Use of Reclosers for Capacitor Bank Switching
Use of Reclosers for Capacitor Bank Switching
(OP)
Hello!
Does anyone have any experience on the use or application of Three-Phase Vacuum Reclosers for capacitor bank switching? What are the key points that need to be address to be able to do this. I read an article about CEMIG (Brazil) being able to use such 3P vacuum reclosers for their 15kV capacitor applications.
CK
Does anyone have any experience on the use or application of Three-Phase Vacuum Reclosers for capacitor bank switching? What are the key points that need to be address to be able to do this. I read an article about CEMIG (Brazil) being able to use such 3P vacuum reclosers for their 15kV capacitor applications.
CK






RE: Use of Reclosers for Capacitor Bank Switching
As you may be aware, capacitor bank switching can be a source of severe voltage transients. Transient (inrush) currents can be also severe. These transient voltages and currents occur primarily when a capacitor bank is energized. Voltage spikes over 2pu can be often be generated, especially if re-striking occurs in the breaker. Back-to-back switching of capacitor banks is even more potentially severe.
To minimize the voltage transients during switching, pre-insertion resistors and inductors are very commonly used in combination with the capacitor circuit switcher (ie breaker).
The 90 degree phase shift between the voltage and capacitor current also presents a challange. As the breaker contacts are seperating, the contacts will normally interrupt the current at a zero-crossing. For a purley capacitive load, the system voltage is a maximum during the zero-crossing of the current. The presence of maximum voltage during the current zero-crossing makes it much more difficult for the interruption device to successfully break the circuit. Hence re-strikes can be common during cap bank switching.
Cooper Power Systems and Josyn Electric have excellent technical articles in PDF format on their web sites. There are many papers that discuss the issues relating to cwitching devices.
Also, a very good reference text is "Electrical Transients in Power Systems", by Allan Greenwood. Mr. Greenwood was at the forefront of vacuum switching develpoement in the early 1970's, while working for GE. His text book is an outstanding referance book, a true invaluable classic.
Regards,
Chris
RE: Use of Reclosers for Capacitor Bank Switching
Are these large substation capacitor banks or line capacitors?
RE: Use of Reclosers for Capacitor Bank Switching
RE: Use of Reclosers for Capacitor Bank Switching
hope to hear some experiences or studies related to this...
CK
RE: Use of Reclosers for Capacitor Bank Switching
Make sure you look at the source impedance when considering switching a bank this large. We tried switching a 2400 KVAR bank at a rural substation a few summers ago. I received several calls from customers who saw their lights get brighter each morning and dimmer each evening at about the same time. I then calculated that the switching was causing a voltage rise/drop of about 4.5% To stop the phone calls, we broke it into four banks of 600 KVAR each and switch them in sequence at 120 second intervals to allow the regulators time to smooth the transition.
RE: Use of Reclosers for Capacitor Bank Switching
Chris8410 makes a great point - the manufacturer's have guidance on this application. Cooper's text states roughly 2 amps for capacitor or cable-energization switching due to the extremely X/R ratio. I even discussed this with S&C regarding the use of an omni-rupter for manual disconnection of a cap-bank at 12.47kV - limitation was 600kVAr maximum (30 amps) on a 600 amp rated load-break switch.
RE: Use of Reclosers for Capacitor Bank Switching
RE: Use of Reclosers for Capacitor Bank Switching