Multi-channel optical fiber ring sound emission detection system based on heterodyne method

Abstract

The invention provides a multi-channel optical fiber ring sound emission detection system based on a heterodyne method and belongs to a sound emission detection technology in the nondestructive test field. The system comprises a distributed-feedback-type narrow-band laser (1), an acoustic optical modulator (2), a first optical fiber coupler group (3), an optical fiber ring sensor group (4), a reference optical fiber ring sensor (5), a second optical fiber coupler group (6), an interference coupler group (7), a balance detector group (8), a mixer group (9) and a demodulation system (10). By using the system of the invention, partial discharge of a transformer can be measured in an online and real-time mode and most of defects of a traditional electric sensor are overcome.

Description

technical field [0001] The technology of the invention belongs to the acoustic emission detection technology in the field of non-destructive testing, and mainly relates to a fiber ring acoustic emission detection system based on a heterodyne method, which is used for measuring partial discharge acoustic emission signals of power transformers. Background technique [0002] Partial discharge, referred to as partial discharge, its English abbreviation is PD (Partial Discharge); refers to in high-voltage equipment, when the field strength generated by the applied voltage in the electrical equipment is sufficient to cause discharge in the insulating part of the area, but no discharge is formed in the discharge area. A discharge phenomenon of fixed discharge channels. Generally, a weak acoustic signal will be emitted along with the partial discharge, which is called the acoustic emission signal, and the judgment of the partial discharge can be completed through the verification of...

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Problems solved by technology

[0004] Since the transformer is in the internal environment of strong electromagnetic interference during operation, this directly leads to the inability of the equipment based on electric operation to operate reasonably due to strong electromagnetic field interference, so the traditional partial discharge method has the following main defects: (1) Because the transformer is in a strong electromagnetic field during operation, it is impossible to measure various conditions of the transformer during operation, which makes the experimental environment different from the operating environment, so the experimental results of the transformer cannot be the closest to the real results

(2) Although the weak partial discharge will cause slow changes in the insulating medium, there are still many damages caused by a single, strong partial discharge. The monitoring method based on electricity cannot monitor in real time, resulting in the failure to repair in time mistake

(3) Traditional regular maintenance and insulation preventive tests need to be tested offline after a power outage, which prolongs the test time and increases redundant work. Frequent power outages will also cause unpredictable damage to other equipment

[0006] The first one: use the piezoelectric effect of piezoelectric ceramics to detect acoustic emission signals. The advantages of this monitoring method are its high sensitivity, long development time, relatively mature technology, and easy networking. Multi-point monitoring can monitor the location of the acoustic emission source, but because it is an electrical sensor, it does not have the ability to resist electromagnetic interference and can only be installed outside the transformer, so it cannot identify weak acoustic emission signals, which limits it. Applications

[0007] The second method: use the optical F-P cavity as the sensor for measurement and fiber grating as the sensor for measurement. Although these two measurement methods are based on optical sensors, their system configuration costs are relatively high because of their sensing principles, which is inconvenient. Networking, forming multi-channel, multi-point measurement, it is not easy to locate the source of acoustic emission

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