C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003
Special Report - Technical Theme 5
SYSTEM DEVELOPMENT
A. Arcos
Chairman - Spain
J. Corera
Rapporteur - Spain
Jose Corera Session 5 Special Report - 1 -
C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003
Jose Corera Session 5 Special Report - 6 -
C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003
INTRODUCTION
The session deals with the following topics:
- assets management and maintenance policies
- deregulation impact and benchmarking
- network development
- methods and tools for planning
A total of 62 contributions has been received.
1. BLOCK 1
1.1 ASSETS MANAGEMENT AND MAINTENANCE STRATEGIES
The regulatory frameworks that affect most Distribution Utilities are pushing strong cost-cutting regimes, while keeping or improving service quality. As a result maintenance strategies, and in a wider scope assets management strategies, are being revised and refined to improve efficiency.
a) Maintenance strategies and Reliability-Centred Maintenance
RCM in different variances, and other maintenance techniques are investigated in the following contributions.
Question 5.1. Taking RCM to the field is a complex task, and requires good reliability records. Which large scale experiences can be reported on the usage of RCM, and which are the returns so far? Is there experience in applying RCM outside substations?
Question 5.2. What is the experience of utilities in disseminating to their field force advance maintenance criteria (instead of routine maintenance)?
Paper 5.1 (Sweden) presents an enhanced RCM method. Two techniques are used to evaluate how Preventive Maintenance (PM) improves reliability, and tested with data from MV cables from Stockholm city network.
Paper 5.2 (Germany) proposes to focus maintenance to the most critical or important components in the network, thus making maintenance is more effective. A 110 kV network is analysed, and transformers are selected as the components where PM can improve availability. The study reports that a few transformers are the main responsibles for a large portion of energy not delivered.
Question 5.3. Ranking the importance of transformers from the point of view of maintenance implicitly means they are not moved in the network. Could the experience of this paper be extrapolated to other utilities?
Paper 5.3 (Sweden) proposes a simplified RCM method, applicable to any Distribution network, which they expect to reduce the effort and money an extensive RCM would require.
Paper 5.4 (UK) focuses on the convenience of applying condition-based monitoring to schedule maintenance, and lists the techniques available to assess the situation of each particular component.
Question 5.4. The cost of evaluation of the condition of the assets has to be taken into consideration. Could the authors give an overview on the costs involved in the techniques discussed?
Paper 5.5 (Germany) proposes the use of fuzzy logic to decide either the replacement of certain components of the substation or the complete renewal, based on the condition of the elements and their relative importance in the network.
An integrated system for maintenance scheduling is presented in paper 5.6 (Germany) which uses Dempster-Shafer’s theory of evidence, which helps to deal with the data available on the status of the components, typically incomplete and even inconsistent.
Paper 5.13 (Norway) presents a proposal to take maintenance decisions on protection equipment in substations, based on monitoring real-time parameters which are acquired today by numerical protections.
Paper 5.15 (UK) presents the concept of “health indexes”, which try to resume in a single figure the condition of each network asset. This “extreme” simplification is valuable for overall, long term business decisions.
Question 5.5. Evaluation of condition can be difficult, specially for assets outside substations. How do the authors deal with them, for the calculation of Health Indexes?
Paper 5.16 (UK) defends sample-based condition monitoring techniques instead of periodic maintenance policies involving invasive maintenance (dismounting the components), the last ones prone to cause future malfunctions by themselves.
A large-scale implementation of a maintenance system is reported in paper 5.11 (Spain). With 1.800 users, the applications covers PM, CM, inspections and reliability. Benefits expected are 15% reduction in personnel costs, 20% reduction on external costs and 15% increase in investment efficiency.
Question 5.6. Could other utilities report on the experience of maintenance systems in the field? To which degree these maintenance systems are integrated with the ERP and the inventory of the company, and could they report on the difficulties found on this integration?
Question 5.7. Are utilities using data terminals or portable computers in the field to support maintenance activities?
Paper 5.12 (Romania) presents a study to refit the transmission substations in Romania for the years 2001-2010, under the perspective of the integration with the UCTE. The plan takes into account the relative importance of the substations.
