testing an extension lead with surge protection

[lish70]

Just been doing some testing today including 6 brand new extension leads, first two tested ok 3rd one failed with low insulation resistance of around 0.250m ohms. It was then i noticed that this one had surge protection. Can anyone please explain why this would cause these results and how to get around it.

Many thanks

 

[entech]

hi, does your tester have a 250v dc option. if so use that as the 500 setting will always fail on surge protected extn leads.

 

[Adam W]

:iagree:

 

[platty1005]

SPD's have an internal electronic filter circuit to protect the applinces plugged in hence the poor reading . BS7671 states the Test Voltage for SPD's can be reduced to 250V DC but the pass is still above 1Megohm

 

[lish70]

Thanks guys all sorted now. All makes perfect sense. Still trying to get to grips with my Metrel MI3304 (wish i'd got something smaller!). I've now worked out how to test with the 240v dc )