How to know the strum of a short chirp
The electric stingray puffed its tail low and died in a short chirp.
It has become food for our reader, what is it short chirp and how to know yoga? Well, well, on a good supply, we can try to give an opinion.
Let's take a look at the simplest lance that is made up of light bulbs and, for example, a car battery:
A stream flows along the lance along the darts and a light bulb starts to burn. Everything is simple.
Let's assume that our darts, like leading to a light bulb, are absolutely bare and raptly, like a diva on the wiring, one more such naked wire is lying. This posting locks our two bare wires. The І axis begins with the naytsіkavіshe - at the scheme vinikaє short chime (short circuit). Short zamikannya - the shortest path for the passage of an electric strum with a lancet, de least opir.
Now the strum is flowing with a light bulb and wiring. Ale, we have a smaller opir, a lower opir of a light bulb, and may the whole strum flow there, a smaller opir - tobto for wiring. Oskіlki opіr our wiring is already small, those strums are already flowing even more great, according to Ohm's Law. And if a great strum flows, then a lot of heat, which will be carried out by wiring, will be even greater, according to the Joule-Lenz Law. Zreshtoy according to the lance, what a vision of chervonim, the great strum will flow and the wines will be very warm. So much that you can navit pozhezha.
You chanted more than once at the news, which became hotter after a short flicker. In this case, the exposure of the conductor of the phase in some place begins to expose the conductor of zero. Basically short circuit in living booths to look like an old cable, which is cracking at the seams in a kind of handy slip and water, as you can spend on a cable. Ale is also a human factor. Tse, zvichayno, nedotrimannya zahodіv safe when koristuvannya electric jet.
When designing a be-like energy system and specially prepared electrical engineers for additional technical data, tables, graphs and computer programs, analyze the operation of the circuit in different modes, including:
1. idle run;
2. nominal value;
3. Emergency situations.
I especially need to become a third step, if inaccuracies are blamed in the measure, it can be a bad possession. Most of the stench is due to the "metal" short-circuiting of the lances of life, if between different potentials the voltages are connected by a vipadkovy rank of electrical support to the rozmirnistyu in the Ohm's parts.
These modes are called short flashes or short short circuits. Blame it on:
failures in robotic automation and protection;
pardons for service personnel;
poshkodzhennya possession through technical old;
elemental splashes of natural phenomena;
sabotage or diversification of vandals.
A stream of short flickers for its magnitude significantly change the nominal voltage, as the electrical circuit is being created. That's why the stench just vipalyuyut weak months in the setting, ruining yoga, crying out after.
The cream of the thermal ruining still stinks of a dynamic day. Yogo showing good showing a video clip:
To turn off the development of such accidents during operation, start fighting them at the stage of project development. electric power supply. Therefore, theoretically calculate the possibility of accumulating short streaks of that magnitude.
These data are victorious for the further development of the project and the choice of power elements and zahisnih outbuildings schemes. They continue to work constantly and during the operation of the possession.
A stream of possible short chimes can be developed using theoretical methods lower level accuracy, admissible for the superficial creation of zahistu.
Yakі elektrichnі protsesі zakladіvі in the basis of rozrahunka strumіv short zamikannya
We pay attention to the fact that whether there is any kind of applied voltage, including constant, changing sinusoidal, pulsed, or whether it is otherwise, creating a stream of accidents, like repeating the image of the form or changing the fallow in the application All the same, you have to tell the designers and get it in their rozrakhunkas.
The assessment of the vindication of m dії strumіv of short zamikans is allowed by vikonati:
Ohm's law;
the magnitude of the force characteristics of tension, which is applied in the presence of a voltage;
vicorist structure electrical circuits electrical installations;
the value of the newly applied support to the dzherel.
Follow Ohm's law
As a basis for the development of short chimes, the principle is taken, which means that the strength of the struma can be calculated according to the magnitude of the applied voltage, so that it can be added to the value of the connected support.
Vіn dіє і at rozrahunku nomіnalnyh navantazhen. The only difference is that:
under the hour of the optimal robotic electrical circuit, the voltage and opir are practically stabilized and change insignificantly within the boundaries of working technical standards;
in case of accidents, the process is spontaneously reversed. Ale can be rebatched, shriveled with fragmented methods.
