Isolating cable faults, part 1.

Question 1

how does a fault indicator cable work?

Answer 1

when abnormally high current flows through it, it will alarm.

Answer 2

when faulted cable has been found, it should be isolated and tag at both ends.

Question 3

explain how you can isolate a faulted cable ?

Answer 3

lift the load-break elbows on each end of the cable from the feed-through bushings on the transformers, and then place the elbows in standoffs on the transformers

Question 4

when using a phasing sticks to test a isolated cable for fault. what does high voltage reading means?

Answer 4

high voltage reading means that the current is passing through the phasing sticks and the cable
to ground through a fault somewhere in that cable. (cable has a faulted)

Question 5

when using a phasing sticks to test a isolated cable for fault. what does zero or very low voltage reading means?

Answer 5

it means that there is no short to ground on that cable and the cable probably all right.

Question 6

True or false. Cable fault indicators eliminate the need for isolating sections of cable.

Answer 6

False

Question 7

list three types of cable fault indicators used on URD systems.

Answer 7

1. relay and flag arrangement
2. indicating light
3. audible tone

Question 8

Circle the correct answer.
When one section of cable is isolated at a time starting from the normally open point, the first step is to

a. Replace the blown transformer primary fuse on the isolated side of the loop

b. Place the end of the first section of cable in a double feed- through standoff at the second transformer from the normally
open point

C. Lift the load-break elbow for the first section of cable at the first transformer on the isolated side of the loop and place it on a standoff

d. Take a voltage reading between the open bushing on the transformer and the first section of cable using a pair of phasing sticks and the appropriate adapters

Answer 8

C. Lift the load-break elbow for the first section of cable at the first transformer on the isolated side of the loop and place it on a standoff

Question 9

Circle the correct answer.
If the voltage reading taken on a section of cable is ___________, voltage is passing through the phasing sticks and the cable to ground through a fault somewhere in that section of cable.

a. Approximately equal to phase-to-ground voltage
b. very low
c. Zero

Answer 9

a. Approximately equal to phase-to-ground voltage

Question 10

True or False. One of the drawbacks of troubleshooting one section of cable at a time starting at the normally open point is that a problem with the phasing sticks could result in the entire URD loop being out
of service.

Answer 10

True

Question 11

Circle the correct answer.
When one section of cable is isolated at a time starting at the blown
riser pole fuse, the first section of cable that is tested is isolated from
the (normally open transformer/ first transformer in the loop).

Answer 11

first transformer in the loop