Rozrahunok struma zamikannya. Rozrahunok struma single-phase flickering to the ground in a fence from an insulated neutral
a) Changing the struma with a short zmіkannі
Strum at the process short hum does not become immutable, but changes, as shown in fig. 1-23. From this little one you can see that the strum, which increased at the first moment of the hour, fades to a deacoy value, and then under the action of the automatic wake-up regulator (ARV) reaches the value that has been restored.
Promіzhok an hour, by stretching out some kind of change in the magnitude of the strum k.z. called a transitional process. After that, as a change in the magnitude of the struma, it is applied and until the moment the short circuit is turned on, the mode is switched on, after the short circuit has been established. Depending on whether the selection of the settings of the relay protection or the re-verification of the electrical control for thermal and dynamic stability is carried out, we can change the value of the stream at different times and hours.
Shards of the line may be a sing inductive support, which pereskodzhayut mittevamu strum at the time of a short zamikannya, the value of yogo is changed by a streak, and the growth of the sing law from a normal to an emergency value.
To simplify the analysis of the analysis of the strum, which takes place during the first hour of the transitional process, it is looked at how it is composed of two warehouses: aperiodic and periodic.
Aperiodic is called postiyna after the sign of warehouse strumu i a, as it vibrates at the moment of a short fading and vanishes suddenly to zero (Fig. 1-23).
Periodic warehouse strumu k.z. at the cob moment to the hour I nmo is called the cob strum of a short chime. The size of the cob strum k. z. vikoristovuyut, as a rule, for the choice of settings and reverification of the sensitivity of the relay switch. The cob strum of a short chirp is also called superperipheral, so that for this child, the substitution scheme is introduced in such a way as the ranks of the superperipheral opir of the generator and the superperipheral e.d.s.
Establishments strum k.z. є periodic strum after the completion of the transitional process, zumovlenogo like extinguished aperiodic warehouse, and the operation of the ARV. Reverse strum up to. is a sum of periodic and aperiodic warehouses at any moment of the transitional process. Maximum value new strumu called shock strum k.z. that is calculated for the hour of re-verification of electrical equipment for dynamic stability.
As it was planned more, for the selection of settings and the re-verification of the sensitivity of the relay, the sound of the cob chi over the front strum of the short circuit, the magnitude of the change, is the simplest. Vykoristovuyuchi cob strum in the analysis of swidkodіyuchy zahistіv and zahistіv, scho mayut small windows of the hour, not good aperiodic warehouse. The admissibility of which is obvious, to that it is aperiodic warehouses in merezhs high voltage it fades away more quickly, in an hour 0.05-0.2 s, then it will sound less than an hour when you look at the sights.
At k.z. at the edge, which live in the dark energy system, generators, which are equipped with ARV, which support constant tension on її tires, periodic storage stream at the process of c. do not change (Fig. 1-23, b). To that rozrahunkove meaning of cob struma k.z. at which point it is possible to win for the analysis of the behavior of the relay zahistu, scho di є s be-what-ever-for-an-hour.
At the fences, which live like a generator of the chi system cold sweating, The pressure on the tires as in the process of short circuit. does not become stagnant, but changes at significant boundaries, cobs and strums of k. not equal (Fig. 1-23 a). At the same time, for the rozrahunka, it is necessary to wash the windshield for an hour on the order of 1-2 s and more, the next would be to win the strum k. However, the shards of Rozrahunok strum, standing up, k.z. povnyano folded, it is permissible in more vipadkiv vikoristovuvaty cob strum k.z. Such an allowance, ring out, do not lead to a great death. Explain it like this. On the size of the struma, scho having risen, k.z. Significantly greater injection, lower by the size of the cob strum, to give more transitional support at the mist of poshkodzhennya, strumi navantazhennya and іnshі factori, so that you don’t hesitate to sound when the strum roses to. To that rozrahunok strumu, that having risen, k.z. maybe mother even a great kidnapping.
