1 - Schneider Electric SNB
1 - Schneider Electric SNB
1 - Schneider Electric SNB
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Understanding (EMC) phenomena<br />
Type<br />
Source<br />
Transmission<br />
Frame connections<br />
Symbol :<br />
General definition<br />
1<br />
2<br />
3<br />
4<br />
5<br />
A frame connection is an equipotential connection point or plane that may or may not be connected to earth and<br />
which is used as a reference for a circuit or system.<br />
Note: a frame connection having a potential that is deliberately specific or variable must be the subject of special<br />
insulation and, if applicable, connection measures.<br />
Specific definition for electrical installations<br />
A frame connection is any exposed conductive part of apparatus, equipment or an installation that is not live<br />
during normal operation but which may become so in the event of a fault.<br />
Examples of frame connections (exposed conductive parts) :<br />
- metal structure of a building (framework, piping, etc.),<br />
- machine bed plates,<br />
- metal cabinets, unpainted cabinet bottoms,<br />
- metal cable troughs,<br />
- transformer casing, Programmable Logic Controller backplate, etc.<br />
- green/yellow wires (PE/PEN) of earthing conductor.<br />
Exposed conductive parts and safety of persons<br />
and property<br />
Basic Specification IEC 364 and national texts that are specific to certain installations describe the constructional<br />
arrangements that guarantee compliance with adequate safety levels.<br />
Regardless of the installation’s earthing arrangement, green/yellow so-called «PE» or «protective earth»<br />
conductors having a defined impedance are provided for connecting exposed conductive parts to earth and to<br />
the origin of the installation so that :<br />
• During normal operation or if there is a fault to an exposed conductive part :<br />
- high fault currents are eliminated (safety of property),<br />
- no hazardous voltage can occur between two exposed conductive parts, an exposed conductive<br />
part and the soil or metal structure (safety of persons),<br />
Te<br />
• Since the safety of installations takes precedence over every other aspect, subsequent work on the<br />
connection of exposed conductive parts shall, under any circumstances, involve :<br />
- disconnecting a «PE» (green/yellow) conductor from an exposed conductive part,<br />
- increasing the impedance of any «PE» connection.<br />
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