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...
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...
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...
For a power transformer that is built to IEC standards say 132kV to 11kV and 40 or 50MVA top rating what is the maximum percent impedance? Is it possible to build a transformer that has roughly 30-35% impedance at the top rating? I know in US I’ve heard figures as high as 20% are possible at...
Hello,
I have attached an image of what I believe to be the case for a 3-wire current transformer. My thought is these are wired such that there are two half coils internally wound in series as shown, is this accurate? If they were full coils then the measured current would be double of what...
Hello,
FOR ANSI: It is my understanding that the ultimate interrupting capacity of a medium voltage expulsion power fuse is its asymmetrical RMS 1/2 cycle ampere rating, is this true? Therefore, for any X/R ratio, that fuse must be capable of interrupting the asymmetrical RMS current and the...
Hello,
In looking at the Neher McGrath calculations for ampacities of conductors routed in a conduit in air, I can't seem to find anything related to if you have multiple paralleled conduits with the same types of conductors in air, for example, if you had (3) 3" conduits spaced 2" apart in air...
Hello,
Just was curious if anyone knows approximately what LADWP's RS substation transformer impedances are. I know their breakers at their substations were rated 25,000A for many years and the IEEE standard rates those at a test X/R of 17. Based on that the minimum impedance considering...
Hello,
If you have a transformer that is designed as a 55°C/65°C rise, what should the 12 x FLC at 0.1 seconds and 25 x FLC at 0.01 seconds multipliers be based upon? The 55°C rating, or the 65°C rating?
For example, if you have a 3000kVA transformer with 55°C rise, it is capable of being...
What is the usual operation of a feeder protection system supplying secondary networks, is it more typical that the substation circuit breaker will open before the network protector, or the other way around? Reason being, is if you delay the feeder circuit breaker to open a few cycles after the...
So I ran a quick study in SKM to see what happens if you run a substation with (2) transformers that step 138kV down to 13.2kV. The substation I experimented with had a bus tie breaker between the two transformers. The substation was serving a 2-transformer spot network with each transformer...
Hello,
I am curious to know what the typical load power factors have been estimated for urban loads (commercial buildings and some residential towers). Reason why I ask is I've seen a number of urban substations that do not have power factor correction installed at the substation or inside...
Does ANSI C37.010 emergency ratings definitions also apply to medium voltage (5-35kV) drawout circuit breakers? For example, say you have a substation with 84MVA transformers and you have an emergency 4-hour rating of 100MVA on a bus section. At 24.9kV, you would be over a 2000A breaker...
So I'm think this is somewhat of a complicated question.
In a transmission system you have the generation and the end users (loads). So am I correct in thinking there is sort of a three tier system in handling generation revenue?
Basically what I'm thinking is it works like : Generation...
Does anyone know if the old Magne Blast air magnetic switchgear required a free standing auxiliary section when a bus tie breaker was used? I'm looking at the section views of a typical unit and it looks like there isn't much space to do the bus transition in one unit.
Thanks.
Kind of an open question, but have power factors been on the rise in general in terms of the actual connected loads? I am seeing more and more utilities removing capacitors from their system which leads me to believe it is possible that the substation load power factors have been improving in...
Hello,
Just curious, does anyone apply fusible link style cutouts to their system by using the single-shot ratings? I believe the manufacturer's standard label is for a 5-shot operation at a given fault current (there are a series of tests in the IEEE standard). I know that some manufacturers...
Does anyone know of any manufacturers of solid dielectric type branch splices (wye or tee) for polymeric transmission cables up to 138kV class? I saw that Furukawa Electric of Japan makes solid type branch splices for up to 275kV but was curious if any of the other European cable makers...
Thought this would be a good place to ask. How is the T&D industry preparing for the onset of Electric Vehicles, which as an electrical engineer, I am aware have the capability of disturbing daily load profiles to a certain extent? Sorry to be vague but I thought this would generate some...
Hi,
I have a question regarding ANSI style load tap changers applied on the low voltage winding (26.4kV) windings for distribution transformers. I have seen series type LTC's applied to these units where the winding is split into a main winding and a tap winding. Typically ANSI spec tap...