In response to all that has been said above, you can use an additional and more acceptable number of victories for the analysis of relay protections, which will develop from a vitrimonial hour, cob struma k.z. When it is possible to lower the struma with a short zamikannya, it is necessary to vrakhovuvat for the zahist, to make a windshield for the hour, introduced before the rozrahunka to increase the coefficients of confidence, it is equal to the shvidkodіyuchim zahists.
b) Appointment of cob struma k.z. in a simple scheme
Oskilki with a three-phase short circuit. (Fig. 1-24) f.d.s. and support at all phases are equal, all three phases are changed at the same minds. vector diagram for such a short zamikannya, yake, ya know, called symmetrical, induced in fig. 1-18, b. Rozrahunok symmetrical lanceug maybe a big apology. In fact, the shards of all three phases are rebuying at the same minds, to finish the growth of one phase, and then we will expand it by two more. Rozrakhunkov's scheme at his mother looked, the testimony in fig. 1-24, b. It is quite obvious what to induce in the simplest way, what is being looked at, the rest of the scheme is much simpler, below is shown in fig. 1-24 a.
Folding electric lancers If there are a lot of parallels and last ones, the difference will be even more obvious.
Father, at symmetrical system rozrahunok strumіv i naprug can work only one phase. Rozrahunok is based on the folding of the substitution scheme, in some cases the elements of the rozrahunkovo scheme are replaced by suitable supports, and the zherel of life is indicated by them. d.s. or the tension on the clamp. The skin element is introduced into the replacement circuit with its active and reactive supports. Opir generators, transformers, reactors are indicated on the basis of passport data and entered to respect, as indicated below.
Reactive supports of power transmission lines are protected by special formulas, or they can be applied approximately for such a virase:
de l-dovzhina dіlyanki linії, km; x ud - pitoma re active opir lines, Ohm / km, as you can take equal:
Nadali for forgiveness, it’s important to remember that umova (1-23), as, as a rule, it is used for 110 kV tension fencing and more, effectively, and we will introduce only reactive supports rozrachunk scheme
Designated struma k.z. under the hour of life in the system of non-circumferential sweating. Strum k.z. in the rozrahunkovy scheme (Fig. 1-25) it should be distinguished from the onset of virase, kA:
de x res - the resulting opir to the point of the short circuit, equal to the fall of the sum of the transformer supports and lines, Om;
U s - mizh phase voltage on the busbars of the system there is an unrestricted pressure, kV.
Under the circumstance, the system of non-fenced sweating may be on the verge of a tighter life, the voltage on the tires of which is left permanently independently from the city. at the outer edge. Opir system unrestricted tension is taken equal to zero. If you really want a system of uncircumcised tightness, you can’t understand it widely with short fluctuations. It is possible to understand that the system, which is being looked at, may not be tight in quiet depressions, if the internal support is less than the support of the outer elements that are included between the tires of the system and the point of c.
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Example 1-1. Designate a strum. pass with a three-phase short circuit behind the reactor with a support of 0.4 Ohm, which is connected to the tires of the generator voltage of 10.5 kV of the exhaust power plant.
Solution. The reactor opir points are significantly larger, the lower opir of the system can be taken into account, which are connected to the tires of non-fenced tightness.
Designated struma k.z. under the hour of living in the system of obmezhenoї sweating. As an opir of the system, to live the point of a short zamikannya, it is equally great, it is necessary to protect the strum of the k.z. In this way, an additional support x spst is introduced into the substitution circuit and it is accepted that tires of unobstructed tightness are behind this support.
The value of the struma k.z. be assigned to such a virase (Fig. 1-26):
de x vn - opir of the lance of a short flash between the tires and the point of the short circuit; x syst - opir system, guidance to tires dzherel.
Opir systems can be assigned, as well as tasks for a three-phase strum. on її tires I k.z.zad. :
Example 1-2. Significance of the strum of a three-phase short circuit behind the support of 15 ohm lines 110 kV, which live in the buses of the substation. Strum of a three-phase short circuit on the busbars of the substation, guidance up to a voltage of 115 kV, up to 8 kA.
