Single-phase shorting to the ground in meshes from an insulated neutral. Cause poshkodzhennya vl
Rozpodіlnі merezhi 6-35 kV are used in the mode from the insulated neutral. Electrical supply of spare parts is installed behind a three-wire system cable lines. Such a mode of work and neutrality allows you to increase the survivability of the life of the people for the songs of the day in the electric circuits.
So, for example, in case of a single-phase fault on the ground (such a short period of time takes up the largest number of mid-range), in the insulated neutral there is no emergency switching on of a damaged feeder. The line voltage is filled with the same voltage until one phase closes to the ground.
However, at single-phase flicker in the meshes from the insulated neutral there are processes that affect the operation mode of the electric mesh as a whole. The voltage on the low phase, fallow in the form of a fading, pragne to zero. In vibrations, if it is possible to show that the voltage on the phase is equal to zero, it seems that it is “all the earth”, and the zamikannya is called “metal”.
Symmetry line voltages when it does not collapse, and the axis of the phase voltage, two "healthy" phases rise to the level of the linear ones. At first, such a reapplied voltage can be shown on the vector diagram of the voltage tricot. With a change in the stress vector, for example, f. BUT, the stress vector f. IN ta f. W jump vector_voltage VAі SA.
The value of the struma, which flows through the mist, is found in the direct proportionate fallow in the value of the capacitance of the line and the applied voltage. The capacity of the line to fall due to its length and rozgaluzhennosti. This strum may be of small value, the proteo of such a mode is in a periodic ignition of the arc, which is intermittent.
When the arc rises, it’s easier, it’s bigger phase voltage, in another way, aperiodic warehouse strums appear, yak negatively pour into the camp of insulation and cable lines. In addition, the eminent nature of the arc is accompanied by the vision of heat that generates smart mind for the transition of a single-phase transition between phases.
Shifting the phase voltage of the "healthy" phases to the level of the line voltage, threatening breakdown of the weakened phase insulation of the other lines connected to these tires. Therefore, according to the rules of technology for the operation of electric lines, it is necessary to start negligently before turning on the power feeder.
For the exchange of strums, zastosovat on the ground in the nets from the insulated neutral arcing reactors(DGR). They are also called a cat to extinguish an arc, or a Petersen cat. The connection of the coil is connected to the neutral of the transformer connected to the tires of the compensated line. The principle of extinguishing the arc of foundations for mutual compensation of strums of an eminent and inductive nature.
Since the symmetry of the phase voltages is broken, at the zero voltage of the transformer of the coil there is a potential, the value of which lies in the nature of the earth fault: if the voltage is lower on the phase wire, then the voltage is higher in neutral, and the voltage is applied to the coil. Theoretically, the most ideal compensation for the strum mic to the ground can be reached by resonant adjustments of the GDR.
With such an inflated strum, the coils will be closer to the strum of the mic to the ground, and be in the opposite phase, with which full compensation of the strum of the mic can be reached. In practice, resonant adjustment of the DGR can not be reached, but it does not require such compensation.
On the right in that the number of phases repeated lines razrіznyayutsya iz-za raztashuvannya in the open space, visibly one of one. Lines, which can live with single-phase electric receivers, can be driven unevenly, and lead to the destruction of the symmetry of the system and the appearance of a potential in zero explorer coil transformer.
Taki asymmetric modes can bring to the superworld the work of arc-extinguishing reactors, and induce the vinification of resonant circuits. To turn off such situations, it is allowed to work with the robot in an undercompensated mode.
Compensation of strums zamikannya on the ground is transferred for such lines of strums: 6 kV - 30 A, 10 kV - 20 A, 35 kV - 10 A. it’s important that the arc doesn’t heal, otherwise it’s extinguished on its own, stosuvannya compensation in this way is not obov’yazkovo.
It is acceptable at point K (Fig. 6.9) at the edge of a dead-earthed neutral, a single-phase short circuit of phase A is connected to the ground.
For a single-phase short circuit, it is necessary to have a replacement circuit for direct, reverse and zero sequences, from which the values \u200b\u200bof,,, are assigned.
Rivnyannia (6.10) is supplemented by such three boundary minds:
Rice. 6.9. Schematic diagram single-phase short circuit
Symmetric warehouses of the struma at the slower phase with the improvement of the border minds:
(6.20)
tobto. 
.
In this order, strumi at the phases: ;;. Strum that flows through the earth: 
.
Voltage for low phase BUT:
Symmetrical warehouse voltage at the short circuit location:
(6.22)
Phase voltage in the short circuit area:
Virazi (6.20) and (6.21) allow you to induce vector diagrams of the stream and stress (Fig. 6.10). On the vector diagram of the voltage (Fig. 6.10b) kut θ between the stresses of non-shocking phases lie down in the vіd vіdnenja between them change in the ranges of 60° ≤ θ ≤ 180° . Lower boundary v_dpovidaє, Upper - at. prikut θ up to 120 °.
Rice. 6.10. Vector diagrams strumiv (a) and voltage (b) single-phase short circuit
Let us represent in the equation (6.21) the symmetrical storage voltages (6.10):
stars from the improvement of equality (6.20) are taken:
(6.24)
A complex substitution scheme that matches virase (6.24) can be seen (Fig. 6.11).
