| 摘要 |
<p>PURPOSE:To enable voltage detection with high measuring accuracy, by connecting an electrooptical element modulating optical power corresponding to the electrical change in a plurality of phases to the intermediate part of a light transmission path in series. CONSTITUTION:According to the currents flowing to power sources 4A-4C, secondary currents flows to resistors R1 from current transformers CT1-CT3 through lead wires 15, 15. The voltages at both terminals of the resistors R1 are applied to Pockels elements 13A-13C and, when a power source 26 is turned ON, a light emitting element 22 is operated to emit optical power which is, in turn, transmitted and applied to the element 13A through a polarizing picture preserving optical fiber cable 17 and a light transmitting body 12 by the Pockels effect of said element 13A and the element 13 receives phase modulation corresponding to the change in voltage. The elements 13B, 13C also receive phase modulation in the same way corresponding to the change in the voltages applied to said elements. The optical power subjected to phase modulation receives intensity modulation by an analyser 23 through the light transmitting body 12 and a cable 20 and is succeedingly converted to an electric signal by a light receiving element 24. This signal is outputted from output terminals 28, 28 through an amplifier 27. Only by connecting a predetermined meter to the terminals 28, 28, a zero phase current can be detected and measured.</p> |
