Electrical installations of residential, public, administrative and household buildings. Protective security measures

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 7. Electrical equipment of special installations

Electrical installations of residential, public, administrative and household buildings. Protective security measures

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

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7.1.67. Grounding and protective measures for the safety of electrical installations of buildings must be carried out in accordance with the requirements of Ch. 1.7 and additional requirements given in this section.

7.1.68. In all rooms, it is necessary to connect the open conductive parts of general lighting fixtures and stationary electrical receivers (electric stoves, boilers, household air conditioners, electric towels, etc.) to the neutral protective conductor.

7.1.69. In the premises of buildings, metal cases of single-phase portable electrical appliances and desktop office equipment of class I in accordance with GOST 12.2.007.0-75 "SSBT. Electrical products. General safety requirements" must be connected to the protective conductors of a three-wire group line (see clause 7.1.36.).

Metal frames of partitions, doors and frames used for laying cables should be connected to protective conductors.

7.1.70. In rooms without increased danger, it is allowed to use pendant luminaires that are not equipped with clamps for connecting protective conductors, provided that the hook for their suspension is insulated. The requirements of this clause do not cancel the requirements of clause 7.1.36. and are not the basis for two-wire electrical wiring.

7.1.71. To protect group lines supplying socket outlets for portable electrical appliances, it is recommended to provide residual current devices (RCDs).

7.1.72. If the overcurrent protection device (circuit breaker, fuse) does not provide an automatic shutdown time of 0,4 s at a rated voltage of 220 V due to low short-circuit currents and the installation (apartment) is not covered by a potential equalization system, the installation of an RCD is mandatory.

7.1.73. When installing RCDs in series, selectivity requirements must be met. With two- and multi-stage circuits, the RCD located closer to the power source must have a setting and trip time of at least 3 times greater than that of the RCD located closer to the consumer.

7.1.74. In the coverage area of the RCD, the zero working conductor should not have connections with grounded elements and a zero protective conductor.

7.1.75. In all cases, the use of RCDs must ensure reliable switching of load circuits, taking into account possible overloads.

7.1.76. it is recommended to use an RCD, which is a single device with a circuit breaker that provides overcurrent protection.

It is not allowed to use RCDs in group lines that do not have overcurrent protection, without an additional device that provides this protection.

When using RCDs that do not have overcurrent protection, their design verification in overcurrent modes is necessary, taking into account the protective characteristics of the higher-level device that provides overcurrent protection.

7.1.77. In residential buildings, it is not allowed to use RCDs that automatically disconnect the consumer from the network in the event of a power failure or unacceptable drop in mains voltage. In this case, the RCD must remain operational for a time of at least 5 s when the voltage drops to 50% of the nominal.

7.1.78. In buildings, RCDs of type "A" can be used, responding to both alternating and pulsating fault currents, or "AC", responding only to alternating leakage currents.

The sources of pulsating current are, for example, washing machines with speed controls, adjustable light sources, televisions, VCRs, personal computers, etc.

7.1.79. In group networks supplying socket outlets, an RCD with a rated operating current of not more than 30 mA should be used.

It is allowed to connect several group lines to one RCD through separate circuit breakers (fuses).

The installation of RCDs in lines supplying stationary equipment and fixtures, as well as in general lighting networks, is usually not required.

7.1.80. In residential buildings, RCDs are recommended to be installed on apartment shields; they can be installed on floor shields.

7.1.81. The installation of an RCD is prohibited for electrical receivers, the disconnection of which can lead to situations dangerous for consumers (turn off the fire alarm, etc.).

7.1.82. It is mandatory to install an RCD with a rated operating current of not more than 30 mA for group lines supplying outlet networks located outdoors and in especially dangerous and high-risk areas, for example, in zone 3 of bathrooms and shower rooms in apartments and hotel rooms.

7.1.83. The total leakage current of the network, taking into account the connected stationary and portable power receivers in normal operation, should not exceed 1/3 of the rated current of the RCD. In the absence of data, the leakage current of electrical receivers should be taken at the rate of 0,4 mA per 1 A of load current, and the network leakage current at the rate of 10 μA per 1 m of the length of the phase conductor.

7.1.84. To increase the level of fire protection in case of short circuits to grounded parts, when the current is insufficient to operate the overcurrent protection, at the input to an apartment, an individual house, etc. it is recommended to install an RCD with a trip current of up to 300 mA.

7.1.85. For residential buildings when meeting the requirements of clause 7.1.83. RCD functions according to paragraphs. 7.1.79. and 7.1.84. can be performed by one device with a tripping current of not more than 30 mA.

7.1.86. If the RCD is intended for protection against electric shock and fire, or only for protection against fire, then it must disconnect both the phase and neutral working conductors, overcurrent protection in the neutral working conductor is not required.

7.1.87. At the entrance to the building, a potential equalization system must be made by combining the following conductive parts:

main (main) protective conductor;
the main (main) grounding conductor or the main grounding clamp;
steel pipes for communications between buildings and between buildings;
metal parts of building structures, lightning protection, central heating, ventilation and air conditioning systems. Such conductive parts must be interconnected at the entrance to the building.

It is recommended to re-execute additional potential equalization systems during the transmission of electricity.

7.1.88. All open conductive parts of stationary electrical installations accessible to the touch, third-party conductive parts and neutral protective conductors of all electrical equipment (including socket outlets) must be connected to an additional potential equalization system

For bathrooms and shower rooms, an additional potential equalization system is mandatory and should include, among other things, the connection of third-party conductive parts that extend outside the premises. If there is no electrical equipment with zero protective conductors connected to the potential equalization system, then the potential equalization system should be connected to the PE bus (clamp) at the input. Heating elements embedded in the floor must be covered with a grounded metal mesh or a grounded metal sheath connected to a potential equalization system. As an additional protection for heating elements, it is recommended to use an RCD for a current of up to 30 mA.

It is not allowed to use local potential equalization systems for saunas, bathrooms and shower rooms.

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

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