| 摘要 |
PURPOSE:To prevent short-circuit between taps by connecting and inserting in series a parallel circuit of fuse and oil-immersed auxiliary contact between a vacuum valve for resistance contact of each pair and vacuum valve for main points. CONSTITUTION:In case cut-off performance of valves WA, WB for resistance contacts is deteriorated and long arc is generated, short-circuit between taps can be prevented by detecting gas and oil flow due to overheat and melting of current limiting resistors RA, RB. In case the cut-off performance of both valves HA, HB for main contacts and WA, WB for contact resistance are deteriorated and longer arc is generated, the oil-immersed auxiliary contacts KA, KB open while the power is being supplied when the exchange proceeds and the arc is generated in the oil. A current flows into the fuses FA, FB by such oil-immersed arc voltage. While the power is being supplied to the fuses FA, FB, exchange loss increases. When the valves HB, HA for main contact in the remote side open, short-circuit is generated between taps. But the fuses FA, FB melt due to a circuit, current flowing in such a case and the short-circuit condition is cancelled. Thereby, tap change of transformer can be realized without giving damage to the tap changer itself under the loading condition. |
