How To Adjust The On-load Tap Changer Of The Static Voltage Stabilizer?

In order to ensure the power supply quality of long-distance lines, the general substation is equipped with a dedicated 10/10kV Static Voltage Stabilizer. The static voltage stabilizer has the function of automatic voltage regulation on load, and the power is supplied to the line through the static voltage stabilizer.

The structure and principle of the static voltage stabilizer are similar to those of the transformer. It uses the principle of electromagnetic induction to change the impedance and voltage distribution of two coils with equal turns and anti-phase series connection to adjust the output voltage. It is essentially a 1:1 transformer.

The connection methods of the static voltage stabilizer winding include star grounding, star ungrounded and triangle connection.

The two independent incoming power supplies of the substation are provided by the public power grid, and the incoming voltage levels are 10kV, 35kV, 110kV, 220kV, etc. The substation is generally equipped with a static voltage stabilizer, and its basic rated transformation ratio is 10/10kV. When the voltage on the main bus side changes within the range of 0.875-1.125 times the rated voltage value, the static voltage stabilizer adjusts the tap to maintain the voltage on the line bus side at around 10kV. The static voltage stabilizer generally has 9 gears, and the ratio coefficient is changed by adjusting the gear. For example, when the main bus voltage is 0.875 times the rated voltage, the tap should be in the 9th gear; when the main bus voltage is 1.125 times the rated voltage, the tap is in the 1st gear. The driving motor of the static voltage stabilizer generally uses a two-phase power supply, and the protection device respectively opens the boost or buck relay to charge the capacitor forward or reverse, thereby changing the lead and lag relationship of the two-phase power supply, driving the motor to rotate in the forward and reverse directions, and driving the gear switching mechanism to realize the boost and buck functions.

How is the tap switch of the transformer adjusted?

The tap changer of a 10kV transformer has three positions, and the voltage adjustment range is ±5%. When the voltage change of the system does not exceed ±5% of the rated voltage, the problem of over-high or under-low voltage can be solved by adjusting the position of the transformer tap changer. For a distribution transformer with no-load voltage adjustment, the tap changer has three gears, namely, gear Ⅰ, which is 10500/400V; gear Ⅱ, which is 10000/400V; gear Ⅲ, which is 9500/400V. When the system voltage is high and exceeds the rated voltage, the secondary bus voltage of the transformer is high, and the transformer tap changer needs to be adjusted to gear Ⅰ. If the system voltage is low and does not reach the rated voltage, the secondary voltage of the transformer is low, and the transformer tap changer needs to be adjusted to gear Ⅲ. This is the so-called "high to high, low to low". However, the adjustment of the transformer tap changer should be relatively stable and should not be adjusted frequently, otherwise it will affect the operating life of the transformer.