As per the subject, really.
The symptom I have is that sometimes, my central consumer unit's RCD/GFE will _sometimes_ trip when I turn on some older test equipment. Anecdotally, it does seem to be humidity related, for example if it's foggy outside.
This started happening since I moved from an apartment in the the city to a rural house, and this is the first time I've encountered it with this TE. I've had both units for ~20 years.
The TE is an HP 8753A VNA and an HP 8565A spec an.
I tried measuring the leakage at the consumer unit using a UT210E clamp meter simultaneously around both Live & Neutral, that has a resolution down to 10s of mA, but it was inconclusive, as it proved difficult to get a stable reading.
I measured the DC resistance on the two appliances, and it's up in the 10s of megohms. They do have Y caps of the order of single digit nF that I can measure.
I do have an inline RCD, but its trip current is the same as the consumer unit's central RCD.
It's kinda difficult to measure when the circuit trips.
So my question is, how best can I measure earth leakage of an appliance out of circuit? Does a PAT tester measure AC impedance for example, or is it just DC resistance?
I have both a variac and an isolation transformer if that's any good.