| 摘要 |
The electrical stray field is scanned in the surrounding of the covered conductor, after which the impulse components, which are purposely digitalized and further frequency filtered, are separated from the obtained signals, which takes place by eliminating to 20 kHz high frequency signals. After the frequency filtration process the effective values of the impulse components, which correspond to a defined and pre-set time period and selected length of time intervals, are computed. The values are registered and the effective values which correspond to diverse time scanning periods are subsequently and/or simultaneously compared. Faults in the medium voltage covered conductors are detected by comparing the common values. The apparatus (1) includes an electrical stray field sensor (3) which is connected through the impulse component detection unit (55) to the frequency filter (7), which is further connected to the to the computing unit (8) whose output (82) is linked to the evaluation unit (9). The impulse component detection unit (55) is purposely assembled from the voltage divider (4) and the impulse component dividing device (54). The voltage divider (4) is purposely capacitive and the electrical stray field sensor (3) is toroidal and encircles the insulation of the covered conductor (2). The A/D converter (6) is inserted either between the impulse component detection unit (55) and the frequency filter (7), or the impulse component dividing device (54) and the frequency filter (7). The computing unit (8) is purposely coupled with the evaluation unit (9), whereas the evaluation unit (9) can be connected either with the remote access device (93) or the remote access device (93) is integrated to the evaluation unit (9). |