Paper 5.17 (Yugoslavia) presents a study that ranks lines to be renewed based on the cost of energy not supplied to customers, calculated by a reliability analysis of the lines.
Question 5.8. Automation can be sometimes an alternative to equipment renewal, as it improves the line reliability. Could this possibility be considered as an alternative to change the ranking of lines to be renewed, in the authors methodology?
b) Assets management
Assets management represents a new model for the utility, where assets are the source of revenue and are to be managed (operated, maintain) in the most efficient way, using centralised decisions. This new concept of organisation is intended to maximise the margin obtained, however the requirements from the information point of view are much more than in the past, as knowledge has to be systematised and concentrated (instead of being disseminated in the field organisations) so the assets owners can take accurate decisions. Three contributions are received to this topic.
A comprehensive coverage on Asset management information requirements is given in paper 5.7 (Netherlands).
Paper 5.8 (Norway) analyses the integration of the information systems to support assets management. Systems considered are the Network Information System, the Enterprise Resource Planning System, the SCADA system and the Customer Information system. Important aspects are the adequate allocation of the functionality to each systems, the complexity of the maintenance of the interfaces and the users ergonomics, proposing to give to each type of user a single interface.
Question 5.9. The large effort required for implementation and maintenance of the systems mentioned has a return which is sometimes difficult to evaluate. Could the authors report on the cost-benefit analysis of their experience?
Question 5.10. Paper 5.8 makes reference to the initiative of IEC TC57 WG14, that standardise the interfaces between applications in Distribution. Are utilities following this effort? Would they be willing to implement such interfaces, provided the impact on running systems?
Paper 5.9 (Netherlands) reports a successful experience of implementing an assets management organisation in a 1.400.000 electricity and 900.000 gas customers Utility in The Netherlands. Investment level is reported to be reduced by 40%, while quality of supply has improved.
Question 5.11. The organisation roles of asset manager, asset owner and service provider could result in a larger organisation. How was this overcome in the experience reported?
Question 5.12. Implementing an assets management organisation can require the formalisation of internal contracts, with reference prices for the services, etc, which can involve excessive managerial effort. How did the authors dealt with this issue?
1. 2 NETWORK DEVELOPMENT.
This preferential subject includes 14 papers, which have been classified in 4 areas, representing the more relevant issues of the electrical industry for network development.
They are:
· Rural distribution
· Losses management
· Reliability
· New initiatives to improve network development
a) Rural Distribution
The first paper 5.24 (Croatia) presents a practical example for long term extension of a rural network, and proposes optimal policies that take into account reliability and costs.
Paper 5.27 (South Africa) develops models for network capacity increase by improving the usage of voltage regulators and by adjusting the MV/LV transformers. It includes an optimisation study of a real feeder.
Paper 5.59 (France) presents a device with solid-state control that control voltage downstream low voltage networks (named voltage adapter shifter). 100 prototypes are installed in the field. Also presents a three/mono transformer to connect monophasic loads. These devices are intended for rural networks.
Question 5.13. Which are the main issues for efficient rural network extension? Where is the balance between service quality and the extension needs?
Finally, paper 5.33 (Belgium) presents a solution for areas where only transmission network is available; the solution proposed is to adapt the technology of an SF6 inductive voltage transformer and connect it to one phase of the lines, so it can provide power similar of a rural transformer.
Question 5.14. ¿Which can be the consequences of installing multiple single-phase devices on network reliability? These long lines are used for power transmission generated in large power plants. Does the study evaluate the possible economic loses due to the effect on the availability of the lines, in contrast with the service given to the inhabitants of these low populated areas?
b) Losses Management.
The second topic, loses management, includes two papers 5.18 (Romania) and 5.21 (Spain). The first paper describes the loading level of lines above which the cost of the losses justifies the upgrade of the capacity of the line. The other justifies the usage of high efficiency transformers (reduced losses in the windings and the iron) for the losses saving along the life of the transformer.
Question 5.15 Has it been considered within the economic analisys the savings due to the Kyoto protocol (compromises to reduce emissions of CO2)?
c) Reliability improvement
The first paper 5.23 (Czech Republic) proposes the usage of a zero cable between 2 MV/LV secondary substations to increase the reliability of the network. The novelty resides in that the cable is connecting two feeders in their middle point, without any load connected two it, and it is normally opened and telecontrolled.
Paper 5.25 (Spain) describes the opportunities to improve network reliability by migrating from a topology type Merz to a more reliable topology. The consequences on reliability are studied on new telecontrolled substations. Techniques of states enumeration are used, and applied to the Region of Buenos Aires, Argentina.
Paper 5.26 (Italy) describes the application of new technologies to the development of new network concepts and network structures, using reliability probabilistic criteria for the network components, instead of the traditional n-1 analysis (which is deterministic). Together with it, the risk of increment of distributed generation in MV networks is analysed.
Paper 5.30 (Netherlands) discusses how the usage of techniques of probabilistic risk analisys can allow better decisions, based on mean values and standard deviations. It also deeps on methods of demand forecast.
Finally, paper 5.34 (Germany) studies the renewal of network components in a mature distribution network, using tools of reliability analysis. O&M costs can be diminished without a deterioration of quality of service.
Question 5.16. Which techniques can electric utilities employ to adapt in an efficient way to the regulatory compromises of quality of service? Are classical deterministic methods adequate? De they demand in excess?
d) New initiatives to improve network development
The first 2, papers 5.19 (India) and 5.20 (Thailand) discuss the usage of FACTS to improve the reliability and the capacity of the existing networks.
Paper 5.28 (South Africa) analyses different criteria for measuring voltage quality based on probabilistic techniques, to reduce the risk of error.
Finally, paper 5.29 (South Africa) presents the process of dissemination in the different areas of the company of the methods and techniques for planning and investments decisions, and comments on the problems found.
2. BLOCK 2
2.1 DEREGULATION IMPACT AND BENCHMARKING
Deregulation in the electrical sector keeps Distribution as a regulated business, being one of the more controversial topics how the revenues are to be established and revised along the years. Reference networks are considered in many cases a starting point to evaluate the capital costs to set up the network and to evaluate the future O&M costs. However, as Distribution utilities are numerous and with a different history, the tuning of the model to make it applicable is a point of discussion. It should benefit the improvement of efficiency and the quality of service. Comparison between utilities is also a way to evaluate and encourage better performance. The model has to take into account the reasonable losses in the Distribution network, and promote their reduction, in benefit of the whole system.
Losses evaluation from the regulatory point of view are considered in 3 contributions. The overall framework is presented in 2 papers, and finally one paper discusses benchmarking.
Paper 5.36 (Spain) discusses that the Distribution network electrical losses allocated to each customers within the current Regulatory framework in Spain are based on Loss factors (DLF) whose simplicity does not reflect reality. A new DLF scheme is proposed based a real calculation of losses separately for the HV, MV and LV networks, and for each of the 6 time periods of the day. Resulting factors are said to be more accurate, and could be used for regulatory purposes.
In the same line, Paper 5.37 (Belgium) presents a method to estimate losses in MV networks; LV losses are calculated just by balancing energy input-energy consumed by customers, along a period of 5 years to reduce the errors of lack of simultaneity of reading of the customers.
Paper 5.38 (UK) indicates that the current revenue mechanisms in UK do not give enough incentives to more efficient equipment, as losses reduction is not sufficiently rewarded. Utilities try to minimise capital investments. Additionally the paper analyses two samples of LV reference networks that, although theoretical, can serve as a target for the real networks.
Question 5.17. Is the opinion of Utilities in the same line, that the current restrictions to investment make losses reductions a second importance criteria when building new networks?
Paper 5.39 (Sweden) presents the new model for regulating distribution utilities in Sweden, which is now being developed. The model evaluates the cost of running (yearly cost of capital invested, operations and maintenance) a reference utility that would have the same customers and energy traffic, adding an additional premium for quality of service. The revenue calculated will be used as reference revenue for each utility.