Power issue

To understand reactive power it is essential to know the load.In simple terms KVAR is power wasted by system. It is not generated .Think your load is Induction Heating the system is highly inductive resulting in CosΦ less than 0.5 you cannot avoid it so we have to correct it by adding Capacitors in circuit to improve power factor and reduce reactive power. Similarly induction motors are also Inductive load. So the most appropriate method is to correct at load centre itself.For resistance furnaces the power factor is almost unity hence reactive power is practically nil. Automatic Power Factor Correctors (APFC)has to be installed at all Distribution substations and Main Receiving Stations to improve Power Factor and reduce KVAR PF up to 0.95 is reasonably good .to achieve beyond that is not economical.

always talk in our discussion about reactive power indead if we think deeply what is reactive power?

• Philosophically speaking-it is INACTIVE POWER : the current Sinusoid is leading/lagging the Voltage Sinusoid by angle φ radian in a cycle's total 2Π radians.Current Not working in full Rythm with Voltage.

how it generates?

• The Reactances(+ve by Inductors,_ ve by Capacitors) causes Load Current to LAG/LEAD the Voltage vector.That is how Reactive Current HAPPENS(generates)

what is its affect on the entire system ; #generation

• If load going out of generator is Leading/Lagging much, then as the Current I_max. is a limiter,you cannot get the max. possible Kilowatts out of generator. P_{KW. MAX} can not be taken out of Generator.You will have to be happy with P_actual=P_{KW MAX.}. cosφ. So you cannot get maximum possible out of the GenSet+Dam/GasTurbine/SteamTurbine/Diesel Engine prime mover!

What is its effect on Transmission? Similar to above:

• If Transmission line can carry no more than I_max you are carrying less than maximum Kilowatts- hence less you earn money by selling SO MANY KILOWATTS only.(P_kw.max.cosφ)

On Distribution Transformer--SAME loss( limitation is max. Current at Secondary)

So what is the best thing to do: If you can --Minimize Leading and Lagging angle φ that is Maximize Power Factor =Cosφ

How? Not now please!

Would like add a bit. The capacitors and inductors are charging & discharging devices by characteristics of materials. Both these materials charges in one cycle and discharges in another as per time constant. Hence the system will not see any power consumed by these. But the Energy is lost due to losses in charging and dis-charing.

Hence it is wasteful of energy. All the equipments like UPS, DG, Transformers are rated for 0.8pf. Hence true power required by the loads to do the work is reduced. Hence in order to have better reliability we need to check, measure & de-rate the systems.

Dynamic VAR compensator are also available now in order to keep the power factor in control. These are real time and no matter whether it is lag or lead, the compensation is done.

The entire effect of reactive power to both generation and trasmissinon is that if you have low MVar the the generator terminal voltage will be less say if your gen output is 11kV and your MVar is 12 then you may have a low terminal voltage of say 10.7KV depending on the sation consumption and excitation. The effect of this on transmission is that if your MVar is less then the transmision line voltage will actually be low for example if it is 133KV then it may tend to fall as low as 127KV.

If at your genearting plant you have room for more reactive power then you can adjust the entry point to maintain the line voltage but if your at the maximun then tell you control center to put in capacitor banks. The line voltage will then be maintained.

Thats the effect of MVar, KVar , Var what ever you would like to call it.