Tension caused tension
Z її to help evaluate the power energy feasibility of the construction of the ruinous robot with short strums, analyze the trivality of the current flow, the magnitude.
We can look at the butt, if that same shmatok honey dart with a span of five square millimeters and a long pіvmeter, the spigot was connected directly to the terminal of the Krona battery, and after an hour they were inserted into the contacts of the phase and zero of the butt socket.
At the first drop, through the wire, the voltage was flowing, a stream of short flickering, which would loosen the battery to such an extent that I would mess up the practice. The tightness of the dzherel is not to stick on those who want to burn the plugged-in jumper and tear the lance.
Ask another person automatic zahistu. It is acceptable that the stench is wrong and jammed. Todi strum short zamikannya pass through home wiring, reach the entrance shield to the apartment redundant lines power transmission lines to the transformer substation, to live.
At the result, to the winding of the transformer, it is connected to carry out a long line with a large number of wires, cables and that part of the day. The stench means to increase electric opir our short. Ale navіt vіpadku vіpadku ymovіrnіst that, scho won't show the applied pressure and just burn.
Schematic configuration
Under the hour of eating, the people are fed up to them different ways, for example:
through the potentials of the positive and negative windings of the constant voltage;
phase and zero single-phase per-butovoe metering 220 volts;
three-phase circuit 0.4 kV.
In the dermal s tsikh vipadkіv may be damaged isolation different places What will I bring to the passage through them of the stream of a short zamikannya. Tіlki for triphasic lanceug zminnogo struma can be short zamikannya mіzh:
usima trioma phases at the same time are called three-phase;
two be-like phases between each other;
whether it be a phase and zero - single-phase;
phase and earth - single-phase to earth;
two phases, that earth - two-phase to earth;
three phases and the earth - three phases to the ground.
When creating the project of electricity supply, the possession of all the modes is necessary to prorahuvati and vrahuvati.
Injection of the electric support of the lanceug
The length of the main line in the direction of the voltage supply until the moment of the short circuit is fixed may be the first electric opir. This value is between the streams of a short chirp. The presence of the windings of transformers, chokes, coils, capacitor plates is supplemented with inductive and electrical supports, which form aperiodic warehouses, which create a symmetrical shape of the main harmonics.
Known methods of rozrahunka strumov short zamikannya allow you to calculate them with sufficient accuracy for practice, for a long time prepared information. The real electrical opir of the already selected circuit can be measured according to the methodology. Vono allows you to clarify the rozrahunok, to make corrections for the selection of the defense.
Basic Documents
1. Methodology
Won good vikladena at the book of A. V. Belyaev "Selection of equipment, protection and cables for 0.4 kV rails", published by Energoatomizdat in 1988. Loan information covers 171 sides.
The book hopes:
sequence of rozrahunka strumiv KZ;
the appearance of a streamlined dielectric arc at the place of adoption;
principles of choice zahisnoy equipment for the values of the strums.
The book is published Dovidkova information on:
automatic vimikach and zapobіzhnikam with the analysis of the characteristics of their own powers;
selection of cables and equipment, including installations for the protection of electric motors, power folding, entry buildings generators and transformers;
nedolіkіv zakhistu okremih species automatic vimics;
specificity of the zastosuvannya of wine relay protections;
apply the verse of the design tasks.
2. Install RD 153-34.0-20.527-98
This document is displayed:
methods of rozrahunkiv strumiv symmetrical ta asymmetric modes in electrical installations with a voltage up to 1 kV;
methods for converting electrical devices and conductors to thermal and electrodynamic stability;
methods for testing the switching capability of electrical devices
Vkazіvki not ohoplyuyut rozrahunka strumіv KZ hundredovno pristroїv RZA zі specific minds of exploitation.
3. GOST 28249-93
The document describes the short circuits that are blamed on the electrical installations of the blast jet and the method of re-roofing for systems with a voltage of up to 1 kV. Vіn dіє z 1 sіchnya 1995 fate on the teren of Belarus, Kyrgyzstan. Moldova, Russia, Tajikistan, Turkmenistan and Ukraine.
