Renewable collector cable buyers in New York

34.5 kV, and why the collector is not a distribution feeder

The standard collector voltage in the United States is 34.5 kV, and the cable is 35 kV class: 420 mil XLPE insulation at the 133% level, single conductor, usually aluminum, with a copper tape shield or a concentric neutral. The reason for the voltage is reach. A collector feeder may run a mile or more between the furthest inverter and the substation, and at 34.5 kV the current for a given power is low enough that the cable can be a practical size and the voltage drop stays acceptable.

Older wind projects in particular were built with 15 kV collectors, using 220 mil cable and smaller conductors. That is one reason repowering is such a productive source of this material: a project that replaces its turbines and its inverters often upsizes the collector from 15 kV to 34.5 kV at the same time, and the old feeder cable comes out. Solar projects have also been built at 24.9 kV and 13.8 kV where the utility's practice or the project size pointed that way.

Sizing is driven by voltage drop and thermal limits together. Long feeders are limited by drop, short ones by ampacity, and both are affected by how the cables are buried: three single conductors in trefoil run cooler than three laid flat and spaced, and a duct bank runs hotter than direct burial in moist soil. That is why collector cable sizes vary so widely between projects of similar capacity.

Direct burial, conduit, and what survives

Most collector feeder is direct-buried: trench, sand or a flowable thermal backfill, cable, more backfill, warning tape and a tracer wire, with cover depth set by the project's design and the local code. The thermal properties of the backfill are part of the electrical design, not an afterthought, because they set the ampacity the cable can actually carry.

Conduit is used where the route crosses something it cannot disturb — a road, a railway, a wetland, an existing pipeline — and at transitions into equipment. Those crossings are often installed by horizontal directional drilling in HDPE duct, sometimes several hundred feet in a single bore, and the cable is pulled in afterwards.

That difference decides what can ever be recovered. Cable in conduit can, in principle, be pulled out and reused if the route is straight and the jacket is sound, though a long pull through a drilled bore rarely comes out undamaged. Direct-buried cable is cut out in short sections when a project is decommissioned, and it is usually recovery material rather than reusable cable. The valuable collector cable in the surplus stream is overwhelmingly the cable that never went in the ground.

Close-out and repowering: the two surplus patterns

At construction close-out, the material is over-ordering. Collector cable is bought against a calculated footage with an allowance for pulls, transitions and damage, and what is left goes back to the contractor's yard or stays on site. Reels are usually partial rather than full, the cut-offs are the tails from home runs and transitions, and there is normally a reserve of cable the owner keeps for maintenance. That reserve is the piece sellers most often forget to mention and buyers most often want.

Removal only happens after the feeder is de-energised at the collector substation, isolated, proved dead and released under the site's own lockout procedure. At repowering, the material is removal. Turbines are replaced with larger machines, inverters are replaced with higher-rated units, and the collector is reconfigured, which produces both new-build surplus and the old cable. The old cable is the harder lot: direct-buried, cut out in short lengths, often with a jacket that has spent twenty years in wet soil, and frequently mixed with the old connectors and terminations.

New York's project pipeline feeds both patterns. Utility-scale solar has concentrated in the upstate counties where land is available and interconnection exists, wind in the North Country and the western counties, and battery storage closer to the downstate load. Siting runs through the state's renewable siting process and interconnection through the grid operator, and both take years — which means the cable for a project is often ordered long before the close-out lot exists.

• Which project and which stage: new build, close-out, or repowering
• Reel-by-reel footage rather than a total, since a part reel and a full reel price differently
• Conductor size and material, and whether the shield is tape or concentric
• For removed cable: whether it was direct-buried or in conduit, and how it was cut out
• Whether the O&M spare is included, because it is usually the best cable on the site