Yake recognition of a neutral droth in a three-phase system. Neutral wire
For rozrahunku triphasic lanceug zastosovnі all methods that are vicorous for rozrahunka linear lances. Sound the support of the wires and the internal support of the generator is less than the supports of the receivers, so it is easier to build such lances (as it does not require great accuracy), the support of the wires can be fixed (Z L \u003d 0, Z N \u003d 0). The same phase voltages of the receiver U a , U b і U c will be equal to the phase voltage of the electric power supply (generator or secondary winding transformer), then U a = U A; U b = U B; Uc=UC. How many more complex supports of the phases of the priming Z a = Z b= Z c currents in the skin phase can be determined by the formulas
İ a = Ú a / Z a; İ b = Ú b / Z b; İ c = Ú c / Z c.
Vidpovidno to the first law of Kirchhoff strum at a neutral dart
İ N = İ a + İ b + İ c = İ A + İ B + İ C .
Phase voltage - vinikaє between the cob and the end of the phase. Otherwise, it is important to determine how the voltage is between one of the phase wires and the neutral wire.
Linear - yak vyznachayut sche yak interfazne or interfazne - vinikaє between two wires or the same vysnovkami different phases.
At the end of the life of the tricutnik (Fig. 3.12), the end X of one phase is connected with the ear of the other phase, the end of Y of the other phase is with the ear of the third phase, the end of the third phase Z is with the ear of the first phase A. The ear A, B i From the phases, three darts are connected for help to the primaries.
Z'ednannya phases of the dzherel in the closures of the trikutnik can be done with symmetrical system EPC, shards
A + B + C = 0.
Yakshcho zadnannya windings trikutnik incorrectly vikonano, tobto. at one point connects the ends or the cob of two phases, the total EPC in the circuit of the tricutnik winds up at zero and a great stream flows through the windings. Tse emergency mode for life is unacceptable.
The voltage between the end and the cob of the phase when connected with a tricot is the same as the voltage between the line wires. To that, when z'ednanny trikutnik line voltage dovnyuє phase vpruzі.
As an unreliable support for the line wires, the line voltage of the lifeline can be compared to the line voltage of the life line: U ab = U AB , U bc = U BC , U ca = U CA . Behind the phases Z ab , Z bc , Z ca phase strumsİ ab, İ bc ta İ ca. Smart positive direction of the phase voltage Ú ab , Ú bc and Ú ca phase streams. Smart positive direct line streamsİ A , İ B and İ C accepted as a life expectancy before the adoption.
On the vіdmіnu vіd z'єdnannya zіrkoy vіdnіnі strikutnikom, phase strumi not equal liniynym. Strumi at the phases of the match are assigned to the formulas
İ ab = Ú ab / Z ab; İ bc = Ú bc / Z bc; İ ca = Ú ca / Z ca.
Linear streams can be assigned to the phase ones, aligning with the first Kirchhoff law for knots a, b and c (Fig. 3.12)
The left and right parts of the equal system, (3.20), are taken
İ A + İ B + İ C = 0,
tobto. the sum of complexes of linear streams is equal to zero for symmetrical, so for not more symmetrical.
When connecting the phases of the winding of the generator (or transformer) X, Yі Z go to one sleeping point N, which is called a neutral point (above a neutral point) (Fig. 3.6). End phases of priming ( Z a, Zb, Zc) also go to one point n. Such a day is called a day of zirka.
Provide A−a, B−bі C−c, which start the cob of the phases of the generator and the primach, are called linear, N−n, what is the starting point N generator with dot n priymacha, - neutral.
A triphasic lansyug with a neutral droth will be chotiric, without a neutral droth it will be tripartite.
In three-phase lances, phase and linear voltages are distinguished. phase voltage U F - the voltage between the cob and the end of the phase or between the linear dart and the neutral ( U A, U B, U C at the dzherel; U a, Ub, U c at the receiver). If you can support the wires with a support, then the phase voltage in the receiver is vvazhayut such themselves, like in the dzherel. ( U A=U a, U B=Ub, U C=U c). For the mentally positive direc- tions of the phase voltage, the direc- tions in the cob up to the end of the phases are taken.
