The Gujarat Energy Transmission Corporation (GETCO) has emerged as a leading state transmission utility in recent years owing to its pioneering efforts in technology adoption and operational performance improvement. It was the first utility to adopt hybrid gas-insulated switchgear (GIS) technology. In addition, the transco has implemented substation automation, optical ground wire (OPGW), and supervisory control and data acquisition (SCADA). GETCO has also drawn up a roadmap of smart grid technologies and solutions to bring down operational costs in the long run.
The utility has implemented a host of IT and operational technology (OT) measures in the past couple of years to improve its functioning and efficiency.
Smart technologies
The utility undertook the mapping of all technical and business functions, and identified many smart grid solutions to make these functions more efficient. A smart grid cell under the engineering department has been formed to implement smart grid technologies with a concrete action plan. The following are some smart grid technologies that GETCO has adopted in the past few years.
Substation automation system
A key technology adopted by GETCO is the substation automation system, which aims at reducing human interface at substations for manpower optimisation, besides improving the reliability and accuracy of operations. Some of the substations that have these systems are the 220 kV Shapur, 220 kV Lalpar, 220 kV Kangasiyali, 220 kV Jarod, 220 kV Vallabhipur and 220 kV Sartanpar, 220 kV Atul, and 220 kV Suva substations.
As a step towards digitalisation of substations, the utility has installed optical current transformers (OCTs) and merging units in substations. OCTs are comparatively safe to operate with no flaming or explosion risk, and are lightweight and compact. GETCO has completed two pilot projects in this regard.
Smart communication technology
In order to do away with obsolete technology and have a bigger bandwidth for data transmission, GETCO is in the process of laying OPGW (5,270 km) and replacing the conventional power line carrier communication (PLCC) with fibre optic terminal equipment. In this technology, the teleprotection equipment is used to protect signalling and prevent inter-tripping of transmission lines. Teleprotection signals and commands travel via OPGW rather than line conductors as in the case of PLCC. As of January 2017, about 710 km of OPGW has been laid by the utility.
GIS and hybrid switchgears
The utility has also adopted GIS and hybrid switchgears for high reliability and availability. These assets are maintenance-free and are economical on a life cycle cost basis. It has commissioned a 220 kV hybrid switchgear at Sartanpar (Morbi) and a 220 kV GIS at Atul.
High performance conductors
GETCO has installed AL-59 conductors for 400 kV and 220 kV lines after an internal study of existing tower designs. Since they operate at high temperatures, high temperature low sag conductors offer much higher current carrying capacity (thermal rating) vis-à-vis an equivalent size aluminium conductor steel reinforced without appreciable increase in sag.
Web-based Transmission asset management system
GETCO has mapped all its assets and carried out diagnostic tests to find the root cause of equipment failure. Based on the analysis of the failure rate and operational performance of the equipment, it has implemented a web-based transmission asset management system to map assets. The system helps in monitoring the entire life cycle of equipment, and renovation and modernisation planning.
Some of the smart grid technologies that are under implementation in GETCO are full digital substation with process bus, conversion of the conventional protection system into a substation automation system, line monitoring unit to assess the maximum line capacity, SF6 switchgear with SCADA at 11 kV to optimise the manpower for operation, static synchronous compensator at the distribution level for dynamic reactive power and power transformer with ester oil at 66/11 kV class voltage.
SLDC modernisation
GETCO has undertaken a host of initiatives to modernise the state load despatch centre (SLDC). It has time and again collaborated with academic institutions such as the Indian Institutes of Technology (IITs) and National Institutes of Technology for resolving grid operation issues and the optimum utilisation of transmission infrastructure. The utility has carried out a research and development project with IIT Bombay for the development of an analytics software for online power system oscillation mode identification, hybrid state estimator, and dynamic security assessment with voltage stability. The aim of the online oscillation mode identification software is to identify oscillation modes and analyse them for severity in ambient and event scenarios. Dynamic stability analysis is necessary mainly because the grid is integrated. Any disturbance in one region can result in a blackout in another grid area as well. The dynamic security assessment system identifies the system capability against any contingency, possibility of contingency and possible remedies. The major advantage is the availability of these security tools in real time with a dynamically changing system. GETCO has also covered 400 kV and 220 kV transmission lines under geographic information system, leading to better network planning and asset management.
GETCO has a full-fledged SCADA system for grid monitoring and control in real time. This is done through remote terminal units, but it poses limitations in terms of speed and data processing. Analytics are being developed to analyse, correlate and check grid parameters to monitor the reliability and stability limit of a system in real-time operations.
Wind power is being scheduled according to the forecast received from the wind station. SLDC Gujarat has engaged REConnect Energy Solution Private Limited as the forecasting service provider (FSP) for wind generation forecasting for two years. The SLDC provides the static data (one time) and variable data (weekly availability based on tariff meter data and real-time SCADA data) to the web portal. The FSP in turn provides week-ahead forecasting, day-ahead forecasting and real-time forecasting. Starting from 0000 hours, 16 revisions are allowed in each one-and-a-half-hour time slot. The utility is also utilising wide area monitoring system (WAMS) for power system operations. WAMS aims to facilitate highquality, system-wide measurements for enhanced monitoring, control and protection applications in a large power system. A key feature of this technology is the precise synchronisation of the measurements using global positioning system satellites. This feature also allows for the direct measurement of phase angular differences between phasors at distant locations in a power grid.
Conclusion
GETCO has drawn up a blueprint of transmission projects to be executed during the Thirteenth Plan (2017-22), based on anticipated load growth in the domestic, industrial, agricultural and commercial segments. It has planned network expansion with a focus on key state and national infrastructure projects like the special investment regions, the Delhi-Mumbai industrial corridor, railway container projects, automobile hubs, and metro and port projects. With expansion in full swing, the transco is actively checking the viability and compatibility of new technologies with its system.