Battery systems are used in substations to close and trip high voltage circuit breakers, for transformer protection and safe isolation during normal or fault conditions.

The application requires a high reliability system as energy transmission and distribution is required at all times and cannot move into a situation of unavailability. The application often has a mixed load duty cycle with low level continuous loads and short peak loads for switching operations. Clearly, the battery type must be optimized for the loads and often high performance products are used for solenoid-actuated switch gear and medium to long rate products for spring-actuated switch gear.

Since the battery protects expensive transformers, reliability is foremost in its required attributes. In addition a long life is required as the typical substation life is over 25 years and low maintenance helps to minimise the life cycle cost. Since smaller distribution substations have more extreme temperatures, the ability to function over a wide temperature range is essential.