Everyone knows that,the regulating device of the transformeris divided into the transformer “no excitation” regulating device and the transformer “with load” regulating device.
Both refer to the transformer tap switch voltage regulation methods, so what is the difference between the two? Let us first understand the definitions of the two:
①”No excitation“voltage regulation, is to change the transformer’s primary and secondary sides are both disconnected from the power source high-voltage side tap to change the number of turns ratio for voltage regulation.
②On-load voltage regulation: By using the on-load tap changer, the tap position of the transformer winding is changed without breaking theloadcurrent, thus changing the high-voltage winding to regulate the voltage.
It can be seen from the above that the difference between the two is that the no-excitation voltage regulating switch does not have the ability to switch gears with load, because this type of tap changer has a short-time interruption process during the gear switching process, which will cause arc between contacts and damage the tap changer, while the on-load voltage regulating device has an intermediate resistance during the gear switching process, and there is no short-time interruption process, from one gear to another gear, thus there is no arc between contacts caused by the interruption of load current. It is generally used for transformers with strict requirements forvoltageand frequent gear switching.
Some friends may ask, since the “on-load” voltage regulation device can achieve the voltage regulation function of the transformer under the operating state of the transformer, why choose the “off-load” voltage regulation device? Everyone won’t have their brains dug out.
Of course, first of all, it’s the price!
Under normal conditions, the price of a no-excitation voltage regulator transformer is 2/3 of the price of a on-excitation voltage regulator transformer; at the same time, the volume of a no-excitation voltage regulator transformer is also much smaller because it does not have a on-excitation voltage regulation part. Therefore, in the absence of a regulation, or in other cases, a no-excitation voltage regulator transformer will be selected.
Speaking of the voltage regulating device of the transformer, some friends will ask, why choose the on-load voltage regulation of the transformer? What is its function?
Improve the voltage qualification rate
Power systemDistributionPower transmission in the network, the generated losses, only at the rated voltage its loss value is the smallest. Carrying out on-load voltage regulation, often maintain the qualified voltage of the substation busbar, so thatElectricalEquipment operates at the rated voltage state, will reduce losses, is the most economical and reasonable. Voltage qualification rate is one of the important indicators of power supply quality, timely carrying out on-load voltage regulation, can ensure the voltage qualification rate, so as to meet the needs of people’s lives and industrial and agricultural production.
Improve reactive power compensation capability, improvecapacitorinjection rate
Power capacitors, as reactive power compensation devices, their reactive power output is proportional to the square of the operating voltage. When the operating voltage of the power system decreases, the compensation effect decreases, and when the operating voltage increases, it can cause overcompensation of the power-consuming equipment, causing its end voltage to increase, and even exceed the standard regulations, which can easily damage the equipment insulation and cause equipment accidents. In order to prevent the reverse transmission of reactive power to the power system and stop the reactive power compensation equipment, resulting in the waste of reactive power devices and the increase of loss, the main transformer tap changer should be adjusted in time to adjust the bus voltage to the qualified range, so as not to stop the compensation of capacitors.
Okay! Let’s understand the internal structure of the on-load tap changer device together!
From the above figure, it can be understood that the on-load tap changer of the on-load regulating device consists of a switching switch (including the switching switch body and oil chamber) and a tap changer (with a polarity changer).
After the above four processes, the switch with load has completed the seamless connection of the voltage regulation with load. So, when can a transformer not be used for on-load voltage regulation? ①Transformer overload operation (except in special cases) ②When the light gas protection of the on-load tap changer trips and alarms ③The oil withstand voltage of the on-load tap changer is not qualified or there is no oil in the oil level gauge. ④The number of pressure adjustments exceeds the specified number of times ⑤When the pressure regulating device malfunctions Some children may ask, it’s reasonable to prohibit the adjustment of the on-load tap changer in case of abnormal conditions of the on-load tap changer, but why is the on-load tap changer also locked when overloaded? This is because the main transformer normally has a voltage difference between the main contact and the target tap during the load-adjusted voltage process, which in turn creates circulating current. Therefore, during the voltage adjustment process, a parallel resistor is connected to bypass the circulating current and the load current. The parallel resistor needs to withstand a large current. When the main transformer is operating under overload conditions, the operating current of the main transformer may exceed the rated current of the tap changer, causing the auxiliary contacts of the tap changer to weld. So in order to prevent the arc phenomenon of the tap changer, it is forbidden to perform on-load voltage regulation when the main transformer is over-loaded, and if the on-load voltage regulation is forced, it may cause the on-load voltage regulation device to burn out, the heavy gas of the on-load voltage regulation device to act, and the main transformer switch to trip