Line voltage ( U L) - voltage between line wires or between single-layer windings of different phases ( U AB, U BC, UCA). Mentally positive directions of the linear voltages are taken from a point that corresponds to the first index to a point that corresponds to another index (Fig. 3.6).
By analogy with the phase and line voltages, the phase lines are also distinguished linear streams:
Phazni ( I F) - ce strums at the phases of the generator and priymachiv.
Linear ( I L) - strumi in linear droths.
50. Understand about asymmetric modes work in tripartite and chotiriprovid lancers. Appointment of a zero dart.
Triprovidny lanceug
In a steep slope with asymmetric vanishing Z ab ≠ Z bc ≠ Z ca. Sound out blaming when eating food three-phase mesh single-phase receivers. For example, for the purpose, fig. 3.15, the phases of strumi, kuti zsuvu phases and phasic tension will be different in the wild phase.
Vector diagram for vipadku, if phase ab є more active, In the bc phase it is active-inductive, and in the ca phase it is actively-dismissive induced in fig. 3.16 topographic diagram - in fig. 3.17.
Pobudov’s vectors
İ A = İ ab-İ ca; İ B = İ bc - İ ab; İ C = İ ca - İ bc.
In this way, with a non-symmetric navantage symmetry of the phase streams ab, b, ca is destroyed, then the linear streams A, B, C can be assigned only a rozrachunk for the vision-guided lines (3.20) or a graphic path with vector diagrams (Fig. 3.16, 3.16, 3.16).
An important feature of the phases priming with a tricot is those that, when changing the support of one of the phases, the operating mode of the other phases is left unchanged, because the linear voltage of the generator is constant. Change only the stream of this phase and the line stream at the wires of the line, connected with the phase cycle. To this reason, the scheme of the tricoutnik is widely used for the inclusion of a non-symmetrical vanity.
When expanding for asymmetric navantage, the values of the phase streams ab , bc , ca and the disruption of the phases ab , bc , ca are assigned to the cob. Then we assign linear streams for additional lines (3.20) for complex forms or for additional vector diagrams
Chotiriprovidny lansyug
With a symmetrical system, the voltage is asymmetric, if Z a ≠ Z b ≠ Z c and φ a ≠ φ b ≠ φ c jets at the phases of the slow difference are determined by Ohm's law
İ a = Ú a / Z a; İ b = Ú b / Z b; İ c = Ú c / Z c.
Strum at the neutral dart İ N more geometric sum of phase strums
İ N = İ a + İ b + İ c .
The voltages will be U a \u003d U A; U b = U B; U c \u003d U C, U Ф \u003d U L / zavdyaki neutral dart at Z N \u003d 0.
Otzhe, neutral wire ensure the symmetry of the phase voltage of the priymach with a non-symmetrical drive.
To that chotiriprovidnu merezh include single-phase non-symmetrical navantazhennia, for example, electric lamps of heating. The mode of operation of the skin phase of the voltage, which is under the constant phase voltage of the generator, is not dependent on the mode of operation of other phases
It is called zero to that which in some strums is equal to zero, and neutral to that which still has skin phases.
Assigning a zero dart in that it is necessary for vibrating the phase voltage of the voltage, if the support phases are different, as well as for grounding the electric field in the meshes with a dead-earthed neutral.
Zavdyaki recognition of zero dart The voltage on the skin phase will be practically the same at uneven ambition phases. Illumination of the saturation, inclusion of a star, and the presence of a zero dart, shards of even phase alignment are not guaranteed.
The span of the zero wire of three-phase lines, in which zero wires are not vicorous for grounding (special or lighting, which are being reconstructed), take close to half the cut of the phase wires.
For example, for example, phase darts may have a diameter of 35 mm2, zero wire is taken to be 16 mm2.
