FAQ
Home » Blog » FAQ » Power factor of a generator connected to national grid

# Power factor of a generator connected to national grid

Q: What should be the power factor of a generator connected to national grid in order to have maximum stability? Whether it should be high or low?

1. National grid is like a infinite bus for an average size Generator. We can observe stable operation of generator within its capability limit for all ranges of power factor for infinite time , irrespective of power factor.
2. Observe the load cycle, The generators operate in overexcitation mode (lagging pf) during the day & during night ,when transmission lines generate enough reactive the same generators operate stable in underexcitation mode (leading pf).
3. Therefore as long as there is no instance of large disturbance, we can observe stable operation of generator within its capability limit for all ranges of power factor.

Transient Stability:
1. Depends upon the initial condition of the generator operation (see on Power vs Sin-delta plot)
2 The level of power thrown-off causing the disturbance & Equal area criterion of the energy balance & Inertia.
3 During transient/disturbance, the stability is ensured better if the angle delta (rotor angle or power angle) is small, meaning the amount of store energy in the rotating system is high. Theoretically this means delta angle =0 to have robust stability, but it is practically impossible to have power generation at that value.
4 In order to have maximum stability & power generation simultaneously , the value of rotor angle has to be non zero , on positive side. (negative means motor operation).
To Conclude : It means over-excited mode.(lagging pf ). Many colleges in discussion chain above have written near about 0.9 - 0.94 lagging . They are correct.

Calculate (5 - 1) =

You may also like:

We used four huge 5KV motors and VFDs at the coal mine compared to a single 0.75 HP 480 VAC VFD at the bakery, and startups/shutdowns were order of magnitudes different, but the time frame was immaterial to ...
Large machines are - generally speaking - made of pieces (segments) because the circle for the stator and/or rotor core is too large to manufacture from a single sheet. This leads to some breaks in the ...
When the transition between wye and delta takes place, be very sure that that the mechanical interlocks on the contractors are properly adjusted. If one doesn't completely open before the other closes, you ...
KW is true power and KVA is apparent power. In per unit calculations the more predominantly used base, which I consider standard is the KVA, the apparent power because the magnitude of the real power (KW) is ...
Some of these conditions are convenient and some are mandatory. The convenient conditions are: Same voltage Ratio and Turns Ratio, Same Percentage Impedance, Same KVA Rating, Same Position of Tap changer. The ...
Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.

Featured

Like pumps, fans consume significant electrical energy while serving several applications. In many plants, the VFDs (variable ... A frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ... Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ... Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ... Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...

In Discussion