Rice. 6.11. Complex replacement circuit for a single-phase short circuit
Visnovki for the analysis of a single-phase short circuit
6.9. Two phase short circuit to ground
Let's go to the point Before(Fig. 6.12) at the rail with a solidly grounded neutral, there is a two-phase short circuit to the ground between the phases INі W that earth.
For rozrahunku Before(1.1) it is necessary to have a substitution scheme for the direct, reverse and zero sequences, from which the values of the supports of the direct, reverse and zero sequences are determined.
Rivnyannia (6.6) is supplemented by three boundary minds:
Symmetric warehouse voltages of phase A with boundary adjustments:
(6.26)
tobto. 
, stars 
.
Rice. 6.12. Schematic diagram of a two-phase earth fault
Three days off (6.10):
Oskilki strum phase BUT, then, substituting equality (6.27) in the rest of the spectrum, may be:
.
From the rest of the viraz we take:
Substituting the value of the virase (6.28) in the formula (6.27), after the transformation is possible:
(6.29)
Substitution circuit for two-phase short circuit Before(1.1), which confirms virase (6.29), is shown in fig. 6.13.
Rice. 6.13. Complex scheme for substituting a lansyug with a two-phase short circuit to earth
Strumi in advanced phases:
(6.30)
The modulus of virazіv at square temples at equal (6.30) warehouses:
Also, the absolute value of strums in low phases INі W sign up like 
;
.
Fallow vіd vіdnosin mіzh і value m(1,1) be in the range 1,5 ≤ m (1,1) ≤ .
Strum, which flows through the earth (and parallel way), will be:
.
(6.32)
Viraz (6.28) can be given in such a way:
(6.33)
The voltage of the non-shocked phase at the short circuit
Vector diagrams of the stream and voltage at the mist of a two-phase short circuit to the ground are shown in fig. 6.14. On the vector diagram of the stream, θ can be changed at the boundaries of 60º ≤ θ ≤ 180 º, pragnuchi to the lower boundary at that to the upper at.
Rice. 6.14. Vector diagr voltage (a) and strum_v (b) at dvof short circuit to earth
Visnovki from the analysis of a two-phase short circuit to earth:
The voltage of the low-phase phases in the short circuit is equal to zero and is significantly lower than the normal values in all CES.
The voltage of the non-shocked phase does not change and the rated voltage is increased.
At the system of electrical supply, streams of short-circuit currents of the sequences flow.
One of the main reasons for the disruption of normal work electrical installationsє short chimes. Short circuit (short circuit) - be it, not transferred by normal robotic minds, electrically connected between phases, and in systems from a grounded neutral (or some conductors) - one or more phases from the ground (zero wire) .
The zamikannya can be through an electric arc or without a middle (without a transitional support). In electric fringes, it is possible to see short flickering and flickering to the ground in the fallow mode in the neutral mode: three-phase short (symmetrical flickering of all three phases); two-phase (asymmetric zamikannya two phases); two-phase to ground (non-symmetrical muting); single-phase short (asymmetric zmikannya in merezhy іz grounded neutral); single-phase to the ground (at the lines from the insulated neutral).
Short-circuited streamers are switched on by a relay switch short term. Saszing the wings are not used 5 seconds, once ї ї is needlessly Ektrodinnamychniy Thrum_chnya Mozdali Seriesniki Plucodezhenna Ekletrobladnanna Ta Prikodnikіv, Scho Viklikyutn Vіdmov Basic Webidnavi Elektro Installations, Avaria on Elektrotanzi TA PІDSTANTSII, And Systems Systems Systems. Particularly unsafe short circuits on the buses of the stations and substations, as they often come through the dithering of the insulation and breakdown, damaged by the robotic relay protection switching equipment. As a result of which at the substations it is possible to vibuhi and burn, yak produce up to important lessons that trivalih interrupted in electropostachani. At short hums electric power transmission lines and being switched on by a relay switch can also be interrupted for a three-hour period of electricity supply (especially in the military on the lines without a backup meal), which is responsible for the great economic failure.
In case of a fault on the ground in the meshes from the insulated neutral, the robot is allowed to work until the end of the day. The ground fault mode is also not safe, the shards are accompanied by overvoltage, which leads to the two-phase (suspended) ground fault modes and that the switch-on is spozhivachiv. In addition, under this regime, the harm to people and creatures is blamed, and in the place of the tormenting of the earth, the harm is fired through an electric arc.
In the system of electric supply, the lines are reinforced with a voltage of up to 1000 less pressure. The sequence of interphases in the lines can be single-phase short circuits “phase - zero” and “phase - earth”. Qi poshkodzhennya is also unsafe, shards can be short interphase flickering.
