Relay Engineering Services Limited (RES) is a specialist technology company that develops and markets equipment, solutions and know-how for testing Power Systems Protection relays and associated systems.

Within this highly focused and complex field we have built up unrivalled expertise and technical competence. This experience is employed to deliver some truly advanced and rugged products, combining software-based control with the very latest electronics technology available.

We are the UK market leaders in this field and prime supplier to all the UK electricity generation and distribution companies. Our products are time proven and in constant use in over 30 countries by customers in the electrical supply, distribution, research and development, railway and industrial sectors.

Product Background

Every high voltage circuit, generator, motor and transformer operating on electricity networks, railways and industrial installations throughout the world is protected by some form of protection relay. These sophisticated devices must operate correctly at all times to disconnect a faulty or overloaded circuit. Furthermore, for the whole protection system to operate, a backup uninterruptible supply must also be constantly available from a standby battery.

To ensure the safe and reliable operation of these networks, every element of their protection system needs to be regularly tested in a consistent, efficient and traceable fashion. RES protection test sets are designed to provide the speed and accuracy required to achieve this in an intuitive and self-documenting fashion.

Our relay and battery testing products are all completely software controlled from a standard PC/laptop utilising the familiar Windows® environment. Unlike other products, our test sets are designed to offer exceptional application coverage and test the widest range of relays without the need for any additional accessories or optional software modules. Additionally, the use of sophisticated power electronics technology enables us to offer exceptionally powerful voltage and current output capabilities together with class-leading power-to-weight ratios.

Company History

Relay Engineering Services was formed in 1987 to bring to a wider market the APTS protection relay test set. This test set was already the standard equipment and in extensive use by what is now the UK's National Grid Company. It was developed by RES's founder in 1983 whilst working for NGC as a Protection Engineer. It was then the world's first portable computerised protection relay test set.

Since then RES has developed and brought to market many more test sets, including sets for testing standby batteries, energy meters, circuit breakers and a complex power systems simulator. The new APTS test set, now completely revised with the most up-to-date technology and designed with over a decade of experience in the field remains the company's flagship product. Capable of testing virtually every relay in existence today and in the future, it is the instrument of choice for protection systems professionals.

RES is now the UK's market leader in this niche field. Our test sets are now standard equipment within most UK generating, railway and regional electricity companies.

Internationally we have also made substantial inroads and today an ever expanding network of sales and support representatives is in place to service customers worldwide.