manual synchronization

[babysitter]

Hi All,

If you miss the opportunity to manually sync when the scope needle is moving clockwise is it okay to immediately slow the prime mover down enough for the scope to rotate counter clockwise and sync in?

 

[ScottyUK]

The frequencies and phase must match closely, and the engine should ideally be slightly faster than the grid. You can slow down to below synchronous speed and have another go as you raise speed. You can sync on a falling governor too but it is more likely that you will end up driving the prime mover in reverse; some are less tolerant of this than others.


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If we learn from our mistakes I'm getting a great education!

 

[waross]

In agreement with Scotty.
You are better to slow the prime mover a little bit and catch it on the next revolution of the 'scope. If you have reverse power protection you may trip it by sync'ing on a falling 'scope.
If you miss your sync, you may be running a little too fast in any event.

Bill
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"Why not the best?"
Jimmy Carter

 

[rbulsara]

Agree with above. Plus there is no 'immediate' effect. So you adjust a little and wait to see that your change is stabilized. Do not close on when the scope is in transient state. Wait for the syncscope either to complete a full circle slowly or stay withing sync limit.

Rafiq Bulsara

http://www.srengineersct.com

 

[jan63]

i do not know about any one else.I agree that it is better to synchronise when synchroniser is moving in clock wise direction.But has any one noticed that sychronising in reverse direction that "incoming" slower than "running" is more smooth

 

[waross]

A good sync in the forward direction should be without disturbance. If you're noticing "more smooth" you may be doing it wrong to start with. Possibly you are closing with the 'scope moving too fast.
I did see a station where closing with the scope turning counter clockwise was sometimes smoother. I've mentioned that plant before. There was a hard wired, 30 degree phase angle wired into the synchroscope.
Does your scope stay at 12:00 oclock after the breaker is closed?

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

 

[slavag]

Hi
What Rafiq saied (and other guys too ).
Best Regards.
Slava

 

[jan63]

yes it stays at 12 o clock.

 

[ScottyUK]

One possible explanation for the rough sync is the response of the governor as the machine takes up load. What type of prime mover have you observed this with?


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If we learn from our mistakes I'm getting a great education!

 

[waross]

Your connections are OK if the 'scope stays at 12 oclock.
Scotty may be on to something.

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

 

[babysitter]

Thanks all for responding. I wasn't thinking in terms of "smooth" or "rough" (new to me) more acceleration/deceleration of the rotor/steam turbine may cause damage overtime.

Thanks again!

 

[ScottyUK]

If you raise and lower speed gently then it won't cause any problem over the range you will be changing the speed. Most auto-synchronisers can automatically raise and lower both the shaft speed and the excitation over defined range so it's nothing unusual. A decent synchronising relay allied to a good governor will do a better job of synchronising than most humans are capable of, and it is consistently accurate where humans occasionally get things wrong. Synchronising a big machine is one of those things that you absolutely don't want to get wrong.

You will know when you have performed a 'rough' sync - i.e. when the phase angle is too far out, you have a ridiculous voltage mismatch, or the frequencies don't match properly: the ammeter dials will bounce like crazy, the mechanical shock will show on the vibration instruments all the way down the machine train, the excitation may trip. Get it too far wrong and you will probably break something expensive.


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If we learn from our mistakes I'm getting a great education!

 

[racobb]

I usually try to set the gen freq. at about 60.1 to 60.15 Hz (US) so that I get a slow approach to sync, sync check get happy, close initiates and the close is very close to 12 on the scope. Much more than that seems to allow the gen to accelerate past 12 before closing. Works for me at least!

Alan

 

[byrdj]

if you are going CW and miss the close at 12, then to make the scope reverse requires reducing steam to the turbine less than the flow required to maintan speed, and with the inertia of the unit, the flow can actually be taken to zero to get the scope to reverse before it gets back to 12. if you close on a quick reversed going CCW, you will go go reverse power on the generator.

if you miss the close, why not leave steam flow as is and catch it at the next 12.

 

[rmw]

As I have had to do way more times that I'd like to count back when units were synchronized by men with good eyes and quick reflexes.

Scotty, reading an earlier post, sounds like you have 'been there, done that' for you to have been able to describe it in such detail.

rmw

 

[ScottyUK]

Hi rmw,

I did one careless sync on a medium-sized machine and it scared me enough to be very cautious in future. I've investigated a few bad auto-syncs where a faulty sync relay was slow in sending the close signal, and a series of them with a bad governor. The worst one (auto-sync, faulty sync relay) was bad enough to feel the shock on the unit from where I was in the control room. All the lights on site flickered, so we must have bumped the 275kV network quite hard. A colleague was up on the machine at the time and when he came down he was an ashen grey colour, babbling about how the whole machine had jumped from side-to-side along the shaftline. It must have been a scary moment up there.


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If we learn from our mistakes I'm getting a great education!

 

[Rodmcm]

Most modern autosynchs have the a selection to synch on the way up or on the way down. I know that there is often a difference between say hydro and steam/gas driven. I understand that this is to stop reverse power and hence acceleration of a large prime mover. I would have thought that if there is a policy for autosynch on site then there would be the same policy for manual synch

 

[waross]

This thread may be of interest!
Wrong generator synchronization ?
thread238-130828

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

 

[edison123]

Wow, Bill. That thread of mine is almost 5 years old. How did you dig it up ?

BTW, that machine is still working. The flapping noise I mentioned there was due to the rotor leads (going under the main exciter armature) not being properly wedged tight. We rewedged the rotor leads and the noise went away.

[I know that my feedback a bit tardy]

Muthu

http://www.edison.co.in

 

[waross]

Use the Google custom search at the top of the page with a few key words. I remembered a few key elements of Gunnar's adventure.

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