Surge Protective Device

An SPD that has failed is not automatically a bad device. Most surge protection devices are sacrificial by design: they absorb surge energy, give up a little of their capacity each time, and eventually reach a condition in which they can no longer clamp anything useful and must come out of service. Ask why does […]

Ask when should an SPD be replaced and most answers stop at the status window. That is one input, and on its own a weak one: it shows that a device has reached end of life, never that a device is still fit for service. An SPD can be electrically exhausted while the window still […]

Why a solar combiner box needs both a DC MCB and a DC SPD: the division of labour between overcurrent and transient overvoltage protection, why neither device can substitute for the other, how they coordinate on the DC bus including the SPD backup protection requirement, and how the pairing changes between 1000 V DC and 1500 V DC systems.

A datasheet tells you what a device can do. An SPD specification sheet tells a supplier what you need — and it decides whether the quotes you receive can be compared at all. Enquire with a part number or two lines of description and you will get prices built on different assumptions: different protection levels, […]

Solar DC protection is a chain, not a purchase. In one array you can have a reverse current from nine healthy strings into one faulted string, a lightning-induced impulse arriving on the same conductors, and a maintenance team that needs to work on the inverter DC input — three problems that share a cable and […]

Follow a DC surge protection circuit through normal operation, a surge and recovery, and see why protection modes and DC fault disconnection need their own design.