CONDITION BASE MAINTENANCE (CBM)

ACTIVITY ON 12/4/10

Purpose of CBM are :

> to monitor health of cable before any failure occur

> as a precaution before cable get damage

There are two types of Advance Testing :
(1) Dielectric Spectroscopy

(2) Partial Discharge

Abbreviation
* PILC - Paper Insulated Lead Cable

XLPE - Crosslinked Polyethylene

TYPE 1 - Dielectric Spectroscopy

DS testing is acttualy to check the moisture of insulation.

- the result taken will be compare with the references table provided (*only PILC had the references table, XLPE has no limit)

- if the data didn't match with the table, further action are required base on the recommendation

- if the moisture is high , its easy for water tree to happen

- DS usually used for PILC cable. However it also can be apply to XLPE cable but it needs extra High Voltage set in order to check the XLPE moisture.

TYPE 2 : Partial Discharge

Types :

- on-line PD testing

- on-PD monitoring

- off-line PD testing

PD Theory :

- Electric discharges which do not bridge electrode are called partial discharge. between the electrodes a sound dielectric is present in the form of solid, liquid or gaseous insulator.

- PD belongs to a far greater group of gas discharges. In all these discharges gas molecule are ionized by impact of electrons.

- Classification : corona discharge, surface discharge, and internal discharge.

PD Diagnostic (in general)

Advantages :

- Non-destructive test

- Technology which can defect and locate high impedances defects such as void, cuts, elctrical trees and tracking (symptoms for Water Tree)

- On-line application possible

- Effective at locating defects in mixed dielectric systems

Limitations :

- limited to cables with a continuous neutral shield

- requires a trained analyst to interpret measurements

- cannot detect or locate conduction type defects

- loses accuracy in branched network applications

two ways to handle PD testing :

(1) VLF - Very low frequency

(2) OWTS - Oscillating Wave Testing System (default by TNBR)


i will share with u guys bout the PD Mapping (site measurement) later