Yeah I agree and I can see how the MVAR ratings change with square of voltage based on the math. The actual supply MVAR really depends on what you define the operating voltage at for the exact kVAR you need out of the system. You are also right that people do like to round numbers a bit...
Edit - whoops was trying to respond to your first comment
Depends on the utility. The issue becomes loading on the substation at lower power factors. Correcting to close to unity is generally preferred particularly when the transformer will be fully loaded in contingency conditions. The...
Well more of a question I guess.
The utility they call them 10MVAR and 20MVAR capacitor banks but I think in reality if you were building them in racks since 10 and 20 are not easily divisible numbers considering you have three phases. Something like 10.2MVAR and 20.4MVAR (at nominal voltage...
It might just come down to what they state as an operating voltage. Using identically sized and connected capacitors is preferred in station banks just for simplicity.
well this is more for getting specific MVAR ratings out of the bank, basically fine tuning the bank. Standard capacitor sizes limit the bank combinations. Like if you were going to install a 10MVAR bank it could have 17-200kVAR capacitors per phase but that amounts to 10.2MVAR at nominal...
I'm not following?
If a load has say 1000kVAR of inductive load and 1000kW of resistive load and I provide hypothetically say a 500kVAR capacitor, then I'm improving the power factor either way. The original power factor before correction in that case would have been...
I think this is correct, that specifying the 7,970V units is proper.
So basically the equivalent capacitance of 33kVAR at 7,970V is 1.392uF.
If I take my base voltage of 7,970V and 50 kVAR I get 2.09uF, and similarly if I use a 100kVAR I get 4.18uF.
Series capacitor ratings are like two...
Hi,
Say that my system voltage is 13,800Y/7,970V.
If one was to connect a capacitor that is nameplate rated 100kVAR 7,970V in series with a 50kVAR unit with nameplate rating of 7,970V, would these two series capacitors be able to provide me with roughly 33.3kVAR per the series capacitor rule...
I agree using a 400:5A CT is more appropriate for this application given the full load current will only be 328A as stated you will lose a lot of resolution and prone to more error using a 1200:5A CT especially under lower loads.
That's how I ended up designing it was I put the CT right at the...
I looked at this in more detail and I don't think its possible to accurately detect faults pertaining to the transformer or the portion of the tapped line. The only way I think this is possible is putting the current transformers specifically at the tap point so it only sees the TR-1 current in...
Hello,
I am wondering if it is possible to connect a circuit like the one I have shown in the attached PDF where the 87T differential current circuit will only compare the current flowing through my TR-1 transformer? Is that what an 1:1 Aux CT would do for me? The issue is that I don't want...
Yes you are correct, the added cabling is figured into the equation figuring in about 100 meters or more which would be the closest transformer station and switchgear.
CL reactors are an option though they can be expensive. I had one priced recently 400A and 0.5 ohm with enclosure it was...
DVD I think that is a neat approach because the C channels would help make sure the skates stay on the rails that is one big downside to what I proposed is that you would really have to be careful when moving it to make sure you stay aligned and on the surface of the HSS.
On another note, I did...
I actually followed up with some engineers over there and got some additional information, for record:
They use transformers with impedances of around 33.5% impedance on 50MVA base, maximum short circuit level at the station bus is about 25kA. They do parallel all (3) 35/50MVA units together...
So here is a conceptual drawing of my last comment, with the HSS steel channels being used with the skates to move into place, for reference. Stacked solid plates could also be used to get the 4" elevation rather than the HSS but they would be heavier. Nylon rollers would be needed so it can...
Ok makes sense so it’s not necessarily the “column loading” compressive strength that is the issue it’s more of the deformation/deflection caused by the roller point loads moving on the timbers so adding a steel plate will redistribute the load on the joists so the rollers don’t indent the...
Hello,
So I am not a structural engineer but I know enough to be dangerous I suppose and I had to take some structural engineering courses in my undergrad.
Anyways, say that I have a load that weighs 35,000lbs and it is to be placed onto (4) machinery skates that have rollers. Those machinery...
And in thinking about this a bit more, with this configuration saying 25% impedance on 50MVA base with 11.5kV secondary, you would be able to run two transformers in parallel on a bus indefinitely and not exceed the peak ratings of the ring main switches and also not exceed the 25kA for 1 second...
I actually think they are running their transformers in a split bus configuration at the substation with the bus ties normally open. If you look in this article, I think they only parallel the 11kV breakers in switching operations for the low voltage AC supplies which they call LVAC to prevent...
Well I was looking at a utility that has paralleled 3 50MVA transformers on the 11kV bus so of supplying downstream ring main gear close to the station that is rated 25kA the issue is you need to be at 63kA peak or less for the load break switches. By my calcs with 150M of 240 mm 3C cu cable...
