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Chapter 6) 7SR17 Commissioning and Maintenance Guide
2.12
O
/U
VER
NDER
2.12.1
Phase Under/Over Voltage (27/59)
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
Where more than one Undervoltage (27) elements are being used with different settings, it is convenient to test
the elements with the lowest settings first. The elements with higher settings can then be tested without disabling
the lower settings.
Note that if the voltage is reduced below the 27UVG setting, the function may be blocked. VTS operation may
also block the 27 Undervoltage function. Current inputs are not normally required to stabilise the relay during
voltage element testing.
If the 'O/P Phases' is set to 'All', the voltage on all phases must be reduced simultaneously. Otherwise the 3
phases should be tested individually. If the DTL is short, starting from nominal voltage, slowly decrease the
applied 3P or VL1 test voltage until the Pickup LED (temporarily mapped) is lit. Record the operate voltage. The
LED should light at setting Volts +/-5%. Slowly increase the input voltage until the LED extinguishes. Record the
reset voltage to check the 'Hysteresis' setting. If the DTL is long, the operate level level should be checked by
applying a voltage of 90% of setting voltage. Check Hysteresis by resetting element to the operate level setting
plus the hysteresis setting.
Connect the relevant output contact(s) to stop the test set. Step the applied voltage to a level below the setting.
The test set should be stopped at the operate time setting +/-5%
Test inputs VL2 and VL3 by repeating the above if necessary.
When testing is complete reinstate any of the disabled functions.
Where more than one overvoltage (59) elements are being used with different settings, it is convenient to test the
elements with the highest settings first. The elements with lower settings can then be tested without disabling the
higher settings.
If the 'O/P Phases' is set to 'All', the voltage on all phases must be increased simultaneously. Otherwise the 3
phases should be tested individually. If the DTL setting is short, starting from nominal voltage, slowly increase the
applied 3P or VL1 test voltage until the Pickup LED (temporarily mapped) is lit. The LED should light at setting
Volts +/-5% Decrease the input voltage to nominal Volts and the LED will extinguish. Record the reset voltage to
check the 'Hysteresis' setting. If the DTL setting is long, the operate level can be checked by applying 100% of
setting to cause operation followed by setting minus the Hysteresis setting to cause reset.
Connect the relevant output contact(s) to stop the test set. Step the applied voltage to a level above the setting.
The test set should be stopped at the operate time setting +/-5%
Page 40 of 62
V
OLTAGE
As per 'Relay Voltage Config' setting.
n/a apply zero current to stabilize other functions
47, 81B
27/59-n - Self Reset
©2014 Siemens Protection Devices Limited
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