| 摘要 |
The invention relates to a water monitoring system and a water monitoring method for a high voltage cable (CA) including a conductor (4) and a screen (2) surrounding the conductor. At least a first water sensing wire (11) extends in the screen (2) between the cable beginning (CB) and the cable end (CE) and at least a second wire (12) is connected with the first wire (11) at the cable end to form a loop. A first switching unit (3) is provided between the cable beginning (CB) and the measurement circuit (MC). A control unit (CU) controls the first switching unit (3) over a first predetermined time interval into a first switching state in which the water sensing wire (11) and the second wire (12) are connected to the screen potential. In a following second predetermined time interval the control unit (CU) controls the first switching unit (3) into a second switching state in which the water sensing wire (11) and the second wire (12) are disconnected from the screen potential. The measurement circuit (MC) performs a water intrusion measurement by performing resistance or isolation measurements, i.e. voltage drop measurements, in the second predetermined time interval. Preferably, the first predetermined time interval is much longer, i.e. 30 to 60 minutes, than the second time interval, e.g. 1 to 2 minutes. |
