With the thrust on renewable energy, efficiently integrating such intermittent sources of energy is becoming a key priority for transmission system operators. A case in point is the state transmission company, Gujarat Energy Transmission Corporation Limited (GETCO).
The share of renewables in the state’s power sector is expected to grow significantly, with the government targeting to have over 17 GW by 2022. Gujarat currently has an installed renewable energy capacity of around 7 GW, which accounts for around 29 per cent of the total installed capacity. In terms of power generation, wind and solar make up for 9.18 per cent and 1.97 per cent share, respectively.
In order to keep pace with this projected growth, GETCO has been working on a number of initiatives to develop state-of-the-art tools along with real-time data of renewable energy generation. Key among these have been the setting up of a dedicated renewable energy management centre (REMC), equipped with forecasting and scheduling tools and real-time monitoring of renewable energy generation, for ensuring grid stability; and inclusion of a number of grid modernisation technologies such as automatic demand management system (ADMS), SCADA with energy management system, and wide area monitoring system (WAMS) with phasor measurement unit (PMU).
“Gujarat has adopted many IT- and OT-based technologies and solutions for capturing real-time data, facilitating decision-making as well as grid monitoring and analysing grid behaviour in real time,” says a senior company spokesperson.
Overview and existing infrastructure
Set up in 1999, the company is responsible for electricity transmission in the state. It is a subsidiary of GUVNL, which is wholly owned by the Government of Gujarat. Gujarat has the largest transmission network among states. During 2018-19, the transco helped meet a maximum power demand of 18,221 MW.
GETCO has been expanding its transmission network in keeping with the state’s growing power demand. Its transmission assets include 63,641 ckt km of lines. In fiscal 2019, the line length witnessed an increase of 41.56 per cent from the 44,956.49 ckt km line length that was put in service in fiscal 2012. The majority (51 per cent) of transmission lines are at the 66 kV level, followed by the 220 kV level (32 per cent) and 400 kV level (which accounts for the rest). The number of substations owned by the transco stood at 1,969 in fiscal 2019, an increase of 55 per cent over the financial year 2012. More than 90 per cent or 1,791 substations are at the 66 kV level, around 104 substations are at the 220 kV level, 58 substations at the 132 kV level and 16 substations at the 400 kV level. The company’s transformer capacity stood at 110,047 MVA as on March 31, 2018.
GETCO managed to achieve transmission line and substation availability of over 99.58 per cent and 99.87 per cent, respectively, over the past five years. A balanced growth in network with adequate reactive power compensation and efficient grid operations helped the company contain transmission losses to 3.72 per cent during 2017-18.
GETCO’s total revenue increased by 27.07 per cent, from Rs 29.33 billion during 2016-17 to Rs 37.28 billion during 2017-18. The utility’s operating expenditure increased from Rs 1.05 billion in 2016-17 to Rs 1.12 billion in 2017-18. Its net profit went up from Rs 1.06 billion during 2016-17 to Rs 3.75 billion during 2017-18.
The transmission network of Gujarat is designed and updated from time to time with latest technology to ensure the supply of safe, secure and reliable power. It is the first state utility to have commissioned a static synchronous compensator at the 220 kV Timbdi substation for mitigating the voltage variation issue in the Saurashtra region. Gujarat is the only state to have commissioned 10 reactors on the 220 kV side to meet over-voltage issues during low-load sessions.
A pioneer in SCADA implementation, Getco has installed this system to monitor, operate and control the transmission system of the entire state. It has implemented an ADMS, one of the most advanced solutions, in the country. The transco has put in place an outage management system and an e-payment mechanism for external stakeholders. GETCO has also implemented technologies such as substation automation system, gas-insulated switchgear and hybrid switchgear, high capacity conductors and high-temperature low-sag conductors.
The state’s renewable energy generation capacity is connected to about 190 pooling stations, also referred to as the point of common coupling (PCC)/point of injection. Variability of renewable energy generation in a high penetration scenario is, thus, a critical challenge for system operators to manage power system balance. The establishment of REMCs and real-time monitoring of renewable energy generation was envisaged as a primary requirement for grid integration of large-scale renewables.
The functionalities of an REMC include forecasting of renewable energy generation, generation of quality and reliability of renewable energy data, and geo-spatial visualisation of renewable energy generation. The REMC comprises data interface units at the grid substation, interconnecting substation and renewable energy developer’s pooling substation. The REMC can integrate SCADA systems of renewable energy developers, provided they support standard interface protocols. PMUs can be installed at critical substations where remote monitoring is required at each power frequency granularity level. The transco has engaged three forecasting service providers (FSP) for providing wind and solar generation forecast at the STU pooling station level as well as at the aggregated state level.
The development of analytics based on the PMU data from IIT Mumbai has also been taken up. This includes online oscillation mode identification (commissioned), state estimator (currently at the development stage), and dynamic security assessment (developed up to the prototype level).
Challenges and the way forward
Lack of accuracy of renewable energy forecasting, the need for capturing real-time data continuously, and deviation between forecast and actual renewable energy generation are some of the key challenges. Also, there are issues of managing harmonics and reactive power in the associated transmission network after connecting renewable energy generators. Another problem is the threat to cyber security of data and application, which is increasing day by day.
Looking at the growth of renewable energy in the state, grid monitoring along with action at the individual wind mill level, and wind farm/solar station pooling at the station level will be of utmost important for the transco to ensure safe and secure grid operation.
The transco’s future projects include monitoring weather and power generation data at the inverter level as well as at the wind mill level for monitoring & control.
It plans to upgrade energy accounting and scheduling software with disaster recovery facility, replace the existing energy accounting software, and introduce the multifactor authentication for energy accounting and scheduling software and automatic meter reading of all ABT meters). Further, Getco plans to appoint a service provider as a qualifying coordinating agency (QCA).
The transco is in the process of implementing WAMS Phase II at 62 locations (at 450 PMU installations) covering all 400 kV and major 220 kV interface points, and renewable rich pockets to enhance monitoring of the grid. Upgradation of analytics with implementation of WAMS Phase II PMU at the SLDC control centre is also being explored.
Going forward, technologies such as online replacement of conductor using robotics, and line patrolling and supervision using drone/mobile application would remain major focus areas. Further, onsite testing of LVRT/HVRT FRT is planned by the company.
Net, net, with the state’s energy landscape transitioning towards decarbonisation, the current and planned initiatives by GETCO are expected to create a seamlessly integrated low-carbon energy system.