Requirements for directly buried external telecommunication cables in Vietnam

According to Clause 2.3.3, Section 2 of the National Technical Regulation on the Installation of External Telecommunication Cable Networks issued together with Circular 20/2019/TT-BTTTT (effective from July 1, 2020), the requirements for directly buried external telecommunication cables in Vietnam are as follows:

- General requirements

+ The cable route must be the shortest possible (under given terrain and space conditions).

+ Ensure a safe distance from the cable to other underground structures such as water supply pipes, wastewater sewers, and fuel pipes in underground ducts as specified in Table 4.

+ Ensure the minimum distance between the directly buried cable route and power cables, railways according to safety regulations of the power and railway sectors.

+ Ensure the minimum distance between the directly buried cable route and certain other structures as specified in Table 4.

+ In case of using directly buried cables in areas under construction or areas not yet stable in urban architectural construction, a warning tape must be used above the buried cable at least 10 cm, or a marker pole must be used for signaling.

Figure 2 - Placing warning tape over directly buried cable route

+ The directly buried cable route must follow the priority order from highest to lowest as follows:

++ Bury the cable under the sidewalk or the median strip between two traffic lanes.

++ Bury the cable under the roadbed. In this case, the cable route must run close to one side of the road edge; if it is a one-way street, choose the right-hand edge according to the one-way direction.

++ Underground telecommunication cables must be tagged with ownership (made of a material resistant to moisture) at locations such as cable chambers, manholes; cabinets, or cable boxes in compliance with this Regulation.

++ When laying underground telecommunication cables inside ditches or water drains, appropriate cable protection measures must be taken without affecting the water flow. During construction, existing greenery must not be affected.

+ Underground telecommunication cable routes must be marked for the identification of underground conduits, cables, and pipes as specified in Joint Circular No. 21/2013/TTLT-BXD-BCT-BTTTT.

- Requirements for cable trenches

+ The dimensions of the cable trench must be calculated to fit the quantity, type, and protection method of the cables.

+ The trench depth depends on the soil grade as specified in Table 7.

Table 7 - Trench Depth

- Requirements for safety distance between directly buried telecommunication cables and electrical systems

+ To avoid increased ground potential due to fault currents passing through grounding systems of power systems, telecommunication cables with metal sheaths directly in contact with the soil must be distant from power system grounding. If local conditions do not allow for a safe distance, high-voltage-resistant sheathed telecommunication cables or cables in plastic insulating pipes must be used.

+ In areas with significant increases in ground potential, copper cables must be replaced with fiber optic cables or a microwave system must be used as a replacement. The minimum distance between telecommunication cables with metal sheaths in contact with the soil and the grounding of high-voltage power systems must comply with electrical safety requirements as per QCVN 01:2008/BCT and related electrical safety regulations, and must be approved by the power management unit.

+ To prevent direct contact between power cables and directly buried telecommunication cables at crossings, the telecommunication cable must be enclosed in a rigid PVC pipe and placed above the high-voltage cable, with the distance specified in Table 4.

The editorial board of Lawnet informs you.