High voltage cable seal defect detection - Application of ACFM technology in power energy field

1 Inspection background:

Lead seal is mainly used for the connection between the end of the liner and the internal cable of the metal protective sleeve. Although the process is cumbersome at present, it is still widely used because of its good strength and aging resistance and reliable sealing performance.

2 Inspection status:

At present, the detection method used for lead seal is visual inspection, which needs to remove the heat shrink sleeve and waterproof belt of lead seal, which is a complicated process and the efficiency is very low. In addition, ultrasonic method, X-ray method and eddy current method are also gradually applied. The ultrasonic method is limited by coupling and needs to remove the surface protective layer for testing, which is mostly used for testing before cable installation. The detection methods that do not remove the outer protective layer include X-ray detection and eddy current detection. The working environment of the X-ray detection site is complex, and the actual operation is difficult. Because the interior of the cable is not complete, there are gaps in the interior, and there are also risks of missing detection and false positives. The eddy current testing method is trapped in the lifting height of the probe, and the lifting height of the ordinary eddy current testing equipment is only 1-2mm, which can not meet the penetration requirements of the protective layer above 5mm of the cable seal.

3 Test method:

Ac electromagnetic field detection (ACFM) is a non-contact nondestructive detection method for surface or near-surface defects based on the principle of electromagnetic induction. By increasing the signal strength, reducing the signal frequency, and improving the attenuation algorithm of the signal in non-conductor materials, the workpiece detection under the protective layer of 5mm thickness is realized.

4 Technical advantages:

1, compared with visual testing and ultrasonic testing, no need to remove the protective layer, direct inspection, saving the cost of testing;

2, no pollution to the environment and human body, to avoid the safety problems of X-ray detection;

3, the detection depth can reach 3mm, lift height can reach 6mm, compared with eddy current detection effect is better;

4, instant output results, improve inspection efficiency, digital inspection, easy to save data, traceability.

5 Typical applications:

1, in service high-voltage cable seal defect detection;

2, power grid tensioning clamp defect detection.