Synchronization

thank you for your replay

for phase rotation it is ok . but what about other conditions like voltage amplitude and

frequency

thanks

One alters the frequency until the two systems are synchronised, and then one closes the switch. The two then stay synchronised.

If there is a voltage difference between the two sources then the greater will supply current to the lesser. Other equipment sorts this out.

When you synchronize the generator with the bus, the frequency will be exactly right. Once the breaker is closed, increasing the throttle will allow the generator to assume some load (real KW). (The throttle should be set in "droop" mode when the generator is paralled with the bus.)

If the generator voltage is not the same as the bus, there will be reactive current flowing between the generator and the bus (cross current) and the load will appear to the generator to be reactive. The voltage regulator should have circuitry to adjust the voltage to minimize cross current.

http://www.fgwilson.ie/files/generator-set-synchronising-with-and-running-in-parallel-with-a-supply-utility.pdf

I agree. A very primitive but effective method of manual synchronization was the use of a 10 watt clear incandescent light bulb across one incoming/outgoing phase.When the light went totally dark,they were synchronized and the transfer switch was actuated.

This was used on a circa 1950's GE 3.125 MW co gen set.

I've seen generators with two lamps monitoring the voltage between two phases of the generator and bus. When the generator is brought up to speed, the lamps brighten and darken in synchronism and the breaker should be closed when the lamps are dark.

One time a generator had been repaired and the phase rotation had been accidentally reversed. The lamps oscillated out of phase indicating the problem.

In order to check synchronism between generator supply and grid supply, 1-phase voltage vectors are only considered both on generator side as well as on grid side.

If the generator step-up transformer is YNd1, Y-N vector on grid side is matched with y-b on generator side.

Three phase VT at generator terminals has other jobs also to do in addition to providing y-b voltage vector to synchronising scheme (Voltage input to Protection, metering, AVR etc. to name a few).

thanks for all

sorry but suppose the voltage on three phase in grid not equality how we can

depend on only one phase to synchronization (because we have one voltage

transformer in phase/s)

thanks

You are probably meaning slight unbalance in phase voltages that appears due to lack of transposition of conductors in the transmission lines etc.

Bear in mind, synchonisation doesn't mean only matching of voltage magnitude.

It is also

• phase angle,
• speed of voltage vector (frequency) and of course the
• voltage magnitude.

Of these parameters, the tolerance available in voltage magnitude matching is like 5%.

I am sure the voltage deviations in different phases is definitely below the allowed tolerance of 5%.

thank you very much for your replay

Because if one phase is synchronised and the direction of rotation of the two sources is the same, the other two will be as well and there will be much rejoicing when the switch closes.

If they're not rotating in the same direction then one has no business attempting synchronisation, because it simply cannot happen and there will be much misery were one to try, otherwise pronounced "BANG!" and accompanied by blown fuses, smoke and the like. Pure folly.