This document provides an example calculation for determining distance to fault using an 860 DSPi device. The distance to fault formula uses the velocity of propagation and difference in frequency between two markers on the standing wave pattern. In the example, with a velocity of 0.84 and a frequency difference of 35.97, the calculated distance to fault is 11 feet. A note indicates the markers need to be placed on a full cycle of the standing wave for an accurate measurement.

1. Application Note
860 DSPi Distance to Fault
Distance to Fault Formula = (VP * 492)/Delta in Frequency of Marker B – Marker A
VP = Velocity of Propagation
VP = 0.84 (This is set by the user for the cable under test)
∆ B-A = 35.97
Distance to Fault = (0.84 * 492)/35.97 = 11 Feet
Note: The markers need to be place on one full cycle of the standing wave to get a correct
distance to fault measurement.
For Additional Help Contact
Trilithic Applications Engineering 860 DSPi Distance to Fault
1-800-344-2412 or 317-895-3600 P/N 0010275005 – Rev 5/07
support@trilithic.com or 1 of 1
www.trilithic.com
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