Power logging at the 480V 3P 4W main panel (panel that feeds an outdoor lighting only load)
Consider a three phase 4 wire 480V circuit with the following average amperage (Fundamental) measurements:
L1: 191.5A, -7.84 deg
L2: 177.9A, -130.92 deg
L3: 178A, -253.02 deg
N: 20.6A, -156.9 deg
The...
Is this a correct statement?
"In general, if the inrush current exceeds the available SCA, the inrush event would take more time and voltage drop would be larger"
Thanks.
Estimating the kW pickup settings for an ABB Type 32R Circuit Shield Reverse Power Relay Catalog 237P. IB 7.8.1.7-1 pg 4 states "for unity power factor conditions, the 3 phase kW to cause relay operation can be estimated kW=(sqrt3)(V)(I)".
If operating at other-than-unity condition, can pickup...
In the early stages of investigating an intermittent GF Trip on a 4160V CB, and was hoping to get some good feedback.
The installation is typical 4160V 3W 3P Metal Clad switchgear lineup, featuring utility main (normal), and a generator main (backup). These 2 mains are interlocked to prevent...
Hoping to get clarification or opinions on this.
Consider shielded medium-voltage cable (Shield Grounded) and associated loadbreak / deadbreaks (that feature a semicon shield - grounded).
Does examination or otherwise being near require PPE?
My answer is no, the code clearly states "Insulated...
Consider outfitting existing 5kV (4160V ac 3P) outdoor metal enclosed switches (Westinghouse WLI or similar) with an ammeter.
Installing CTs with KA style analog meters is an option.
I am curious if:
1. Any CT-powered digital ammeters available? (Or Battery Powered)
2. Any manufacture have a...
Is there a resource, similiar to RS MEANS, for MV equipment/installation cost estimation? More specifically, commerical / industrial / campus type MV distribution (not utility).
Thanks.
Forgive me if these are dumb questions. the 2012 70E requires the Arc Flash Boundary on the label (among other things). This is defined as the distance at which the incident energy equals 5 J/cm^2 (systems >50V). Is there a method to meet this requirement without calculations, understanding...
Two Questions:
1. What is preferred source (AC or DC) for a dielectric withstand voltage test of an air M.V. C.B.
My thought is AC (assuming the service voltage is AC)
2. NETA MTS lists the HiPot as an optional electrical test (for an air MVCB), with the CB closed. Is there a reason the test...
For a medium voltage switchgear lineup, in a typical industrial or commercial setting. I tend to prefer a DC Battery Bank providing control power to the MV Breakers Close & Trip & Charge, and Protective Relaying Power (assuming digital relays).
This for reliability and dependibility, perhaps...
The notes setting the boundaries for table use list a maximum short circuit amps available and a maximum fault clearing time.
Is this "maximum fault clearing time" determined by the "maximum short circuit amps"?
Thanks
Consider a 15kV aged underground (radial) shielded cable system. 13.2kV AC service. Many splices, taps, and terminations. Ground fault exists, location and phase unknown. Insulation resistance tests confirm this. What is the opinion on thumping this circuit WITHOUT clearing the cables (i.e...
Good day,
Is there a standard that indicates recomended utility voltage supply variance, both phase-to-phase and phase average vs. nominal? I understand the +/- 10% is common for "vs. nominal", and I've seen both +/- 3% and +/- 5% for phase-phase differernce. Curious if this was a publication...
Recently, a 1MVA 12470-4160 oil filled pad mount transformer was energized after being out of service for about 1 month (no changes or maintenance, just de-energized). The unit was energized (no load, just secondary cables) and soon started to "pop" or "thump". This sounded odd so the unit was...
Consider a typical 480V 3P distribution system. A loose / high impedence connection is causing momentary voltage sags during the intermittant arcing. (Not a line to ground or phase to phase fault) I know these voltage sags are detectable downstream of the loose connection, however, are they...
Electrical equipment often has a “Short Circuit Amps (SCA)” rating. If the available SCA exceeds the equipment’s rating, but the upstream protective device to this equipment is sized to operate at a value less than the equipment’s SCA rating, is this acceptable?
Thanks
What is the opinion on the long term effects of 5-25kV shielded power cables de-energized for long periods of time ... that is, cables that are "backups" or "WIP". Cables that are in underground ducts, outdoors, and run through a facility. Will keeping such cables energized be beneficial...
Do medium voltage (5-15kV) cables (shielded power cables) "swell" over time when subject to constant moisture, laying in water?
If this "swelling" is evident, is it indicative of the remaining life of the cable?
Thanks
Is it permissable to provide motor overload protection for 2 identical motors from the same OL relay?
In particular, we have an overhead crane with two 2-speed motors operating in unison (each rail). The "low-speed" motor windings (both motors) are supplied from a common reversing starter and...
Looking at Westinghouse A200 Overload Heater Chart, there are five choices.
1. Non Compensated Open Starters
2. Ambient Comp. Open and Encl. Starters
3. Non-Compensating Enclosed Starters
4. Block Type Overload Using 3 Heaters
5. Single Pole Type Overload
Could someone explain these terms...
