EMERGENCY RESTORATION SYSTEM
ERS Tower – a solution that helps in reducing the outage time of transmission line… Column By : Mr. P. Barua – Supreme & Company
As a manufacturer of transmission towers and electrical hardware, we have been working for the last three years on developing a product which will make a big impact in the transmission line sector. The most important aspect of transmission line is to provide continuous and reliable power. But, these lines are subjected to several natural disasters like earthquake, flood, landslides and hurricanes. Power failure due to these scenarios make a severe financial damage to consumers, utilities and the power producing units. It is necessary that these transmission line utilities take precautionary actions to avoid and reduce these disruptions. Further, in order to address the increasing power demand, utilities are uprating their lines by reconductoring. However, this is problematic as the shutdown required for reconductoring cannot be provided as those lines are already invariably overloaded.
We planned on developing a solution which will help in reducing the outage time of transmission line. This led to the development of ERS Tower, an indigenous product of Supreme. It is a temporary structure designed to bypass the existing transmission towers of any voltage in any terrain. They will be used until the main line is reconductored or restored. The entire structure can then be disassembled and reused. Only a small outage will be required to bypass the main line to ERS.
The unique feature of Supreme ERS is that they are made of High Strength Steel. The fully standardized fabrication process of High Strength Steel has made it an economical, functionally reliable and structurally stable option. The savings due to reduced outage time far outweighs the cost of such ERS which is now substantially reduced with the use of steel. The entire design is made in such a way that the whole structure can be erected in few hours. Sections are made modular in order to ease transportation as the site may be very remote to carry the structure. There is no need for any civil foundation. Erection is made ease with the usage of Gin Pole which obviates the need of heavy machineries. Use of composite insulated cross arm will reduce the crossarm load on the structure and also the clearance required for insulator swing.
The tower is entirely supported using guy wires. Hence it is essential that all the guy wires are properly anchored to the soil. In a conference organized by CBIP, TATA Power published a work where they mentioned that they were unable to use a temporary structure for restoring the line because of the marshy soil condition which will not be able to take the mechanical load of the structure. Our team took this as a challenge and developed different kind of anchors that would support the structure in all soil conditions.
Our first project was to bypass an existing 132-kV transmission line in order to facilitate the construction of a nearby flyover. A line length of 1800 circuit metres, which passes through a residential and heavily crowded commercial area in Sector 2 of Vaishali, was at standstill and lying abandoned after completion of foundation works since January 2017 and waited for a shutdown for a minimum of 10 days, for completion of erection of 2 Nos. Multi-circuit Towers and stringing to follow.
There were several 11kV and 33kV along the line which was the major challenge for us at the time of stringing. The line was serving a large number of people and hence getting shutdown for bypassing the line was very difficult. UPPTCL provided the required shutdown, five days after the structure erection. After complete installation, there was a severe hailstorm but the tower withstood the same without any damage to it. The bypass line was in charged state for a month serving the utility’s customers who didn’t have to undergo suspension of service. This new experiment played a significant role in promotion of line uprating by re-conductoring of old lines without necessitating the need for new ROW. The key thing to be noted is that this is the first ever bypass arrangement made by an Indian Manufacturer on a High Voltage Transmission Line.
We were again given an opportunity by UPPTCL to bypass a 132kV line which was an hinderance for the completion of a 400kV line. This project was also quite challenging as the line route was having a flyover, river and a highway crossing. The project was executed in four days with only a line shutdown of 4 hours. We achieved a challenging feat of taking the bypass line and crossing the highway without making any disruption to the highway traffic. This exercise helped in completing a project which would evacuate 580 MW line where substantial investment was already made on 98% stretch of the line and associated substation would have remained idle for indefinite period.
With the success of our previous projects on our back, we were given a job of restoring an abandoned 400kV Quad Double Circuit line in Eastern India. The double circuit line was transferred to 3 sets of ERS tower with two towers in each set thereby forming a double circuit. There was no road access to the site. Survey and even transportation of materials to site was made using country boats. Rowing the boat with tower materials was difficult as the river current was increasing as the day progress.
Secondly, the span across the river was too long and hence it was necessary for us to install a tower in the middle of the river. Fortunately, the site survey made by our team found a sand dune in the middle of the river which was effectively used to install the tower. The real challenge started at the time of installing the anchors. Soil was too soft that it was not suitable for installing any type of anchors. Modular supports were specially designed for this considering the guy angle and ease for transportation. The long modular steel supports offer the large width that is necessary for both connecting the guy wires and also increasing the stability of the ERS tower.
Thirdly, we need to ensure that the conductor is not immersed in the river as it may add as an extra load on the conductor during stringing. Pulling the conductor while it is subjected to a heavy river current would have severely stressed the tower. In order to avoid such issues, water cans were tied on the conductor so that the conductor floats on the river. Only tension towers in ERS were used in order to reduce the sag and obtain the required vertical clearance across the river. Further, long rod insulators of 160 kN were used for attaching the guy wires to ensure the clearance between the phase and guy wire. Embankment was made using sand bags to prevent the erosion of the bank. As the tower will remain there for next three months, local people saw this as an opportunity and started cultivating crops over the sand dune.
Line was charged on 10th January, 2018 and will evacuate around 800-1000MW of power for the next three months with the help of ERS. Without ERS, this prolonged outage would have resulted in a serious economic loss to the utility.
Transmission line owners and electrical EPC contractors will be benefited the most by ERS. It is not a disaster management system alone. ERS can be used in places where there is a need for line reconductoring or re-routing of line. Duration of line outage can be reduced substantially with the use of ERS. Apart from power sector, ERS can also be used as a temporary telecommunication tower for big gatherings.
Our mission is to provide a safe, secure and uninterrupted supply of Electrical Power while observing health, safety, and environmental standard. We have significantly augmented the marketability and customer relevance of this technical innovation by combining it with a suitable business model. Traditionally, vendors for this product, based on Canada and US, were targeting only utilities with large networks who would have large inventory and a dedicated team doing periodic drills to be able to actually use the product once in a while for restoring. This made them out of bounds for a large number of stake holders who have periodic outages due to failure or reconductoring the line.
So, we adopted an innovative business model where rather than selling structure, we offer complete end to end solution. We take care of transportation, erection, supervision and disassembling of the structure. This saves the O&M, training and storage cost that are incurred by the customer in case they own the system. We are proud to inform that our ERS has helped in restoring more than 2000MW of power within the last 8 months. Currently, it is taking 5-6 days to transport our structures to the site and begin the erection works. Hence, we are planning on setting up storage units across India which enable us to start line restoration immediately.
We are discussing with major power corporations for Supreme to act as an electrical contractor for providing the ERS solution to them. In ELECRAMA 2018, we will be showcasing a demo model of our ERS which will help the customers to have an idea of what we are doing and what are the benefits that they get from it. We will be providing them with an insight of what we have accomplished so far and what we are planning to achieve in the next upcoming years.
