| 摘要 |
PURPOSE: To prevent an accident such as the fusion of a wiring due to an excessive current by estimating the value of a current flowing through the wiring after connected before electrically interconnecting the wirings inside of a building. CONSTITUTION: Before an earthing bus 5 is directly connected to the communication ground 10 of a building by terminals (a), (b), a connection resistance 6 of a resistance value Rm1 through which an excessive current does not flow and an ammeter 7 are connected between the terminals (a), (b) and a current Im1 flowing through the ammeter 7 and a current value Ip1 at the point (p) of a ground wire 8 having the possibility of fusion are measured and recorded. Next, after the resistance value of the connection resistance 6 connected between the terminals (a), (b) is changed to Rm2 the current value Im2 of the connection resistance 6 and the current value Ip2 at the point (p) of the ground wire 8 are once again measured and recorded. Next, the current value Ip0 flowing through the ground wire 8 when the terminals (a), (b) are directly connected to each other is estimated by using an equation: Ip0 =(Im2 Rm2 Ip1 -Im1 Rm1 Ip2 )/(Im2 Rm2 - Im1 Rm1 ) on the basis of the resistance value Rm1 , Rm2 and the measured current value Ip1 , Im1 , Ip2 , Im2 . |