Solution. Vіdpovіdno up to (1-26) x syst:
The strum appears at the mist of the k.z. obviously (1-25):
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Opіr system pіd hour rozrahunkіv k.z. maybe the tasks are not strum, but the intensity of a short flicker on the buses of the substation. The tension of a short zamikannya is a mental value, equal
de I k.z. - Strum short zamikannya; U cp - the average rozrahunka voltage at that stage of transformation, where the short strum is counted.
Example 1-3. Significance of the strum of a three-phase short circuit behind the reactor support 0.5 ohm. Reactor live in tires 6.3 kV substations on some other versions 300 MB A.
Solution. Significantly opir systems:
c) Designation of excess stress
The scheme is shown in fig. 1-26, the value of the excess pressure on the tires varies according to the onset of stress:
х - opіr vіd tires dzherel zhivlennya to the point de vynachaetsya surplus voltage.
The scores of the opir of the analyzed lancet are taken to be daily reactive, virazi (1-27) and (1-28) include absolute values, and chi are not vectors.
Example 1-4. Calculate the extra phase voltage on the busbars of the substation at the butt 1-2.
Solution. For the first viraz (1-27):
d) Razrakhunki strums short flickering and voltage at the opening of the fence
At the folding opening of the fence, in order to designate a strum at the mist of the short circuit, it is necessary to change the replacement scheme in advance so that it is small, simple looking, it is possible to build with one zherel of life and one strong support. With this method, it is carried out adding successively and in parallel the inclusion of needles;
Example 1-5. Change the replacement scheme, point to fig. 1-27, determine the resulting opir and strum at the misc. The values of the supports are shown in fig. 1-27.
Solution. The transformation of the scheme of substitution is robimo in the offensive sequence.
For rozpodіlu struma k.z. behind the diagrams you can speed up the formulas, pointing at the table. 1-1. Rozpodіl strumіv carried out sequentially in the reverse order, beginning with the rest of the stage of the transformation of the replacement scheme.
Stock 1-6. Rozpodіliti strum k.z. behind the needles of the scheme, pointed at fig. 1-27.
Solution. Significant strumi in parallel gilkakh 4 and 7 is similar to the formulas (Table 1-1):
Strum I 7 to pass along the support x 5 and then rozgaluzhuetsya parallel gilkami x 2 and x 3:
Zalishkov's voltage at any point of the drawn scheme can be marked by a path of subsequent summing up and a significant drop in voltage in її needles.
Stock 1-7. Calculate the excess voltage at points a and b of the circuit shown in fig. 1-27. Solution.
Yakshcho well e.d.s. not equal, equivalent to f.d.s. cheer for this formula:
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e) Razrahunok strum_v short circuit for passport data of reactors and transformers
In all butts, looked more, the supports of all the elements of the circuit were set in ohms. The support of reactors and transformers in passports and catalogs is not set in ohms.
The parameters of the reactor are set according to the number of visible value voltage drop in the new one at the passage of the nominal stream x P %.
Reactor opir (Ohm) can be assigned to such a virase:
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de u hom ta i hom - Rated voltage and the reactor strum.
Opir of the transformer is also shown in vіdsotkakh as the value of the drop in the voltage in the first windings at the passage of the stream, equal to the nominal one, u K , %.
For a two-winding transformer, you can write opіr (Ohm):
de u K , %, U HOM , kV, - specified more, and S HOM - nominal intensity of the transformer, MB A.
In case of a short circuit behind the reactor or the transformer, connected to the busbars of the system of non-fenced pressure of the jet and the pressure of the short circuit. vyznachayutsya for such viraz:
de I hom- nominal strum type of reactor and transformer.
Stock 1-8. Calculate the maximum possible strum of a three-phase short circuit. behind the RBA-6-600-4 reactor. The reactor has the following parameters: U H = 6 kV, I H = 600 A, x P = 4%.
Solution. It is necessary to designate the most possible short circuit strum, however, that the reactor is connected to the busbars of the non-fenced pressure system.