Peretin of a zero wire of a three-phase system with a dead-earthed neutral, in a zero-wire wire for grounding, may be at least half of the cut of the phase wires, and in such fluctuations it is more expensive.
Zero wire repeated lines 320/220 is to blame for the mother of the same brand and perer_z with phase wires:
on plots, wired with steel wires, as well as bimetal and steel-aluminum phase wires, with a span of 10 mm2;
in case of impossibility to ensure the safety of other means of necessary selectivity, protection from short faults to the ground (with which it is allowed to take zero darts more, lower phase darts).
Sparks in one- and two-phase lines along the neutral and phase wires flow through a stream of the same size, then for these lines, cuts in the zero and phase wires should be taken the same
51. Causes of blame for transitional processes in electric lances. Differential equalization of the electric steel of the Lancers and methods of their perfection.
Transitional processes are blamed for any changes in the regime electric lansyug: when the lancet is connected and turned on, when the voltage is changed, when the emergency modes are violated (short flicker, shaving the drota thinly). Changes in the electric lance can be as quiet as other switches, called at random commutation. Physically transitional processes are the processes of transition from a power plant, from a power plant, to a switching mode, to a power plant, from a switching mode.
The transitional processes sound like a breeze: the trivality of them becomes ten, hundred, which are sometimes billions of parts of a second. The frequency of transitional processes is rarely equal to seconds and tens of seconds. The VIVCHENNE of the Relocious process is important, it is allowed to get up, the yak is deformed for the form of the amplitudum, Viyaviti is the distortion of the crusty on the snuffs of the Lantseyug, the yaki is able to viyavit, the zbie - the zbizhita of the amplitudes, the yakiytye of the yak. periodic process, and also signifies the valority of the transitional process. From the other side, the robot is rich in electrical appliances, especially the mechanisms of industrial electronics, based on transitional processes. For example, in electric heating furnaces, the material can be deposited due to the nature of the transitional process. Superficially shallow heating can cause a plume, and superficially more negatively affects the material and leads to a decrease in productivity.
In a wild way in an electric lance, transitional processes can be blamed, as in a lance, there are inductive and mnist elements, which can accumulate the building or give the energy of a magnetic or electric field. At the moment of switching, if the transitional process is started, it is necessary to re-energize between the inductive, mnistem elements of the lancet and the most important energy dzherelami, connected to the lancet. With some part of the energy, it is irrevocably transformed into other types of energy (for example, heat on an active support).
After the end of the transitional process, a new regime is established, which is designated only by the best sources of energy. When the transient energy sources are turned on, the transitional process can be blamed for the fluctuation of the energy of the electromagnetic field, accumulated up to the cob of the transient mode of the inductive and excitatory elements of the lance.
52. Rule the commutations and their vicissitudes of the minds of the cob.
The first law of commutation lies in the fact that the strum at the gallus with the inductive element at the cob moment at the hour after the commutation can be the same, as if the fault was not in the middle before the commutation, and then from this value the fault begins to change smoothly. The said sound is recorded as i L (0 -) = i L (0 +), regardless of how the commutation occurs at the remaining moment t = 0.
Another law of switching is involved in the fact that the voltage on mnіsnumu elementі the initial moment after switching can have the same value, as it is a little without a middle before switching, and then from this value it starts to change smoothly: UC (0 -) = UC (0 +).
Otzhe, the presence of the neck, which avenges the inductance, the lance, which turns on under the voltage, is equal to the opening of the lance in the same place at the time of switching, so i L (0 -) = i L (0 +). The presence of the lance, which turns on under the voltage, the plugs, which to compensate for the discharge of the capacitor, is more likely to short-circuit in the same place at the time of switching, so U C (0 -) = U C (0 +).
However, in an electric lance, there can be voltage cuts on inductances and streams on capacities.
In electric lances with resistive elements, the energy of the electromagnetic field is not stored, on the basis of which the stench of the transitional processes is not blamed, tobto. in such lancers, stationary regimes are established mittevo, stribkom.
