Gloomy Muskrat update reveals transmission testing hampered by vibrating condensers

All or portions of the three synchronous condensers at the Soldiers Pond switchyard can be seen in this N.L. Hydro/Nalcor photo. (Nalcor Energy - image credit)
All or portions of the three synchronous condensers at the Soldiers Pond switchyard can be seen in this N.L. Hydro/Nalcor photo. (Nalcor Energy - image credit)

Efforts to commission the high-voltage power line from Muskrat Falls to Newfoundland's Avalon Peninsula have again run into problems, but this time the bug-prone computer software needed to operate it does not appear to be the primary reason.

And it could mean a delay in a critical test planned for later this month.

In its latest update to the Public Utilities Board, N.L. Hydro revealed another long-standing concern — the reliability and design of three large synchronous condensers at the sprawling switchyard at Soldiers Pond, outside St. Johns — has re-emerged as a potential roadblock to final commissioning of the 1,100-kilometre Labrador-Island Link, known as the LIL.

The switchyard is where high-voltage, direct-current power from Labrador — up to 900 megawatts — is converted to alternating current electricity and then integrated into the island's power grid

The synchronous condensers at Soldiers Pond help maintain system stability and keep voltages at specified levels, and at least two of the three condensers must be available when the power line is operating at peak capacity.

Since their installation roughly four years ago, the condensers have been plagued by jamming and vibration problems.

And the latest? The contractor, GE Power, has been unable to resolve an issue with the bearing on condenser No. 1 and has informed Hydro that a "design review" is needed. It's not clear whether that means a major overhaul or outright replacement of the unit is needed.

Units No. 2 and 3 also experienced "forced outages due to vibration" on two occasions last month, unrelated to the bearing issue with Unit 1. The outages occurred during testing, and the condensers were brought back online within a few hours.

As a consequence, Hydro has restricted the LIL to a maximum of 315 megawatts until it receives documentation from GE confirming that the condenser problems have been resolved.

That could be a problem. The LIL was tested up to 475 megawatts last month, and testing at power levels greater than 675 megawatts is scheduled for the week of Nov. 21.

But in a phone interview Friday afternoon, Hydro CEO Jennifer Williams expressed confidence the high-power test will proceed as planned, and the investigation into the root cause of the condenser trips is "close to being concluded."

"These are assets in service not that long, and you need a period of time for the assets to experience all kinds of system operating conditions, and then you tweak your various protection settings to what it needs to be for the longer term," Williams said of the condensers.

When asked about the design review for condenser No. 1, Williams said it's too early to say how the situation will be resolved.

When asked if the entire multi-million-dollar unit will have to be replaced, Williams said, "We're not getting into that at this point because we have to go through all of the aspects of the engineering and the various options that are available."

The LIL will be considered commissioned, meanwhile, once these high-power tests tests are successfully completed.

Monthly meetings between the CEOs of Hydro and GE Power are ongoing "to ensure this issue is resolved to satisfaction," according to the update.

The LIL is the transmission component of the Lower Churchill Project, which also includes the 824-megawatt hydroelectric generating station at Muskrat Falls in central Labrador. The power station was commissioned last year, although one of the four generating units is currently offline for planned maintenance.

The project is massively over budget, at nearly $13.4 billion, and is years behind schedule.

GE has been struggling for years to perfect the specialized control and protection software needed to safely operate the LIL, and trial operations that commenced Oct. 11 have revealed some encouraging results. There were no LIL-related customer outages in October, for example.

"The period will be considered successful after 30 consecutive days of operation without a trip attributed to the HVdc2 system," says the update to the utility regulator.

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