M.B.Barker and B.A. Vivian
Tumut Pond and Island Bend Dams are owned and operated by the Snowy Mountains Hydro Electric Authority. These dams, which are gated, have recently had significant electrical supply and control system upgrades. Subsequent reliability analyses performed for the gates provided unexpected results which highlighted issues concerning common mode failures and common cause failures associated with the mechanical systems. A further unexpected outcome of the analyses was the minor affect of human error and response to the emergency operating conditions of the gates in the event of electrical supply failure due to the over-riding mechanical system failures. This outcome was of benefit to the owners who had some concern that centralization of operation and consequent reduction in operating personnel would have an adverse effect on the reliability of the gates. The operation of the automatic control system is an ongoing issue for Island Bend where hunting of the gate operation is yet to be resolved. The preparation of the fault trees, development of failure probabilities and outcomes of the analyses are discussed in the paper which highlights some of the difficulties in design and operation of spillway gates, particularly where human response time is limited and automatic control is essential.
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Now showing 1-12 of 26 2965:
Neil Gillespie, Chris Hansen
With the introduction of the Resource Management Act in 1991, two significant changes have meant a complete review has been necessary of the planning provisions for hydro generation facilities in plans prepared under the new legislation.
Firstly, the Resource Management Act 1991 introduced an ‘effects’ based approach to planning, as opposed to an ‘activity’ based approach that existed under the previous Town & Country Planning Act 1977. Secondly, the planning mechanisms available to hydro generators to provide for their facilities changed.
Contact Energy Ltd (Contact) is a significant hydropower generator based in Central Otago. The new Regional and District Plans prepared under the Resource Management Act 1991 now contain provisions controlling activities previously provided for by way of a designation. Contact has invested considerable time and effort into the plan preparation process to ensure their activities are not unduly restricted by the new plans.
This conference paper provides an overview of the changes to the planning associated with hydropower generation facilities, and Contact’ s experience in the plan preparation process.
Thomas Zink, Michael Howat, Clive Anderson, Richard Davidson
This paper describes the refurbishment of Diversion Gate No 2 at Roxburgh Dam on the Clutha River, New Zealand. This 53m high concrete, gravity dam constructed in the 1950’s had three diversion gates fitted with stoney rollers which when opened into flow allows the rollers to disengage from the gate precluding subsequent closure. Diversion gate No. I was sealed off with a concrete plug. The remaining two diversion gates are required to provide additional flow control flexibility at the dam. Key aspects of the refurbishment design and construction include the system used to remove silt from upstream of the gate, and the condition of the gate itself and the concrete diversion channel after nearly fifty years of service. Brief details of the commissioning testing are also presented.
Graeme Bell, Robin Fell and Mark Foster
Standards based, dam safety management has always been about managing risks. Risk based approaches attempt to quantify the risks in a formal manner, but are based on the same requirement for good investigation and engineering, and understanding of the physical processes, as standards based methods.
This is demonstrated by the assessment of the potential for internal erosion and piping of Eucumbene Dam. The assessment is a combination of semi-quantitative risk based, and standards based approaches, and considers the likelihood of initiation, continuation, progression to form a pipe, and breach. The filter transition zones are coarser than required to meet modern filter design criteria, but it has been demonstrated by laboratory testing, and relation to the performance of other dams, that if, in the low likelihood erosion of the core initiates, it will after some erosion, seal on the filter transition zone. The downstream zone of rockfill has sufficient permeability to discharge any potential leakage which might occur, so the likelihood of breach of the dam by piping is
P L Campbell, J W Walker and J T Mills
The results of a questionnaire on deformation surveys sent to dam owners around the world are presented. An analysis of the large variation in current international practice is made. The link between geodetic surveys and displacement instrumentation is established. The comparison with practice within a recent major New Zealand dam owner is drawn and a deformation survey policy is developed. Recourse is made to dam safety guidelines. Application of the policy is then described for a selection of differing types of hydraulic structures. It is shown that with the application of the policy a more rational approach resulted, surveys better reflected actual performance and there was better integration with the overall dam safety monitoring programme.
L Joyce and G Macdonald
Claims for negligence against professional advisers are increasingly common. Large dams can, in the event of failure, give rise to large claims by a large number of affected parties. This paper highlights from the perspective of lawyers practising in the field of professional indemnity litigation some of the ways of managing the risk of such claims being made.