Search results for query: *

Hello, For a CT installed indoors in a powerhouse, what is the "typical" or rule-of-thumb life cycle of a CT? What are factors affecting the life expectancy and is it common to see a CT fail in service? Typically, CT's are not maintained, so I was wondering what could be leading up to a...

Hi Gents, I had a question - is the thermal factor rating on a current transformer refer to continuous or overload capability of an instrument to carry increase in current? For example, if 1000:5 CT has TF of 2.0 at 40 degree C ambient, does this mean that this device can carry 2000Amps...

Hello Gents, I'm looking at a trend in PI for a water level value and the value is fluctuating below 0 feet and above 0 feet. To me that is strange, I'd expect the trend to be above 0 feet. What can I infer from this trend? When the sensor is reading & reporting a negative value, is that...

Hello Gents, I notice that in Full Static Excitation schemes, a delta-delta connected PPT is utilized. Why delta-delta type? My thoughts are that to provide higher reliability - if one phase fails, you can still supply AC power to your power bridge converter via open delta connected PPT. Also, a...

Greetings, Has anyone done offline Potential Transformer burden testing? Is offline PT burden testing more challenging to do than an online testing? Just wanted to hear from your experience. Thanks, EE

Hello, Are there any concerns with locating HPU system and battery bank in the same pre-fab building from safety perspective? Any industry codes one would have to follow? Thanks, EE

Greetings All, I have a question - I see a battery cell nameplate having a rating of 105AH 8 HR to 1.75VPC. Does this mean that the ampere hour capacity of the battery cell is 105AH? Why is "8 HR" included in the nameplate data..is this indicating that the battery can produce 13.125Amp...

Greetings, Why do we typically see an open-delta PT having one of the secondary phases grounded? What is the purpose of grounding, to prevent phases from floating? We'd still get the same line-line voltage between VAB, VBC, and VCA. Thanks, EE

Hi Guys, I was thinking about Fe and Cu losses of a power transformer. Do we expect the iron and copper losses to stay constant over the life of a transformer? I know that the total losses are a function of loading of the transformer, specifically the CU losses that are proportional to I2R...

Hey All, Is there a reduction of maximum torque that should be applied to bolts due to the age of the bolts? If bolts have been in service for a long time, is there a possibility of damage to them if they were re-torqued to their maximum spec value? Thanks, EE

Greetings, Are pressure transducers such as GE or Campbell Scientific, need to be installed in upright position? Thanks, EE

Hello, I have been pondering about this topic lately, and figured I'd ask on the forum. Most of us here are professionals and often we go extra mile to meet the deadline or assure a quality product. Please put your discipline, type of business and average hours worked a week. Electrical...

Hi everyone, What's the difference between UL listed/rated equipment and non-UL listed devices? Can a device that does not have UL label be as reliable and long lasting quality-wise? What would be a scenario where you would omit/forego UL label as your tech requirement? Thank you, EE

Hello, Has anyone used a CT Analyzer to determine the accuracy class of a current transformer. If metering class and burden data rating were missing, and you knew the ratio of the CT, presumably you could inject current on the primary and measure the secondary to derive current ratio error in %...

Hello, I apologize if this question was already asked on this forum, but is it a common(industry) practice to provide ground connection for Y-Y grounded PT's at the switchgear where the PT's are installed? If the secondary wiring(4-wire "Y") leaves the switchgear to control room, we should avoid...

Greetings, all Does anyone have technical references/guidance on how to inspect insulators(bushings) for damage or end of useful life, such as signs of pitting/arcing damage, etc. We'd need to evaluate pictures from the site to determine if replacements need to be ordered. Thanks, EE

Gentlemen, Thank you for your replies. I wanted to provide additional information on this setup. The generator feeder will terminate at a power terminal blocks panel and the two circuits will then branch out from this termination point(one can be considered a feeder and the other a tap). I...

This is a supervised industrial installation. I don't see how you could protect the feeders at their origin point other than by the GEN breaker in this configuration. Besides, both runs are short from the genset to their respective switches. Regards, EE

Waross, Thanks for the response. Is the distance of the circuit for each run determine if dedicated over-current protection should be provided. If the circuits from the genset to the switches have a short run, why would GEN breaker not be considered adequate protection for the feeders? I get...

Greetings, All- I wanted to get feedback if it is kosher to have two circuits supplied from the same standby generator. I believe it is permitted to have a single breaker supply two different circuits. The tap rule would not apply here, since both circuit conductors ampacity would be sized to be...