IEC 62932-2-2:2020 pdf download – Flow battery energy systems for stationary applications – Part 2-2: Safety requirements.
5 Safety requirements and protective measures 5.1 General Each secondary battery has a different structure and therefore only the features critical or specific to the flow battery shall be taken into consideration. The flow battery energy system as shown in Figure 1 differs from other secondary batteries, in that a system for circulating the electrolyte is present. The fluid circulating system consists of tanks, pumps, piping, sensors and some safety-relevant devices. From a chemical safety point of view, since fluid is contained in tanks, pipes and stacks, the sealing is an important factor. There is also the possibility of hazardous gases being present, requiring that appropriate countermeasures be implemented. Clause 5 specifies the safety requirements and protective measures in consideration of the above-mentioned aspects. 5.2 Risk information The manufacturer shall provide the user with risk information based on the risk analysis to describe hazards and the appropriate measures taken or to be taken for mitigation purposes. The information shall include a safety data sheet (SDS). The information can be provided in the form of a user manual. See the recommended structure for user manual in Annex A.
5.3 Electrical hazards 5.3.1 Electrical shock The FBS is an electrical energy storage device and contains hazardous live parts of DC and/or AC voltage which can cause a risk of electrical shock. Electrolyte is to be considered as carrying dangerous voltages. Batteries are sources of dangerous voltages and energy (current flow) also when they are not connected to an external power circuit. In flow batteries the amount of residual energy is, when no electrolyte circulates, limited to the charge stored in the electrolyte remaining in the stack itself. In all cases protective measures according to IEC 60364-4-41 shall be implemented. 5.3.2 Short-circuits The electrical energy stored in an FBS can be released in an inadvertent and uncontrolled manner due to short-circuiting the terminals. Because of its considerable level of energy and subsequent high current, the heat generated can melt metal, produce sparks, cause explosion, or vaporize fluid. To avoid short-circuits, protective devices such as insulation shrouds, fuses and circuit breakers shall be installed in a way that a short-circuit does not occur under any foreseeable conditions. For the type of conductor arrangement of unprotected sections, IEC 60364-4-43 shall be taken into consideration. For protective measures, the FBS shall mitigate a short-circuit fault which occurs outside stacks by: – stopping the supply of energy and fluids to the flow battery cells; – stopping PCS and opening circuit breaker(s); and, – interrupting the short-circuit current path by using fuses between stacks.
5.3.3 Leakage currents In a system in which no point of the battery installation is directly connected to earth, ground faults in the FBS are, due to the large amount of fluid in the fluid handling parts (pumps, pipes, stacks, tanks), a particular problem, and system operators shall be well informed of this matter. Ground faults can cause the following significant risks: – electrocution when a person accesses the fluid leaking from piping, cells and/or other components of the fluid system; NOTE 1 In this case a person’s body becomes a part of the circuit of the leakage current. – arcs and fire when short-current is established by the fluid leaking from piping, cells and/or other components of the fluid system. NOTE 2 The criticality of arcs and fire depend on the electrical conductivity of the fluid. If the fluid has low electrical conductivity, leakage current is small and severity of the risk is low. This also depends on the configuration of stacks. Thus, the detection level is designed taking dangerous leakage current level into account. The circuit of the FBS shall be properly insulated from other local conductive parts. The minimum insulation resistance between the battery circuit and other local conductive parts shall meet the requirements of IEC 62485-2:201 0, 6.4. The minimum insulation resistance between them shall be greater than 1 00 Ω per volt of the nominal voltage of the FBS. The insulation shall resist the environmental effects of temperature, dampness, dust, gases, steam, and mechanical stress.