How to practice a three-phase strum merezha from an insulated neutral
The one with the coils of the inductance coil, connected between the neutral N and grounding (Fig. 1), has a short circuit on the ground, crim struma I Z.Z, to pass the inductive strum I L.
Rice. 1. Principle of compensation
The assigned streams are shifted in phase one by one at 180 °. That's why the stench is seen one by one; as a result of a sumarny (surplus) strum at the mist of a ground fault I OST.Z<< I З.З, т. е. во много раз меньше емкостного тока I З.З.
On fig. 2 shows a vector diagram of stresses (Fig. 2, a) and streaks (Fig. 2, b) at the edge with strum compensation I Z.Z. The straightening of the strum is shown in fig. one.
Explanation before prompting vector diagrams.
The vector of the voltage U AB is the difference between the vectors EPC: ? AB=? BUT -? B. Straight vector? AB - what is the end of the vector? B to the end of the vector? A. Why is it explained, what is viraz for? AB can be recorded at the sight? A =? B+? AB. To know the sum of two vectors, it is necessary to add another vector (?AB) to the end of one vector (?B). The crazy vector (? A) come out, how can I get the cob of the vector? B (point N) at the end of the vector? AB. Direction of the vector - from the point N to the end of the vector? AB. Qi rules stosuyutsya pobudovi vector? AS. To inspire vector diagrams, the scheme shown in fig. 1, hand-feed at the sight shown in fig. 3.
Rice. 2. Vector diagrams: a-voltage; b-strumiv
Rice. 3. Streaks and voltages when phase A is shorted to ground
A sum of strums to pass through the place of zamikannya on the ground? B .3, ? C .3, ? L - Do the first two streams have an ambiguous character and move in phase vectors and similar EPCs? aw ta? AC at 90°. The strum vector in the coil of inductance L is phased by 90 ° in the EPC vector, what did the strum call? BUT.
Suma strum? B Z i? S.Z is inspired by the parallelogram rule (it is possible, as shown in Fig. 2, b, to extend to the end of the vector? B.Z vector? S.Z). The sum of these vectors, tobto. the vector of the strumu zumikannya on the ground, marked yak? Z.Z.
Vector surplus strumu zamikannya zemlі poduvaniya yak suma vektorіv? L i? Z.Z. Is it straight from the point 0 to the end of the pribudovanogo to the vector? L vector? Z.Z.
Ideally, the resonant tuning of the coil, i.e., I rest \u003d 0. However, reality is within reach, i.e. up to. the number of inclusion lines in the merezha is not consistent.
The superfluous strum is to blame for the mother's inductive nature, so I L > I Z.Z. It is necessary for saving in all modes of mesh directly tightness of zero sequence. The nonviolation of this position, transferred by the PTE, can lead to incorrect actions of directing defenses and signaling about the earth.
The coil of inductance L is usually called a grounding arc-extinguishing reactor (reactor - like the word reactive, so it can be reactive in nature).
Grounding arc-extinguishing reactors (GGRs) should be installed not at the local, but at the railing substations, so that the sound of the sound before the next moment of the earth was minimal. At the same time, the substation is guilty, buti is tied with a measure of life no less than two lines (moving out of the miraculousness of the hope of saving life on it). The pressure of the DGR is due to the єmnіsny strum zamikannya on the ground. Oskilki tsya tension is reactive, then
Q DGR \u003d nI Z.Z U F.NOM
de n \u003d 1.25 - coefficient, which is the development of the insurance network; U F.NOM - nominal phase voltage of the wire.
Oskіlki strum DGR I L є striynym strum zero sequence, then the zero sequence of the transformer, to the neutral of which the DGR is connected, may be minimal. Can you show that you are more than happy with the transformer with the circuit diagram? / Δ. On the introduction of the DGR, recognized for grounding, a transformer TA (Fig. 1) is installed, which is necessary for controlling the struma when adjusting and testing the compensation system I Z.Z. For the connection of the DGR, there are okrem power transformers, so the windings of the PN of the main power transformers in the centers of living cannot be neutral (the stink of the junction at the trikutnik).
During the operation of the measure, її parameters are changed: through switching (increased or switched on), the capacity of the earth phases is changed linearly. Tse to bring the system of compensation to discord. Permissible world discord is 5%. Sob please given with the help, the best way to stop the DGR from the smooth automatic regulation of the inductance.
Switching on (shaving) one of the phases of the transformer, to the neutral of which the DGR is connected, to bring the voltage up to the neutral. The voltage should be set to 0.5U F.NOM), which should not be allowed (for PTU, the voltage on the neutral of the transformer is allowed no more than 15% and for a period of 1 year no more than 30% of the nominal phase voltage). The norms of voltage on the neutral windings are due to the fact that the insulation of the transformer windings in the neutral area is weakened and the voltage on the neutral can lead to breakdown.
Theoretical analysis shows that in order to fully compensate for the earth streak, it is possible to turn off the appearance of repeated breakdowns in isolation after the first breakdown, and the barrier can be successfully repaired. To this end, developments are underway for special regulation of arc-extinguishing reactors and attachments for their automatic regulation. Zokrem, good results have been directly achieved by Professor V. K. Obabkov. In these distribution areas, compensation is not only for a temporary warehouse ground, but also for an active warehouse, which is necessary for switching off the electric arc, which is interleaved.
Placed on 07/05/2011 (valid until 07/18/2013)
As a lot of our readers, especially the facsimiles of design organizations, have no specific recommendations in the current Russian technical literature on how to choose protection from a zamikan on a sinful earth (OZZ) and daily modern methods of adjusting settings. For this reason, the materials for this purpose call for great interest.
