In our time, humanity can not practically do without electricity, she has found applications in all areas of human activity and its need for further development of human society is evident. Energy program for the long term provides for further development of EC. Commissioning of large power plants, intensive development of core and distribution networks are extremely complicated problem of managing. In this regard, a continuous process of development and improvement of equipment of relay protection. Razrabatyvayutsya new types of semiconductor differential-phase defenses, which are simpler and more reliable in operation.
Relay protection yavlyaetsya main type of electrical automation, which is impossible without reliable operation of modern power systems. It provides continuous monitoring of the condition and mode of operation of all elements of power and responds to the appearance of lesions and abnormal modes.
Operated relay protection (RE) power systems, primarily performs tasks assigned to it. However, in some modes, it can refuse to act or false work. Protection against earth faults may refuse to act because of an arc in place of circuit [1].
The main requirements to the relay protection:
Selectivity.
Rapidity of action.
Sensitivity.
Reliability [2].
Year by year, tougher requirements for quality electricity supply to consumers, making it all the more responsible role of rare power and all the more urgent task of improving the sensitivity and speed of protection. The prospect of its solution is associated with the introduction of microprocessor technology. A new element base can not only improve the data processing algorithms, but also use more than was possible before, the amount of information about the emergency state of the object. This allows you to achieve greater technical excellence of RE, including the proper operation of the above modes.
Scientific work carried out during the Masters for 2010 — 2011. in accordance with the scientific direction of the Department of Electric Power Stations ", Donetsk National Technical University.
Development of algorithms for RE, which allow to determine the damages, regardless of the saturation of current transformers and the presence of the arc in the injury site.
The main tasks of development.Development of a software system with the further implementation of the learning process.
Item development.Development is done using the software package MicrosoftVisualC++.
ÎThe basis for master's work to develop a method that would allow virtually increase the safety and trouble-free networks own use of thermal power stations.
Report on the theme of "Development of a method determine the modes of intellectual elements of their own needs TES." presented at the XVI All-Ukrainian Student Scientific Conference "Electrical and electromechanical systems, April 18 — 20, 2011, SevNTU, Sevastopol. Also at IX international scientific-technical conference of young scientists and specialists "Electromechanical and power systems, modeling and optimization", ESMO 2011, Kremenchug
Problem definition and analysis of recent research. Single-phase earth faults are the most common type of injury in electrical networks medium-voltage (within 85-90% of the total number of violations of the normal operation of networks in terms of their purpose and design). Under these circumstances, the strong deterioration of insulation in most cases they develop in line to line short circuits or multi-seat breakdown of insulation from the group failure of electrical equipment, followed by a major material damage, and Shortage of electricity to customers. Therefore, we have assumed that the main direction of improving the reliability of electrical networks is to fight single-phase ground fault. That's why most technically advanced countries, including Ukraine, are currently being intensively work on improving the conditions of electrical distribution networks. Mathematical modeling of transients in networks of 6 — 10 kV, many papers [6 — 9 and others]. In these studies investigated surge in networks with deaf and arc fault to earth. However, these models are based on an explicit method of numerical integration of differential equations of the network elements, which in many cases lead to a breach of the numerical stability and do not allow us to investigate many practically important cases of transients.
Research problem. The aim of this work is to develop a mathematical model of the distribution network for transient analysis based on the use of discrete equivalent circuits of its individual elements to ensure the numerical stability of the model.
Summary of the basic material. Typical scheme of distribution mains (Fig. 1) contains a feed transformers, overhead and cable transmission line, load and other elements.
Equivalent circuit of such a network (Fig. 2) contains the active and inductive resistance elements and capacitance and active resistance network isolation. In order to automate the formation of a mathematical model of the electrical system of any complexity will use its graph and matrix-vector write Ohm's law and Kirchhoff [5].
Equivalent circuit of each of the elements of the scheme will be generalized branch (Figure.3) With a sequence-parallel connection of R, L, C elements, which take into account the resistance of the element (R, L) and its isolation on the ground (C, Rc).
The advantage of this representation model for transient analysis is that the algorithm for calculating the steady-state and transient processes remains the same. The difference is that at each step of the calculation of the transition process to update the values of resistance and emf branches.
As we know, the greatest surge in the closing phase of the ground may occur if the time of closure occurs in the maximum voltage faulted phase, and the extinction of the arc - when passing through the \ "Zero \" high-frequency component of the current circuit or component of the industrial frequency. Figure.3 Shows the waveforms of multiple earth-fault phase A.
