The work presented in this report details the background to surge arrestersudand surge protective device components, viz., spark gaps, gas dischargeudtubes and metal oxide varistors. Current surge protective device technologiesudare detailed for several of the larger surge protective device manufacturersudworldwide. Tests were performed using both 8/20 μs and 10/350 μs currentudimpulses to verify the voltage and current response of gas discharge tubesudwith or without series MOVs and triggering circuits. Measurements obtainedudfrom the test setup were compared against each other, sharing a total impulseudcurrent of 35.8 kA peak using an 8/20 μs waveform and 10.2 kA peak using aud10/350 μs current impulse waveform. In the work presented, it is shown thatudseries varistors dampened any voltage and current oscillatory behaviourudsuperimposed from the current impulse generator due to their voltageudclamping properties, which similarly do not allow any follow current to flowudafter a surge has subsided. No effect was seen by using a single varistor or audmany parallel mounted varistors in series with a gas discharge tube. By usingudthree electrode gas discharge tubes with a triggering circuit, the clampingudvoltage was reduced, as the gas tubes reacted faster than an equivalentudcircuit without a triggering module, which has the advantage of reducing theudprotection level for the protected equipment.
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