Oleksiy Shalin, Doctor of Technical Sciences, Professor of the Department of Electrical Stations of the Novosibirsk State Technical University
In the previous issue of the journal (“Novini Elektrotekhnіki” No. 4 (34) 2005), an article by Oleksiy Ivanovich Shalіn was published, in which the butt of the rozrahunka of the settings was set to strike the ground, which reacts to the zero-sequence voltage.
About the value of the discount coefficient
The recommendations of the authors were made to investigate the settings of the non-directional strum protections of zero sequence in the OZZ. From these recommendations, it is clear that fakhivtsy suttvo diverge in thoughts about such fundamental values for the rozrahunka, like the coefficient of the kidka, the normalization of the coefficient of sensitivity is thin.
Commentary to Sergia Tytent Kittenkov Sudraju, Shaho Wickworks at the roses Krayfіrtsієnt Dvka, Shaho to serve in the main VID visop-frequency stream of zero-by-country, Scho Vikonniє in the process of iznosti sampling Fazy Lantseaga, the charge of the єnnivities of the phases of the phase, not to smear the resistive landnery neutrals. It turns out, zokrema, tim, that the resistor at the 6-10 kV lines is switched on to the lance of a low-voltage neutral transformer.
How often do you tell the truth, be it more concretely expressing your own inter-truth. If the language is about resistors that are installed in the neutral of the neutrals (the neutral is a three-phase throttle coil with a zigzag zigzag) obviously, then such a thought is absolutely true in most cases. Behind the first harmonic, the inductive support of the neutral with a voltage of 63 kVA at a voltage of 10 kV becomes 96 ohms. According to 10-20 harmonics, which are present in the process of recharging capacities during OZZ, the operation is up to 960-1920 Ohm and with a resistor support of about 100-150 Ohm, the total opir of the “neutralizer - grounding resistor” will be practical. As a result, in accordance with the opinion of Sergiy Titenkov, the resistor that is grounded is practically not in line with the recharge capacity and, in such a rank, is not in line with the throw factor.
At a voltage of 35 kV, tri-winding power transformers can lead to the neutral. The grounding resistor is switched on with a neutral wire. To say to this person that this resistor does not flow into the overcharge stream would be wrong.
About the hour
Let's look at the circuit for the butt of the circuit, induced in. There is a living transformer with a voltage of 35 kV and an intensity of 10 MVA. As a result, one power line of the power transmission line is powered, so then it is divided into two lances, so that they can live their transformer with an intensity of 4 MVA with a circuit for connecting the primary winding to a star with a neutral wire. To reduce the level of overvoltage at the neutral transformer, the included grounding resistors. Vykoristannya in the measure of grounding resistors allows you to increase the efficiency of protection, but at the same time, the methodology for choosing the settings has been reviewed.
Vіdpovіdno to strumu spratsovuvannya zakhistu vіd OZZ ІСЗ in merezhi z insulated neutral for the presence of the cable transformer, the zero-sequence stream is selected from the offensive mind:
de k n = 1.2 (coefficient of reliability);
k br - the coefficient of the kick, which is the protection of the kick of the strum at the time of the discharge of the OZZ, as well as the building of the relay to respond to the new one;
I s.fid.max - the maximum strum of the feeder, which is protected.
Vіdpovіdno to for mittєvo dyuchyh zahistіv vіd OZZ in rozrakhunkah next to the value of creation k n k br = 4…5. For zahistu for an hour for the possibility of vining, the arcs kн kbr = 2.5 are interleaved. Obviously, these values are recommended by the author for the traditional industrial relays, including RTZ-51.
At the suggestion to vvazhat k n \u003d 1.2, k br \u003d 3 ... 5 (a hundred relays of old types). Relay RTZ-51 is recommended to accept kbr = 2…3. At the same time, it is suggested to vikonuvat the zakhist without a windshield for an hour. “If you choose the protection of the OZZ of modern digital relays, for example, the SPACOM series, the SPAC-800 ..., you can get the value k br = 1 ... 1.5 (you need to check with the manufacturer)” .
In my opinion, there, where it is possible, it is better to win the victory over the OZZ from the late hour. Tse daє mozhlivіst zabezpechiti selektivnіst at dvoh i bіlshe poslіdovno included LEP, vikoristovuvati in rozrahunkah values less then koefіtsієnta kidka, zapobіgaє pomilkovim vіdklyuchennyam neposhkodzhenih lіnіy pіslya of yak vіdklyuchaєtsya poshkodzhena lіnіya (via ferorezonansnі yavischa, pov'yazanі vimіryuvalnimi transformers naprugi s), i m. d. d.
At deyaky galuzahs (mines, kar'єri toshcho) є normative documents, which will require a negaine inclusion of OZZ. There it is necessary to win the mittevo chivalry of defense against the OZZ.
Appointment of єmnіsnyh strumіv
The value of I s.fid.max \u003d I CS for merging from an insulated neutral is recommended, for example, to be as follows:
for cable ties
for merezh with repeated LEP
de U- Rated voltage railings (kV);
S - total length of the line (km).
The sumarny єmnіsny strum of the railings is shown as the sum of the descriptions of the warehouse of all the galvanically connected lines of the railings.
More precisely the value of the strum I s. Prote there it is indicated that the value of the strum is determined according to (2), (3), it can give a penalty close to 40-80% equal to the real one, we measure it with OZZ in a strum. One of the reasons is the lack of capacity of the earth to save electricity, for example, engines, as well as the construction of the overhead power lines (the type of support, with a grounding cable or without it) is thin.
(4)
de U f - phase voltage (kV);
w = 2pf = 314 (rad/s);
C S - capacity of one phase of the gap between the earth (F).
