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2.9
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. Current inputs are not
required to stabilise the relay during voltage element testing.
If the DTL is short, starting from nominal voltage, slowly decrease the applied 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 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%
©2010 Siemens Protection Devices Limited
7SR242 Duobias Commissioning & Maintenance Guide
Figure 2-11 Phase Under/Over Voltage
V
(V
)
1
X
n/a apply zero current to stabilize other functions
59N
27/59-n - Self Reset
Chapter 6 Page 38 of 57
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