Reverse Power trip 3

Sorry, DR files

First file actually showed reverse power condition. Current phase shift is greater than 90 degrees which would put the power into the reverse power quadrant.

Relay oprerated correctly. Pole slip unlikely, power swing possibly, field forcing possibly non existent, prime power issue possible.

About your graph:
1 -It was not included digital channels 32R-P1 and32R-P2.
2 - Right vertical cursor indicates triggering of the DPR. What event recorder start this one?
3 - Records of 0.4seg is insufficient for analysis. There should be a oscilogram up to 10sec.
4 - The phasor curve do not depicts the capability of the generator; does not indicate reverse power.

Attached is DR files analysed by a program that I am familiar(DPR Reason brand)
I did not calculate the three-hase power either. I'm assuming CT ratio: 1000/5 A and PT ratio: 13800/115V. Is that correct?

Hello:
CT 1000/1A, VT 13.8/sqrt3/ 0.11/sqrt3 kV

Setting Recorder 1sec, 50/50%
Trigger is Power P1 trip.
10sec was start on/off, reset time 3sec is latch function in operation

I stand corrected, looking at your png file on a cycle by cycle basis, current phase shifted the complete range from 0 to 180 degree, pole slip very likely.

oscillograms attached the power phase of the data records.
Cursor left by measuring the direct power and reverse power (-10MW). The oscillations have a period of time <0.3seg prevents the reset cycle when it goes positive. With that P1 was operated after 10sec.

The setting P1 = 3 * 17/100 = 0.5MW and P2 = 8 * 17/100 = 1.36MW are easily achieved, however only P1 gives trip .. Why?

The regularity of the oscillograms Vn and absence of voltage dip, indicating that there was no failure in the AVR or fault.
There was a disturbance starting 10 sec ago (not registered) on which the system tried to take the entire load of the generator.
In my opinion this oscillation does not define an out of step trip.

I think the original png file blow-up was easier to see.

Cycle by cycle analysis shows a propagating current shift from in phase to 180 degrees out of phase and you can only get that from a pole slip.

Easier to view the scenario as a large salient pole unit with an internal impedance of a pure inductor and connected into an infinite bus. Moving the rotor 1 complete pole pitch and you get 180 degrees.

Trace indicates current from pure power to reactive to reverse power to reactive power back to pure power. It would be hard to imagine that it is just rotor swing without going unstable or the oscillations would decay back to normal power generation without tripping.

Studies of stability are associated with delta = power angle.
For simplicity assume deltaR = mechanical angle between the rotor and stator.
In transient stability maximum deltaR is assumed 180degree for avoiding Motoring of synchronous machines.
OST is a loss of estability seen by admitance relays

Motoring the generator that is under the control of the automatic voltage regulator does not threaten the power system. Of course, this assumes the que system can withstand the loss of the failed unit's generating capacity. Because the field circuit is unaffected by the loss of the prime mover, generator Var loading and terminal voltage remains unchanged immediately Following the power reversal.

Engine-driven generators have mechanical protection systems que shut down the drive in the event of mechanical failures such as bearing overheating. On these units, motoring may be the result of a mechanical protective trip. In this situation, motoring can cause severe damage, because the initiating mechanical fault has not been cleared. Also Motoring these units poses a danger of explosion and fire because of unburned fuel. Gas turbines and other gear-driven generator units are subject to damage under motoring conditions When gearing is designed to be unidirectional. In such designs, only one side of the gear tooth is machined to act as a drive surface. Motoring reverses the input to the drive and the wrong tooth acts face the face the drive-Resulting in excess wear and heating.


Motoring is a problem of prime mover. Although not a practical reasoning, I always wonder what would happen if no protection operate: After short time of motoring, diesel prime mover burst and the electrical system would be stable with the generator keeps running as unload induction generator.

Slavag should worry to inspect damage in diesel engine instead of OST, and triggering DPR by pickup relay instead of trip relay.

ERRATA
......................................................................................................
...................................................................................................
....................After short time of motoring, diesel prime mover burst and the electrical system would be stable with the generator keeps running as synchronous condenser.

...........................................

Diesel connected generators are not designed for the function on a sync condense unit.

Trying to drive the prime mover, burst or not will possibly redult in generator damage, likely bearings first the stator overheating, cooked insulation due to lsrge load current from a siezed engine.

Sync condense unit are typically large unloaded synchronous motor or designed such as to operate as a sync condense unit. Other types could be decoupled horizontal machine with starting motor running gear and a decoupling plate, vertical machine duch as pelton ot francis turbine with pressurized scroll case to drive the water below the turbine.

Anyways, that us what we have in our system in with the exception of unloaded sync motors, customers such as paper mills and mining mills have them.

Large diesels have an annoying tendency to pump lube oil when under light load, no load or when motored. Often motoring is the worst case for oil pumping. The lube oil "slobbered" into the exhaust system is liable to ignite or explode. Burning oil may be ejected from the exhaust stack.
The power required to motor a diesel engine is well within the capability of the generator end to drive. There are other possible issues;
If the engine lost power due to fuel shortage, some injectors and some injector pumps may be damaged by running without fuel.
If the engine tried to shut down because of low oil pressure, the engine may be damaged by running with low oil. Low oil pressure may lubricate the bearings but be insufficient to spray oil onto the cylinder walls resulting in piston, piston ring and cylinder liner damage.
A complete loss of lube oil will, of course, also damage the bearings.
Damage to the camshaft, cam followers and tappets may also result.


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

Merci !

summarizing my point of view:
Motoring is a problem of prime mover not eletrical generator!
That's all!

Ok, thanks a lot guys for your opinion.
Engines in tests now, from yesterday in full operation. Will see.
I try now receive new DR, yesterday was again reverse power trip.
My problem, station is very far from me and we have from time to time problem with Ethernet.

In regards to diesel generators as synchronous condensers;
I know of an installation where this is done.
A city was supplied be a diesel generating plant.
A transmission line was built to supply the city from a new hydro installation and the DG plant was mothballed.
The city load grew and the transmission line voltage drop became an issue.
The DG plant was put back in service. The generators are run at low KW output and high KVAR output to offset the transmission line voltage drop.
I don't know if there are oil pumping issues.

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

In any case, I see this as OUT OF STEP and Im worry, becouse Im not have on this moment out of step protection of generators.

Connection was OK today.
See picture, OUT OF STEP

slavag,
-1st thread: I think it was out of step situation ( pole slip, 78 ), Im not believe in some real reverse power: diesel fault.
-4rth thread:I try now receive new DR, yesterday was again reverse power trip.

1- You should fix 32R-P1 and P2 because of maloperation if indeed there is no motoring.
2- about tnudot.JPG:I believe this oscillogram is not enough to make a judgment.
if were a comtrade file maybe I could give an opinion.

Hello odlanor.
Please find attached DR files
Trip was faster, Power 2 was tripped.
In operation was two generators, tripped only one, second was near to trip.