CN110086160B - Method for eliminating residual current of ground fault of neutral point arc suppression coil grounding system - Google Patents

Method for eliminating residual current of ground fault of neutral point arc suppression coil grounding system Download PDF

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CN110086160B
CN110086160B CN201910356814.1A CN201910356814A CN110086160B CN 110086160 B CN110086160 B CN 110086160B CN 201910356814 A CN201910356814 A CN 201910356814A CN 110086160 B CN110086160 B CN 110086160B
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fault
passive element
phase
ground fault
zero
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CN110086160A (en
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杨磊
叶茂泉
杨正昌
欧阳玲
罗俊杰
向齐光
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Guangdong Power Grid Co Ltd
Dongguan Power Supply Bureau of Guangdong Power Grid Co Ltd
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Dongguan Power Supply Bureau of Guangdong Power Grid Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/08—Limitation or suppression of earth fault currents, e.g. Petersen coil

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Abstract

The invention discloses a method for eliminating ground fault residual current of a neutral point arc suppression coil grounding system, which comprises the following steps: step 100, measuring three-phase voltage and zero-sequence voltage of a power distribution system, and detecting a ground fault and a fault phase; step 200, when a ground fault occurs, putting a passive element into a lagging phase of a fault phase to suppress fault residual current to zero; step 300, delaying a set time, changing the value of the input passive element, if the zero sequence voltage changes according to a corresponding rule, indicating that the ground fault is eliminated, quitting the input passive element, and recovering the normal operation of the system; otherwise, judging as a permanent earth fault, and returning to the step 200; when a ground fault occurs, a passive element is added to suppress the fault residual current to zero, the value of the passive element is irrelevant to the ground resistance and only relevant to the parameters of the system, so that the suppression effect is not influenced by the fault resistance, the suppression effect is good, and the method has the characteristics of simple and reliable operation, convenience in adjustment and low cost.

