Tomasz Babczyński

Time Coordination of Distance Protections Using Probabilistic Fault Trees With Time Dependencies

Distance protection of the electrical power system is analyzed in the paper. Electrical power transmission lines are divided into sections equipped with protective relaying system. Numerical protection relays use specialized digital signal processors as the computational hardware, together with the associated software tools. The input analogue signals are converted into a digital representation and processed according to the appropriate mathematical algorithms. The distance protection is based on local and remote relays. Hazard is the event: remote circuit breaker tripping provided the local circuit breaker can be opened. Coordination of operation of protection relays in time domain is an important and difficult problem. Incorrect values of time delays of protective relays can cause the hazard. In the paper, the time settings are performed using probabilistic fault trees with time dependencies (PFTTD). PFTTD is built for the above mentioned hazard. PFTTD are used in selection of time delays of primary (local) and backup (remote) protections. Results of computations of hazard probabilities as a function of time delay are given.

Dependability and Safety Analysis of ETCS Communication for ERTMS Level 3 Using Performance Statecharts and Analytic Estimation

Dependability and safety in European Rail Traffic Management System (ERTMS) level 3 are influenced by quality of localisation of trains and communication. In the paper, dependability and safety of European Train Control System (ETCS) communication for ERTMS level 3 is considered. In ERTMS level 3, traffic is controlled by so called moving block that is associated with the distance between subsequent trains. Relationship between probability of emergency train braking as a function of distance between subsequent trains is studied. In the study, the following parameters are taken into account: train speed, emergency braking distance, train length, position localization error, random variable of emergency braking and stopping times, parameters of transmission between trains and radio block centres, processing time in these centres. In order to find this relationship, the following methods: performance statecharts based and analytic estimation have been proposed. Quality of these methods is investigated.

Performance Evaluation of Multiagent Personalized Information System

An agent-oriented architecture for personalized information system is considered in this paper. This architecture is composed of four types of agents and is based on FIPA standard. The emphasis is put on performance evaluation, which is based on system dynamics. In FIPA, the most extensive models of dynamics are statecharts. Performance statecharts are such statecharts that are extended by probability distributions of activity duration times and probability distribution for solving non-determinism. Performance analysis of the personalized information system using performance statecharts is carried over in the paper.

PERT based approach to performance analysis of multi–agent systems

The following analytical approaches: queuing network models, stochastic timed Petri nets, stochastic process algebra, Markov chains are used in performance eevaluation of multi–agent systems. In this paper, new approach which is based on PERT networks is proposed. This approach is applied in performance evaluation of layered multi–agent system. These layers are associated with the following types of agents: manager, bidder, and searcher ones. Our method is based on approximation using Erlang distribution. Accuracy of our approximation method is verified using simulation experiments.

Performance comparison of multi-agent systems

Performance comparison of two information retrieval multiagent systems is carried over by simulation. The first system contains stationary agents only, while the second one contains one mobile agent. Performance models of these multiagent systems are expressed by performance statecharts. The performance statecharts are such a modification of UML statecharts that contain probability distributions for activity duration times and for transmission times, and probability distributions in order to solve non-determinism.

Performance evaluation of multiagent-system oriented models for efficient power system topology verification

In the paper, the power system topology verification with use of multiagent systems is considered. Two multiagent systems are taken into account. One of these systems is a modification of the second one. In the modified system, there are additionally so-called substation agents. Stages of analysis, design and investigation of performance characteristics of presented multiagent systems are described in the paper. The goal of the paper is presentation of performance characteristics of the mentioned multiagent systems in terms of probabilistic characteristics of agent activity and created messages. The carried out investigations show that the modified multiagent system has much better features than the earlier system.

Performance evaluation of multiagent systems for power system topology verification

The paper deals with power system topology verification with use of multiagent systems. Two such multiagent systems are considered. The assumed idea allows considering a topology verification of a whole power system as the set of many local topology verification processes. Each of the described multiagent systems performs the topology verification using a different protocol. For each of the multiagent systems, analysis and design are outlined using the Multiagent Systems Engineering. For their design models, probabilistic performance evaluation has been carried out. Then, a comparison of the investigated multiagent systems is made, paying special attention to their performance effectiveness.

Selection of Tripping Times for Distance Protection Using Probabilistic Fault Trees with Time Dependencies

Distance protection of electrical power system is analyzed. This protection is based on local and remote relays. Hazard is the event: remote circuit breaker tripping provided the local circuit breaker can be opened. Coordination of operation of protection relays in time domain is important and difficult problem. Incorrect values of delay times of protection relays can cause the hazard. In the paper, the impact of delay time settings on performance of protective scheme is analyzed using Probabilistic Fault Trees with Time Dependencies (PFTTD). PFTTD are introduced in the paper and used for the above-mentioned hazard analyzes. The outcomes are hazard probabilities as a function of delay time values.

Estimation of mean response time of multi-agent systems

The following analytical approaches: queuing network models, stochastic automata networks, stochastic timed Petri nets, stochastic process algebra, Markov chains can be used in performance evaluation of multi-agent systems. In this paper, new approach which is based on PERT networks is presented. This approach is applied in performance evaluation of layered multi-agent system. Time-out mechanisms are used in communication between agents. Our method is based on approximation using Erlang distribution. Accuracy of our approximation method is verified using simulation experiments.

Virtualization from University Point of View

In this chapter we present some problems connected to cloud computing and in particular to virtualization. At university cloud computing is on the one hand interesting tool for researchers and on the other very interesting topic to research. We present network simulator with nodes done in virtual environment (in this case virtualization is a tool) and scheduling algorithm for cloud computing (in this case cloud computing is object of our researches).