(5)
de c i - Pitoma capacity per phase i-oї line (F/km);
l i - Dovzhina i-oї line (km);
m - number of lines (cable lines, wired with a ground cable and without it);
c j - capacity per phase of the j-th element of the measure (F);
q j - the number of elements in the measure, which are to be insured, krіm LEP (for example, dvigunіv);
n- blatant number such elements.
(6)
de S nom - nominal total tightness dviguna (MV A);
U nom - nominal voltage of the motor (kV).
For other types of electric motors
(7)
de n nom - Nominal frequency of rotor wrapping (r/hv).
As it was conceived more, the rozrahunkovі єmnіsnі strumi merezhі zvіchây vіdіznyayutsya vіd real, yаkі can be seen only by zamіrіm on objects. However, the process of vimiru єmnіsny strumu, krіm tekhnіchnіh difficulties, po'yazyany shchey іz deakoy methodical insignificance. Dosvіd pokazyvaє, scho on rich objects near the warehouse of the єmnіsny strumu merezhі navit with metal OZZ there are no less than the warehousing industrial frequency, and the th value of the stream of the most important harmonics.
Vimir of the total value of the strum, for example, for additional traditional devices, recognized for vimiryuvannya strum in the industrial frequency, bandages from suttivim bluffs. In reality, the death rate was close to 30% (zocrema in the case of a change in the vimiryuvannyh strums of a rozrachunkian). Larger precisely єmnіsny strum merezhі can be vibrated with an oscillograph way from distant layouts at the harmony warehouse.
Streams of zero sequence in resistive-grounded wires
For the presence of a number of grounding resistors in case of an external OZZ, an active strum I IR can also be used. If you want to replace I s.fid.max (1) you need to submit
Sensitivity is changed by the value of the coefficient k year:
(9)
de k h. norms - normative coefficient of sensitivity;
I PROTECT - strum at the defense of the poor LEP.
In resistive-grounded wires and installations
de I" CS - sumarny strum of a fence for virahuvanni smysny strum of a feeder, which is being protected;
I R - strum of a grounding resistor, which flows from the edge of a low-voltage connection. It has been shown that when it comes to the protection of the OZZ, the lines are repeated with the recommended values normative coefficient sensitiveness is unsafe through the possibility of being established in the MISS of the OZZ of the great transitional support and guidance for the sake of reason. In the same place, recommendations were made on how to reconsider the sensitivity of the zakhist at this point.
Strumi in transient modes
Ninі weakly twisting the power supply, yakim may be the value of the coefficient k br pіd hour is installed in the neutral of the earthing resistor. Є two thoughts of anything:
The value of k br can be the same, as in the case of wires without grounding resistors;
The value of k br may be taken smaller, lower at the front slope.
Vіdomo, scho k br to deposit, zokrema, vіd vіdnoshennja of the maximum jet to recharge the capacity of the tank (strium to the discharge of the capacity of the damaged phase and recharging of the “healthy” phases) and the value of the jet jet to be protected in the installed mode of the zone. On fig. Figure 1 shows an oscillogram of a zero-sequence strum 3I0 in the transient process of the earth fault in one of the electrical connections, described in the total strum of the fault in a 19 A. The maximum value of the struma of the transitional process was 138 A, amplitude value having risen to the struma 3I0 up to 16 A. Having determined the increase in the maximum struma to the amplitude, having risen as k max , we will take the fall k max = 8.62.
Having installed a grounding resistor with a support of 2 kOhm in the neutral of the lively transformer (the resistor stream at OZD is 10 A, then it is 0.53 of the total strum stream), it is necessary for the same advent k max \u003d 1.3, tobto. k max decreased by more than 6.5 times. Increase the resistor support to increase k max (in the range of this slope up to 8.62). If a small amount of grounding resistors is installed in the measure, and upon arrival, as it is seen, when an active strum flows through one of them, then it is necessary to reduce the value of k max to a certain decrease in the value of k max, the shards of the 3I0 strum are installed in the examined rise.
From what has been described, it is clear that the value of k br for this type of drop can be taken lower, lower for the capacity of grounding resistors, and the lowering step of k br should lie in the support of the resistor. In the descriptions, there is one more method of grounding, appointments for safety efficient work selective zakhistu flicker to ground at 6–10 kV fencing (Fig. 2). In this case, the neutral transformer is not installed.
With the appearance in the measure of the voltage of zero sequence, which is evidence of those who became flickering to the ground, a special humicator between the skin phase and the earth is smeared with its grounding resistor. Where do they settle active streams flickering to the ground, appendages for the selective manifestation of a weak arrival.
For interchange of overvoltages, which can be connected in the network before the grounding resistors are turned on, the installation is transferred to the LGN busbars. The thermal stability is to blame, but it is secured for an hour before the grounding resistors are turned on, and it is detected by the relay protection of the damaged connection. Spratsyuvavshi, relay zakhist vіdlyuchaє poshkodzhené priednannya, after which the grounding resistors are connected. Grounding resistors are low-power, heat-resistant, with an hour of thermal stability of about 10-20 seconds.
Butt rozpodіlu strumіv
On fig. 3 shows rozpodіl strumіv in lancers of the scheme.
When prompted, the little one was admitted to the fact that:
- capacities of the phases of the power transmission line as far as the earth is bugatorically shifting the capacities of other elements of the circuit;
By turns through transformers, the voltage can be reversed;
The active strum of the isolation of the phases of the earth is more than small;
The supports of the power transmission line and the windings of the transformer are too small.
On the scheme of Fig. 3 not shown switching devices and intermediary overvoltage. Here Tr is a life-giving transformer; LEP1 - LEP, where did the phase flicker to the ground; LEP2 - non-ushkogen LEP (or a group of such lines); R1 - grounding resistors.
