How to adjust the voltage of an 800KVA oil-immersed transformer?

An 800 kVA transformer is usually 10 or 6 KV. Such transformers generally do not have on-load tap changers, so it is not possible to adjust the voltage while the transformer is in operation. The voltage you are experiencing is unstable, but it remains on the high side. It is recommended that you set the transformer’s voltage ratio to its highest setting. If the voltage remains unstable during production, it is suggested that you contact the upstream substation to use an on-load tap changer for voltage adjustment.

There is a tap changer on the primary side of the transformer. For transformers with a rated voltage of 10 kV, the middle position of the tap changer corresponds to 10 kV; there is one tap above and one tap below this position, corresponding to 10% of the rated voltage, that is, 95,000 V and 105,000 V respectively. This tap changer can be adjusted depending on the level of the output voltage. If the voltage is too high, as mentioned by the poster, the tap changer should be adjusted to the 105,000 V position, which will lower the voltage. A tap changer is designed to allow the output voltage of a transformer to be changed within a small range. It utilizes the principle of changing the number of winding turns to appropriately reduce or increase the output voltage when the input voltage is too high or too low. For distribution transformers, since the primary current is low, tap changers are used to alter the number of turns in the primary winding in order to change the output voltage. Tap changers are divided into two types: on-load adjustment and off-load adjustment. The former allows for adjustment while the load is still connected, without shutting down power supply, whereas the latter requires adjustment only when the power is turned off. Load-free tap changers are generally used in distribution transformers. When the primary voltage of a transformer is too high or too low, the secondary voltage will also be too high or too low, which affects the electricity supply to users. To address this issue, transformers are capable of adjusting their output voltage within a certain range; this is achieved by changing the number of turns in the primary winding through the adjustment of the tap changer connections. The voltage standard value indicated on the transformer nameplate. When the primary voltage rises to 10.5 kV, adjusting the tap changer to position 1 can maintain the secondary voltage at its rated value ； When the primary voltage drops to 9.5 kV, adjust the tap changer to position 3 to maintain the secondary voltage at the rated value as well.