What are the solutions to the problems associated with high-voltage test transformers?

In the high-voltage test, the insulation of the transformer can be checked by many detection methods, but through people's actual work experience, it can be known that most tests have no way to accurately reflect the change of the insulation of the transformer.

There are many factors that lead to these situations. The most important factor is that during the experiment, the staff did not consider some small links, so that the final experimental data did not, so as to get the wrong results, and then let the actual operation Becomes more and more difficult.

1. Relevant problems of high voltage test of high voltage test transformer

1.1 The voltage polarity and leakage current during the test

When the high-voltage test transformer gets wet, it mainly starts around its outer skin. The most important factor that causes the insulation of the high-voltage test transformer to get wet is the high-voltage test transformer skin.

According to the electroosmosis phenomenon, in the electric field, the water molecules in the transformer exist in the form of a positive charge. However, once the transformer winding is applied with a positive voltage, the water molecules in the insulation will no longer be compatible, so the water molecules are discharged Flow to the housing, so that it contains less water molecules, so the inside of the transformer will cause the leakage current to gradually decrease.

The principle of the opposite case is the same. If a negative voltage is applied to the transformer winding, the water molecules in the transformer will change the same, mainly reflected in:

The water molecules in the insulation will be absorbed, and at the same time will move through the insulation towards the transformer winding. At this time, it will cause the moisture in the area with high field strength in the insulation of the high-voltage test transformer to gradually increase, resulting in continuous leakage current Get bigger.

At the same time, the voltage should pay special attention to the fact that the polarity cannot affect all high-voltage test transformers. The representative case here is the new high-voltage test transformer, and the voltage polarity cannot change the actual measurement data of the new high-voltage test transformer size.

Since the insulation of new high-voltage test transformers will not be damped under normal circumstances, the moisture in it can usually be in the range that is not considered, plus the influence of the electric field, the electroosmosis will become less obvious, so the positive and negative polarity test voltages are carried out During the process, the magnitude of the leakage current obtained is basically the same. For those old transformers, the test voltage polarity will seriously affect the accuracy of the test measurement data.

1.2 The influence of temperature on insulation resistance

As far as the insulation resistance itself is concerned, its induction of temperature is obvious, and many insulation resistances will become very small due to the increase in temperature. Once the temperature rises, the molecules and ions in the insulation resistance will accelerate to collide with each other, so that the polarization problem of the resistance will increase, and the conductance will increase accordingly, which will cause the insulation resistance value to become smaller and smaller.

Not only that, if the temperature keeps rising, the water molecules in the insulating layer will decompose many impurities in a part of the resistance, and this will accelerate the speed of the insulation resistance becoming smaller. If the appearance of the insulation resistance is dirty, the speed at which the resistance becomes smaller will be more obvious.

1.3 The influence of the boosting rate on the measurement of leakage current

Generally speaking, the leakage current is one of the properties of the transformer, and it has nothing to do with the boost rate. However, when we tested, we learned that if a micro-ampere meter is selected for current reading, the value read and leakage There is a large difference between the current values, which is a leakage current that does not actually exist, because there is a small amount of combined current that includes a small amount of absorbed current.

Therefore, the boosting rate will seriously affect the reading size of the leakage current value, especially those larger transformers, the impact is more obvious.

In addition, since the absorption strength of large transformers is particularly good, if you want to make the leakage current read more practical, you should learn some effective skills and corresponding countermeasures. In the actual measurement process, generally do not need to spend a lot duration.

The data shown is only the current value after one minute of pressurization. Obviously, there is some absorption current in this data. There is a certain difference between the measured leakage current value and the boost rate. If the voltage continues to increase, there will be an absorption phenomenon while the voltage increases, and the measured current value is smaller than the actual current value.

If the voltage value is increased in a short time or the increase rate is faster, the absorption phenomenon cannot occur when the voltage is boosted. The measured current is much larger than the actual current, which may cause an error. Analyze the results.

In short, when conducting the insulation test of power transformers, it is necessary to pay attention to the problem of small links, which cannot be ignored, otherwise, it will affect the measurement results, cause misjudgment, lead to wrong conclusions, and give practical work Bring a lot of unnecessary troubles and troubles.

In addition, the hazards of the work site humidity, high-voltage wiring, and remaining charges should be considered to understand the principle of the hazards. At the same time, each test technique should be mastered to accurately read the measurement data to ensure the facility The effective and scientific operation is reasonable and feasible.

If you want to know more, our website has product specifications for transformers, you can go to ALLICDATA ELECTRONICS LIMITED to get more information