I think its AS2760 that outlines the reasons and procedures for testing portable and fixed electrical appliances (its been a long time).

In essence it says that all class one (earthed) appliances need at least 1,000,000 ohms resistance between active, neutral and the earth of an appliance and less than one ohm earth continuity.

Class two (double insulated) appliances need only comply with the insulation resistance as there is no earth wire.

OK. To date these have been rules set out for safe workplaces and some astute home makers, however I have been in a caravan park that insisted on tagging BEFORE you hook up to the power!! I explained to the manager that I was licenced and all my appliances had been tested and were in date OR less than 12 months old (as per the standard) but he insisted that he do the checks, when I asked him by what standard he was testing he couldnt quote the standard and when I asked him to show me his megger he produced a multimeter. I went on to another park and dobbed him into the OTR (office of the technical regulator).

Folks, I am very anal when it comes to electrical safety, so all my appliances get a yearly check. It is not only checked for the electrical properties, the test looks at condition of the appliance, cord condition and entry, and lastly operation of the appliance.

I am not going to preach that we should all get our appliances tagged, however for peace of mind its not a bad idea. I remember purchasing a cheap power board from Bunnings many years ago, just out of curiosity I did the checks and it failed on insulation resistance, it seems somebody spilled coffee all over the block, cleaned it up and put it back on display. When I bought this to the managers attention he asked me to check a few more on the pallet, 2 others failed (seems the coffee spread out a bit). He was very grateful and gave me staff discount every time I purchased from that store.

Lesson here is dont take it for granted that all new electrical gizmos are safe, if they make funny smells or spark and arc when plugged in, take them back for a refund.

There are a number of technical colleges and TAFE where you can do a one day course to "licence" you to carry out these tests, it is worth remembering that a megger (the meter that produces the 500V necessary for testing the insulation) costs about $300 for a manual meter and must be calibrated yearly. It is a good hobby income for me and gives me the satisfaction in seeing my fellow caravaners are safe.

Safe travels