1. Introduction. Rationale for the relevance of the theme
2. Anticipated goals and objectives of the study
4. A review of research and development on
4.2 National review (in Ukraine)
List of publications and materials on the final work
The functions of identifying and automatic shut-off of damaged electrical equipment, as well as identifying abnormal modes of electrical equipment (eg, overload of the transformer) Perform relay protection and automatics (RPA). The main performance properties of relay protection - technical excellence (which includes the selectivity and stability of operation) and operational reliability. However, in some modes, it can not function, ie false work, or refuse to act. One of these regimes, as practice shows, is the saturation of current transformers aperiodic component of short circuit current, which leads to strong distortion coming in the relay of information [1].
Every year the tougher requirements for quality electricity supply to consumers and accordingly - increasing requirements for relay protection of power systems. One solution to this problem is to extend the application of microprocessor relay protection. 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 status of the object. This allows you to achieve greater technical perfection of relay protection, including the proper operation of the above mentioned mode [2].
Figure 1 shows the waveform of the secondary current and the magnetizing current of current transformer when it is saturated with the aperiodic component. Physically, this phenomenon is the accumulation of magnetic flux in the core of current transformer, since there is no or reduced half-wave polarity, which in normal conditions, reversing the core [4].
Aperiodic component of the primary current, appearing in the transient regimes are transformed into the secondary circuit of current transformer in order to more error than they decay slowly. Consequently, with increasing decay time increasing proportion of the aperiodic component of the primary current is spent on the magnetization of the magnetic current transformer. Thus, it follows from Figure 1, despite the small amount of current that the maximum does not exceed three values of the nominal secondary current, the transformer went into saturation mode. Saturation of current transformer aperiodic component, as noted above, leads to a deterioration of the protection relay. Currently, there are already current transformers, which are not saturated, but their widespread use is not yet possible. Consequently, for a long time to be used electromagnetic current transformer, which makes the actual development of protections that would ensure proper operation in this mode (switching time less than 10ms) [3].
The aim is to develop algorithms RE, which will determine the damages, regardless of the saturation of current transformers and increase reliability of relay protection.
Research objectives:
• Analyze taken into consideration the control group of parameters that characterize the transition process;
• develop an algorithm to identify damage to the parameters of the transition process;
• implement the algorithm in the programming language Visual C ++.
Scientific novelty of this paper is to develop a new principle of construction of relay protection against damage to electrical equipment, which allows to determine the damage to electrical equipment on the basis of the analysis simultaneously several emergency settings (the nature of the current change, the presence of the aperiodic component, the period and the current frequency, etc.). The developed program can be used in carrying out practical work on discipline "of microprocessor relay protection. Report on work presented at the Ukrainian Student Scientific Conference "Electrical and Electromechanical Systems" (Sevastopol, 2011).
Similar studies were conducted at the Department of Applied Mathematics and Informatics years earlier. In particular, the student Kolesnik AV
developed a distributed system for automatic recognition of images in real time. The topic of his master's work sounded like, "Distributed software system for image
recognition, supervisor Associate Professor, Ph.D. Ladyzhenskii Y. The novelty of this work was to develop algorithms for face recognition based on the anthropometric
characteristics of persons who can operate in real time on low-contrast images.
4.2 National Review (in Ukraine)
Ukraine has also conducted similar studies related to pattern recognition based on analysis of relevant parameters.
Prof. Chuvash State University, IN Ulyanov Lyamets UY wrote a series of articles devoted to the recognition of states of emergency facilities. Namely, the "Perspective methods and means of recognition of states of emergency power systems (Lyamets Y.Y., Nudelman G.S., Pavlov S.A.) [5]," Recognition of the damage to power transmission. Part 1. Recognition of the injury. P.2. Common questions of recognition of damaged phase. Part 3. Recognition of the line to line short circuits (Lyamets Y.Y., Nudelman G.S., Pavlov S.A., Efimov, E.B., Zakonyshek Ya) [6-8] and many others.
Organization of the United States is ELEKS software developer program DAKAR (Interactive automated complex analysis mode), which is designed to calculate and analyze the steady state and transient power systems.
Interactive automated complex analysis modes (Dakar) is designed to calculate and analyze the steady-normal boundary and post-emergency modes of operation of electrical systems voltage 0,4-1150 kV electromechanical transients (stability analysis) of electric power systems, taking into account the actions of any automated devices, the reaction thermal equipment power station.
As part of complex information support is an information database (IDB) and software (PS) work with it. The information base consists of data on the electric circuit network and its modes, and power equipment, and reference information.
In the complex DAKAR provides links to other programs (or users) via the import / export data from: the old DOS-version DAKAR, CDA format (for programs in Ukraine and Russia), format UCTE DEF (Europe) format XML.
DAKAR complex following tasks:
- Calculation and analysis of steady-state regimes;
- Equivalenting mains;
- Creation of graphical network diagrams and wiring diagrams of substations, with playback on their calculation results;
- Study of static and dynamic stability modes of EPS;
- Analysis of long-term transients;
- Analysis of asymmetric, nepolnofaznyh modes and calculation of short circuit currents.
Users DAKAR complex in Ukraine are:
• GP "Ukrenergo" "Western Electric Power System", Lviv;
• CJSC "Institute "Ukrzahidenergoproekt", Lviv;
• OJSC EC "Odessaoblenergo", Odessa;
• OJSC EC "Zakarpateoblenergo", Uzhgorod;
• OOO "Kiev Energy Construction Company", Kiev [9].
In connection with the development of the algorithm is executed on the protection line to line short circuits (short circuit). The algorithm is based on an analysis of simultaneous multiple emergency settings:
- the nature of the current change in one or more phases (increaseor decrease);
- the presence of the aperiodic component in the currents;
- ranges of values of derivatives of currents;
- frequency of the current and the ratio of the durations of adjacent half-cycles.
Figure 2 shows the algorithm for the recognition of emergency operation, which allows you to uniquely identify a short circuit and its parameters are based on an analysis of combinations and ranges of emergency options outlined earlier. This algorithm includes a large number of subroutines that analyze the parameters that characterize the transition process.
One of these routines is shown in Figure 3. This algorithm for determining the form of a short circuit. It allows you to determine whether a short circuit, and his view by comparing the phase currents from the current setpoint.
Figure 4 shows the algorithm for determining the period and frequency. The input parameter is an array of numbers, describing the sinusoidal signal i (t). When alternately multiplying the previous value and then store the sign. Once you change the sign twice, displays the value of the period. Current frequency is defined as the reciprocal of the period.
In the next Fig.5 detection algorithm aperiodic component, which is based on a comparison of two adjacent half-cycles. We first calculated the half-periods (one crossing '0 '), then alternately compare the neighboring half-cycles. If they are not equal, is checking that the values of the amplitudes (maximum current). After that, we can conclude that there aperiodic component in the current.
All these algorithms are implemented in the programming language C ++. Figure 6 shows the results of the identification of 3-phase short circuit.
To verify the correctness of the algorithm uses the actual short-circuit oscillograms given in the technical literature.
Preliminary analysis of the algorithm showed that it can correctly identify the three-phase short circuits.
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 her supervisor after this date.