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Partial Tension – Northeast, USA

Background

A longtime DMC Power customer in the Northeast United States was conducting their annual helicopter fly-over of 115kV transmission lines and noticed during the thermal scans that a competitor's loop splice on the lower left jumper wire (between the two dead end structure shoes) was running hot and needed replacing

Problem

A fast solution was needed for both product delivery and installation.

  1. The 115kV line runs parallel to the Right-of-Way of Commuter Railroad tracks and next to Interstate I-95. Since no modifications can be made on or near the tracks during regularly scheduled commuter service, installation was required to take place outside of the morning rush hour.
  2. Circuit outages are difficult enough in the congested Northeast. Disabling the railroad's main commuter line for maintenance longer than the allotted one hour outage window was not an option. An additional complication to the installation was that the operation of the main communication trunk line was integrated into the 115kV OPGW static line. This required the Utility & Railroad protocols to provide redundancy box grounding around the area where the work was being performed.
  3. A splice failure would put thousands in the New England region out of power.

Solution

The contracting company was very familiar with DMC Power products and recommended us for our fast turnaround on made-to-order fittings and the engineering & field support that would be provided throughout this time sensitive project.

A conference call was held on February 22nd between the Utility Engineering Department and DMC Power's Engineering Manager, Full Tension Product Manager, Area General Manager and Territory Manager to understand the scope and requirements of the project.  Three remedial options were discussed:

  1. Cut out the existing jumper conductor and failed splice and replace with two DMC Power loop splices. This option proved concerning given the short length of tail conductor from the bolted shoe and the unknown “heat affected” zone of the conductor
  2. Apply two new DMC Tee Taps on the main line and shunt the existing jumper with new 1590 ACSR conductor and two new DMC Power terminals.
  3. Design a new Reduced Length Splice for the Partial Tension application.

The purchase order was received on February 28th. With a very compressed timeline we had to start work immediately.

DMC Power is an ISO certified company with strict protocols in place when creating an entirely new connector. This process usually requires 6-8 weeks for designing, testing and manufacturing a new part. From initial design to manufacturing, this entire project was compressed into 2-3 days without compromising quality standards DMC Power has in place.

(2) DC92-225-76

Split Run Tee
Cable to Pad

(2) DC94-225-76 -00

Partial Tension Terminal
15° Each (30° Total)

 (2) DC91-225-76-S1

Partial Tension Splice
Reduced Length

Installation

Connectors shipped from our Los Angeles facility on Friday, March 3rd, and were delivered on-site Monday, March 6th, with installation planned the following day.

The DMC Power Swage System is designed to connect in ALL weather conditions. However, due to rain, sleet, snow and dangerous on/off winds, the decision was made to push the installation to Thursday, March 9th.

DMC Power arrived on-site that Thursday morning with Swage Tooling in hand. A 30-minute training/refresher was performed with the Construction Crew (3 Linemen and 1 Foreman), Utility Managers (Engineering and Construction) and representatives from the Railroad Agency (including Engineering, Construction and Project Managers).

After the failed splice was cut out during the outage it was determined the Deadend tail conductor was long enough and the existing jumper was replaced using (2) modified DMC Power loop splices.

Results

The loop splice solution worked perfectly and installation was flawless. The loop splices were Swaged, redundant box grounding removed, construction personnel retracted to the ground and the line was energized faster than the 1 hour maximum allotted time with no disruptions to train or Interstate traffic. All parties were extremely pleased with the efficiency, safety and reliability of the DMC Power Swage System.

"I want to thank you and your group for the continuous support.  Your involvement with this particular hotspot repair made it all possible.  Thank you and I look forward to working with your company on future transmission maintenance projects"  - System Maintenance Lead Engineer

 

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