Battery energy storage systems (BESS)

BESS most commonly operate as unearthed systems, which means all line conductors are intentionally isolated from earth. Although these systems can continue to operate with a single earth fault, it is vital to indicate and clear the first fault as quickly as possible. If the fault is not cleared, a second fault develops and a line-to-line short will occur. Bender’s insulation monitoring devices (IMDs) will give advanced notice of a first fault condition which allows for time to properly identify and clear the fault before a catastrophic issue arises. Bender offers a wide range of IMDs for virtually all size BESS, from small-scale deployments to commercial and industrial systems to large-scale, utility grade systems.

Most BESS operate via an unearthed system design, however there are earthed installations that must have proper earth fault protection to operate safely. These systems can be earthed at the + or – pole of the DC (battery) circuit, or at the neutral connection point on the inverter. It is essential to detect gradual insulation deterioration or earth faults by means of residual currents. This allows issues to be detected and cleared at an early stage, before they trip a protection device and/or damage the batteries. Bender’s residual current monitors are able to detect low-level AC and DC earth faults to indicate minor issues before they become major issues, such as equipment fires or system shutdowns.