From the oscillograms it follows that the first closure phase to earth voltage on the healthy phases do not exceed 2.6 Uf values of the amplitude, but during subsequent voltage breakdowns on the healthy phases increase to 4.5 Uf, ie, in this type of circuit the process of escalation of tension. Similarly, there is an increase stress on the damaged phase. The figure also shows the waveforms of the zero-sequence accession damaged LEP2. Residual current damaged accession is in antiphase with the currents of zero sequence other accessions. When the closure phase on the ground, power is usually directed toward the injury site, which is in the range of the relay power lines. Power is calculated as the product p (3Uo) on 3Io [4].
Conclusions:A mathematical model of the electrical system voltage of 6-10 kV, which feature is the use of discrete models of its elements.
Discrete model provides high numerical stability of solutions of systems of differential equations and can be recommended for the analysis of surge and the behavior of relay protection of electric networks for the Deaf and arc fault on the ground.
Relay Series REJ51_, REJ52_ REU51_, REU52_ performed on a modern microprocessor — based and are designed to protect various power projects. Relay function as overcurrent protection (DOLE), undirected and Directional earth fault (OZZ), relays the maximum and minimum voltage, and measuring, signaling, registration and oscilloscope emergency settings. The relays have a communication port and can be integrated into the system to transmit data to PCS venture. Communication is carried out by SPA protocol. There is an opportunity to support standard international protocols (eg, IEC 870 — 5 -103). All relays are compatible and are part of a comprehensive system protection and management of ABB.
Relays are used in secondary switching circuits for use as a primary and backup protection of power
Fields of application:• power stations and substations;
• industry;
• oil and gas companies;
• public utilities, etc.
Applications:• Low voltage complete devices;
voltage of 0,4 kV and above and recommended for use on the newly introduced and reconstructed objects.
• Cabinets and protection panel lines, transformers, generators, etc;
• transformer substations;
• cell KRU and camera CSR 6 -10 kV (in t.ch. and modernized);
• Switchgear 0,4 kV, etc.
Indication and recording of dataProtection relay shall measure and display the current values of the currents and stresses in the primary or secondary values, the registration of emergency and currents stresses on the issue of indicators and two-line LCD display (For the relay with LCD display) information triggered protections. Values emergency voltages and currents and indication of actuation of protection is stored in nonvolatile memory. Job settings and configuration of the relay runs the control buttons on minidisplee or using a personal computer and special software. Registrar disturbance is recording analog and digital signals.
Recorded the last five alarms parameters of analog and discrete values that can be used to assess the injury and the calculation of switching resource switches. Executing the output relays to disconnect and alarm are freely programmable. Embodiment
Relay run in the universal, with improved performance hull, inside which are different blocks. In relays REJ52_ and REU52_, but LEDs on the front panel has a 2-line 16 character minidispley LCD and 6 buttons. Here is also a port optoelectric converter for connecting a personal computer. At the rear of the relay is a connector for connecting the device to a system of automated control systems (in REJ52_ and REU52), as well as connectors for current transformers, voltage, power supply and relay outputs. There are front and rear performance of the relay with the installation of the rack or on the surface, recessed or Semi-flush mounting.
And installation dimensionsDepending on the selected installation kits relays REJ5xx, REU5xx can be set by type of flush mounting, semi-flush mounted, mounted on a rack or wall mounting. Overall and mounting dimensions are shown in the figure below (dimensions are in millimeters).
Modern RE is characterized by the expansion of the introduction of intelligent methods. Microprocessor electric base allows you to handle an increasing amount of information that allows for simultaneous control of RE relatively large amount of electrical parameters of the regime. This allows you to achieve greater technical excellence of RE, including the proper operation of the above modes.
Completed development of the algorithm of protection from line to line short circuits (short circuit). The main control parameters passed to the next group:
- The nature of the current change in one or more phases (increase or decrease);
- The presence of aperiodic component;
- The derivatives of currents;
- Frequency of the current and the ratio of half—period.
Completes the development of the algorithm (Figure.1), Which allows for the analysis of combinations and ranges of these parameters uniquely identify a short circuit and its parameters (in range or outside it, since the mere fact of a short circuit can be established by simpler methods).
To verify the correctness of the algorithm uses the actual short-circuit oscillograms given in the technical literature.
Preliminary analysis of the results of the recognition algorithm of emergency operation revealed that he correctly identifies the presence of high-frequency signal, aperiodic.
Preliminary analysis of the results of the recognition algorithm of emergency operation revealed that he correctly identifies short-circuit and conducting analysis on all parameters (amplitude, frequency, etc.).
When writing this master of the abstract work is not completed yet. Date of final completion: Dec. 1, 2011 Full text of the work and materials on the subject can be obtained from the author or his / her supervisor after this date.