What would SEN argue is a reasonable surge arrester specification for defence against lightning strike?
Defence against lightning needs to incorporate surge arresters, devices that filter out big voltage and current spikes, as well as keeping strong frequencies at bay. Talk to suppliers about best specifications for use in your area.
You should be looking for devices that give isolation primary to secondary sides, have performance that’s at least 125 per cent of full load capacity. You also want high-speed, leading-edge suppression and a high-energy resistance metal oxide resistor, plus or minus 1 per cent output volts at 85 per cent load with -25 per cent to 15 per cent of nominal input volts.
In addition, you’d need a voltage change on load change of plus or minus 3 per cent for 3 cycles and 95 per cent correction for 2 cycles. Your surge arrestors shouldn’t just be looking after the transformer’s secondary side – add arrestors to the secondary side of sensor wiring as well.
It goes without saying that you should avoid all external wiring and you should bond your system by making physical connection of any walled conduits to system ground. It’s also important to ground the main transformer to a grounding roof or copper earth tape and connection using insulated wire – use a big gauge.
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