Planning on Improving The Availability of Egat's Optical Networks Utilizing Opgw

The optical networks have been deployed by several power utilities to support the control and operation of power system. Particularly in Electricity Generating Authority of Thailand (EGAT), we have utilized the Synchronous Digital Hierarchy (SDH), based on time division multiplexing (TDM) technology and it has been proven of its reliability, availability and survivability for almost two decades. The designed SDH network can offer recovery of communication link within sub-50 milliseconds which has been satisfied for power utility backbone communication infrastructure. Although the trend of communications technology is moving toward to utilize packet network, some operation application such a teleprotection system stills depending on TDM technology due to the requirement on the high dependability, security and short transmission time of teleprotection signals.

The typical SDH network consists of data plane and management plane separately. In the data plane SDH transmits payload data and in the management plane, the separated network management system (NMS) provides network and network-element provisioning and performance management. Improvement to the mentioned technique, SDH equipment can be enhanced with the use of control plane as described in the standard from ITU-T Recommendation G.8080; automatic switched optical network (ASON). This enhancement can add the advantage on implementing an optical mesh network that can improve the availability over a typical ring network. Several SDH ring networks have been deployed in EGAT utilizing Composite overhead ground wire with optical fiber (OPGW).

This paper is focused on the improvement on EGAT's optical networks in metro and vicinity areas. It is due to the fact that the connectivity of OPGW among EGAT's substations in metro and vicinity areas has been increased and it is good opportunity for us to integrate the control plane technology for new SDH network within our procurement and later will be implemented in those mentioned areas. Our proposed planning involves a building of mesh networks for given nodes (substations) and given available number of fibers inside OPGW. At the first stage of this plan, the network design is created by using the optimization tool (a linear programming) to obtain the best solution for a full mesh network that all nodes are connected by one another with the objective of a least use of optical fibers. However, to be realistic, in case that the budget may be limited, the constraint on limited number of links is added for the second stage of the design and finding out the solutions.

The result from both ideal and more realistic solutions are compared in this study which will be very useful information for network planners in their further design and procurement process. Although, the acquisition of equipment may differ from the optimized solutions, the information on how far the procurement is apart from the best one can be shown and compared for administrator's consideration. Moreover, the mesh network planning can be useful for the enhancement of optical networks supporting the power distribution network where there are more substations and fiber-optic connections among them than the transmission network.