It has been established that at the lines from the grounded neutral, single-phase short circuits become 65%, two-phase to ground - 20, two-phase - 10, three-phase - less than 5%. At the lines of the insulated neutral, the greatest number of warnings are observed during earth faults and two-phase short faults
Korotkі zamikannya in elektrichnih trammel poyasnyuyutsya rіznimi reasons: torn down їh іzolyatsії through atmosfernі that komutatsіynі perenapruzhennya and takozh її starіnnyam, mehanіchnimi poshkodzhennyami, poshkodzhennyami, viklikanimi tvarinami that Ptah, nacherkami on glass tubes storonnіh predmetіv, proїzdom pid lіnіyami oversized mehanіzmіv. arrow, combines, thinly), falling supports, shlostuvannya wires in the wind, ozeleditsa, "dance of wires" thinly. Often, the reason for the failure of the circuit can also be the wrong operation of the service personnel, for example, pardon the switching on of the lancers with a strum, the inclusion of the roses on the short, the pardon in the head circuits and the circuits of the relay protection and automatics, the inclusion of a short circuit grounding repair robots etc. The sooner the operation of the electrical installation is organized, the more likely it is to have short circuits. However, it is impossible to turn them off for the most part, having come to live, so that the stench would not be caused by the possession of those trivial destructions of yoga robots. Under an hour of short chimes through the great jets, the temperature of the jet-guiding parts moves, and the conductors and insulation are fluctuated. With this electrodynamic susilla, the electrical shock can be disrupted. Decreased voltage in the treadmill with a short flickering, a change in the moment of the electric motors of the treadmills, their galvanization and winding the teeth again, as well as the destruction of the robots of the other treadmills, which led to the inclusion of the treadmills. With a short fading, there is a strong electromagnetic surge on the line connection and the system of the air intake blocking.
Also, in order to minimize the negative consequences of short flashes, you need to learn how to identify the strumi k. Razrahunki strumіv nebhіdnі: for pіvnyannya, assessment and selection of the main schemes of electrical substations; choice of electrical appliances; assessments of the behavior of rescuers for emergency minds; designing and adjusting the attachment of the relay control and automation; design of grounding outbuildings; vznachennya vplivu strumіv up to. on the line link; selection of dischargers; accident analysis
To assess the thermal and electrodynamic injection of the strum of the short circuit, as well as for the specific step of the decrease in the voltage, it is necessary to know the maximum possible strum of the short circuit. at tsіy point merezhі. For rozrakhunkіv di ії relay zakhistu and її succesfull ї work in the most folded minds, they also sign the minimum stream of k.z.
In Denmark, rіven strumіv k.z. for merezh suttєvo poddvischivsya. For a measure of 35 kV and more, it is necessary to combine the parameters of the electrical devices, transformers, conductors and other electrical control, the minds of the security of the stability of the power system, and for the measure of 3-20 kV - the parameters of the electrical devices and strumoprovodiv, thermal stability of the cable
For obmezhennya strum_v k.z. vicorist sectional mesh, install transformers with split windings lower voltage, strumoobzhuvalny reactors Zastosuvannya dermal method can be economically primed.
Sectional mesh efficient way, Scho allows you to change equal strums to. at 1.5 ... 2 times. At 10 kV separate lines, there are widely used separate busbar sections, as a way to eat different transformers in the substations. However, in this case, there are shortcomings: different equal voltages behind the sections, unevenly driven transformers.
In power transformers with a voltage of 25 MVA and more vicorous windings, the lower voltage is split on the two, which allows you to increase the support of the transformers in the short circuit mode. about 2 times.
Reactors serve as an exchange of strum_v k.z. at tight electrical installations, as well as for trimming on selected tires with a significant excess voltage. Їx zastosovuyut mainly in electrical lines with a voltage of 6-10 kV, above 35 kV and higher.
In domestic energy systems electrical networks A voltage of 6-35 kV is used, as a rule, from an insulated neutral or from a neutral grounded through the great inductive support of the arc-explosive reactor (DGR), as well as from grounding through the great active support. On the view of the line with a dead-earthed neutral, single-phase flickering in the line with an insulated neutral is not accompanied by the appearance of great short-circuit strums, the streaks of the strum flicker to the ground through the arc great pillars capacity of the phases of the mesh.
Let's look at the nature of the change in the voltage and flow of the wires and their vector diagrams in normal minds and with a single-phase earth fault (K3 (1)) in the mode, if the neutral wire is insulated, closed through the reactor, to be extinguished, or through an active resistor. For forgiveness, we accept that the need for a measure is daily. This allows you to enter the voltage phases at all points of the network with invariable and equal EPC phases of life. In Fig. 9.1, a radial line is drawn from an insulated neutral with a lifeline (a generator or a step-down transformer) and one equivalent power line, which mentally represents the entire line. The capacity of the phases of the earth was changed, replaced by an equivalent ground capacity W 0.
Opir Rі X LEP do not cheat. The city of zherel zhivlennya is also not insured against the loss of small significance.
In normal mode wire voltage BUT,INі W by relation to the earth equal to the corresponding phase voltages U A, U b, U C E BUT, E IN, E C.Vector of phase voltages symmetrical star(Fig.9.2, but), and їх sum is equal to zero, after which the voltage in the neutral N per day: U N = 0. Pіd dієyu phase naprug through єmnostі phases schodo zemli W BUT, W IN, W To pass streams that increase the phase voltage by 90 °:
The sum of the small streams that pass through the phases in the normal mode, up to zero, and volume 3 I 0day (fig.9.2, but).
Metaleve earth-flickering of one phase in the measure from the insulated neutral. It's possible that the phase is messed up BUT(Div. fig.9.1), then the phase voltage of the earth is reduced to zero ( U A = 0). Neutral voltageU N(1) U N = U KN (Fig.9.1 and 9.2, b), then. voltage, which is higher for the values and the reverse value for the sign of the grounded phase:
(9.2)
The voltage of the non-corrected phases how much the earth moves to the interphase values U
B(1)= U
BA ta U
Z(1)= U
SA. The interfacial voltage is constant, as can be seen from Fig. 9.1 and 9.2.
