UOF Protection Summary
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UOF can be configured to trip the switchgear if the measured frequency goes outside of a designated normal band for an unacceptable period of time.
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UOF protection elements can be enabled/disabled individually.
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Settings can be configured within the range 45 Hz to 65 Hz but individual settings must be chosen with respect to other settings and the dead-bands.
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The ACR will not auto reclose after a UOF protection trip but can be configured to close automatically when the frequency returns to normal.
Table 61 Under/Over Frequency Protection Settings/Specifications
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UOF Protection Settings/Specifications |
|
|---|---|
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Frequency setting range(1) |
45...65 Hz |
|
Frequency setting resolution |
0.1 Hz |
|
Accuracy (for sinusoidal input) |
± 0.05 Hz |
|
Frequency dead-band (hysteresis) |
0.2 Hz |
|
Number of under or over frequency cycles before tripping |
2...1000 |
|
Frequency calculation |
Once per cycle averaged over 2 cycles |
|
Low Voltage Inhibit range |
4...23 kV |
|
Low Voltage Inhibit setting resolution |
1 V |
|
Normal Frequency Close Time |
1...1000 s |
| (1) Under/Over tripping frequencies and normal frequencies are interlocked by software so that only viable settings are possible. | |