What Are The Common Lightning And Strong Current Protection Measures for Fiber Optic Cable Lines?

1 Preface

Fiber optic cable line lightning and strong electricity, is through the avoidance, channeling or leakage into the ground and other means, in order to prevent lightning/strong electricity on the fiber optic cable line itself or communication equipment and people made damage. Since the lightning protection and strong electricity prevention measures of the fiber optic cable line are often unified, the lightning protection and strong electricity prevention measures of the fiber optic cable line are often considered together in the project.

2 General requirements

In the annual average number of days of thunderstorms greater than 20 days in the region and a history of lightning strikes, fiber optic cable lines should be used to prevent lightning measures.

Severe thunderstorms, new fiber optic cable lines should be avoided around the isolated trees, towers, towering buildings, street trees, woods and other easy to attract lightning targets. When it can not be avoided, should be used arc extinguishing line, can be used non-metallic fiber optic cable.

Fiber optic cable joints on both sides of the metal components should not be electrically connected, should not be grounded.

3 new silicon core pipeline, direct burial of fiber optic cables

New silicon core pipeline or directly buried cable with metal components, should be based on the soil resistivity at a depth of 10m (ρ10) to set the lightning protection line (also known as "discharge line").

Lightning protection line should be 7/2.2 galvanized steel stranded wire, and fiber optic cable, silicon core plastic pipe vertical interval should be 300mm. single lightning protection line should be located in the fiber optic cable, silicon core plastic pipe directly above, double lightning protection line interval between the line should not be less than 300mm, and should not be greater than 600mm. lightning protection line should not be placed in a continuous length of less than 2km.

4 overhead fiber optic cable

4.1 Protection against strong electricity

Poles and power supply lines above 35kV should be crossed vertically, and when they cannot be crossed vertically, the minimum crossing angle shall not be less than 45°. Aerial fiber-optic cable and commonly used electrical facilities crossing the minimum vertical clearance should be in line with the requirements of the following table.

Overhead fiber optic cable and overhead power supply line crossing, should be set up in the lower part of the power supply line. Crossing part of the overhead line should be used three lines of protection insulation splint or protection sleeve fixed in the stranded wire protection, protection length beyond the two sides of the edge of the crossing each 1 m. When the power supply line to the household line for the overlay line, the fiber optic cable can also be in the household line above the crossing.

Overhead fiber optic cable and 10kV or more high-voltage power supply line crossing, crossing file on both sides of the overhead fiber optic cable poles on the hanging line should be done to the ground, the pole on the ground in the ground at a height of 2.0m to disconnect the 50mm discharge gap, both sides of the pole on the line should be installed in the ground at a height of 2.0m with insulators, to do the electrical disconnect. The hanging wires on the nearby poles on both sides of the crossing gear should be retrofitted with insulators and should be made electrically disconnected.

The horizontal clearance between the newly erected electric pole and the power supply line should be not less than 4/3 of the height of the pole, and it is strictly prohibited to erect the pole right under the power supply line.

4.2 Lightning protection

Every 250m or so poles, terminal poles, corner deeper than 1m corner poles, flying line across the pole, pole length of more than 12m poles, poles on the top of the hill should be set up to avoid lightning, overhead suspension line should be connected with the ground. Suspension line should be every 300m ~ 500m using the pole lightning conductor or tie line grounding, every 1km or so should be installed insulators to set the electrical disconnect.

The use of cable as a lightning conductor, 4.0mm steel wire (also known as "galvanized iron wire") one end should be higher than the pole 100mm, 100mm from the top of the pole should be 3.0mm steel wire bundled, and every interval of 500mm bundled once, the other end of the 4.0mm steel line pressed into the cable hoop and its good contact. 4.0mm steel wire on wooden poles should be used for the lightning or pull wire grounding every 1km or so should be installed insulators to set the electrical disconnection. 4.0mm steel wire in the wooden pole should be fastened with nails, nails should be spaced 500mm.

Cement poles without reserved lightning conductor nails, should be used throughout the 4.0mm steel wire as a lightning conductor, along the extension of the pole cloth into the ground; cement poles with reserved lightning conductor nails, should be used 4.0mm steel wire and reserved nails connected.

When the cable is utilized to make the ground line, the cable should be connected to the cable hoop with 4.0mm steel wire through the ground clamp, and enter the ground through the cable.

When there is no tie line to be utilized, the ground line on the pole can be extended, and the ground line on the pole can be 4.0mm steel line or steel stranded wire, and the hanging line is put into the ground through the ground line on the pole.

The underground extension of the pole ground line should be buried in the ground below 700mm, can be "serpentine" extension, is strictly prohibited coil. Extension of the line grounding resistance and extension length should meet the requirements of the following table.

5 Fiber optic cable line terminal grounding

ODF frame of high-voltage protection device should be used cross-sectional area of not less than 35mm2 copper-core power cable lead to the first level of grounding sinks in the room, access to the room's ODF frame can also be used cross-sectional area of not less than 16mm2 copper-core power cable lead to the floor where the room is near the grounding row.

Outdoor fiber optic cable transfer box of high-voltage protection device should be used cross-sectional area of not less than 16mm2 grounding wire connected to the grounding device.

Set in the field of fiber optic cable splitter box can be grounded using the ground rod, fiber optic cable splitter box and ground rod can be connected through the 4.0mm steel wire. Set up in the urban areas of the optical fiber splitter box does not have good conditions for the installation of ground may not be grounded, but should enter the optical fiber splitter box cable to do the ground insulation.

Installed in the indoor fiber optic cable transfer box, fiber optic cable splitter box, fiber optic cable terminal box should be used directly within the building foundation as a steel grounding body, or use a cross-sectional area of not less than 16mm2 multi-stranded copper wire connected to an existing grounding device.

In the ODF, fiber optic cable transfer box, as well as a good grounding splitter box, outdoor fiber optic cable should be used with a cross-section of not less than 6mm2 multi-stranded copper wire will be the metal components of the fiber optic cable and high-voltage protection and grounding device reliably connected. The metal components of the indoor fiber optic cable should be electrically disconnected from the ODF, the high-voltage protective grounding device of the fiber optic transfer box, the rack and the box.

6 Summary

The current technical standards for communication line engineering, lightning protection of fiber optic cable lines and strong electrical protection more along the previous overhead wires or cable lines of protective measures. Some of the protective measures for fiber optic cable lines is too strict but the practical significance is not very large, for example, the grounding resistance of the fiber optic cable transfer box is required to be no greater than 10 Ω. And for the dangerous effects of strong electricity, the actual project is often not enough attention, resulting in fiber optic cable line construction process is still personnel electrocution accidents occur.