IMPLOSIVE CONNECTORS For Tactical Upgrades of Transmission Lines

Part of the challenge in increasing the ampacity of these circuits was to rebuild them so that they could be operated at higher temperatures while maintaining safe electrical clearances.

The summer of 2005/2006 has seen some of the largest scale transmission line maintenance works take place on Transpower NZ Ltd’s 220kV asset. Responding to the need to increase the capacity of existing transmission lines, Transpower awarded a joint venture between Electrix Ltd. and Transfield Services Ltd. with the job of completing tactical upgrades of high voltage circuits all over the South Island of New Zealand.

TACTICAL UPGRADES
Originally built in Goat (400mm2) and Zebra (485mm2) ACSR in the 1950’s and 1960’s, part of the challenge in increasing the ampacity of these circuits was to rebuild them so that they could be operated at higher temperatures while maintaining safe electrical clearances.

Backed by Transfield and Electrix, the technology chosen to complete the tactical upgrades was implosive connectors over the traditional compression connectors. Implosive connectors offered a number of advantages for the project including:
• Fastest speed of install : minimised outage duration
• Increased asset uptime/availability for system operations
• No conductor cleaning required
• Consistent high quality installation – every fitting

Use of implosive connectors was supported by Electropar with testing completed in Electropar’s IANZ accredited (IANZ in NZ is similar to NATA in Australia) high current test laboratory. Over an almost 12 month period, the Goat and Zebra implosive fittings (Midspans, Deadends, Repair Midspans and Repair Deadends) were subjected to 500 cycle tests with a temperature rise of 110C in accordance with IEC 61284. This provided a current rating temperature for the conductor of 90C.

Electropar has completed this same test regime for compression fittings (Midspans, Deadends, Repair Midspans and Repair Deadends) for Goat and Zebra conductors, and will shortly begin similar testing for Venus (61/3.75 AAC) conductor compression fittings.

At the same time, damaged aluminium strands of Zebra ACSR conductors were repaired utilising implosive repair sleeves applied from a helicopter. ABB in New Zealand developed the procedure for applying the repair sleeves with the 220kV circuits alive, the damage having occurred under twin conductor spacer clamps. This repair work was a real success both in terms of speed of install and install quality.

Shortly Electropar will undertake electrical/mechanical testing to more accurately quantify the effect the repair sleeve has on restoring conductor ampacity and tensile strength.