Gareth Magennis wrote:

"Phil Allison" wrote in message
...

bud-- wrote:


As explained in the IEEE surge guide
(starting page 30) plug-in protectors work primarily by limiting the
voltage from each wire to the ground at the protector.

** Connecting MOVs to ground like that in a *plug-in device* is prohibited
on safety grounds under EU and similar regulations as followed in most
230/240 V places - like Australia where I am.

MOVs either have or can develop after some use leakage currents well in
excess of the maximum permitted, which is only a milliamp or so for most
categories of appliances.

The only components that may be so connected are agency approved " Y caps "
with values like 4.7nF - while MOVs and " X caps" always go across the
line.


In the UK you can buy "surge protected" multi outlet extensions like this:
http://www.amazon.co.uk/Sivitec-Swit...rge+protection


Problem is, these can't be tested with a typical PAT Tester, as they fail
the test every time, being as there is circuitry between live and ground.


** Really? You read this somewhere on the net, right?

I bet they CAN be tested, passing all the tests is the issue.

FYI:

A customer, who runs a hire business, brought in his "Megger 4DV" PAT tester recently for a check over - so I got to see exactly what it did and how.

Some tests involved normal AC power being applied to the device, others used high voltage DC and another low voltage AC at high current to check earth conductor resistance.

AC leakage current and insulation resistance are the main things checked - the pass /fail threshold was user adjustable to suit the type of appliance under test. Class 1 and class 2 ( double insulated ) appliances follow different rules.

The operator is also expected to carry out a thorough visual inspection too, so needs to be familiar with electrical appliance safety.

If a new product failed one of the tests, that would be VERY alarming and should be reported to the supplier immediately.



.... Phil