In Fig.9.2, b a vector diagram of the voltage of wires and neutral wires along the distance to the ground ( U B(1), U Z 1), U N): dots BUT,IN,W represent wire potentials, dot N confirming the neutrality of life, full stop BUT tied from the earth and has a zero potential.
Strumi when zamikanny on the ground. The mischief is in trouble Before to pass streams that are zipping through the containers of non-shocking phases of the merezhі (9.1). Oskilki U A = 0, then I A(C) = 0. In the other two phases, the voltage U" Bi U" There are streams that viperedzhayut on 90 ° qi of the voltage:
Strum I s(C) more money strum in the phases INі W(Fig.9.1): I h(C) = ( I B(C) + I C(C)). Z urahuvannyam (9.3)
Oskilki U BA + U CA=-3 E A (Fig. 9.2, b):
In this rank, strum I s(C) is equal to the loss value of the normal eminent strum phase I f(C) = U f / X C . From Fig. 9.2 b you can see that the strum I h(C) vperedzhaє vіd U N by 90°. Strum I s(C) can be assigned to the formula
De l- zagalna dozhina odnієї phase merezhі; W ud - area 1 km of the phase of the earth.
At the countermeasures I h(C) to be found in the boundaries of the chasts up to dekilkoh tens of amperes; for cable ones - in the number of amperes up to 200-400 A in large cities.
Strumi and zero-sequence voltages when flickering to the ground. In case of ground faults at phase voltages and streams, warehouses of NPs appear:
(9.5)
(9.6)
Substituting(9.5) values U " In i U " W , acceptable
(9.7)
Shards of opir wires are significantly smaller XЗ, at all points of the line U o= U OK. Strumi I 0 U oK, they flicker through the phase capacity and ground zero points of generators and transformers, which are also grounded. Z rozpodіlu strumіv I 0, shown in Figure 9.3 following:
De U f - normal voltage urogenital phase.
From the point of view, it is possible to make a visnovok, which is a clear strum at the mist
(9.9)
Strumi 3 I 0(C) and I z(C) move in phase and outpace the stress vector.
Compensatedmerezha. Let's take a look at the neutral, which is grounded through the arc-extinguishing reactor DGR, for the purpose of compensating for the small blasts at the power supply (Fig. 9.4). In case of earth faults, the voltages at all points of such a measure may have the same value as at the measure from an insulated neutral. For the presence of DGR pіd diєyu voltage U OK = U N=- E Vinicaє inductive strum I DGR, which passes through the phase, which is closed to the ground BUT Poshkogenoy LEP W1 until the moonlight Before and on the ground turn to DGR:
I DGR = -E BUT /X DGR Cey strum superimposed on the strum I s(C) - Being inductive, I GDR prolongation by phase I s(S) - Resulting strum
With a new compensation, how should you start to secure, I DGR = I s(C) = 3 E BUT ωС 0, and then the resulting strum I h=0.
Єmnіsny strum NP I 0(С) (fig.9.4, but) to go through all the non-sheds and the poor LEPs. Strum I DGR is less likely to pass on a random admission W1. Strum I 0 in the windings of the generator during the day, the zero point of the zero point is isolated. In non-student LEP ( w n) the sum of the phase strums in case of a fault on the ground I 0(C) W Toki I 0(C) W n directing to busbars, their values are determined by capacities C0 LEP:
Poshkodzhenіy LEP W1 at the distance from the busbars of the substation to the point of closing Before strum 3 I 0p.l more than the total strum ∑3 I 0(С)∑ = I s (C) at the mist's money for virahuvannyam strumu
Strum 3 I 3 I 0(С) for non-student LEPs.
For the presence of the DGR strum on the cob of the poshkodzhenoy LEP 3 I 0p.l. I DGR of an arc-explosive reactor and a total ½mnіsny jet of non-shocking power transmission lines:
With additional compensation I DGR = ∑3 I 0(С)np.l i todi
(9.13)
Later, at the compensation line on the cob of a poshkodzhenoy LEP (between the tires and the dot Before) to pass the superfluous inductive strum of the DGR, numerically equal to the strum of the poshkogenoy LEP ( W1 in Figure 9.4). Directly to the strum in case of full compensation of spivpadatme with a direct strum in non-shocked LEP. Rozpodil strumiv I 0, the indications in Fig. 9.4, are valid for any values ω , then. for all harmonics (crim of multiple triplets) strums I 0і I f
.
Strumi in the measure active support. In parallel with the arc reactor, a resistor is switched on R(Shown by the dotted line in Figure 9.4). Todi, krim strumiv I 0(C)i I DGR, the third strum is coming I R = U OK/ R, which runs in phase z U oK and failures by 90° in relation to strum I 0(C)i I DGR. In this rank, for the presence of the resistor R strum at the misery
(9.14)
When flickering to the ground through the transitional opir voltage of the weak phase U A= I 3R n = U OK , and the voltage in neutral U N=- E A+ U K, tobto. it appears smaller, lower than the metal zamikanny. The stress of the non-shocking phases of the earth, as well as the strumi, is apparently changing I 0 ta I 3. Strum
In rozrakhunkas, there is a decrease in the struma and the voltage of the NP, equipped with a support R p, to be protected by the coefficient of repeatability β = U OK / U f . With metal fading β = 1, shards U OK= U f. With an inconsistent zamikanny on the ground U ok = β U F, strum I 0= β U f/ X C and strum
Table 1.5
The main regulatory and legal basis for diagnostic control of high-voltage electrical control can be changed from the improvement of the essential GOST 27.002-89.
