The switch cabinet is a kind of electrical equipment. The external line of the switch cabinet enters the main control switch in the cabinet first, and then enters the sub control switch. Each branch circuit is set according to its needs, such as instrument, automatic control, motor magnetic switch, various AC contactors, etc. Today, Martin from Hengfengyou Electric will introduce three detection methods for partial discharge detection of switchgear.
1. Ground wave detection
When partial discharge occurs in the insulation layer of the high-voltage switchgear, electromagnetic wave will be generated, and the metal shell of the switchgear will shield most of this electromagnetic wave.
However, a small part will be transmitted through the joint of the metal shell or the gasket of the gas insulated switch, and a ground wave will be generated and transmitted to the ground through the external surface of the metal shell of the equipment.
The range of the earth wave is usually between several millivolts and several volts, and the rise time is several nanoseconds. The probe can be set on the outer surface of the switch cabinet in the working state to detect the partial discharge activity.
2. Ultrasonic testing
In fact, ultrasonic detection is a kind of mechanical vibration wave. From the perspective of energy, the process of partial discharge is the process of energy instantaneous explosion.
Electrical energy is released in the form of acoustic energy, optical energy, thermal energy and electromagnetic energy. Electrical breakdown occurs in the air gap, and the discharge can be completed in an instant. At this time, the electrical energy will also be converted into thermal energy in an instant. The gas in the discharge center will expand under the effect of thermal energy and propagate outward through sound waves.
The gas in the propagation region is heated to form an isothermal zone, the temperature of which exceeds the ambient temperature; When these gases start to contract after cooling, subsequent waves will be generated. The frequency and intensity of the subsequent waves are relatively low, including various frequency components, with a wide frequency band. The frequency of ultrasonic waves is greater than 20kHz.
Because the area of partial discharge is relatively small, the local emission sound source is the point sound source.
3. Ultra high frequency detection method
In the process of time change, the electromagnetic vibration generated by partial discharge will generate electromagnetic waves. In solid gas and gas medium, the partial discharge pulse will generate very rich electromagnetic wave ultra-high frequency components, up to several GHz.
In the process of practical application, the detection of partial discharge signals can be carried out by two probes. The time sequence of the signals detected by the probes is used as the judgment basis. If the distance between the discharge sources is close, they will be detected first;
The probe position is constantly changing, and the approximate position of the discharge source can be judged step by step. Or through multiple probes, the time difference equations of the probe detecting the partial discharge signal can be set up to obtain the three-dimensional spatial coordinates of the discharge source and finally determine the discharge source.
Hengfengyou Electric Electrical distribution cabinet, distribution board cabinet and distribution pannel,Factory &Manufacturer 30years. sold to more than 50 countries around the world. CB CCC UL KEMA . Hengfengyou Electric will provide you with the best low-voltage distribution solution.【WhatsApp： +86158 5326 5269（Alisa） sales@panel-builder.cn https://www.panel-builder.cn 】
