Heathrow disaster is a reminder to keep HV assets in good shape

It is not our place to speculate on the results of  the inquiry into what caused the catastrophic Heathrow outage on March 21. But the incident is a salutary reminder that grid reliability depends on ensuring that assets are maintained to the highest standard – including legacy HV transformers and tapchangers.

The work of our Ferranti operation is proof that electro-mechanical tapchangers that may have been in services for 60 years or more can be among the most robust and reliable assets on the grid, given the appropriate maintenance and modernisation.

We are uniquely able to support a vast range of tapchangers in more than 30 countries, including Ferranti, Metropolitan Vickers, AEI and English Electric, with service kits, parts, factory manuals, engineering and know-how.

Replace or fix?

As we have written previously, we recently looked at a 1960s 132/11/11kV transformer with a tapchanger that was starting to fail – and engineers braced to spend £2 million for replacement.. 

They were astonished when we told them we had the parts, factory manuals and know-how to restore the tapchanger’s performance to 100% – and doubly amazed when we said that, with basic maintenance, it would last at least another 35-40 years and probably reach its 100th birthday.

Among the advantages of old electro-mechanical units is that many were robustly engineered, with parts such as contacts and switches that are accessible and relatively easy to replace.

Maintain and modernise

In many instances, tapchanger performance can be restored and/or extended with a simple on-site service. For more complicated applications we can bring them from site to our workshop and do a full refurbishment to as-new condition.

Modernisation options include fitting new controller interfaces and communications modules, compliant with the IEC 61850 international standard, so they can be fully integrated with DNO management systems, greatly reducing the need for physical interventions.

They can also be upgraded with other accessories for temperature and moisture monitoring  and control.

So, with basic and regular mechanical maintenance, and various elements of condition monitoring and modernisation, the reliable life expectancy of legacy tapchangers is vastly extendable.