Insulation Testing during a condition report/periodic test.

I'd be wary of that - the RCD might not trip, even with 29mA of leakage (though real ones usually have thresholds in the low to mid 20mAs) That could represent  a touch under 10k ohms  - which if it is concentrated at a single point is probably quite a serious fault and worthy of investigation. A DC test actually checks the insulation, and is not fooled by capacitance. An RCD 'headroom' test alone cannot distinguish between a dead mouse glowing on the wire resistivity  and a problem, or several nano-farads of capacitance L-E from a long and meandering installation in perfect health, or a room of IT equipment with 'Y' c connected filter capacitors on the mains inputs  to tame the worst excesses of the switch mode power supplies. Both capacitive cases are legitimate earth leakage, but the resistive case is not.

That said, a test of L-N leakage with the clamp meter around L and N looking (RCD-like) for the out of balance current is a good confidence check that there will not be RCD false alarms in the future, though I suggest an investigation limit of 10mA on a 30mA RCD

Insulation tests do have merit, especially on wiring that is either brand new (looking for nails in the wire from the new skirting board or whatever) or in poor condition ( post flooding or buildings with suspect rodent issues come to mind as special cases).
Mike.

I am reminded of the sad Emma Shaw case, where an insulation resistance test would not have picked up a serious fault, but an R.C.D. may have saved a life.

https://www.dailymail.co.uk/news/article-2077015/Young-mother-electrocuted-mopped-water-leaky-boiler-died-catalogue-workmens-errors.html

And...........

www2.theiet.org/.../messageview.cfm

Z.

I am reminded of the sad Emma Shaw case, where an insulation resistance test would not have picked up a serious fault, but an R.C.D. may have saved a life.

https://www.dailymail.co.uk/news/article-2077015/Young-mother-electrocuted-mopped-water-leaky-boiler-died-catalogue-workmens-errors.html

And...........

www2.theiet.org/.../messageview.cfm

Z.