They are all SF6 nowadays. Here is a link to one company's offerings:
https://www.hitachienergy.com/ca/en/products-and-solutions/generator-circuit-breakers
It used to be the domain of Airbast 50 years ago. There are still some around in service today.
13,800 Pros:
- 50% reduction in line current
- May allow for simpler feeder circuit configuration due to lower currents.
13.800 Cons
- Depending on the operating environment,
- motor insulation systems will be more complex and potentially less reliable especially if the operating environment is...
Check out this link:
http://energy.gov/sites/prod/files/oeprod/DocumentsandMedia/BlackoutFinal-Web.pdf
It's a lengthy read but gives some good insights into the operation of the electrical power transmission grid.
If you are in a cold climate the dead tank breakers (DTB) utilize electric tank heaters to keep the SF6 gas from liquefying whereas the live tank breakers (LTB) utilize a mixed gas to prevent liquefaction. If you require black start capabilities LTB’s may be a better option for you in cold climates.
Be careful with the larger motors feed at 5 kV. In order to realize the full rating of the motor you will likely be forced into using power circuit breakers rather than contactors. A typical 5000 HP motor at 4000 volts will draw somewhere between 585 - 640 Amps at full load. Depending on the...
Those values do seem extremely low. We maintain many types of transmission system breakers and even the 4000 Amp breakers had higher contact resistances than the numbers you recorded.
The closest match we have in our system would be General Electric type KSO breakers. They are 1200 Amp, 138...
API standard 2026 - "Safe Access/Egress Involving Floating Roofs of Storage Tanks in Petroleum Service" outlines, as the title suggests, a number of considerations prior to entering onto various types of tank roofs.
My question concerns tanks with internal floating roofs. We have a number of...
Thanks for the responses:
** What is interrupting rating of CB's today? 70kA? **
There are 32-138kV breakers rated at 80KA interrupting, 4000 Amp continuous.
**What is the current rating required for 138kV breaker / switchgear if it has to handle 550MW - and how about the busbar and bus...
I work for a utility that operates several large 138 kV systems. Several of these system have become too large in opinion. The most concerning is a 345kV/138kV substation sandwiched between a large urban area and a heavily industrialized area. The 138kV section consists of 16 outgoing circuits...
Wolf39:
It is going to be hard to rank interrupting technologies in order of which tend to chop the most current. In some cases it is going to depend on the voltage level and specific breaker. Here are some general thoughts:
1. Air-Blast – For sure the worst. Keep in mind that all the breaker...
*Gianoli - Why is a contactor better than a circuit breaker in this regard?*
I mentioned this in my previous post for a few reasons:
A. The alloys used for vacuum interrupter contacts are always a compromise. They can’t weld together. They should have good electrical conductivity. They should...
relayman1000,
I am going to assume when you use the term air blast circuit breaker you really mean air-magnetic circuit breaker. There are air blast circuit breakers but they were usually applied at the transmission circuit voltage levels. The ones used in medium voltage circuits were usually...
Perhaps I need to clarify my position somewhat. The failure rate on these things is not low it's almost none existent.
Do we have breakers/contactors/reclosers blow up? All the time. Probably a couple a month. Some have rodents enter the enclosure. Some get wet and blow up. Some get dirty then...
Zogzog,
"NETA recommends doing it "IF APPLICABLE ", whatever that means"
You are not looking at the same NETA standard that I am what rev are you looking at?
**I have the 2005 edition of the Maintenance Testing Specifications Guide. I can’t quote the exact section because I don’t have it...
The company I work for has stopped all regular PM testing of vacuum interrupters years ago. We have thousands in service and the simple facts are that the number of failures we saw (basically zero) simply did not support continued testing. We still do some other tests but not vacuum bottle...
edison123,
You are right. My mistake.
In general, 10% increase in voltage also results in a 10% INCREASE in starting current. However, it does result in a 7% DECREASE in full load current and a 3C to 4C drop in temperature rise. This according the table I am looking at (Standard Handbook For...
I wrote this plan up but now I hesitant about posting it because I have some safety concerns. Specifically surrounding the motor contactor or breaker. However, I would like to post it for discussion purposes only. Would it be worth a try? Would it work? Is it safe? 20 years ago we did this kind...
Give us a bit more info. Might have some ideas.
A. Motor type. Induction-squirrel cage, Induction-wound rotor, Synchronous,???
B. Motor voltage. 4160, 6600, 13,200,???
C. Is there any possibility of getting the motor and fan to turn slowly before energizing the motor?
D. Is this an ID and FD...
Momentary Duty:
Is the Maximum RMS asymmetrical current that the circuit breaker will withstand including short-circuits from all sources and motors and the DC component. This rating is independent of the operating voltage. It defines the ability of the circuit breaker to close against and...
“so, now my question is, could the PI be high because the readings were taken shortly after being removed from the oven (after steam cleaning) and should another PI be run now the the windings have been out of the oven for a length of time?”
Yes, your reading could be high because you had just...
