CN117148214A - Online monitoring method for turn-to-turn short circuit fault of dry hollow parallel reactor group of neutral point ungrounded system - Google Patents

Online monitoring method for turn-to-turn short circuit fault of dry hollow parallel reactor group of neutral point ungrounded system Download PDF

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CN117148214A
CN117148214A CN202311150212.3A CN202311150212A CN117148214A CN 117148214 A CN117148214 A CN 117148214A CN 202311150212 A CN202311150212 A CN 202311150212A CN 117148214 A CN117148214 A CN 117148214A
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庄羽
王永红
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Harbin University of Science and Technology
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Abstract

The invention discloses an online monitoring method for turn-to-turn short circuit faults of a dry type hollow parallel reactor group of a neutral point ungrounded system, and belongs to the technical field of online monitoring of dry type hollow reactors. The problem of large error of a monitoring result of the on-line monitoring method of the turn-to-turn short circuit fault of the dry air reactor in the prior art is solved; the invention comprises the following steps: s1, calculating electrical parameters of a dry hollow parallel reactor group of a normal operation neutral point ungrounded system; s2, calculating electrical parameters of the dry type hollow parallel reactor group of the inter-turn short circuit fault neutral point ungrounded system; s3, adopting a normal operation reactor set basic equation as a monitoring algorithm to perform on-line monitoring of the reactor set, and performing inter-turn short circuit fault judgment according to inter-turn short circuit fault judgment conditions; s4, calculating the minimum absolute change quantity of the loss percentage of the dry air reactor as a threshold value for judging the turn-to-turn short circuit; the invention effectively reduces the measurement error and can be applied to the online monitoring of the dry type air-core reactor.

Description

Online monitoring method for turn-to-turn short circuit fault of dry hollow parallel reactor group of neutral point ungrounded system
Technical Field
The invention relates to an online monitoring method for turn-to-turn short circuit faults of a dry type hollow parallel reactor, in particular to an online monitoring method for turn-to-turn short circuit faults of a dry type hollow parallel reactor of a neutral point ungrounded system, and belongs to the technical field of online monitoring of dry type hollow reactors.
Background
The dry hollow shunt reactor has the technical advantages of simple structure, light weight, good linearity, convenient maintenance and the like, is widely applied to power systems, but in recent years, the dry hollow shunt reactor has a plurality of firing accidents, and seriously threatens the safe operation of a power grid. A large number of research results show that most of dry-type hollow parallel reactor group faults are inter-turn short circuit faults caused by inter-turn insulation breakdown, the current flowing through the dry-type hollow parallel reactor is very small in the initial period of the inter-turn short circuit faults, overcurrent protection cannot act in time, and the current cannot be protected after the current gradually develops into single-phase short circuit or phase-to-ground short circuit faults, so that fire accidents occur.
Research on new technology of on-line monitoring of dry air-core reactors has been gradually carried out, and monitoring projects mainly comprise electrical parameter monitoring, magnetic field monitoring, temperature field monitoring and the like. The electrical parameter monitoring increases the operating voltage and the angle formed by the operating voltage and the current, or the equivalent impedance calculated by the operating voltage and the angle; the magnetic field monitoring adopts a detection coil to detect the change of the magnetic field around the reactor caused by turn-to-turn short circuit; the temperature field monitors the reactor external temperature variation. Temperature field monitoring has a slower response speed due to the heat transfer process of temperature. In comparison, electrical parameter and magnetic field monitoring have faster response speeds, which react to turn-to-turn short circuit faults from different angles of electricity and magnetism, respectively.
The dry hollow shunt reactor is manufactured by adopting a single phase, three phases are connected in a Y-type way to form a reactor group, a neutral point is not grounded, and referring to fig. 2, in a power system, the reactor group is provided with a circuit breaker and a current transformer, and a bus is provided with a voltage transformer.
When electric parameter monitoring is carried out, three-phase bus phase voltage signals can be obtained through a voltage transformer, phase current signals flowing through the reactors of all phases can be obtained through a current transformer, and as the three-phase voltage and the impedance of the three-phase reactors are not completely balanced, the neutral point voltage is not zero and can be changed along with the unbalance degree. If the neutral point voltage drop is ignored, the direct calculation of the electrical parameters using the signals obtained by the voltage transformer and the current transformer brings about a large measurement error.
In neutral ungrounded systems, a high level of insulation is required for the neutral to ground. The voltage signal of the neutral point can be obtained by adding the voltage level or the voltage divider which is the same as the phase voltage to the neutral point, the voltage signal of the neutral point is very low in normal operation, the voltage signal obtained by voltage reduction through the voltage divider is very weak, new challenges are brought to online monitoring, additional economic investment is brought to a system by adding a high-voltage component, the problem that the neutral point is not grounded is usually ignored in the actual monitoring research of the turn-to-turn short circuit fault of the dry air-core reactor, and the actually obtained monitoring result has larger error and cannot accurately judge the turn-to-turn short circuit fault of the dry air-core reactor.
Therefore, a method for monitoring the dry type hollow parallel reactor group of the neutral point ungrounded system is needed to solve the problem that the online monitoring result error of the dry type hollow parallel reactor group of the neutral point ungrounded system is larger.
Disclosure of Invention
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
In view of the above, the invention provides an on-line monitoring method for the inter-turn short circuit fault of a dry type hollow parallel reactor group, which aims to solve the problem of larger error of the monitoring result in the on-line monitoring method for the inter-turn short circuit fault of the dry type hollow reactor in the prior art.
The technical proposal is as follows: an online monitoring method for turn-to-turn short circuit faults of a dry hollow parallel reactor group of a neutral point ungrounded system comprises the following steps:
s1, calculating electrical parameters of a dry hollow parallel reactor group of a normal operation neutral point ungrounded system;
Specific:
s11, calculating to obtain the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s12, calculating neutral point voltage according to the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s13, obtaining an impedance basic equation of the normal operation reactor group according to the phase sequence relation of the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s2, calculating electrical parameters of the dry type hollow parallel reactor group of the inter-turn short circuit fault neutral point ungrounded system;
specific:
s21, calculating to obtain the reactance of the three-phase reactor after the fault and the loss percentage of the three-phase reactor after the fault;
s22, obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s3, adopting a normal operation reactor set basic equation as a monitoring algorithm to perform on-line monitoring of the reactor set, and performing inter-turn short circuit fault judgment according to inter-turn short circuit fault judgment conditions;
s4, calculating the absolute change quantity of the loss percentage of the turn-to-turn short circuit fault at the innermost end of the dry hollow shunt reactor, and taking the absolute change quantity as a threshold value for judging the turn-to-turn short circuit.
