PEN head

from Wikipedia, the free encyclopedia

A PEN conductor (Abbr. For English protective earth neutral ) is a conductor at the same time the functions of the protective conductor (PE) and the neutral conductor satisfied (N). A ladder with such a double function is only possible in a TN-C system .

In older standards, the PEN conductor with functionally the same meaning was referred to as the “zero conductor” until around 1991, although the official renaming to “PEN conductor” took place in 1973. The neutral conductor was originally made in Germany in gray and from December 1965 in blue, in Switzerland originally in yellow, then in light blue and blue. The protective conductor (PE), however, is marked with a green-yellow color. Originally the protective conductor had a red color coding in Germany and a yellow-red color coding in Switzerland (see historical development of the protective conductor ).

Since the PEN conductor has a protective conductor function, it must not be pluggable or switchable separately from the external conductors, not even through overcurrent protection devices . Only the outer conductor (s) is / are to be separated or a mechanically coupled two- or four-pole switching device must be used.

In new systems, PEN conductors have been permitted in Germany since May 1973, and in Austria since January 1976, only permanently installed with a conductor cross-section of at least 10 mm² copper or 16 mm² aluminum. In Switzerland, zeroing scheme III ("classic zeroing") has been prohibited since 1974 for new installations . This measure was taken in order to keep the probability of a PEN conductor interrupted (e.g. due to mechanical influences) low. In Germany this was included in VDE 0100. Indirectly, the specification of a large minimum cross-section also prevents the previously common practice of "classic zeroing" by means of a short connection from the neutral conductor to the protective conductor connection to Schuko and SEV-1011 sockets.

An interruption in the PEN conductor not only negates the protective effect, but also harbors additional risks for electrical accidents if the outer conductors are still active . Housings of consumables of protection class I , such as washing machines and refrigerators, can carry a partial voltage of an outer conductor up to 230 volts to earth. No earth fault current can flow through the interrupted PEN conductor and the protective measure “automatic shutdown of the supply voltage” by triggering the fuse has no effect . This could result in a life-threatening electric shock for a person who touches these devices . In addition, no working current can flow and the connected devices do not work, which can give a layperson the impression that there is no voltage.

An interruption in the PEN conductor also leads (in the network section after the interruption) to the neutral point in the AC network no longer being held at zero potential. With the usual star connections in the consumer networks, a floating star point is created, the potential of which depends on the resistance of the current consumer on the three outer conductors and can vary extremely due to switching processes. This means that in extreme cases, up to almost 400 V can be present on a 230 V consumer circuit.

  • Example: A heater with 3680 watts (corresponding to 14.4 ohms) is connected to one outer conductor and a soldering iron with 20 watts (corresponding to 2645 ohms) is connected to another outer conductor. The other pole of both devices is connected to the neutral point of the power grid via the common PEN conductor. This means that 230 volts are applied to each of the devices. However, if the PEN conductor is interrupted and there is no connection to the star point, the two resistors are connected in series to 400 V and form a voltage divider on which the voltage is distributed in proportion to the resistors. The soldering iron is then operated with 397.8 V, the heater, on the other hand, only with 2.2 V.
Color scheme for PEN conductor

In the DA-CH countries, PEN conductors must be marked for new systems with the color combination green-yellow over the entire length and also with blue marking on the conductor ends. Existing PEN conductors (with a sufficient cross-section) can also be color-coded in blue over the entire length if they are provided with green-yellow marking at the conductor ends. By convention, the PEN leader is not designated as an active leader.

The PEN conductor can no longer be used in connection lines of mobile devices and in new house installations. As a general standard (with local exceptions) today in DA-CH the supply with a TN-C network with three outer conductors and with a PEN conductor at the transfer point from the network operator to the customer can be seen. According to the current TAB, the PEN conductor is divided into an N and a PE conductor and a 5-pole continuation of the installation exclusively as a TN-CS system in the main power supply system (usually in the house connection box ). Immediately from the PEN distribution, a PEN conductor (corresponding cross-section) is led to the main earthing rail (previously main equipotential bonding ). From the transition from the TN-C to the TN-CS system, the protective conductor (PE) and neutral conductor (N) are kept strictly separate in the further course of the line. According to DIN VDE 0100-540: 2012-06 (Section 543.4.3), it is not permitted to connect the neutral conductor to any other earthed part of the system in the further course of the line, or to reconnect it with the protective conductor.

In the current edition of DIN VDE 0100-540: 2012-06, in Section 543.4, the treatment of the PEN, PEL or PEM conductor is presented in detail and unambiguously , in addition to earlier versions .

literature

Individual evidence

  1. ↑ VDE 0100: 1973-05, §3 c) 4 (replaces 1991-11), VDE 0100-200: 1982-04, section 6.4 (replaces 1985-07) and VDE 0100-430: 1981-06, section 10.3. (replaces 1991-11)
  2. ↑ See document CENELEC 64A (CH) 101/73 of October 1973. At a standardization meeting on June 26, 1975 in Ankara, Switzerland's application (at TC 64) to rename the neutral conductor to “PEN conductor” was accepted.
  3. ↑ VDE 0100 / 12.65, § 10N, b 9.1 for the protective conductor and at the same time in § 10N, b 8.1 for the neutral conductor (today PEN conductor)
  4. ↑ VDE 0100 / 5.73 Regulations for the erection of high-voltage systems with nominal voltages up to 1000 V.
  5. ↑ https://www.schrack.at/fileadmin/f/at/Normen_und_Bundesgesetze/Fachinformationen_OEEK/Elektrische_Niederspannungsanlagen/Anlagen_mit__Klassischer_Nullung__-_was_ist_zu_tun.pdf
  6. ↑ a b DIN VDE 0100-540 (VDE 0100-540): 2012-06 Construction of low-voltage systems - Part 5-54: Selection and installation of electrical equipment - Earthing systems, protective conductors and protective equipotential bonding conductors.
  7. ↑ Archived copy ( memento of the original dated August 29, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.electrosuisse.ch
  8. ↑ DIN VDE 0100-510 (VDE 0100-510): 2011-03 Installation of low-voltage systems - Part 5-51: Selection and installation of electrical equipment - General provisions; Marking, section 514.3.2 PEN conductor, PEL conductor and PEM conductor