The demand for reliable power equipment has increased significantly in recent years. The reliability and quality of power depends on the health of equipment such as conductors, transformers, switchgear and meters. If any equipment in the power value chain breaks down, grid security would be compromised, impacting electricity supply to consumers. Therefore, testing and measurement (T&M) of power equipment is critical for ensuring safe operations, accuracy and reliability of equipment, and compliance with the standards. It also helps in maximising the useful life of assets.
With significant capacity additions in the transmission and distribution (T&D) segment over the past few years and the growing adoption of advanced technologies, the demand for T&M of critical equipment is also increasing. The country’s transmission line length stood at 413,407 ckt. km as of March 2019, recording a compound annual growth rate (CAGR) of 7.25 per cent between 2013-14 and 2018-19. The alternating current and high voltage direct current (HVDC) substations capacity also increased significantly during this period to 877,163 MVA and 22,500 MW, recording CAGR of 11.15 per cent and 10.75 per cent respectively. Meanwhile, the total distribution line length stood at 10.9 million ckt. km as of 2017-18, recording a CAGR of 4.85 per cent between 2013-14 and 2017-18. The transformer capacity (at 33 kV and below) is estimated at about 789,000 MVA, growing at a CAGR of 8.52 per cent during the same period.
In addition to network growth, the technological landscape in the T&D segment is witnessing growing automation of substations, remote grid operations, and implementation of digitalisation initiatives. T&D utilities are moving to higher voltages. Power Grid Corporation of India Limited (Powergrid) is implementing 1,200 kV ultra high voltage alternating current (UHVAC) and ±800 kV HVDC projects, while state transmission utilities (STUs) like Maharashtra State Electricity Transmission Company Limited, Rajasthan Rajya Vidyut Prasaran 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.
The growing renewable integration and setting up of electric vehicle (EV) charging infrastructure requires further strengthening and augmentation of T&D networks. Advanced devices such as static synchronous compensators (STATCOMs) and static VAR compensator (SVCs) need to be installed to provide reactive power support to the grid both under steady state and dynamic conditions. Also, smart metering has emerged as a key focus area in the distribution segment with over 35 million smart meters expected to be installed under various government schemes. Overall, the demand for T&D equipment such as towers, transformers, conductors, switchgear and meters is expected to stay robust in the coming years.
In this backdrop, T&M will play a significant role in ensuring reliability and safety of electrical installations. In order to protect the interconnected power systems from cyberattacks, utilities need to ensure that their existing T&M facilities are expanded and upgraded with the latest technologies.
The T&M market comprises original equipment manufacturers, vendors and third-party testing agencies. Many equipment manufacturers and utilities have set up advanced testing facilities for ultra high voltage (UHV)/extra high voltage (EHV) systems, transmission towers, cables, meters and advanced switchgear. The National Accreditation Board for Testing and Calibration Laboratories (NABL)-accredited labs such as the Central Power Research Institute (CPRI) and the Electrical Research and Development Association (ERDA) regularly conduct testing and certification of T&D equipment. They perform several activities including the evaluation of EHV/ UHV equipment; high power short circuit testing of transformers, circuit breakers and other T&D equipment; power system studies; and transmission line tower and accessories testing.
For the testing of high voltage equipment, NTPC Limited, NHPC Limited, Powergrid, the Damodar Valley Corporation and CPRI have together set up the National High Power Test Laboratory (NHPTL) at Bina, Madhya Pradesh. The lab will provide transformer testing (short circuit testing) facilities in the country. With this, they no longer have to send large power transformers (specially 100 MVA and above) to overseas testing labs such as KEMA in the Netherlands and CESI in Italy. In September 2017, NHPTL successfully conducted the online short circuit test of a 765 kV commercial transformer, becoming the world’s first laboratory to conduct online short circuit testing of 765 kV transformers. Powergrid is also undertaking long-term field operation and performance monitoring at the 1,200 kV National Test Station in Bina which was commissioned in May 2016.
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 operating equipment. They have also adopted automated test kits for numerical protection devices.
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 (LiDAR) 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. Along with conventional equipment testing practices, tests like sweep frequency response analysis and excitation for HV transformers, capacitance and tan delta measurement for other critical equipment, dynamic contact resistance measurement of breakers are being conducted by utilities.
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 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.
Given the increase in metering coverage with states striving to achieve 100 per cent metering across all consumer segments, meter testing has become a key priority for discoms. Further, utility concerns about safety and performance hazards associated with these meters are on the rise. While regulatory stipulations require third-party testing of meters in distribution circles, not many states have made progress in this regard. In February 2019, Pashchimanchal Vidyut Vitran Nigam Limited (PVVNL) signed an MoU with ERDA for setting up a testing laboratory at Muradnagar, Uttar Pradesh. The site testing laboratory will be equipped with routine and acceptance testing facilities for major electrical distribution equipment. PVVNL and other Uttar Pradesh discoms use this facility for acceptance testing of equipment purchased by them for quality assurance. In March 2019, the Gujarat Electricity Regulatory Commission (GERC) invited expressions of interest from NABL-accredited electric meter testing laboratories for empanelment by GERC as an independent third-party meter testing laboratory in the state.
In light of the growing role of communication in power systems, T&D utilities are realising the need for testing communication solutions. Optical ground wires are the communication backbone, and testing of these wires requires the introduction of new test kits. Protocol testing tools for Modbus, IEC 104, IEC 103 and IEC 61850 are needed. Utilities are also increasingly realising the need for mobile testing labs for equipment on the field such as distribution and power transformers and interface meters.
Further, power quality issues have increased in the power sector and thus equipment for power quality measurement is required. As per a report by the Forum of Regulators, it is important to undertake power quality monitoring at suitable locations. Since power quality measurements at all locations will entail huge investments, the report recommends doing this phase-wise. Power quality meters may be installed at select representative locations based on voltage level, type of consumers and significance of power quality. Discoms are also testing solar panels with the increasing uptake of rooftop solar projects. Mobile testing labs allow on-site testing of photovoltaic modules saving time and resources. In December 2018, DNV GL, the world’s largest independent energy advisory and certification body, launched its first on-site solar laboratory for the testing of PV modules in India. The new mobile service provides flash test/I-V curve measurement and electroluminescence testing for PV modules on site.
Issues and the way forward
The long testing time at NABL-accredited laboratories and the limited availability of laboratories like CPRI/ERDA are the key issue. Sometimes, mistakes are made at NABL-accredited testing laboratories, even in sensitive testing cases like sound transmission class rating tests and accuracy tests, due to overcrowding at the existing NABL-accredited testing laboratories. To resolve this issue, utilities need to upgrade the testing system in all its laboratories with state-of-the-art technology, and secure NABL accreditation for all its labs.
Further, strong equipment procurement policies are needed. In most discoms, procurement is made on the basis of the lowest price offered by vendors, which may lead to compromises on the quality of meters. Also, the limited availability of quality T&M equipment in India leads to a high dependence on imports. Thus, reliable and world-class T&M units need to be developed with technology sharing with foreign players. A star rating system of independent test laboratories can be developed as independent testing provides further validation of quality, safety and reliability.