Further, in the step S11, for the Y-type connected reactor group, the neutral point to ground voltage isThe three-phase voltage is represented by A-phase voltage +.>B-phase voltage->And C phase voltage->The three-phase current is composed of A-phase current/>Phase B current->And C phase current->The three-phase reactor impedance is composed of A-phase reactor impedance Z A Impedance Z of B-phase reactor B And C-phase reactor impedance Z C Composition;
the three phase voltages are expressed as:
the three-phase current satisfaction condition is expressed as:
combining the formula (1) and the formula (2) to obtain neutral point voltage
Neutral point voltageExpressed as:
in the formula (3), the three-phase reactor impedance is expressed as:
wherein j is an imaginary unit, and the three-phase reactorReactance is obtained by A-phase reactor reactance X A Reactance X of B-phase reactor B And C-phase reactor reactance X C The three-phase reactor loss percentage is composed of an A-phase reactor loss percentage K A Loss percentage K of B-phase reactor B Loss percentage K of C-phase reactor C Composition;
let the average value of the reactance of the three-phase reactor be X AVG The relative deviation of the three-phase reactor reactance from the average value thereof is represented by the relative deviation gamma of the A-phase reactor reactance from the average value thereof XA Relative deviation gamma of reactance of B-phase reactor and average value thereof XB And the relative deviation gamma of the C-phase reactor reactance from its average value XC Composition; let the average value of the loss percentages of the three-phase reactor be K AVG The absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is represented by the absolute deviation delta K of the loss percentage of the A-phase reactor from the average value thereof A Absolute deviation delta K of loss percentage of B-phase reactor from average value B And absolute deviation ΔK of C-phase reactor loss percentage from its average C Composition;
the relative deviation of the three-phase reactor reactance from its average value is expressed as:
the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is expressed as:
in the formula (5), the relative deviation between the three-phase reactance value and the average value thereof satisfies the condition expressed as:
γ XA +γ XB +γ XC ＝0 (7)
in the formula (6), the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof satisfies the condition expressed as:
ΔK A +ΔK B +ΔK C ＝0 (8)。
further, in the step S12, the three-phase reactor impedance is obtained according to the relative deviation between the three-phase reactor reactance and the average value thereof and the absolute deviation between the three-phase reactor loss percentage and the average value thereof;
the three-phase reactor impedance is expressed as:
substituting the formula (9) into the formula (3), and neglecting the relative deviation of the three-phase reactor reactance and the average value thereof, the three-phase reactor loss percentage and the higher order term and the product term of the absolute deviation of the three-phase reactor loss percentage and the average value thereof to obtain the neutral point voltage
Neutral point voltageExpressed as:
wherein,for zero sequence voltage>For voltage drop caused by unbalance of reactance of three-phase reactor, < >>Voltage drop caused by unbalanced loss percentage of the three-phase reactor.
Further, in S13, a voltage drop due to unbalance of reactance of the three-phase reactorAnd voltage drop caused by unbalance of loss percentages of three-phase reactor +.>Wherein, the relative deviation of the three-phase reactor reactance and the average value thereof and the absolute deviation of the three-phase reactor loss percentage and the average value thereof are respectively the real part coefficient and the imaginary part coefficient of the three-phase voltage, and the three-phase reactor impedance is obtained by combining the formula (1) and the formula (10):
the three-phase reactor impedance is expressed as:
obtaining an impedance basic equation of the normal operation reactor group according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
the basic equation for the impedance of a normal operation reactor set is expressed as:
wherein the three-phase positive sequence voltage is composed of A-phase positive sequence voltageB-phase positive sequence voltage->And C-phase positive sequence voltage->The three-phase negative sequence voltage is composed of A-phase negative sequence voltage +.>B phase negative sequence voltage->And C-phase negative sequence voltage->
The relative deviation of the reactance of each reactor and the absolute deviation of the loss percentage in the normal operation dry type hollow parallel reactor group can be obtained through calculation through offline measurement values of the reactance of each reactor and the loss percentage, and after the three-phase voltage and the three-phase current are monitored, the loss percentage monitoring value of each reactor under the normal operation condition can be obtained through analysis type (12).
Further, in S21, it is assumed that an inter-turn short circuit fault occurs in the a-phase reactor, and the reactance of the a-phase reactor after the inter-turn short circuit fault is X' A The relative change value of the reactance of the phase A reactor after turn-to-turn short circuit fault is gamma' XA Loss percentage of the phase A reactor after turn-to-turn short circuit fault is K' A The absolute change value of the loss percentage of the phase A reactor after turn-to-turn short circuit fault is delta K' A Obtaining the average value X 'of the reactance of the three-phase reactor after turn-to-turn short circuit fault' AVG Average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG ；
Average value X 'of three-phase reactor reactance after turn-to-turn short circuit fault' AVG Expressed as:
average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG Expressed as:
according to equation (13), the three-phase reactor reactance after the turn-to-turn short circuit fault is expressed as:
wherein the relative deviation of the three-phase resistor reactance after the inter-turn short circuit fault and the average value thereof is determined by the relative deviation of the A-phase resistor reactance after the inter-turn short circuit fault and the average value thereofRelative deviation of the reactance of the B-phase resistor from its average value after a turn-to-turn short-circuit fault +.>And the relative deviation of the C-phase resistor reactance from its average value after turn-to-turn short circuit failure Composition;
according to equation (14), the three-phase reactor loss percentage after the turn-to-turn short circuit fault is expressed as:
wherein, the absolute deviation of the loss percentage of the three-phase reactor after the turn-to-turn short circuit fault and the average value thereof is determined by the absolute deviation of the loss percentage of the A-phase reactor after the fault and the average value thereofAbsolute deviation of B-phase reactor loss percentage after turn-to-turn short circuit fault and average value thereof +.>And absolute deviation of C-phase reactor loss percentage from average value after turn-to-turn short circuit fault +.>Composition is prepared.
