The project addresses issues related to charge development of GIS spacers, lubrication, grading capacitor condition, bus transfer capability and Frame R maintenance.
Objectives
The following projects address issues relating to the condition and life extension of substation equipment:
Lubrication and maintenance: The study will cover the problems associated with ageing of lubricants, environmental impacts and material / lubricant interference. By using theoretical and practical application and testing, all modern and development products will be considered. It is proposed to use a University to carry out this research as they will provide the level of independence required, will study the latest products available from the major manufacturers and will also be able to consider the latest developments that may not be marketed yet.
Internal examination of circuit-breaker voltage grading capacitors removed from service has revealed incipient faults that would certainly have lead to failure but which were not revealed by existing diagnostic checks. The present work is concerned with applying a range of diagnostic techniques to capacitors that have been in service and correlating the indications obtained with the results of internal inspections to identify the techniques most effective in detecting incipient fault conditions. The knowledge obtained will be used to decide whether the capacitors of circuit-breakers undergoing refurbishment are fit for a further 20 years service without risk of disruptive failure or whether they require replacing.
The main technical issues with regard to the second refurbishment of Frame r ABCBs are associated with lubrication of the trip latch and trip valves. The operation of the trip valve is critical. A ‘stuck open’ trip valve (which has occurred in service) can cause severe air loss resulting in flash through of the open interrupters. Slow operation and air loss can also result in a severe reduction in Lightning and Switching Impulse Voltage capability. NG staff have expressed concerns about the performance of the current recommended trip valve lubrication (Molycote FS 3451) because it is separating in service and losing its oils. The trip valve design relies heavily on regular lubrication to maintain it functionality and the current maintenance regime is inadequate to achieve reliable performance from the valve. Research into the design of the valve is required to alleviate this problem allowing current maintenance intervals to be achieved or improved upon.
The effects of bus transfer duty on the Committee design of disconnectors and the possibility of designing a retro-fit solution to give Committee designed disconnectors an on-load bus transfer rating to modern standards will be investigated.
