Over Frequency

Default value

• Dropout: 5%

• Pickup: 20% of delta dropout

Range

Delta Frequency : 2% -> 10% of rated : could be 2 – 3 – 4 – 5 – 6 – 7 – 8 – 9 – 10%..

Differential

The differential between dropout and pick up is fixed on automatic HMI and this differential is set at 20% of the delta value.

Sequence of events

• When a sensor detects a frequency below the set drop-out frequency for a period longer than the time delay, it deems the voltage is out of range.

• When the sensor detects a frequency at or above the pick-up point, it deems the frequency as acceptable.

Example of calculation on overfrequency of TransferPacT Automatic

For example, Fe= 50 Hz , Dropout 5%= 2.5 Hz,

Differential between dropout and pickup= 2.5 Hz * 20%= 0.5 Hz

overfrequency dropout is 50 Hz + 2.5 Hz = 52.5 Hz

Pickup = 52.5 Hz - 0.5 Hz = 52 Hz