Measuring Current on Underground Cables

SensorNote 110: Operation notes for safety and productivity

Is the SensorLink® Ampstik® able to measure a shielded cable?

Yes, the SensorLink Ampstik can measure the sum of the currents on a shielded cable. When there is current on both the conductor and the shield, the total depends on the direction of current flow of both the conductor and the shield. In the below example, with 100 A load on the conductor, and 3 A load on the concentric neutral, the total Amps measured is 97 Amps.
Note: Current on the concentric is typically generated by unbalanced load.

Underground Cable


Where is the best place to accurately measure an underground cable?

On an underground system, the best place to measure current is above where the concentric neutral is tied to ground on the elbow.

ElbowAmpstik on Elbow



Does the Bleed Wire have an influence on the measurement?

There is very little influence onto the bleed wire and has little influence on the measurement. The Bleed Wire is in place to discharge capacitive voltage from the semi-con on the elbow. The elbow would be in failure mode with any significant current on this wire.

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