I am doing a dynamic motor starting study for 5000HP motor using ETAP.
Based on motor data,load data, motor innertia(1130),coupling inertia(25), load inertia(78), the starting time is only 3seconds. Based on my experience, it should be at least 5s. is there something wrong with my inputs? Or...
I am dealing with TOSHIBA international on a project. They have already purchased fuses for their switchgears. The problem is, their fuses can't ideally protect their contactors from short circuit faults. I understand that it is a common practce to allow fuses to blow rather to trip the...
I niticed on IEEE buff book-P298 that overload relays- 49/50 should be set at 100% cable capacity and induction relays should be set at125% cable capacity. Is this the common practice here in North America?
I have a prolem here. The switchgear company has purchased all the fuses for their use based on the co-ordinaation study they did inside their switchgear, but the 57X curve is way above our upstream overcurrent protection curves. Even above the transfirmer curve. This means, this fuse is...
I am doing a MV motor protection setting. But the Asymetrical inrush current is overlapped with SR469 Inst. setting, if if shift Inst a bit above, like 0.06s, which is still below Cirucir breaker openning time.Then they would be co-ordinated.Is it reliable to do so?
Hi, Folks,
Inst. settings are very sensitive. Sometimes I try to avoid it for the main and branches. Per code, CEC or NEC, we are not allowed to disable them. So what I normally do is to set Inst on Main higher than the branch fault currents(Max.available), which is reduced by impedance in...
I am doing a coordination study for a ficility by using ETAP and SKM.
What is confusing me is, the same type of fuse was showing on SKM and ETAP TCC differently. on SKM,there is almost no overlap, because the top left portion of 900E was cut off, which was showing on ETAP. the top left portion...
I am doing a protective coordination for 600V system, which is the secondary side[Y] of 1500KVA Transformer. The sencondary side is 3W+[N+G]. N& G are in one wire. GF current calculated is 7.6KA, 3phase fault current is 10.1KA.
I am wondering if we need any G-F protection on MCC main breakers...
Hi, Folks,
I am doing a harmonic study for a facility using ETAP software.On ETAP transformer editor, there is a harmonic page confusing me, which requires the inputs for 6,12,18 pulse data regarding harmonics. I consulted ETAP. They were saying lighty-loaded transformers generate harmonic...
I am doing a short circuit study for a system. The fault level on 28KV side is, R1= 6.78727 OHM, X1=19.19640 Ohm.
On the SLD, it also shows that, R1(pu)=0.6787pu, X1(pu)=1.7196pu. 100MVA base
The above data doesn't make sense to me. The short circuit current derived from the above data.
I am doing NGR sizing for 220KV system. I am wondering if anybody can direct me to size the size of NGR. Is there a rule of thumb for this calculation?
I am doing a relay setting for a plant. I found that the settings for MCC feeders should be set at short time delay and long delay without any instantanneous settings. Otherwise it would be hard to corrdinate with down stream circuit breakers. Is is a common pratice here in North America?
Hi, Guys
I am doing the coordination study for 600V system. What is bothering me is, it is very hard to coordinate between Transformer damage curve with MCB & inrush current, which is very high. According to codes, primary CB shouldn't set higher than 125% FLA, because we don't want dry type...
I am doing the load calculation for the whole plant. I am wondering how I should consider the transformer load with regard to the load list. Should I consider the actual load consumption or just the full load of transformer?
i am still new in North America. what is common practice here ...
Hi, Guys,
I am doing the load calculation for the whole plant. I am wondering how I should consider the Lighting transformer load with regard to the load list. Should I consider the actual load consumption or just the full load of transformer?
Thank you in advance.
I am going through IEEE buff book(2001 version.On page 431-432. It says" The second harmonic and some relays with higher harmonic(e.g., fifth,seventh, eleventh, thirteenth) are filtered to restrain them. The filtered harmonics are applied to the restrainig winding when the magnitude of the...
I am doing UPS 24VDC voltage calculation. Current drawn is 10A. I was told by my lead that I should use 20A for the voltage drop calculation when I use 1 way circuit length. This doesn't make sense to me. Because I am new to this Country. I want to make sure I did a right calculation.
Hi,Everybody,
I am running ETAP motor starting study. I set the fixed tap at -10% on Primary side,in the mean time, I set up Auto LTC at 100%. In this case, I got the minimum voltage dip compared to other cases. Does the fixed tap setting affect the voltage dip while the Auto LTC is also in...
