Protective measure (electrical engineering)

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In electrical engineering, a protective measure refers to the precautions taken to protect people and animals against electric shock as a result of dangerous contact voltage .

General

A protective measure always consists of a combination of two independent protective measures, basic protection and fault protection . Hazardous active parts must not be accessible or touchable under normal conditions. Furthermore, in the event of a fault, dangerous contact voltages are prevented from occurring on accessible conductive parts or surfaces.

Basic protection

As a basic protection is defined as the provision for protection against direct contact with live parts which are under normal operating conditions voltage.

Error protection

As error protection is defined as the provision for protection against indirect contact of exposed conductive parts. These are bodies (surfaces) of electrical equipment or external conductive parts that must not accept any dangerous contact voltage in the event of a fault. As an alternative, fault protection also includes double or reinforced insulation.

Classification of protective measures

Several protective measures against excessively high contact voltage are defined, a distinction is made between:

  • network-independent protective measures
  • network-dependent protective measures

Network-independent protective measures

No protective conductor is required for these protective measures . A protective conductor may be used with PELV.

Network-dependent protective measures

Today's networks always assume a star-connected three-phase transformer . The old versions with transformer coils connected in a triangle only allowed conductor-conductor voltages without reference to earth. They are being broken down more and more and are becoming increasingly rare. The old networks can be recognized by the two-pole protection. Today's network forms are divided into TN systems , TT systems and IT systems .

To present the protective measure, reference is now made to the underlying network type, because not every protective measure can be implemented in all networks.

Shutdown protection

These protective measures are only permitted as additional protection. It would therefore not be permissible to operate a device in which all electrically conductive parts and parts belonging to the operating circuit are not isolated just because one of the following protective measures is applied.

All of these protective measures mentioned here only serve to protect against indirect contact.

Protection through reporting

This protective measure is only used in the IT network; it is called an IT system with insulation monitoring. This protective measure used to be called the protective line system .

Additional measures

Additional measures apply to the protective measures protection by switching off or reporting:

Special measures

In addition to the measures that offer complete protection such as B. protective insulation, there are also measures that offer partial protection:

  • Protection through distance
  • Protection from obstacles

Laws and norms

  • EN 61140: 2002-03 + A1: 2006-08 (IEC 61140: 2001 + A1: 2004 modified; VDE 0140-1: 2007-03) Protection against electric shock - common requirements for equipment and systems
  • HD 60364-4-41: 2007-01 (IEC 60364-4-41: 2005-12 modified; VDE 0100-410: 2007-06) Installation of low-voltage systems - Part 4-41: Protective measures - Protection against electric shock

literature

  • Wolfgang Hofheinz: VDE publication series "Standards understandable" - protection technology with insulation monitoring . Volume 114, 2nd revised edition, VDE-Verlag GmbH, Berlin and Offenbach 2007, ISBN 978-3-8007-3026-1 .

Individual evidence

  1. ^ A b Klaus Tkotz, Peter Bastian, Horst Bumiller: Electrical engineering. 27th revised and expanded edition, Verlag Europa-Lehrmittel Nourney Vollmer GmbH & Co. KG, Haan Gruiten 2009, ISBN 978-3-8085-3188-4 .
  2. ↑ a b c Gerhard Kiefer: VDE 0100 and the practice. 1st edition, VDE-Verlag GmbH, Berlin and Offenbach, 1984, ISBN 3-8007-1359-4 .
  3. ^ A b Hans-Günter Boy, Uwe Dunkhase: The master's examination in electrical installation technology. 12th edition, Vogel Buchverlag, Oldenburg and Würzburg, 2007, ISBN 978-3-8343-3079-6 .
  4. ↑ Ernst Hörnemann, Heinrich Hübscher: Electrical engineering specialist training in industrial electronics. 1st edition. Westermann Schulbuchverlag GmbH, Braunschweig, 1998, ISBN 3-14-221730-4 .
  5. ↑ Nils Hagge: Protective measures and measuring technology. University of Hanover online ( memento from June 12, 2007 in the Internet Archive ) (accessed from archive.org on August 24, 2015; PDF file; 504 kB).

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