All,
I'm working on a project where the client has already purchased two 33kV/480V Wye-Wye transformers, one at 1.5MVA the other at 1MVA. Both Wye neutrals are solidly grounded.
These transformers come with current limiting, primary fuses mounted within the transformer's cable box enclosure...
All,
Unusual problem that I can't explain, looking for some help:
We have a 480V, 3phase, 2MW resistor load bank for testing generators. If we megger the phases with respect to the frame, with the unit's frame not bonded, we get high MegaOhms on all phases. If we then bond the frame, and...
I am trying to find a unit cost for decommissioning and removing of O/H transmission lines. 2016 PG&E Final Generator Interconnection Unit Cost Guide has the following:
Double Circuit (per mile, $x1000)
69kV = 420
115kV = 420
230kV = 650
Those published values seems high for removal of lines...
We are designing a 480V solidly grounded system for an industrial mine located in the Southern USA, where the climate is mild and the area will be designed with a solid industrial ground grid with multiple ground rods. Customer has requested that all 480V branch circuit feeder (15A CB and...
At a site in Canada, we have a 5kv feeder that has four 3c-#500 MCM, shielded, Aluminum armoured, 5kV, 100% cables running in parallel. The run length is 350m. One of the phases on a cable failed and the client wants to replace it. They already have onsite a 400m reel of 3c-#500MCM, shielded...
Curiosity question: for PT primary fuses, say 4160V, current limiting, ferrule mounting similar to the fuses shown in the following specification sheet: Link
I noticed that when I measure the fuse resistance with an ohm meter I usually get around 30ohms for a good, non-blown fuse. For all other...
Hello,
We are installing a 69kV EPR incoming service cable from O/H lines to feed our plant. At the O/H power pole structure there is a 3 phase disconnect switch gang operated by a lever handle at ground level. The power pole is wood and sits in a steel pile. There are three ground rods, a #4/0...
We have a 3 wire, 600V secondary distribution fed from a 1.5MVA XFMR with a 5A NGR on the Neutral to ground. The system is designed to Alarm on Ground fault only.
Yesterday while clearing snow with the excavator, the crew ran over a 600V, 3c-#4/0 armoured cable feeding the fresh water pump...
Hello,
We have a 1.5MVA XFMR that was used to step up 600V to 4160V for an undergrounded (U/G) tunnel in a remote mining operation. The U/G tunnel has been decommissioned and I would like to reuse this transformer for a 4160/600V step down application. However, I am not familiar with a...
We have a 4160/600V 1.5MVA/2MVA (ANN, AFN) dry type transformer that is used to run load banks for testing the upstream 4kV gensets. Curious to know how frequent (per hour) can this transformer be cycled (re-energized)?
Energisation of any transformer will produce a magnetic phenomena called...
We are installing heat trace on an overland tailing slurry line. The piping is about 2km long and the heat trace is strictly for freeze protection. It is not process related. We are trying to determine the temperature setpoint. Looking over the IEEE Heat trace standard 515, it doesn't explicit...
We shall install an overhead line running about ~7km west as well as ~5 km to the North East. The O/H line shall be 13.8kV, high resistance, 3 wire, 60Hz, and we shall use Partridge 266.8 MCM ACSR.
We shall also use an overhead ground conductor wire and I am wondering if we should go with bare...
We have a water pumphouse that is approximately 1.5km from camp. The load is about 30kVA, 3phase, 3 wire system (60Hz). We are exploring options and are thinking about stepping up from 600V to 4kV, running a #4 AWG conductor for the distance and then stepping down at the pumphouse with a...
I have to install a 1600A feeder from a unit-sub to a 600V distribution switchgear. I can meet the free air ampacity @75C with 3x1c-#500MCM/PH. The problem is this configuration is unsymmetrical.
A-B-C
C-B-A A-B-C
I could run an extra conductor to make it a 4x1c-#500MCM/ph:
A-B-C C-B-A
A-B-C...
I have an application where I'm running 1000ft of parallel single conductors on tray across a site. I could use free air rating, however, there is one instance where I have to bury the cables to traverse a road and the buried segment is no more than 45ft. I will determine the conductor size...
Basic question on Lockout Relay 86 and power distribution transformers used as voltage step down for industrial sites. Typical transformer sizes are from 10MVA to 500kVA with LV secondary (600V or 480V distribution).
Curious to know at what transformer size do you typically not use the relay...
Anyone ever install a Vesda system to monitor the air within sections of a 4kV Switchgear & 600V MCC?
Vesda is an aspirating detector that monitors the air for smoke to provide the earliest warning of a potential fire. We shall install this system in our electrical rooms. However, our client...
Hello,
I am looking for an outdoor rated 2.5MVA stepdown XFMR from 4kV to 600V. This is going at a mine site in the North and the environment is dusty. I am trying to avoid oil type XFMRS if I can. It's a not a big deal, but I am curious, what's the largest dry type I can get that is "sealed"...
Can anyone give an estimate or ballpark amount per mile (or km) for overhead line at 4.16kV and 13.8kV? (Capital + installation.)
I know it is tough, so many variables including location, terrain, but I just want a rough guide. Assume ACSR, pole mounted line just running along side of a road...
Auto-Transformer Magnetizing Current
For 3phase Auto-transformers used in Step-up/down voltage application, is the magnetizing inrush current approximately the same as a two winding 3phase transformer?
I use the following guidelines for inrush current on two winding XFMRs:
2 X Ipri @ 100...
