Dry-type air-core reactor non-metallic turn-to-turn insulation short circuit fault protection system and method

Abstract

The invention discloses a non-metallic turn-to-turn insulation short-circuit fault protection system and method for a dry-type air-core reactor, and relates to the technical field of online fault monitoring. At the initial stage of a turn-to-turn short circuit fault, only a power factor is monitored, and the fault is difficult to effectively identify and warn timely. According to the structure parameters of the dry-type air-core reactor, the loss value of each layer of coil and the normal power factor value under the normal condition are obtained, the total loss value of the turn-to-turn short circuit fault layer coil is obtained through the preset fault power factor value, and the temperature distribution of each package under the normal condition and the fault condition is obtained according to the two loss values. Establishing a power factor threshold value according to the two power factor values, obtaining a real-time power factor value according to the actually measured voltage and current, and when the difference value between the actually measured power factor value and the normal power factor value is greater than the power factor threshold value, determining that the power factor value is smaller than the normal power factor value. And meanwhile, when the temperature value of any one package collected in real time is greater than the corresponding package temperature threshold value, judging that the dry-type air-core reactor has a fault. The method is used for detecting the dry-type air-core reactor.

Description

Technical Field

[0001] This invention relates to the field of online fault monitoring technology. Background Technology

[0002] Dry-type air-core reactors have advantages such as simple structure, light weight, small size, good linearity, low loss, and convenient maintenance. They can compensate for reactive power, suppress power frequency overvoltage, limit short-circuit overcurrent, and filter high-order harmonics, and are widely used in power systems.

[0003] During operation, dry-type air-core reactors are subjected to switching overvoltages and thermal stresses. These stresses can damage the encapsulation insulation, causing it to crack and allowing rainwater and dirt to enter the reactor. This gradually deteriorates the inter-turn insulation, eventually leading to inter-turn insulation breakdown and causing an inter-turn short-circuit fault. In the early stages of an inter-turn short-circuit fault, the reactor current changes very little, and the overcurrent protection cannot operate in time. The fault gradually develops into a single-phase short circuit or a phase-to-ground short circuit before protection is activated, potentially causing a fire. This seriously affects the safe and stable operation of the power grid, and also brings huge economic losses and adverse social impacts.

[0004] After an inter-turn short circuit fault in a dry-type air-core reactor, a non-metallic short circuit fault develops. Compared to a metallic short circuit fault, a non-metallic short circuit fault results in a larger short-circuit turn resistance, a smaller circulating current, less loss, and a smaller change in power factor. Therefore, in the early stages of an inter-turn short circuit fault, monitoring only the power factor is insufficient for effective fault identification and timely early warning. Thus, it is necessary to explore a new method and system for protecting dry-type air-core reactors against non-metallic inter-turn insulation short circuit faults, enabling real-time monitoring of the reactor's operating status and ensuring its safe and stable operation. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing methods, which rely solely on power factor monitoring, are insufficient for effective fault identification and timely early warning in the early stages of inter-turn short-circuit faults. This invention proposes a protection system and method for non-metallic inter-turn insulation short-circuit faults in dry-type air-core reactors.

[0006] A method for protecting a dry-type air-core reactor against non-metallic inter-turn insulation short-circuit faults, the method comprising the following:

[0007] Step 1: Based on the structural parameters of the dry-type air-core reactor, establish a system of voltage equations and solve for the phasor values ​​of the coil currents in each layer of the dry-type air-core reactor under normal conditions. Based on this phasor value, the coil loss values ​​of each layer of the dry-type air-core reactor under normal conditions are obtained. Normal power factor value of dry-type air-core reactor under normal conditions ;

[0008] Step 2: Preset the fault power factor of the dry-type air-core reactor under non-metallic inter-turn insulation short-circuit fault conditions. ,according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. ;

[0009] Step 3, according to Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions; based on and Obtain the temperature distribution of each encapsulation when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor;

