Q&A: Gas-Insulated Switchgear Grading Capacitors with Patrick Gaillard
July 10, 2017 | Jessica Baris, Communications Specialist and Copywriter
Maxwell Technologies’ CONDIS® gas-insulated switchgear (GIS) grading capacitors have been designed and delivered to customers worldwide since the 1990s. Patrick Gaillard, product marketing manager for Maxwell’s high-voltage product line, says that the GIS capacitor represents a significant part of Maxwell’s history of serving high-voltage customers, a relentless focus on quality, and the culmination of engineering savvy.
Q: Why is the CONDIS GIS grading capacitor a significant product in Maxwell’s portfolio?
PG: From the outside, it looks like a plain tube, so it doesn’t look like much to the uninformed eye. But the CONDIS GIS grading capacitor is actually a very impressive assembly of physics, electrical, mechanical and thermic technical knowledge. When you think about it, it’s an impressive concentration of different technologies and a lot of precision from Maxwell engineers who contributed their knowledge and decision-making over many years of developing advanced versions of this product.
The GIS capacitor’s capabilities are significant when you consider factors such as volume and challenges with temperature issues. It is the answer to the highest electrical and mechanical requirements for a circuit breaker.
Patrick Gaillard, product marketing manager for Maxwell’s high-voltage product line, works with the team of engineers and operators who design and manufacture CONDIS medium- and high-voltage capacitors, including the GIS grading capacitor (pictured).Q: What does a GIS capacitor accomplish in a circuit breaker?
PG: GIS grading capacitors are installed in SF6 gas-insulated substation circuit breakers to reduce the energy of the arc at the opening of the circuit breaker.
The way I like to describe it is like this: If you have two strong people lifting a bench press weight, you’d want both sides to have equal weight. If one side has more weight than the other, one person will have to lift much more. The GIS capacitor creates balance of power on the circuit breaker chamber so that each chamber, when opened, has the same energy distribution.
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Q: Can you comment on the materials that make up the capacitor?
PG: The internal windings of the capacitors, or the active part, is wound with a state-of-the-art winding machine to ensure the highest quality. The oil is specialized for this capacitor, and the dielectric is specified for the customer’s application. Our team selects the appropriate bellow according to the temperature specification to promote the capacitor functions in the 20 to 30 years of potential lifetime. The gasket material is another component. Our team works diligently to select the highest quality materials so that our capacitors perform reliably under the electrical and mechanical stress of demanding environments.
Q: Where has Maxwell completed GIS capacitor installations?
PG: We have high-voltage installations all over the world. Customers in China and India install our GIS capacitors for 800 kV and 1,100 kV breakers. The capacitors are an optimal solution for areas of high density populations, such as India, Japan, South Korea and the east coast of China, where footprint impact—or the size of the substation—is very important. GIS technology helps reduce the size of the substation.
GIS could be installed inside a cellar or below a commercial building or a hospital. In Japan, we completed an installation underground for a substation in a huge parking area. This type of installation would be impossible with air-insulated switchgear (AIS) systems.
The dielectric, or active part, inside a CONDIS capacitor Q: What environmental conditions can the GIS capacitor withstand?
PG: It’s a versatile product. The standard operating temperature is –40°C to 70°C. An even more rugged version of our traditional GIS capacitor can operate from –60°C to 87°C. It was designed to meet customer needs for a capacitor that could endure arctic conditions, such as in northern Russia or Canada.
Q: What are the benefits of the product for the customer?
PG: To achieve the capacitance value the customer needs, GIS is the most efficient volumic solution on very high-voltage circuit breakers. The capacitor is compliant with IEC 62146-1, the standard that sets performance measures for electrical, mechanical and thermal durability of grading capacitors during breaker opening. The tightness is an absolutely critical quality factor too, because our customers want to avoid oil leakage from the capacitor and SF6 gas penetration. The capacitor is also relatively straightforward to install, with two connections, one on each side.
Q: You mentioned IEC standard compliance. What is the process for testing the GIS grading capacitor?
PG: Our high-voltage laboratory is located at our Swiss premises and is where our skilled operators test all our medium- and high-voltage capacitors. The GIS capacitor is placed inside an SF6 field tank so that we can measure the capacitance, tangent delta and partial discharge and perform the power frequency withstand test according to the IEC standard. Our GIS capacitors are installed in breakers with five to seven bars SF6 pressure. We test product tightness with 8 bars of absolute pressure to ensure perfect tightness.
A lab operator prepares to test a set of GIS grading capacitors in an SF6 field tank.Q: Why is Maxwell’s long history of service to the high-voltage industry an important factor when selecting a supplier partner?
PG: We understand the industry’s needs and our customers’ needs inside and out. There is a 100-plus-year-old history behind Maxwell’s CONDIS product line and service to the high-voltage and utility industries. When you understand the history of an industry and have responded to changes in technology and demand, you are more capable in meeting current needs and solving today’s challenges.
Q: Any final thoughts you’d like to share?
PG: Our specialization in high-voltage capacitors has led us to develop more compact products that continue to fulfill customer specifications. As for the GIS grading capacitor, our engineers have refined its electrical and mechanical features since its inception. Our talented team makes it a pleasure to come to work every day.
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Communications Specialist and Copywriter
About this author
Jessica A. Baris is communications specialist and copywriter at Maxwell Technologies and enjoys telling a good story. Her background includes writing and editing for the high-tech, construction, and meetings and conventions industries. A San Diego native, Jessica earned a Master of Arts in rhetoric and writing from San Diego State University and a Bachelor of Arts in linguistics from the University of California, San Diego.
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