I am in the US and have an ONAF transformer rated for 20MVA with a 100kV delta primary and 21.6kV Y secondary. The %Z is 6.03% at 100k-21.6k.
The X/R is unavailable.
If I remember correctly, the X/R ratio I can safely use for a transformer this big is 20 when determining my maximum fault...
We have a 100kV/21.6kV substation. On the secondary side we have 4 cap banks, 300kVAR each, setup in a delta. We then go through 13000 ft of 636 to another cap bank (3 banks at 900kVAR each). After another 2500 ft of 636, we go to a 21.6kV/4160V transformer, which has a cap bank of 600kVAR and...
What are the pros and cons of ETAP vs. EasyPower as far as learning curve and functionality?
I am new to either one and have an opportunity to decide which one I want to learn/use. Does one do certain simulations the other don't? Is one easier to learn than the other? What about support and...
I trying to make heads or tails of a simple trip circuit. I have not seen a circuit such as this but they tell me the wiring is correct as shown in the drawing. Sorry for the crudeness of the drawing.
If the contact below the breaker closes, it trips the breaker. I am totally missing something...
I have taken over a project in the US where a 200HP, 460VAC motor burned up. The only protection, which was in place, was the 'Over Temp Protection 2', per the MG standard. This is essentially a thermostat wired into a NC contact. After reading an older version of the MG standard, this...
I have a conveyor belt application using 2 mechanically coupled 500HP motors with 2 VFD's (VFD1 and 2) and one 500HP motor/VFD (lets call it VFD3). They are setup as master/followers. VFD1 is the master. It takes a speed set point and in turn sends the required torque to VFD2 and 3. The conveyor...
I have a new 3MVA, 480VAC Dry Type transformer, VPI. The manufacturer claims they then dip the transformer, along with the copper bus and insulators after the VPI process. Obviously, this coats the insulators with varnish. Has anyone seen this before? As far as I know, this is not anti-tracking...
Maybe I am reading to much into Article 727.5 for ITC. It says 'installation of type ITC cable with other cables shall be subject to the stated provisions of the specific other articles for the other cables. Where the governing articles do not contain stated provisions for installation with type...
So I have been with this company for nearly a year and have some real concerns with how things are done and not done. This company has been around for many years and rarely had an EE on staff. Is one needed here? For sure.
Since starting, I have had to gently argue the need to have a service...
My question is related to service entrances in an industrial environment. I have been handed a half completed job in which we have a campus of 5-6 buildings with various processes happening in each. We have a boiler building that gets power to several motors from an MCC building. Of course the...
I have a 2000A service and am sizing the EGC and neutral wires from the transformer secondary to the service entrance. I have 6 parallel runs of 500MCM. NEC 2011 250.30(A)(3)(b) says the size of the grounded conductor in each raceway shall be based on the total circular mil area of the parallel...
Is a soft start considered power conversion equipment by the NEC? I am referring to NEC2011 430.122(B). This section talks about bypass devices. I think the answer is no but would like confirmation. The section says conductors feeding these devices with a bypass needs to be sized on 125% of the...
Someone shoot me now, my boss wants to know where the requirement is to have cable going to VFD's being VFD cable (XLPE and perhaps shielding of some sort). I told him I know it is a general requirement in Article 110 (110.3). He was looking for a more specific requirement. I told him I don't...
Sorry looked all over and can't find out what OP means next to my name, Original Poster? Thanks and sorry for posting in this thread - where else to post.
I am a EE trying to decipher the code on bonding of metallic raceways in Class II Div 2 areas. We do NOT use the raceway as the equipment grounding conductor. I am also looking at NEC 2011. System is agricultural 480/277V.
502.30 - Grounding and Bonding, Class II Div 1 & 2. (A) says the...
Are there any gotcha's I should be aware of while supplying a large facility with two services (480V/277 2000kVA and 1500kVA)? I am keeping them isolated and will have the appropriate signage, etc as required and appropriate grounding/bonding. I just want to make sure I haven't overlooked...
Ok, I seem to always work in an area I haven't before. I am looking for good grounding/bonding references. I already know about Soares Book on Grounding and IEEE 142 (they are on order). The reason being the new company I started at has an electrician that was told at sometime in the past that a...
Our customer decided at the last minute to put in a transfer switch (manual-really a contactor), non service entrance rated (no overcurrent protection). They want to put it in after the service transformer and metering but before the disconnect. I have researched this and there seems to be some...
I am looking for product advisories on the ECS2100 when Cutler-Hammer had the line. I have searched high and low with no luck. Anyone have any suggestions? In particular, I am looking for one in 2003 that discussed insulation upgrades on the power drawers.
Anyone using the ECS2100 that was...
