The Uncle Gnarley Blog has a new website. Click here to visit to view the latest posts!

Thursday 3 November 2016


Guest Post Written By Phil Helwig, P.Eng. (Retired)

Phil Helwig is a retired Engineer and Hydropower Consultant with over five decades of experience -  much of it right here in Newfoundland and Labrador. He has been a frequent writer to the Telegram on the North Spur stability problem as well as on other issues including power reliability and security.

This is Helwig's first contribution to the Uncle Gnarley Blog. It is a timely one, too. In recent weeks readers have seen posts regarding the Phase I Report of the Public Utilities Board (PUB). It dealt principally with the findings of the Liberty Group's investigation into the root causes of DARKNL. In late August Liberty filed its Report on Phase II of the PUB's mandate which includes consideration of security and reliability issues in the post-commissioning of Muskrat Falls. Phil Helwig has now distilled this Report and comments on the concerns of the Liberty Group for Uncle Gnarley readers. I am pleased to welcome him to the blogosphere and say that I am very grateful to him for lending his expertise in such an important public policy area. - Des Sullivan

                                 ADEQUACY AND RELIABILITY 

Phil Helwig, P.Eng. (Retired)
Liberty notes that the in service date of Muskrat Falls is delayed until 2020-21 a slippage of 3 years. This delay extends the period of vulnerability of the Island System (IIS), since no new on Island generation sources are planned. This is partly mitigated by the reduction in the load growth forecast.

Liberty divides their report into two parts the first considering the IIS prior to in-service of Muskrat Fall and a second part dealing with the interconnected Labrador-Island-Nova Scotia System.

Island System prior to infeed from Muskrat Falls:

1.  Liberty notes ongoing problems with Hydro’s thermal fleet, Holyrood (2x170, 1x150 MW), Hardwoods C.T. (50 MW), S’ville C.T. (50MW). The new Holyrood C.T. (120 MW) is presumably reliable.

2. The situation is somewhat mitigated by the fact that the forecast load growth after adjustments in 2016 reduce the load growth to 2019/2020 from 1.9% to 1.4% or 0.63% and 0.46% on an annual basis. (This is much less than the 2.0% per annum in Nalcor original proposal!!)

3.   Liberty found Hydro’s load forecasting procedures as outdated and likely to underestimate peaks compared to more modern approaches in use by most large utilities in North America. I was surprised that Hydro defined their estimated peak at the 50% probability level: that is accepting a risk that 50% percent of the time the actual peak would be larger than forecast. Liberty noted that the 90% point is more commonly used implying that a forecast would be exceeded 10% of the time.

4.  Liberty identified several risks that need to be addressed in Hydro’s forecast, notably a forecast risk. What is implied, but not stated in this last recommendation, is a feeling that if Hydro’s forecast errors over one year 2015 to 2016 are significantly lower than previously expected; then next year’s forecast could err on the high side.

5.  To Liberty’s list of risk factors I would add a climate risk. As heating loads comprise a significant portion of IIS, severe winter conditions would produce higher system peaks requiring more resources; whereas, mild winters would produce lower peaks and require fewer resources.

6.   Liberty suggests that new sources of supply for the IIS may be need before the winter of 2020/2021 when Muskrat power becomes available. Additional generation and other options for dealing with this shortfall in peak power are discussed at some length in their report.

7.  Liberty notes that management of the challenges until 2020/21 is not limited to technical issues but is equally dependent the ability of staff to manage contingency situations. In this regard Liberty, note their concern about Hydro’s culture. This issue is pursued later in Section V, page 81 on tolerance of UFLS (under-frequency load shedding) and in Section VI, page 90 on Transition to Operations (planning). Their comments on Hydro’s culture present a rather narrow view of this matter in my opinion. I think there may be more profound issues, notably: problems of political interference. I suspect there may still be other issues but I am not familiar enough with Hydro’s current set up to be a credible critic.

Labrador-Island Link (LIL):
1.  Liberty provides a summary of the features of the HVDC system explaining its performance, resilience and also vulnerabilities. The biggest risks are associated with the mismatch between the size of the Labrador infeed and the relatively small size of the Island System. Additionally, they note the increased complexity of the LIL System and the demands this will put on Hydro management. Essentially they are saying that the new scheme represents promotion from the minor to the major leagues and will require a totally new company (and operating culture).

