Lysenko Vasilii Vladimirovich

Faculty: Electrotechnical

Speciality: Electrical power plants

Theme of master's work: Development of the transients scanner-analyzer in a contour of zero sequence of a distributive network 6 кВ power plants

Scientific adviser: associate professor, c.t.s., Nikiforov Andrei Petrovich

Abstract

1. Introduction
2. The theme urgency
3. The work content
4. Conclusion
5. Reference

Introduction

The earth-faults are the most frequent type of damage at the objects of power industry. Their influence on equipment, people’s safety and animals, on the work of system as a whole, defines by the conditions of neutral.
        The conditions of neutral unambiguously defines the means, which can be used for defence or signalization from the monophase earth-faults (MEF). That’s why, there is a non-rare point of view, when the preference is given for conditions, which provide high selectivity of defence action. In particular, this is for conditions of resistive earth of neutral in the switch networks.
        However, the choice of neutral conditions is influenced by the following factors:

• The character, structure of network system and its extension;
• The work conditions of earth devices;
• The potential damage, which can be caused to the equipment;
• The people’s and animal’s safety;
• The providing of regular power supply;
• The value of devices of relay defence and automatic machinery.

        Thus, the choice of the neutral conditions is a multiple-factor problem, which has no one right decision. This is confirmed by the fact, that in the world, in the networks of the different classes of tension there exists a lot of variants of neutral earthing.
        Using of resonance grounding is expediently for rural power supply. These conditions are also defensible, if the lines of electricity transmissions are laid in the settlements, where there is a high possibility of people’s damage by electric current and many different connection lines.

The theme urgency

The defence from the monophase earth-faults (MEF) in the networks 6-35 kW is a burning problem, because nowadays there is no one point of view in the choice of protection devices from MEF, in different types of MEF and in different work conditions of network neutral.
        The main task of this project is development of new device of selective search (SS). The devise is implemented on the microprocessor-based elemental ground. On the first stage, it’s necessary to conduct the analysis of existing decisions of known devices SS (protection devices from MEF). As a rule, all defences work using “the signal”. The device, which is projected, can work both on the disconnection and on the signal.
        The result of the project is multilogic and universal system SS of damaged feeder. The results of work can be used for analysis of transients at any feed systems and with any structure and quantity of engines, generators, systems.

The work content

In the work, it is used the structure- linguistic method of determination of process essence. A method is based on an analogy between the structure of objects and syntax of language. It is considered within the framework of this method, that objects consist of united sub-objects as well as phrases and suggestions are built by connection of words, and words are made from letters. Primary informative sensors form terminal symbols (TS). The aggregate of rules form non-terminal symbols (NTS). On the picture 1, the generalized tree of recognition (or flow diagram) of individual devices SS is shown.

Picture 1 - The generalized tree of recognition devices SS

HFS — high-frequency signal;
        LFS — low-frequency signal;
        MFS — mid-frequency signal;
        PD — the phase detector;
        PWM — pulse-width modulation;
        DOV — the delay one-vibrator;
        B — blocking;
        TE — threshold element;
        P — rule;
        C — grammar.

On the picture 2, the generalized tree of recognition of centralized devices SS.

Picture 2 - The generalized tree of recognition of centralized devices SS

MV — the majority valve;
        SD — the selective device;
        NTS — non-terminal symbol.

