Surge Capacitors & Arrestors for Motor...
Surge Capacitors & Arrestors for Motor...
(OP)
Dear Folks,
Greetings...In one of the projects, surge arrestor and surge capacitors are located in MV motor terminal box. As soft-starter has been provided for this motor, is it recommended to change the location of surge protection devices to switchgear end (before soft-starter)? The power supply to motor is feeding from Vacuum Circuit Breaker. What are the consequences in shifting surge protection devices to switchgear end? Appreciate your discussion and suggestions...Thank you..
Greetings...In one of the projects, surge arrestor and surge capacitors are located in MV motor terminal box. As soft-starter has been provided for this motor, is it recommended to change the location of surge protection devices to switchgear end (before soft-starter)? The power supply to motor is feeding from Vacuum Circuit Breaker. What are the consequences in shifting surge protection devices to switchgear end? Appreciate your discussion and suggestions...Thank you..





RE: Surge Capacitors & Arrestors for Motor...
RE: Surge Capacitors & Arrestors for Motor...
237-224515
There were a lot of different aspects covered there. Buried within was a discussion about whether surge cap provides comparable protection when remote from motor at the switchgear. I think it highlighted one thing: there certainly are varying practices with respect to surge protection of motors in general. In retrospect, I think surge cap will usually do almost as good at the switchgear as at the motor.
In your case, I'm pretty sure that putting surge caps at the motor would not be an option. Putting them just downstream of the vacuum contactor would make sense to me in that situation fwiw.
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RE: Surge Capacitors & Arrestors for Motor...
237-224515
should've been:
thread237-224515: Surge Caps and Lighting Arrestors on 5kV motor
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RE: Surge Capacitors & Arrestors for Motor...
However, I found another datapoint on the general question of preferred location of caps (motor or switchgear).
The authors below advocate that placing caps at the motor is far preferable to the switchgear. One reason is that apparently that caps near the breaker are more likely to interact with the breaker during interruption to cause problems such as reignition and current chopping.
http:
"Simulation of Protective Schemes of High Voltage Utility Motors", by Archana soni , Gayatri Agnihotri, Ganga A., presented at International Conference on Power System Transients – IPST 2003 in New Orleans, USA
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RE: Surge Capacitors & Arrestors for Motor...
So once you accept that, then you have to look at the PURPOSE of the surge caps. Reducing inductive kickback to prevent chopping currents, especially in vacuum contactor starters, is their main function. So it really becomes a moot point as far as SURGE caps is concerned because you no longer have a straight vacuum starter. Even though the RVSS starter may have a vacuum bypass contactor and a line isolation contactor, all of them that I am aware of will still turn the motor off with the SCRs, not the contactors. So there really is no purpose for the surge caps any longer.
When the RVSS mfr says to move the caps to the line side, they are referring to Power Factor Correction capacitors, not surge caps. PFC caps have a different purpose and may be very necessary, warranting their retention in the circuit. I always recommend that PFC caps in an MV soft starter circuit be controlled by another VC so that they are only on-line AFTER the soft starter is done ramping and the Bypass Contactor is closed.
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RE: Surge Capacitors & Arrestors for Motor...
Having a soft-starter in the circuit changes a lot of practices.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Surge Capacitors & Arrestors for Motor...
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RE: Surge Capacitors & Arrestors for Motor...
RE: Surge Capacitors & Arrestors for Motor...
RE: Surge Capacitors & Arrestors for Motor...
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