1. General

Today are discussed the principles of synchronizing, Today are discussed the principles of synchronizing, accomplishing it. In theory, there are a minimum of two simple measurements or indications, which may be used for synchronizing a generator to a grid.

When two voltages satisfy the conditions of being equal in magnitude, have an equivalent frequency and an angle of zero between them, then round the voltage loop they add to be zero at each and each instant of your time on the sine waves. Consequently voltmeters connected across each of the synchronizing breaker contacts will both read zero. Lights placed within the same position also will be totally out when all the synchronizing conditions are satisfied.

In practice, we’d like information which the voltmeters and lightweight won’t give us so as to synchronize a generator to the grid. During the actual physical process of synchronizing, we want to know whether the generator or the grid is fast and by how much. The instrument, which can provide this information, is that the synchroscope Figure Show the connection of synchronous scope between the Generator synchronize and there for the grid.


We will still get to use two voltmeters to see that the generator and therefore the grid voltage are an equivalent (noting that these two voltmeters aren’t those referred to above, since those ones were placed across the synchronizing breaker contacts).

The position of the synchroscope pointer indicates the difference in angle between the generator voltage and therefore the grid voltage. When there’s a zero angle between the 2 voltages, the synchroscope pointer is within the vertical or 12 o’clock, position.

The speed of rotation of the pointer indicates the difference in frequency of the 2 voltages. The pointer will rotate within the Slow or counter clockwise, direction when the generator frequency is below the grid frequency. The pointer will rotate within the Fast or clockwise, direction when the generator frequency is bigger than the grid frequency. It should be acknowledged that the synchroscope will only rotate for little differences in frequency of up to 2 Hz. With larger frequency differences, the synchroscope is meant to not rotate

The last two paragraphs indicate that when:

• The pointer is vertical or at 12 o’clock,

• The pointer is steady, not rotating; then the 2 voltages are in phase and therefore the frequencies of the generator and grid are equal

In practice the synchronizing breakers are closed when the generator is simply slightly fast and at about the 5 minutes to 12 position moving toward 12 o’clock. This allows a touch little bit of time for closing the synchronizing breakers and it assures that the generator won’t act as a motor once the synchronizing breaker is closed.

It is important to see the right operation of the synchroscope before each synchronizing is attempted. To do this, the generator is operated at but synchronous speed and therefore the synchroscope must rotate within the slow direction. Similarly when the generator is operated at a speed greater than synchronous, the synchroscope must rotate within the Fast direction.


Now that the generator is at the purpose where the output breakers are often allowed to shut, consideration has got to be taken on the external electrical system. In the previous section, we considered that the electrical system was already energized which we were within the process of synchronizing with it. This not only is that the normal process, but also allowed clearer explanations of the parameters involved.

Before we proceed with this intimately, we should always check out things of learning a de-energized load or often called load. All of the above factors still apply. The generator must be operating at rated voltage and frequency, plus have the AVR and speed controller in commission. The last two items are going to be covered in additional detail later. The first concern is that the amount and sort of load which will be picked up and what the expected results are going to be on the generator.

The magnitude and type of load has a unique impact on the turbine-generator through the output medium – the current. As you’ll recall at the beginning of the series on electrical equipment the generation of electricity is really the method of pushing electrons or pushing current. Also recall that a generator is nothing quite a transformer with a rotating primary coil. The current draw on the secondary coil (stator) will in fact affect the first winding

2.1. Armature Reaction

When the generator is loaded and current flows in the stator conductors, there is a second flux φS produced by the stator coils. Armature reaction is that the interaction of the magnetic flux s of the stator φS and rotor φR windings that produces a resultant magnetic field mentioned because the air gap flux. Armature reaction has the subsequent three characteristics:

2.1.1. Active Component

The active component of the present that produces Real or Active power weakens the flux linkage across the air gap. The flux linkage within the air gap stretches (Figure 15). If the MW loading increases, without increasing the exciter voltage, the flux lines get stretched more, this suggests that the load angle increases. This can’t be allowed to happen or a pole slip may occur as discussed previously. Hence as load increases the exciter current has got to be increased (over-excitation) to take care of the strength of the sector. Although it’ll be discussed later, it should be noted that an important fault current can pull the generator out of step and pole slip occur because the prime-mover (steam) and automatic transformer (AVR) cannot react fast enough to correct the flux deficiency.

armature reaction

2.1.2. Reactive Lagging Component

With a lagging load on the generator, lagging current is pulled from the stator and therefore the generator is seen to be producing MVARS. The lagging stator current creates a resulting flux that directly opposes the sector flux. As evoked voltage is proportion to flux(V α f) the generator output voltage drops to take care of rated voltage the rotor field must be magnified and therefore the generator then become over-excited.

2.1.3. Reactive leading element

With a number one load on the generator, insulation current is equipped to the mechanical device and therefore the generator is to be engrossing MVARS. The mechanical device current creates a ensuing flux that directly assists the sphere flux. As evoked voltage is proportional to flux (V α f) the generator output voltage can increase. To take care of rated voltage the rotor field must be deceased and therefore the generator then becomes under-excited.

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