Wreck Cove Hydroelectric System

Under NERC, Nove Scotia Power must maintain multiple black start pathways to re-start the grid should a black-out ever occur. Wreck Cove is one of the two pathways Nova Scotia Power uses to meet this NERC requirement.[6]

Nova Scotia Power must maintain sufficient capacity to serve its peak load as well as additional capacity for the planning reserve margin (PRM). The PRM acts as a resource to respond to a contingency to ensure customer load can be served in the event unexpected generation restrictions or supply requirements arise. For example, the PRM capacity ensures adequate generation in the event that one or more generation resources are unavailable or cannot run at full capacity at the time of system peak. Planning reserves also account for uncertainties in demand forecasting and resource availability. The Wreck Cove system contributes approximately 8 percent towards NS Power’s total required capacity in 2020, assuming a PRM of 20 percent.[6]

NERC/NPCC requires electric utilities to have their largest single energy production source covered by an alternative source in reserve capacity. Currently, NS Power’s largest single unit is Point Aconi Generating Station which produces 168 MW of operating capacity. Wreck Cove Units 1 and 2 have an accredited capability of 106 MW each unit (212 MW total), making this facility an important provider of this service. As such, the reliable operation of the Wreck Cove Generating Station provides Nova Scotia Power’s ability to meet this requirement. NPCC also requires that operating reserve capacity be available and on the grid within 10 minutes. If Wreck Cove’s Units 1 and 2 are off-line, they can be brought onto the grid and reach full capacity within the 10-minute requirement.[6]

Wreck Cove assists with providing tie-line regulation. Nova Scotia Power is required to have reserve capacity available for changes in demand across the tie-line to New Brunswick. Because Wreck Cove is capable of changing its output at the rate of 20 MW/min, it is more effective in responding to fluctuations in Nova Scotia system load and wind generation than slower acting thermal generation sources, which can be moved at a rate of 0.5 MW to 2 MW per minute.[6]

Wreck Cove 1 has been utilized in recent years as a means of balancing energy generation throughout the cycles associated with wind generation. Nova Scotia Power’s hydroelectric generation provides load/wind following services, meaning that the hydroelectric generation is dispatchable and can be used to mitigate the impacts resulting from the high variability of wind generation resources and associated forecasting variations. Although wind following was not the original intent for the use of Wreck Cove, having the ability to utilize Wreck Cove in this way has supported the development and integration of wind generation on the grid. This service is related to the Tie-Line Regulation discussed above, but over a longer time frame. The flexibility of Wreck Cove’s load response is also critical to managing periods of short term, large scale load changes (pickup and drop-off) from industrial customers on the grid.[6]

Wreck Cove provides critical peak load shaving capacity for the short periods of high load that occur daily, typically during morning and evening peak hours. Given Wreck Cove can be brought on-line quickly for these periods of high load ramping, thermal generation resources which cannot be cycled off-and-on frequently can be more economically dispatched.[6]

Wreck Cove is a source of 212 MW of stored power for Nova Scotia Power to use when needed. It can operate at maximum power for 4–6 hours depending on conditions, at which time it needs to allow water from farther upstream in the watershed to make its way to Surge Lake.[6]

Nova Scotia Power’s 33 hydro plants/50 hydro units provide 180 MVar of dynamic reactive power to the system. The Nova Scotia Power System Operator controls generators to absorb or produce reactive power to control system voltage. Wreck Cove is located at the eastern end of the transmission grid and therefore its ability to support load is less important than generation closer to the load centre; however, due to its relative size, its dynamic reactive power contributes to stabilizing the grid following disturbances.[6]

Wreck Cove, like all hydro and thermal generators, is equipped with speed governors which maintain the scheduled grid frequency of 60 Hz. It provides a significant contribution to system inertia, which stabilizes the grid frequency during disturbances.[6]

Hydro generation contributes to system inertia, which allows the system to ride through fault conditions, and short circuit strength, which provides the high fault current levels needed to activate system protection devices (inverter-based wind, tidal and solar do not materially contribute to this).[6]

The project land were owned by the Province, with the exception of the 26 square kilometres (10 sq mi) Chéticamp Lake area which was owned by the federal government and formed part of the Cape Breton Highlands National Park. At the request of the Province, the latter was removed from the Park in 1958 when planning for the project first began. Since that time these lands were managed by the Department of Indian and Northern Affairs as federal crown lands but were not been subject to the National Parks Act.

The Nova Scotia Power Corporation (NSPC) recommenced planning for the project in 1974. At that time the Minister of Indian and Northern Affairs agreed in principle to an exchange of the Chéticamp Lake lands for those of an equivalent natural value elsewhere in the Province, on the condition that there should be no adverse effects from the project or the National Park. In late 1974 a private consultant prepared a preliminary environmental evaluation of the project's probable effects. Following a review of this evaluation a resolution was passed by the Nova Scotia Legislature in January 1975 indicating that the project was to proceed, and "that a phased environmental assessment be undertaken to minimize potential adverse effects". In March 1975, Nova Scotia Minister of the Environment, Mr. Bagnell, joined with Mme Sauve, the federal Minister of the Environment, in calling for a new assessment of the project's environmental effects with particular emphasis on the segment involving the Chéticamp River system. Details of the agreement were contained in a March 1975 joint Canada-Nova Scotia press release. The Nova Scotia Department of the Environment was to be responsible for the coordination of the assessment and the NSPC was to produce the Environmental Impact Statement (EIS) under joint guidelines approved by the federal and Nova Scotia Departments of Environment. Both Environment Departments were to co-chair a public meeting on completion of the EIS. The federal government chose the Environmental Assessment and Review Process (EARP) as the federal review mechanism. All Panel members came from the Department of the Environment with the exception of one member from Parks Canada.

