking system was built and subsequently installed in Heysham 2 nuclear power station in the UK. The software operates on-line and in real-time. The core software for this new system was general purpose so that it could be applied to any power system. To configure the software for any new network the user has only to enter the appropriate network data through a graphical user interface. The paper describes the core software that was subsequently installed in Heysham 2 nuclear power station, including practical experience of its operation. The work was completed in 1985 and implemented on specialised hardware. Despite this, the core software is even more relevant today than at that time because advances in hardware technology have created the opportunity to construct a universally applicable dynamic interlocking system. The advent of circuit breakers with built-in microprocessor systems and communication interfaces, as well as the power of SCADA systems, has created the opportunity to install dynamic interlocking systems on many plants using the generalised software described here and standard hardware. Such systems have the potential to reduce installation costs, greatly improve the flexibility of plant operation and reduce maintenance costs