2.  Liberty notes that the LIL has considerable resilience in that it can still meet most of the forecast load with one pole out of service (monopole failure). A bipole failure while less frequent is the main reliability concern as the IIS will have difficulty with coping with this condition especially as the IIS matures. Nalcor is counting on the supply of power from N.S. to mitigate the problem, but there is no agreement about the modalities.

3.   Some questions about design are mentioned. The first involves the spacing between cables. Liberty mention the spacing to be as little as 50 m. Earlier concepts called for much wider spacing to reduce the risk of simultaneous cutting of more than one cable by an iceberg scouring the sea bottom. The second of these design decisions involves routing of the LIL T.L. over the Long Range Mountains where icing conditions are particularly severe. An alternative route along the Humber River and TCH would have avoided the high elevations of the Long Range Mountains where icing problems are extreme. The current design is less conservative but the reasons for the changes have not been explained in any of the several presentations on Muskrat Falls that I have attended. Newfoundland Power questioned the risk of failure of the ground(ing) wire due to icing and the consequent risk of shorting out one or other poles. The concern arises because the ground wire is lighter than the conductors but (may) support an ice load equal to that of the conductors. Nalcor claim they have evaluated the issue and concluded that the cost of a stronger wire is not justified.

4.   Liberty notes that limited data is available on cable failures based on experience of power cables. It does not appear that any of the much more voluminous information on subsea communication cable breaks was consulted.

5.   Though not mentioned explicitly, reliability problems will be less in early days but become more of a challenge as the LIL matures.

6.     Liberty is sceptical about Hydro’s assumptions about the time required to repair damages to cables or OHL; noting, that failures are likely to occur during periods of bad weather that complicate repair work and problems of access due to remoteness of many portions of the T.L.

7.   Liberty reviewed the main issues concerning reliability of the converter station and under-sea cables, OHL but notes the following issues that were not addressed:

·       Tripping of some or all ac lines to Muskrat Falls Converter Station
·       Tripping of some or all ac lines to Soldiers Pond Converter Station
·       Delays in clearing faults near to Muskrat Falls or Soldiers Pond
·       Major faults, e.g., fire or extensive insulation damage to 2 or more high inertia synchronous condensers, requiring repair at times of high loading on the LIL
·       Operator errors
·       Major fires in the convertor stations.

They recommend that these issues be evaluated in Hydro’s reliability studies. In my opinion several of these items can be dealt with by proper design and quality training.

8.  Liberty is concerned about Hydro’s management of the Transition to Operations and provides scopes and staffing requirements needed for this work, see Section VI: Transition to Operations, page 90 in their report. The note and I quote: “Future reliability depends as much on such people related improvements as much as it does on the billions of dollars of investment.”

9.   The point that most grabs my attention is Liberty’s recommendation that Hydro, as a top priority, should work out a deal with N.S. Power over (emergency) supply. This should have been done long ago. Furthermore, Liberty mentions that we may have to pay for this service - when N.S. is getting Muskrat Falls energy for free!!! This is unacceptable in my opinion, should it ever come to pass.

10. Though not discussed by Liberty - the design of the protection and control system is critical in maintaining system stability when the system is stressed by major faults. The design should be verified against all plausible perturbation/system faults. My guess is that the loss of a power transformer that triggered the 2014 blackout may have been omitted in Hydro’s analyses.

Signed: Phil Helwig
Editor's Note:
Phil Helwig has had a varied engineering career in both education (8 years) and in design and technical management (44 years). Most of his formative experience was with a small company in Newfoundland (ShawMont) which valued versatility, as a result Phil was able to develop expertize that goes well beyond the skills set normally associated with his formal area of competence, as a hydrotechnical specialist. His main area of expertize is in the fields of hydropower and water resources where he has been involoved in investigations, economic planning and project optimization studies and detailed design. He has been responsible for several innovations in Canadian practice: notably, the design of Cat Arm Hydel unlined pressure tunnel (head = 386 m) and “bathtub overflow spillway” and design of Hinds Lake Power Canal based on natural armouring (the first application of this technology in hydro design world wide) and the design of Paradise River double curvature arch dam only the third arch dam ever built in Canada. More recently from his experience in South Asia he has developed expertize in design of hydraulic structures to handle water borne sediment. His latest interest is in the field of eco-hydraulics. In 2004 Phil formed his own company, Helwig Hydrotechnique Ltd. and has worked on four continents in three languagesTechnology transfer is an integral part of all Phil Helwig’s assignments.