| 摘要 |
<p>PROBLEM TO BE SOLVED: To allow a leakage current flowing on a three-phase four-wire distribution line to be monitored by detecting a leak current by a resistance I0r.SOLUTION: Leakage current detection means 12 detects a leakage current flowing on a three-phase four-wire measured conductor line which Y-connects three phases (R phase, S phase, and T phase) and grounds a neutral point so as to pull out a ground line. Reference voltage detection means 13 detects a voltage generated between any two phases of the measured conductor line as a reference voltage. The leakage current by a resistance calculation means 15 calculates a leakage current by a resistance Ir due to a ground insulation resistance based on a phase differenceθbetween the reference voltage and the leakage current and an effective value Iin accordance with the case where the phase differenceθis within the following cases (A) to (C) : (A)π/6≤θ≤5π/6:Ir=I*sinθ/cos(π/3), (B) 5π/6≤θ≤3π/2:Ir=I*sin(θ-2π/3)/cos(π/3), and (C) 3π/2≤θ≤13π/6:Ir=I*sin(θ-4π/3)/cos(π/3).</p> |