Really, whether there is a lancet element, it can be opir r, inductance L and mnistyu Z, tobto. in real electrical outbuildings, they use heat input, sounding the passage of the struma and the apparent support r, as well as magnetic and electric fields.
Transitional processes in real electrical outbuildings can be adjusted or upgraded with a choice of different parameters of lances, as well as for the settlement of special outbuildings.
53. Description of the process of charging and discharging a capacitor connected in series with a resistor. The simplest generator of saw-like voltage.
Let's look at the diagram in Fig. 5.12. At Z A ≠ Z B ≠ Z C strum system is asymmetric (I A ≠ I B ≠ I C), which is similar to Fig. 5.5 I N \u003d Ia + 1c + I with. Tsey strum I create a fall; voltage I N Z N at the neutral dart.
For rahunok, the voltage drop on the neutral rod
potential point Nun different, to that the phase voltage is applied U "c not good for phase voltage
dzherela U c . Schob qi voltage buli equal, guilty
be close to zero opir neutral pro
water.
When Zc is changed to zero (short-terminated receiver phase), the phase voltage U′c = IcZc change to zero. Replacing the support of the phase priymach tyagne change yogo phase voltage.
With a short-circuited phase W accepting neutral point potential P become equal to the potential of the point W, which means the voltage U Aі U "b rise to linear stress Ucaі ubcwhat unacceptable. For a defense against such a regimen of the skin phase, for example, guardians are installed. In case of a short flicker, the melting insert of the fuse burns out, which does not allow transferring to the potential of the point W to the goal P.
For the presence of a neutral signal, a short phase flicker W priymacha є one-hour short chimes for dzherel E C to that, the zapobіzhnik spratsovuє nadіyno. For the presence of a neutral dart, the guard does not work, oskolky mode
Z Z= 0 not є jerel short chirps E.S.
In this rank, as if opir of a neutral drotu, called in practice zero drotom, then:
1) the system of the phase voltage of the primach is asymmetric;
2) change of voltage (opir) of one phase to bring up the change of voltage on all phases of the receiver; 3) in case of gradual isolation of one phase of the receiver (short circuit), the receiver of two other phases can be out of tune with the overvoltage on them; 4) the work of zapobіzhnikіv (of other foreign aparatіv) becomes undesirable. With a glance at it, zero drіt pragnut vikonati with little support.
And how to buti in case of unstoppable urvisches of zero drotu? It is not possible to operate the lansy with this through the insecurity of getting out of the fret of the priymachiv with a short stuttering of one of the phases.
More nadіynym є bagatorazov re-grounding zero drotu: at the neutral point of the generator, in the areas of the galvanization of the lines, at the public and common budvels, at the end of the three-phase line, etc. When shaving the zero drota, the strum will pass through the ground.
Respectfully, due to the method of changing the asymmetry of the phase voltage of the receivers, in practice, single-phase receivers should be divided evenly in phases, in order to change the zero-point stream, which, if equal, is equal to zero.
Neutral at LEP
At the power lines of different classes zastosovuyutsya see different neutrals. Tse pov'yazano z tsіl'ovym prichennyam tаrіznoy аpаratura zahist linії vіd short zamikannya ta vytokіv. The neutral is solidly grounded, insulated and effectively grounded.
Deep earthed neutral
It can be installed in voltage lines from 0.4 kV to 35 kV, with a small longevity of power lines and a large number of connection points. As soon as the phase arrives, the connection of a single-phase voltage is connected between the phase and the zero drotom (neutral). Zero conductor of the generator and grounding.
Insulated neutral
Zastosovuєtsya in lines with a voltage of over 2 kV to 35 kV, such lines may be the middle of the day and there are a small number of points of connection of spare parts, which sound like TS near residential areas and heavy machines of factories and factories.
In lines at 50 kV, it can be insulated, and the neutral is effectively grounded.