Vіdpovіdno up to (1-33) strum k.z. pretend to be behind the reactor
Example 1-9. Signify the maximum possible strum and tightness of the triphasic short circuit. behind the low transformer: S, H = 31.5MB A, U H1 = 115 kV, U H2 = 6.3 kV, u K = 10.5%
Solution. Accepting, like a front butt, that the transformer is connected from the side of 115 kV to the busbars of the system of non-fenced tightness, it is significant strum k.z.
Nominal winding stream 6.3 kV of the transformer is additional.
Details Created: 24 April 2011
I to strum single-phase short circuit, A; U f Z t single-phase flicker on the ohm case; Z c new opir phase drіt-zero drіt, Ohm.
This formula allows for a variation in the removal of results at the boundaries of ± 10%. For an accurate rozrahunka of a short zamakannya, it is necessary to coristuvatysya according to GOST 28249-93.
The main warehouse formula is the latest opir of the lancer. Z c. It can be known in 2 ways:
V_dom_ parameters of the drotu and transitional supports
If we take into account the parameters of the dart and the transitional support, then the value of the total support of the lancer is calculated according to the following formula:
R f active phase opir, Ohm; r n active opir zero dart, Ohm; r a is the total active opir of contacts of the lancet phase-zero (snaps on the inputs and fittings of the devices, the sockets of the contacts of the devices, the contact at the short circuit), Ohm; x f "internal inductive opir of the phase drotu, Ohm; x n" internal inductive opir of the zero drotu, ohm; x" zovnіshnіy іnductivny opіr lantsyug phase-zero, Ohm.
Vіdomy povniy pitomiy opіr loops phase-zero
With the help of a new pet, the phase-zero loop support is based on the formula:
Z f-0 outside nursery opir loop phase - zero, which should lie in the material and cross the core, Ohm / km; - Dovzhina drotu, km.
As in lances, there are darts of different reparations and dozhins, then it is necessary to take the sum of the values Z c.
butt
For accuracy, let's take a look at the butt of knowledge struma of a single-phase short zamikannya.
Come on є lansyug, to some kind of electrical connection. We are familiar with the parameters of the life-giving transformer, lengthening and cutting the wires of the line. It is necessary to find out about the short circuit strum on the grips of the electric receiver. For which we fold the algorithm diy.
Whose butt is visible single-phase ground fault surge (OSZ) for a 10 kV substation (the scheme of the substation is shown in Fig. 1). Relay protection and automation of all feeders on SEPAM S40 microprocessor terminals (Schneider Electric)
Fig. 1 - Scheme of a 10 kV substation
1. To improve the accuracy of our rozrakhunkiv shdo OZZ vikoristovuєmo method that is rooted in the intended pet of the emnisny strumu zamikannya on the ground. (So the meaning of the pet strumu strumming on the ground, you can win from the final data from Table 1, or take it from technical characteristics cable, yakі nada Virobnik plant)
- Uph - phase voltage of the mesh, kV;
- ω=2Пf=314(rad/s);
- Z - single-phase capacitance across the earth (µF/km);
2. Since then, we have appointed the petty strum of the earth, rozrakhovuemo vlasny strum of the cable line:
The results of the investigations are entered to table 2
Table 2 - The results of the surveys
| Name of arrival | relay type zahistu | cable brand, peretina, mm. |
Dovzhina, km | Pitomy єmnіsny strum mikannya on the ground Iс, А/km | Vlasny strum cable line Ic.fid.max,A |
|---|---|---|---|---|---|
| CL-10 kV No. 1 | SEPAM S40 | APvEVng-3x120 | 0,5 | 1,89 | 0,945 |
| CL-10 kV No. 2 | SEPAM S40 | APvEVng-3x95 | 0,3 | 1,71 | 0,513 |
| CL-10 kV No. 3 | SEPAM S40 | APvEVng-3х70 | 0,7 | 1,55 | 1,085 |
| CL-10 kV No. 4 | SEPAM S40 | APvEVng-3x95 | 0,3 | 1,71 | 0,513 |
| KL-10 kV No. 5 | SEPAM S40 | APvEVng-3х70 | 0,2 | 1,55 | 0,31 |
| CL-10 kV No. 6 | SEPAM S40 | APvEVng-3x95 | 0,6 | 1,71 | 1,026 |
3. Razrakhovuєmo strum spratsovuvannya zakhistu, when you wake up in the case of a wet strumu following the formula (thy mind you take care of the unscrupulous zakhistu at the same time as a single-phase zamіkannі on the ground):
- Kn - coefficient of reliability (taken equal to 1.2);
- Kbr - coefficient "kidka", which is a vrakhovu kidok of the mnistny strum at that hour, if the OZZ is forfeited;
- Ic.fid.max – the maximum strum of the feeder, which is protected.
