| 摘要 |
PURPOSE:To make the sensitivity-setting work of a ground relay safe and laborsaving by setting the ratio of a distribution line length to an overall distribution line length for each plurality of distribution lines. CONSTITUTION:A ground discrimination circuit 11 detects occurring of a ground in a distribution line and a ground-phase discrimination circuit 12 discriminates a ground phase x. A rho-setting circuit 16 sets the ratio rhoi of a distribution line length to an overall distribution line length. A comparison circuit 14 computes a value containing the zero-phase current I0 of the distribution line, the phase voltage Vx of the ground phase x and the set value rhoi:(1-rhoi)¦Vx¦/¦3I0¦ and compares the value with a ground reference resistance Rg0. Then, when the computed value is less than the ground reference resistance Rg0 as the result of comparison, a ground resistance discrimination circuit 13 discriminates occurring of the ground in the distribution line by the fault-point resistance falling below the ground reference resistance Rg0. |
