| 摘要 |
<p>PURPOSE:To improve the detecting sensitivity of a zero-phase current to a large extent, by shielding the outer surface part of a magnetic core with a magnetic shield member which is formed by laminating high-permeability magnetic materials having the different operating magnetic fields. CONSTITUTION:Magnetic fields are generated by three positive-phase currents through three-phase conductors which are provided through the inside of a zero-phase current transformer 1. The magnetic fields are attenuated through magnetic shielding layers gradually from the outside. The magnetic fields reaching a magnetic core 5 become very small. Meanwhile, when the zero-phase current flows through any one of the three-phase conductors due to the occurrence of a grounding fault, magnetic flux is induced in the magnetic core 5. A coil 6 detects this fact and sends a signal to an optical voltage sensor 4. The optical voltage sensor 4 detects the signal highly sensitively without induction and outputs an optical signal.</p> |
