I have been testing 4 extension leads with RCD plugs installed. On all of them I received high readings for a 30mA trip on both sides of the sine wave (0deg & 180deg). A couple were over 200ms so considered a fail. I became suspicious about this so I tested the same RCD plugs using my Meggar 1720 and had totally different results. With the Megger all were in the <20ms results hence acceptable.
My test setup with the Primetest 250 was :-
Connect portable RCD plug to a power socket
Connect Primetest 250 to extension lead with the mains inlet socket
ie as per the manual
Have I carried out the test incorrectly ?