Is 2000/3600 KVA AA/FA rating a typical value for a dry type 15kV/480V transformer? I mostly deal with oil filled transformer that typically have stages of 1.00/1.33/1.66 PU ONAN/ONAF/ONAF, so just wanted to make sure the FA rating of 1.8 PU was not a typo.
For a 2 MVA synchronous hydro generator, what are the impacts of running without excitation for 15 minutes with the wicket gates closed? How much reactive power would you expect to see flowing into the generator. How much real power losses might occur? Would you expect an in service failure...
Do VFDs with active regen capability typically have any sort of anti-islanding protection? IEEE 1547 specifies that Distributed Energy Resources must trip within 2 seconds, but VFD controlled loads like cranes and elevators can regen for tens of seconds under normal conditions. It seems like...
Do residential style water heater elements have significant inrush when first energized?
I have seen warnings about huge inrush currents for incandescent lamps damaging contactors. For switching water heater elements, can they be treated as purely resistive or would I need to account for...
I recently heard about some arcing that puzzled me and I am hoping someone might have some idea of a plausible explanation for the arcing.
Situation:
A crew was replacing substation getaway #1, consisting of 150 ft of underground 15 kV cable between the substation switchgear the overhead...
Do all 208 V and 480 V disconnects typically have load breaking capabilities? If not, at what amperage rating do isolation-only switches become available?
At the moment I am reviewing a drawing that shows a 400 A 208 V switch that will be used for lockout/tagout purposes. If large amperage...
As a four year update to thread815-433536, Amtrak will be resuming service tomorrow on the new Point Defiance Bypass route between Seattle and Portland.
https://media.amtrak.com/2021/11/cascades-service-to-resume-on-the-point-defiance-bypass/...
Is there a way to have Excel bottom align the text in a cell with wrap text turned on? When I change the alignment in a cell with wrap turned, the text location only changes by the height of a single row of text rather than aligning the last row of text to the bottom of the cell.
The...
For industrial ICs, does short term operation above 85C immediately damage the chip? Or do ICs follow the rule of thumb that every 10°C increase in temperature reduces life by half? I have a circuit board that might occasionally be exposed to temperatures above 85C. I am trying to understand...
Is there a good tool to view the RMS magnitude of a channel in a COMTRADE file? In the image below from a DFR (USI M9000 @6000 Hz), the magnitude calculation displayed by SYNCHROWAVE appears to have numeric noise. I suspect the noise may be due to COMTRADE timestamps being limited to whole...
How long should a 750 hp motor run at idle after unloading it to cool down the motor? This motor powers a water pump via a magnetic drive. The pump currently runs at idle for 30 minutes before shutting down. I was told the idle period was to cool down the pump, though I do not specifically...
Why do ANSI type B voltage regulators have a range of +10% to -8.6% per slide 15 of Regulators-D.Wareham.pdf when the nameplate states +10%/-10%? I can see why they would have a range of +11.1% to -9.1% if the series winding is 10%. I cannot figure out where the 8.6% comes from.
Is there any way to estimate the sequence impedances for the Wye-Delta-Wye 12.47 kV/480V transformer in the attached image? I am trying to calculate how high I should set the ground fault relaying at the substation to avoid tripping on a feeder that has several similar Wye-Delta-Wye...
What are typical reactive excitation losses in a 480V/120V single phase 500 VA Control Power Transformer for a motor control center? Would 60 VAr be reasonable?
Can I put a 120V capacitor in the control panel to provide power factor correction? The MCC already has power factor correction...
Is there a term besides sync check for describing network hot line-hot bus reclosing logic?
At generation sites and interfaces between planned islands, the traditional sync check has a large allowable slip frequency, but a very small angle difference.
For all other locations, the goal is to...
Is it typical for higher harmonics to increase well after transformer energization? The attached file show 3rd and 5th harmonics actually peak after about 2 seconds. This is first time our transient recorder has capture this long of file, so I curious as to whether this is typical.
The bank is...
We recently had a 7000 amp line ground fault one feeder that also caused an adjacent feeder to trip on about 1500 amps of 3I0 current (500 amps on each phase). One possible cause would be grounded wye-delta connected transformer bank somewhere on the adjacent feeder. Other than inspecting...
I just upgraded to Excel 2013, and now one of my macros throw throws the following error when I try to save the workbook as a csv file to a network server: "Runtime error '1004' There is no active Protected View window." Anyone run into this before? This the first time in a while I have...
Can a pivot table be configured to have the Grand Total field be a SUM for each row, but a MAX for each column? I can work around it by putting the MAX function outside of the pivot table, but seems like there should be built in way to do it.
Example desired data table:
Jan bob sue pat SUM...