From the small one it can be seen that the active streams of the grounding resistors are switched through the transformer Tr live and the short phase of the LEP1 line. As a result, a sum of active streams of resistors in non-shocked phases and a terminal stream of a non-shocked LEP flow through. Behind the attack of a non-early LEP, there is no more than an illusory strum of the LEP.
Descriptions of a higher method of resistive grounding of buv implementations at three substations of the Khanty-Mansiysk REM Naftoyugansk electrical tethers. Knowing up to today's day confirmation of operation high efficiency such a technical solution. In times of zastosuvannya tsієї circuits, as shown by our research, grounding resistors also reduce the value of kmax, and therefore і k br. At the same time, for achieving the same effect, the support of resistors in the circuits of Fig. 2, 3 next take 3 times as large, lower when the grounding resistor is turned on, for example, the neutral of the power transformer.
Rice. 1. Oscillogram of a zero-sequence surge at the transitional process of a single-phase earth fault at a 35 kV gauge
Rice. 2. Inclusion of grounding resistors between phases and ground at different faults
Rice. 3. Rozpodіl strumіv v lanceugs scheme
Carrying out the follow-up allows the growth of the onset of the windings: changing the number of grounding resistors without neutrals to lead to a change in the value of k br. Zastosuvannya neutralerіv mnіzhuє tsey efekt, zdebіlshego practically zvodyachi yogo naіvіvets.
As a result, when the grounding resistors are connected through the neutralizer, the value of the coefficient of the throw k br is taken, as for the insulated neutral line, it is likely to be recommended.
When the grounding resistors are switched on behind the guiding circuits without the use of neutralizers, the values of kbr can be reduced. Since the strum of the grounding resistor is approximately equal to the total strum of the wire (as it is recommended for optimal exchange of overvoltage), the value of the coefficients of the throw is valid up to can be accepted at a level of 1.2-1.3.
How to support grounding resistors? three phases merezhi (as it often happens with great values of the strum), the value of k br can be taken the same as for the merezha from an isolated neutral, or it is assigned after additional rozrachunkiv strums of the transitional process of OZZ.
Bula described one of the peculiarities of the mountainous arc in domestic cables with paper-oil insulation. It was about those that, at the first stage of the OZZ, the ignition of the arc in such a cable would lead to the laying out of the oleic-rosin seepage and seeing a significant amount of gases, like extinguishing the arc, like vinyl. As long as the gases, which have settled down, do not "pishli" in different sides, in the middle of the arc between the balls of paper, the arc does not burn. With this, through a “pause” in the stream of zero sequence, the defender of the OZZ, at the earliest, you can start working. The reason is that for an hour without a pause, the strum organ rotates at the outer station, that organ of the vitreous clock for an hour, so “not turning” the vitremka is installed at the hour, it also rotates at the outer camp.
In order to protect such drivers from the OZZ from some import companies (as well as from the department of the joint production plant of the Novosibirsk State Technical University and TOV "PNP BOLID") - the option of remembering the fact of the launch of the attack. As if “pecking” of the strum organ, then this fact is remembered for a certain hour up to 0.3 s, and with repeated “pecking” it will turn on. For such protections, it is recommended to take an increase in the value of k br, for example, 1.5 in the measure of the grounding resistor.
Stagnation area of non-directed defenses
On the whole, non-directional strum strums in the form of OZZ can be more effective only in installations with a large number of connections to the connection section, and sometimes a small strum strum. That way, when you see the strum, it’s obvious (1) that it didn’t lead to an unacceptable decrease in sensitivity. This change is typical, for example, for workshops of enterprises with a large number of low-power electric motors connected through short cables.
Since a reactor is installed in such a measure to extinguish the arc, then for the sake of effective fire protection in the short circuit, in parallel with the reactor, turn on the grounding resistor, moreover, the jet that flows through the resistor during the fault is guilty of overshooting the setting of the “rough” protection itself by 1.5 strike. For this type of non-directed strum infection, the necessary selectivity and high sensitivity in OZZ can be ensured.
Significant improvement in efficiency was achieved with victorious strum defenses of zero sequence with the vimir. For example, use a microprocessor terminal to defend, the principle of any foundation on the equal value of the zero sequence in all the accessed sections of the selected tires that are protected. It is not necessary to bring a spratsovuvannya in the case of єmnіsnyh strums. Due to the presence in the reactor line, which is to extinguish the arc, such a zahist allows you to effectively reveal the possibility of failure in the event of a fault.
Literature
1. Shalin A.I. Zakhist vіd flicker to the ground in 6–35 kV lines. The butt of rozrahunka of settings // Novini elektrotekhnіki. - 2005. - No. 4 (34).
2. Shalin A.I. Flickering to the ground at the 6-35 kV fences. Advances and nedolіki rіznih zakhistіv // Noviny Elektrotekhnіki. - 2005. - No. 3 (33).
3. Shabad M.A. Rozrahunki relay protection and automation of rozpodіlnyh merezh. - St. Petersburg: PEIPK, 2003. - 350 p.
4. Andreev V.A. Relay protection and automation of power supply systems. - M.: Vishcha school, 1991. - 496 p.
5. Aleksandrov A.M. Choice of settings for spratsovuvannya zakhistu asynchronous electric motors with a voltage of 1 kV. St. Petersburg: PEIPK, 2001.
6. Chelaznov A.A. Development of technical regulations and standards for the electric energy gallery of the VAT Gazprom // Practice of the third All-Russian scientific and technical conference “Exchange of overvoltage and grounding modes of neutral networks 6–35 kV” / Novosibirsk, 2004. - P. 12–25.
