Selection of electrical conductors and layout of power distribution equipment

Conductor selection

1) The type of conductor should be selected according to the laying method and environmental conditions. In addition to meeting the above conditions, the insulated conductor should meet the requirements of the operating voltage.

2) Select the conductor cross section and meet the following requirements:

1. The line voltage loss should meet the requirements of the normal operation of the electrical equipment and the voltage at the starting time;

2. The current carrying capacity of the conductor determined according to the laying method and environmental conditions shall not be less than the calculated current;

3) Cooling conditions of the laying route: When laying insulated conductors and cables along different cooling conditions, when the length of the worst cooling section exceeds 5 m, the section of insulated conductor and cable should be selected according to the conditions of the section, or only the section Use insulated wires and cables with large cross sections.

4) Correction of the temperature of the ring laying environment: The allowable current carrying capacity of the conductor should be corrected according to the ambient temperature of the laying place. The temperature correction coefficient can be calculated as follows:

k=√(t1-t0)/(t2-t0)(2.2.4)

Where k: temperature correction coefficient;

T1: the maximum allowable operating temperature of the conductor (°C);

T0: ambient temperature of the laying place (°C);

T2: ambient temperature (°C) used in the conductor current carrying capacity standard;

5) Ambient temperature of the wire laying place:

1. The cable directly laid in the soil, using the monthly average temperature of the hottest month of the laying place;

2. The bare conductor laid in the air, the average maximum temperature of the hottest month in the area where the area is laid; the average maximum temperature of the hottest month in the house (the average of 10 years or more is taken.)

6) Neutral section

1. In the three-phase four-wire power distribution system, the allowable current carrying capacity of the neutral line (hereinafter referred to as n line) shall not be less than the maximum unbalanced load current in the line, and shall be included in the influence of harmonic current.

2. In the circuit with the gas discharge lamp as the main load, the neutral line cross section should not be smaller than the phase line cross section.

3. Use single-core wire as the neutral wire for protecting the neutral wire (hereinafter referred to as the pen wire). When the cross-section is copper, it should not be less than 10mm2; when it is aluminum, it should not be less than 16mm2; the core wire with multi-core cable For the pen line trunk line, its cross section should not be less than 4mm2.

7) Cross section of protection line (hereinafter referred to as pe line)

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