electricpete: Dang it, I think I'm wrong. I agree with you, the imbalance would be in the form of partial vector sum from the stator pole in the series connection having a higher magnitude. Which would probably be difficult to read in the canceling neutral. Good catch, thanks.
An investment into air gap monitoring would be beneficial to monitor gap stability. There are solutions by the major manufacturers to insert core RTDs in the ventilation ducts as well. The level of core monitoring is more dependent on your interest in keeping the existing core.
Technically...
...as another note, I can agree with the others, waiting to replace the core once you strip the coils may put you in a compromising position. It would be worth doing a 3 point heat run monitoring all temperatures and infrared to see the core condition. Options such as Elcid could also be...
edison123: It sounds like there are two schools of the term moving the stator. One being recentering the stator frame and core assembly about the rotor, the other being reshaping the stator core via push and pull methods.
In the latter, we had performed this in our utility on asphalt mica...
Tom: Depending on the head room designed in the core, you should be able to rehabilitate the core if the shape is reasonable. Our utility has a history of operating cores well past 70 years with few problems. This is acceptable so long as the due diligence engineering is performed such as the...
Tom: I agree with your theory. In evaluating some machines with bypassed turns, it does affect the orbit of the shaft centerline. Similar to your eccentricity of the stator, the tight air gap section should induce a larger radial synchronizing torque. Also the tight section should result in...
Clyde38 --- Typical weight for a hydro ~20-50MVA is on the order of 165T with poles attached.
Or for a 100MVA unit, rotor spider 165T + rotor rim + rotor poles + fan blades etc.
Typical pole weight of a 50MVA machine is ~ 2000lbs
I stator rubbed a medium sized hydro machine.
Just as you identified, you should be nervous if you are going to reshape the stator. It really depends on how long you want to stretch the life.
In my case the results post move were as follows:
- core vibration (stretching and relaxation of the...
It depends on your application of the lug. During HV testing, a lot of testing is performed with 600V conductors in free air at voltages >22kV using normal 600V connections.
For a permanent installation, you should do the research with vendors.
Hydro or thermal? If you take apart a vertical hydro, it's very apparent within the thrust and guide bearing assembly as to how the unit is isolated while having a single ground reference.
Mostly, units without ground brushes get them added with a static exciter upgrade (hydro) or 64F...
I agree with schweitzereaton. Shunts are the way to go with voltage-iso amps. I've had too many incidents of so called dc-ct's having hysteresis. The shunt size's aren't too bad, I've had a few which are into the 2000A range, not that much bigger than the bus it's bolted on.
I guess it all...
I agree with 'oldfieldguy'. The final 'trip' test is still required to fire the 86's and 94's and breaker trips/flags/annunciation, even in the digital world.
Kudos to 'oldfieldguy'. The electromechanical relays well applied will still protect you. It is far too easy to turn on every...
In general, relay testing involves secondary injections controlled through a 3 phase test set. The idea is to simulate operational modes to basically trace the expected operational curves using automated sweeps of 3 phase voltages and currents. This is assuming that the metering circuits of...
Where is your generator breaker (high side or low side of the step up transformer)? Also, are you sync PT's accounting for the tap position.
As other have indicated, drop your voltage and the VARs will follow. If your unit has picked up VARs after a long period post syncing, your bus...
In reference to the phase outlets, large generators (hydro-gen) usually have the entire stator winding up to and past the parallel circuit leads unshielded in mica wrapped bus (whether by rect bar, round tubing, solid round bus) aka circuit ring bus, with taps to the phase outlet terminal...
Shielded is the preferred method these days. Older installations (1920's) were unshielded, 1940's also had non-shielded cable leads into generators, and the use of 11kV non-shielded instrument transformer connections. With good line to line, line to phase clearances, you could make anything...
Regarding MW swings during closure, I've seen 0.35pu (with fast decaying swing) of generator MVA swing on a 'good syncronization' or within syncrocheck spec, and issued sycnro-close pulse. I've seen 0.5pu of generator MVA on a manual sync as well. It's quite interesting to watch with a strobe...
There's an IEEE standard regarding neutral grounding schemes. I've worked with all of them, solidly grounded, neutral transformer, neutral resistor etc. Each type has it's benefits and set-backs. The standards even have a tutorial section to help you work out the sizing.
From what I've seen...
I agree with Muthu. I got to work in a large global rewind engineering company for a period, and there is ALOT going on with the slots per pole per phase ratio. I found that there is some juggling within the coil group distribution for the vector summation for phase separation, balance, what...
