How to generate partial discharge and how to measure and prevent it - News - Global IC Trade Starts Here Free

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Kaixin micro test

Test probe P100-M3

Electrical equipment operating in the power grid, such as cables, capacitors, transformers, transformers and motors, is designed to withstand voltage levels based on its operating voltage rating. Under normal conditions, its insulation performance can withstand the operating voltage. Due to poor manufacturing processes, insulation of electrical equipment may leave bubbles, impurities, cracks, etc. inside. Under the action of high-voltage alternating electric field, this kind of insulation will have periodic partial discharge inside the insulation. Since the discharge energy is small, the entire path will not be broken down at once, but the insulation performance may be degraded or even the withstand voltage performance may be lost. Over time, this partial discharge will cause the entire insulation to break down and explode, which will greatly affect the safe operation of the power grid and the reliability of power supply, causing great economic losses to users and society. Therefore, attention should be paid to the partial discharge of electrical equipment.

The partial discharge phenomenon inside the insulation of electrical equipment is periodic, repeats with the change of AC voltage, and discharges when the amplitude of AC voltage is maximum. When the inside of the insulating member is partially discharged, energy in the form of light, sound waves, and the like is also generated.

The measurement methods of partial discharge are generally classified into non-electrical measurement methods and electrical measurement methods.

The non-electrical measurement method is mainly an ultrasonic method, and its purpose is to detect the position of a partial discharge portion. The electric measurement method is a measurement method using a high-frequency pulse current, which is widely used because of its high sensitivity and ease of use. The partial discharge tester is made according to the principle of high frequency pulse current method.

The partial discharge detection can reflect the insulation defects of electrical equipment. This test is non-destructive and, to a certain extent, replaces the destructive withstand voltage test, and the test voltage should be such that it does not cause a penetrating discharge. When the partial discharge amount test of a certain device is performed, the pulse current generated by the partial discharge of the measured object is amplified and sent to the measuring instrument, and after the discharge amount is corrected, the discharge electric quantity value is measured. For different types of equipment and insulation. The amount of discharge is also different. Manufacturers of high-voltage electrical products have factory test standards, which can be evaluated according to standards.

In order to make the power grid operate safely, it is necessary to carry out technical testing of the partial discharge quantity for newly put into operation equipment, and unqualified products shall not be put into operation. For equipment that has been installed in the grid, it must be tested according to the regulations. If it is not qualified, it should be out of operation. In this way, it is possible to avoid major accidents such as explosions caused by partial discharge of equipment and power outages in the power grid.

Pay attention to the test: the wiring of the test circuit must be correct, the contact parts of the wiring must be firm, and the entire test system should be properly grounded. Before the test, put the sensitivity of the instrument at the required minimum value, gradually increase the pressure, and pay attention to observe the indication value of the instrument at any time. If abnormality is found, it should be powered off.

In short. Partial discharge test is one of the important detection methods for detecting insulation defects of electrical insulation structures and oil-immersed insulation structures.