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Surge protection - monitoring effectiveness.

whjohnson
Ok, so folk are all going mad and fitting SPD consumer units et al.

BUT - How effective will they actually be?

In other words, what steps are in place to monitor and record the effectiveness of these devices?

So the flag turns from green to red over time, yet the consumer unit continues to deliver regardless, and the customer notices nothing changing, in the same way that they never test RCDs by using the test button.

How will we ever know whether or not these devices are actually worth the money? Or is it a case of another successful snake oil sale?

How long will it be before a future EICR flags up the fact that the SPD has 'died'.?
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    While I do not want to get into the politics of what should be in the wiring regs. (this time)

     

    How do these things mitigate a surge when an isolation transformer is in cct? Surely the rise in energy in the primary is replicated to a degree in the secondary depending upon the turns ration? If this is the case, then surely there is still risk of damage to any electronics downstream?

    How about the effects upon a step-up transfomer too?




    Not really as you might have expected - the surge waveforms are very very short duration compared to the 50Hz mains cycle, and the magnetic core of a conventional power transformer is nothing like fast enough to respond (running out of steam somewhere in the high frequeny audio to ultrasonic regime depending on size), so it is as if the core is replaced with air. Also the capacitance between windings is far more significant than it would be for low frequency events, so really the magnetic coupling between the windings is more or less switched off, and the trasnformation ratio is more to do with the capacitance ratio on both sides, in the manner of an oscilloscope probe or a graded insulator.



    (the capacitive voltage divider concept is illustrated in this article about scope probes) realise in a transformer it will not be anything like that simple, as the winding capacitance of the outgoing cables is very much distributed and may be better seen as sections of transmission line of varying impedances.




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  • 0
    While I do not want to get into the politics of what should be in the wiring regs. (this time)

     

    How do these things mitigate a surge when an isolation transformer is in cct? Surely the rise in energy in the primary is replicated to a degree in the secondary depending upon the turns ration? If this is the case, then surely there is still risk of damage to any electronics downstream?

    How about the effects upon a step-up transfomer too?




    Not really as you might have expected - the surge waveforms are very very short duration compared to the 50Hz mains cycle, and the magnetic core of a conventional power transformer is nothing like fast enough to respond (running out of steam somewhere in the high frequeny audio to ultrasonic regime depending on size), so it is as if the core is replaced with air. Also the capacitance between windings is far more significant than it would be for low frequency events, so really the magnetic coupling between the windings is more or less switched off, and the trasnformation ratio is more to do with the capacitance ratio on both sides, in the manner of an oscilloscope probe or a graded insulator.



    (the capacitive voltage divider concept is illustrated in this article about scope probes) realise in a transformer it will not be anything like that simple, as the winding capacitance of the outgoing cables is very much distributed and may be better seen as sections of transmission line of varying impedances.




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