Further, in S22, the formulas (15) and (16) are substituted into the formula (3), and the relative deviation of the three-phase reactor reactance from the average value thereof, the three-phase reactor loss percentage, and the three-phase reactor loss percentage are ignoredThe higher order term of the absolute deviation of the average value thereof, obtains the neutral point voltage
Neutral point voltageExpressed as:
wherein,the voltage change value of the neutral point caused by turn-to-turn short circuit fault of the phase A reactor is obtained;
substituting the formula (17) into the formula (1), and obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the phase sequence relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
the fundamental equation for the impedance of the reactor set after the turn-to-turn short circuit fault is expressed as:
wherein,
further, in the step S3, the reactance relative change amount of the three-phase reactor after the turn-to-turn short circuit fault is increased by a value gamma' XA And delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A For unknown quantity, neglecting neutral point voltage change caused by inter-turn short circuit fault, wherein the impedance basic equation of the inter-turn short circuit fault reactor group is consistent with the basic equation of the group of normal operation reactors, under the condition, the loss percentage of the three-phase reactor after the inter-turn short circuit fault is calculated by neglecting turns when the neutral point voltage change caused by the inter-turn short circuit fault is ignoredPercentage K' of loss of A-phase reactor after turn-to-turn short circuit fault when neutral point voltage is changed caused by short circuit fault A Loss percentage K' of B-phase reactor after inter-turn short circuit fault when neutral point voltage change caused by inter-turn short circuit fault is ignored B "and C-phase reactor loss percentage K 'after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored' C ' composition, calculating to obtain the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored, and the reactance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored, wherein the reactance of the three-phase reactor X ' after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored ' A ' B-phase reactor reactance X ' after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored ' B ' and C-phase reactor reactance X ' after the turn-to-turn short circuit fault when neutral point voltage change caused by the turn-to-turn short circuit fault is ignored ' C ' composition;
the impedance of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
the three-phase positive sequence voltage is far greater than the three-phase negative sequence voltage, and the three-phase reactor impedance difference calculated by the formula (19) and the formula (18) is mainly positive sequence impedance difference;
multiplying the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored in the formula (19) by coefficients a, b and c in the formula (18) respectively to obtain the loss percentage relation of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored;
the relationship of the loss percentage of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage changes caused by the inter-turn short circuit fault is ignored is expressed as follows:
will K' A ＝K A +ΔK′ A Substituting the three-phase reactor loss percentage variation after the inter-turn short circuit fault when the neutral point voltage variation caused by the inter-turn short circuit fault is ignored into the formula (20);
The loss percentage change quantity of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
wherein, the percentage change of the loss of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is the percentage change of the loss of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored A Percentage change delta K' of loss of B-phase reactor after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored B And neglecting the loss percentage change delta K' of the C-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage is changed due to the turn-to-turn short circuit fault C Composition;
adding the loss percentage change quantity of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored to obtain the loss percentage absolute change quantity increase value delta K 'of the three-phase reactor after the inter-turn short circuit fault' A ；
Delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A Expressed as:
ΔK′ A ＝ΔK″ A +ΔK″ B +ΔK″ C (22)
in summary, the calculated increase value of the loss percentage change of the three-phase reactor after the inter-turn short circuit fault is distributed to the three-phase reactors according to different proportions, the absolute change value of the loss percentage of the three-phase reactor after the inter-turn short circuit fault is far greater than the relative change value of the reactance of the three-phase reactor, the calculated loss percentage change of the three-phase reactor after the inter-turn short circuit fault is increased, the loss percentage change value of the A-phase reactor containing the inter-turn short circuit fault is far greater than the loss percentage change value of the other two-phase reactors, and the loss percentage change value of the A-phase reactor is 2/3 of the actual change value;
Adopting a formula (12) or a formula (19) with the same calculation method as a monitoring algorithm, continuously monitoring three-phase voltage to ground and three-phase current, calculating a three-phase reactor loss percentage monitoring value by combining known normal operation reactor impedance, and performing difference value operation on each reactor reactance and loss percentage monitoring value and historical data to obtain absolute variation of loss percentage of each phase reactor;
when an inter-turn short circuit fault occurs at a certain moment, the absolute variation is suddenly changed, and according to the formula (21), the inter-turn short circuit fault judgment condition is deduced to judge the inter-turn short circuit fault;
the inter-turn short circuit fault judgment condition is expressed as: and when the minimum absolute change quantity of the loss percentage of a certain coherent air-core reactor exceeds 2/3 times of the actual change quantity, judging that the phase reactor has turn-to-turn short circuit fault.
Further, in the S4, in the equivalent circuit of the dry type hollow shunt reactor, the dry type hollow shunt reactor is wound in a multi-layer manner, the equivalent circuit of the dry type hollow shunt reactor is built by taking the layer as a unit under the power frequency voltage,for applying voltage>For the current flowing through the reactor, +.>R is the current flowing through each layer of coil 1 ～R n For the resistance of each layer of coil, L 1 ～L n For the self-inductance of each layer of coil, +.>For the induced potential formed by mutual inductance between each coil and other coils, i (i=1) the induction potential of the n) layer coil is +.>
Induced potential of the ith layer coilExpressed as:
wherein j is an imaginary symbol, ω is an angular frequency, M i,k Is the mutual inductance of the ith layer coil and the kth layer coil;
establishing a voltage equation set of an equivalent circuit of the dry-type hollow shunt reactor;
the voltage equation set of the equivalent circuit of the dry type hollow shunt reactor is expressed as follows:
wherein,for the equivalent resistance of each layer of coils of the equivalent circuit of the dry-type air-core shunt reactor, the resistance, self inductance and mutual inductance among the coils of each layer are determined by the structure of the reactor group and the characteristics of metal materials, n equations and current variables are arranged in the formula (24), and the current of each layer of coils can be analyzed;
total current flowing through the reactorExpressed as:
the impedance value Z of the dry hollow shunt reactor is expressed as:
wherein X is a reactance value, and K is a loss percentage;
in the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor, the fault layer coil can be divided into two parts under the assumption that the ith layer coil has 1 turn of short circuit fault, the short circuit turns form an n+1th branch, and the rest turns form an ith branch;
establishing a voltage equation set of an equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor;
The voltage equation set of the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor is expressed as:
wherein,for the equivalent resistance of each layer of coil of the equivalent circuit of the turn-to-turn short circuit fault dry-type hollow shunt reactor, the equation (27) forms n+1 equations, n+1 current variables exist, each current value is obtained by solving the equation set, the current flowing through the reactor does not contain short circuit turn current, and the reactance and loss percentage of the turn-to-turn short circuit fault reactor are analyzed by utilizing the equation (25) and the equation (26); the method is characterized in that the loss percentage variation is minimum after the inter-turn short circuit fault occurs at the innermost end of the dry type hollow parallel reactor is deduced, the absolute variation of the inter-turn short circuit fault loss percentage at the innermost end of the dry type hollow parallel reactor is calculated through theory, 2/3 times of the absolute variation is taken as a threshold for judging the inter-turn short circuit, and the inter-turn short circuit fault occurring at any position of the threshold can be effectively judged.
The beneficial effects of the invention are as follows: according to the invention, the neutral point voltage of the reactor group can be accurately calculated by calculating the electrical parameters of the dry hollow parallel reactor group of the neutral point ungrounded system; the loss percentage before and after the turn-to-turn short circuit fault of the dry hollow parallel reactor group can be accurately calculated through summarizing the deduced on-line monitoring method of the turn-to-turn short circuit fault of the dry hollow parallel reactor group of the neutral point ungrounded system; the influence of the unbalance of the neutral point unconnected system voltage and impedance on the loss percentage monitoring result is solved, the measurement error is effectively reduced, and the measurement accuracy is improved; and accurately judging the turn-to-turn short circuit faults of the dry type hollow paralleling reactor and the fault phase sequence of the reactor group according to the minimum absolute change quantity of the turn-to-turn short circuit fault loss percentage of the innermost layer end part of the dry type hollow paralleling reactor.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic flow chart of an online monitoring method for turn-to-turn short circuit faults of a dry hollow parallel reactor set for a neutral point ungrounded system;
FIG. 2 is a schematic diagram of the wiring of a dry hollow parallel reactor assembly in a power system;
FIG. 3 is a schematic diagram of equivalent circuit of a dry hollow shunt reactor;
fig. 4 is a schematic diagram of an equivalent circuit of the turn-to-turn short circuit fault dry-type air-core shunt reactor.
