An optical ground wire (also known as an OPGW or, in the IEEE standard, an optical fibre composite overhead ground wire) is a type of cable that is used in overhead power lines. Such cable combines the functions of grounding and communications. An OPGW cable contains a tubular structure with one or more optical fibres in it, surrounded by layers of steel and aluminium wire. The OPGW cable is run between the tops of high-voltage electricity pylons. The conductive part of the cable serves to bond adjacent towers to earth ground and shields the high-voltage conductors from lightning strikes. The optical fibres within the cable can be used for high-speed transmission of data, either for the electrical utility’s own purposes of protection and control of the transmission line, for the utility’s own voice and data communication
Prior planning for the installation of the OPGW cable is performed by monitoring the line, taking into account the following parameters:
- Reel length: The OPGW reel lengths are determined based on the following considerations: the position of the tension towers, tower access, the distance between supports and crossings of other lines, roads, railways, routes, services and other obstacles.
- Splices: The splice point locations depend on the maximum available length of OPGW and on the tower locations and accessibility.
Prior to the OPGW cable installation, each optical fibre is verified using OTDR.
As a rule, one drum at a time of OPGW cable is installed. In case of any difficulties, the SRC supervisor has to be contacted. He will give the correct guidelines to proceed with the OPGW cable installation. The detailed procedure is linked here for preview.
After stringing and the optical measurements after installation the OPGW cable will be spliced. After splicing, each joint is optically verified using OTDR in order to ensure that the attenuation values are within the required margins.
After installation, a final measurement of the transmission characteristics is the values are duly recorded. A copy of this is submitted to the customer.