Determining And Measuring Vp Values - AEMC Instruments CA7024 Manual De Instrucciones

4.9

Determining and Measuring Vp Values

Velocity of Propagation (Vp) values are characteristic of each cable type
and brand.
The Vp is used to measure the length of a cable and to measure a fault
location. The more accurate the Vp, the more accurate the measurement
result will be.
The cable manufacturer may list the Vp on their specification sheet or may
be able to provide it when asked. Sometimes this value is not readily avail-
able, or the user may wish to determine it specifically to compensate for
cable batch variations or for special cable applications.
This is quite easy:
1. Take a cable sample of exact length increments (ft or m) longer than
60ft (20m).
2. Measure the exact length of the cable using a tape measure.
3. Connect one end of the cable to the Fault Mapper (see § 4.11). Leave
the end unterminated and make sure the wires do not short to each
other.
4. Measure the length and adjust the Vp until the exact length is displayed.
5. When the exact length is displayed, Vp is established.
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Fault Mapper Model CA7024