The state standard establishes the main methods of rozrahunkiv strumiv kz at the beginning and whether there is a certain time for electrical installations from synchronous and asynchronous machines, reactors and transformers, repeating and cable power transmission lines, bus ducts, folding complex navnazhennia nodes.
Technical standards for the design of electrical installations are determined by official state standards and approved by the International Council of Powers for standardization, metrology, certification.
Blackness of the projector for the rozrahunka of the strum_v of a short zamikannya
The next step is to prepare the necessary for the analysis of the output, and then we will carry out a survey. After the installation, the possession before the process of putting yoga into operation, and during operation, the correctness of the choice and the rightness of the process are changed.
Selection of holidays
Whether or not the scheme can be brought to a simple view, if it is made up of two parts:
1. dzherelo naprugi. For a 0.4 kV line, the role is victorious secondary winding power transformer;
2. lifeline power lines.
Under them, the needs of power are chosen.
Transformer data for rozrahunka strum_v
It is necessary to say:
the magnitude of the short-circuit voltage (%) - Ukz;
spend a short zamikannya (kW) - Rk;
rated voltage on the windings of the high and low sides (kV. V) - Uvn, Unn;
phase voltage on the winding of the low side (B) - Eph;
nominal pressure (kVA) - Snt;
povniy opir strum single-phase short circuit (mOhm) - Zt.
Data of lifeline for rozrahunka strumiv KZ
Before them one can see:
brands and number of cables from the designated material and wire cut;
zagalna dozhina trasi (m) - L;
inductive opir (mOhm/m) - X0;
the last reference for the phase-zero loop (mOhm / m) - Zpt.
Tsі vіdomosti for the transformer and lines zoseredzhenі at dovіdniki. In the same place, take the shock coefficient Kud.
Sequence of the rozrahunka
For the known characteristics, calculate for:
transformer - active and inductive opir (mOhm) - Rt, Xt;
lines - active, inductive and top opir (mOhm).
three-phase mic and shock (kA);
single-phase short circuit (kA).
For the values of the rest of the calculations, the strums and pick up automatic vimikachi and other facilities for caregivers.
Razrahunok strumov short zamikannya designers can vykonuvat manually for formulas, dovidkovymi tables and graphs, or for help of special computer programs.
On a real power plant, put into operation, all streams, including nominal and short flickers, are recorded by automatic oscilloscopes.
Such oscillograms make it possible to analyze the breakdown of emergency modes, the correctness of the work of the power control and the protection of the outbuildings. According to them, you can come in to improve the reliability of robots and save electrical circuits.
What is such a short hum and through what short hums are heard
Short flicker in electrical wiring most often they penetrate through the damage to the insulation of the streak-conducting parts, in the wake of mechanical failure, old age, infusion of water and aggressive media, as well as the wrong kind of people. Have a different vindication short hum grows, and the amount of warmth that is seen, as it seems, is proportional to the square of the stream. So, as short flicker the strum increases by 20 times, then the amount of heat that is seen at the same time, the growth is approximately 400 times.
Thermal injection on wire insulation drastically reduce mechanical and electrical power. For example, as a conductor of electric cardboard (as insulation material) at 20 ° C taken as one, then at temperatures of 30, 40 and 50 ° C it will increase by 4, 13 and 37 times in the same way. The thermal old insulation is most often blamed for the overweighing of electric lines by strums, which is long overdue for this kind of conductors. For example, for cables with paper insulation, the term of the service can be used according to the “eight-degree rule”: the temperature on the skin is 8 °C, the term of the service of insulation is shortened by 2 times. Thermal polishing is also provided by polymeric insulating materials.
Injection of water and aggressive media on the insulation of wires istotno pogrіrshuє її camp through the appearance of the surface streams of the turn. In the form of heat, which at the same time, the homeland evaporates, and traces of salt are overfilled on the insulation. When pinned viparovuvannya strum coil znikaє. In case of repeated injection of water, the process is repeated, but through the increase in the concentration of salt, the conductivity increases, so that the strum coil does not attach after the completion of the vaporization. Moreover, there are more sparks. Nadalі pіd dієyu struma turn іzolyatsіya vvugluєєє, vtrachaє mіtsnіst, scho mozhe bring to viniknennya mіstsevy arc surface discharge, zdatnogo slаkhnutієі isolation.
