Consideration of surge arresters for low voltage mains applications
Date
2012-02-14
Authors
Michalopoulos, Aristidis
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Abstract
The work presented in this report details the background to surge arresters
and surge protective device components, viz., spark gaps, gas discharge
tubes and metal oxide varistors. Current surge protective device technologies
are detailed for several of the larger surge protective device manufacturers
worldwide. Tests were performed using both 8/20 μs and 10/350 μs current
impulses to verify the voltage and current response of gas discharge tubes
with or without series MOVs and triggering circuits. Measurements obtained
from the test setup were compared against each other, sharing a total impulse
current of 35.8 kA peak using an 8/20 μs waveform and 10.2 kA peak using a
10/350 μs current impulse waveform. In the work presented, it is shown that
series varistors dampened any voltage and current oscillatory behaviour
superimposed from the current impulse generator due to their voltage
clamping properties, which similarly do not allow any follow current to flow
after a surge has subsided. No effect was seen by using a single varistor or a
many parallel mounted varistors in series with a gas discharge tube. By using
three electrode gas discharge tubes with a triggering circuit, the clamping
voltage was reduced, as the gas tubes reacted faster than an equivalent
circuit without a triggering module, which has the advantage of reducing the
protection level for the protected equipment.