OPGW and Earthwire

Earthwire, OPGW and OPPC

Earthwires of overhead transmission lines will be fixed to the top points of the poles and primarily serve to protect the conductors from lightning and thus to increase operating safety because the necessity to shut off the facilities on short notice will be reduced.

Due to the trend towards central remote control and control of in-house facilities, such as power plants or switchboard plants, earthwires were successively being replaced by earthwires with integrated optical fibres. In addition, these OPGW (Optical Ground Wires) did not only serve for active lightning protection but also played an active role in data transmission. The large-area development of the OPGW network on the 110kV-400kV level helped to open up a new business field, namely commercial marketing of signal distances that are ultra-rapid and insensitive to disturbing factors and are, for example, used for the mobile phone network.

Depending on the structure of the optical fiber, a distinction is made between the following types:

  • OPtical Ground Wires:
    These metallic structures are very similar to the standard models of earthwires. Usually single wire strands will be replaced by capillary tubes made of special steel, in which the sensitive glass fibers are bedded in a gel filling as to be protected from shocks and impacts. Due to the mechanical structure of these OPGW, these types can absorb the whole tensile force.
  • All Dielectrical Self Supporting Cables:
    These non-metallic structures will be operated in electric autonomy from the overhead transmission line and mostly be conducted on the pole on the level of the phase system. Depending on the model, there are different ways to incorporate adequate drawing and reinforcing elements into the ADSS cables.
  • OPtical Attached Cables:
    These non-metallic structures, which are not self supporting, will be fixed to existing metallic earthwires by means of adhesive tapes, clips or spirals or simply wound around the wires.
  • OPtical Phase Conductors:
    If an overhead transmission line is not equipped with any earthwire but a communication distance is desired, phase conductors with integrated optical glass fibers will be used. These structures are mechanically structured like OPGW’s. The special feature of OPPC’s is that it will be necessary to install an electric by-pass in the area of a splice box or to uncouple the communication distance of the glass fiber from electric voltage in case of final span poles.

All the mentioned types of optical fibres require special suspension fittings and dead end fittings so that they can be fixed to the poles. Conventional compression dead-end clamps or simple suspension clamps cannot be used because they would impair or damage the sensitive glass fibres. For OPGW’s and ADSS cables, Mosdorfer has developed and tested a complete product portfolio of fittings on the basis of spiral fittings. As for ADSS applications on overhead transmission lines with shorter spans (e.g. medium voltage), roller fittings with different fastening variants are available.

In order to guarantee a highest possible degree of reliability of the communication lines, Mosdorfer can provide an extensive portfolio of accessories, such as vibration dampers.