Urgent! ! ! Comprehensive protection tripping issue! ! ! !
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The medium-voltage motor trips less than one second after being switched on. It has a capacity of 250 KW and operates at 10 KV; the transformation ratio of the current transformer is 50. The overcurrent protection setting was adjusted using comprehensive protection settings to 0.4, with an extreme inverse time curve applied. Yet, the motor trips within less than one second of switching on. The current value shown at the time of tripping was 60 A, which is approximately 3.5 times the set value. According to the curve, the motor should trip only after seven or eight seconds. What could be the reason for this? Waiting online! ! ! ! ! ! ! ! ! !
Your setting current is incorrect; don’t set it based on usual experience – we have encountered such problems here as well. Try increasing the magnification a bit. I guess there should be no problem then.
1. First, it is necessary to confirm that there are indeed no issues with the motor itself! Just measure the insulation and DC resistance to find out! 2. The switch trips within less than 1 second of being closed – is it the protection relay that causes this trip? Is it possible that there are other issues with the tripping circuit (for example, the instrument interlock tripping contact remains closed)? What action records are there for comprehensive protection? What signal is being sent? Did it trip due to overcurrent protection? It’s either some other protection mechanism that has triggered; it needs to be investigated thoroughly! 3. If it is confirmed that there is no problem with the motor itself and that an overcurrent protection mechanism indeed triggered, then the overcurrent threshold can be increased slightly, and the motor can be started again to see if everything works fine
Overcurrent protection should be activated only after startup is complete; if it’s activated from the beginning, the starting current can exceed 10 times the rated current, which will definitely trigger the inverse-time protection mechanism. The 3.5 times the rated current value you see is merely the current level at the moment of activation.
It’s not clear what model of comprehensive protection the poster is using! It uses inverse-time overcurrent protection, which probably also covers the quick-break protection!
Check what the motor start time setting is
When the motor starts, the current can reach more than 7 times its normal value. The comprehensive protection system has a setting for the start time; during this period only the quick-break protection is active, while overcurrent, stall, and overload conditions cannot be protected during this start time. Please check the comprehensive protection system first – it’s unlikely that there is a problem with the motor.
This post was last edited by lzs771010 on 2010-8-28 at 15:14. Is your startup a overload startup, and does it include a water resistor for starting? Here, the water resistance start, overload, and quick-break settings are all at 9.9. I think your quick-break value is relatively low
That is not the quick-break value; it is the overcurrent setting value
I’m not sure what brand of circuit breaker the original poster is using; it seems to me that the quick-break value is set too low. The poster could try increasing that value a bit.
In fact, the original poster hasn’t provided a lot of information clearly, so it’s difficult for everyone to analyze and determine what exactly caused the circuit breaker to trip! If it is a trip due to comprehensive protection for exports, then there will be information indicating the action taken on the panel of that comprehensive protection system; it shows which type of protection was activated (instant break? Overcurrent? Zero sequence? ), it’s obvious just by looking at the panel, but the original poster never told us!