Hi Pete:
It seems to me that there are several kinds of conductive
parts that we need to be concerned about from a safety
perspective:
1. Energized parts at hazardous voltage.
2. Energized parts at non-hazardous voltage.
3. Energized parts at non-hazardous current.
4. Grounded/earthed parts.
5. Non-grounded/earthed parts susceptible of becoming
energized at a hazardous voltage in the event of a
fault.
6. Non-grounded/earthed parts not susceptible of becoming
energized at hazardous voltage in the event of a fault.
For the purpose of these definitions, grounded/earthed is
taken as meaning bonded to the earth.
Non-grounded/earthed is taken as meaning not bonded to the
earth, but may be incidentally connected to earth (i.e.,
not connected to earth in a manner that assures a current-
carrying capability).
Each of the preceding parts can be either accessible or
inaccessible. (The safety standards prohibit some of these
parts from being accessible.)
According to your definitions:
> Exposed conductive part: conductive part of equipment, which can be
> touched and which is not normally live, but which can become live when
> basic insulation fails.
Exposed conductive part = My definition 5, and accessible.
> Extraneous/non-electrical conductive part: conductive part not
> forming part of the electrical installation and liable to introduce an
> electric potential, generally the electric potential of a local earth.
Extraneous/non-electrical conductive part = My definition 6.
Your question: Which is a better term for the definition,
extraneous or non-electrical?
In the sense of this discussion, a conductive part is implied to
be an electrically-conductive part. So, a non-electrical
electrically-conductive part could be taken as an oxymoron. Its
certainly not clear as to what is meant.
Let's review Webster's Collegiate Tenth:
Extraneous: 1) existing on or coming from the outside; 2a) not
forming an essential or vital part; 2b) having no relevance; 3)
being a number obtained in solving an equation that is not a
solution to the equation.
So, it seems the word "extraneous" is consistent with the
definition of the part.
Best regards,
Rich
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