The zamikannya, which is blamed on electrical framings, machines and apparatuses, is distinguished by great variability, as it looks, so it is behind the nature of the frivolity.
To simplify the analysis of the analysis of the behavior of the relay protection in case of ushkodzhennya, okrem factors are included, which is not essential to add to the magnitude of the stream and voltage. Zokrema, as a rule, is not immune to the transitional opir at the mist, and all poshkodzhennya look like a “deaf” or, as it seems, “metal” phase connection between themselves, or the earth for the measure from a grounded neutral. Opir of all three phases are considered the same.
1.2.1 Vidi short chimes
The main chime is shown in fig. 1.21. Interphase short circuits - three-phase and two-phase ( but, b, in) - they are blamed both at the treads from the grounded one, and in the treads from the insulated neutral. Single-phase short circuits can only be connected in strings from a grounded neutral ( G). At the railings from the insulated neutral, single-phase short circuits to the ground (OSZ) are introduced ( d).
The main reasons for crying out the noise on the lines are the overlapping of the insulation during the hour of a thunderstorm, the shaving of the wires during the cold weather, the handwriting, the overlapping of the polluted and the allowance of the isolation, the pardons to the staff and the іn.
1.2.1.1 Three-phase short circuit
A symmetrical three-phase short twitches are the simplest type of fluctuation for analysis and analysis. Vіn characteristic tim, scho strum and the voltage in all phases is equal to the value of the yak in the short circuit, so in any other point of the measure:
I A = I B = I C; U A = U B = U C.
The vector diagram of the surge and voltage at a three-phase short circuit is shown in fig. 1.22.
The shards of the system are symmetrical, the strum, which passes at the skin phase, which is visible from the EPC, which creates yoga, to the same cut φ short circuit the spivvіdnennia of the active and jet bearings of the lancet of a short zamikannya:
For lines up to 35 kV, sound less than 45 °.
The voltage at the short circuit point is equal to zero, and whether there are any other points of the measure, it can be determined, as shown in Fig. 1.22 in. So Yak Vio Faznі І Mіzhfaznі'sfts in the mіstsi of the triphase short zimicanna Rivnі zero, and at the points, Vіddenih Vіd Mіstsya kz on the small way of Vіdstan, slightly per magnitude, view of the scenery, scho otzayudsya, represents the nib_lsu sky for Robot Energosysystem robots and generators and electric motors.
1.2.1.2 Biphasic mic
Mickannya two phases. With a two-phase short circuit of the strumite, the voltages of the different phases are not the same. We can look at the spivv_dnoshnenya strumіv and naprug, typical for a two-phase short circuit between phases B and C (Fig. 1.23). In the late phases, the same strums pass in the mid-short circuit, and in the non-short phases, the strum is daily
I A = 0; I B = -I C.
Interfacial voltage Ubc at the mist the short circuit is equal to zero, and the phase voltage is determined by the formula:
U B = U C = E/2, U B C = 0.
So it’s just like in case of a three-phase short circuit, strums, which pass in the low phases, stand in the EPC, which creates them (in this situation E sun abo parallel youmu vector U sun on kut φ short circuit is assigned to the spіvvіdnoshennyam active reactive supports lanceug).
Vіdpovіdnі vіdnі іn_diagrams on miscі KZ pobudovanі in fig. 1.23. At the world in the distance in the place of short circuit phase voltage U V , U W that interfacial voltage U sun zbіshuvatimutsya, as shown in Fig. 1.23 dashed lines for a point n.
From a glance at the stability of the parallel robot and generator and the robot of electric motor analyses, the type of ushkodzhennya becomes significantly less unsafe, lower three-phase short flickering.
Short circuit of two phases to the ground in the distance from the grounded neutral. At the wires from the grounded neutral, the two-phase short circuit to the ground is significantly unsafe, the lower two-phase short circuit. This is explained by the more significant decrease in interphase voltages at the short circuit, since one interphase voltage changes to zero, and the other two - to the value of the phase voltage of the non-eared phase (Fig. 1.24).
Spivvіdnoshnennya strumіv i naprug mіstsі short circuit for the first kind of poshkodzhennya may look like this:
I A = 0; U B = U C = 0.
This type of protection for the mesh from the insulated neutral is practically not affected by a two-phase short circuit. Strumi, what to pass in the area of short circuit and in the circuits of the circuit, what can be seen, as well as interphase voltages in different points measures may have their own meaning, which is the case with a two-phase short circuit.
1.2.1.3 Single phase short circuit
Single-phase short-circuit in the line from the grounded neutral. A single-phase short circuit can be less common in the strings from a grounded neutral (in Russia, as a rule, from a grounded neutral, strings with a voltage of 110 kV and more are used). The vector diagrams of the flow and voltage at the mist of a single-phase short circuit of phase A are shown in fig. 1.25 but formulas that signify their main characteristics:
UA=0; I B = I C = 0.