Description

Method for eliminating residual current of ground fault of neutral point arc suppression coil grounding system
Technical Field
The invention relates to the technical field of power distribution systems, in particular to a method for eliminating ground fault residual current of a system with a neutral point grounded through an arc suppression coil.
Background
The structure of the power distribution system is complex and changeable, the connection with users is tight, and random faults are easy to occur, wherein about 70% of faults are instantaneous ground faults, and the ground fault current suppression technology is a difficult point and a hot point problem in the research of the power distribution system.
In order to limit the grounding fault current, the power distribution system in China generally adopts a mode that a neutral point is grounded through an arc suppression coil, and the grounding fault current is suppressed by compensating the capacitance current in the grounding current, so that the short-time operation of the power distribution system with the fault is realized. However, with the increase of cable networks and the massive access of nonlinear loads and power electronic equipment, fault current contains a large amount of active components and harmonic components, while the traditional arc suppression coil can only compensate reactive components in the fault current, cannot compensate active components (about 2% -8%) and harmonic components (about 5%), and partial power distribution network ground fault current still reaches dozens of amperes after compensating capacitance components through the arc suppression coil, is enough for maintaining arc combustion, does not meet the requirement of power grid regulation operation, cannot be used for intermittent arc grounding fault caused by insulation fault, has limited suppression effect, is easy to generate overvoltage which can reach 7 times of rated voltage to the maximum extent, is easy to burn high-voltage electrical equipment, even causes fire connection accidents, and causes large-area power failure.
Therefore, research on an active arc suppression method for suppressing fault current and voltage is started at home and abroad, and for example, in a text entitled "full compensation technology and application of a ground fault neutralizer", published by Swedish Neutral corporation in sweden 2015, an active current arc suppression method is disclosed: when the earth fault occurs, the earth residual current is taken as a control target, the current is injected to a neutral point through the residual current compensator, and the earth fault total current (including reactive component and active component residual current) is compensated, so that the aim of completely inhibiting the earth fault current is achieved. Because the fault residual current cannot be directly measured and the zero sequence active current component of the line is difficult to accurately measure, the grounding residual current is taken as a control target, the intermittent arc grounding fault cannot be inhibited, the cost is high, the selling price of one set of device reaches 400 ten thousand yuan, and the method is difficult to be practically applied.
The invention discloses a power distribution network ground fault arc extinction and protection method (patent application number 201110006701.2). The method can realize 100 percent arc extinction of instantaneous faults and quick isolation of permanent faults by injecting a certain current into a power distribution network and forcing the fault phase voltage to be zero and the ground fault current to be zero, thereby solving the defect that the traditional neutral point grounding technology inhibits the fault current. However, this method requires injecting current into the distribution network by means of power electronics, which is costly, and it is difficult to precisely control the amplitude and phase of the injected current, and its suppression effect is difficult to ensure.
In summary, in the prior art, the reliability, safety and economy of power supply of the power distribution system cannot be considered.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for eliminating the residual current of the grounding fault of a system with a neutral point grounded through an arc suppression coil, which can effectively solve the problems provided by the background technology.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for eliminating residual current of ground fault of a system with a neutral point grounded through an arc suppression coil is characterized by comprising the following steps:
step 100, measuring three-phase voltage and zero-sequence voltage of a power distribution system, and detecting a ground fault and a fault phase;
step 200, when a ground fault occurs, putting a passive element into a lagging phase of a fault phase to suppress fault residual current to zero;
step 300, delaying a set time, changing the value of the input passive element, if the zero sequence voltage changes according to a corresponding rule, indicating that the ground fault is eliminated, quitting the input passive element, and recovering the normal operation of the system; otherwise, it is determined as a permanent ground fault, and the procedure returns to step 200.
In a preferred embodiment of the present invention, in step 200, the passive element is formed by connecting a resistor and a capacitor in parallel.
In a preferred embodiment of the present invention, the resistor R in the passive elementmAnd a capacitor CmThe specific expression of (A) is as follows:
Figure BDA0002045684340000031
wherein r iso、C0Respectively representing the resistance and the capacitance of the system to the ground, L is the inductance of the arc suppression coil, and w is the angular frequency of the system.
As a preferred technical solution of the present invention, in step 300, the relationship between the zero sequence voltage and the passive element is:
Figure BDA0002045684340000032
wherein, Csm、RsmAre respectively the set values of the passive components,
Figure BDA0002045684340000033
for the zero sequence voltage of the system after the passive elements are put into use,
Figure BDA0002045684340000034
j is the system angular velocity for the system supply voltage after the passive component is switched on.
In a preferred embodiment of the present invention, the set time is 0.2 seconds to 15 seconds.
Compared with the prior art, the invention has the beneficial effects that:
(1) when an earth fault occurs, the fault residual current can be suppressed to zero by throwing a passive element into a lagging phase of a fault phase, the defect that the active current cannot be compensated by a traditional arc suppression coil is overcome, the safety level of personal equipment at a fault point is obviously improved, and the reliability of power supply is improved.
(2) The value of the passive element which is put into phase after the failure phase lag is irrelevant to the grounding resistance and only relevant to the parameters of the system, so the suppression effect is not influenced by the failure resistance and is good.
(3) Compared with the method for inhibiting the fault current by injecting the current into the system, the method can inhibit the fault residual current to zero only by throwing a passive element into the lagging phase of the fault phase, and has the advantages of simple and reliable operation, small volume of the passive element, convenient adjustment, low cost and better economy.
(4) The invention simultaneously considers the reliability, safety and economy of power supply, and has the advantages of high real-time performance and simple and convenient realization.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a diagram of the current phasor flowing through the passive element of the present invention;
FIG. 3 is a schematic diagram of the elimination of residual current from ground fault of the neutral point through arc suppression coil grounding system according to the present invention;
FIG. 4 is a dynamic waveform diagram of ground fault residual current suppression under 100 ohm ground fault resistance conditions in accordance with the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for eliminating ground fault residual current of a system with a neutral point grounded through an arc suppression coil, which comprises the following steps:
