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Hello All, The project is to refurbish a large 5500HP,4kV Brushless Sync motor and convert the motor protection controls from the induction discs to our standard relay protection scheme for MV sync motors using the Multilin SR469/SPM relays. The 4kV motor is fed directly from a captive stepdown...

jraef, Thanks for your comments. I appreciate the advice and I will post correctly in the future. Thanks again. eleceric

This is perfect timing for a strange event that just occured to me with regards to AC coil contactors. Has this ever happened to anybody out there. A standard contactor with a 110 Vac coil was chattering and was "humming" terribly. Suspecting the shading coil had failed somehow, we changed the...

Try a vendor rep, a motor repair shop, or call GE directly.

Mjeshtri, You do need to monitor this transformer closely as the DGA clearly indicates that there appears to be a high temp oil pyrolysis condition occuring. There apprears to be significant overheating as well based on the indicated CO2/CO ratio as well. Also, C2H2 is high indicating that...

pete: Thanks for the post. Currently we do not do continuous monitoring, but that is something to look into for the future. On my 5kV motors, I try to do semi-annual checks, winter and summer to get some idea of temperature variations on the equipment.

I use the Iris capacitive couplers as well, on 4kV motors ranging from 5000HP to 10,000HP. The on-line test done by Iris is simple, and the data gathered is quite extensive. I'm not quite sure however the value of this yet, as the data is very subjective, and based on typical trends from the...

SparksZA, I have worked with water cooled motors and MV drives for many years. My latest install was ~7MW, and looking back, we should have designed more than just the bare minimum for the cooling loop for better reliability. A flowmeter and circulation pump redundancy would keep you going. I...

No offence Golruss, but you better have an electrical testing firm familiar with parallel systems check out your problem. Sounds like your sources will be paralleled, thus hot phasing is a must and make sure that your alternate source, i.e. genset perhaps, is in sync too. I have to agree with...

Thanks Ralph, however there is a big difference in Pete's equation and the equation that you indicate. From our incident, we have data that gets us close to what Pete's equation generates. Can you clarify Vza, and Vzb for me, as I believe I'm not applying the impedances correctly. Thanks Thanks.

Thanks Ralph, Good info.You are correct, upon further investigation, the taps on the transformers were changed to compensate for an undervoltage occurance at a large refrigeration unit. The two transformers had approximately 200 V difference, i.e. T1=2500V, T2=2300V, or 9% difference. Using...

No problem with the "reverse feed" but in addition to major items that wbd indicates, you will have a delta-delta system so ground fault protection will not be available. It will be worth your time to recommend a hi-resistance ground detector on your 4kV side to detect ground faults even if you...

mpparent, When you say braced, you are refering to the BIL ratings of the Tx, and the MVA rating of the switchgear. Yes, the gear can handle it. Good info electricpete and stevenal, thanks guys.

I have a power system infrastructure that effectively puts two 3000kVA, 13kV/2.4kV, Z1=5.55% and Z2=6.33%, in parallel via basically a main-tie-main configuration. It's not as "clean" an arrangement, due to several feeder breakers that allow the tie between the two transformers. Old...

I'm trying to look for an alternative to grounding brushes that ride on a shaft of a steam driven compressor to dissapate electrostatic charges that are generating nuissance noise signals and in some cases a transient large enough to fry the analog signal input to the monitoring system. Brush...

Confined space, exposed equipment moving while people are working, dust, reduced visability, etc. That's the perfect environment for a wireless gadget. Make sure that you buy good batteries and since this device will be dragging on the floor while the workers are cleaning this dryer, you might...

Thinker, You do not mention if the 10KV feeder is in any kind of a raceway. If this area is prone to excavation work in the future, and since as you are running signal wires today there are bound to be other trenches run in the future, you should consider additional encasement of the HV feeder...

I have to agree with Alwaysex as well. With electronic devices incorporating metering and protection togehter in a small, relatively inexpensive package, it's probably worth spec'ing the gear with these types of devices up front. If cost is that much of an issue, the standard arrangement of...

Many years ago I began programming on Modicon 584's with the old dos Modsoft programer. I was also responsible for training in-plant techs on how to troubleshoot as well as do "simple" changes to programs. This was quite a shift for techs who were used to dealing with relay logic. The biggest...