The first strum spratsovuvannya zakhistu skladє:
- - KL-10 kV No. 1 Iсз= 1.134 A;
- - KL-10 kV No. 2 Iсз= 0.62 A;
- - KL-10 kV No. 3 Iсз= 1.3 A;
- - KL-10 kV No. 4 Iсз= 0.62 A;
- - KL-10 kV No. 5 Iсз= 0.37 A;
- - KL-10 kV No. 6 Iсз= 1.23 A
4. Revisiting sensitivity to zakhist, with the improvement of what will be included minimum quantity including lines, our mind has everything that is on the section.
I beg your respect, that the coefficient of sensitivity is concordant with PUE clause 3.2.21 is more: for cable lines- 1.25, for repeated lines- 1.5. At the book "Rozrakhunka of the relay protection and automation of the rozpodіlnyh merezh. M.A. Shabad -2003 r" Kch = 1.5-2.0 should be induced. In this rozrahunka, I take the coefficient of sensitivity to PUE. What coefficient of sensitivity to accept, choose yourself.
De:
IсΣmin - the least real value of the total єmnіsny strum.
In my opinion, the least real value of the total strum is the total strum of the sections:
I section - IcΣmin = 2.543 (A);
II section - IcΣmin = 1.849 (A);
5. Significant hour of spratsovuvannya zahistu vіd OZZ:
For all cable lines of 10 kV, which are included, the hour of protection is assumed to be equal to 0.1 sec.
Table 3 - The results of the investigation of the protection against the OZZ
| Name of arrival | relay type zahistu | First strum spratsovuvannya Iсз, A |
Hour spratsovuvannya zakhistu, sіk | Coefficient of sensitivity, Kh |
|---|---|---|---|---|
| CL-10 kV No. 1 | SEPAM S40 | 1,134 | 0,1 | 1,4 > 1,25 |
| CL-10 kV No. 2 | SEPAM S40 | 0,62 | 0,1 | 3,27 > 1,25 |
| CL-10 kV No. 3 | SEPAM S40 | 1,3 | 0,1 | 1,12 |
| CL-10 kV No. 4 | SEPAM S40 | 0,62 | 0,1 | 2,2 > 1,25 |
| KL-10 kV No. 5 | SEPAM S40 | 0,37 | 0,1 | 4,2 > 1,25 |
| CL-10 kV No. 6 | SEPAM S40 | 1,23 | 0,1 | 0,67 |
For the arrival of CL-10 kV No. 3 and No. 6, it is not enough for the sensibility of the defender, so we can stop the replacement of the Sepam S40 terminal → the Sepam S41 or S42 terminal, which allows vikonati directing zahist zero sequence.
In order not to spend a lot of time on rozrahunok by hand, the bula is crushed:
List of literature:
- 1. Rozrahunki relay protection and automation of rozpodіlnyh merezh. M.A. Shabad -2003 r
- 2.RD 34.20.179 Standard instruction to compensate for the strum of the earth in electric wires 6-35 kV - 1993 r
- 3.Zamikannya to the ground in the range of 6-35 kV. Rozrahunok of settings of non-directional strums. Shalin A.I. // News of Electrical Engineering. - 2005 r
