Testing and measurement (T&M) has immense significance in the power industry as supply reliability depends on the smooth performance of all interconnected systems. Unless these systems are tested and maintained at regular intervals, breakdown of any of their components has the potential to trigger a grid collapse. Besides reliability, T&M aids in safe operations, compliance with standards and optimisation of asset lifetime.
With significant capacity addition across the generation, transmission and distribution (T&D) segments, the need for T&M of critical equipment has increased considerably. The installed generation capacity has increased from 267 GW in 2014-16 to 370 GW in 2019-20, recording a compound annual growth rate (CAGR) of 6.7 per cent. The aggregate transmission line length at 220 kV and above voltage stood at 425,071 ckt. km as of March 2020, growing at a CAGR of 6.3 per cent in the past five years. Meanwhile, alternating current (AC) transformer capacity stands at 942 GVA and high voltage direct current (HVDC) transformer capacity stands at 25,500 MW, recording a CAGR of 10 per cent and over 13.5 per cent respectively between 2014-15 and 2019-20. In the distribution segment, the total line length grew at a CAGR of 4.11 per cent to reach 11.12 million ckt. km as of 2018-19, as per Power Line Research. Besides strong capacity addition, the power sector is witnessing a technology transition with the addition of renewables to the power mix, utilities’ focus on digitalisation and automation, as well as introduction of electric vehicles and distributed generation.
Generation utilities are increasingly diversifying into renewables as well as looking at ways to reduce emissions from their thermal power plant fleet. In line with the environment ministry’s norms for emission control, T&M of sulphur oxides (Sox), nitrogen oxide (NOx) and particulate matter control equipment has gathered pace. Gencos are deploying combustion monitoring systems that enable them to view a range of furnace conditions in a power plant. Modern combustion monitoring systems are also equipped with continuous carbon monoxide and NOx emission monitoring capability as well as automated controls needed to improve fuel performance. NTPC Limited is working with the Central Pollution Control Board (CPCB) for the installation and commissioning of continuous ambient air quality monitoring stations (CAAQMSs). In February 2020, NTPC signed an agreement with the CPCB to provide financial support of Rs 800 million for the installation of 25 CAAQMSs across six states and three union territories. Data garnered from these stations will be used as inputs for air quality index evaluation for the respective cities.
Likewise, T&M of renewable energy equipment including solar cells, photovoltaic (PV) modules and wind turbine generators is also in considerable demand. Recently, in March 2020, NTPC invited applications from eligible domestic and international agencies for the empanelment of consultants for carrying out third-party quality inspection and testing of solar PV modules.
T&M is crucial for transmission utilities, especially as they are moving to higher voltages and deploying high-value equipment such as transformers, rectifiers and HVDC systems. For instance, Power Grid Corporation of India Limited (Powergrid) is implementing 1,200 kV ultra-high voltage (UHV) AC and ±800 kV HVDC projects, while state transmission utilities such as Maharashtra State Electricity Transmission Company Limited, Rajasthan RajyaVidyutPrasaran Nigam Limited and Uttar Pradesh Power Transmission Corporation Limited have progressed to the 765 kV level. Many discoms are taking steps to implement the high voltage distribution system to improve the high tension-low tension ratio in their networks.
T&M of smart meters is also an emerging area of focus in the distribution segment as accurate measurement of energy is crucial both for consumers and service providers. With the government’s mandate to replace all conventional meters with prepaid smart meters in the next three years, the need for laboratories to test smart meters is expected to increase significantly. In addition, T&M of electric vehicle chargers and batteries, microgrids, and underground cables is likely to be in greater demand in the coming years.
Key trends and developments
The National Accreditation Board for Testing and Calibration Laboratories (NABL)-accredited laboratories such as the Central Power Research Institute (CPRI) and the Electrical Research and Development Association (ERDA) are key bodies for testing and certification of power equipment in the country. They perform several activities including the evaluation of extra-high voltage (EHV)/ultra-high voltage (UHV) equipment; high power short-circuit testing of transformers, circuit breakers and other T&D equipment; power system studies; and transmission line tower and accessory testing. Besides, testing is undertaken by certain original equipment manufacturers, vendors and third-party testing agencies.
