APTP Articles

Standby Battery Installations Provide Electricity to Key Elements of Power Generation

Standby battery installations provide electricity to key elements of power generation, transmission and distribution systems, such as circuit breakers and protective relays, computers, control panels and telecommunication equipment, when other power sources have failed.

The batteries can provide power instantly, either directly as DC or via an inverter as AC, thereby ensuring that critical systems continue to operate until emergency generators are ready to take over, or the main electricity supply is restored.

In some instances, the batteries may also be required to support “black start capability” for a power station. This capability is provided for selected power stations to enable them to start operating after a national power cut without relying on power from the external transmission network. Once the power stations with black start capability have resumed operation, they can supply other power stations with energy so that they can also restart. Black start capability is therefore essential for the security of the country’s power supplies.

As batteries play such an important role, it is essential for battery systems to be planned, installed and monitored in line with relevant standards, such as European Standard EN 50272-2, which corresponds with German Standard VDE0510. Battery capacity must be calculated from the number of users that need battery power, and the amount of power each user requires. Power station operators must also provide evidence that the emergency power systems can support essential functions in case of emergency.

Battery Capacity

A battery must be capable of continuously supplying electricity over a specified period of time. This ability is defined as its capacity and is calculated by multiplying current supplied by time, with the result expressed in amp hours (Ah). Battery manufacturers specify the nominal capacity of their products, but this does not always correspond with reality. Even when they are new, for example, batteries must be charged for a time before they reach their maximum capacity. And over the working life of a battery, its capacity can be expected to decrease significantly as it ages, until it eventually reaches the point where it is unable to supply power for the period originally intended.

Under favourable conditions, a battery can have a service life of 20 years, but this is the exception rather than the rule. Batteries store energy chemically, and the efficiency of the chemical processes can deteriorate rapidly if the battery is poorly managed and maintained. Insufficient charge, uneven load levels, corroded clamping bolts or internal connections, unfavourable ambient temperatures and bad ventilation can all rapidly and drastically reduce the life of a battery. 

Furthermore, it’s important to remember that a battery is made up of a number of cells connected in series. A single defective cell can prevent the whole battery from working correctly, possibly shutting down an entire facility, causing the whole of a city district to be without power, or allowing industrial processes to collapse. A battery installation is only as good as its weakest cell.

Niclas Wetterstrand - Program Manager Megger Sweden