7. About the increase in the reliability of the 6 kV supply of power units AES. Circular Ts-01-97 (E). - M.: Rosenergoatom, 1997.
8. Lur'є A.I., Panibratets O.M., Zenova V.P. that in. A series of neutrals of the FMZO type for the operation of ceramic-coated submagnetized arc-extinguishing reactors of the RUOM series in separate pits made of insulated neutral // Elektrotekhnika. - 2003. - No. 1.
9. Electrical engineer. Volume 3. Virobnitstvo, transmission and distribution of electrical energy / For the editorial staff of professors MEI V.G. Gerasimova et al. (Chief editor A.I. Popov) - 8th view. - M.: Vidavnitstvo MEI, 2002. - 964 p.
10. Bukhtoyarov V.F., Mavritsin A.M. Zahist vіd flicker on the ground electrical installations kar'єrіv. - M.: Nadra, 1986. - 184 p.
11. Korogodsky V.I., Kuzhekov S.L., Paperno L.B. Relay relay for electric motors with a voltage of over 1 kV. - M.: Vishcha shkola, 1987. - 248 p.
12. Patent for vineyards of the Russian Federation No. 2157038. Appliance for detecting the coming from the ground in the distance from the insulated neutral / Shalin A.I. Bulletin of Wines No. 27, 2000
13. Shalin A.I. Flickering to the ground at the 6-35 kV fences. Vipadki wrong dіy zahistu // Elektrotekhnіki. - 2005. - No. 2 (32).
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In electrical engineering, it is clear that it is an omnisniy strum; This phenomenon is blamed for the occasional phase, after which the arc is called, which is grounding. In order to get rid of serious negative consequences, it is necessary at the same time and correctly to win the rose of the eminent struma of the border. Tse allow to change the overvoltage at the time of re-ignition of the arc, and to create a wash for її independent extinguishing.
What is an eminent strum
Єmnіsny strum vikaє, as a rule, on the lines with a great length. In this case, the earth and conductors work similarly to the capacitor plates, adhering to the appearance of singing capacity. Shards can change characteristics, or you can serve as a post until it appears. For cable lines with a voltage of 6-10 kilovolts, this value can become 8-10 amperes per 1 km of length.
In times of connection lines, which are located in a non-negative country, the value of the strum can reach as many as tens and induce hundreds of amperes. In the process of switching on, if the moment comes for the stream to pass through the zero value, the voltage on the contacts that separate will be daily. However, at coming moment the whole possibility of establishing an electric arc.
Even if the value of the surge current does not exceed 30 amperes, it should not lead to serious disturbances in the zone of unsafe overvoltage and flicker to the ground. The electric arc, which strikes at the misery, is quickly extinguished with the one-hour appearance of steel flickering to the ground. All the changes of the legislature are waking up electrical lines, at a straight line from the tip to the cob. The expansion of these changes will be proportional to the length of the line.
In order to change the strum zamikannya on the ground, in the gait, naprugou vіd 6 to 35 kіlovolt zdіysnyuєtsya compensation єmnіsny strumu. This allows you to reduce the speed of reinforcing the voltage at the slow phase after the arc is extinguished. In addition, overvoltages are reduced at times of repeated ignition of the arc. Compensation vykonuetsya іz zastosuvannyam arcing grounding reactors, scho mâyut smoother or step of regulation of inductance.
The setting of the arc-extinguishing reactors is gradually reduced to a compensation stream, the magnitude of which is more expensive to the short-circuited stream to the ground. When the adjustment is made, the variation of the parameters in the compensation order is allowed, if the inductive storage stream is not more than 5 amperes, and the step of the input from the main adjustment is 5%.
Vikonannya nalashtuvannya with insufficient compensation is permissible only in that case, if the pressure of the reactor, which is to be extinguished, is insufficient. Stupin razladu in tsomu vapadku not guilty perevischuvat 5%. The head mind of such a setting is the presence of the voltage of the neutral, as it can be faulted with asymmetrical capacities of the phases of the electric line - when shaving the wires, stretching the cable lived thinly.
In order to get ahead of the winknennya emergency situations and get used to the entrances, it is necessary to loosen the strum on the song space. Establish special methods that allow you to get accurate results.
Butt of the rozrahunka of the strumu
The value of the elastic struma, which in the process of closing the phase of the earth, is less than the value of the elastic support of the measure. Por_vnyannі s іduktivnymi ta active supports. To that, the first two types of support for the hour of the rozrachunkiv are not afraid.
The adopted strumu is most easily seen from the butt three-phase mesh, de at phase A, the magnitude of the strums in the other phases and C is increased for the help of the advancing formulas:
Modules of strums in these phases I in і I s, vrakhovuchi pevn_ pripuschennja С = С А = С В = С С і U = U А = U В = U С can be calculated using one more formula: sum strums of phases B and C. The formula will look like an offensive rank: When carrying out practical rozrahunkiv, the amount of strum zamikannya on the ground can be assigned approximately according to the formula: , de U porіvn. - є phase mid-nominal pressure step, N - coefficient, and l є total distance, which can be an electric call with a point of earth flicker (km). The assessment, won for the help of such a rozrahunka, indicates the independence of the magnitude of the struma from the month of zamikannya. Tsya value is signified by the crown of all lines.
How to compensate for small jets of noise on the ground
The work of electric lines, with a voltage of 6 to 10 kilovolts, is carried out from an insulated or grounded neutral, in a fallow way, from a struma to the ground. In all modes, the circuit turns on arcing coils. The neutral is grounded behind an additional coil to extinguish the arc, in order to compensate for the jet flickering to the ground. If there is a single-phase earth fault, the operation of all electrical receivers will continue in normal mode, but the electrical supply will not be interrupted.
