Does anybody know where I can get some "hard" data on fluidized thermal concrete (aka Fluidized Thermal Backfill -FTB) for installation of underground power cable? I am familiar with the concept but I need to find more detailed information such as performance data, pricing...
what is the rated voltage of the generator? Also, the value you have listed for transient reactance looks wrong (=0.224 maybe?). The values of reactance listed, are those the saturated values?
The calculation of short circuit contribution from a generator is very involved. However, a quick...
load losses come from 3 places:
1. resistive losses in the windings
2. eddy current losses in the windings
3. eddy current losses in the tank
temperature would affect #1 in that the resistance of the windings increases as the temperature increases (copper & aluminum have a positive temperature...
A very good reference if you can get your hands on one is the Okonite publication: Engineering Data for Copper and Aluminum Conductor Electrical Cables. There are lots of informative charts & tables in this book on power cables, including a chart which shows the short circuit withstand...
Try this link, its the TIA suppliers Directory for fiber optics....its dated April 1999 but it should give you good contact info on a wide variety of fiber optics vendors:
http://www.fols.org/pubs/dir.pdf
Thanks.
Question came up because of the apparent disparity in requirements for fire pump protection in the NEC. The NEC requires the protective device to be sized for locked rotor current (LRA), but but the feeder only needs to be sized for 125% of motor FLA. So, if the motor does happen to...
anybody know how to go about calulating the emergency rating of a power cable? In other words, if you have a copper cable with a temperature rating of 75oC (or 90oC or 105oC), what is the ampacity of that cable at the emergency rated temperature of 130oC?
Reliability is an issue, not so much because it is three winding versus two winding, but because you have one transformer versus two. If that single three winding transformer has a failure all your downstream loads are out of commission until you can repair/replace that single transformer...
yes, 3 phases in one duct is ok if you dont exceed the fill limits for the conduit size. check the NEC.
Also there is a recommendation in the NEC for running all 3 phases in a single ferrous duct (rather than a single phase or conductor) in order to negate this inductive heating effect...
Well, there should be no current flowing through the conduit itself, as it is a single conductor insulated and jacketed cable. My pricipal worry is accelerated degredation of the cable insulation over time due to excessive temperature. The voltage level is about 15 kV (60 hz circuit) but the...
To make a long story short, impedance is inversely proportional to frequency. So, as your line frequency increases, the impedance the circuit decreases. Basically what this means is that, if you have equipment designed for 50 hz applications & you run 60 hz power through it, the impedance of...
Can anybody point me in the right direction or give a good reference to solve the following problem/question:
How much heating (i.e. max temp) will occur in a piece of steel conduit (sleeve) due to the magnetic field produced by a large power conductor run inside of it?
Although the NEC...
thank you. This was the type of response i needed. I suppose that my question is not exactly relay-related but more CT-related, esp with regards to CT saturation. The real problem is, do I need to take into account the peak asymmetrical rms value into account when determining CT saturation...
Quick question:
when determining the setpoint for a instantaneous overcurrent relay for a feeder, what value of fault current is appropriate:
Should the setting be determined based on symmetrical rms, asymmetrical, or peak short circuit (three phase bolted) fault value?
Also, this value, is it...
Noise in a power transformer is due primarily due to magnetostriction, the expansion & contraction of core steel under an alternating magnetic flux, which causes vibration in the transformer assembly. This vibration is transmitted to the air via the transformer tank walls, causing that familiar...
Given the following test data:
Transformer base rating (in VA)
Transformer no-load (or iron) losses (in W)
Transformer load (or copper) losses (in W)
Transformer percent impedance (%Z)
How do you determine %X & %R values?
some confusion on my part...is it:
a) load losses/rating x 100 = %R
or...
Response for #1, #2, #4 =
I highly recommend that you look at IEEE Std 399 - Power Systems Analysis; This standard will give you the methodology for performing a load flow/voltage drop study. There is a chapter devoted to load flow studies along with examples. This is an excellent reference to...
I'm suprised no one mentioned it but there in an excellent textbook by Theodore Wildi that is a very solid intro and very easy to get into. It is a Prentice Hall publication entitled "Electrical Machines, Drives, and Power Systems, 3rd ed." It should be available via ecampus.com...
a few things to keep in mind:
Once you arrive at the size required from calculations, select a standard motor size (i.e. if your calculations result in a 433 hp pump, specify a 500 hp motor for your application). Refer to NEMA MG 1 or National Electrical Code (NFPA 70), Article 430.
Design...
look in the NFPA 850, Chapter 3 "General Plant Design". There are guidelines for minimum separation distances between structures for outdoor and indoor oil-filled transformers including firewall requirements. The guidelines are based on transformer oil capacity (volume), type of oil...