Effectively earthed neutral
To be installed on long lines with a voltage of 110 kV to 220 kV (clause 1.2.16 PUE)
Div. also
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Notes
Dzherela
- “Theoretical ambush of electrical engineering. Electric lances » Bezsonov L. A. Moscow. "Vishcha school." 1996 ISBN 5-8297-0159-6
Lesson that characterizes the neutral wire
The cannonade on the left flank will swell, and the cannonade of the right krill will be respected. The arrows of the division of Moran and the division of the Viceroy fired a strong fire, raising the ear of the attack of the right krill.The vice-king opens the village [Borodinim] and crosses with his three bridges, following on the same height with the divisions of Moran and Gerard, yak, under the same stone, straighten to the redoubt and see the line with the other military armies.
Everything is blameworthy but vikonan in order, saving, as far as possible, the troops in reserve.
In the imperial camp, near Mozhaisk, 6th of spring, 1812.
Disposition tsya, already unclear and confused written, - as if you allow yourself without religious fear to the genius of Napoleon to be placed before yoga order, - concluded chotiri puncti - chotiri order. Every day, these arrangements could not be and were not vikonan.
At the disposition it is said, firstly: that they were armed with the garmats of Pernetti and Fouche, on the field chosen by Napoleon, with the harmats of Pernetti and Fouche, as if they could fight them, all one hundred and two harmats, fired fire and sizzled Russian flashes and redoubt with shells. It could not be broken, because the shells, recognized by Napoleon, did not reach the Russian robots, and tsі one hundred and two garmats shot empty pillboxes, while the nearest chief, by Napoleon’s order, did not hang in front.
Another order was that Poniatowski, straightening to the village in the forest, blew the wings of the Russians. It could not be and was not crushed by the fact that Poniatowski, straightening to the village in the forest, following Tuchkov there, blocking his path, and could not get around and not obiyshov the Russian position.
Third order: General Kompan to destroy the forests in order to destroy the first fortifications. The division of the Company did not overcome the first fortifications, but it was victorious, so that, walking out of the fox, it would be small under the cannon fire, which Napoleon did not know.
Fourth: The Viceroy took over the village (Borodin) and crossed with his three bridges, following on the same height with the divisions of Maran and Frian (about the yaks it is not said: where and if the stench will collapse), with yoke straighten to the redoubt with others.
Skіlki can be understood - as if not from a stupid period, then from quiet trials, as if they were the vice-king of vikonati given to you punishment, - the blame for the destruction through Borodino was angry at the redoubt, the divisions of Moran and Friana were guilty of destroying the front at once.
Everything, like and іnshi points of the disposition, did not and could not be vikonan. Proyshovshi Borodino, the vice-king of the bov vіdbity on Kolochі and could not go far; the divisions of Moran and Friana did not take the redoubt, but were beaten, and the redoubt was already on the battlefield, and the cavalry was choked (Imovirno, not transferred to the right for Napoleon, that was not Chuvana). Otzhe, the same day, the order of the disposition was not and could not be vikonan. But in the disposition it is said that after I enter in such a rank, I will be given punishments, in the wake of the enemy, and it could be, that at the hour of the battle, all the necessary arrangements will be made by Napoleon; but it didn’t happen and it couldn’t be that, during the hour of the battle, Napoleon was so far away, that (as it turned out in the course of the year) the head of the battle could not be given to him in a moment, and even the order of the battle could not be vikonan.
Question 6. What is the neutral wire for?
Vidpovid6
. Neutral wire is used to check the phase voltage at the voltage terminals. A= 
a; 
B = b; C= c. In this case, the voltage drop on the voltage is overridden by the equal phase voltages of the generator. In times, if the internal opir of the generator is not enough (equal to zero), then the voltages on the voltage are equal to the phase voltages of the generator, constant and do not lie in the magnitude of the voltage. ( The stream changes, but the pressure on the tension does not change).
Question 7. What are the lines to describe the electric mill of the lancer with asymmetric vanishing?
Vidpovid7
. In case of asymmetric phase tension and the presence of a neutral phase complex, the voltage on the tension 
,
,
related to the complex stresses of the Dzherel A, OV, Ô Z Kirchhoff equations:
;
;
;
de 
- complex stress between the neutral points of interest and dzherela ( merezhі).
call the voltage of the neutral.