step 100, measuring three-phase voltage and zero-sequence voltage of a power distribution system, and detecting a ground fault and a fault phase;
step 200, when a ground fault occurs, putting a passive element into a lagging phase of a fault phase to suppress fault residual current to zero;
step 300, delaying a set time, wherein the set time is 0.2-15 seconds, changing the value of the input passive element, if the zero sequence voltage changes according to a corresponding rule, indicating that the ground fault is eliminated, quitting the input passive element, and recovering the normal operation of the system; otherwise, it is determined as a permanent ground fault, and the procedure returns to step 200.
In step 200, the passive component is formed by a resistor and a capacitor connected in parallel. The value of the passive element, in which the resistance is independent of the ground resistance and only of the parameters of the system itselfRmAnd a capacitor CmThe specific expression of (A) is as follows:
Figure BDA0002045684340000051
wherein r iso、C0Respectively representing the resistance and the capacitance of the system to the ground, L is the inductance of the arc suppression coil, and w is the angular frequency of the system.
In step 300, the relationship between the zero sequence voltage and the passive element is:
Figure BDA0002045684340000052
wherein, Csm、RsmAre respectively the set values of the passive components,
Figure BDA0002045684340000053
for the zero sequence voltage of the system after the passive elements are put into use,
Figure BDA0002045684340000054
j is the system angular velocity for the system supply voltage after the passive component is switched on.
As shown in fig. 1, which is a schematic diagram for eliminating residual current of ground fault of a system with a neutral point grounded through an arc suppression coil,
Figure BDA0002045684340000055
Figure BDA0002045684340000056
is system power supply voltage, wherein the three-phase voltages are equal in magnitude and sequentially differ by 120 degrees in direction, and r is0、C0Respectively representing the resistance and the capacitance of the system to the ground, wherein the neutral point N is grounded through the arc suppression coil, the inductance of the arc suppression coil is L, Rm，CmResistance and capacitance in passive components.
Let A phase generate single-phase earth fault and its fault resistance be RfZero sequence voltage of
Figure BDA0002045684340000057
Before the passive elements are put into use, a writing node voltage equation of a system neutral point N column is as follows:
Figure BDA0002045684340000058
wherein the content of the first and second substances,
Figure BDA0002045684340000061
simplifying the above formula yields:
Figure BDA0002045684340000062
the fault phase voltage at this time is:
Figure BDA0002045684340000063
the fault current can be solved by combining the two formulas as follows:
Figure BDA0002045684340000064
after the ground fault occurs, a passive element (composed of a resistor and a capacitor which are connected in parallel) is additionally arranged between the hysteresis phase of the fault phase and the ground, and the suppression of the residual current of the ground fault is realized by regulating and controlling zero-sequence voltage. The zero sequence voltage after the compensation element is put into use is set as
Figure BDA0002045684340000065
Then there are:
Figure BDA0002045684340000066
the method is simplified to obtain:
Figure BDA0002045684340000067
let in the above formula
Figure BDA0002045684340000068
I.e. the fault phase voltage can be made zero, so that the fault current is zero.
In addition will be
Figure BDA0002045684340000069
And order
Figure BDA0002045684340000071
At this time Rm，CmIt should satisfy:
Figure BDA0002045684340000072
when the parameters of the passive element satisfy the above formula, the fault phase voltage
Figure BDA0002045684340000073
The voltage of the system phase B at this time is:
Figure BDA0002045684340000074
the current flowing through the passive element is through the resistor RmCurrent flowing through the capacitor CmSuperposition of currents of (c):
Figure BDA0002045684340000075
Figure BDA0002045684340000076
the combined upper formula shows that:
Figure BDA0002045684340000077
the phase voltage can be drawn according to the above formula
Figure BDA0002045684340000078
The current phasor diagram generated on the passive element, as shown in fig. 2, in which
Figure BDA0002045684340000079
Is a capacitor CmThe current generated by the branch-circuit,
Figure BDA00020456843400000710
is a resistance RmThe current generated by the branch-circuit,
Figure BDA00020456843400000711
is that
Figure BDA00020456843400000712
And
Figure BDA00020456843400000713
the vector sum of (1).
According to the formula, the current generated by the passive element in the phase B is equal to the fault current generated by the phase A when the single-phase earth fault occurs, namely, the residual current of the earth fault is just eliminated.
According to the formula, zero sequence voltage and passive element R are obtained when the system is not in faultmAnd CmCorrespondingly, the relationship is shown as the following formula:
Figure BDA0002045684340000081
in the formula Csm，RsmIs a setting value of the passive element.
Therefore, it is possible to judge whether or not the ground fault has been eliminated by changing the passive element value after the passive element is thrown: if the value of the passive element is changed, the change rule of the zero sequence voltage is as the formula, the earth fault is judged to be eliminated, otherwise, the permanent earth fault can be judged.
Fig. 3 is a flow chart of the present invention. Firstly, measuring three-phase voltage and zero-sequence voltage of a system, and detecting a ground fault and a fault phase; when the earth fault occurs, a passive element is put into a lagging phase of the fault phase to suppress the fault residual current to zero; delaying a period of time, changing the value of the passive element, if the zero sequence voltage of the system changes according to a corresponding rule, indicating that the ground fault is eliminated, quitting the passive element and recovering the normal operation of the system; otherwise, judging the fault is a permanent ground fault, readjusting the value of the passive element to suppress the fault residual current to zero until the fault line is isolated, and recovering the normal operation of the system.
The simulation model for eliminating the residual current of the ground fault of the arc suppression coil grounding system shown in the figure 1 is built by utilizing PSCAD, the inductance value of the arc suppression coil is L-0.25H, and the capacitance to the ground of the system is C 010 muF, system resistance to ground r010k Ω. If the phase A of the system has single-phase earth fault and the fault resistance is 100 omega, a passive element is put into the phase B of the lagging phase of the fault phase, and the value of the passive element is set according to the formula, then the following steps are carried out: cm＝5.56μF、RmWhen the ground fault occurs, 0.02s is set at 1239.16 Ω, the passive element is thrown in at 0.04s, and fig. 4 is a fault residual current waveform diagram corresponding to a ground fault resistance of 100 Ω. As can be seen from fig. 4, when the passive element is applied (0.04s), the residual current of the fault is quickly suppressed to zero, and the residual current of the ground fault of the system in which the neutral point is grounded through the arc suppression coil is eliminated.
Figure BDA0002045684340000091
As shown in the above table, in order to verify the effectiveness of the present disclosure for low resistance faults and high resistance faults, when the simulated fault resistance values are respectively 8 Ω, 25 Ω, 100 Ω, and 1000 Ω (a phase is in ground fault), the fault occurrence time is 0.02s, and the passive element is put in at 0.04s, the simulation results of the corresponding fault currents before and after the passive element is put in are summarized as shown in the above table.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (2)

