Notes on high voltage electricity

• Terminology
• Germany
• Color coding in Europe
• Earthing systems
• References

Terminology

Terms that are commonly used in high voltage/AC/mains electrical systems.

• The term earth is more commonly used in British English, and the term ground is more common in North American English¹. Both terms are mostly used synonymously.

• PE should under normal conditions not carry current. PE is an integral part in home/residential wiring because it causes circuit breakers (GFCI) to trip more quickly in case of leakage current.

• GFCI/RCD are safety devices that quickly break the electrical circuit if leakage current (typically $5-30mA$ ) is detected to earth.

  In Germany, these are commonly only installed in wet rooms.

• Ground and neutral are closely related but not the same. Neutral point of an electrical supply system is often connected to earth ground.

• Stray voltage is electrical potential between two objects that shouldn't have any voltage difference between them² (e.g. $PE$ and $N$).

• Type C plugs are commonly known as europlug³.

• Type F plus are commonly known in Germany as Schuko⁴ (Schutzkontakt).

Germany

• Germany is a full member of IEC.
• In Germany, DKE (Deutsche Kommission Elektrotechinik Elektronik Informationstechnik in DIN und VDE) is the organization responsible for the promulgation of electrical standards and safety specifications⁵.
• DIN VDE 0100 is the German wiring regulations document that is harmonized with the standard IEC 60364⁶.

Color coding in Europe

Color coding required by the European Committee for Electrotechnical Standardization (CENELEC) as defined in IEC 60446 Wiring colors⁷:

Color	Conductor	Graphic
Brown	Single-phase live / L1	5
Black	L2 live in 3-phase circuits
Grey	L3 live in 3-phase circuits
Blue	Neutral
Green/yellow	Protective earth

• IEC 60446 is now a part of IEC 60445 Basic and safety principles for man-machine interface, marking and identification - identification of equipment terminals, conductor terminators and conductors⁵. IEC 60446 has subsequently been marked as withdrawn.
• In Sweden the local national standard SS-436 40 000 allows the exceptional for blue (normally reserved for neutral) to be used as a connecting wire between switches, between switch and fixture, as well as phase wire in a two-phase circuit under the condition that no neutral wire is used in the particular circuit⁵.

Earthing systems

The IEC 60364 standard⁶ defines three "families" of earthing systems, using two letter codes.

1. First letter⁸ denotes how the connection to earth is made:

• T: Direct connection to a point with earth (Latin: Terra)
• I: No point is connected with earth (Latin: insulatum), except maybe with high impedance.

2. Second letter⁸ denotes where earth connection is supplied from:

• T: Local direct connection to earth (earthing rod for example).
• N: Electricity supply network, either separately to by the neutral conductor (TN-S) or combined with the neutral connector (TN-C) or both (TN-C-S).

The different TN systems are:

• TN-S: PE (protective earth) and N are separate conductors that are connected together only near the power source⁸.

  Normal circuit currents flow only in the N, and PE bonds all equipment cases to earth to intercept any leakage current (installation failure).

  Neutral conductor is connected to earth at he point of supply, but no common path to ground exists for circuit current and protective conductor.

• TN-C: A combined PEN conductor fulfills the functions of both a PE (protective earth) and N conductor⁸.

  Neutral conductor is connected to earth ground at the point of supply, and equipment vcaseds are connected to the neutral (as opposed to PE in TN-S).

  The danger with TN-C is that a broken neutral connection will allow all the equipment cases to rise to a dangerous voltage if any leakage of insulation fault exists in any equipment.

• TN-C-S: Each piece of electrical equipment has both a protective ground connection to its case⁸, and a neutral connection. These are all brought back to some common point in the building system, and a common connection is then made from that point back to the source of supply and to the earth.

• TT: No lengthy common protective ground conductor is used¹. Instead each terminal, equipment or distribution system has its own connection to earth ground.

References