Developments towards HV substations without disconnector switches and with modern control systems

In open-air high-voltage substations, disconnector switches are applied to ensure personnel safety during maintenance of circuit breakers. However, disconnector switch maintenance has become significant in comparison to circuit breaker maintenance. Therefore, a study has been performed to investigate the consequences of leaving out the circuit breakers from a substation; this would result in significant cost reductions. The results of the analysis shows that, if certain precautions are taken, personnel safety of a substation without disconnecters is comparable to that of a substation with disconnectors. Next, a new medium-size 110 kV substation had to be realised. It was decided to omit the line disconnecters, i.e. the disconnector switches between circuit breakers and the line connection. A modern SMS (substation management system) has been used with distributed interfacing on primary equipment level. Optimal serial communication between SMS and protection equipment leads to savings on cabling and measurement equipment. The savings on secondary equipment are about 25% and on primary equipment about 10%. In future the expected savings on a substation without disconnector switches are up to 20% of the total life-cycle cost