Relejaizsardzibu un pretavarijas automatiku sistemas elementu sinteze

Sophistication of the electric power system, rate and complex nature of its processes demand high efficiency of the control, that might be achieved only by ensuring automation of these processes. The most prominent spheres of power systems automation are protective relaying (PR) and emergency preventive automation (EPA). New epoch of power systems development was initiated by implementation of the microprocessor circuitry. Application of microprocessor base offered new opportunities not only for creation of complex, technically perfected PR and EPA devices, but also for creation of integrated systems involving PR and EPA devices. The goal of the present study was to develop technical means and methods of PR and EPA microprocessor systems for electric power systems based on wide application of microprocessor systems, to work out software and hardware, and systems of control and diagnostic. Economic situation in the Baltic States was taken into account, where a significant number of outdated equipment in electric power system is in operation yet financial base does not contribute to a large-scale implementation of the expensive equipment. For achieving the set goal there has been accomplished: - The analysis of development of PR and EPA microprocessor devices, means for the set up and test, software and data transfer devices, virtual and statistical virtual testing methods of sophisticated PR and EPA devices are suggested, substantiated and worked out. - The calculation algorithm for the derived parameters, which is used in deployment of expert systems of emergency events analysis is proposed and implemented. - Software for data exchange among PR and EPA terminals and protective relaying service personal computers; terminal setting editors and the system for events control is worked out and implemented. - The system ensuring generators parameters control, display and analysis of the data received is created. - The method for correction of non-linear converters is suggested, substantiated and implemented. The results of the conducted research and development are widely applied in Latvian, Lithuanian, Estonian, Russian and Mongolian electric power systems. The items implemented: - The software for data exchange "REMILINK" and "AUTOLINK". - The program for displaying emergency processes Smoky. - The software for virtual tests execution "ANIMATOR" used for testing and setting more than 300 microprocessor terminals implemented, including; - Recorders of emergency processes "REMI" - Complex protections of power transmission lines "REDI" - Units for elimination of asynchronous operation "AGNA" Detectors for fault location in 110-750 kV power transmission lines "REMI-FL" - The system for control of generators parameters.Abstracts in Latvian, English, Russian. Separate summary in Latvian and English, 52 p.Available from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi

Improvement of the Sensitivity of Differential Protection of Power Transformers

This paper presents the development of micro-processor based device for improving the sensitivity of differential protection of power transformers. Power transformers failure may lead to high scale system’s operations disruption and heavy economic losses, that’s why the lever of requirements for power transformer protections is so high. Differential protection is usually used as a main protection against internal faults such as inter-windings faults, inter-coil faults or coil-core faults. For safe protection against incomplete winding faults protection device must be capable to detect differential current from such a low value as 0.01% from nominal. However, transformer for relay protections needs are produced with error classes 5P and 10P meaning error rate 5 and 10 % correspondently. The idea for a new device is to use information obtained from measurement current transformers. The micro-processor based device may “teach” itself by forming some error correction table in it’s memory on the basis of core outputs compare during normal operation. In case of fault device may operate with much higher sensitivity thus sensing fault on it’s early stage

Mācību līdzekļi relejaizsardzības laboratorijā

Tiek realizēts projekts - laboratorijas mācību stendu veidošana. Tā galvenais mērķis ir paaugstināt apmācības kvalitāti, dot praktiskas iemaņas, ieinteresēt studentus jauna materiāla apgūšanai. Jaunu mācību stendu izveide ir nepieciešama laboratorijas iekārtu atjaunošanai. Dotais stends konkrēti ir paredzēts virzītas nullsecības strāvas aizsardzības izpētei. Ar tā palīdzību tiek plānots veikt laboratorijas darbus, kuros studentiem tiks dota iespēja patstāvīgi uzdot aizsardzības iestatījumus, kā arī izsekot notikumu attīstību dažādu bojājumu gadījumos

Phase Plane Usage for Convergence Analysis of Seidel Method Applied for Network Analysis

This paper presents the convergence analysis of Seidel method for solving power systems automatic tasks. In a condition of use of Programmable logical controllers with low capacity as a hardware, algorithm solution based on Seidel method have some advantages, such as memory saving. However, there are some limits for Seidel method convergence. If the electrical network condition is close to resonance there will be no assurance that Seidel method will converge. As a result of made experiments we can conclude that usage of relaxation method in conjunction with convergence control on the phase plane allows to solve network analysis problem with nonexpansible hardware

Signal Extraction from Inrush Current for Inter-Winding Fault Protection of Power Transformers

In case of transformer failure there is a high risk of losing part of power system, which can result in disruption for consumer power supply. This is the main reason for power transformer protection requirements to be so high. Power transformer is a complicated object considering its protection. Sensitivity level is a key element in inter-winding faults detection. Incomplete winding faults that occur in the multi-wire transformer windings, when multiple parallel wires form a coil, are very hard to detect, this is why it is the most challenging issue for the differential protection. Our idea is in creating a microprocessor based device that will use an inrush current surge as an information source for inter-winding fault detection within transformers

Internal Winding Fault Protection for Shunt Reactors

Existing protection techniques for shunt reactors can’t guarantee sufficient sensitivity for inter-winding faults due to limited precision of current transformer. To solve this usage problem of input resistance of resonance contour formed by reactor bank inductance attaching wiring capacitance is proposed. Difference between input resistance profiles of damaged and healthy bank is used as a fault criterion

Experience of Transformer’s Inrush Current Modeling for the Purposes of Relay Protection

In case of transformer failure there is a high risk of losing part of power system, which can result in disruption for consumer power supply. This is main reason for power transformer protection requirement to be so high. Power transformer is a complicated object considering its protection. Sensitivity level is a key element in inter-winding faults detection. Our idea is in creating an additional function that will use an inrush current surge as an information source for inter-winding fault detection within transformers. However it is absolutely impossible to perform multiple tests with real megawatt class transformer. That is the key why it is so important to make a correct model and to be sure that model is identical to real transformer. We choose Matlab+Symulink+ Symscape+SymPowerSystem combination as modeling environment, we have tried multiple environments and selected this one as best performing. To verify our model we use measured data from small test transformer

Current Transformer Error Correction

This paper presents the development of micro- processor based device with ability to decrease protection-type current transformer measurement error in the area of small currents. Measurement transformers are available with a high precision class of 0.2 and 0.5 and maximal measurable current up to double rated value. Transformers, produced for relay protection purposes, are with error classes of 3, 5 and 10 meaning error rates of 3, 5 and 10 % respectively. Our idea consists in a new way for joining the characteristic curves of relay-type and measurement-type current transformers. The micro-processor based device may “teach” itself by forming some error correction table in it’s memory on the basis of core outputs compare during normal operation. In case of fault device may operate with much higher sensitivity thus sensing fault on it’s early stage