It is significant to build up the Russian cable lines until they have a great capacity, shards of leather cable with their own capacitor. As a result, a single-phase ripple in similar lines can lead to an increase in the struma on a small scale up to ten dozens, and in some fluctuations - hundreds of amperes. Diya tsikh strumіv to produce to shvidkogo ruynuvannya іzolyatsії cable. Through ce, far away, single-phase flickering becomes two-or three-phase, yelling at the switch-on of the house and intermittent electrical supply of the spozhivachiv. On the very cob, there is a nest of an arc, which step by step transforms on a permanent zamikannya to the ground.
If the strum crosses the zero value, the arc starts to rise, and then it reappears. At once, at non-shocking phases, the increase in voltage is increased, which can lead to destruction of the insulation of other plots. In order to extinguish the arc at the poshkodzhenny mіstsі, it is necessary to viskonat special come in for compensation of the єmnіsny strum. Z tsієyu method to the zero point of the merezhі is connected to an inductive grounding arc-extinguishing coil.
The circuit for switching on an arcing coil, shown on a small scale, consists of a grounding transformer (1), a vimikach (2), a voltage signal winding with a voltmeter (3), an arcing coil (4), a stream transformer (5), (6), a stream relay ( 7), sound and light signalization (8).
The design of the coil is made up of windings with a cold core, placed in a casing, lined with olive. On the head winding there is a ring, which gives five values of the struma for the possibility of regulating the inductive struma. One of the windings is switched on to the zero point of the transformer winding, closed by a star. In some windings, a special grounding transformer can be used, and the winding of the main winding is connected to the ground.
In this manner, for the sake of safety, not only the rozrahunok of the strumum is taken care of, but also carried out for the help of special outbuildings. In general, it gives good results and is safe safe operation electrical measures.
Electric fences can be used from a grounded or isolated neutral transformer and generator. Merezhi 6, 10 and 35 kV are operated from the insulated neutral transformer. Merezhi 660, 380 and 220 can be used both from insulated and grounded neutral. The largest width of chotiriprovidnі merezhi 380/220 grounded neutral.
Look at merezhi from insulated neutral. On the little one 1, a diagram of such a measure is shown triphasic struma. The winding is depicted in a stark way, everything that has been said below can also be seen until the winding secondary winding at the trickster.
Rice. Fig. 1. Scheme of a three-phase struma line from an insulated neutral (a). Flickering to the ground in a measure of isolated neutral (b).
In general, the isolation of the stream-conducting parts of the treadmill from the earth would not be such a garno, nevertheless, the conductors of the treadmill may make a connection from the earth. The star is of two kinds.
1. Isolation of the strum-like parts may be a simple opir (or conduction) in relation to the earth, which sounds like a mega-machine. Tse means that through the insulation of the conductors and the earth to pass the strum is not of any magnitude. With good insulation, the entire strum is more maly.
It is admissible, for example, that between the conductor of one phase, the earth voltage is 220 V, and the vimiryans with a megger opir іzolyatsії tsgogo drota 0.5 MΩ. Tse means that the strum to the ground is 220 phases 220 / (0.5 x 1000000) \u003d 0.00044 A or 0.44 mA. The strum is called the strum of the coil.
For clarity, on the diagram, the insulation support of the three phases r1 r2 r3 is depicted at the visual support, attached to the skin to one point of the wire. In fact, streams of a turn in the right line are distributed evenly along all the wires, at the skin line, the stench flickers through the ground that yogo sum (geometric, i.e., from the improvement of the phases) reaches zero.
2. A link of a different kind is established as a conductor in the line at a distance to the ground. How can you understand?
The skin conductor of the land can be seen by yourself as two. IN red lines conductor and earth - as a bi capacitor lining, and again between them - a dielectric. At the cable lines, the capacitor plates lived on the cable and that metal sheath, covered with earth, and the dielectric - insulation.
At changing voltage changing the charges of the capacitors caused the failure of the passage through the capacitors of the changed streams. This is how the names of the strums at the reference line are equally divided along the length of the wires and in the skin okremіy dilyantsi also zamikayutsya through the ground. On fig. 1, and the support of three-phase capacities to the ground x1, x2, x3 is mentally shown by applying the skin to one point of the line. What is the greater dozhina merezhі, tim great value strum a coil and єmnіsnі strum.
We wonder what will happen to the images of the little one 1, and the merezhi, as in one of the phases (for example, A) will appear flickering to the ground, ie. Such a vipadok is depicted as a little 1, b. Shards of opir between the wire of phase A and the earth are small, the support of the turn and the capacity to the ground of the phase are shunted by the support of the flicker to the ground. Now, under the influx of the line voltage of the line UB, a jet of a turn and an alternate jet of two right phases pass through the earth and the ground. The paths of passage of the stream are shown by arrows to the little one.
The flicker, shown on the little 1,b, is called single-phase flicker to the ground, and the emergency strum, which is the cause of this - strum single-phase zamikannya.
Let us know now that the single-phase fading of late insulation has become not directly on the ground, but on the body of such an electrical receiver - an electric motor, an electric apparatus, or on metal construction, for which laying electric darts(Fig. 2). Such a zamikannya is called zamikannya on the body. If so, the body of the electric receiver or the design does not tie the connection with the ground, then the stench builds up the potential of the phase of the wire, or close to new.
Rice. 2.
The dot to the hull is equal to the dot to the phase. Through the body of a person, її vzuttya, pіdlogu, the earth, the support of the coil and the єmnіsnі supports of the right phases, the closures of the lances are established (for simplicity, in Fig. 2, the mnіsnі supports are not shown).
The strum at this lancey zamikannya lie down as a support and you can get people of an important blow, or it will be fatal for her.
