Large battery storage devices are a crucial technology for storing energy from renewable sources such as solar or wind power. They play a central role, particularly on an industrial scale and for grid-supporting applications. But as capacitances increase, so do the challenges: How can electrical safety be guaranteed? How can errors be detected and avoided at an early stage?
This article focuses on the challenges and safety requirements for large-scale battery storage solutions that are used in combination with large-scale PV installations or wind farms as grid-serving memory.
One of the biggest challenges with large battery storage devices is the early identification and localisation of electrical errors. Earth faults in particular can have serious consequences - from system downtimes to fires.
In unearthed IT systems, a first earth fault does not immediately lead to a failure, as no residual current can flow. Important: this occurrence of a first fault is the signal for immediate action. If the error remains undetected, the risk of a second error increases over time, which in turn increases the risk of a short-circuit.
In earthed TN or TT systems, on the other hand, a residual current flows immediately in the event of a fault, which causes a rapid protective shutdown and thus inevitably leads to operational failures.
In practice, the chosen power supply system depends on the system architecture and the respective safety requirements. While unearthed IT systems are technically possible in certain applications such as renewable energies with galvanic separation (transformer), many battery storage systems - especially in industrial applications - are operated as earthed systems (TN/TT). This applies in particular if a direct network connection is made without galvanic separation.
The consequence: The requirements for monitoring technology differ depending on the power supply system - which is why specialised solutions are necessary to detect errors at an early stage and be able to react in a targeted manner. Specifically, this is insulation monitoring (IMD) for unearthed systems and residual current monitoring (RCM) for earthed systems.
If an insulation fault is detected too late, the electrical safety level deteriorates - arcing, fires or dangerous short-circuits can occur. In addition to the direct hazard to people and installations, there are additional negative consequences for grid-connected storage applications: If a memory fails, it can no longer fulfil its system services - such as frequency support or peak load management. This can affect grid stability, especially in phases with high volatility of renewable energy sources.
A proactive monitoring concept - adapted to the respective power supply system - is therefore not only crucial for the reliability of operation, but also for the reliability of supply.
Depending on the application and system configuration, it makes sense to determine which monitoring strategy suits the power supply system as early as the planning phase. It is not only the topology and magnitude of the supply, but also availability, servicing and standard compliance requirements that influence the choice of protection technology. If you plan early, you can avoid retrofitting at a later date - for example by selecting inverters with externally connectable monitoring devices or by using suitable sensors in central DC busbars.
But a lot can also be optimised in existing buildings: Modern insulation and residual current monitoring systems often have a modular design and can be integrated at a later date - for example via communications interfaces to the control technology or via remote maintenance. This not only enables continuous condition assessment, but ideally also significantly reduces unplanned idle states and maintenance costs. Transparent monitoring is a real efficiency lever, especially for growing storage farms or heterogeneous system landscapes.
Whether a large-scale PV installation, storage farm or industrial application - the reliability of operation and efficiency of large energy logs depends largely on a suitable safeguard and monitoring concept.
The choice of the right protection technology adapted to the power supply system (IT or TN/TT) plays a central role here.
Proactive monitoring reduces idle states, lowers maintenance costs and increases overall availability.
Reality shows: Different applications require differentiated solutions - and this is precisely where the key to reliable energy storage lies.
