As T&D utilities expand and upgrade their grids, they are continuously looking for technologies and products that can help in reliable and economic delivery of electricity. A key technology in this context is high-voltage disconnectors, which are a critical element of a modern grid. Parameswaran Iyer, Global Product Manager, Power Grids Business, ABB, spoke to Power Line about the important role of disconnectors in grid networks, their advantages, and trends in the deployment of this technology….
What grid challenges does India face today? How can they be addressed?
The Indian grid is undergoing changes in terms of the energy generation mix. While ours is already one of the largest operational synchronous grids in the world, the government aims to add more renewables to it. The target, according to India’s renewable energy ministry, is 500 GW of renewable energy capacity by 2030. But as we adopt more renewable energy, integrate more wind and solar parks, micro- and nano-grids, grid operations become increasingly complex. To enable the monitoring and control of equipment and power flows, centrally or remotely, utilities must move towards digitalization – a trend that has already started. The fundamental requirement here is the reliability of equipment in the transmission network.
Often, a high-voltage disconnector is considered a low technology equipment. But one must realize it is an integral part of the power transmission network. A single loose link can cause the grid to collapse. In 2003, a major collapse within the Swedish power grid due to a disconnector failure left around 1.5 million people in the dark. The disconnector is, therefore, put through the same system conditions as a high-voltage breaker or instrument transformer and must be designed to withstand them.
What are the most important technical features of a disconnector?
A disconnector is used to isolate equipment such as breakers, transformers and transmission lines from the power network to enable the latter’s maintenance or replacement. Continuous exposure to weather conditions requires it to withstand harsh environments and ensure reliable operation over its lifetime of about 25 years. Our disconnectors are designed for very low friction, have sealed bearings and very few discrete parts. They are easy to erect and commission at site.
What specific conditions, faced by Indian grids, make disconnector quality important?
India is a large country. Its geographical spread is so vast that outdoor equipment like disconnectors are exposed to a wide variety of environmental conditions – high ambient temperatures, humidity, dust and ice in some places, coastal and chemical environments, earthquakes and storms. A sturdy product is required that can perform well in all such conditions.
Indian utilities are modernizing and trying to move to unmanned substations that can be monitored remotely. As mentioned earlier, the integration of renewable energy sources into the grid calls for reliable technology solutions. Unreliable disconnectors slow down the pace of modernization and the transition to unmanned substations.
Can you please elaborate on this?
In India, problems with disconnectors are taken for granted. We are aware of utilities maintaining teams of personnel for disconnector maintenance, which is carried out more frequently than normal.These teams clean and grease rotating parts and electrical contacts more than once a year. Unreliable design and components, and improper erection and commissioning processes often lead to disconnectors not operating the way they should. Personnel have to go to the switchyard and operate disconnectors manually.
In some cases, contacts get welded when the disconnector is in a closed condition and you can imagine the effort needed to open such disconnectors. Interestingly, some utilities do not trust the indication of the status the disconnector captures and displays on the SCADA. They reconfirm it by sending personnel to physically verify it. This way, utilities are forced to retain people within the substation.
Reliable disconnectors can help them significantly reduce their running and maintenance costs.
How do ABB disconnectors ensure this?
ABB disconnectors are designed to withstand the special conditions discussed earlier.
They use sealed double-ball bearings for rotating parts, which, along with current transfer assemblies, are encapsulated with a long-life lubricant. All linkages use rod-end bearings to ensure very low friction during movement, which is maintained in all types of environments. The current transfer contacts use a special grade of copper that does not need external springs to ensure contact pressure.
It is a well-proven product in the toughest of environments like the northern parts of Russia, deserts of Egypt, earthquake and storm-prone regions of South America and Southeast Asia, and areas with high salinity and chemical pollution.
These days, people try hard to save on installation and commissioning costs. Disconnectors are often commissioned by people who are not fully trained or qualified. Another reason for the maloperation of disconnectors is wrong installation. ABB handles this by ensuring that critical subassemblies are completed in the factory itself.
In a nutshell, with a reliable product and ease of handling, we address current performance issues, support future modernization initiatives, and help utilities reduce costs.
How do customers in India view ABB disconnectors?
ABB disconnectors are known for their quality world over. But quality comes at a price. We have customers who have switched to ABB disconnectors for critical applications in need of higher quality.
We have recently installed our disconnectors in the sparsely populated regions of Leh, Khalsti, Drass and Kargil for Power Grid Corporation of India Limited. A high-altitude application in extreme weather conditions (temperatures ranging from -20° to +40°, frequent blizzards), it called for a technology that could operate in a snow- and ice-ridden atmosphere. The customer knew ABB could do it, and we did.
We are seeing a growing interest in India for our products. Some utilities deploy ABB disconnectors in parts of their network they consider critical, or when they need minimum downtime. Within a short span of time, they see the difference.
We have other projects where customers in aluminum and steel industries, in search of high reliability, went for ABB disconnectors for their switchyards. Our relationship with such customers has stood the test of time and we continue to supply our products to them.
Apart from standard applications, we have also supported our customers with special installations at heights. We have mounted disconnectors on top of gantries with the operating mechanism at the ground level. We have deployed inverted and vertical mountings where there were space constraints. All these were at a height of up to 20 meters. All this was possible only because our product is reliable. You cannot imagine people going up to such heights for maintaining them.
Any final word on quality consciousness and the progressive mindset of Indian customers?
I strongly believe that customers in India are quality conscious. Tender evaluations that over-emphasize the lowest price compromise quality and long-term performance. The examples we have discussed earlier show the changing mindset.
We have seen an increase in our disconnector sales in India and this is an indication of the quality consciousness of the Indian customers.
Regarding the progressive mindset, I can only share an experience. Three years ago, I had a very pleasant surprise while visiting one of our customers. It was a private utility and it had a switchyard in a busy area in a large city. It was completely unmanned – no one other than the security guard at the entrance of the substation. The substation was being monitored remotely and was using ABB disconnectors.