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waross (Electrical)22 Oct 24 16:33 Is the meter showing the energization current of a transformer? One phase is often subject to DC offset and that may be almost as much as 2 times the other phase peaks. I looked and did not see anywhere the meter may be showing energization current of Xfmr...

bacon4life (Electrical)22 Oct 24 16:12 Do you have reason to think the loads are balanced across phases? Perhaps there is twice as much load connected to B phase? Do you think its possibly due to imbalanced loads? The value is approximately 50 Amp peak in phases A & C but 100 in phase B...

Hello All, I have a question. I have a meter that is showing the peak current in phase B to be double that of peak current phase A & C. Does anyone know what may cause this? In phase B its 190 Amps approximately while in A * C the peak was about 95.

Use stranded or non stranded (soild cables) for power distribution cables? Also, use the same for ground cable?

Anyone know requirements for sizing grounding cable on LV side of a power Xfmr?

I know how many power cables I need based on Xfmr size and LV cable I plan to use. My question is do I need a ground and neutral? My thinking is 216 is line to line voltage but the 125 would be line to neutral so I would need a neutral and a ground. Is this correct?

What does a way mean exactly? Does it mean for each direction power flows? If so, why 3 ways? 6 ways?

What do these terms mean in this type of switch? Load Break? Does that simply mean it can be operated under load? Air Switch? Does that mean that it doesnt have any special insulation such as SF6 etc.? Just operates in atmosphere?

waross (Electrical)22 Jan 24 23:41 Equipment grounding or bonding conductor apart from system grounding conductor. Different rules, different sizing. I think what you are saying to Equipment grounding is same as bonding conductor? and the system grounding conductor is what would be the ground...

dpc (Electrical)23 Jan 24 01:36 In the NEC, a grounded conductor carries load current (neutral) while an equipment grounding conductor normally carries no current. So in this case wouldn't the ground cable carry neutral current back to ground? and also carry current under fault conditions that...

Ground cable size required for MV circuit I am currently designing a power system to use 3 1/C 500 kcmil MV cables. I am doing a calculation to determine the size of conduit required as well as grounding cable size required. I found thread on forum listed here about grounding cable size...

As with many things, the definition of over-current has changed over the years. But, cable ampacity, 125% of rated current. The protection setting, by code, depends on a number of factors: Transformer voltage, Transformer %impedance. Fuses, breakers, dual element fuses, Overload protection on...

waross (Electrical)29 Dec 23 17:14 Conductor size is based on rated full load current. If there is a possibility that an ONAN transformer may be upgraded by the addition of fans, the AHJ may require the ONAFfull load current to be used. It comes down to the conductor size or ampacity must be...

waross (Electrical) Noted Finally sit down and was able to review above equations to fully understand. Your feedback is appreciated. Quetiosn: What locale code are you referring to above? My location we would be required to use NEC Article 450 for determining Xfmr protections and while the...

b_gibb (Electrical)29 Nov 23 15:48 The cable is sized for the protection, not the transformer full load rating. For example, if your fuse is 30A, you need to size the cables for this value. In other words, calculate the protection first, then the cable size. Should'nt the cable be sized larger...

waross (Electrical)28 Nov 23 18:43 I get 1202 Amps for both 277 and 480 Volts. Hint: Use 3 instead of root three for 277 Volt calculations. Or; use root three times 480/277. I see how you did this calculation but not sure why you use root 3 for 277 V calculations. If everything being fed from...

I am going to follow up with some vendors to see what options may be available at MV levels. I think some good points are made and it may very well be that some AHJ's will not give a permit for closed transitioning at MV level or maybe even LV.

Appreciate the feedback Overvoltage and jghrist. I am looking to replace several MV duplex switches. A couple are fed from utility and generator as the 2 sources but the others are fed from two different utility loops within the site. The purpose of the closed transitioning spec. is to not...

Closed transition it is very important to make sure that the sources are in sync as close as possible. Often a closed transition switch will have a limited range within which it will complete the transition and a limited time period to complete the transition before it defaults to an open...

Hello, I have a 13.8 Kv-480/277 V, 1000 KVA Xfmr. Using S = V*I*sqrt(3) I got: I available on primary side = 41.84 Amps I available on secondary side (Using 277 Volts) = 2,084 Amps My questions: 1) Do I simply take 41.84 Amps (I on primary side) and multiply by 1.25% = 52.3 Amps and choose...