The voltage used to neutralize is developed using the 2-node method:
de: Ė -complex EPC, 
- Complexes of conductivity of the phases of nawantage.
Strumi phases of interest know about Ohm's law:
İ a = a / Z a = ( A- )/Z a;
İ b = b/ Z b = ( B- )/Z b;
İ a = s/ Z c = ( C- )/Z c.
Question 8. How to induce the summation of vector diagrams of voltages and streams for the subsequent modes of a three-phase lance?
Vidpovid8 .
Pobudov’s vector diagrams are repaired from vectors of linear stresses, which are given by the line and minds do not lie flat. Tse rіvnostoronnіy trikutnik, utavleniya vectors of linear stresses. The length of the vector is consistent with the linear stress, and the distance between the vectors is consistent with the phases between the vectors of the stress.
Pobudov with vector diagrams for a vipadku equal navantage .(symmetric mode).
1. Choose the complex plane (+1, j). Really everything +1 is directed vertically uphill, vyavnu-vzdovzh axis-X. (Turn on the cut +90°).
2. Select the scale of the voltage, for example 1cm→20V. Vector U a(at the scale) indicative of the real axis +1. The end of the vector is signified by a small letter a.
3.Vector U b i U c (in scale) is slightly lower than +120 і -120 variant. Kіntsi vektorіv is signified by small letters bі c obviously.
4. The point that indicates the cob of coordinates is signifi- cantly small letter n. Tse neutral point of acceptance.
5. Be the vector of linear voltages. For tsgogo z'єdnuєmo kіntsі phase vektorіv. Take away vector U a b= U A b, U bc = U BC, U c a = U C А.
Dot, mottled N on the vector diagrams, which indicates the neutral point of the generator, is located in the center of the line voltage tricot. Do you have a generator neutral N escaping from net trawling n. At the tip of the slope n, which shows a neutral point of interest, is known by the method of notches. The vectors of the streams are added according to the ratio to the highest vectors of the phase voltage with the adjustment of the phases between them.
Below are vector diagrams for different robot modes.
(Fig. 8).
Mode 2 Shaving phase BUT (Fig. 9):
When phase A is cut and the two other phases are equally attracted, the neutral point of acceptance n move to the middle of the line voltage BC. Z b i Z c appear sequentially connected and switched on to the line voltage BC. Voltage drop between points A that n increase, and the phase voltage b i c become equal to half of the linear BC.
Mode 3 Short flicker phase A (Fig. 9).
In case of phase A fading and the same saturation of the two other phases (that is, when the phase A with the zero point of the saturation is connected to the cob of the phase A with the zero point of the saturation), the point n moves to point A. The phase of the voltage A becomes equal to zero, the strum b i c become equal linear.
Opir, Z a ≠ Z b≠ Z c , phase voltage of the receiver a ≠ b≠ c , between points Nin is the neutral displacement voltage.
4.1.
4.2. Using the method of notches (with a compass or a line) from the skin vertex, we put in the input vectors and phase voltages of the primer. A speck of crossbars will give a point of neutrality n. Generator neutral point N zalishaєmo in a big place.
4.3 Returning point nі N. Tse the vector of the voltage used in the neutral U nN (at the scale).
4.4 We will be the vector of phase streams of advancement. If there are light bulbs, if it is possible as an active support, then the phases between the phase voltage and the phase stream of the voltage must be cleared up. To that, the vector strum_v_dklada_mo (scaled) vzdovzh Vіdpovіdnyh vіdpіdnyh vektor_v phase ї nagruzki.
***) In the case of the wave, it is necessary to determine the destruction of the phases between the struma and the phase-like phase stress according to Ohm's law in the complex form and the vector struma with the help of a protractor.
Mode 5. Nervnomirne navantage with a neutral dart (Fig. 11).
For the presence of a neutral phase, the voltages of the priymach become equal to the phase voltages of the dzherel A= a; B = b; C= w:
