Factors affecting the flow of high-voltage insulated overhead cables

The high-voltage insulated overhead conductor has the structure of a common grounding clamp, and an external gap discharge device is added. 

The piercing electrode at the upper end can penetrate the wire insulation layer to make the lightning protection grounding ring and the wire form an electrical connection, and the ground rod is attached to the line for maintenance. 

The grounding connection of the line; a lower arcing electrode at the lower outer side of the grounding ring is provided with a pilot arc electrode, and a discharge gap is formed corresponding to the steel leg flange of the line column insulator PS15 or PS20.

During normal operation, there is a large air gap between the arcing electrode and the flange of the insulator steel or the grounding electrode, and no current flows; when the lightning induced over voltage of the wire exceeds a certain value when lightning occurs, or when a direct lightning strike is encountered.

A flashover is formed between the arcing electrode and the grounding electrode to form a short circuit, and the continuous power frequency arc is burned between the arcing electrode of the lightning protection grounding clamp and the grounding electrode or the insulator steel foot flange to release the overvoltage energy. 

To protect the wire from burnout. Its special material determines its high mechanical strength. 

When the cable is crushed by an external force to 2/3 of the original cable diameter, the current-carrying surface can be kept unchanged. 

Since the materials constituting the wire are all inorganic materials, there is no flammable medium, the cable can be normally energized at a temperature close to the melting point of copper, and the fireproof performance is excellent. 

Therefore, the copper core wire and cable is a fire-fighting system and requires a safe place to replace the flame retardant. Trending products for refractory cables. 

The factors that affect the wire may be the following:

1. Ambient Temperature

The ambient temperature value used is the temperature of the surrounding medium when the cable or conductor under consideration is not loaded.

2. Parallel Wires

When two or more wires are connected in parallel in the same phase or the same pole of the system, measures should be taken to ensure that the parallel wires share the load current evenly.

3. The number of overhead wires with high-voltage insulation

The number of wires to be considered in a loop is the number of wires carrying the load current. 

It is not necessary to consider the neutral line when it can be assumed that the conductor carries the balancing current in the multi-phase loop. 

When the neutral line carries current and the phase line load is not reduced accordingly, the neutral value of the loop current rating should be considered. 

Wires that are only used as protective conductors should not be considered. The PEN line should be considered the same as the neutral line.

4. Soil thermal resistance rate 

For cables buried in the ground, where the actual soil thermal resistivity is higher than 2.5Km/W, the current carrying capacity must be appropriately reduced or the soil around the copper core wire and cable should be a suitable material replacement.

5. Changes in laying conditions along the route

When the cooling conditions of the various parts of the wiring path are different, the current carrying capacity of the copper core wire and cable shall be determined to be suitable for the unfavorable part of the path.

6. Multi-loop grouping

When installing more wires or cables in the same group, you must multiply by the specified correction factor. The group correction factor is calculated on the assumption that a load of each loop cable of the group is the same.