APFCs for DG Sets

Some gensets are equipped with their own built in PFCs, hence no need to controll PF

It is the load characteristics that determine the need for PFC and the tariff that deterrmines the economics of using them. Ordinarily, PFC is placed at the end of a transmission line to improve power factor within the line and to reduce transmission losses.

If the EB has imposed a penalty on the tariff for low power factor on the new connection then the use of PFC now will be an economic one based on the avoidance of penalty charges to the EB, and this explains the commencement of use.

dear,

good logic !

But,

As you are convinced that State electricity Board give you rebate if the average power during the billing month is maintained at 1.0 ( > 0.96 ) so, definitely, you shall set the APFC instrument for power factor 0.98 or 1.0 .

But, as you shpould be aware that DG sets do not work properly at leading power factor . So, if APFC was ON with DG sets running, with some manufacturer's APFC instruments, as CT current sensed is zero, ( CTs being placed in SB line ), all the capacitors will be switched ON. dg shall operate at leading pf, damaging the shaft or engine.

But now a days, microprocessor based digital APFCs are available that do not switch on all the capacitors , in that case, you could have been started the APFC even priior to SB supply is received. Only, all the capacitors would be off as the CT sensing is at zero current. As CTs are placed in SB line.

Further, I have seen APFC relay with 2 Incomer CTs. You can set different values of PF for each CT incomer.

Incomer 1 - CT placed in SB line - PF set = 1.0

Incomer 2 - CT placed in DG line - PF set = 0.8 lag.