Reference numerals: 1. a voltage transformer; 2. a circuit breaker; 3. a current transformer; 4. a reactor group; 5. a neutral point.
Detailed Description
In order to make the technical solutions and advantages of the embodiments of the present invention more apparent, the following detailed description of exemplary embodiments of the present invention is provided in conjunction with the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention and not exhaustive of all embodiments. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
Referring to fig. 1-4, the embodiment of the method for on-line monitoring the turn-to-turn short circuit fault of the dry type hollow parallel reactor for the neutral point ungrounded system specifically comprises the following steps:
s1, calculating electrical parameters of a dry hollow parallel reactor group of a normal operation neutral point ungrounded system;
specific:
s11, calculating to obtain the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s12, calculating neutral point voltage according to the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s13, obtaining an impedance basic equation of the normal operation reactor group according to the phase sequence relation of the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s2, calculating electrical parameters of the dry type hollow parallel reactor group of the inter-turn short circuit fault neutral point ungrounded system;
specific:
s21, calculating to obtain the reactance of the three-phase reactor after the fault and the loss percentage of the three-phase reactor after the fault;
s22, obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s3, adopting a normal operation reactor set basic equation as a monitoring algorithm to perform on-line monitoring of the reactor set, and performing inter-turn short circuit fault judgment according to inter-turn short circuit fault judgment conditions;
S4, calculating the absolute change quantity of the loss percentage of the turn-to-turn short circuit fault at the innermost end of the dry hollow shunt reactor, and taking the absolute change quantity as a threshold value for judging the turn-to-turn short circuit.
Further, in the step S11, for the Y-type connected reactor group, the neutral point to ground voltage isThe three-phase voltage is represented by A-phase voltage +.>B-phase voltage->And C phase voltage->The three-phase current is composed of A-phase current +.>Phase B current->And C phase current->The three-phase reactor impedance is composed of A-phase reactor impedance Z A Impedance Z of B-phase reactor B And C-phase reactor impedance Z C Composition;
the three phase voltages are expressed as:
the three-phase current satisfaction condition is expressed as:
combining the formula (1) and the formula (2) to obtain neutral point voltage
Neutral point voltageExpressed as:
in the formula (3), the three-phase reactor impedance is expressed as:
wherein j is an imaginary unit, and the three-phase reactor reactance is represented by an A-phase reactor reactance X A Reactance X of B-phase reactor B And C-phase reactor reactance X C The three-phase reactor loss percentage is composed of an A-phase reactor loss percentage K A Loss percentage K of B-phase reactor B Loss percentage K of C-phase reactor C Composition;
let the average value of the reactance of the three-phase reactor be X AVG The relative deviation of the three-phase reactor reactance from the average value thereof is represented by the relative deviation gamma of the A-phase reactor reactance from the average value thereof XA Relative deviation gamma of reactance of B-phase reactor and average value thereof XB And the relative deviation gamma of the C-phase reactor reactance from its average value XC Composition; let the average value of the loss percentages of the three-phase reactor be K AVG The absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is represented by the absolute deviation delta K of the loss percentage of the A-phase reactor from the average value thereof A Absolute deviation delta K of loss percentage of B-phase reactor from average value B And absolute deviation ΔK of C-phase reactor loss percentage from its average C Composition;
the relative deviation of the three-phase reactor reactance from its average value is expressed as:
the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is expressed as:
/>
in the formula (5), the relative deviation between the three-phase reactance value and the average value thereof satisfies the condition expressed as:
γ XA +γ XB +γ XC ＝0 (7)
in the formula (6), the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof satisfies the condition expressed as:
ΔK A +ΔK B +ΔK C ＝0 (8)。
further, in the step S12, the three-phase reactor impedance is obtained according to the relative deviation between the three-phase reactor reactance and the average value thereof and the absolute deviation between the three-phase reactor loss percentage and the average value thereof;
the three-phase reactor impedance is expressed as:
substituting the formula (9) into the formula (3), and neglecting the relative deviation of the three-phase reactor reactance and the average value thereof, the three-phase reactor loss percentage and the higher order term and the product term of the absolute deviation of the three-phase reactor loss percentage and the average value thereof to obtain the approximate neutral point voltage
Neutral point voltageExpressed as:
wherein,for zero sequence voltage>For three-phase reactor reactance imbalanceVoltage drop caused, ">Voltage drop caused by unbalanced loss percentage of the three-phase reactor.
Further, in S13, a voltage drop due to unbalance of reactance of the three-phase reactorAnd voltage drop caused by unbalance of loss percentages of three-phase reactor +.>Wherein, the relative deviation of the three-phase reactor reactance and the average value thereof and the absolute deviation of the three-phase reactor loss percentage and the average value thereof are respectively the real part coefficient and the imaginary part coefficient of the three-phase voltage, and the three-phase reactor impedance is obtained by combining the formula (1) and the formula (10):
the three-phase reactor impedance is expressed as:
obtaining an impedance basic equation of the normal operation reactor group according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
the basic equation for the impedance of a normal operation reactor set is expressed as:
wherein the three-phase positive sequence voltage is composed of A-phase positive sequence voltageB-phase positive sequence voltage->And C-phase positive sequence voltage->The three-phase negative sequence voltage is composed of A-phase negative sequence voltage +.>B phase negative sequence voltage->And C-phase negative sequence voltage->
The relative deviation of the reactance of each reactor and the absolute deviation of the loss percentage in the normal operation dry type hollow parallel reactor group can be obtained through calculation through offline measurement values of the reactance of each reactor and the loss percentage, and after the three-phase voltage and the three-phase current are monitored, the loss percentage monitoring value of each reactor under the normal operation condition can be obtained through analysis type (12).
Further, in S21, it is assumed that an inter-turn short circuit fault occurs in the a-phase reactor, and the reactance of the a-phase reactor after the inter-turn short circuit fault is X' A The relative change value of the reactance of the phase A reactor after turn-to-turn short circuit fault is gamma' XA Loss percentage of the phase A reactor after turn-to-turn short circuit fault is K' A The absolute change value of the loss percentage of the phase A reactor after turn-to-turn short circuit fault is delta K' A Obtaining the average value X 'of the reactance of the three-phase reactor after turn-to-turn short circuit fault' AVG Average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG ；
Average value X 'of three-phase reactor reactance after turn-to-turn short circuit fault' AVG Expressed as:
average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG Expressed as:
according to equation (13), the three-phase reactor reactance after the turn-to-turn short circuit fault is expressed as:
wherein the relative deviation of the three-phase resistor reactance after the inter-turn short circuit fault and the average value thereof is determined by the relative deviation of the A-phase resistor reactance after the inter-turn short circuit fault and the average value thereofRelative deviation of the reactance of the B-phase resistor from its average value after a turn-to-turn short-circuit fault +.>And the relative deviation of the C-phase resistor reactance from its average value after turn-to-turn short circuit failureComposition;
according to equation (14), the three-phase reactor loss percentage after the turn-to-turn short circuit fault is expressed as:
Wherein, the absolute deviation of the loss percentage of the three-phase reactor after the turn-to-turn short circuit fault and the average value thereof is determined by the absolute deviation of the loss percentage of the A-phase reactor after the fault and the average value thereofAbsolute deviation of B-phase reactor loss percentage after turn-to-turn short circuit fault and average value thereof +.>C-phase electricity after turn-to-turn short circuit faultAbsolute deviation of the percent reactor loss from its mean value +.>Composition;
specifically, according to field operation experience, only one reactor in the accident reactor group fails, so that only the phase A reactor is assumed to have turn-to-turn short circuit fault.
