SAFE DISCONNECTION – EXPIERIENCE IN THE FIELD WITH ELECTROMECHANICAL DC SWITCHES AND AN ALTERNATIVE SOLUTION IN PV SYSTEMS

摘要

In most countries DC switches are required by standards [1], [2] or at least common for maintenanceand service. Electromechanic DC switches are reliable and long-term proofed devices. They fulfil safety requirementsby covering the specification for safe disconnection. In PV plants the conditions for components are often veryspecific. In case of DC switches some of them are critical for electromechanical switches. E.g. the wide range ofcurrent and voltages is not easy to handle for these devices. Further the “non-switching” in PV plants – often longerthan 10 or 15 years – is really a challenge for this kind of components. Failures of electromechanical switches in PVplants have been observed (Fig. 1). The motivation of the work is to show, what PV-specific conditions may causeproblems and how alternative systems handle these effects.