[Interview] Writing a New History of Circuit Breakers

2019.05.31 16:31

General Manager Kim Byung-hoon
Circuit Breaker Advanced Development Team  of Hyosung Heavy Industries

Substations and power plants also have a fuse box?

Although not noticeable, every household has an earth leakage breaker called a fuse box. When a high voltage or current exceeding the allowed value flows or a short circuit occurs, the breaker blocks all electricity coming into the house. The fuse box is also needed for power generating plants and substations that convert the power produced from power plants to custom voltages and currents for users.

"The role of the circuit breaker, a core module of the gas-insulated switchgear (GIS), is similar to that of the fuse box. In power plants or substations, if there is an error in the power system or electrical equipment needs repair, we have to cut off the line while the power is alive. Because they handle voltages and currents that are incomparably higher than those of residential homes, such breakers also require high performance."

When a live power line is disconnected, a very high-temperature arc (spark) occurs in the breaker poles. It is essential to dissipate this arc efficiently and to discharge the high thermal gas in the poles to maintain insulation even in high transient voltage. In December last year, Circuit Breaker Advanced Development Team of Hyosung Heavy Industries headed by General Manager Kim Byung-hoon, succeeded in developing a circuit breaker using a system completely different from the conventional way for 420kV GIS. Hyosung has so far produced simple puffer-type circuit breakers which extinguish the arc by creating pressure in the puffer through mechanical compression. This is a conventional breaking system that compresses the insulating gas inside the chamber with a large operating force and extinguishes the arc with strong pressure. The composite arc-extinguishing spring-operated mechanism uses the arc generated when blocking power as energy. This has both compression and heat chambers, and because it sends high-temperature thermal energy generated by an arc to the heat chamber to create pressure, the system can be operated with much less energy than the previous mechanism.

Achievement from everyone’s efforts for 6 years and 9 months

"Customers' needs were clear. They wanted products that are compact and has no quality problems. The 420㎸ 63㎄ GIS, which was the main export model in 2012, was large in size with low cost competitiveness. The breaking part used the hydraulic operating mechanism in a simple puffer structure."

Circuit breakers operated by a hydraulic mechanism have the advantage of achieving large operating energy with high pressure, but they must maintain high pressure throughout the service period and could possibly cause mechanical reliability problems due to gas or oil leaks.

In addition, the size of the breaker is so large that building substations or power plants required more space and therefore high construction costs. On the other hand, the complex arc-extinguishing spring-operated mechanism that uses compressed coil springs without using a fluid can fundamentally prevent gas and oil leakage problems. Also, its low operating load significantly reduces mechanical reliability risks.

"We began developing the 420㎸ 63㎄ composite arc-extinguishing spring-operated circuit breaker in 2012, but securing the proprietary technology was not easy. We have consulted experts in Europe and Japan on the breaking system and worked with domestic and foreign research institutes as well as the Korea Electrotechnology Research Institute to secure simulation technology for predicting breaking performance. We also conducted a joint study on detailed technologies with a Korean university."

His team also received a lot of support from related departments. Performance Verification Team established a process to self-assess the performance of various solutions by building an interim synthesis facility, and testing centers at home and abroad evaluated and analyzed performance together. GIS Development Team also helped reduce the GIS layout dramatically by developing a new EDS module.

Gaining global competitiveness and a stepping stone for entering the North American market

"The development of the 420㎸ 63㎄ composite arc-extinguishing spring-operated circuit breaker is significant in two ways. One is, we have built the groundwork for the continuous expansion of orders through customer satisfaction. Customers can save costs when constructing substations of the same specification, and after construction, maintenance also becomes easier. The other is that we have laid the technical foundation for developing models for entering the North American market because the North American market requires the spring-operated mechanism for 245㎸ 80㎄ GIS as well."

General Manager Kim Byung-hoon of Circuit Breaker Advanced Development Team at Hyosung Heavy Industries, who won the Proud Hyosung-er Award for the successful development of the 420㎸ 63㎄ composite arc-extinguishing spring-operated circuit breaker, says that there is still a long way to go. Going forward, Circuit Breaker Advanced Development Team plans to actively support sales activities for the increased orders of 420㎸ products. At the same time, all development team members will participate in the production process until it is stabilized by immediately addressing any problems that may occur during mass production. They also have a remaining task for the advancement into the North American market, which is researching how to apply the composite arc-extinguishing spring-operated mechanism to the 80㎄ high-capacity breaking chamber.

"These days, the demand for environmentally friendly GIS is increasing. For eco-friendly gas, we need a lot of advance research because its properties are different from the conventional SF6 gas. The next project of Circuit Breaker Advanced Development Team is to establish technology to design an eco-friendly breaking chamber using the composite arc-extinguishing spring-operated mechanism. We will strive to introduce competitive products faster than our competitors."

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