Hello,
I am inserting fault impedance into 3-phase and line-to-line faults in order to find a limiting condition for overcurrent and undervoltage relay coordination.
This is for industrial 4.16kV and 480V systems, which have a fairly high X/R ratio.
Since the system is mostly reactive...
Hello,
Suppose I have a 3-phase 480V panel which has 277V branch positions. Is it correct that the TCC plot reference voltage should
be 480V? I am trying to plot a branch circuit breaker and am unsure if it should be 277V or 480V. Will a single pole single phase breaker off of such a panel see...
Hello,
Suppose in a plant that the voltage at an MCC is below normal due to a degraded switchyard voltage. Fed from the MCC are various motors which use size 1, 2 and 3 starters. With a degraded MCC voltage, the contactors are expected to draw more current due to a degraded source voltage. For...
Greetings:
If anyone has the book "Industrial Power Systems" by Khan the subject refers to the section (9.7.7) in that book.
There have been many helpful posts on motor acceleration time on eng-tips, but none which I have found which might explain why:
average motor torque, Tm = (3*Tlr +...
Greetings:
Wondering if anyone can share more examples or experiences with coordinating undervoltage and overcurrent relays. The paper
"Allowing for decrement and fault voltage in industrial relaying", Arnold Kelly
Industry and General Applications, IEEE Transactions on
Date of Publication...
Hello,
If I had an undervoltage relay in a 120V relay loop receiving input from 4.16kV bus 4200/120 PT's, would it be appropriate to apply symmetrical components to determine, given the relay pickup (say 55V/120V) and the system sequence impedances, a fault current which would depress the bus...
Greetings:
Wondering if anyone can share their thoughts on (4.16kV/480V) overcurrent and undervoltage relay coordination. A range of fault currents (three-phase,line-to-ground,line-to-line,line-line-ground) and corresponding post-fault bus voltages could be calculated and compared to the UV...
Greetings:
Attached is a picture of the zero sequence network of a solid ground fault with high resistance grounding (from EPRI "Grounding and Lighting Protection")
Practically speaking, if the resistor/xfmr was connected to the neutral through a long cable (say 5kV, 2/0, 200'), would its...
Greetings:
The generator neutral conductor of a HR grounded system is rated 5kV, 1/C, #2/0, 100'. In totaling the system capacitance, how can it reasoned to include the shunt capacitance of the neutral conductor? Under balanced operation, the voltage across the neutral should be zero, which...
Greetings:
Can anyone familiar with the following rule of thumb,
"one hour of operation at sqrt(3) times rated voltage equates to about 700 h of operation at unity (rated) voltage" from "The Reality of High Resistance Grounding", Dunki-Jacobs, IEEE Trans. On Industrial Applications, Vol...
Hello,
Suppose that a 480/120V, 350VA transformer is fused on the secondary, and that there are 10,000A fault current available on the primary. Is it correct that the secondary fuse should be rated to interrupt the available 10,000A? If so, has anyone witnessed such an event in practice? Thanks...
Hello,
After performing a re-analysis on an emergency diesel generator high resistance neutral grounding system (for single phase to ground protection), it was found that the resistive component of current was less than the total system charging current (i.e, the resistor kW < system charging...
Hello,
My problem is to determine the shunt capacitive reactance of a 3/C, 500MCM, non-shielded, 5kV cable...
This question is mostly for those familiar with the ABB/Westinghouse T&D Book, Chapter 4, Electrical characteristics of cables, or those familiar with cable geometry.
The cable...
Hello:
I am working on sizing the neutral grounding resistor for a high resistance ( through a distribution transformer) grounded generator. In the first steps, the total system charging current must be determined. I am first gathering the contributions from large cables (500, 750MCM), and...
Greetings:
What knowledge can you share about how the war (most interestingly World War II) changed the way power systems operate?
Some examples which I have found,
-the increased use of capacitors in industrial plants
-the decrease in 600-V equipment, despite its economy
-tapped...
Greetings:
Would be grateful for your thoughts regarding the origin of any bases used for the inrush capability of primary fuses for potential transformers.
I have a GE JVM-3 PT (2400-kV, 750-VA) with an EJ-1 fuse. Also an ancient ITE PT-6 PT (600-VA, 480-V) with Gould A6Y7E-96 fuses...
Greetings:
I am wondering if someone can please confirm a small calculation to determine the maximum secondary short circuit current (i.e bolted fault) on a CPT. The application is for secondary fuse protection of a CPT.
CPT Data:
150-VA
N_turns = 3.7978
480-V primary
480/3.7978 =...
