Partial Discharge Mapping
This world-first technology is capable of mapping High Voltage cables while in normal service to provide the asset owner with the location and magnitude of any PD sites within the length of the cable.
This provides an early warning of developing cable and equipment insulation faults enabling repairs to be planned and organised before a fault occurs with its associated inconvenience and disruption to customers and Network Managers.
Why Carry Out On-line PD Testing on cables?
There are three main reasons for carrying out the On-line PD Testing, as follows:
- To get baseline readings for future condition assessment of cable condition.
- To provide an insulation quality check on the cable termination and cable condition as part of the routine maintenance checks.
- To locate any PD activity along the length of the cable as a pre-cursor to repair and / or replacement.
Suitable applications for cable mapping
Mining, port loading facilities, and power generation (wind farms / hydro) stations, substations and distribution networks, ski fields, hospitals, dairy and meat works, telecommunication centres, water and sewage treatment plants
Case History - 1
This latest technology was used at a ‘SU Zone Substation’ where a full on-line Partial Discharge inspection was completed on 22kV cables, Surge arrestors, and 22kV switchgear.
The comprehensive 42-page report provided to POWERCOR within two days of the completion of this survey furnished.
- Quantitative information to help prioritise maintenance and capital input.
- Quantified the risk of failures for critical feeder cables.
- Enabled repairs to be planned and organised before faults occur by identifying problems in advance.
- Allowed the Powerco maintenance team to focus on higher priority tasks, instead of maintaining assets that may not require attention.
Case History – 2
The benefits of carrying out On Line Partial Discharge Mapping were highlighted in a recent site survey with Nelson Electricity (NZ), when a 33kV XLPE Tie cable was found to have high PD (92 - 135mv). By carrying out accurate measurements, the source of PD was located and repairs action.
Case History – 3
On-line Partial Discharge Mapping was carried out was for Dunedin Electricity Ltd. Prior to re-configuring a 47 year old paper-lead standby sub transmission circuit, confirmation was required that it could handle increased loading. By carrying out an on-line survey, DELTA were able to determine that no PD was present in this circuit, which meant an old asset could continue to be utilised and handle the load. This has resulted in the deferment of $1.1million worth of planned capital works.
