OPGW - A communication solution for Power Utilities

Any Power utility has to set up dedicated communication links connecting all its operating centers spread through out its geographical area. This network primarily conveys voice signals (conventional telephone conversations), data regarding the operating parameters of the system and electrical protection of transmission line. As on date this is achieved through Power Line Carrier Communication (PLCC) and Microwave. Microwave is weather Dependant and does see rare interruptions, but is expensive as the utility has to pay annual license fees. PLCC has a limitation as it can carry only narrow band signals.

The alternative is Fiber Optic based communication, which has phenomenal band width. For this purpose one has to lay the optic fiber physically connecting the end points. Since the electricity board has dedicated transmission lines Cris crossing the entire state, a scheme was thought of to exploit this "Right of Way" which is other wise lying idle.

In this scheme the earth wire ( a galvanized steel wire which is run on the peak of transmission lines) is replaced with a OPGW (Composite Optical Power Ground Wire) which serves the purpose of acting as earth wire and has an embedded stainless steel tube which carry a bunch of fibers.The transmission line terminates at Receiving stations or generating stations and at these locations the OPGW is terminated and the fiber carried to special equipments called Optical Line Terminal Equipments(OLTE). These OLTE are similar to the ones currently used by the major telecom companies and carry signals in the SDH format. ( An international telecom standard accepted across globe).

The signals of the utility which may start from their telephone exchanges or computer network such as Ethernet or their Data Commendation equipments called RTU(remote terminal unit) or connected to the SDH gateway through specialised equipment called Primary multiplexer at the sending end. At the receiving end these are again "dropped" out of SDH gateway through another set of similar equipment and connected to the exchange or ethernet.

Some of the major advantages of this system over existing comparable communication links of Electricity utilities are the phenomenal increase in band width at a low investment. With increased automation being taken by TNEB in terms of computerisation of billing and collection, accessing their main load center points and generating stations on Real time basis, this network will go a long way in providing fail safe & effective communication link.

Last but not the least - the replacement of existing earth wire typically should call for shutting down the concerned power lines. In this case M/s BGR Energy System, the agency executing this project on a turnkey basis are adopting a system called "live Line working" where they will replace the existing earth wire with optic fiber embedded Ground wire(OPGW) under live conditions, minimising inconvenience to consumers.

Once the Optic fiber is laid and commissioned, TNEB has in its asset a dedicated link which can be used by other state departments. TNEB can also lease out to outsiders after complying with the necessary regulatory compliance's.

Till recently PGCIL the central power utility has been implementing these schemes at the central level across states. TNEB's efforts is pioneering in this regard as this will connect their main data centers across the state with their own network