Battery Energy Storage Systems (BESS) are rechargeable battery systems that store energy to be used at a later time. During the day, clean solar energy is used to charge the battery storage system. These systems are typically used to cover peak load coverage and provide grid stabilization.
There are two types of grounding that are currently being used with BESS.
A solidly grounded system has one conductor tied to ground intentionally, which serves as the return path for current during a ground fault. A single ground fault on a grounded system will generate high amounts of ground fault current, which is why the BESS must be robust and resilient. This high current will either shut the system down or cause system failure, most commonly via a fire.
The ungrounded system does not have any conductors tied to ground, henceforth there is no return path for current during a first fault. The BESS can continue to safely operate during a first fault in an ungrounded system.
Although the system can continue to run during a first fault, it is vital that the fault is cleared as quickly as possible. If a second fault were to develop on the opposing conductor, a phase to phase or line to line short would be created through ground.
Imagine a scenario in which one fault has developed and there is a high ohmic fault on the opposing phase. This may not generate enough current to trip over current protection, however, it can generate enough power to cause a fire. Unfortunately, this exact situation is not just theoretical, it has happened in numerous solar and BESS installations.