Energetica India Magazine: september 2020

due to aging or corrosion, regular paint- ing of the towers is necessary. Many of such paint jobs do not last long enough. An eco-friendly, low solvent based, high thickness coating with high solids, high- build paint for weathered galvanized and previously painted structures is recom- mended. This is a modified linseed oil, metallic and ceramic pigmented coating designed for maximum corrosion pro- tection over minimal surface preparation which can be provided both above and below grade structures based on the ne- cessity. This coating can easily last for upwards of 10 to 15 years and provides excellent corrosion prevention. This way, the utility can be assured of longer work- ing life of the infrastructure with enhance- ment of the power carrying capacity with very low additional investment. Power Flow Controller: There are situations in the meshed trans- mission network where parallel circuits (either at different voltage or of different length – often a case due to one of the lines going through a LILO), see uneven loading. Thus, one of the circuits may see overloads while other circuit(s) re- main underutilized. This happens as different circuits offer different imped- ance in the circuit, and current takes the path of least impedance. Such situations are very frustrating, as they do not allow the investments already made (e.g. new lines) to be utilized effectively, thereby rendering the investment useless. Power flow controller (PFC) comes to rescue in such situations. Scalable pow- er flow control technology enables each power line to dynamically vary the ef- fective impedance of a line and provide control to transfer more or less power on the line, based on the real-time needs of the grid. This helps Grid operators to transfer higher power using the existing infrastructure they already have. PFC is an SSSC, which is scalable, modular, voltage agnostic, bi-direction- al FACTS solution which can regulate the power flow of transmission line, by increasing or decreasing the line reac- tance and thus by pushing or pulling the power to the other connected lines in any meshed network. The technology solution is deployable within substations, on towers, or on a mobile platform. Voltage Upgrade : Voltage upgrading can help to achieve much higher power transfer capability with reduced electrical losses and in- creased utilization of the existing corri- dors. Challenges in securing new ROW corridors are well known, which lead to project delays and unplanned cost in- creases. Increasing the voltage rating of overhead lines is possible if necessary electrical clearance is achieved. This can be planned with proper survey and suitable measures such as insulated cross arm, monopoles, special design of towers. Addition of higher voltage bays at terminal substation can be done if space is available or new substation can be built in vicinity of existing substation. While upgrading a corridor, maximum utilization can be achieved by building MCMV lines as well. Thus, the power car- rying capacity of a line corridor can be increased upwards from 4 times to 10 to 20 times. This can completely transform the corridor(s) and open new ways to look at and plan the networks. Another great advantage is that the un-certainties around securing new ROW are drastical- ly reduced, which means that projects can be expected to get completed on time. While, specific design and solution would depend upon existing situation and line details; a solution with insulat- ed cross arm is explained in more detail hereinafter. Line upgrade with Insulated Cross Arm: Use of insulated cross arm can help to upgrade the line voltage, while retaining the existing tower & foundation with few modifications. This is a great solution and can lead to multiplying of corridor capacity by multiples in quick time. Among the key benefits of composite In - sulated cross-arms is that insulator swing under windy conditions is reduced to a minimum. Insulated cross arms replace existing steel cross-arms and suspend- ed vertical insulator strings on traditional lattice towers, thereby enabling conduc- tors to be attached directly to the cross- arm giving space and clearance margin to go for tower upgrade solutions. This combined with HTLS conductors with low sag performance help achieve volt- age upgrade, thereby improving power transfer capacity while still not infringing ground clearances. All the above solutions are already part of CEA’s Transmission planning Guidelines. Some of the solutions like reconduc- toring have been deployed better than other solution in India. It is however con- sidered that all these solutions if consid- ered during planning stage by network planners, can go a long way to maximize utilization of existing transmission assets and corridors, while giving the best in terms of time, space and cost, as com- pared to building new lines to meet grow- ing loads. Figure 6 : Congested corridor of the line Figure 7: Rusted member of the tower structure 50 energetica INDIA- September_2020 POWER SECTOR