ABB has developed a specialist surge arrester retrofit service that enables the transformer circuits in outdoor high voltage substations, typically up to 400 kV, to be upgraded to a high level of protection against the damaging overvoltages created by lightning strikes. The service provides a method for increasing the security and reliability of the substation operation and minimizing interruptions to the power supply delivered to consumers.

The retrofit service uses ABB's well-proven Pexlim surge arresters. These use zinc oxide (ZnO) blocks in a composite silicone rubber housing that is resistant to environmental pollution and vandalism. The material offers high safety levels since it is self-extinguishing and will fail safely rather than explode when overstressed.

In new substation projects, the additional cost and complication of installing surge arresters is relatively small. However, retrofitting surge arresters to existing installations is much more challenging as suitable overhead mounting gantries, typically of a "goalpost" design 20 m high and 21 m in span, have to be transported on site and erected by crane. There may also be a need for additional foundation works and possibly piling.

Tom Smith, ABB project manager responsible for the surge arrester installation service, said: "The ABB surge arrester retrofit service team has refined it skills in 39 installations already completed successfully for UK customers. Having experience of just about every possible permutation enables us to provide a very fast turnaround, with installation usually completed within a week.

"A key aspect of the surge arrester retrofit service is the careful advance planning and coordination we provide to ensure that the installation work tie-ins with planned outages, so that we can minimize potential disruption to the substation operation. And we have developed safe working methods that enable us to carry out a significant proportion of the civil works, even piling for foundations, without having to take an outage."