Further, in S22, the formula (15) and the formula (16) are substituted into the formula (3), and the higher order terms of the relative deviation of the three-phase reactor reactance from the average value thereof, the three-phase reactor loss percentage, and the absolute deviation of the three-phase reactor loss percentage from the average value thereof are ignored, thereby obtaining the neutral point voltage
Neutral point voltageExpressed as:
wherein,the voltage change value of the neutral point caused by turn-to-turn short circuit fault of the phase A reactor is obtained;
substituting the formula (17) into the formula (1), and obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the phase sequence relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
the fundamental equation for the impedance of the reactor set after the turn-to-turn short circuit fault is expressed as:
/>
Wherein,
further, in the step S3, the reactance relative change amount of the three-phase reactor after the turn-to-turn short circuit fault is increased by a value gamma' XA And delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A For unknown quantity, neglecting the neutral point voltage change caused by the inter-turn short circuit fault, wherein the impedance basic equation of the inter-turn short circuit fault reactor group is consistent with the basic equation of the group of the normal operation reactor, under the condition, the loss percentage of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is the loss percentage K' of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored A Percentage K' of loss of B-phase reactor after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored B And neglecting loss percentage K 'of C-phase reactor after turn-to-turn short circuit fault when neutral point voltage changes caused by the turn-to-turn short circuit fault' C ' composition, calculating to obtain the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored, and the reactance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored, wherein the reactance of the three-phase reactor X ' after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored ' A ' B-phase reactor reactance X ' after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored ' B ' and C-phase reactor reactance X ' after the turn-to-turn short circuit fault when neutral point voltage change caused by the turn-to-turn short circuit fault is ignored ' C ' composition;
the impedance of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
the three-phase positive sequence voltage is far greater than the three-phase negative sequence voltage, and the three-phase reactor impedance difference calculated by the formula (19) and the formula (18) is mainly positive sequence impedance difference;
multiplying the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored in the formula (19) by coefficients a, b and c in the formula (18) respectively to obtain the loss percentage relation of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored;
the relationship of the loss percentage of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage changes caused by the inter-turn short circuit fault is ignored is expressed as follows:
/>
will K' A ＝K A +ΔK′ A Substituting the three-phase reactor loss percentage variation after the inter-turn short circuit fault when the neutral point voltage variation caused by the inter-turn short circuit fault is ignored into the formula (20);
The loss percentage change quantity of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
wherein, the percentage change of the loss of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is the percentage change of the loss of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored A Percentage change delta K' of loss of B-phase reactor after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored B And neglecting the loss percentage change delta K' of the C-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage is changed due to the turn-to-turn short circuit fault C Composition;
adding the loss percentage change quantity of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored to obtain turnsDelta K 'for increasing loss percentage absolute change of three-phase reactor after inter-short circuit fault' A ；
Delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A Expressed as:
ΔK′ A ＝ΔK″ A +ΔK″ B +ΔK″ C (22)
in summary, the calculated increase value of the loss percentage change of the three-phase reactor after the inter-turn short circuit fault is distributed to the three-phase reactors according to different proportions, the absolute change value of the loss percentage of the three-phase reactor after the inter-turn short circuit fault is far greater than the relative change value of the reactance of the three-phase reactor, the calculated loss percentage change of the three-phase reactor after the inter-turn short circuit fault is increased, the loss percentage change value of the A-phase reactor containing the inter-turn short circuit fault is far greater than the loss percentage change value of the other two-phase reactors, and the loss percentage change value of the A-phase reactor is 2/3 of the actual change value;
Adopting a formula (12) or a formula (19) with the same calculation method as a monitoring algorithm, continuously monitoring three-phase voltage to ground and three-phase current, calculating a three-phase reactor loss percentage monitoring value by combining known normal operation reactor impedance, and performing difference value operation on each reactor reactance and loss percentage monitoring value and historical data to obtain absolute variation of loss percentage of each phase reactor;
when an inter-turn short circuit fault occurs at a certain moment, the absolute variation is suddenly changed, and according to the formula (21), the inter-turn short circuit fault judgment condition is deduced to judge the inter-turn short circuit fault;
the inter-turn short circuit fault judgment condition is expressed as: when the minimum absolute change quantity of the loss percentage of a certain coherent air-core reactor exceeds 2/3 times of the actual change quantity, judging that the phase reactor has turn-to-turn short circuit fault;
specifically, the reactance relative change amount of the three-phase reactor after turn-to-turn short circuit fault is increased by a value gamma' XA And delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A Is unknown, so that the formula (18) cannot obtain the turn-to-turn short circuitThe loss percentage of each reactor behind the barrier is small, and the neutral point voltage change caused by the inter-turn short circuit fault is ignored because the inter-turn short circuit fault has small neutral point voltage change, and the impedance basic equation of the inter-turn short circuit fault reactor group is consistent with the group basic equation of the normal operation reactor.
