Electrical installations in fire hazardous areas. Electrical wiring, current conductors, overhead and cable lines

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

Electrical installations in fire hazardous areas. Electrical wiring, current conductors, overhead and cable lines

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

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7.4.36. In fire hazardous areas of any class, cables and wires must have a cover and sheath made of materials that do not spread combustion. The use of cables with combustible polyethylene insulation is not allowed.

7.4.37. Through fire hazardous zones of any class, as well as at distances of less than 1 m horizontally and vertically from the fire hazardous zone, it is forbidden to lay transit electrical wiring and cable lines of all voltages that are not related to this technological process (production).

7.4.38. In fire hazardous areas of any class, the use of bare wires is prohibited (for an exception, see 7.4.27, 7.4.43).

7.4.39. In fire hazardous areas of any class, all types of cable and wire laying are allowed. The distance from cables and insulated wires laid openly directly over structures, on insulators, trays, cables, etc. to places of openly stored (placed) combustible substances, must be at least 1 m.

Laying of unprotected insulated wires with aluminum conductors in fire hazardous areas of any class should be carried out in pipes and ducts.

7.4.40. On overpasses with pipelines with combustible gases and liquids passing through a territory with a fire hazardous zone of class P-III, it is allowed to lay insulated wires in steel pipes, unarmored cables in steel pipes and boxes, armored cables openly. At the same time, steel pipes for electrical wiring, steel pipes and boxes with unarmored cables and armored cables should be laid at a distance of at least 0,5 m from pipelines, if possible from the side of pipelines with non-combustible substances.

7.4.41. For mobile electrical receivers, portable flexible cables with copper conductors, with rubber insulation, in a sheath resistant to the environment, should be used.

7.4.42. Junction and branch boxes used in electrical wiring in fire hazardous areas of any class must have a degree of protection of the shell of at least IP43. They must be made of steel or other durable material, and their dimensions must ensure ease of installation and reliable connection of wires.

Parts of boxes made of metal must have an insulating lining inside or a reliable color. Plastic parts, except for those used in a group lighting network, must be made of slow-burning plastic.

7.4.43. In fire hazardous zones of classes P-I, P-II and P-IIa, it is allowed to use busbars up to 1 kV with copper and aluminum tires with a degree of protection IP20 and higher, while in fire hazardous zones P-I and P-II all tires, including including branch busbars, must be insulated. In busbar trunkings with IP54 and higher protection, it is allowed not to insulate the busbars.

Non-separable contact connections of tires must be made by welding, and demountable connections - using devices to prevent self-unscrewing.

The temperature of all elements of bus ducts, including junction boxes, installed in fire hazardous zones of class P-I, must not exceed 60ºС.

7.4.44. Branch boxes with switching and protective devices, as well as detachable contact connections, can be used in fire hazardous areas of all classes. At the same time, junction boxes installed on busbars, including cable entry points (wires) and places of contact with busbars, must have a degree of protection of IP44 and higher for fire hazardous zones of classes P-I and P-IIa, IP54 and higher for zones of class P-II .

For zones of classes P-I and P-II, an advanced break in the branch circuit must be provided at the time of switching of detachable contact connections.

In the premises of archives, museums, art galleries, libraries, as well as in fire hazardous areas of warehouses, the use of detachable contact connections is prohibited, with the exception of connections in temporary networks when displaying expositions.

7.4.45. Distances from the axis of the overhead line to fire hazardous areas should be selected according to 2.4.64 and 2.5.163, with the exception of distances from overhead lines up to 1 kV with bare wires made of aluminum, steel-aluminum or aluminum alloys to open ground warehouses listed in Table. 7.4.4. The distance from the axis of the overhead line up to 1 kV to the warehouses listed in Table. 7.4.4, must be not less than that indicated in Table. 7.4.5; this requirement does not apply to outdoor lighting overhead lines located on the territory of warehouses.

Table 7.4.4. Open ground warehouses for storage of combustible materials and substances, finished products and equipment

Warehouses	Capacity, area
Coal, peat, roughage (hay, straw), flax, hemp, cotton, grain	More than 1000 t
Timber, firewood, wood chips, sawdust	Over 1000 m³
combustible liquids	Over 3000 m³
Finished products and equipment in combustible packaging	Over 1 ha

Table 7.4.5. The smallest distance from the axis of the overhead line up to 1 kV with uninsulated wires made of aluminum, steel-aluminum or aluminum alloys to the boundaries of open ground warehouses listed in Table. 7.4.4.

Suspension height of the upper wire of the overhead line from ground level, m	The smallest distance, m, at the estimated wind speed, m/s (wind area)
	16(I)	18(II)	21(III)	24(IV)	27(V)	30(VI)	33(VII)
Until 7	17	19	27	31	36	41	46
7,5	18	20	31	33	38	43	48
8	19	21	35	35	40	45	50
9	20,5	23	37	37	43	49	53
10	22	24	40	40	46	53	57

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