Hi Folks

A few years ago I worked for BSI "Technical Help to Exporters" and helped to
update their publication "World Wide Plugs and Sockets Survey" - which I
assume is still available from BSI (see www.bsi-global.com)

I remember looking at the Korean standards for plugs and sockets:- Yes -
they were/are variations of Schuko types(both with and without earthing
contacts), but I also seem to remeber some NEMA (USA/Canadian) types as
well.

However, as part of another large exercise for a customer I reviewed many of
the European wiring rules standards to identify any conventions or
requirements for the polarity of wiring-up of sockets - notably those that
accept the various versions of the (generally reversible) Schuko plugs and
also the somewhat similar Danish, Swiss and Italian plugs.

Result : there were (and presumably still are) wiring colour codes for the
building wiring to these sockets - BUT NO CONVENTION AS TO WHICH COLOUR IS
CONNECTED TO WHICH CONTACT TUBE OF THE SOCKET, apart (obviously) from the
requirement that the Green/Yellow insulated conductor be connected to the
earthing contact.

Therefore you must always assume that the Line/Neutral polarity of the wall
socket is random - this is also true for the French version of the socket
with the earthing pin projecting out since it is only a (more recent?)
variety of the type of socket which has no such pin.

Thus the equipment connected to it must have some sort of double-pole
disconnect device (be it a switch, or the plug itself). 

Double-pole fusing requirements may depend on the product standard
requirements, but is effectively required where the internal wiring of the
equipment cannot deal with the full prospective fault current available from
the wall socket.

Hope this clarifies matters.

Regards

John Allen
Thales
Bracknell, UK.



-----Original Message-----
From: Robert Wilson [mailto:robert_wil...@tirsys.com]
Sent: 20 February 2002 19:17
To: emc-p...@majordomo.ieee.org
Subject: RE: South Korean Power System



Schuko plugs come in two basic versions. The original (larger) plug has
two solid round pins for the AC interconnect, and two metal strips along
the side of the plug (one on each side) that are grounding contacts.
When inserting the plug, the body of the plug disappears into the socket
recess BEFORE any electrical contact is made, making them far safer than
the plugs used in North America. Ground contact to the side ground
strips is made before any AC contact. These plugs have no polarization
feature when used in German and most other European Schuko sockets. The
plug can be rotated 180 degrees with no possibility of polarizing it.

However, the Schuko plug had to accommodate the slightly different
French AC socket. This socket is almost the same as the "normal" Shuko
socket, but there is a ground pin that sticks OUT of the recessed
socket, and inserts into a hole in the Schuko plug beside the 2 AC pins.
This hole has a female contact (that is in parallel with the grounding
strips along the edges of the plug). If the French ONLY be inserted one
way around.

The second type of Schuko plug is rather like the North American 2-prong
plug (except is not nowhere near as cheap, flimsy or dangerous). It is
flat and has no ground contact. There are two solid round pins, but they
are made of plastic, with metal contacts ONLY at the very tips, so once
again, no metal is exposed once contact is made.  

Bob Wilson
TIR Systems Ltd.
Vancouver.

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