An analysis of practical work of different devices SS of the damaged area is in the real terms of network of own needs by tension 6-10 kw shows instability of work of devices. The instability of work is related with the group wearing-out of a few devices, not wearing-out or blocking of devices non-selective wearing-out of devices of damaged and not damaged areas of networks an so on. Also on the stability of work have the influence the cases of absence of clear confirmation of appearance of elemental hasp of isolation of phase on earth by the further expressed change of the mode of network operations.
        Researches of devices of selective search (SS) in CAD (Computer-Aided Design) «OrCAD» with the use of the real high-frequency files shows the presence of instability of devises SS work, which shows up in spite of the fact that devices are perfected both in the plan of increase of number of selectivity rules R_sel and rules of blocking of R_bl. The instability of work is also related with the group wearing-out of a few devices, not wearing-out or blocking of devices non-selective wearing-out of devices of damaged and not damaged areas of networks an so on. Also on the stability of work have the influence the cases of absence of clear confirmation of appearance of elemental hasp of isolation of phase on earth by the further expressed change of the mode of network operations.
        The research show that complication of signal information and variety semantic situations on the entrances of devices SS «early or late» will result to steady work of «main» criteria of selectivity or blocking. Even increase of criteria to two-three substantially does not improve a situation. The construction of devices of centralized SS (CSS) is subject to the same unsteady work. Studying of not achieving of work stability of the devices CSS is much more difficult technically, as they work on the relative method of treatment of information.
        From the known devices in practice large stability of work was shown by devices SS, working on the relative method of comparison of high-frequency constituents of transients in condition that recognition and decision-making about disconnecting of the damaged area is executed by a man.
        The generalized tree of recognition of individual devices SS was made and hierarchical systematization of the known devices of SS was exactly determined by the method of gravimetric coefficients count. The results of analysis are shown in a picture. By analogy with the individual devices of SS the generalized tree of recognition of the centralized devices SS (CSS) was made, and also their hierarchical systematization (in a form of picture and a table). The generalized tree of recognition of terminals and their hierarchical systematization was also made.

Picture 3 – Structure-logical system of suggested device SS

Conclusion

• It is possible to suggest involving in SS devices "additional" informative constituents are in the cases of absence "main" informative constituents, although this suggestion directs the task decision towards "complications" of devices SS.
• Analysis of logical part of "simple" devices SS allowed to show a number of the substantial disadvantages in-process SS devices.
• Problems were shown on providing of decline of recognition risk at functioning of devices SS, synthesized on the basis of methods of surplus of joinings of network, increase of filter properties of entrance co-ordinates 3u0, 3i0, sign and temporal methods.
• The "simple" devices SS after setting in the real network forcedly appear before impossibility of flow diagram steadily to define a current semantic situation, which is differed from "outage".
• Existence of resulting signal was shown about non-clear recognition of the damaged area of CZSN (contour of a zero sequence of network).
• Devices SS, built on the basis of impulsive method, initially being not hundred-per-cent selective, can possibly be perfected further, leaning on the linguistic method of recognition of patterns.

Reference

1. Rules of the device of electroinstallations. – М: Energoatomizdat, 1985. – 640 p.
2. Neklepaev B.N., Kruchkov I.P. Electric part of power stations and substations. — Moscow: Energoatomizdat, 1989. — 490 p.
3. Nikiforov A.P. The protection and management, soluble terminal circuit zero sequence network/ PIHE “Donetsk National Technical University”// “Lviv Polytechnic”. — № 637. — 2009.
4. Nikiforov A.P. The choice between the “simple” and “advanced” designs, forming an object of management and protection, structural-linguistic method// Journal of Kremenchug State Polytechnic University Michael Ostrogradskii. — № 3 (56). — Part 2. — 2009.
5. Ivanov I.A / Abstracts// The development of selective actions relative to the needs of networks of power based on a comparison of bit parts. - PIHE “Donetsk National Technical University”. – 2009.
6. Petrov E.A. the Programmable controllers. Standard languages and adopting the applied planning // A publ. Solon-Press. 2004.
7. Sivokobylenko V.F., Lebedev V.K. Transient processes in electrical power systems, auxiliary power (manual). DonNTU, Donetsk – 2002 – 136 p.
8. Circular Ц-01-88. On improving the reliability of networks of 6 kV auxiliary nuclear power plant. - M., 1988. – 7 p.
9. Chernobrovov N.V. Relay Protection/ Manual. — Moscow. — Energy.
10. A.F. D'yakov, N.I. Ovcharenko Microprocessor relay protection and automation of electric power systems.