Single-phase short circuits, which are accompanied by a decrease to zero in the case of a single-phase voltage fluctuation, become less unsafe for the normal operation of the power system, lower are considered more interphase short circuits.
Single-phase earth flicker at the fence with a small strum earth flicker. At the strands with small strumas, there is a short circuit to the ground, up to which one can see a fringe of 2-35 kV, which works from an insulated neutral or from a neutral grounded through an arcing coil or a resistor, the flicker of one phase to the ground is accompanied by significantly smaller struma, the flicker is short.
When one phase is shorted to ground, the voltage of the damaged phase is (U A in fig. 1.26 but) where the earth becomes equal to zero, and the voltages of the non-shocked phases U Bі U C increase by 1.73 times and become equal between phases U B (1)і U C (1) in fig. 1.26 b.
Pіd diєyu voltage U B (1)і U C (1) pass strum through the place of ushkodzhennya I G A, which flickers through the reservoirs of non-fluid phases and C. The reservoir of the non-fluid phase is shunted by the mimic, and therefore the strum cannot pass through it. The magnitude of the strum in the area of the earth is measured in the following way:
de X∑- sumar opіr lancer zamikannya on the ground.
Scatters of active and inductive supports of generators, transformers and cable lines are much smaller, the lower ones are of lesser support, they can be overpowered. Todi
de C - the capacity of one phase of the earth.
Shards in case of phase A fading to the ground of the voltage of the phases і Z schodo zemі rіvnі for the value of the interfacial voltage і zsnutі on kut 60 °, then
U B (1) + U C (1)= 3U FA .
As a result
I ZA \u003d 3U fA ωС.
The locality of the border is mainly determined by the old arrival lines. For redundant lines, you can take the following values of єmnіsnyh strums: 6 kV-0.015 A/km; 10 kV-0.025 A/km; 35 kV-0.1 A/km.
OZZ is the most common type of ushkodzhen at 6-35 kV fencing (75-90% of savage number electric ears). They often lead to great accidents, which are accompanied by significant squabbles.
1.2.2 See ushkodzhen pіd h OZZ
In case of OZZ, it is possible to get worse, if at a glance you can subdivide into a sprat of the main categories:
Short-hour breakdowns;
- "metal", arcless OZZ;
OZZ through the great transitional supports;
Arc OZZ;
Obrivi PL, who are not accompanied by trivalid OZZ.
Short-hour trials. Most of the "stable" OZZs are replaced by short-hour non-stable breakdowns of insulation trivality of 1 to 10 ms, which are accompanied by significant interruptions for trivality without streaks (of 1 to 17 quilins). An hour from the first short-hour breakdown to a stable OZZ should be set from 1 hvilin to 10 decibels and more.
Bezdugov OZZ. This kind of humming occurs at the time of the fault of the superficial galvanic connection of the damaged phase from the ground (for example, from the grounded housing of the electrical installation). With any voltage and zero-sequence streams, you can enter sinusoidal and maximum values. At a glance, the arc-free OZZ is the simplest mode of operation.
OZZ through the great transitional supports. The connection of the phase with the ground through non-metal objects (for example, through the wooden parts of the structure, when falling on the dry soil is too thin) can sometimes be brought up to the OZZ with a great transitional support. So, in the experiment, when a 35 kV power transmission line was dropped, a transitional opir was indicated on the sand, which changed approximately from 7 to 5 kOhm in a few seconds. In Poland, the value of such a support is normalized to be 13.5 kOhm, in Canada - 7.5 kOhm. Taki great values the transitional supports can easily reduce the vimogi to the point of overstretching the lines of the OZZ;
Arc flicker. Beware of breakdowns and phase insulation overlaps. In this case, a “pererivchast” form of a crooked strum in the tube is often suspected. Such an arc is called interleaved. With this strum at the relay, at OZZ, you can interrupt for some hour and take revenge on the great number of high-frequency warehouses.
In some fluctuations in the strum and the tension of zero sequences, the same subharmonious warehouses can be blamed.
The arc, which is to blame for the fault, can sometimes be interrupted for a significant hour, which shifts a few periods of the industrial frequency. Visove zoiszti Tivanosti Tsoledivoye Pause, povodvostii zi-aleny charge єmnostі sampling Fazi Pisl Zgasennya Arci, Vіd Paramerol Merozі, Slіduє, Scho Entered the grounding resistor, etc. Schoshu Tryvali by Takuzi, Schu positively acquainted on the lead to the ground.
Significant instead of high-frequency warehouses in streams of zero sequence, like a randomized, so non-splitted submarines can be brought to a non-selective robotic zakhist. Streaks of zero sequence, for example, of non-shocked submarines can, in some cases, overwhelm the watery streaks with metal OZZ. This is explained by the fact that high-frequency warehouses in a voltage of zero sequence, like, zocrema, are generated by an arc, a significant world is swelled in the lower streams of the lines, the shards of the lower opir change in proportion to the increase in frequency. As a result, the streams in non-shocked lines can be easily relocated by the double streams assigned to the metal OZZ, for which the settings are being checked for protection.
