How is backup power provided in a substation?

Backup power can be provided by means of a mobile DC power system or through a backup battery bank at the substation. In cases where no backup power is available, an on-line discharge test can be performed. In this type of test, the regular substation load is always connected to the battery during the test and is continuously monitored.

What happens if a battery fails in a substation?

Batteries provide power to the protection and control equipment including relays, circuit breakers and other auxiliary devices. If the battery fails then the substation will be left unprotected. Due to the criticality of the batteries for protection, NERC has laid out requirements on maintaining and testing the stationary batteries.

What is a battery discharge test?

Among all the tests, the discharge test (also known as load test or capacity test) is the only test that can accurately measure the true capacity of a battery system and in turn determine the state of health of batteries.

Can a battery pause be counted in a discharge test?

Only one pause is allowed for the duration of the test and the pause time should not be counted in the total discharge time2. Once the test is completed, determine the battery capacity. The test equipment can then be disconnected. While performing the discharge test, one should be prepared to bypass weak cells approaching polarity reversal.

How is power dissipated during a battery test?

In any case, no matter how big the load is, power is dissipated in the instrument as heat during the test. Care should be taken to direct the heat dissipation away from the batteries and/or properly ventilate the area to avoid heating the room or batteries while testing.

What is an example of a low voltage substation?

Some systems at the substation may require lower voltages as their auxiliary supply source. A typical example of these systems would be the optical telecommunication devices or the power line carrier (PLC) equipment, which normally requires 48 V.