Operation - Siemens GEAFOL Neo Operating Manual

8. Operation

8.1 Voltage regulation. If the actual grid voltage deviates from the rated voltage of the transformer, the
tapping gear of the transformer can be adjusted appropriately to control the output voltage value.
a. For no-load voltage regulation, the transformer gear tap shall be adjusted to the appropriate gear to keep in line
with the grid voltage.
For example: The rated voltage on the high-voltage side of the transformer is 10000 ± 2 x 2.5% V, and the rated voltage on
the low-voltage side is 400V. The nameplate identification gear voltage of the transformer is:
Rated voltage
If the grid voltage is 10000V, the three-phase tap shall be adjusted to gear 4-7, as shown in Figure 1. If the input voltage is
up to 10250V, adjust the three-phase tap to gear 4-6 so that the output voltage on the low-voltage side reaches 400V, as
shown in Figure 2. If the input voltage is as low as 9750V, adjust the three-phase tap to gear 3-7 so that the output voltage
on the low-voltage side reaches 400V, as shown in Figure 3.
Figure 1
Warnings:
• The gear of transformer is set at rated gear (4-7) by default when it leaves factory. Make sure that the transformer is powered off
before adjusting the gear.
• The three-phase tap must be adjusted at the same time. The rear gear bolt must be tightened after adjustment and the torque value
must be restored.
b. For on-load voltage regulation, please refer to the operation manual of on-load tap changer.
8.2 When large capacity no-load transformers are put into operation, visible sparks may be generated at
the joints of external components (especially at the core and clamps), but this phenomenon will soon
disappear. This is due to physical reasons, and will not affect the safe operation of the transformer, so
it is not a product defect.
8.3 There is inrush current when the transformer is switched on, and the peak value can reach 6-8 times of
rated current. The setting value of current quick protection for the transformer shall be larger than the
peak value of inrush current, and the time limit shall be ≤ 0. 5 s. Therefore, no-load inrush impulse test shall
be carried out before operation to check whether the relevant protection of the transformer is malfunction
or not. If the protection value is set improperly, it will cause the tripping phenomenon in the later closing.
Remarks:
It depends on the needs of users and the standard requirements of different countries and regions to decide whether the no-load
inrush impact test is to be carried out at site or not.
8.4 For long-term storage (storage time more than 3 months) or overhauled transformers or transformers
to be used at ambient temperature below 0 ℃, it is recommended to operate without load for 12
hours before putting the transformers into load, and the load shall be gradually increased.
5-6
4-6
4-7
3-7
3-8
Figure 2
10500V
10250V
10000V
9750V
9500V
400V
Figure 3
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