Rice. 3. Dotik people to the conductor in the measure from the isolated neutral for the presence in the measure of the earth
From what has been said, it is obvious that for the passage of the strum through the earth, the presence of a closed lansyug is necessary (and it is also said that the strum “goes into the ground” is wrong). At the wires from the insulated neutral, the voltage is up to 1000. The stink to lie in bed will become insulation and keep merezhi. Navіt rozgaluzhenіy merezhі stench znahodyatsya in the boundaries of a few amperes and lower. Therefore, jets, as a rule, are not sufficient for melting fusible inserts, or they are switched on.
With voltages greater than 1000, the main value may be small streaks, the stench can reach ten thousand tens of amperes (as a result, their compensation is not transferred). However, in these merezhakh, the switching on of the short-term connections during the single-phase flickering does not sound zastosovuetsya, so as not to interrupt the power supply.
in such a manner, in the measure from the isolated neutral for the presence of a single-phase flickering (which is signaled by the insulation control accessories) continue to operate electrically. It is possible, that in case of single-phase faults, the line (interphase) voltage does not change and all electrical receivers take energy without interruption. ale in case of skin single-phase shorting in the area with an insulated neutral, the voltages of the non-shocked phases increase to linear ones in relation to the ground, and in the event of a descent of another shorting to the ground in the other phase. Move on the earth, which has disappeared, creating a serious problem for people. Father, be merezha z nayavnistyu in nіy single-phase zamikannya is guilty of looking like that, scho is in an emergency station, oskolki zagalnі mind safety, for such a thing I will become sharply aggravated.
So, the presence of the "earth" is more unsafe with the dot to the parts, which are under tension. It can be seen, for example, from Figure 3, which shows the passage of the struma of the wound with a drop-down dot to the strum-guided dart of the phase A and the unburdened "earth" of the phase C. Lyudin, with whom, is reliant on the influx of the linear tension of the fence. That is why single-phase shorting to the ground or to the case is due to the shortest term.
Explanatory note.
Compensation of єmnіsnykh strumіv zamikannya the earth in merezh 6-35 kV.
Intro. The most common type of short circuit (up to 95%) at 6, 10, 35 kV lines is single-phase ground fault (OSZ), which is accompanied by the passage of a short circuit through the space of a small struma and overvoltages of high multiplicity on the elements of the line (motors, transformers) at high-frequency . So on the fence to produce at times until spratsovuvannya earthen defenders. In the event of a late arrival to laborious and trivial organizational tasks - later on, the admission is delayed for three times and is accompanied by a complex of operational shifts for the reservation of spares. I, as a rule, most of the interphase flickering is caused by OZZ. Rosvitok single-phase mic to the ground is accompanied by a rise in the time of the zamikannya, the rise of a large amount of energy in the area of the OZZ short chirp. You can change the situation with the help of resonant grounding of the neutral.
Strumi zamikanya. In case of OZZ on the ground through the space of ushkodzhennya, an ominous strum flows, noises are revealed by the electric capacity between the phases of the earth. The capacity is concentrated, more importantly, at cable lines, which are the most significant and signify a high-voltage strum of the OZZ (approximately 1 A of the streak falls on a 1 km cable).
See OZZ. Usі OZZ subdіlyayutsya on deaf (metal) and arc. The most frequent (95% of all OZZ) and the most with a careless look OZZ є arc OZZ. Describe the skin type of OZZ okremo.
1) from the point of the gap equal to the overvoltage on the elements of the merezhі, the most secure metal flickering to the ground (for example, the fall of the damaged power line on the ground). In this case, a small strum flows through the breakdown, which is not accompanied by great overvoltages due to the specifics of this kind of OZZ.
2) the peculiarity of arc SPZ - the presence of an electric arc in the SPZ area, as well as the high-frequency colivans, which accompany the skin SPZ.
Methods of strangling strums of OZZ. There are two ways to strangle the strums of the OZZ.
1) switching on the random connection - this method is direct manual and automatic (with the help of relay protection and automation equipment) shutdown. In case of any savings, it is possible to transfer to the category of reserve eating, or it is left without eating. There is no voltage on the weak phase - there is no struma through the breakdown space.
2) compensation of the strum in the area of the hum by a reactor installed at the neutral line, which may have inductive power.
The essence of compensating for minor strums of OZ. As it was observed, when the phase is switched to the ground (breakdown) through the space of the OZZ, a strum flows through. This strum, when viewed from the closest view, is charged with capacities of two (non-neglected) phases, which are left out, charged to a linear voltage. Strumi tsikh phases, zsunutі one shkodo one per 60 electrical degrees, summed up at the point of fluctuation and may by the magnitude of the loss of the value of the phase surge. The value of the stream of OZZ is determined through the space of ushkodzhennia: . The main strum can be compensated by the inductive strum of an arc-explosive reactor (DGR) installed in the neutral line. In case of OZZ in the middle on the neutral, whether there is a transformer attached to it, the windings of which are connected to the star, there is a phase voltage, yak, yakcho є vysnovok neutral, coming to the high-voltage winding of the reactor L, and inductive streak of the reactor through m. This directing strum is similar to the streak of the SPZ and can be compensated for in a similar setting of the reactor (Fig. 1)
Rice. 1 Ways for the passage of streams of the OZZ through the elements of the fence
The need for automatic adjustment in resonance. For reach maximum efficiency DGR circuit, the adoption of all the measures and inductance of the reactor - the zero-sequence circuit of the measure (CNPS) - there may be adjustments at the resonance at the frequency of the measure 50 Hz. In the minds of constant shifts at the railing (turning on / off switching off) the capacity of the railing is changed, which makes it necessary to stop the smooth-running DGR and automatic system compensation of єmnіsnykh strumіv OZZ (ASKET) lashing by hand, looking at the rozrahunkov’s data about the streaks of measure, and that’s not enough to get a resonant lashing.