A series of public meeting and public consultations were held in Baddeck, Halifax, and Sydney. The Final Environmental Impact Statement was produced by the Nova Scotia Power Corporation and distributed in May, 1977. Following review, the Nova Scotia Department of the Environment found that all provincial environmental concerns had been adequately dealt with.

In the end the Panel concluded that the Cheticamp portion of the Wreck Cove hydroelectric project may be constructed and operated with acceptable environmental impact provided the recommendations advanced in their report were implemented.[7]

Between 1975 and 1978, more than 2.5 million cubic metres of rock were blasted and removed to construct the facility’s 11 major dams and associated wing dams. All are earth dams or rockfill dams with an impervious material in the middle (the core dam), with filter material at both sides and rockfill on each dam for stability.[8]

The development involved the diversion of seven headwater streams, including Indian Brook, West Indian Brook and MacMillan's Brook, Wreck Cove River, MacLeod's Brook, the Ingonish River and the headwaters of Chéticamp River. Several large lakes were formed, Wreck Cove Lake, Gisbourne, MacMillan Lake, Chéticamp Lake, all linked by canals and tunnels, guiding the water to Surge Lake at the head of the penstock, where it drops to the underground powerhouse and then follows the tailrace tunnel to the sea.[9] It required one of the largest fleets of earth-moving equipment in Nova Scotia’s history and employed approximately 900 people.

The Wreck Cove Hydro Station produced its first energy on 27 March 1978.[1]

There are 21 dams of various heights and lengths holding back the several reservoirs that make up the Wreck Cove Hydroelectric System:

Water moves from Chéticamp Flowage (El. 464 metres (1,522 ft)), via canal C-1, to Ingonish I (El. 437.4 metres (1,435 ft)), then canal C-2 to Ingonish II (El. 436 metres (1,430 ft)) reservoirs, and on to canal C-3 which discharges into Gisborne Flowage (El. 390 metres (1,280 ft)). Here is it joined with water from MacMillan Flowage (El. 404 metres (1,325 ft)) via tunnel T1, a 4,877 metres (16,001 ft) long, 2.5 metres (8.2 ft) diameter tunnel, to Gisborne, where electricity is generated through the Gisborne Powerhouse's horizontal turbo generator unit. The water then follows canals C-5 & 6 to the Wreck Cove Flowage Reservoir (El. 365.8 metres (1,200 ft)), and then travels via T2, a 610 metres (2,000 ft) long 3.65 metres (12.0 ft) diameter inverted siphon tunnel, to the head pond, Surge Lake. A blasted, concrete lined penstock, 4.15 metres (13.6 ft) in diameter, then carries water down 365 metres (1,198 ft) to the power house below.[2][10][6]

The Wreck Cove station’s powerhouse is located 275 metres (902 ft) underground, accessible down a 620 metres (2,030 ft) access tunnel.[3][10] The powerhouse, which was carved out of the granite of the mountain, is 51.8 metres (170 ft) long, 18.3 metres (60 ft) wide, and 28.7 metres (94 ft) high (from the base of the valve wells to the roof). The bottom of the valve wells are 3.5 metres (11 ft) below sea level, the centreline of the turbines are at an elevation of .3 metres (0.98 ft) above sea level. The main floor of the power house is at 9 metres (30 ft), with the cavern's roof arch rising to 25.2 metres (83 ft) above sea level.[10][6]

At the base of the power house, the concrete lined penstock transitions into a bifurcation and steel lined horizontal penstock, 45.7 metres (150 ft) long. These now paired penstocks deliver the high pressure water to the two 2 metres (6.6 ft) diameter spherical turbine inlet shutoff valves (Dominion Engineering Works) that feed into Wreck Cove's two vertical 101 MW francis turbine (Mitsubishi Motors) generator units (Canadian General Electric).[2][6][11]

The water then is carried to the tailrace,[12] which is another 1,705 metres (5,594 ft) tunnel approximately 6.7 metres (22 ft) wide. The slope of the tailrace is very low, about 1 metre (3.3 ft) in 300 metres (980 ft) (a 0.028% downslope). The top of the tailrace at the sea is always above high tide though the base is at 3.6 metres (12 ft) below sea level.[8][6] All in all, water will have travelled as much as 30 km from the Chéticamp Flowage to the tailrace's outlet at the sea.

The Wreck Cove plant design is creative; hydro turbines frequently rely on large water volume and flow rates to operate. In this case, the series of dams on the plateau 365 metres (1,198 ft) above the powerhouse provide a supply of very high pressure water to the hydro turbines for electricity generation, requiring less flow for the same output due to the high pressure differential. Wreck Cove takes advantage of the Cape Breton Highland's natural topography to provide cost-effective, clean electricity.[1]