Distributed substation control system with PC based local control

In a departure from traditional substation control design in New Zealand, the new Trans Power 220 kV Ashburton substation makes use of an ICADA (integrated control and data acquisition) system for all control and monitoring functions. The system consists of a Westronic D20 distributed RTU (remote terminal unit) and a PC (personal computer) running RealFlex software as the local operator interface. The D20 input/output modules are located in panels in the control room, in the outdoor junction boxes and in the transformer control cubicles, with the modules being inter-connected via fibre optic cable. The D20 RTU serves as the main interface. For all input and output signals, communicating on separate serial channels with the local PC, with Trans Power´s South Island System Control and with the Area Control Centre in Christchurch. Different sets of data are sent to these locations using two separate protocols. The D20 also executes a PLC program which provides some control and alarm combination logic. The local PC displays substation status on graphic mimic screen diagrams, logs events and alarms to printer and disk, and allows local control of circuit breakers, disconnecters, transformers and related items. The operator interface is designed to be “user friendly” with most actions being carried out by “point and click” using a mouse