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Home » Cover Story » Strategic intersection of transmission lines to curb power losses

Strategic intersection of transmission lines to curb power losses

April 29, 2020 7:47 pm

Strategic intersection of transmission lines to curb power losses
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Development of the future transmission infrastructure in the country continues through the competitive route. Industry leaders discuss ways to have more efficient transmission lines and reduce power losses economically.

India has been witnessing tremendous demand for power supply from the past few decades, owing to the ever-increasing population, industrialisation, and urbanisation. The initiatives undertaken by the government considering the impeding requirement of the construction of additional substations and stabilised transformers in the earlier years contribute as primary driving factors in the development of Indian transmission line and transformer businesses.

Utilisation of EHV transmission lines in India

As in 2019, the usage of transmission lines, or the “average line capacity utilisation” is presently estimated at 30-40 percent across the country. This is in line with estimates of global national/provincial grids. Talking about extra high voltage (EHV) transmission lines and its consumption in India, Arun Sharma, Chief Operating Officer of Infrastructure Business, Sterlite Power walks us through the growth rate of EHV lines, which can be seen from the data given below (sourced from CEA/National Power Portal). Transmission lines have grown at a CAGR of 5.2 percent and transformation capacity has grown at a CAGR of 8.7 percent in the last two decades. As the grid has matured, we have also seen growth towards more high capacity/HVDC systems in the past 10-12 years.

He further elucidates on the Green Energy Corridor project which is said to be boosting the demand for transmission lines in India. India has been one of the frontrunners in the adoption of renewable energy (RE) as part of its energy mix. He says, “The Government’s RE capacity addition targets to meet 175 GW by 2022 and 450 GW by 2030 have led to significant action at the transmission front. Green Energy Corridor (GEC) is the name that has been given to the government of India’s plan for grid integration.”

The last 15-18 months has seen 23 transmission projects — with a project value of around `27,000 crores — come up for competitive bidding in two phases. This has greatly encouraged private developers’ participation. By some estimates, competitive bidding on tariffs for these projects has effectively reduced the cost of delivery of power to the consumers by about 35-45 percent.

In fact, Sterlite Power is already executing its first GEC project — Lakadia Vadodara Transmission Project Ltd. — that connects the wind energy zones of Bhuj in Gujarat to the load centres in Gujarat and Maharashtra.

Dealing with technical and market challenges

To ensure the safety of transmission lines, power transformers need protection from unexpected voltage or current. The moment there is an abnormal voltage, there is a huge electromotive force generated within the transformers. Sanjib Mitra, Country Head Sales – Transformer, Electrotherm India Limited says, “Transformers are not designed to withstand such force. Because of heat, the oil gets fiery quickly, and there is always a threat of transformer oil catching fire in a highly unlikely situation.”

In such a scenario, generally Buchholz & PRV are basic protections. OTI and WTI (protection devices provided in transformer marshalling box) are wired up to controlled station/SCADA units for generating alarm/trip signals to the upstream/downstream circuit breakers. However, in large power transformers, current transformers are used for restricted earth fault protection to safeguard any internal faults and differential protection to cover up cable/line faults including the transformer zone.

Whereas, according to Sharma, the current biggest challenge is fighting the outbreak of COVID-19. Being an “essential service”, the transmission segment is also facing its share of challenges, especially with regards to access to sites and movement of men and material. He adds, “But with the amended MHA order dated 16th April 2020 coming into effect, allowing essential construction activities related to power transmission subjected to appropriate precautions, we are hopeful that the situation will improve. It is important that development of the future transmission infrastructure in the country continues through the competitive route, which will ensure cost and time efficiencies being achieved while executing such projects of national importance.”

Further, linear projects like transmission are heavily dependent on active government support and streamlined process definitions. The execution timeline of 18 months for transmission projects catering to renewable energy projects further amplifies this challenge and complexity. To streamline state-level clearances for transmission projects, the appointment of a nodal officer at the state level could be very helpful. Similarly, having a Project Monitoring Committee at the Power Ministry level for a regular progress update and addressing inter-ministerial coordination issues could fast-track project implementation. While the ministries and regulators have been consistently in action, some aspects such as improving liquidity position of DISCOMs will greatly benefit the industry.

Whereas, Sharan Bansal, Director, Skipper Limited, says that it’s highly essential to detect defects or errors that arise in transmission lines, and the same can be done by following some key activities including:

Foundation activities like testing of civil materials involved with casting.

Testing of CA, FA, reinforcement steel, cement, water to ascertain their quality for their respective work. Checking the proportion of civil materials at the time of mixing through mixing machines, for example, checking weight of materials like Azex. After casting, checking the concrete strength (checking the crushing value) by NDT in a client-approved laboratory.

Also, it is necessary to keep a track of tower erection work and analyse back to back and diagonal measurement of stubs of foundation and after tower erection to check the verticality of tower through total station (TS). By TS, the positions of the tower and its deviation of angle, if any, can also be checked to ascertain the load on towers after stringing work.

Securing transmission lines and improving cost efficiency to reduce power loss

In today’s world of wirelessly connected devices and facilities operating at different levels of digital automation, cyberattacks are far a bigger area of concern than physical attacks. However, transmission lines are also vulnerable to natural disasters. These lines are critical and strategic national assets, and disruption may have serious implications. Adequate redundancy is critical for robustness of the grid. Noting the same, Sharma highlights that Sterlite Power is solving problems at the intersection of time, space, and capital. Access to reliable electricity transforms lives and should be a fundamental right for all individuals globally.
Sterlite Power has led the way in adopting the state-of-the-art global best practices and innovations in a legacy-driven power transmission sector:  
Aerial technology adopted for project execution: Helicopter stringing; Heli-crane based tower erections. Asset planning/monitoring using UAVs (drones): Automated inspection and data analytics; Services by unmanned aerial vehicles.

Design engineering and digital platforms: Tower and foundation designs, and route planning, elevation models and resource optimisation using digital platform. Extensive solutions for power utilities to tackle their network congestion challenges by providing solutions that upgrade and uprate corridor intensity. In Kerala, multiple upgrade solutions and innovative conductor designs have been deployed to increase the power flow capacity of the state transmission corridors by 15 times. Re-conductoring of 66 KV transmission line in “live-line conditions”.

Vertical substation design for solving space constraint challenges.

New conductor installed with a span of over 1 km across the River Ganga — the first in India. For monitoring performance and reducing power losses, SCADA has been widely used to monitor and control from one station, either through a twisted pair cable or through a multicore control cable; better is FO cables, which are used in power stations. Nitrogen system fire protection is recommended for prevention of accidental fire hazard in power transformers.

Nowadays, in almost all substations above 10 MVA, NIFPS system is connected with transformer by mechanical pipe line and nitrogen cylinders. Mitra says, “Smart annunciations connected in control system can generate fairly advance notice, which can prevent accumulation of large faults and thus save power transformers and associated cables.”

It is important that development of the future transmission infrastructure in the country continues through the competitive route.
Arun Sharma, Chief Operating Officer of Infrastructure Business, Sterlite Power

It’s highly essential to detect defects or errors that arise in transmission lines right from testing civil materials, CA, FA, reinforcement steel, and cement, and ascertain their quality for their respective work.
Sharan Bansal, Director, Skipper Limited

Transformers are not designed to withstand extra force, as the oil gets fiery quickly in extreme heat conditions and further increases the fire threat.
Sanjib Mitra, Country Head Sales – Transformer, Electrotherm India Limited

 

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