Retrofitting 11KV circuit breakers in primary substations

6.6kV/11kV Oil Circuit Breakers of vintage 1950 / 60´s are still operating in many utilities today and potentially represent a very high percentage of the total network population. Originally installed circuit breakers may have become unsuitable for a number of reasons; such as their operational requirements, or their asset condition, or they may have a restricted network duty. This paper outlines a number of cost effective solutions to enable older equipment, that is no longer manufactured, to be retrofitted with a modern design. Furthermore, it considers the experiences of one electrical utility after undertaking a retrofit programme of 1,100 circuit breakers. A standardised approach is promoted to replace the many variants and peripheral designs with just a handful of modern products.