By hvhipot 
1, ultrasonic testing method needs to use ultrasonic bureau
Ultrasonic bureau discharge inspection device is a detection device which can diagnose power line faults by collecting abnormal ultrasonic signals and analyzing them by software. The device can judge the location and type of hidden trouble without power failure. Device by ultrasonic detector (ultrasonic sensor) after collecting abnormal ultrasonic signal, transmission to the host, at the same time, through the analysis of the host built-in software accurately diagnose the fault hazard type and severity level, and converted into audible sound signal and the output waveform, accurate inspection personnel found line fault hidden trouble, prevent the happening of the malignant fault, to avoid the unnecessary power outages, It improves the reliability of power supply, improves the work efficiency and reduces the labor intensity of inspection personnel.
2, pulse current method
Pulse current method is to obtain the actual discharge by detecting impedance, detecting transformer bushing ground wire, shell ground wire, core ground wire and pulse current caused by partial discharge in the winding. It is one of the earliest and most widely used detection methods. International specialized agencies have also developed special standards for this, the current sensor can usually be divided into narrow band and broadband two kinds of frequency band. The narrowband sensor is usually around 10KHZ, which has the advantages of high sensitivity and strong anti-interference ability, but the output waveform is seriously deformed. The bandwidth of the broadband sensor is about IOOKHZ, which has the advantage of high pulse resolution, but low signal-to-noise ratio.
3, chemical detection method
When partial discharge occurs in the transformer, various insulating materials will decompose and destroy, resulting in new products. By detecting the composition and concentration of products, the state of partial discharge can be judged. At present, this method has been widely used in the on-line fault diagnosis of transformer. The type of fault is different, the degree of fault is different, and the composition and concentration of gas are different, so the pattern recognition system can realize the automatic fault recognition. But until now, there is still no unified judgment standard. Because it is more sensitive to the detection of early latent faults, but can not reflect the sudden faults.
4, light measurement method
It is carried out with light radiation produced by a partial discharge. In transformer oil, the light waves emitted by various disdischarged are different in height and length. Studies have shown that it is usually between 500″ and 700mm. The partial discharge can be recognized by detecting the photocurrent characteristics after photoelectric conversion. Although great progress has been made in analyzing partial discharge characteristics and insulation deterioration mechanism by optical measurement method in laboratory, it cannot be widely used in practice because of its complex and expensive equipment, low sensitivity and the need for the detected substance to be transparent to light.
5, radio frequency detection method
It takes the signal from the neutral point of the transformer. The measured signal frequency can reach 30MHZ, which greatly improves the measuring frequency of partial discharge. At the same time, the test system is easy to install, the test equipment does not change the operation mode of the power system, the total of three-phase partial discharge signals can not be distinguished, and the signal is susceptible to external interference. But with the development of digital filtering technology, radio frequency detection method has been widely used in pd online detection.
6. Uhf partial discharge detection
Because of the shortcomings of traditional detection methods, a new detection method, uHF detection, appeared. The PARTIAL discharge detector (UHF local discharge detector) is widely used to detect partial discharge in power systems, including the insulation status of high-voltage switch cabinets, ring network cabinets, voltage/current transformers, transformers (including dry transformers), GIS, overhead lines, and cables.