The relevance or earthing. Thank you Peter for your so obvious conclusions drawn about the Netherlands Soil. Our lab resides below sea level (approx 4 meters) and we do have easy grounding possibilities.
What is the purpose of grounding however. There is no relevance creating a reliable true earth connection, if the local soil such as in Norway would reside on another voltage level. The purpose of ground is creating a means of putting any touchable piece of metal of an electrical apparatus at a safe voltage level, i.e. the level of it's surrounding such as water supply pipes, gas and heating metal and the voltage level of iron in concrete buildings. The local soil would couple it's CM voltage on every building and pipe, and the only truly safe grounding level that creates a safe earth is local soil potential, whatever level it may reside compared to (Holland) sea level soil potential. BTW since few years all new outlets in Holland will be 3-pole: phase, null and earth, or in some older cities +phase, -phase and earth. Regards, Gert Gremmen, (Ing) ce-test, qualified testing =============================================== Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ =============================================== >>-----Original Message----- >>From: [email protected] [mailto:[email protected]]On Behalf >>Of Pete Perkins >>Sent: Wednesday, January 31, 2001 6:53 AM >>To: PSNet >>Subject: Unreliability of earthing/grounding >> >> >> >> >> PSNet, >> >>Unreliability of earthing/grounding >> >> In the PSNet discussion on touch current, a comment was >>made regarding >>earthing/grounding as it applies to cord connected equipment >>using the most >>common North American NEMA-15 or EURO 10A plugs types (called >>Pluggable Type >>A connections in the 60950 family of standards). >> >> The common use of 3-wire earthed/grounded plugs and sockets >>is a fairly >>recent addition to the wiring codes. This requirement was >>generally invoked >>around 1960 in North America, West Germany & Austria. From this >>it is easy >>to understand that this means that yet today there are many >>unearthed/ungrounded 2-wire installations. >> >> There is not a lot of worldwide data available, but in the >>US Underwriters >>Labs has developed a tracking scheme to estimate the relative >>proportion of >>earthed/grounded to unearthed/ungrounded installations, >>especially relating >>to domestic dwellings. From their information, around the turn of the >>Millennium about ½ of the homes are still 2-wire installations. Added to >>this would be a smaller percentage of businesses (since they are >>more likely >>to get a full electrical remodeling than homes). >> Data is not as readily available for other developed >>countries or regions, >>but something similar seems reasonable. >> In the EU, Holland still does not install 3-wire, earthed >>sockets in all >>locations (although any installation could be easily earthed >>locally because >>of the soil conditions). Norway, on the other hand, cannot >>easily provide a >>local earth since the country is built upon a granite rock so earthing is >>only guaranteed when a specific wire is carried thru the electrical system >>for that purpose - (which often leads to the derogatory comment that the >>Nordic countries are dragging their feet on some changes proposed >>to product >>standards). >> Anecdotal evidence for the developing countries reflects >>the fact that >>earthing is not reliable because of the inconsistencies of installation >>practices. >> >> Because of these conditions, the earthing/grounding is not >>reliable and the >>loss of earth/ground under these conditions is the normal case, >>not a fault. >> >> All of this is compounded by the tremendous expansion of >>the use of many >>products that were, in the past considered commercial, in the individual >>home office or small office developed by converting homes to business use. >>This not only includes PC’s and fax-machines but will also include >>workstations, copiers, servers, telephone switches and ATM’s (for >>delivering >>not only cash, but phone cards, phones and other hi-value items) which are >>installed rather ubiquitously. In the US, any shop that carries >>electrical >>supplies also carries a 3-wire to 2-wire adapter – commonly known as a >>cheater. >> >> The prudent manufacturer will know that the design of the >>equipment should >>take this into account – even though this may not be properly >>accounted for >>in the safety standard that is normally used. >> >> br, Pete >> >> Peter E Perkins, PE >> Principal Product Safety Consultant >> Tigard, ORe 97281-3427 >> 503/452-1201 fone/fax >> [email protected] >> >> >>------------------------------------------- >>This message is from the IEEE EMC Society Product Safety >>Technical Committee emc-pstc discussion list. >> >>To cancel your subscription, send mail to: >> [email protected] >>with the single line: >> unsubscribe emc-pstc >> >>For help, send mail to the list administrators: >> Jim Bacher: [email protected] >> Michael Garretson: [email protected] >> >>For policy questions, send mail to: >> Richard Nute: [email protected] >> >>
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