Substations, equipped with essential switchgear, are vital for ensuring the efficient, safe and resilient supply of electricity to infrastructure, industries and homes. Failures in these systems can lead to widespread outages, significant economic losses and potential hazards. Therefore, investing in high-quality substation design and maintenance is crucial for a secure and reliable energy future. In recent years, there has been a notable shift towards introducing innovation in substation equipment. This drive, primarily led by manufacturers and solution providers, responds to both technical advancements and utility requirements. These innovations offer numerous benefits, including reduced maintenance costs, simplified operation and streamlined designs. However, fully realising these advantages may require utilities to reassess their design philosophies and update their standards to effectively integrate innovative products.
The new and emerging switchgear designs are focusing on the digitalisation of operations and reducing the land requirement of substations. These innovations aim to tackle one of the main challenges faced by utilities in network expansion, which is right-of-way (RoW) constraints. To address this issue, utilities are increasingly adopting new technological solutions. Gas-insulated switchgear (GIS) is being increasingly adopted by utilities as it requires significantly less land compared to air-insulated switchgear. Hybrid substations, which combine GIS and AIS, also offer potential solutions for minimising space requirements.
Digital Substations
An emerging technology for substations is digital substations, which offer several advantages over traditional substations, including simplified installation due to significantly reduced wiring requirements. They enable interoperability among devices from different manufacturers, enhancing flexibility and choice. Moreover, they improve overall reliability and measurement accuracy while facilitating easier commissioning and operations. One key benefit is the seamless integration of modern electronic current and voltage transformers. This integration enhances electromagnetic compatibility performance and ensures better isolation of circuits. Notably, NTPC Limited’s Talcher and Lara power plants utilise process bus technology, employing merging units and switchgear control units.
GIS
Traditionally, AIS was the norm in utilities. However, the shift towards compact and more efficient substation and switchgear technologies is being driven by increasing space constraints and land costs in urban areas. GIS substations offer significant space savings of up to 35 per cent compared to AIS substations, with lower maintenance and outage costs. Although GIS incurs higher initial costs due to its intricate design and materials, its long-term benefits, including reduced land usage and operational expenses, outweigh the upfront investment. Moreover, GIS’s environmental advantages, such as resistance to pollution and its compact design, make it particularly suitable for densely populated urban areas where land is scarce.
The encapsulated and insulated nature of GIS systems ensures safety and environmental benefits, aligning with the growing emphasis on sustainability. Despite the initial investment, the economic and environmental merits of GIS make it a compelling choice for modern power transmission and distribution infrastructure.
Hybrid switchgear
Hybrid switchgear, a blend of AIS and high-voltage GIS technologies, is rapidly gaining popularity for its cost-efficient approach. By integrating AIS functionality into a gas-insulated enclosure, hybrid switchgear achieves a compact design, reducing the required substation area. This technology combines the benefits of both AIS and GIS, offering a balance between land costs and construction expenses. With hybrid switchgear, the bay length is minimised as circuit breaker and disconnector earth switch functions are consolidated into a single module. Despite an initial capital cost approximately 20 per cent higher than AIS, hybrid switchgear requires a moderate land size – about 50 per cent of AIS and 50 per cent more than GIS. This technology optimises space and cost while allowing for future extensions of existing substations. The use of sulphur hexafluoride (SF6) gas in hybrid switchgear simplifies and reduces maintenance frequency, enhancing operational reliability, even in challenging environments such as polluted or extreme climates.
Vacuum switchgear
Vacuum switchgear, once primarily used for medium-voltage applications, is now gaining traction in high-voltage scenarios due to its environmental advantages over SF6 switchgear. Its compact size, heightened reliability, reduced maintenance requirements and faster restoration times are driving this shift. Vacuum switchgear extinguishes electric arcs using a vacuum, which is more effective than other methods. As environmental concerns grow, there is a push to reduce the use of SF6 gas, making vacuum switchgear increasingly attractive for higher voltage tasks. Its ability to withstand higher recovery voltage rates and its lower moving mass contribute to the technology’s reliability and longer lifespan, requiring less maintenance over time.
SIS
Solid-insulated switchgear (SIS) encases the main medium voltage circuit within insulating materials like epoxy resin. In essence, SIS functions similarly to AIS, with no visible live parts along the main circuit. However, challenges arise regarding electrical field variation in harsh environments. Shielded SIS (2SIS) represents a more advanced solution, featuring three concentric layers: a live part (comprising the main conductor, insert and vacuum interrupter), an insulating layer ensuring insulation in all conditions and a conductive layer guaranteeing electrical continuity and effective earth connection. 2SIS technology offers several benefits, including infrastructure that does not age, absence of three-phase or two-phase faults and no internal arc effects.
Other new and emerging trends
Another emerging innovation is the 3D modelling of substations. 3D modelling software offers extensive capabilities tailored to meet the demands of various applications, particularly in the domain of electrical substations. One of its notable features is its ability to seamlessly handle large substations, even those comprising different voltage levels, with over 30 bays and thousands of components. This ensures transparent and efficient management of complex infrastructures. Moreover, the software includes a range of calculation tools to enhance design and analysis processes. These tools encompass lightning protection calculation using methods such as the rolling sphere method (in compliance with standards such as IEC 62305-1 and IEEE 998), phase checker functionality, clearance calculation, sag calculation and assessment of short-circuit current effects.
Apart from this, condition monitoring system for substations is gaining traction. This technology is a comprehensive solution for acquiring and analysing data pertaining to various parameters of transformers, aimed at assessing their quality and predicting potential failures. This process involves observing deviations in transformer parameters from their expected values. It is applicable to both new, normally loaded transformers and heavily loaded ones, as well as older transformers. The monitoring system is characterised by its ruggedness, compactness and cost-effectiveness, making it suitable for diverse operational environments. Moreover, the system features advanced communication capabilities, supporting protocols like IEC 61850 and MODBUS for transmitting monitored parameters to the control room. It complies with international standards for electromagnetic interference, electromagnetic compatibility, dielectric insulation, high-voltage impulse withstands, as well as atmospheric, environmental and mechanical standards. Specifically, it is IEC 61850 compliant, enabling seamless communication with the station computer.
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Conclusion
To conclude, the latest switchgear designs address utilities’ needs to minimise RoW requirements and promote sustainable operations, supporting the expansion of transmission and distribution networks. Upgrading outdated infrastructure and digitising substation and switchgear operations are essential steps towards ensuring a reliable power supply while reducing operational and maintenance costs, as well as minimising outages. Moreover, with the increasing integration of renewable energy sources, the demand for modern substations and switchgear is growing rapidly to effectively integrate these resources into the grid.
Based on inputs from a presentation by Aruna Gulati, General Manager, Bharat Heavy Electricals Limited at a recent Power Line conference