The series resonance under UHV power can help many power workers conduct various power tests more conveniently.

The AC withstand voltage test is an indispensable and easiest to detect problem in electrical equipment testing. The power frequency high voltage required for the AC withstand voltage test is generally generated through a high-voltage test transformer or its series device. During the boosting process, if the current increases sharply with the regulation of the voltage regulator, but the voltage remains basically unchanged or shows a downward trend, it is due to excessive experimental load and insufficient capacity of the testing equipment. Due to volume and weight limitations, the capacity of the testing equipment cannot be made very large. In order to achieve the purpose of voltage resistance, it is necessary to use reactance compensation for the experiment.

For the tested equipment with a test voltage not exceeding the rated voltage of the experimental transformer and a small electrical capacity, parallel resonance method can be used to achieve it, while for the tested equipment with a test voltage exceeding the rated voltage of the experimental transformer or large capacitance samples, series resonance circuit is often used to obtain high voltage at the power frequency or other frequencies.

Principle of Communication Voltage Resistance

According to different principles, there are generally two types of on-site AC withstand voltage: parallel resonance and series resonance. The advantage of parallel resonance is that when conducting withstand voltage tests on equipment with small capacitance and a required test voltage lower than the rated voltage of the test transformer, the equipment is lightweight, easy to compensate for, and provides a power frequency voltage.

Basic methods for fault diagnosis

When searching for the cause of excessive DC resistance imbalance rate, the following methods should be used:

(1) Based on the wiring method of the tested winding, the error size of the DC resistance imbalance rate can be measured to determine the accuracy of the test value and confirm the target value for fault diagnosis.

(2) It is necessary to collect and adjust the operating conditions in a timely manner, especially when there is a short circuit at the outlet or inlet, fully understand the fault phenomenon and operating parameters, pay attention to the fault process and point, the magnitude and duration of the fault current, analyze the thermal stability state, and make initial diagnosis

(3) It is possible to conduct a comprehensive analysis of insulating oil, and analyze the relationship between its material and the generation of various gas components, the conditions for its generation, and the characteristics of transformer equipment reflected by the test results of various indicators.

(4) Based on the structure and characteristics of the transformer body, and a comprehensive analysis of the current experimental situation, according to the requirements of its own conditions, it is possible to repair the fault location and cause of the DC resistance imbalance rate exceeding the standard, and to reasonably compensate for the degree of damage caused by regulations.

(5) Can identify the fault point and cause, develop a solution to the fault, prepare corresponding equipment and items, and carry out fault handling.

In the design of the AC withstand voltage test device in the power system, attention must be paid to the automatic identification system of the AC withstand voltage test device in the power system. The AC withstand voltage test device in the power system should correctly identify the state of the line components to be protected and accurately distinguish the section where the faulty line components occur.

There are many shortcomings of CNOOC in the design of the AC withstand voltage test device in the power system, such as slow voice alarm speed, repeated low cycle load shedding function, incorrect use of single power meters, and the need to avoid faults in the 35kV transformer of the power system when using the AC withstand voltage test device in the power system. In the transformer integrated automation system, once a fault occurs, the AC withstand voltage test device of the power system processes the fault information systematically, records the obstacle status information, including the time of obstacle occurrence, the type of obstacle occurrence, the tripping situation of the working line, and the recovery time. The power system technicians are based on the information provided by the AC withstand voltage test device of the power system in the substation. Further assess the correctness of protective actions and provide a basis for circuit maintenance.