deisel generator set trouble 2

[buguias]

Kindly help me to solve the trouble which I have encountered in the Deisel Generator sets which I am currently maintening .When I changed over the two generator sets to carry the site loads, the incoming generator set experienced a fault indication of underfrequency/undervoltage in the generator switchgear after running a few minutes. Furthermore, the prevoius onlined generator set's circuit breaker is already switch-off and the prime mover is running to cooldown status when this incident happened. Prior to this incident,I have checked the shorting switch for the unit/parallel operation of the Voltage regulator for each generator operating in parallel and I found it to be okey.I am still on the way to find a solution for this problem.

Your kind answer regarding this inquiry is highly appreciated!

Rokie maintenance & service engineer

 

[davidbeach]

The machine couldn't carry the load. Underfrequency is a governor problem and undervoltage is an exciter problem. So, the first thing is to determine which kind of trip.

By the way, it is Diesel, not that other spelling.

 

[nawao]

Few questions:
1)Are this generators operating only when the mains go off?
2)Are you paralleling them to the mains?
3)Or is it a complete islanded system (no mains at all)

 

[Skogsgurra]

Bill? Where are you?

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[rbulsara]

Need more details as to the system design and normal expected operation, etc.

Is this the load tranfer between two generators or from utility to a two generator parallel system?

Also a sequence of events as to which breaker opened and closed would be helpful.

Obviously the second generator alone could not carry the load and got overloaded.

Was this a soft (closed transition) transfer? Was the switchover automatic (even if manually initiated)? Did the two gens ever synchronized and both gen breakers closed to the bus? What were the loads? Gen ratings?





Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

Hi Gunnar.
I'm on a fire rebuild. A bus ride on each end of a 12 Hr shift. On the bus before 07:00 AM and back at accommodations at about 20:40 Cold dirty miserable and not very challenging, but the pay is awesome. Not much time for any life, Eng-Tips included.
The gen set.
If an overload slows a set down, the Under Frequency Roll Off (UFRO) feature of the Automatic Voltage Regulator (AVR) will drop the voltage in proportion to the frequency, starting at 3 Hz below normal.
If the sets were paralleled and you then shut down one set without opening the breaker, the extra load of motoring the set may cause the running set to slow down resulting in both under frequency and under voltage alarms.
Too much load for the set will also cause under frequency and under voltage alarms.
And if the set has been recently worked on and the fuel stop adjustment of the governor is set wrong, the set will act as if it has a much smaller motor. Under frequency and under voltage alarms may be the result.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Correction:
I meant to say:
"And if the set has been recently worked on and the fuel stop adjustment of the governor is set wrong, the set may act as if it has a much smaller motor. Under frequency and under voltage alarms may be the result."
It's 22:27 and the alarm goes off at 05:27.
Night all.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

A.M.
Could be fuel issues. Did you just change the fuel filters? If the air that is frequently left in the fuel filters does not have time to purge, the set may start and run at no load but not have enough fuel/power to drive the load. By the time the drama is over the fuel system may have purged the air and there will be nothing to find wrong.
Extremely cold weather and summer diesel fuel may cause issues until the recirc has warmed up the fuel in the day tank, but this is rare unless the weather is very cold.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[buguias]

Here is my answer to Sir rbulsara's questions:

The generator sets(4 Pcs.) are rated 13.8Kv, 1MW, 3Phase, 60Hz, power factor:80% and it is wye connected.The normal operation is that one generator set runs and carry the site loads every 10 days (scheduled change over from 1 generator set to the next scheduled one), since there's no utility power supply available in the site location.

The load transfer is between two generators operating in parallel.The two paralled generators carry the site loads equally.

When the incoming generator set have already run for almost 5 minutes and carry the 50% of the site loads. The on-lined generator set's main breaker is open in the switchgear manually allowing the incoming generator set to carry the site loads.

The second generator is not overloaded because the site load is only 700 KW as per Kilowatt meter's reading.

The generator main breakers are manually sequenced. The two generator set are properly sychronized and its individual breakers are closing to the line bus.The site loads is a military communication facilities.

Thank you, sir rbulsara for your kind attention for this problem and may this information will help you give me more advice regarding this matter.

The rockie maintenance and service engineer.

 

[rbulsara]

Thank you for the information.

Nothing stands out. As Bill suggested, fuel system would be the prime suspect.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

Where are you and what is the ambient temperature? Do you have hydraulic governors? When the lube oil is cool, the governor response is slower than normal. If you are tripping the breaker on the outgoing set with 50% load, the governor may not be responding fast enough. I had a governor response issue in the tropics with the ambient in the high 80's Fahrenheit. We needed about 15 minutes before the oil was warm enough to give fast enough governor response for our application.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[powerjunx]

warross had pointed out the issue. problem goes with hydraulic governor against the oil viscosity.

Kindly check the governor integrity, loss connection/out-travel arm linkeage, taking samples of oil by draining it out sometimes minute water contamination would deter the response of this unit.

would you mind to name the brand of your governor/actuator?


"..the more, the merrier" Genghis Khan

 

[rasevskii]

for buguias

It is not good practice to trip the outgoing generator at 50 percent load and expect the incoming unit to pick up the load suddenly.

Usually in all power stations the outgoing unit is run down to nearly zero load and the incoming unit is loaded up smoothly while the operator maintains system voltage and frequency.

The way you are now operating is only asking for trouble.
Especially, as noted by others, on a cold started engine.
5 minutes warm up time on a unit of that size is insufficient. 15 minutes or more would be more suitable.

regards, rasevskii