The AC withstand voltage of the transformer is the impact transformer

Friend, you have confused the rated capacity of the transformer with the capacity of the test transformer. The rated capacity of the transformer refers to the ability of the transformer to run with load, and the capacity of the test transformer is only related to the test load, that is, the capacity of the test transformer and the test console are matched, just like the text description of the annex, because the test console has limited current resistance, ball gap and other protection measures, and the output of the test transformer will be cut off if the protection setting value of the test console is exceeded, so as to protect the transformer and the console from destruction. At the same time, it prevents unnecessary damage to the DUT due to excessive test current.

KVA is the unit of apparent power.

w is the unit of active power.

var is reactive power.

m is a trillion (an order of magnitude 10 to the 6th power).

v is the unit of voltage.

1 mv = 1000000 v

Apparent power 2 = active power 2 + reactive power 240000kva is the quota capacity of the transformer is the apparent power (is the capacity of the No. 1 main transformer in the figure).

250kVA is the apparent power (rated capacity) of the transformer of the test power supply to provide power to the test instrument.

Also, there are several mistakes in the units written above, and the k in 250kva 40000kva= should be lowercased.

and 150kv v to be capitalized.

The test power supply is only 250kva = VA in MW to be capitalized.

When doing the withstand voltage test, the high-voltage side is connected to the transformer winding, and the transformer winding basically does not leak electricity to the shell and ground, so the current is very small, and the current is multiplied by your AC withstand voltage value is the output capacity of the test transformer, which is very small, so it is much smaller than your capacity of 40000kva

The allowable inrush current on the high-voltage side of the transformer refers to the transient overcurrent that is allowed in a short period of time on the high-voltage side of the transformer under normal operating conditions, which is usually called "inrush current" or "switching overcurrent". This kind of current is due to the power switch, capacitor, inductor and other circuit elements on or off the instantaneous overcurrent, its amplitude and time is very short, but may cause thermal damage or other damage to the transformer.

In order to prevent the transformer damage caused by the inrush current, an overcurrent protection device is usually set on the high-voltage side of the transformer, and when the inrush current exceeds the rated current of the transformer, the overcurrent protection device will automatically cut off the circuit to protect the transformer from damage.

It should be noted that different types and specifications of transformers, the allowable impulse current size and time are different, and the specific situation needs to refer to the technical parameters and operating instructions of the transformer to ensure the normal operation and service life of the transformer.

The inductive element on the transformer, when the transformer closes with a phase of power that happens to close the voltage crossing zero, because there is no back EMF, there will be an impulse current flowing through this phase.

The transformer is an inductive element, so there will be an inrush current.

Check whether the equipment can withstand the impact of high voltage and high current. (When the no-load transformer is opened, it is possible to produce an operating overvoltage, and when the neutral point of the power right system is not grounded or grounded through the arc suppression coil, the overvoltage amplitude can reach multiple phase voltage; When the neutral point is directly grounded, it can reach 3 times the phase voltage, and in order to check whether the dielectric strength of the transformer can withstand the impact of full voltage or operating overvoltage, an impact test is required.

When energized into the no-load transformer, there will be an excitation inrush current, the value of which can reach 6-8 times the rated current. The excitation inrush current begins to decay quickly, generally after the reduction to double the rated current value, but the complete attenuation time is longer, the large-capacity transformer can reach tens of seconds, because the excitation inrush current produces a large electrodynamic force, in order to assess the mechanical strength of the transformer, and at the same time assess whether the initial stage of the excitation inrush current attenuation can cause relay protection malfunction, the impact test needs to be done. ）

As the name suggests: the impact test is to test the mechanical properties of the transformer. Because the power transmission will produce an excitation inrush current, this inrush current will produce a lot of electrical power to the winding, and the unqualified transformer winding will be deformed, so the new production will be impacted 5 times, and the overhaul will be impacted 3 times.

The impact test is to test whether the transformer can withstand the inrush current and excitation inrush current in a short time.

The bearing of the winding and body under the action of point force.

1. Assess the insulation level of transformer;

2. Assess the excitation ability of the transformer core;

3. Assess the level of transformer anti-electric power;

4. Assess the setting value of transformer relay protection.

Test the mechanical strength of the transformer under the excitation inrush current.

In production practice, due to the particularity of the operation wave on the insulation of ultra-high voltage equipment, the voltage distribution inside the internal insulation is different from the voltage distribution under the capacitant lightning wave and the power frequency voltage. Therefore, the equivalent power frequency voltage cannot be used instead of the effect of internal overvoltage, but the operating impulse voltage should be used to test the electrical strength of the insulation. This kind of impulse voltage generator is used to generate standard impulse voltage waves and voltage values to test the insulation performance of ultra-high voltage electrical equipment under the action of lightning overvoltage or operating overvoltage.

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Pro-220kv transformer impact test low voltage side can impact oh 1, transformer impact closing test does not necessarily have to be carried out from the high voltage side, which is related to the application of the transformer. Generally, this test is combined with the operation of the transformer. Since most of the step-down transformers we use are Xixu, the incoming side is naturally on the high-voltage side, so we can only impact the high-voltage side from the high-voltage side.

If the step-up transformer of the power plant is on the low-voltage side, it will be impacted from the low-voltage side. For those with reverse power transmission capability, the main transformer can be done from the high-voltage side. There will definitely be an excitation inrush current when the transformer is charged at full voltage, but the size is different each time.

The magnitude of the excitation inrush current is related to the remanence and closing angle (non-periodic component) factors! The results are: the maximum voltage is doubled, the magnetic flux is doubled, the supersaturation is supersaturated, and the current increases suddenly.

2. The number of impact tests: before the main transformer is put into operation for the first time, it should be closed by impact under the rated voltage for five times, and the duration after the first power reception should not be less than 10 minutes, and the interval between each time should be greater than 5 minutes. After the overhaul, the main strain impact is three times; The gas lower float should be tripped before the main transformer impact closing, the impact closing is normal, and the no-load charge is 24 hours under conditions; When the transformer of 110 kV and above is started, if there is a condition, zero voltage boost should be used; The on-load voltage regulating device of the transformer should be switched normally when the transformer is put into operation before it can be put into use.

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