Grounding and protective measures for electrical safety. Protective measures against direct and indirect contact

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 1 General Rules

Grounding and protective measures for electrical safety. Protective measures against direct and indirect contact

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.7.73. Extra low (low) voltage (SLV) in electrical installations with voltage up to 1 kV can be used to protect against electric shock from direct and / or indirect contact in combination with protective electrical circuit separation or in combination with automatic power off.

In both cases, a safety isolating transformer in accordance with GOST 30030 "Isolating transformers and safety isolating transformers" or another source of SLV that provides an equivalent degree of safety should be used as a power source for the SLV circuits in both cases.

The current-carrying parts of the ELV circuits must be electrically separated from other circuits so that an electrical separation equivalent to that between the primary and secondary windings of an isolating transformer is ensured.

The conductors of the SLV circuits, as a rule, must be laid separately from conductors of higher voltages and protective conductors, either separated from them by a grounded metal screen (sheath), or enclosed in a non-metallic sheath in addition to the main insulation.

Plugs and sockets of plug connectors in ELV circuits must not allow connection to sockets and plugs of other voltages.

Plug sockets must be without protective contact.

For VLV values above 25 V a.c. or 60 V d.c., protection against direct contact shall also be provided by guards or enclosures or insulation suitable for a test voltage of 500 V a.c. for 1 min.

1.7.74. When using SLV in combination with electrical separation of circuits, exposed conductive parts must not be intentionally connected to the earth electrode, protective conductors or exposed conductive parts of other circuits and to third-party conductive parts, unless the connection of third-party conductive parts to electrical equipment is necessary, and the voltage on these parts cannot exceed the CNN value.

SLV in combination with electrical separation of circuits should be used when using SLV it is necessary to provide protection against electric shock if the insulation is damaged not only in the SLV circuit, but also if the insulation is damaged in other circuits, for example, in the circuit supplying the source.

When using SLV in combination with automatic power off, one of the outputs of the SLV source and its case must be connected to the protective conductor of the circuit supplying the source.

1.7.75. In cases where the electrical installation uses electrical equipment with the highest operating (functional) voltage not exceeding 50 V AC or 120 V DC, such voltage can be used as a measure of protection against direct and indirect contact, if the requirements of 1.7.73 are met. - 1.7.74.

See other articles Section Rules for the installation of electrical installations (PUE).

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