John, You may be pleased to know that the Hazard Based Standard that is being developed to replace both IEC 60950-1 and IEC 60065 does not use the term SELV (or PELV) but invents a whole new set of abbreviations.
Of course, within IEC 60950-1 the correct usage of the term is not 'SELV' but 'SELV Circuit'. Also, IEC 60950 was derived in part from IEC 380 which also used the term SELV to refer to a circuit that was safe to touch because it had two methods of protection between hazardous voltage parts and accessible parts, but it did not invent a new name depending on whether the two methods were Basic + Supplementary; or Basic + Connection of the accessible part to PE; or Basic + a protectively earthed interposed screen (with the secondary floating or connected to FE). Hence, these terms have been used this way for over 20 years and in reality they are not going to change in existing standards now. Most of us in the UK know that when an American says "elevator" s/he really means "lift" and many Americans know that when a Brit is talking about a car's "bonnet" they really mean "hood". So it is with the term SELV (Circuit) and PELV. Regards, Richard Hughes Safety Answers Ltd. www.safetyanswers.ltd.uk In a message dated 07/12/2003 18:28:00 GMT Standard Time, ja014d7...@blueyonder.co.uk writes: I fully agree with John W on the SELV/PELV nomenclature - it is a nonsense at the moment. It is very confusing for most people to use the same term (SELV) in different standards to mean different things, and very difficult to explain to someone who doesnt appreciate the considerable differences in construction that generally arise - we should use PELV in all the standards where we actually mean earthed SELV. Regards John Allen