Further, in the S4, in the equivalent circuit of the dry type hollow shunt reactor, the dry type hollow shunt reactor is wound in a multi-layer manner, the equivalent circuit of the dry type hollow shunt reactor is built by taking the layer as a unit under the power frequency voltage,for applying voltage>For the current flowing through the reactor, +.>R is the current flowing through each layer of coil 1 ～R n For the resistance of each layer of coil, L 1 ～L n For the self-inductance of each layer of coil, +.>For the induced potential formed by mutual inductance between each coil and other coils, i (i=1) the induction potential of the n) layer coil is +.>
Induced potential of the ith layer coilExpressed as:
wherein j is an imaginary symbol, ω is an angular frequency, M i,k Is the mutual inductance of the ith layer coil and the kth layer coil;
establishing a voltage equation set of an equivalent circuit of the dry-type hollow shunt reactor;
the voltage equation set of the equivalent circuit of the dry type hollow shunt reactor is expressed as follows:
wherein,for the equivalent resistance of each layer of coils of the equivalent circuit of the dry-type air-core shunt reactor, the resistance, self inductance and mutual inductance among the coils of each layer are determined by the structure of the reactor group and the characteristics of metal materials, n equations and current variables are arranged in the formula (24), and the current of each layer of coils can be analyzed;
total current flowing through the reactorExpressed as:
the impedance value Z of the dry hollow shunt reactor is expressed as:
Wherein X is a reactance value, and K is a loss percentage;
in the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor, the fault layer coil can be divided into two parts under the assumption that the ith layer coil has 1 turn of short circuit fault, the short circuit turns form an n+1th branch, and the rest turns form an ith branch;
establishing a voltage equation set of an equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor;
the voltage equation set of the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor is expressed as:
wherein,for the equivalent resistance of each layer of coil of the equivalent circuit of the turn-to-turn short circuit fault dry-type hollow shunt reactor, the equation (27) forms n+1 equations, n+1 current variables exist, each current value is obtained by solving the equation set, the current flowing through the reactor does not contain short circuit turn current, and the reactance and loss percentage of the turn-to-turn short circuit fault reactor are analyzed by utilizing the equation (25) and the equation (26); the method is characterized in that the loss percentage variation is minimum after the inter-turn short circuit fault occurs at the innermost end of the dry type hollow parallel reactor is deduced, the absolute variation of the inter-turn short circuit fault loss percentage at the innermost end of the dry type hollow parallel reactor is calculated through theory, 2/3 times of the absolute variation is taken as a threshold for judging the inter-turn short circuit, and the inter-turn short circuit fault occurring at any position of the threshold can be effectively judged;
Specifically, according to the technical standard of 10-66 kV dry-type reactors, when three reactance deviations are within the allowable range of 5%, the deviation between each phase reactance and the average value of the three phase reactances is not more than 2%, and according to the specification in GB/T15543 three-phase voltage unbalance of electric energy quality, when a power grid normally operates, the negative sequence voltage unbalance is not more than 2%, and the operating voltage amplitude, reactance value, phase and unbalance data of the three-phase dry-type air-core parallel reactor are shown in table 1;
table 1 three-phase dry hollow shunt reactor parameters
According to an on-line monitoring algorithm of the inter-turn short circuit fault, the inter-turn short circuit fault is assumed to occur in the 1 st layer of the A-phase reactor, namely, the innermost layer of the A-phase reactor, at different height positions, the inter-turn short circuit fault does not occur in the B-phase reactor and the C-phase reactor, and at the moment, the inter-turn short circuit fault reactor of the three-phase dry type air-core parallel reactorThe absolute change in loss ratio is shown in Table 2, in which ΔK A ″/ΔK′ A Calculating the ratio of the absolute change quantity of the monitored value to the theoretical change quantity for the fault reactor, namely neglecting the ratio of the loss percentage change quantity of the phase A reactor after the inter-turn short circuit fault to the increase value of the loss percentage absolute change quantity of the phase A reactor after the inter-turn short circuit fault when the neutral point voltage caused by the inter-turn short circuit fault changes;
Table 2 absolute change quantity of loss ratio of turn-to-turn short circuit fault reactor of three-phase dry type hollow shunt reactor
As can be seen from table 2, after the inter-turn short circuit fault occurs at any position of the a-phase reactor, the calculated absolute change of the three-phase loss percentage increases, the absolute change of the a-phase loss percentage is far greater than that of the B-phase and the C-phase loss percentage, the ratio of the calculated value of the a-phase loss percentage to the theoretical value is close to 2/3, the algebraic sum of the calculated three-phase loss percentage change is the same as the theoretical change of the a-phase reactor, and the result is identical with the formulas (18) and (19), so that the on-line monitoring method for the inter-turn short circuit fault of the dry hollow parallel reactor set for the neutral point ungrounded system can effectively find the inter-turn short circuit fault of the dry hollow parallel reactor set and judge the phase sequence of the fault.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of the above description, will appreciate that other embodiments are contemplated within the scope of the invention as described herein. Furthermore, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is defined by the appended claims.

Claims (8)

1. The on-line monitoring method for the turn-to-turn short circuit fault of the dry type hollow parallel reactor of the neutral point ungrounded system is characterized by comprising the following steps of:
s1, calculating electrical parameters of a dry hollow parallel reactor group of a normal operation neutral point ungrounded system;
specific:
s11, calculating to obtain the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s12, calculating neutral point voltage according to the relative deviation between the reactance of the three-phase reactor and the average value thereof and the absolute deviation between the loss percentage of the three-phase reactor and the average value thereof;
s13, obtaining an impedance basic equation of the normal operation reactor group according to the phase sequence relation of the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s2, calculating electrical parameters of the dry type hollow parallel reactor group of the inter-turn short circuit fault neutral point ungrounded system;
specific:
s21, calculating to obtain the reactance of the three-phase reactor after the fault and the loss percentage of the three-phase reactor after the fault;
s22, obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
s3, adopting a normal operation reactor set basic equation as a monitoring algorithm to perform on-line monitoring of the reactor set, and performing inter-turn short circuit fault judgment according to inter-turn short circuit fault judgment conditions;
S4, calculating the absolute change quantity of the loss percentage of the turn-to-turn short circuit fault at the innermost end of the dry hollow shunt reactor, and taking the absolute change quantity as a threshold value for judging the turn-to-turn short circuit.
2. The online monitoring method for turn-to-turn short circuit faults of a dry hollow parallel reactor set for a neutral point ungrounded system according to claim 1, wherein the method is characterized in that the method comprises the following steps of1, for a Y-connected reactor group, the neutral point to ground voltage isThe three-phase voltage is represented by A-phase voltage +.>B-phase voltage->And C phase voltage->The three-phase current is composed of A-phase current +.>Phase B current->And C phase current->The three-phase reactor impedance is composed of A-phase reactor impedance Z A Impedance Z of B-phase reactor B And C-phase reactor impedance Z C Composition;
the three phase voltages are expressed as:
the three-phase current satisfaction condition is expressed as:
combining the formula (1) and the formula (2) to obtain neutral point voltage
Neutral point voltageExpressed as:
in the formula (3), the three-phase reactor impedance is expressed as:
wherein j is an imaginary unit, and the three-phase reactor reactance is represented by an A-phase reactor reactance X A Reactance X of B-phase reactor B And C-phase reactor reactance X C The three-phase reactor loss percentage is composed of an A-phase reactor loss percentage K A Loss percentage K of B-phase reactor B Loss percentage K of C-phase reactor C Composition;
let the average value of the reactance of the three-phase reactor be X AVG The relative deviation of the three-phase reactor reactance from the average value thereof is represented by the relative deviation gamma of the A-phase reactor reactance from the average value thereof XA Relative deviation gamma of reactance of B-phase reactor and average value thereof XB And the relative deviation gamma of the C-phase reactor reactance from its average value XC Composition; let the average value of the loss percentages of the three-phase reactor be K AVG The absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is represented by the absolute deviation delta K of the loss percentage of the A-phase reactor from the average value thereof A Absolute deviation delta K of loss percentage of B-phase reactor from average value B And absolute deviation ΔK of C-phase reactor loss percentage from its average C Composition;
the relative deviation of the three-phase reactor reactance from its average value is expressed as:
the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof is expressed as:
in the formula (5), the relative deviation between the three-phase reactance value and the average value thereof satisfies the condition expressed as:
γ XA +γ XB +γ XC ＝0 (7)
in the formula (6), the absolute deviation of the loss percentage of the three-phase reactor from the average value thereof satisfies the condition expressed as:
ΔK A +ΔK B +ΔK C ＝0 (8)。
3. the method for on-line monitoring of turn-to-turn short circuit faults of a dry type hollow parallel reactor group for a neutral point ungrounded system according to claim 2, wherein in the step S12, three-phase reactor impedance is obtained according to the relative deviation of the three-phase reactor reactance from the average value thereof and the absolute deviation of the three-phase reactor loss percentage from the average value thereof;
The three-phase reactor impedance is expressed as:
substituting the formula (9) into the formula (3), and neglecting the relative deviation of the three-phase reactor reactance and the average value thereof, the three-phase reactor loss percentage and the higher order term and the product term of the absolute deviation of the three-phase reactor loss percentage and the average value thereof to obtain the neutral point voltage
Neutral point voltageExpressed as:
wherein,for zero sequence voltage>For voltage drop caused by unbalance of reactance of three-phase reactor, < >>Voltage drop caused by unbalanced loss percentage of the three-phase reactor.
