Steam Hunting When it was Synchronised

Sounds like one of your parameters is out of sync, also the generators don't appear to be connected properly...

https://electrical-engineering-portal.com/preparing-to-synchronize-a-generator-to-the-grid

sir,

we are matching voltage and frequency with grid then we are getting sync permission.

until we are not closing generator breakers.

and some times observed TG hunting observed at 11 mw at smooth operation

Do bear in mind that no-one on this forum other than the Original Poster can actually see the equipment and its behaviour.

So, it may prove necessary to consult a local, qualified, Electrical Engineer to investigate and diagnose the problem with a view to receiving recommendations from that particular source for its correction.

In order to synchronize a generator to the grid, four conditions must be met:

1. Phase Sequence
2. Voltage Magnitude
3. Frequency
4. Phase Angle

The problem might be related to two control loops/systems with similar response times. If two such loops on parallel systems are put into automatic, then neither loop will achieve setpoint for long, as a disturbance, which in this case could be initiated by a minor change in load, may destabilise the whole system. This principle might be what the Original Poster is observing, without necessarily realising it.

• On process plant, it is dé rigeur to change the control arrangements so that one loop operates on the sum of the two signals and the other on the difference between them. In such situations the response times will then become separated by a factor of 4, which can be an asset in the pursuit of stability as the loops will be tuned differently, one acting quickly and the other at 1/4 of that speed. It is recognised that this principle might not be immediately applicable to the Original Poster's installation.

_{It is interesting that this post is in the Mechanical Engineering section rather than the Instrumentation one.}

It sounds like the TG's are not sharing the load (real power).

The governors on the turbines have a characteristic called droop, which is the response of speed to power.

If a machine is supplying power by itself, the droop is set to flat (isochronous) so that the output frequency will be stable when the load changes. When you parallel a second machine, its governor should be set in droop mode. While the first generator's (master) governor maintains frequency, the second machine's governor can then be adjusted to share the load.

Check the governors' droop setting.

http://www.woodward.com/WorkArea/DownloadAsset.aspx?id=2147483661

https://en.m.wikipedia.org/wiki/Droop_speed_control

Sounds like you need a turbine and generator controls consultant.

Be very cautious if your turbine speed governor has an isochronous setting, in control, if you have that option. One would want the droop governors of both (all) units set the same, if you want them to equally share the load swings. Finally, do not put the zero droop (isochronous) unit into service until the human operators have the islanding (disconnected from the grid) situation stabilized. Probably with a cement plant carried inside the island, that is impossible.

Also, I found that the original posting was hard to follow, because the numbers didn't seem to match. In an islanding situation, the real power produced and consumed has to match 100%. Watts that do not match, instantaneously, cause the machine to accelerate or slow down as kinetic energy is stored in or removed from the rotor (inertia).

Same thing for the reactive (called imaginary) power. If the VARS produced and consumed don't match, instantaneously, the voltage will rise or fall until the excitation system responds or the generator protection system trips the breaker.