This may sound a little stupid but I was just wondering if the kW losses (due to I^R) is also metered by the kWHour meter. I believe that the kWHour meter can see this but unfortunately it cannot distinguish between losses and useful power.
Waross,
There is primary circuit breaker and a secondary circuit breaker. However, the secondary cirucit breaker is in the switchgear interconnected by cables.
My question, dealt more with the fact that if the cables have a 125% factor, does it necessarily mean that the switchgear bus bars...
What I am trying to get is for example:
I have a 13.8-0.48kV, Delta-Wye (solidly grounded) 1.5MVA power transformer feeding a downstream 480V switchgear.
The secondary full load is 1804.22A. Assuming no deration, the calculated required ampacity will be 1.25 x 1804.22 = 2255.30A. In CEC Table...
Hi all,
I am aware that NEC requires 125% over-rating factor maintained on top of cable deration. I have a transformer with a secondary full load current. I'm sizing it to be equal to 125%FLA/de-rating factors...then select the cable size.
However, if these cables are connected to a...
Good news guys. I got hold of the switchgear datasheet and it is indicated that:
Symmterical Current = 40kA
Close and Latch Current = 108kA (64kA) Peak
There goes 40 x 1.6 = 64kA, 40 x 2.7 = 108kA
It seems that the breaker is sized as per IEEE Std C37.010-1999 (on a Symmetrical Current Basis).
Some modern distance relays have 2nd harmonic restraint logically built-in to the relay via digital comparators like the AREVA Micom P442 relays.
Some relays have a 50 element that is used to supervise the distance element such that it is set higher than the maximum line in-rush but below the...
I would like to inquire as to what X/R ratio medium voltage circuit breakers are generally tested to sustain their S.C. ratings.
Appreciate any help. Thank you.
I have a 75HP motor with power factor 0.85,efficiency of 0.95 and load factor of 0.98. The nominal voltage is 600V and the motor utilization voltage is 575V
I have a spread sheet showing a FLA calculation using the motor utilization voltage which would end up to be 69.57A.
Using nominal...
I looked at one SKM training manual and it stated that if the "system impedance" check box is selected, the SKM program will use the system short circuit capacity to calculate the equivalent positive sequence impedance and the swing bus voltage drop is calculated given the total power supplied...
The problem we are facing is that this 3.7% 25kV line drop affects the input primary voltage of our transformer (96.3% 25kV nominal) and consequently drops the secondary voltage (including transformer impedance) of our pump station main transformer which is where we are getting the 4.16kV Pump...
We putting up a new substation for a pump station facility. The new main transformer is a 10/13MVA, 25kV-4.16/2.4kV, Z=5.06% power transformer fed from a 25kV Utility Line.
The Utility provided us these information,
System Information At the Transfromer Primary (our 10/13MVA transformer)...
Does this mean that for a Load Flow study, we should always consider 1.0 P.U. voltage at the in-feed or
unless the transmission line impedances are given and then we have to model them into our SLD model?
I have received a Utility Data for me to model the Utility in the SKM program.
The Data gave me the LLL, LL and LG maximum utility fault contribution. It also specified the "Thevenin Impedance" in X1, R1 and Xo, Ro at 100MVA utility Base. I assume that these impedances are in P.U.
However...
We have a 13.8kV solidly grounded system where the short circuit is relatively high.
One of my colleagues are specifying a NEMA E2 class starter to feed a padmounted distribution transformer. The 51G at the secondary is proposed to be wired to to trip the upstream contactor.
My concern is that...
Hi Slava...I've been informed by Burnt2X that you grilled him once on the same subject :-).
I couldn't make out your suggestion. 100/1A connected to a 0.2A relay input?
For directionality, what angle set-point would be ideal for this situation or what would be a good basis for me to set the angle?
Is a 50:5A ZCT (assuming connected burden are ok) sufficient for the application?
I would like to get educated as to how we arrive with the assumption that the SLG current for my application lower than the system charging current in the event of a SLG.
Many thanks...
Thanks to all your inputs.
Burnt2x, if this is an ungrounded system. Is it possible that the broken delta secondary be able to supply enough current to detect a current magnitude enough to pick up the 67N? I had arguments in the past that there is no enough ground fault current enough to pickup...
