| 摘要 |
PURPOSE:To avoid the unnecessary operation of a ground relay by circulating zero-phase currents by installing a zero-phase impedance on the bypass circuit side and inhibiting circulation of zero-phase currents by the impedance. CONSTITUTION:Each phase current on the normal power supply side is composed only of a positive phase component and a negative phase component normally, but zero-phase currents circulating in a closed loop are generated by the unbalance of the impedance between each phase and each branch constituting the closed loop when each phase current is shunt to a bypass circuit 13. Positive phase component and negative phase component currents are not made to flow through the neutral-point residual circuit of a current transformer CT37 at that time because the sum of three phase components is brought to zero, and is made unrelated to the switching of a switch 3. On the other hand, zero phase component is made to flow through the neutral-point residual circuit when the switch 3 is closed, but the zero phase component is limited by zero-phase suppress impedances 2 when the switch 3 is opened. |
