DKI-117 – Insulation fault detection sensor
DKI-117 sensor is used with cable locating receiver (AP-019 or AP027) for location of insulation damage in power cables, gas and heat pipes. Above all, operation of this sensor is based on the principle of voltage difference detection. Therefore, DKI sensor consists of two isolated from each other electrodes connected to the preamp in handle.
How does it work DKI-117?
Firstly, Protective insulation of cables and pipes is used for avoiding metal to earth contact. Secondly, If this insulation is damaged, insulated conductor is shortened to the ground.
Moreover, when tracing transmitter is connected to the utility and to the ground, alternating current leaks in the spot of insulation damage to the ground and returns to the transmitter. Meanwhile, it creates step potential on ground surface. Search of defects can be performed on all supported frequencies, in active or passive mode.
In conclusion, DKI evaluates voltage difference in two points on ground surface. In damage spot the difference value will be as big as the damage of insulation.
DKI-117 Method of cable fault location with DKI Sensor
Firstly, when locating the damage in MAX mode one contact electrode of DKI should be placed above the utility and the second should be perpendicular to utility axis. Secondly, each electrode should be fully stuck into the ground to ensure good contact. Moreover, the gap between to surveyed spots should be not less than 1 meter.
Subsequently, the signal will be displayed at your receiver screen. In other words, it will slowly rise while operator is moving to the damaged spot. Therefore, in the place of damage – the signal will be maximal. In other words, if operator passes the spot of damage, the signal level will decrease. See pic. 1.
In conclusion, MAX method allows to locate the presence of the damage, however it is not too precise in localization of the spot.
While locating the insulation damage in MIN mode, contact electrodes of DKI should be placed straight above in the direction of the utility. While operator is moving to the damage, the signal will slightly rise then significantly decrease to the minimum. Then it will rise again while operator is passing the damage. The spot with minimal signal indicates the damage. See pic. 2.
DKI-117 sensors requires 1 operator, DKI is more effective and sensitive instrument in damage location than DODK sensor.