The emergence of novel paradigms in the distribution segment such as decentralised generation systems, net metering, energy storage, electric vehicles (EVs) and associated charging infrastructure is expected to upend the structural architecture of the industry. It is, therefore, incumbent upon the distribution segment to invest in smart grid infrastructure, smart meters, digital equipment and advanced technologies, in order to support the transition towards the future electric grid. Power Line presents a review of various technologies for the distribution segment.
Underground electricity cables are an emerging trend that is expected to gain traction over the short term, given the resilience of these cables during natural calamities and their inherent tendency to bypass right-of-way (RoW) problems and environmental roadblocks. Underground cables are being installed in several densely populated cities such as Chennai, Bengaluru and Bhubaneswar. Other benefits include ease of network expansion in densely populated areas and protection against theft. These cables entail minimum RoW and require fewer clearances. While underground power cabling is undoubtedly an expensive choice, demand continues to be driven by the need for reliable supply, safety and aesthetic considerations, and availability of clearances.
Smart meters provide real-time consumption data, in addition to information relating to several other parameters, which can enable utilities to acquire a precise view of the consumption. Therefore, smart meters can assist discoms in reducing high aggregate technical and commercial (AT&C) losses due to fraudulence and theft.
AT&C losses in India are currently around 20 per cent as a result of which discoms never get remunerated for 20 units sold to their consumers out of 100 units purchased by the discoms from generation and transmission companies. The installation of digital meters will certainly bring a greater degree of accountability and transparency into the system. Smart meters are capable of disconnecting the load of a consumer or sending an alert to the data centre if tampering is detected, enabling utilities to take necessary action. Also, daily energy reads enable daily energy audits to identify loss-making feeders and quickly take corrective action. Smart metering also gives the additional benefit of all data being available at one central location, without manual intervention, for the purpose of verifiable base lining and evaluating improvements made on various performance indices by utilities. Non-availability of authentic and verifiable data is one of the current roadblocks in the privatisation of discoms.
Recently, Tata Power Delhi Distribution Limited (Tata Power-DDL) began pilot studies on the installation of smart meters based on narrow band internet of things technology. It has already installed 230,000 smart meters based on radio frequency technology. The narrow-band technology will be capable of eliminating the interference and obstruction arising on account of public network congestion, facilitating smooth data flow through a dedicated channel. Many other discoms have also reaped the benefits of smart metering. These include North Bihar Distribution Company Limited, Andhra Pradesh Central Power Distribution Corporation Limited and Ajmer Distribution Company Limited.
Digitalisation allows equipment across the distribution grid to communicate with one other as well as the utility and/or consumer to facilitate better operations and maintenance (O&M) of the grid. Smart meters, intelligent electronic devices, IoT sensors and control and automation software are critical components of digital solutions. These components facilitate greater interaction between the customer and the utility, which may lead to higher and timely receivables. Consumers with decentralised microgrids consisting of rooftop solar, with power demand in the night and surplus power generation in the daytime, especially stand to benefit from a suite of digitally connected and smart solutions, comprising data analytics and real-time monitoring. Such systems can provide solutions for managing load, and timely purchase and sale of electricity. Discoms could consider offering installation and leasing of smart equipment to these microgrids and, in some cases, even managing it for their convenience.
Equipment technology trends
Distribution utilities continue to focus on deploying equipment that requires fewer RoW permissions and ensures greater safety in operations. The uptake of dry-type and K-class fluid-filled transformers, which are associated with lower failure rates, is expected to rise in the short to medium term, as they offer better protection against fire hazards, have reduced/no risk of leakage of insulation fluids and entail minimal maintenance. Discoms are also in the process of installing digital substations, which will integrate real-time data into the system and thereby facilitate reduced downtime and enhanced diagnostics, and avoid the cumbersome requirement of troubleshooting through timely diagnosis of problems. In the switchgear segment, distribution utilities are switching to gas-insulated switchgears (GIS), hybrid switchgears and intelligent switchgears. The deployment of GIS substations has seen growing traction, primarily owing to their compact size. The other key features of GIS include high modularisation, high safety index, lower maintenance requirements, and the ability to resist vibration and avoid electromagnetic pollution. Further, as a GIS is housed in a metal enclosure, it offers protection against environmental conditions such as salt deposits in coastal areas, sandstorms and humidity, and thereby, lowers O&M costs.
The use of hybrid switchgears is also fast gaining popularity, as they take advantage of both air-insulated switchgears (AIS) and GIS technologies, striking a balance between the cost of land and the facility construction cost. Hybrid switchgears are compact, with the AIS functionality integrated in a gas-insulated enclosure. With a hybrid switchgear, the bay length is reduced as the circuit breaker and the disconnector earth switch functions are integrated into one module. As a result, there is an overall reduction in the area required for the substation.
EVs are at a nascent stage of development. However, in the long term, it is inevitable that discoms will enter the charging infrastructure segment, with each discom building and managing a chain of charging stations in its supply area. It would be a win-win for both discoms and EV owners, who would benefit from lower prices owing to direct supply from discoms, instead of charging through third parties who purchase electricity from discoms and hence, are obliged to charge higher prices. Tata Power has already spearheaded the installation of 300 charging stations across 40 cities, catering to different EV makes, models and categories. The installation of charging stations across several areas would also catalyse EV adoption and thereby create, a virtuous cycle of growing EVs and increasing charging stations feeding on each other.
Battery storage is a transformative technology, with the potential to alter the business dynamics of the industry, given the fact that it could stabilise grid volatilities and mitigate peak load issues by immediately coming online to supply electricity in times of contingencies. A battery energy storage system (BESS) can charge during the off-peak hours and discharge power during peak conditions. A critical feature of BESS is to support distribution transformers in managing peak load, regulating voltage, improving the power factor, regulating frequency and settling deviations. For example, if there is sudden rainfall, affecting power supply from solar panels, batteries could come online and supply electricity with limited ramping time, thus facilitating continuous and reliable power supply. Tata Power-DDL has installed a 150 kW/528 kWh community energy storage system in collaboration with Nexcharge at the Ranibagh substation. Calcutta Electricity Supply Corporation added a 315 kWh BESS in its East Calcutta substation in January this year.
The way forward
In the coming years, technological advancements in the distribution segment will be capable of restoring profits to the segment by reducing AT&C losses, in addition to reducing expenditure on repairs and maintenance by virtue of real-time diagnosis, identification and pre-emptive repair of equipment throughout the distribution network. Furthermore, the rapidly growing segments of microgrids and EVs offer distribution companies an opportunity to reinvent their businesses and enhance their revenue portfolio. Therefore, the government, equipment suppliers, discoms and financial institutions must, in coordination, design a coherent and functional strategy, taking a multidimensional view of these developments, in order to enable phased execution of these technologies.