Gas Discharge tube based mains transient protector......upstream of mains fuse?

[betwixt]

You are looking at a completely different scenario. The article mentions high speed data lines and the need to use a GDT to minimize capacitive loading, not very low impedance power lines. The schematic also shown the current clamping to "AGND0" which to most would suggest an analog or 'clean' ground rather than one side of the AC line.

Try an experiment, it's something I developed as a student project years ago, it will safely identify spikes large enough to trigger the GDT:
1. Use a wire ended neon indicator lamp. Wrap as many turns of fine wire around the glass as possible. Keep it away from the lamps wires.
2. Connect it in series with a fixed resistor or MOV to simulate the circuit you propose.
3. Connect the ends of the coil wire to an oscilloscope and set it to trigger in single shot mode.

The neon has similar characteristics to a GDT except perhaps a lower ignition voltage but it is typically still > 100V. As it ignites the current through the gas will create a small magnetic field which the coil will convert to a voltage. It will allow you to see the discharge and hence get some idea of how it behaves differently in alternative configurations while maintaining complete voltaic isolation and safety.

Brian.

 

[treez]

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Also, regarding MOVs connected from Line to ground, is it standard practice to put GDT’s in series with these? –The reason being to prevent the leakage current from the MOVs from tripping the RCDs.
….Not only this, but when a company does a LINE/NEUTRAL to Earth insulation test (say on a streetlight product), the test fails if the MOVs to earth don’t have GDTs in series with them.
So do you agree that GDT’s are needed in series with the MOVs that are connected from line to earth? (as in the attached schematic).
(As you know,MOVs are needed from Line to ground, and from neutral to ground, in order to quench transients from lightning strikes.)

 

[betwixt]

Personally, I've never seen a GDT used that way. I've used thousands of them in telecoms line protection applications and when very long data lines are used between buildings or sites but never on an AC power line.

I'm not saying it wouldn't work but the ignition voltage would be very unpredictable and could be as high as the combined GDT and MOV rated voltages although intuitively it would be the GDT voltage plus some other voltage depending on leakage current in the MOV.

Brian.

 

[treez]

Mains transient protection with MOV/GDT combination

Hello
Thread one of the following describes using a MOV and GDT in series, across Live to Neutral.

https://www.edaboard.com/showthread...nsient-protector-upstream-of-mains-fuse/page3

In normal cases, (no transients), how much of the mains voltage will be across the MOV, and how much across the GDT.?....ie will it all appear across the GDT because it is higher impedance?