I am running a motor starting by ETAP voltage control module. I set current limiting at 350%FLA and initial voltage setting was set at 55% to ramp to 90%. I was expecting to cause voltage drop on the bus within 15%. But actual voltage drop on the bus was about 30%. I am wondering if I set the...
For some high efficiency motors, the Inst setting should be above 20FLC in order not to cause nuisance tripping during starting. Asymetrical inrush current is of the concern for some fast reacting breakers.
I am working on 400V system. 4 wire system is required for the incoming section. so the 4 pole circuit breaker is needed for the main incomers.
IEC also recommends that 4 pole circuit breakers shpould be used if SWGR or MCC feeds equipment in a hazardous area. But I am not sure about the...
I am working on International project based on IEC standards. But I don't have data for tripping times of Current limiting circuit breakers and fuses.
Some people said it is 1/2 cycle. Other people said it is 1/4 cycle.
I would apprecite it if anybody here can provide me more acurate infomation.
I have a Russian Collegue. He told me that Paper insulated cable is still common in Russa.
I got confued by him. To my knowledge, paper insulated cable should be used on higher voltage level. below 10kV, we should use XLPE.
is there anybody from Russa?
I am currently working in a Russsian project. As per Russian Code PUE. Power cables larger than 3x16mm2 should be with at least 1 diameter spacings in a cable structure. Based on this, there would be a huge amount of cable trays.
Some of my collegues are saying that cable tray is same as cable...
Thank you for your response.
As per NEC, fuses connected in parallel should be factory assembled and listed as a unit. That means, this kind of products are called 2 barrel or 3 barrels per phase and should be listed in their catlogue?
Is my understanding correct?
Thanks.
I did some study regarding the possibility of using fuse -contactor scheme for 10kV motor. I have noticed that there are no large rating fuses which can suit large motor application. The max. 12kV fuse for motor protection is rated 200A. Apparently it is not good for some larger motors as shown...
We are working on a russian project. I am trying to find the grouping factor for 1 core cables and 3 core cables.
My understanding is that the grouping factor for 1 core cable and 3 core cables are different because of diffenrent structures of cables.
We have the goruping factors from a...
Rcwilson, in our case, we will have enough short circuit to clear the fuse within 100ms before the contactor drop out. So contactor can be protected.
Cable sizes for the circuit breaker could be a problem. I will do a quick calculation to size the cable based on short circuit thermal...
I am working on an international project. One of our engineers insists on using 12kV contactor instead of breaker. There are a couple of manufacturers available for 12kV contactor, such as ABB, Siemens, and Areva. I am not feeling comfortable with using 12kV contactors. My concern is as...
Skogsgurra,
Very good point. The setup of the voltage levels can definitely change the efficiency of the motors or other types of machines, which would cause different current outputs.I always go higher settings in order to avoid nuisance trippings. We need to consult with manufactures...
Redox,
Sorry for the late response. I was swamped at work during the weekdays.
I did calc. by ETAP and by hands and got the same results, which are 44kA(3phase, L-G). I was assuming that you input a lower zero sequence impedance for the transformer. Check your inputs and do it again. the...
Hi, Fellows,
I am working on a project on which I have to calculate actual cable ampacity in order to decide overlaod setting of the cable.
But I am not sure about the normal temperature rise inside MV SWGR. Does it affect cable ampacity if the cable is run partly inside SWGR?
Based on CEC, if...
Which Software did you use? I suggest you to check the data input on transformer page if you use ETAP.Usually the hand calculation result should be very close to Software calculation result. I will check with my software tomorrow to see if there is anythng wrong.
Thanks for the hints.
What happened was, the pin resistivity the soil company measured is 71,000 ou-cm, which is 710 ou-m. Engineering company did the designbased on this. Actually, the soil resistivity for the dry gravel is high up to 100000 ou-m.
That's why the grouding resistance is too high.
We did some testing on the ground rod system in one of our stations. The test results are extremely high. It was 1800 ou with one rod. It was 200 ou with 8 rods and bullding steel structure. I think it is due to a poor design.
We are thinking of reducing the soil resistivity by injecting some...
