A major utility had installed a large solar farm in upstate New York. To receive 2019 tax credits for the renewables project, the utility needed to document that the solar farm could generate power. The power company had not yet extended the grid to connect to the installation, however.

On Thursday, December 19, a utility representative called Sunbelt Rentals and explained the need to perform a proof of concept and secure the tax credits. With only 10 days before the end of 2019—and Christmas less than a week away—timing was critical. 

Weather and holidays complicate logistics

The customer gave verbal approval for the project at 9 p.m. on Friday, December 20. The Sunbelt Rentals team worked through the weekend to source equipment and determine freight costs for travel through holiday traffic. All load bank equipment had to be on site and set up to begin testing by Thursday, December 26.

On Monday morning, haulers made several stops to pick up the load bank, transformer, and cabling, and then headed to the site for delivery. On the day after Christmas, drivers loaded the generators and, along with a technician, headed for the solar farm at 3 a.m. Wes Frink flew out of Indianapolis an hour later.

The team converged on the site at 10 a.m. Instead of the deep snow they expected, they found 8 to 10 inches of liquefied mud. Given the mobility issues, offloading and setup took 3 to 4 hours longer than usual. But the team had all equipment in place and tested by Thursday evening. 

Electricians made the final connections to high voltage lines on Friday, but the inverter company technician was delayed a day. The utility was finally ready to test the solar farm on Saturday.

Load bank helps verify power generation and anti-islanding

Utilities use load banks to prove a solar installation can generate power and also to verify the equipment works before final grid connection. The load bank absorbs power from the solar farm to prevent generator shutdown or wet stacking. 

For this project, the team connected two parallelable Doosan 500-kW generators to a 3.3-MW load bank as a common bus. They then connected the load bank to a 1500-kVA 34.9-kV transformer to generate power and simulate the grid. This setup fed power to two 2750-kVA 34.9-kV transformers and the solar farm inverters, powering their controls to start operation. 

The team also simulated anti-islanding using the load bank. The anti-islanding test is an IEEE standard. The test verifies that a renewable project can isolate itself from the grid to ensure worker safety if the grid fails. The test used both 500-kW generators to fire up the three transformers at once. Despite the substantial inrush current, Frink chose the configuration to let the utility move seamlessly from the first to the second test. This setup saved the customer about a day of test time.

Sunbelt Rentals team outpaces two others

Although the utility’s primary goal was to secure tax credits, the test also served as a proving ground for vendors. The utility representative noted that not only did Sunbelt Rentals equipment look the best, but the team finished testing first despite being the last called. Instead of days spent on-site for testing, the representative needed only 45 minutes.

Price always matters when deciding which rental company to hire, but the utility appreciated having a turnkey solution provided by a team that understands their needs. “What I’m most proud of is the teamwork,” said Frink. “We were able to pull this all together in just days and get the right gear to the customer for the test.” 

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