Battery energy storage capacity for self-consumption according to the required autonomy in transformer substations
K. Deželak Environment and Energy Statistics Section, Statistical Office of the Republic of Slovenia (SURS), Ljubljana (Slovenia) 2026-06-27

Abstract

Batteries and DC power supply in the transformer substation are of essential importance for the timely and correct operation of electrical power systems and for ensuring the safe and reliable operation of devices in the substations. Due to their characteristics and long charging cycles, existing stationary lead-acid batteries (Pb) are currently extremely oversized compared to the expected 12-hour autonomy. With the use of modern protection and control devices, the consumption of DC self-consumption has been greatly reduced in practice. However, the battery capacity should still remain the same, mainly due to the need for a large current load, which may occur with the possible simultaneous operation of a large number of circuit breaker trip coils in the event of a fault in the substation. In addition, the possibility of using Li-ion battery packs is proposed, as this technology has several advantages, such as smaller dimensions and more efficient use of space for installing batteries, the possibility of fast charging, and less sensitivity to temperature and microclimate changes. The article thus presents the selection of some characteristics for Pb and Li-ion batteries under continuous loads for small and large substations. Aforementioned, were performed using battery models in the Matlab software package, with the model previously validated with measurements.

Key words: Battery energy storage, self-consumption, transformer substation.

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