upgrade 138kv underground circuit from polk to garrott substations ercot rpg meeting january 13,...
TRANSCRIPT
Upgrade 138kV Underground Circuit From Polk to Garrott Substations
ERCOT RPG Meeting
January 13, 2012
1
Scope
• Upgrade capacity from 247 MVA to 480 MVA
• Parallel existing circuit (no new circuit)
• Follow existing route
• Loop into Midtown substation
• Utilize DTS technology
• Install fiber optic circuit protection
2
Circuit Route
• Downtown Houston
• 12,300 feet
• New parallel cable follows same route
3
Midtown
Challenges
• Downtown city streets
• Parallel utilities
• Crossing utilities
• METRO light rail
• NBA Season
• Paving ordinance
• Permits
4
Project Engineering
• Utilize current cable technology
• XLPE insulated– Ready domestic supply– Available craftsmen
• CNP had successful installations with these materials on other projects
• 20’ to 24’ depth
• Final permits recv’d 11/2010
5
Construction Plan
• 6,000 ft. horizontal directional drill
• 6,300 ft. guided bore 400 – 500 ft. sections
• Broke ground 12/2010
6
Planned Grout Tests
• Two 80 ft. mockups (rehearsal)
• One 500 ft. test
• One 460 ft. re-test
• Goal: prove no voids
7
Test Grout Results
• Good grout suspension
• Successful grouting of 80 ft. mockups
• Large voids in 500 ft. test section
• Revised spacer design
• 460 ft. retest successful
8
Project Delay
• Inspection revealed unacceptable ductbank segments
– Grout intrusion• Must resolve for cable installation
• Conduit source plant changed
• Schedule delay
• Installed in new section
– More grout intrusion
• Reviewed
– Process
– Material
• Schedule delay
9
Project Continuation
• New conduit supplier
• Contractor required to rebuild or repair bad segments– Rebuild
• Push out whole segments
• Install new casing and conduits
• Establish a procedure
– Repair• Excavate/shore to bad area
• Point repair
• Successful grouted sections
• Projected energization date: 4/26/2012
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