Obrivi PL, who are not accompanied by trivalid OZZ. Sometimes, in the 6–35 kV lines, faults are blamed for not producing a zero-sequence stream to a trivial overshoot, but even as a “summary” of the OZZ, for example, shaving the plume on the submarine. If the plume hangs, not sticking out of support, then the strum of zero sequence per day, and the normal protection from the OZZ does not work. When blown by the wind, the plume can briefly zamikatisya on the support, which will lead to "beaking" zakhista, but if you spratsovuvannya do not sound through the shortness of such a zamikannya.
OZZ features in fallow in line design and modes of operation. The great injection into the behavior of defense against OZZ is given by the scheme of the merezhі, modes of work and constructive vikonannya lines. It is obvious that OZZ processes proceed in a different way at the lines with repeated cable lines.
OZZ in cables made of plastic insulation, when finishing with large streaks, often lead to a stable high arc. For the quiet minds of the OZZ at the cable with paper insulation, leaking oil-rosin mastic, sound to bring up the oli and that boisterous vision of gases. The turbulent flow of gases in the gas mіkhurі, which, having settled down, causes the arc to go out, away from the flames, which seems to be more likely after the “rozmoktuvannya” of the gases, which have disappeared.
Obviously, when different values struma OZZ in other phases of the development of the process of trivality of the mountain arc and the trivality of streakless pauses can change. At the link, for example, the transition at the cable lines from the mittevo of the air defenses to the OZZ up to the time, to make a windshield for an hour, you can bring it up to the winds in quiet weather, if the trivality of the mountainous arc becomes less for a windshield for an hour.
In the episodes of the OZZ on the submarine for the obviousness of the soundless pauses characteristic of the arc, which intersperses, standard scheme the security of the vitrimms can be actuated for an hour, the shards for an hour without a pause of a pause of the stench “throw off” the freeze after an hour, - the relay (or block) of the vitrimki is rotated for an hour at the exit camp. For uninterrupted functioning of the zahist, it is necessary to ensure the "remembering" the actual hour of the fact of the launch of the zahist. As if by stretching the established hour of memory, the strum of zero sequence appears again, the Zakhist is guilty of spratsovuvati.
In the case of OZZ on double-sided submarines between two lancets of the same submarine, connected to different sections, there is a connection through the intermediate spaces. In case of OZZ on one of the lanes, the voltage of zero sequence vinikaє on both sections of the selected tires, and the stream of zero sequence flows through the lines, adjoining up to one section of the selected tires of the substation, and so on. However, it is not possible to reverse the peculiarity during the development of the design, it is possible to non-selectively include non-shocked lines in the case of OZZ in the border.
In some 35 kV lines, there are lines of operation of vikonan without transposition of phase wires. Whom blames the asymmetry of the phase capacities of the earth, which causes the displacement of the neutral lines, i.e. the appearance of a voltage and a zero sequence for the current of the OZZ. Installing a grounding resistor in the neutral changes the voltage, prote in the protection from the OZZ is an additional strum, which is the next step to reverse the settings.
If, in the range of 6-10 kV, as a rule, it is necessary to install cable transformers with a zero-sequence stream, in order to cause a slight unbalance in the normal mode, then in the range of 35 kV, sound for protection from the OZZ, it is possible to vicorate filters from three transformers into the stream, the unbalance of which can be in deyakyh vipadkah duzhe great. If you don’t cheat on the hourly adjustment of the settings, then you can non-selective spratsovuvannya.
Modes of operation. Streams of zero sequence can change during the operation process due to the following reasons:
As a result, the inclusion of four lines and a jumper in the circuit, for example, in the process of exploitation;
Pіd hour vіmknennya linіy, priєdnannyh to the bus station pіdstantsії or rozpodіlnogo item, after repair. In case of this, they can change the exact same way between the strum and the elastic zero sequence in the sloping line;
When replacing part of the damaged line cables;
Due to the presence of an arc-explosive reactor connected in parallel with a grounding resistor, the operating personnel do not start a vicorist autopilot, it’s supposed to be. With every possible mode of suttvoї overcompensation, scho complicates the work of the greater number of protections in the form of OZZ.
Injection of the voltage transformer pid hour OZZ. In fact, more than once they were afraid of the spratsovuvannya zahistivniya neushkodzhenikh lines after the connection of the line with OZZ. One of possible reasons such a non-selective spratsovuvannya є those that the voltage transformer (VT) in the process of OZZ accumulates energy, which after the inclusion of a faulty line begins to be exchanged with the capacities of the non-shocked lines. When directly, the magnitude of the streams near these lines stench is consumed near the zone of spratsovuvannya zakhistu, after which the zakhist vіd OZZ diє on vіdklyuchennya non-selectively. The presence of the grounding resistor helps in time, the chips accumulated in the TN, the energy is clearly seen in the resistor. Dodatkovym entry, which allows you to see such non-selective spratsovuvan, є zaprovadzhennya vitrimka hour spratsovuvannya zakhistu.
