Bacon4Life, Thanks for the response.
I have been told that NEC 90.5(C) (Explanatory Material) says "Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of...
Hello,
We are installing a customer-owned 25 kV to 4.16 kV substation. This is a skid mounted system, and the only exposed energized parts are the tips of the high side transformer bushings. The substation will be outdoors, and will be protected by a 7 foot high fence with a locked gate.
Table...
From the picture, it is hard to tell if they are explosion proof seals just below the block heater starter box. They look small. If they are explosion proof, then the remainder of the conduit fittings are in a Class I, Division 2 environment. You will need another seal off fitting within 10...
Mbrooke,
I am not sure if the conductor is steel or not. I hope to find out next week.
bacon4life,
Is alumoweld suitable for use as a current carrying conductor? I am not a lineman. Thanks for the education on wire types. PS- Good name - makes me hungry!
waross,
The wire is run high all of...
Mbrooke,
I assume that you mean a (galvanized) steel conductor would not be legal.
Would the conductor have to be adequately insulated (5 kV?) from the structure?
Podobing
Hello,
I work for an electrical contractor, primarily in the mining and gas industries. A customer installs and maintains their own 12,470 volt power distribution system. They use wooden poles with a cross arm that holds the three phases. There is also a single wire at the top of the pole...
Guys,
I like the responses so far.
EdStainless - In a previous life, I have seen large HP VFD's used at both 480 volts and 4160 volts. I worked in the mines, and in the mine itself, 480 volts was used for both soft start and vfd applications for conveyor belt (for example), regardless of HP...
Hello,
We are in the very early stages of doing the electrical engineering on a pump project. The pumps will be used to pump water over a long distance (not much lift) for a gas processing operation. The people that engineered the hydraulics say that they need three 600 horsepower motors to do...
Guys,
Sorry for taking so long to respond, but I have been gathering information. When I changed the power system analyzer to look for voltage imbalance (thank you for that recommendation), the voltage imbalance "spikes" corresponded with the motor vibrations. We re-located the analyzer to...
Charz,
I have seen the PT system that you describe used for ground fault detection in medium voltage (4160 volt) systems that are ungrounded. The neutral of the PT primary bank must be grounded or else you cannot detect a ground fault. As you said, the main reason for grounding the secondary...
Guys,
I have been back to the site, and have some new information, but nothing concrete yet.
The motor, shaft, and bearings are all horizontal. The couplers used are grid-pack couplers. The system RPM is 890, and all bearings are grease lubricated.
The power system analyzer was changed from...
Guys,
Thanks for all of the responses and interest in this problem.
To address some of the questions that were asked:
Itsmoked: The motor starter is about 25 feet from the motor. It is an across the line starter, and it is the only load on the 4 kV bus.
Waross: Other loads operated by...
The monitor triggers at 10 percent (sag or swell) on any one phase. It also monitors frequency, and I believe that the tolerance is plus or minus 0.2 Hertz.
Hello,
Underground coal mines use large electric motors to operate their ventilation fans. The number of fans required depends on the size and depth of the coal mine. One fan, in particular is a 2000 HP, 4kV, 890 rpm motor that is started directly across the line. The motor has two vibration...
Bill,
I never thought of using AC to do the measurement. I was focused on DC, and once I get focused, it's like putting blinders on a horse.
What you suggest makes a lot of sense. I'll have to give that a try.
Thanks,
Dave
