What Is Syn-Check ?

Are you referring to the synchronising of a generator to match the frequency and phase of the grid before switching it on-line?

Waterlucky,

Strange name!!!

Anyway, the correct term is "sync-check".

It applies to the procedure of synchronising a generator or two power supplies from differing power systems.

Lets take the generator first:

In order to connect a generator on to a live power system you have to ensure three conditions are met:

1 The voltages are equal or within an acceptable band

2 The frequency of the two power systems are equal or within an acceptable band ( they are usuall slightly different with the generator you are trying to synchronise being slightly higher, the difference is referred to as the "slip")

3 The breaker or switch which is used to finally connect the generator to the power system must be closed when the incoming generator's phase angle is exactly coincident or within an aceptable band of the power system( usually 5-10 degrees) you are connecting to .

So in summary you need : voltage, slip and angle.

For a first time synchronising , you will need to verify these three using independent instruments sucjh as a phasing stick

Once done , you can then rely on the built-in panel instrumentation ( if you have that) to display the parameters.

A device called a "synchroscope" is used to give the slip and angle information.

Voltmeters will give you the incoming and system voltages.

In large power systems, a backup verification of these parameters is done by a sync check relay.This is usually labelled as "25" in the schematic drawings.

The other time you will need to do the above is when you are connecting two power supplies together, like from two different systems .Lets say you have transmission lines coming from another power system and you want to connect two power systems, you will need to go through the same synchronising steps as outlined above .

This time it involves a biger process since the control centers of the two power systems will have to be in contact with each other to match the voltages, frequency and slip.

There is another time you verify parameters in a power system but that is referred to as "phasing out" .

It is done when you are cnnecting power supplies or commissioning new HV sub stations.That is different to synchronising.

I said a handsful.

Hope it helps.

Excellent reply. You definitely covered all the bases.

If you are talking about Synch Check for ALternators to be connected with Grid It is like This--

To do above said The Voltage And Frequency of both the systems have to be matched in three manners

1. Voltage Amplitude

2. Fequency

3. Phase Angle for all phases between two Systems

For this earlier days people used to have 3 lamp or two lamp bright or dark method

Now a days Synch Check relays are used.

Hope this is what u wanted

The Sync Check relay is a permissive device that is in series with the breaker closing coil. See this post which is VERY detailed on paralleling and load sharing. Once all the parameters are met for paralleling two sources to the same bus (as mentioned by djacob), voltage levels & phase angle (and the speed at which those phase angles cross must be slow enough for the relay reaction time) the relay allows a signal to pass through to the breaker closing coil to close the incoming unit feeder breaker to the bus. The signal to close can come from an operator holding the "Parallel" button after they have manually adjusted the voltage and speed of the oncoming unit (but the sync check relay won't let the signal pass until 'happy') or the signal can come from a switch placed into the "Auto Parallel" position and then a monitor takes control of engine governors to force speed match automatically with a slight bias so the phase angles will cross slowly.