hello folks!
I have a good understanding of transformer insulation classes, the base ambient temp, the temperature rise, hot spots,etc.
However what I'm not finding easily is how to select an insulation class for a transformer?
Is it as simple as: outdoor, hot environment, pick the highest...
Sometimes I hate the NEC.
So I know that if I have a ladder or ventilated tray that has a SOLID cover top, I need to de-rate by almost 60% or so.
But the NEC rules don't cover the scenario of a ventilated cable tray used with a VENTILATED tray cover. In this scenario, can I use free-air...
I have a 13.8kV 3 phase generator that I'm connecting to the utility as part of a DER project.
So I've been pouring over the interconnection requirements documents from several local utilities and all of them show a transformer between the generator and the utility.
What if my generation is...
I'm ashamed to admit that I should know the answer to this question, but I'm blanking....
In popular tools like ETAP, when I plot inverse time current curves, why does the curve cut-off in the inverse time (long time) region? [top left side of the curve]
Kind of like this, or this ?
I've gone through IEEE 80, local code requirements and design guidelines, but I'm struggling with the implementation of ground loops around a substation fence that has a host of interferences, different surface materials, etc.
I'm attaching a photo of the fence in question. The fence in...
Hey guys,
Here is the islanded setup:
I have a 3 phase generator (with a NGR in its neutral) connected to a step-up transformer.
I asked for a DELTA-WYE transformer (delta on the generator side).
However the only available transformers are WYE-WYE.
I suspect I can't just leave the XO on the...
44kV system (3 phase, 3 wire).
This is an existing substation plant that is in-service and we can't de-energize due to customer uptime requirements.
While doing some excavation work for ductbanks/concrete pads/etc, the civil contractor has run into the existing ground grid (done years ago by...
Say you are doing a hand-calc for the fault contribution of a generator.
If an alternator is rated for 2000kVA, but the genset max output kW is 1500kW at a worst case PF of 0.8:
Which number do you use for short circuit fault contributions? The 2000kVA or the 1875kVA (1500/0.8)?
I would...
I have a 750kVA Dry Type transformer inside an e-house.
I also have 13.8kV swgr in the same room.
How do I cool this room? (A) ventilation louvers only with blower fans? or (B) enclosed room with HVAC?
Transformer manufacturer requires ventilation openings on the wall near the transformer...
For a pre-fabricated e-house that has switchgear/control panels/etc, one of the items is a large 750kVA dry type transformer located inside the e-house that dissipates 7kW of heat when running at full load.
The transformer manufacturer says to provide 12" of clearance on the back of the...
Hey folks, this is for a small cogen plant:
I have a 13.8kV switchgear with a 1200A, 95kV BIL vacuum breaker that feeds a 750kVA dry-type 13.8kV/600V transformer via a short 20' cable run. Vacuum breaker has surge arrestors on the load side.
The upstream supply is two large 10MVA transformers...
I have a 600:5A CT, Rated C200. Total burden on CT circuit is 1.008Ohms.
C200 means, it holds 10% accuracy upto 20x secondary rated current.
If my fault level at this bus is 20kA, 20kA translates to 166A on the secondary, which is >20x secondary rated current.
Is this a clear-cut case that I...
Hey folks,
I have 3x 13.8kV generators connected in parallel to a 13.8kV bus with a zig-zag transformer.
I'm trying to see what my options are here for the generator neutrals. See attached PDF for a sketch of what I'm trying to get at.
The way I see it I have 3 options: OPTION 1 - transformer...
I'm attaching a sketch to make it 100% clear what I am trying to do. See attached JPG. https://imgur.com/a/1kLdd2p
This is for an 8 month rental project where they are renting generators and are looking to parallel the 3. There is no space for a new switchgear / 'splitter' to tie the 4.16kV...
I know the answer to this is very subjective, depending on locales, local ministry/inspection guidelines, etc, but I wanted the general group's thoughts on this scenario:
If I have an oil-filled transformer with 700 gallons of non-PCB mineral oil, installed outdoors, but its only a temporary...
Do 600V generator suppliers/packagers typically include surge arrestors with HRG grounded units?
I have a system where: generator is 600V, delta, with the neutral point grounded via a 5A NGR.
2 days ago the generator tripped offline: Phase B / C PTs failed and Phase C surge arrestor...
My projects are always on the service/consumer/industrial load end user.
Often I have to run by the utility whether the main transformer I'm procuring is WYE or DELTA, and utilities will give me their preferences / requirements.
Can someone walk me through why a utility would want a WYE on...
I'm doing a crash course into understanding generator impedances/reactances that the utility for our project is requesting to do their study.
The generator manufacturer has given us all the reactances/impedances/time constants.
My question:
- If its a salient pole generator, is it...
I have a reputable switchgear manufacturer that has provided 4.16kV switchgear lineups (multiple instances, different projects) where the current transformers supplied are rated for 600V.
For example the CT103 from Arman here:
http://www.chesselectric.ca/wp-content/uploads/2015/07/CT103.pdf...
I often run into power system studies where I have the following setup:
generator that is rated at a certain kVA (lets say 1375kVA) some refer to it as "type load".
genset output, usually a lower kVA obviously (lets say 846kVA).
the generator manufacturers provide reactances in the format of...