OZZ heritage. Flickering phases to the ground in the voltage range of 6-35 kV can lead to such unacceptable consequences:
Overvoltages are close to 2.4–3.5 times parallel to the phases at the rail, which can lead to a breakdown of the insulation of non-shocked phases and the transition of the OZZ at the “double” or downlink to the ground due to its characteristics, close to two-phase short circuits. Rizik vyniknennya such subvіynyh zamіkan pomitno virіs the rest of the hour at the link with the old isolation electrical machines that equipment of rich energy facilities and the cost of their modernization and replacement;
Possible manifestations of ferresonance, such as those at the lines that are looked at, most often go out of tune with voltage transformers. In some cases, power transformers are weakly energized, which work in a mode close to idling;
Nebezpeka razhennya people and creatures electric jet- on submarines, OZZ is often seen when shaving the dart and falling on the ground. Such a concern is especially great, as a submarine should pass through densely populated areas, for example, in a locality;
Breakdowns of the insulation of the motor stator winding on the stator metal often occur through an arc and can lead to significant damage not only to the winding itself, but also to the stator lag (called "pozhezha zazhezha"). "Perіzhzh" _izoljatsії to produce before the appearance of unsafe coil or interphase short flicker. In case of any “secondary” breakdown of insulation, which is to be blamed for appearing in a measure of 3-10 kV OZZ, it will appear on the motors itself, the shards of their insulation will sound like the insulation of the submarine of that other property. It is necessary to produce up to significant vitrates, due to their repair and simple winding mechanisms. In this case, the engines are switched on by defenders in the interphase short circuit. It is clear that the majority of these short circuits are blamed as the consequences of the OZZ, it becomes obvious that, having installed an effective protection of the OZZ in the measure, it is possible to sharply shorten the number of short circuits on the engines and the beats that accompany them;
It is possible to break the concrete support in the area of the ground from the ground when the phase insulation is crossed on the reinforcement of the concrete support, so the submarine is not connected for a long time. As a result, the support wastes its power;
In the wake of the troubling piercing of the struma of the OZZ, the soil was the support hanging, the growth of the opir, in the wake of which there is an increase in the insecurity of people’s wounds with a crock of tension or an elastic dotik;
There is a possibility of a vindication after that, as the OZZ is not switched on for a long time, for example, at the middle of the switchgear, through the vysokotempertny arc at the OZZ area;
In the rest of the hour, a significant number of imported cables were put into operation near the Russian energy systems, and a great amount of sheathing (armor) was put into operation by some rich conductors, such as a small total span. For example, with a cut of a three-phase cable 70 mm 2, the overcut of the armor becomes close to 20 mm. When vinicated "rich" flicker to the ground, the outer shell is strongly overheated and screams to burn, that it is curving. plastic insulation;
In case of arc flashes on the submarine, significant transitions are made in the vicinity of the communication lines (for example, telephone).
1.2.3 Analysis of the wear resistance of 110 kV substation
At the department of ECCIS ІRGTU, a work is being carried out for the purpose of the assignment on the lines of the PL 110 kV of the branch Electric lines (WEC) of the BAT "IESK".
WEIGHT will provide electricity to a large territory, as it stretches out regional center− Irkutsk area − more lower by chotirista kilometer on pivnich and bordered by the right bank of the Angari river, the western shores of Lake Baikal and the basin of the Lena river and its tributary. The area of the "spill zone" WEIGHT should be over 120 km2. WEIGHT zdіysnyuyut elektroprostachannya 9 administrative districts in the region and the national autonomous okrug. The main heads of the WEC are more and more uninterrupted power supply to the population, objects of the social sphere, enterprises and organizations.
Rivne poshkodzhennya PL 110 kV richly vischiy lower at the reshti branch of BAT "IESK". Zvichayno blaming nutrition about the causes of increased earache.
For the period from 2002 to 2011 (Tobto for 10 years) 13 lines of 110 kV have become 658 poshkodzhen. Pithomy rіven ushkodzhuvannostі becoming 0.0753 shkodzhenya per 1 km of the length of the substation 110 kV on the river, then on the river in the middle fall 1 shkodzhenya on the skin 13 km of the substation 110 kV. The reason for the advancement of the rіven of ear-juvation, but not the foreign one, is to unambiguously allow for the manifestation of particular causes of ear-juvation. The presence of such causes in the singing world is confirmed by the equally equal rozpodilom of the day, which we have seen, along the old lines.
More important is the poshkodzhen - tse short circuit, yakі stumbled on the fleetingly that lines were lost in the robot for the successful operation of the automatic reclosing (AR). The place of the worn-out short circuits was often not revealed by the staff, to which the CRAP’s attachment was shown, showing the place in the lines with great mercy through pardons and the hour of introducing the external information after the ignorance of the rozrachunk method embedded in this attachment. The pardon was revealed in the course of work, by a team of students, graduate students and candidates of the department of ECCIS IRDTU.
The analysis of statistical data about short circuits on 110 kV lines for 2002-2011 was carried out. Filed on fig. 1.27 and 1.28 data show that the increase in the number of short circuits falls on summer months rock (cherry, lime, serpen) and in the early years from 5 to 7 years. At the same time, fate and achieve the most intense fog, dew and vaporization of water from hollows, bright, flooded rivers. These short circuits are not stable, the shards of an electric arc, passing through the garland of insulators, dry out, and the PL under the APV re-opening under the voltage.
Vikonano also analyzes the distribution of short circuits behind the old submarine 110 kV "Ust-Orda - Bayanday" (Fig. 1.29) and other lines WEIGHT.
The analysis showed that the short circuit was broken according to the old substation 110 kV to fall into natural minds Mіstsevosti roztashuvannya linії. The largest influx on the growth of the KZ is due to the expansion of the lines near the swampy moors or the air of the valleys of the rivers.