Fire alarm characterized by offensive possible manifestations electric jet: ignition of insulation of wires and other combustible objects and speeches; zdatnistyu іzolyatsії provіv poshiryuvati gor_nnya pіd h її її vіd tehnіh dzherel zapalennya; with a short zamikannі razmeltnih metal particles, sho podpalyuyut otochuyuchi combustible materials (shvidkіst razloto molten metal particles can reach 11 m / s, yakі temperature - 2050-2700 ° C).
When rewiring electrical wiring the emergency mode is also activated. Through the wrong choice, the inclusion of a slow down stream, which passes at the wires, exceeds the nominal value, so that the increase in the width of the stream (overweighing) is made. For example, when passing a struma of 40 A through successively three pieces of darts of the same length, aloe vera cut - 10; 4 and 1 mm2 width of yoga will be: 4, 10 and 40 A / mm2. In the rest of the shmatka, there is a streak, and, obviously, there are tightness. The wire with a span of 10 mm2 is slightly heated, the temperature of the core of 4 mm2 is within acceptable limits, and the insulation of the core with a span of 1 mm2 is simply burned.
Chim strum short zamikannya vіdznyaєtsya vіd strum navantazhennia
The main effect of a short circuit in the appearance believe in what short flicker Insulation damage is the cause of the emergency mode, and in case of overweighing - it is a last resort. For the first conditions, the rewiring of wires and cables at the connection with a greater emergency mode is more fire-safe, less short-term.
The material was wired, and it directly flows into the zapalyuvalny building during re-witching. Porіvnyannja pokaznіnіv pozhezhnї nezbezpeka wires of the APV and PV brands, taken off during testing in the mode of navantage, showing that the ability to take insulation in the wires with the middle streak-conducting conductors is higher, lower in aluminum.
With a short circuit that very regularity is guarded. Propalyuyucha building of arc discharges near lansyugs with medium streak-conducting veins of high, lower with veins of aluminum. For example, steel pipe with commissar walls 2.8 mm are removed (otherwise combustible material is spalled on the surface) with aluminum 16 mm2, and with a copper core - with 6 mm2.
The multiplicity of the struma is due to the short strumming struma, or the transition to a trival struma for a given wire cut.
the largest pozhozhnoy unsafe you can conduct cables with a polyethylene sheath, as well as polyethylene pipes when laying cables in them. Electrical wiring in polyethylene pipes near the fireside becomes more trouble, lower electrical wiring in vinyl plastic pipes, to which the area of polyethylene pipe congestion is signifi- cantly higher. Particularly unsafe is the need for private living booths, de, as a rule, in the same measure, all live happily ever after, and the aparati often zahistu often during the day, or it’s more than risked for a stream of a short zamikannya. In richly-topped living houses, it is also not possible for the bags to be covered with dimmed lamps or turn on butovі electrical appliances with a greater sweating, lower than that, like a loosened mesh.
On electrical installations(sockets, vimikachs, cartridges too) indicate the boundary values of strums, voltages, tensions, and on zatskachs, roses and other types, moreover, the largest cuts of conductors that come. For a safe vikoristannya tsikh outbuildings, it is necessary to decipher these inscriptions.
For example, 6.3 A is applied to vimicac; 250 V", on cartridge - "4 A; 250; 300 W ”, and on the bottom-rozgaluzhuvach -“ 250 V; 6.3 A, 220 V. 1300 W, 127 V, 700 W. "6.3 A" is ahead of those that strum, which pass through the vimikach, is not guilty of overheating 6.3 A, otherwise the vimikach will overheat. For a smaller strum, a vimikach is suitable, for which there is less strum, the contact heats up less. Write "250" to indicate that the vimikach can be stuck in the strings with a voltage no higher than 250 V.
