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4.2.11 Securing of mechanical position
The right position of installed and fixed generator to the foundation must be secured in such a way that
set axial alignment will not be changed in the course of operation. Feet must be plugged in into the
foundation.
4.2.12 Checking the insulation resistance of stator winding
Measure the insulation resistance of the stator winding with respect to the stator core and enclosure prior to
•
commissioning or after prolonged non-operational periods (due to storage or standstill, for example).
Perform the test in accordance with IEEE Std 43 "Recommended practice for testing insulation", see
•
chapter 4.2.13.
Use a suitable insulation tester.
•
CAUTION
Before you begin measuring the insulation resistance, please read the manual for the insulation
resistance meter you are going to use.
Where possible, measure the insulation resistance of the winding with respect to the machine enclosure when
•
the winding temperature is between 20 and 30 °C.
When making a measurement, wait until the measuring instrument display no longer changes. This will take
•
approximately one minute.
4.2.13 Insulation test for stator winding
Before the first commissioning, or after prolonged storage or standstill periods, it is necessary to measure the
resistance of the stator winding to the stator laminations and frame.
It is generally sufficient to conduct this measurement with an insulation test device, such as a megger.
Recommended measuring voltage: 1000 V
Measuring connection: All phases tested together against iron, connection cable and instrument transformer
disconnected.
Minimum value of insulation resistance:
Ω
R
>=10*(U
+1) M
40°C
N
U
= numerical value of rated voltage in kV
n
1) Following IEEE 43
Temperature correction: Halving/doubling of the resistance value is to be expected with temperature increases
/decreases of 10 K.
The values below must be achieved during the measurement.
Conducting the test:
Set up measuring connection, with the winding still earthed
•
Measure the winding temperature with the built in temperature sensors
•
Remove earth connection
•
Switch on insulation test device and take a reading after one minute
•
Switch device off
•
Earth winding
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Product documentation 1D 3.8.en
(1-min-value)
1)
R
50°C
R
40°C
R
30°C
R
20°C
R
10°C
Tab. 5 Minimum value of insulation resistance
Rev. E, 10/13
≥ 14 MΩ
≥ 28 MΩ
≥ 55 MΩ
≥ 110 MΩ
≥ 220 MΩ
page 27/42
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