The implementation of an overhead power line (OPL) with insulated conductors SIP 35 kV is an excellent modern solution.
To protect these power lines from impulse (thunderstorm) overvoltages, the rules for the installation of electrical installations require the following:
- Clause 2.5.115: Overhead lines (OHL) with voltages from 110 kV to 750 kV must be protected from direct lightning strikes with lightning protection cables along the entire length of the line.
- Clause 2.5.116: For overhead lines (OHL) with voltages up to 35 kV, the use of lightning protection cables along the entire length of the line is not required.
For protected overhead lines (POL) with voltages from 6 kV to 35 kV, the installation of protective devices (PD) is required to prevent the bridging of insulators on supports from lightning overvoltages or to protect conductors from the action of the power electric arc of the companion current, which arises due to the impulse bridging of insulators from lightning overvoltages.
To prevent the bridging of insulators during storms on supports of protected overhead lines (POL), the following PDs should be installed: surge protection devices (SPD) with a series-connected spark gap or long-spark discharge gaps, or multi-chamber type discharge gaps. These SPDs should be installed one per support with phase rotation. For double-circuit POL, SPDs should be installed on each support, one per phase, in each circuit in such a way as to protect only one pair of identical phases with the same phase rotation principle.
So, we have implemented the construction of several double-circuit protected overhead lines (POL) 35 kV according to projects that involve installing SPDs on each support, one per phase, in each circuit, thus protecting only one pair of identical phases with the same phase rotation principle.
This solution, of course, complies with the requirements of the rules for the installation of electrical installations. However, the cost of these protective devices (PDs) is quite significant, and considering the length of overhead lines (OPL), the cost of the used PDs occupies a significant percentage of the total construction cost of the overhead line (OPL).
In our opinion, since the first paragraph of clause 2.5.116 states that for overhead lines (OHL) with voltages up to 35 kV, the use of lightning protection cables along the entire length of the line is not required, no one explicitly prohibits using lightning protection cables to protect protected overhead lines (POL) with a voltage of 35 kV.
Even considering that installing lightning protection cables on supports requires installing metal brackets, the cost of which may be slightly higher than the cost of brackets for installing PDs on supports, the cost of lightning protection cables from leading European manufacturers will be significantly higher than that of steel lightning protection cables. And if we consider the construction of protected overhead lines (POL) 35 kV with spans between supports of 50…60 m, then the cost difference between the solution with the use of PDs and the use of lightning protection cables can be quite significant.
Therefore, in our opinion, it is necessary to take into account the economic component of the construction of protected overhead lines (POL) in such a challenging time for both our Clients and the country as a whole.