Over the past year, the CPRI has conducted over one million evaluations on samples sent by the central, state and private power utilities as well as domestic and international electrical equipment manufacturers. In the recent past, CPRI has also upgraded the accuracy test facility on potential and current transformers as per national and international standards. The CPRI is setting up an additional regional testing laboratory in Nashik, Maharashtra. The foundation stone for the laboratory was laid by the power minister in January 2019. The unit laboratory will have testing facilities for transformers, miniature circuit breakers, contactors, switch fuse unit, panels, bus ducts and current transformers. The central government has sanctioned the establishment of research and testing facilities at Nashik with an outlay of Rs 1,153 million. The completion of this laboratory will facilitate utilities and electrical industries in the western region as they can test their products close to their manufacturing units.
Recently, in March 2020, GE Steam Power India signed a deal worth $32 million with the CPRI for supplying two 2,500 MVA short-circuit generator systems. The addition of two short-circuit generators to the existing one in the CPRI’s High Power Laboratory in Bengaluru will upgrade its capacity to 7,500 MVA, making it the highest capacity short-circuit capacity laboratory in India. The scope of the project includes supply, installation, commissioning and testing of two sets of 2,500 MVA short-circuit generators with super excitation, driving and auxiliary systems, ready for parallel operation in synchronisation with their existing 2,500 MVA generator to yield short-circuit powers of 2,500 MVA, 5,000 MVA and 7,500 MVA respectively.
Meanwhile, the ERDA is setting up a testing laboratory at Muradnagar in Uttar Pradesh. An MoU for this was signed between the ERDA and PashchimanchalVidyutVitran Nigam Limited (PVVNL) in February 2019. The laboratory will be equipped with routine and acceptance testing facility of equipment including distribution transformers, instrument transformers, energy meters, insulators and cables. The laboratory will help PVVNL and other Uttar Pradesh discoms to test equipment in lesser time and lower overhead cost. In 2018, the ERDA also established a testing facility for IEC 61850 communication protocol testing for intelligent electronic devices (numerical relays), the only facility in the country.
Further, NTPC, NHPC Limited, Powergrid, the Damodar Valley Corporation and the CPRI have together set up the National High Power Test Laboratory at Bina, Madhya Pradesh. The laboratory provides transformer testing (short-circuit testing) facilities in the country. With this, they no longer have to send large power transformers (especially 100 MVA and above) to overseas testing laboratories such as KEMA in the Netherlands and CESI in Italy.
Key T&M strategies
The T&M market has evolved over the years. In addition to routine and type tests, diagnostic tests are being conducted by utilities to assess the health of the operating equipment. Separate tests are conducted for overhead, underground and EHV lines in the T&D segment. In overhead lines, punctures in the insulation of live wires can be monitored using punctured insulator detectors. Other online or live monitoring methods include distributed temperature sensor and sheath current monitoring. To monitor the health of EHV transmission systems, aerial line patrolling is increasingly being deployed. Helicopters and drones equipped with light detection and ranging sensors, thermovision cameras, corona cameras and high resolution video and digital cameras are deployed for identifying transmission line defects. The health of underground cables can be assessed with very low frequency testing. To bring down the high failure rate of distribution transformers, utilities are making acceptance tests more stringent. Power transformers are tested at NABL-accredited testing laboratories such as the CPRI and ERDA. For distribution transformers and energy meters, only percentage/sample testing is done at NABL laboratories, while 100 per cent testing is done at the utility level.
Issues and the way forward
Of late, power quality has become a focus area in the power sector and, therefore, equipment for power quality measurement is required. It is important to undertake power quality monitoring at suitable locations in a phase-wise manner. Further, there is a need to ramp up T&M infrastructure, especially given the long testing time at NABL-accredited laboratories and the limited availability of slots in the CPRI and ERDA.