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2.13 Under/Over Frequency (81)
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
This function can be tested by application of 1P or 3P voltage. For Over-frequency, the elements with the highest
setting should be tested first and for Under-frequency the elements with the lowest settings should be tested first.
The elements with other settings can then be tested without need to disable the elements already tested. Note
that the relay is designed to track the gradual changes in power system frequency and that sudden step changes
in frequency during testing do not reflect normal system operation. Normal 'instantaneous' operation of the
frequency element is 140-175ms in line with the Performance Specification. Application of sudden step changes
to frequency can add additional delay which can produce misleading test results.
Gradually increase/decrease applied voltage frequency until 81-n operation occurs. Elements set for more
extreme frequency fluctuation should be tested first with lesser elements disabled.
If the 81-n Delay setting is long it will be advantageous to map the function to temporarily drive the relevant
Pickup output in the Pickup Config sub-menu in the Output Config menu as this will allow the Pick-up led to
operate for the function. If the delay setting is short the operation of the element can be easily checked directly.
The frequency should then be gradually decreased/increased until the element resets. The reset frequency can
be used to check the Hysteresis setting.
If the element is set as 81-n U/V Guarded, The applied voltage must be above the 81 UV Guard Setting in the
U/O Frequency menu.
Apply setting frequency +0.5Hz for Over-frequency or -0.5Hz for Under-frequency and record operating time.
Starting with the element in the operated condition, gradually increase or decrease the applied voltage until the
element resets. Measure the reset voltage level to check the 81 Hysteresis setting.
F
U/O
DTL
(Hertz)
(sec)
If the element is set as 81-nU/V Guarded, this setting can be tested by applying the test voltage at a level below
the 81 U/V Guard Setting at a frequency in the operate range. Increase the voltage until the relay operates.
©2014 Siemens Protection Devices Limited
As per 'Relay Voltage Config' setting.
n/a apply zero current to stabilize other functions
81-n - Self Reset
Hyst.
D.O.
P.U.
(calc.)
Freq
Hertz
Chapter 6) 7SR17 Commissioning and Maintenance Guide
D.O.
Operate
Freq.
Time
Hertz
+/- 0.5Hz
UV
NOTES
Guard
Page 43 of 62
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