Principle dії ASKET. KNPS is adjusted to resonance with an automatic adjustment of compensation type UARK.101M, which works on the phase principle. Reference signal ( line voltage) and the 3Uo signal from the winding transformer (for example, NTMI). For pravilnoї that stіykoї robot ascetic neobhіdno stvoriti boxed nesimetrіyu in MEREZHI scho robitsya Dzherela zbudzhennya neytralі (ІVN) - abo included visokovoltnoї kondensatornoї batareї in one of the phases MEREZHI, abo its orientation spetsіalnogo nesimetrichnogo transformer type TMPS іz vbudovanim ІVN (s mozhlivіstyu regulyuvannya koefіtsієnta transformatsії of discreteness of 1.25% phase voltage). In the rest of the fall, the magnitude of the voltage 3Uo in the resonance mode and the stability of the ASKET robots remain unchanged when the gauge configuration is changed (div. formulas below). At the neutral transformer, a DGR is installed (for example, of the RDMR type). Also, ASKET appears as a system TMPS + RDMR + UARC.101M.
About spіvvіdnoshennia values of natural and piece asymmetries. At the edge of the insulated neutral, the voltage on the NTMI open-circuited tricot with the improvement of the coefficient of transformation of the output stresses of natural asymmetry. The magnitude and cut of the voltage is unstable and fall due to various factors (weather, ... .. and so on), for the correct operation of the ASKET, it is necessary to create a more stable signal as in magnitude, and in phase. For which, a damaged neutral is introduced into the KNPS ( dzherelo piece unsymmetrical). As a way to win the terminology of the theory of automatic control, piece unbalance is a corny signal, which is to win for the control of the KNPS, and natural - a shift, as it is necessary to choose the value of piece asymmetry. At merezhakh with visibility cable lines with a small strum of 10 and more amperes, the value of natural unbalance is, as a rule, much smaller. Clause 5.11.11. PTEESiS combines the magnitude of the unsymmetrical stress (natural + piece) in the strings, as it works out of compensating for the sump, less than 0.75% of the phase voltage, and the maximum step of the neutral shift is less than 15% of the phase voltage. On the open tricot NTMI cі vіdnі vіdpіdatimu values \u200b\u200b3Uo \u003d 0.75V and 15V. The maximum level of neutrality in the resonance mode (Fig. 2).
We introduce below the formula for the expansion of the voltage 3Uo in the resonance mode for two ways of creating piece asymmetry:
1) at the time of the condenser Co
,
de-cut frequency of merezhi, 314.16 s-1,
http://pandia.ru/text/79/550/images/image006_44.gif" width="24" height="23 src=">- EPC phase, B,
http://pandia.ru/text/79/550/images/image008_37.gif" width="29" height="27">- coefficient of transformation by 3Uo of the winding transformer, in a measure of 6 kV - 60/, in a measure of 10 kV - 100/http://pandia.ru/text/79/550/images/image010_32.gif" width="97" height="51">,
de Ksm - changeover coefficient of the zsuvu phase For a special transformer.
From the formulas, it can be seen that in the case of a Co capacitor, the value of 3Uo at the point of resonance should be deposited in the streak line (), and in the case of a special asymmetric transformer, it should not be deposited.
The minimum value of 3Uo is chosen, depending on the mind of the best work, I will add UARK.101M, and become 5V.
In visceral formulas, the magnitude of the natural tension of the asymmetry of the measure is not protected through її small values. jpg
Rice. 3 Voltage vectors in the resonant-grounded array
Visnovki:
Accurate automatic compensation of the ¾mnіsny strumu OZZ є contactless arc extinguishing and in povnnіnnі z merezhy, scho pratsyut іz іzolovana neutralu, z resistively-grounded, zіstkovo kompensirovannaya, аlso іz іz kombinirovannoi
change the strum across the ground to the minimum values (near the boundary to active warehouses and other harmonics), ensure safe arc extinguishing (because of the three-valve flow of the grounding arc) and safety when the strum rises near the ground;
easing the windshield to the grounding outbuildings;
intermediary overvoltage, which is blamed for arc fault faults, up to a value of 2.5-2.6 Uf (at a compensation rate of 0-5%), safe for isolation of the operating line;
Significantly reduce the voltage stress, which is being changed, in the gradual phase, while reinforcing the electrical powers of the area of shock in the area after the skin lightening of the grounding arc, which is intermittent;
prefer handwriting reactive pressure on the dzherel zhivlennya for arc OZZ, which saves the amount of electricity from the survivors;
zapobіgaє razvitku in merezhі ferresonance processes (zocrema, mimoly zsuvіv neutral), yakscho vykonuyutsya zastosuvannya fusible zapobіzhnikіv on the power lines;
including the reduction of static resistance during transmission of tension along power lines.
When compensating for minor windings and cable lines, they can work for a long time with the phase that is closed to the ground.
Literature:
1. Likhachov to the ground in the nets from the insulated neutral and with the compensation of the strums. M.: Energia, 1971. - 152 p.
2. Obabkіv adaptive systems keruvannya resonant objects. Kiev: Naukova Dumka, 1993. - 254 p.
3. Fishman V. Methods of neutral grounding at 6-35 kV rails. The view of the designer. News of Electrical Engineering, №2, 2008
4. Rules technical operation electric stations and merezha Russian Federation. RD 34.20.501-vidannia. Moscow, 1996.
Lead Engineer
Rice. 2 Apply resonant indicators of KNPS
Rice. 4 Resonance grounded wire response to arc fault