If you multiply 4 A by 250, then you get 1000, not 300 watts. How to calculate the value from the letter? Need to get out of tightness. With a pressure in the measure 220 admissible strums: 1.3 A (300:220); at a pressure of 127 - 2.3 A (300-127). Current 4 And the voltage is 75 (300:4). Write “250 V; 6.3 A" indicates that the application for the voltage is not more than 250 V and for the struma is not more than 6.3 A. Multiplying 6.3 A by 220 V, we will take 1386 W (rounded 1300 W). Multiplying 6.3 A by 127, we get 799 W (rounded up to 700 W). Blame food: why is it so unsafe to round up? Not unsafe, the shards were rounded off, but the value of tightness was less. If the pressure is less, then the contacts are heated less.
When leaking through the contact of the electric jet through the transitional support on the contact, the voltage drops, tension and energy is seen, as a result of the heating of the contacts. Above the world, increase the struma in the lance, or increase the support leading to a further increase in temperature, and contact that wire, which to supply, which I can call out.
In electrical installations, there are unresolved contacts(soldering, zvaryuvannya) and roses (on twine, vtichnі, spring thin), as well as contacts of switching devices - magnetic starters, relays, switches and other devices, specially designed for switching and switching off electrical switches, for their switching. At the borders of the internal supply of electricity, the input to the supply of electricity flows through a large number of contact circuits.
Contact details are not at fault, for the daily conditions are not at fault. However, the investigations carried out some time ago over the possessions of the inner workings showed that only 50% of the contacts were satisfied with the DSTU. When the struma flows through the struma in a non-acidic contact contact, for one hour, a significant amount of heat is seen, proportional to the square of the struma (width of the struma) and the support point of the effective contact to the contact.
If the contacts are sticking with combustible materials, then they can be ignited or scorched and ignited by the insulation of the wires.
AT size of transitional contact support lie in the thickness of the struma, the strength of the compression of contacts (the size of the support area), in the material, from which stench is prepared, the degree of oxidation of the contact surfaces is thin.
To change the width of the strum in contact(Other, and temperature) it is necessary to increase the area of the contact dot. As soon as the contact surfaces are squeezed one to one with such force, the small humpbacks in the areas of torsion will be a trifle of winter. Through it, the expansion of the elementary maidanchiks, which stick together, and the additions of the maidan maidanchiks appear, and the width of the struma, the transitional opir and the heating of the contact decrease. Experimental research showed that between the support of the contact and the magnitude of the torque (force of compression) it is wrapped proportionally. To change the moment to turn, by 2 times the contact wire of the APV with a span of 4 mm2 or two wires with a span of 2.5 mm2 is increased by 4-5 times.
For the introduction of heat from contacts and the rise of yoga in in the middle prepare the contacts of the foam mass and the surface cooling. Particular respect is given to the areas of wiring and connecting them to the contacts of the incoming outbuildings of electrical appliances. On the known ends of the wires, zastosovuyte tips of different shapes and special zatiskakh. The reliability of the contact is ensured by special washers, which are springy and with the sides. After 3-3.5 years, the contact is increased approximately 2 times. Significantly increase the number of contacts and with a short zamakanny after a short periodical injection of the struma on the contact. Testing showed that the greatest stability during injection unfriendly factors Mayutnі z'єdnannya with spring spring washers.
Unfortunately, "economy on pucks" is a wider sight. The washer can be made from colored metal, for example, from brass. The steel washer is protected with anti-corrosion coating.
Be it a person, whose work is connected with the maintenance of electrical engineering, you already know better about those inacceptability, as if you have a short chime (k.z.). Some people care that it’s out of the question. Tse not so. A short hiccup is the whole process, otherwise, as always, the emergency mode of the robot, whether it be a plant of an electrical installation. And the axis of the trace of yoga is right to lead to the worst. Zagalnopriynyat vyznachennya to say: “A short zamikannya - tse without a middle z'ednannya two or more dots that lead to life's potential. Є abnormal (not overflowing) robotic mode.
In order to understand what you yourself see in the language at that moment, if you blame it for a short time, it is necessary to guess the principles of the functioning of the elements of the circuit. Let's imagine the simplest lance, which is made up of two conductors and that need (for example, light bulbs). In the great minds of the conductor, there are directings of the charge of elementary particles, which are mindful with the constant infusion of the dzherel. The stench is moving from one pole of the dzherel to the other, through two log cabins and a lamp. Obviously, the lamp vibrates the light, so that the particles wink at her singing robot.