4. The method for on-line monitoring of turn-to-turn short circuit fault of dry-type hollow parallel reactor set for neutral point ungrounded system as claimed in claim 3, wherein in S13, the voltage drop caused by unbalanced reactance of three-phase reactorAnd voltage drop caused by unbalance of loss percentages of three-phase reactor +.>Wherein, the relative deviation of the three-phase reactor reactance and the average value thereof and the absolute deviation of the three-phase reactor loss percentage and the average value thereof are respectively the real part coefficient and the imaginary part coefficient of the three-phase voltage, and the three-phase reactor impedance is obtained by combining the formula (1) and the formula (10):
the three-phase reactor impedance is expressed as:
obtaining an impedance basic equation of the normal operation reactor group according to the relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
The basic equation for the impedance of a normal operation reactor set is expressed as:
wherein the three-phase positive sequence voltage is composed of A-phase positive sequence voltageB-phase positive sequence voltage->And C-phase positive sequence voltage->The three-phase negative sequence voltage is composed of A-phase negative sequence voltage +.>B phase negative sequence voltage->And C-phase negative sequence voltage->
The relative deviation of the reactance of each reactor and the absolute deviation of the loss percentage in the normal operation dry type hollow parallel reactor group can be obtained through calculation through offline measurement values of the reactance of each reactor and the loss percentage, and after the three-phase voltage and the three-phase current are monitored, the loss percentage monitoring value of each reactor under the normal operation condition can be obtained through analysis type (12).
5. The method for on-line monitoring of inter-turn short circuit fault of dry hollow parallel reactor set for neutral point ungrounded system as claimed in claim 4, wherein in S21, it is assumed that inter-turn short circuit fault occurs in a-phase reactor, and reactance of a-phase reactor after inter-turn short circuit fault is X' A The relative change value of the reactance of the phase A reactor after turn-to-turn short circuit fault is gamma' XA Loss percentage of the phase A reactor after turn-to-turn short circuit fault is K' A The absolute change value of the loss percentage of the phase A reactor after turn-to-turn short circuit fault is delta K' A Obtaining the average value X 'of the reactance of the three-phase reactor after turn-to-turn short circuit fault' AVG Average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG ；
Average value X 'of three-phase reactor reactance after turn-to-turn short circuit fault' AVG Expressed as:
average value K 'of loss percentages of three-phase reactor after turn-to-turn short circuit fault' AVG Expressed as:
according to equation (13), the three-phase reactor reactance after the turn-to-turn short circuit fault is expressed as:
wherein the relative deviation of the three-phase resistor reactance after the inter-turn short circuit fault and the average value thereof is determined by the relative deviation of the A-phase resistor reactance after the inter-turn short circuit fault and the average value thereofAfter turn-to-turn short circuit faultRelative deviation of the B-phase resistor reactance from its average value +.>And the relative deviation of the C-phase resistor reactance from its average value after turn-to-turn short circuit failureComposition;
according to equation (14), the three-phase reactor loss percentage after the turn-to-turn short circuit fault is expressed as:
wherein, the absolute deviation of the loss percentage of the three-phase reactor after the turn-to-turn short circuit fault and the average value thereof is determined by the absolute deviation of the loss percentage of the A-phase reactor after the fault and the average value thereofAbsolute deviation of B-phase reactor loss percentage after turn-to-turn short circuit fault and average value thereof +.>And absolute deviation of C-phase reactor loss percentage from average value after turn-to-turn short circuit fault +. >Composition is prepared.
