Condition assessment on critical 22 kV high-voltage cables in a Chemical plant
During an Online PD survey, critical PD activity was revealed at one out of 25 outgoing cable circuits. The relevant circuit consisted of two parallel-connected cables with associated terminations, as well as transition joints 1.5 meters from the terminations.
Online PD measurements (50 Hz):
A few weeks after the Online test, we did a Offline cable diagnosis. This test confirmed the results from the Online test. During normal operation, critical PD activity was present at phase L1 and L2 at one of the two cable sets connected in parallel. The test also revealed critical PD activity at phase L3 at the other cable set at 20% overvoltage.
On the basis of the inspection, it was recommended to change terminations / joints at phase L1 and L2 at cable 1 and termination/joint at phase L3 at cable 2
Offline cable diagnosis:
Cable 1 with faults on phase L1 and L2 at operating voltage:
Cable 2 with fault on phase L3 in case of overvoltage: