Stanislav Rusek

Discrete maintenance optimization of complex multi-component systems

Abstract A complex multi-component system consists of finite number of non-identical components that can be realized as maintained components with different maintenance modes. We distinguish between four component models: non-repairable components, repairable components with corrective maintenance, repairable components with latent failures that are identified by means of preventive maintenance and component with preventive maintenance policy in which the component is restored (either repaired or renewed). The paper describes a new method for optimal maintenance strategy of a complex system respecting a given reliability constraint. It is based on our previously developed direct analytical method that enables exact reliability quantifications of highly reliable systems with maintenance. The method takes into account complex systems with maintained components, including all above models. Cost-optimization problem is solved where decision variables are changeable maintenance parameters that are optimally selected from a set of possible realistic maintenance modes. As a discrete maintenance model in this paper is considered such a model, where each maintained component can be operated in one or few discrete maintenance modes. One maintenance mode is characterized by fixed decision variables that affect maintenance cost of the mode. If a system hypothetically contains k components with 5 independent maintenance modes, in total we have 5 k maintenance configurations of the system, from which the optimal is found. The optimization method is demonstrated on real system from practice – a complex power distribution network.

The input analysis of parameters and expected operation modes of energetic technologies in technological centre ENET

This paper deals with a description and partial analysis of energy production units and their implementation in the laboratories of ENET technological centre in Ostrava - Vitkovice. The paper refers to individual types of conventional and non-traditional sources of electric power that are connected to the technological centre distribution grid, together with analysis of their topological configuration, with a presentation showing division of individual power sources into logical technological groups with definition of either nominal or estimated operating parameters. The data summarised in this paper will serve mainly as input material to design a dynamic model, for modelling of transients and short-circuit ratios mainly on non-traditional energy sources, as well as full energetic systems already implemented. That is why the paper also addresses an introduction of concept and expected software products for future creation of the model.

The problems of electrical distance in connection with the operation of wind power generator

Renewable sources of electrical energy (especially the wind power generators), which have been lately promoted, are causing problems in distribution and transmission operation networks. Variable supply (or load) of electrical energy cause voltage fluctuations in the distribution networks, changes in short-circuit ratio, and also affect active losses in the network at the expense of distribution companies. Alternative generators of electricity influence the distribution networks not only by their output power, but also by their electrical distance from the supply network, i.e. mostly from the distributing point of the superior system. The issue of electrical distance is currently seen only in relation with the short-circuit effect (short-circuit contribution of individual generators). The presented paper correlates the electrical distance of the connection point of wind power generators in the distribution network of medium voltage (22kV) from the 110kV power supply node and the voltage effect on the distribution network and the 110kV power network.

Analysis of properties of power inverter digital model at the ENET technological centre

This paper describes the analysis of power generating units and their implementation, these are located within the technological centre in Ostrava-Vitkovice. Further issues concerned in this paper deal with digital simulation using computer model created using the EMTP — ATP software to evaluate particular process courses that may occur on the power inverter installed in the technological centre. The data summarised in this paper will serve mainly as input details for development of a dynamic model. The data from this digital model will be then compared to the values measured on the real power inverter.

Software solution design for application of reliability centered maintenance in preventive maintenance plan

The implementation of Reliability Centered Maintenance into Preventive Maintenance Plan scheduling is one of the possible paths towards cost reductions in the fields of diagnostics and operating personnel. There is also the assumption of maintaining acceptable reliability of individual devices within the entire network. The devices to be considered suitable for application of RCM concern network elements present in sufficient quantities, supported with enough experience relevant to maintenance and with the data obtained through operative measurements and protection available. This data set forms ideal fundamentals for analysis and status assessment of a particular device. Provided the current status of a system element is known and it future development can be expected, the maintenance interval can be adjusted — giving priority to PMP applicable to devices in unsatisfactory condition and postponement of PMP for devices in good condition. This paper describes the design of software for PMP priority assessment pursuant to the RCM method with respect to priority assigned to electric power supply and evaluation of consequences for customers.

Software Determining Optimum Order for Maintenance

The paper deals with the development of Reliability Centered Maintenance software for distribution system network elements. In this case describes the order of maintenance for transformers 110 kV/MV. When determining an optimum maintenance sequence, the appropriate parameters of technical conditions and operational importance are required. The database of input values referring to the technical conditions and importance has been completed over the recent year. This paper describes processing of such input databases to create a format required for subsequent calculations and the first results that is the definition of order for maintenance.

Analysis of results for 110 kV power lines restoration methodology

This paper focuses on restoration methodology for 110 kV power lines. Principle of reliability centered maintenance is used in the restoration method. The input data is typically collected in the operation of the distribution network. The data distributed concerns the power, the database of faults and the effect of failure. Functional application is used to determine the results and analysis.

Processing of input databases of technical condition and importance and definition of order for maintenance of 110 kV / MV transformers

The paper describes another part of the work to define the order of maintenance for transformers rated 110 kV / MV. When determining an optimum maintenance sequence, we require the appropriate parameters of technical conditions and operational importance. The database of input values referring to the technical condition by importance has been completed over the recent year. This paper describes both the very processing of such input databases supplied to crate a format required for subsequent calculations as well as the first results of the processing that is the definition of order for maintenance.

Stages of development of 110 kV power lines restoration method

The paper describes 110 kV power lines restoration method based on reliability centered maintenance and its development. The database of faults is used to determine technical condition. The distributed energy and effect of failure are used to determine the importance of line. A functional application was developed to debug the methodology.

Confidence intervals in reliability database

The paper deals with the computation of distribution network component reliability parameters. Current values of the component reliability parameters in distribution network are used for the reliability computation and also for reliability-centered maintenance system. The reliability confidence parameters are calculated for accuracy.