Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
AI TechDocKnowledge

Glossary · Electrical engineering and control panels

Protective extra-low voltage (PELV)

Also known as: PELV

German: Funktionskleinspannung mit sicherer Trennung (PELV)

In electrical safety, protective extra-low voltage (PELV) is an extra-low voltage system that is electrically separated from higher-voltage circuits by protective separation but, unlike SELV, may be connected to earth.

  • Control panels

In one sentence

PELV is an extra-low voltage circuit safely separated from higher voltages that, unlike SELV, may be connected to earth.

Example

The 24 V DC control circuit of the machine is designed as PELV: the power supply provides safe separation, and 0 V is connected to the protective bonding circuit.

How it applies

  • Engineering: Most machine control circuits are PELV: the power supply unit provides protective separation, and one side is earthed so earth faults can be detected or cause defined behavior. IEC 60204-1 references PELV for control circuits.
  • Installation: Protective separation must be maintained along the whole circuit, including cable routing and devices connected to it. Mixing PELV and higher-voltage conductors requires suitable insulation.
  • Documentation: State the circuit type in the circuit diagram and component data. The German list term (Funktionskleinspannung mit sicherer Trennung) is an older designation; current German standards simply use PELV.

PELV vs. SELV

Both use extra-low voltage and protective separation. Safety extra-low voltage (SELV) is not connected to earth, PELV may be. The earthed connection changes the protection concept, so the two terms can't be swapped.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: IEC 60364-4-41, Low-voltage electrical installations — Part 4-41: Protection for safety — Protection against electric shock

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

Seen a mistake? Send us a note!