India has a large number of transmission and distribution (T&D) projects in the pipeline. As per the Central Electricity Authority, around 123,000 ckt. km of transmission lines, 400,000 MVA of AC transformation capacity and 13,000 MW of HVDC substations are currently under construction and will be commissioned in the next four to five years. The interregional transmission capacity is proposed to be increased from 78,050 MW at present to 118,050 MW by 2022. In addition, several distribution utilities are planning to strengthen and augment their networks, and install smart meters as part of the various government schemes.
In the backdrop of such large capacity addition and the growing deployment of advanced technology in the sector, the demand for testing and measurement (T&M) of critical equipment like switchgear and transformers is expected to rise. Further, the increasing reliability and safety concerns call for new maintenances strategies and T&M techniques. Therefore, utilities need to augment and upgrade their testing facilities. They also need to keep abreast with the latest technologies and practices in the T&M space to ensure accuracy and compliance of equipment with all applicable standards and regulations.
T&M plays a significant role in the power sector. It helps certify, calibrate and assess the quality and reliability of power equipment. 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. Notable 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 regularly conduct testing and certification of T&D equipment. They offer facilities such as 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.
As the country’s transmission system is gradually moving to higher voltages, adequate testing facilities for UHV/EHV equipment and devices are required. Power Grid Corporation of India Limited has taken the lead in this regard with the development of the 1,200 kV UHV AC National Test Station at Bina, Madhya Pradesh. The utility has commissioned 1,200 kV single and double circuit transmission line sections and associated 1,200 kV bays as part of a pilot project using indigenously developed equipment. These equipment, including the 1,200 kV transformers, were developed by Bharat Heavy Electricals Limited, CG Global (formerly Crompton Greaves), ABB, Siemens, Toshiba, etc. In May 2016, power flow through the 1,200 kV National Test Station commenced successfully. The test station would enable manufacturers and transmission utilities to conduct various field tests to develop field-proven equipment for 1,200 kV systems and gain initial operational experience.
In the distribution segment, loss reduction, replacement of ageing infrastructure and deployment of smart grid technologies are the key factors driving the demand for new equipment. The T&M market is focusing on equipment categories such as transformers, switchgears and meters. Transformer failure is among the leading issues that utilities are grappling with. The distribution utilities are yet to take significant steps in the T&M of energy meters. While regulatory stipulations require third-party testing of meters in distribution circles, not many states have made progress in this regard. In many states, meter testing still comes under the ambit of electricity inspectorates. Further, with the huge demand for smart meters, utility concerns about safety and performance hazards associated with these meters are on the rise. Therefore, smart meter testing has emerged as a new focus area in the T&M of meters.
Discoms cannot set up T&M facilities for all products that they buy and are thus have to rely on the testing facilities of vendors or independent test laboratories. Therefore, discoms need to verify the reliability and quality of equipment at the time of approving the vendors. Since detailed testing of each of the delivered products is not possible, it is important to select an appropriate and reliable vendor, evaluate the samples thoroughly, and undertake failure analysis. Meanwhile, the launch of smart grids has created demand for new technologies in the T&D sector, which implies new areas of research and development in the T&M industry.
Equipment condition monitoring
Along with conventional equipment testing practices, diagnostic testing and preventive maintenance practices are gaining prominence among T&D utilities. Condition-based monitoring systems are deployed to check on critical power protection systems. Utilities need to make decisions regarding power network equipment, maintenance schedules, replacement of existing assets and addition of new ones on a regular basis. This not only has a significant impact on their operational performance but also affects costs. To facilitate this decision-making process, T&D utilities undertake equipment condition monitoring (ECM), which provides valuable data on the working condition of select grid components to both operators and asset managers. ECM involves the use of condition-based monitoring systems for assets through a combination of intelligent electronic devices, smart sensors, open protocols and head-end software.
ECM can be conducted through manual inspections (periodic visual inspections), continuous monitoring with a change-in-status/condition alarm as the only output (low-level alarm), periodic automated monitoring (connection of portable analysis instruments), or continuous online monitoring (full-time measurement of parameters to assess the condition of equipment while in service). Under ECM, data is analysed through innovative algorithms and knowledge modules, which enables accurate evaluation of condition information and predictive analysis. It can be seamlessly integrated into the existing substation communication and visualisation infrastructure.
In addition, ECM analyses data to help identify potential equipment failures and undertake maintenance planning for similar equipment. ECM can also help determine the remaining life of the equipment by employing residual life assessment techniques. ECM solutions can be customised as per the specific requirements of various components of the electricity supply network ranging from transformers and switchgear to overhead lines and cables
With predictive analysis, outages can be reduced. This improves reliability as reflected in lower SAIDI (system average interruption duration index). In addition, ECM helps bring down operations and maintenance costs via condition-based maintenance, under which an asset is serviced only when required. It can also extend the lifespan of an asset, thus reducing capital replacement costs. ECM reduces the workforce requirement, and helps achieve greater efficiency and higher corporate savings. Apart from this, it improves workforce safety and power quality to ensure employee retention and customer satisfaction. Besides, ECM plays a role in verification tests by reporting installation conditions. It automates the collection and preservation of baseline condition data and characteristics. ECM also provides information on the prior condition of the equipment before a failure has occurred and prevents unsafe conditions for workers.
Issues and challenges
One of the key issues faced by utilities is the long testing time taken at NABL-accredited laboratories due to a large number of testing requests and the limited availability of such laboratories. As a result, errors have been observed in equipment testing done at these laboratories. In addition, obtaining NABL-accreditation for utilities setting up their own testing laboratories is a time-consuming process.
Further, 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 in collaboration with foreign players. As per industry experts, a star rating system of independent test laboratories should be developed. Further, product development teams and test laboratories should work together to undertake equipment failure analysis.