Power factor correction

We are operating a Mini grid with 13200volts transmission line extending to about 4km to the last load. Our generator sets are only 40 to 90 KW, and most of these are operating at about 50% of the capacity. With this load condition, we noticed that the power factor of the six systems are almost the same, between 60% to 70% only. Our generators are 480volts, these are then transformed to 13200volts for the transmission/distribution. At the load side, these are then stepped down to 220volts for household use. The system is line to ground. Considering the above conditions what could be the cause of the low power factor. The average number of transformers connected to the system are 9, these includes the three single phase connected in delta-Wye configuration for voltage step up from the generator. I am not yet registere