Vacuum Circuit Breakers Become Prevalent

This "Cut the Copper" blog examines how the medium-voltage (MV) vacuum circuit breaker came into surface and its benefits over air-magnetic breakers.

05/02/2012


In the 1970s, GE dusted off a fault interruption technology initially developed in its labs 45 years earlier, introduced this new product, then placed it into commercial service—the medium-voltage (MV) vacuum circuit breaker. This breaker came onto the market with significant advantages over the medium voltage air-magnetic breakers it replaced (as well as MV oil circuit breakers prior to that).

The new technology reduced the size, weight, cost, complexity and maintenance requirements of previous technologies, while increasing the durability and longevity of the breaker, and the new breaker quickly gained wide acceptance in all markets. Other manufacturers quickly followed suit with new vacuum breaker designs of their own.

Side and rear views of a 38KV vacuum circuit breaker. Courtesy: Siemens, USAFault interruption was crisp and fast and precise, and after interrupting even a large fault within just microseconds after contact opening and the first current-zero on each pole, the contacts that had just interrupted the fault arc inside the vacuum bottles instantly healed themselves, by condensing and re-depositing the plasma of the arc back onto the contacts as fresh new, smooth metal.

This was fantastic for interrupting a large fault, but turned out to be not so good for switching on and off inductive loads (like MV transformers and motors) – as users soon learned. The main problem was that upon opening a breaker, the current that had been flowing through the inductive load stopped flowing instantly. The interruption of current flow went from SOMETHING to NOTHING in virtually zero time, and the energy trapped inside the inductor instantly displayed itself as a huge transient voltage across its outer winding terminals, and could also stressfully distribute the excessive voltages deep within the interior windings and winding layers of the transformer.

This was a far different current interruption than had been provided by air magnetic breakers, which had drawn the fault arc comparatively slowly through a long and large “arc quencher” path, causing a relatively lengthy interruption and arc cooling process. The abruptness of operation of the new vacuum breakers caught the industry off guard and unprepared for a new phenomenon - frequent catastrophic failures of downstream transformers, in ways that had almost never been experienced before. 



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
Control Engineering Leaders Under 40 identifies and gives recognition to young engineers who...
Learn more about methods used to ensure that the integration between the safety system and the process control...
Adding industrial toughness and reliability to Ethernet eGuide
Technological advances like multiple-in-multiple-out (MIMO) transmitting and receiving
Virtualization advice: 4 ways splitting servers can help manufacturing; Efficient motion controls; Fill the brain drain; Learn from the HART Plant of the Year
Two sides to process safety: Combining human and technical factors in your program; Preparing HMI graphics for migrations; Mechatronics and safety; Engineers' Choice Awards
Detecting security breaches: Forensic invenstigations depend on knowing your networks inside and out; Wireless workers; Opening robotic control; Product exclusive: Robust encoders
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
News and comments from Control Engineering process industries editor, Peter Welander.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
Anthony Baker is a fictitious aggregation of experts from Callisto Integration, providing manufacturing consulting and systems integration.
Integrator Guide

Integrator Guide

Search the online Automation Integrator Guide
 

Create New Listing

Visit the System Integrators page to view past winners of Control Engineering's System Integrator of the Year Award and learn how to enter the competition. You will also find more information on system integrators and Control System Integrators Association.

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.