5 Installation and commissioning
64
BA5831400-00 EN
5.6 Setting temperature gradients (winding temperature)
Since the temperature sensor is located in a thermometer pocket instead of
directly in the winding, the temperature difference between the winding and
insulating fluid must be taken into account. The temperature difference at
nominal load is called the temperature gradient. This is specified by the
transformer manufacturer. The temperature difference is reproduced in the
thermometer by a heating resistor that is supplied with the secondary trans-
former current of the transformer.
Setting the temperature gradient is necessary for thermome-
ters to display the winding temperature. Perform this setting
before commissioning the transformer and before connecting
the current transformer [
The pointer thermometer is set at the factory as follows:
Parameters
Setting
Nominal secondary transformer current
2 A
Temperature gradient
17 K
Nominal heating current for MT-ST160W
1 A
Nominal heating resistance for MT-
ST160WR
6 Ω
Table 6: Factory settings
If the temperature gradient of the transformer deviates from this factory set-
ting, you must adjust the temperature gradient of the thermometer. Depend-
ing on the device variant, there are two different processes to do this:
▪ MT-ST160W(/RM): Gradient setting by heating current
– You need a constant current source and a voltmeter.
▪ MT-ST160WR(/RM): Gradient setting by resistance value
– You need an ohmmeter and, for a second calibration before commis-
sioning, a calibration bath and a current source.
5.6.1 Gradient setting by heating current
For the MT-ST160W and MT-ST160W/RM device variants, set the tempera-
ture gradient by adjusting the heating current.
Summary of Contents for MESSKO MT-ST Compact
Page 25: ...3 Product description 25 BA5831400 00 EN 3 6 Nameplate Figure 9 Nameplate ...
Page 78: ...8 Disposal 78 BA5831400 00 EN Observe the national disposal regulations in the country of use ...
Page 90: ...10 Appendix 90 BA5831400 00 EN NPT adapters optional Figure 73 NPT adapters 1 2 NPT 3 4 NPT ...
Page 91: ......