OPGW stands for Optical Ground Wire. Earlier we used shield wire / sky wire / Ground Wire for protecting the high voltage phase wires form lightening strikes on the Transmission Tower. But today, we use OPGW as shield wire /sky wire / ground wire. It is designed to replace traditional static / shield / earth wires on overhead transmission lines with the added benefit of containing optical fibers which can be used for telecommunications purposes.
OPGW serves two purposes:
- One is to protect the high voltage phase wire on the tower from the lightning strikes.
- Another very important function is transmitting data. It is used form data telemetry from Generating Station to the load dispatch center.
Construction of OPGW:
OPGW is optical fiber composite ground wire. This cable contains a tubular structure having one or more optical fiber and surrounded by layers of aluminum and steel wires. This layer of aluminum and steel wires serves to connect the tower to the ground. The optical fiber within the cable is used for the high speed data telemetry between the utilities or sold to some third parties for high speed fiber interconnection between the cities. For example, POWERGRID with its brand name ‘POWERTEL’ in Telecom business is the only utility in the Country having overhead optic fiber network using Optical Ground Wire on power transmission lines.
A simple schematic diagram of OPGW is shown below.
This cable is designed in such a way to withstanding the mechanical stresses applied to overhead lines due to environmental factors such as wind and ice. It must also be capable of handling electrical faults on the transmission line by providing a path to ground without damaging the sensitive optical fibers inside the cable.
Application of OPGW:
As discussed earlier, it is used as sky wire as well as for data telemetry.