Specifications

7SR242 Duobias Description Of Operation

3.13 Voltage Protection: Under/Over Frequency (81)

Optionally six under/over frequency elements are provided.

Frequency elements are blocked if the measured voltage falls below the 81 U/V Guard setting.

The sense of the element (under-frequency or over-frequency) is set by the 81-n Operation setting.

81-n Setting sets the pick-up frequency for the element.

An output is given after elapse of the 81-n Delay setting.

The 81-n Hysteresis setting allows the user to vary the pick-up/drop-off ratio for the element.

Operation of the under/over frequency elements can be inhibited from:

Inhibit 81-n A binary or virtual input.

81-n U/V Guarded Under voltage guard element.

Figure 3-20 Logic Diagram: Under/Over Frequency Detector (81)