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Switchgear Question No.5 - Current Chopping phenomenon
What is current chopping phenomenon? In which type of circuit breaker (SF6 or VCB) it is more severe?
Author : Glavizh - From: Iran-Mahabad
 
#1
Tue, March 29th, 2011 - 13:09
current chopping in CB is the incident of arc current interruption before normal current zero is reached.If This current is enough to deliver a voltage which is greater than restriking voltage then the arc will continue again. But gradually the current falls and certainly the voltage also
reduces and finally fall down the restriking voltage and ultimately arc is extinguished. It results in voltage oscillation in the line which affects the electrical equipments.
I think it is severe in Vacuum circuit breakers (VCB) 
Author : Jagadish Subbaramaiah - From: India
 
#2
Tue, March 29th, 2011 - 14:10
In addition to my earlier response information available at the following link is releavnt and useful

http://www.csanyigroup.com/comparison-between-vacuum-and-sf6-circuit-breaker 
Author : Jagadish Subbaramaiah - From: India
 
#3
Fri, September 28th, 2012 - 19:47
How severe the capacitor switching through VCB?,

and what all the points to be consider for cap switching? and what is the instantaneous current during switching and immediate voltage after tripping for 250KVAR on 12KV system voltage? 
Author : GOPAL - From: india
 
#4
Thu, October 4th, 2012 - 11:54
The physical processes during the capacitive switching duty for vacumm circuit breakers have been studied by T. Kamakawaji, T. Shioiri, T. Funahashi, Y. Satoh, E. Kaneko and I. Oshima, “ An Investigation into Major Factors in Shunt Capacitor switching Performances By Vacuum CBs With Copper Chromium Contacts ”, IEEE Power Engeneering 1993 winter meeting Columbus OHIO
They found that the pre-ignition at contact closing and the subsequent inrush current heavily eroded the contacts leading to detached particles. These particles cause late breakdowns which appear as NSDD’s. The NSDD or non-sustained disruptive discharge is a disruptive discharge associated with current interruption that does not result in the resumption of power frequency current or, in the case of capacitive current interruption does not result in current in the main load circuit. Breakdown frequencies of typically 3/1000 where found under the experimental conditions studied. A restrike can generate an overvoltage of 3 pu. between the terminals of the capacitor bank, whereas a NSDD is accompanied by a sudden voltage shift of the neutral capacitor bank voltage, which leaves the voltage across the capacitor unchanged, but creates an overvoltage of between 1.5 and 5 pu. on the terminal of capacitor bank to earth. Due to the rare occurrence and the random nature of the phenomenon, the relation between NSDD and overvoltage is not well understood.
The occurrence of a Non Sustained Disruptive Discharge leads to a shift of the voltage of the neutral point of the bank. Although the phenomenon in itself is rare, the over-voltages produced are deterministic and depend on the recovery voltage of the phase in which the NSDD occurs and on the moment of breakdown. The experimental study shows that the overvoltage after NSDD is limited to about 4.2 pu. on the capacitor bank terminals. Surge arresters are shown to be an effective means to limit this overvoltage. As cost efficient solution it is proposed to use a single surge arrester on the neutral point of the capacitor bank.
 
Author : unknown
 
#5
Sun, December 9th, 2012 - 22:12
there are certain circumtances like disconnecting transformer on no load in which it is necessary to interrupt small inductive current.the no-load current of a transformer is almost at zero power factor lagging.This current is normally smaller than the normal current rating of the breaker.interrupting such current causes severe duty on circuit breaker.this phenomenon is called current chopping. 
Author : sourabh jal - From: india
 
#6
Sat, April 6th, 2013 - 05:37
Current Chopping is when a low inductive current eg. Current to a shunt reactor or magnetising current of a transformer is interupted by a circuit breaker, current flows to zero before the natural current zero. 
Author : Cleophas Abimiku - From: Nigeria
 
#7
Thu, November 21st, 2013 - 11:38
When low inductive currents, such as magneting current of transformer, shunt reactors are interrupted by breaker, there is rapid deionization of contact space and may cause the current to be interrupted before its neutral zero. This phenomena is callad current chopping.In such situation,the energy stored in the magnetic field appears in the form of high voltage across the stray capacitance,which will cause the restriking of the arc. 
Author : Pramod kumar tiwari - From: India
 
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