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Partial discharges (PDs) are an electrical phenomenon that occurs within a transformer whenever the voltage stress is
sufficient to produce ionization in voids or inclusions within a solid dielectric, at conductor/dielectric interfaces, or in
bubbles within liquid dielectrics such as oil; high-frequency transient current discharges will then appear repeatedly and
will progressively deteriorate the insulation, ultimately leading to breakdown. Fiber sensor has great potential on the
partial discharge detection in high-voltage equipment for its immunity to electromagnetic interference and it can take
direct measurement in the high voltage equipment. The energy released in PDs produces a number of effects, resulting in
flash, chemical and structural changes and electromagnetic emissions and so on. Acoustic PD detection is based on the
mechanical pressure wave emitted from the discharge and fluorescent fiber PD detection is based on the emitted light
produced by ionization, excitation and recombination processes during the discharge. Both of the two methods have the
shortage of weak anti-interference capacity in the physical environment, like thunder or other sound source. In order to
avoid the false report, an all-fiber combined PD detection system of the two methods is developed in this paper. In the
system the fluorescent fiber PD sensor is considered as a reference signal, three F-P based PD detection sensors are used
to both monitor the PD intensity and calculate the exact position of the discharge source. Considering the wave band of
the F-P cavity and the fluorescent probe are quite different, the reflection spectrum of the F-P cavity is in the infrared
region, however the fluorescent probe is about 600nm to 700nm, thus the F-P sensor and fluorescent fiber probe can be
connected in one fiber and the reflection light can be detected by two different detectors without mutual interference.
The all-fiber partial discharge monitoring system not only can detect the PDs but also can ensure the position of the PD
source and is of great anti-interference capacity in harsh environment.
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