With a direct turn, it is constantly changing, but at the same time it is important. The number of electronics, which can be passed by a songful lot of a lancet in one hour, is separated by a lamp support, conductors, an EPC dzherel. In other words, the strum does not grow indefinitely, but supports the regime that it has established itself.
Ale z for some reason, the isolation on the lances of the lancer is being removed. For example, the lamp was flooded with water. And here її change. As a result, the strum, which is flowing along the contour, is surrounded by a total support of the living room, wires and a water "isthmus" on the lamp. Ring out the sum of the pavement is miserable, which is not insured by the rozrachunkas (blanks to establish specialization of the calculation).
The subsum is practically inexhaustible growth of the struma, which follows the classical Ohm's law. At times, the tightness of a short chirp is often predicted. It depends on the boundary values of the electric strum, which you can see was alive until the end of the fret. Before speech, it is protected from wiring (short-circuiting) the battery contacts.
Although in the butt we can see the support of the lamp from the lancet after falling on it, there are no reasons for the short flicker. For example, if you talk about the scheme itself, then k.z. so you can blame, as if the insulation would be destroyed, if only one dart and wine would stick out of the ground. At this point, the strum looked like a life-giving place on the path of the smallest support, that’s into the ground, which is a great power. Ushkodzhennya іzolyatsії vіdrazu dvoh provіvіv і їх dotik prizvedi until the same result.
The foregoing can be said: kz can be from the earth and without it. On the processes that are being vіdbuvayutsya, tse do not spit.
About yakі w ushkodzhennya was on the cob statti? As you can see, the greater the value of the struma, which flows through the lot of the lansyug, it is more heated. For sufficient tightness, she was dzherel at short circuit. deyakі dіlyanki lansyug just burn out, transforming into a medium saw (for the medium elements).
Zakhist in the form of a short zamikannya is simple and effective. Notifications about the collapse through fading are blamed, first for everything, through the wrong choice of parameters of the devices, the wrong selectivity. If you go about a 220 V butt lance, then stop them with an overworld growth of the struma electromagnetic rozchipluvach, which is found in the middle, opens the lance.
An electric lance is called an electric circuit, like a leak. Lantsyug can be folded, for example, from batteries, to live a light bulb, or from impersonal elements, built up among themselves, for example, at your computer. The lancet can be stacked with an uncircumscribed number of elements and the strum must be entered at one contact on the ear of the lancet and exit at one contact into the terminal of the lancet.
For proof:
A lot of people are called shaving lansyug - short zamikannyam. It is necessary to clearly understand how to shortly mute the essence of the places (bridging) for passing the stream by the shortest path at the mіstsі zamikannya, bypassing some of the elements of everything electric lansyug.
Ring a short chirp, maybe even a small opir - tse lead up to the great struma from the zherel of life (you can bring yoga out of tune). In order to carry out life without interruption, it’s possible to burn out with the mass (a possible option is to stop, plus or minus the life’s death), sound the burnout, and if there is no yoga, then it can burn the life’s death. Tse short flicker.
As soon as it merges and ceases to work again, if you collapse the elements of the lancet, the price is called the shave of the lancet and the shave is taken off by itself at that moment, if the attachment is not processed. So the strum does not flow, and the lance does not work.
Ruh strumu and ruh electron in the lancets of a post-strumu
On the image you can see how it works electric strum and how electrons collapse. As you can remember, electronics collapse from a minus (negative contact of the living life) to a plus (positive contact). So the electric strum really collapses. For a great part of the hour, people appreciated that the positively charged particles were carrying the charge, and then, the stench of the guilt was collapsing from positive to negative contact. So ring out your normal flow. If it is easier for you to show that the strum is flowing from plus to minus, then there is nothing terrible in it, without changing the essence of the process.
The Lanziugs change strum, The polarity of the struma is constantly changing, so in such a lance the electrons collapse like a straight line, and in a reverse direction. In other articles on our site, we will talk about the constant and the changing strum.