1. A method for eliminating residual current of ground fault of a system with a neutral point grounded through an arc suppression coil is characterized by comprising the following steps:
step 100, measuring three-phase voltage and zero-sequence voltage of a power distribution system, and detecting a ground fault and a fault phase;
step 200, when a ground fault occurs, putting a passive element into a lagging phase of a fault phase to suppress fault residual current to zero;
step 300, delaying a set time, changing the value of the input passive element, if the zero sequence voltage changes according to a corresponding rule, indicating that the ground fault is eliminated, quitting the input passive element, and recovering the normal operation of the system; otherwise, judging as a permanent earth fault, and returning to the step 200;
in step 200, the passive element is composed of a resistor and a capacitor connected in parallel;
resistance R in the passive elementmAnd a capacitor CmThe specific expression of (A) is as follows:
Figure FDA0002958239410000011
wherein r is0、C0Respectively representing the resistance and the capacitance of the system to the ground, wherein L is the inductance of an arc suppression coil, and omega is the angular frequency of the system;
in step 300, the relationship between the zero sequence voltage and the passive element is:
Figure FDA0002958239410000012
wherein, Csm、RsmAre respectively the set values of the passive components,
Figure FDA0002958239410000013
for the zero sequence voltage of the system after the passive elements are put into use,
Figure FDA0002958239410000014
j is the system angular velocity for the system supply voltage after the passive component is switched on.
2. The method of claim 1, wherein the set time is 0.2 seconds to 15 seconds.
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CN206533136U (en) * 2016-12-20 2017-09-29 大连电力勘察设计院有限公司 220kV transformer stations arc suppression coil parallel low resistance earthed system

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