6. The method for on-line monitoring of turn-to-turn short circuit fault of dry-type hollow parallel reactor set for neutral point ungrounded system as claimed in claim 5, wherein in S22, formula (15) and formula (16) are substituted into formula (3), and the higher order terms of the relative deviation of the three-phase reactor reactance from its average value, the three-phase reactor loss percentage and the absolute deviation of the three-phase reactor loss percentage from its average value are ignored, to obtain neutral point voltage
Neutral point voltageExpressed as:
wherein,the voltage change value of the neutral point caused by turn-to-turn short circuit fault of the phase A reactor is obtained;
substituting the formula (17) into the formula (1), and obtaining an impedance basic equation of the reactor group after turn-to-turn short circuit fault according to the phase sequence relation between the three-phase positive sequence voltage and the three-phase negative sequence voltage;
the fundamental equation for the impedance of the reactor set after the turn-to-turn short circuit fault is expressed as:
wherein,
7. the method for on-line monitoring of inter-turn short circuit fault of dry hollow parallel reactor set for neutral point ungrounded system as claimed in claim 6, wherein in S3, the reactance of three-phase reactor after inter-turn short circuit fault is increased by a value γ' XA And delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A Ignoring the neutral voltage change caused by the turn-to-turn short circuit fault as an unknown quantity, and obtaining an impedance basic equation of the turn-to-turn short circuit fault reactor groupThe loss percentage of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is consistent with the basic equation of the group of the normal operation reactor, under the condition, the loss percentage K' of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored A Loss percentage K' of B-phase reactor after inter-turn short circuit fault when neutral point voltage change caused by inter-turn short circuit fault is ignored B And the loss percentage K' of the C-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored C The composition is calculated to obtain the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored, and the reactance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is the reactance X' of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored A B-phase reactor reactance X' after inter-turn short circuit fault when neutral point voltage change caused by inter-turn short circuit fault is ignored B And C-phase reactor reactance X' after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored C "composition;
the impedance of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
the three-phase positive sequence voltage is far greater than the three-phase negative sequence voltage, and the three-phase reactor impedance difference calculated by the formula (19) and the formula (18) is mainly positive sequence impedance difference;
multiplying the impedance of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored in the formula (19) by coefficients a, b and c in the formula (18) respectively to obtain the loss percentage relation of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored;
the relationship of the loss percentage of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage changes caused by the inter-turn short circuit fault is ignored is expressed as follows:
will K' A ＝K A +ΔK′ A Substituting the three-phase reactor loss percentage variation after the inter-turn short circuit fault when the neutral point voltage variation caused by the inter-turn short circuit fault is ignored into the formula (20);
the loss percentage change quantity of the three-phase reactor after the turn-to-turn short circuit fault when the neutral point voltage change caused by the turn-to-turn short circuit fault is ignored is expressed as:
Wherein, the loss percentage change quantity of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored is the loss percentage change quantity delta K 'of the A-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored' A ' ignoring the loss percentage change delta K ' of the B-phase reactor after the inter-turn short circuit fault when the neutral point voltage is changed caused by the inter-turn short circuit fault ' B "sum of percentage change delta K 'of loss of C-phase reactor after turn-to-turn short circuit fault when neutral point voltage change caused by turn-to-turn short circuit fault is ignored' C ' composition;
adding the loss percentage change quantity of the three-phase reactor after the inter-turn short circuit fault when the neutral point voltage change caused by the inter-turn short circuit fault is ignored to obtain the loss percentage absolute change quantity increase value delta K 'of the three-phase reactor after the inter-turn short circuit fault' A ；
Delta K 'for increasing loss percentage absolute change of three-phase reactor after turn-to-turn short circuit fault' A Expressed as:
ΔK′ A ＝ΔK″ A +ΔK″ B +ΔK″ C (22)
in summary, the calculated increase value of the loss percentage change of the three-phase reactor after the inter-turn short circuit fault is distributed to the three-phase reactors according to different proportions, the absolute change value of the loss percentage of the three-phase reactor after the inter-turn short circuit fault is far greater than the relative change value of the reactance of the three-phase reactor, the calculated loss percentage change of the three-phase reactor after the inter-turn short circuit fault is increased, the loss percentage change value of the A-phase reactor containing the inter-turn short circuit fault is far greater than the loss percentage change value of the other two-phase reactors, and the loss percentage change value of the A-phase reactor is 2/3 of the actual change value;
Adopting a formula (12) or a formula (19) with the same calculation method as a monitoring algorithm, continuously monitoring three-phase voltage to ground and three-phase current, calculating a three-phase reactor loss percentage monitoring value by combining known normal operation reactor impedance, and performing difference value operation on each reactor reactance and loss percentage monitoring value and historical data to obtain absolute variation of loss percentage of each phase reactor;
when an inter-turn short circuit fault occurs at a certain moment, the absolute variation is suddenly changed, and according to the formula (21), the inter-turn short circuit fault judgment condition is deduced to judge the inter-turn short circuit fault;
the inter-turn short circuit fault judgment condition is expressed as: and when the minimum absolute change quantity of the loss percentage of a certain coherent air-core reactor exceeds 2/3 times of the actual change quantity, judging that the phase reactor has turn-to-turn short circuit fault.
8. The method for on-line monitoring turn-to-turn short circuit fault of dry type hollow shunt reactor set for neutral point ungrounded system as claimed in claim 7, wherein in the step S4, in the equivalent circuit of dry type hollow shunt reactor, the dry type hollow shunt reactor is wound in multiple layers, and the equivalent circuit of dry type hollow shunt reactor is built in units of layers under power frequency voltage, For applying voltage>For the current flowing through the reactor, +.>R is the current flowing through each layer of coil 1 ～R n For the resistance of each layer of coil, L 1 ～L n For the self-inductance of each layer of coil, +.>For the induced potential formed by mutual inductance between each coil and other coils, i (i=1) the induction potential of the n) layer coil is +.>
Induced potential of the ith layer coilExpressed as:
wherein j is an imaginary symbol, ω is an angular frequency, M i,k Is the mutual inductance of the ith layer coil and the kth layer coil;
establishing a voltage equation set of an equivalent circuit of the dry-type hollow shunt reactor;
the voltage equation set of the equivalent circuit of the dry type hollow shunt reactor is expressed as follows:
wherein,the equivalent resistance of each layer of coil of the equivalent circuit of the dry-type air-core parallel reactor is equal to that of each layer of coilThe resistance, self inductance and mutual inductance between coils are determined by the structure of the reactor group and the characteristics of metal materials, n equations and current variables are arranged in the formula (24), and the current of each layer of coil can be analyzed;
total current flowing through the reactorExpressed as:
the impedance value Z of the dry hollow shunt reactor is expressed as:
wherein X is a reactance value, and K is a loss percentage;
in the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor, the fault layer coil can be divided into two parts under the assumption that the ith layer coil has 1 turn of short circuit fault, the short circuit turns form an n+1th branch, and the rest turns form an ith branch;
Establishing a voltage equation set of an equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor;
the voltage equation set of the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor is expressed as:
wherein,for the equivalent resistance of each layer of coil of the equivalent circuit of the turn-to-turn short circuit fault dry type hollow shunt reactor, the equation (27) forms n+1 equations, n+1 current variables exist, each current value is obtained by solving the equation set, and the current flowing through the reactor does not contain any currentThe current containing the short-circuit turns is analyzed by using a formula (25) and a formula (26) to obtain the reactance and loss percentage of the turn-to-turn short-circuit fault reactor; the method is characterized in that the loss percentage variation is minimum after the inter-turn short circuit fault occurs at the innermost end of the dry type hollow parallel reactor is deduced, the absolute variation of the inter-turn short circuit fault loss percentage at the innermost end of the dry type hollow parallel reactor is calculated through theory, 2/3 times of the absolute variation is taken as a threshold for judging the inter-turn short circuit, and the inter-turn short circuit fault occurring at any position of the threshold can be effectively judged.
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Publication number Priority date Publication date Assignee Title
CN1652424A (en) * 2005-01-13 2005-08-10 天津大学 Protecting method for short-circuit between wire coils of parallel reactor of ultrahigh voltage transmission line
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US20170227594A1 (en) * 2016-02-10 2017-08-10 General Electric Company Systems and Methods for Detecting Turn-to-Turn Faults in Windings
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CN109856510A (en) * 2018-12-24 2019-06-07 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 A kind of lookup method of inter-turn insulation defect of dry hollow reactor position

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1652424A (en) * 2005-01-13 2005-08-10 天津大学 Protecting method for short-circuit between wire coils of parallel reactor of ultrahigh voltage transmission line
US20170227594A1 (en) * 2016-02-10 2017-08-10 General Electric Company Systems and Methods for Detecting Turn-to-Turn Faults in Windings
CN106786368A (en) * 2016-12-26 2017-05-31 云南电网有限责任公司电力科学研究院 The guard method of the dry type hollow shunt reactor based on voltage-phase variable quantity
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