[0010] Based on the temperature distribution of each enclosure when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, the average value of all temperatures along the height direction of each enclosure is calculated as the average temperature of each enclosure. The average temperature of each package is selected from the temperature distribution of each package when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor. Equal temperature points correspond to heights Under normal circumstances, the dry-type air-core reactor is encapsulated at the corresponding height. Temperature at the location ;

[0011] Step 4, according to and Establish power factor threshold ;according to and Establish temperature thresholds for each encapsulation. ;

[0012] Step 5: Real-time acquisition of voltage and current across the dry-type air-core reactor, and real-time acquisition of temperature values ​​for each package. Based on the real-time acquired voltage and current, calculate the real-time power factor. When the real-time power factor differs from the normal power factor... The difference is greater than the power factor threshold. At the same time, when the temperature value of any package is collected in real time and is greater than the temperature threshold of the corresponding package... When a fault is detected in the dry-type air-core reactor, the dry-type air-core reactor is disconnected, thus protecting it. Preferably, in step 1, the coil loss values ​​P of each layer of the dry-type air-core reactor under normal conditions are obtained based on the phasor value. i Normal power factor value of dry-type air-core reactor under normal conditions The specific process is as follows:

[0013] Phasor values ​​of current in each layer of a dry-type air-core reactor under normal conditions Represented as:

[0014] Formula 1,

[0015] In the formula, This represents the real part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions. The imaginary unit, This represents the imaginary part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions.

[0016] Total current phasor value flowing through dry-type air-core reactor Represented as:

[0017] Formula 2,

[0018] according to and The current amplitude of each layer of the dry-type air-core reactor under normal conditions was obtained. and total current amplitude :

[0019] Formula 3,

[0020] Formula 4,

[0021] according to Obtain the coil loss values ​​of each layer of a dry-type air-core reactor under normal conditions. for:

[0022] Formula 5,

[0023] In the formula, The resistance of each layer of coils in a dry-type air-core reactor;

[0024] according to Obtain normal power factor for:

[0025] Formula 6,

[0026] In the formula, It is a resistive current. , This represents the total number of coils.

[0027] Preferably, in step 2, according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. The specific process:

[0028] Assuming a nonmetallic inter-turn short-circuit fault occurs in the k-th layer coil of a dry-type air-core reactor, the magnitude of the resistive current in the faulty reactor is... For the sum of total current amplitude They are represented as follows:

[0029] Formula 7,

[0030] Formula 8,

[0031] In the formula, Let be the real part of the current in the k-th layer coil during a nonmetallic inter-turn short-circuit fault. This represents the real part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions.

[0032] Represented as:

[0033] Formula 9,

[0034] Transform Equation 9 into:

[0035] Formula 10,

[0036] Set the preset fault power factor value Substituting into Equation 10, we obtain the real part of the current in the k-th layer coil during a nonmetallic inter-turn short-circuit fault. ;

[0037] according to Obtain the current amplitude of the k-th layer coil. :

[0038] Formula 11,

[0039] according to Obtain the loss value of the k-th layer coil. :

[0040] Formula 12,

[0041] In the formula, The resistance of the k-th layer coil of a dry-type air-core reactor under normal conditions;

[0042] according to Obtain the short-circuit turn loss of the dry-type air-core reactor. :

[0043] Formula 13,

[0044] In the formula, , This represents the total loss of a dry-type air-core reactor during non-metallic inter-turn short-circuit faults. Apply an external voltage to both ends of the dry-type air-core reactor. This represents the total current amplitude of the dry-type air-core reactor. This refers to the coil loss in the non-short-circuit fault layer;

[0045] according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. for:

[0046] Formula 14.

[0047] Preferably, in step 3, according to The specific process for obtaining the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions is as follows:

[0048] Under normal circumstances, dry-type air-core reactors, according to The heat generation rate per unit volume of the internal coil of each package is:

[0049] Formula 15,

[0050] In the formula, For the first Heat generation rate per unit volume of the encapsulated internal coil , This represents the total number of packages. Let m be the number of coils inside the m-th envelope. For the first The volume of the coil;

[0051] According to the heat conduction equation for each unit volume of the enclosure:

[0052] Formula 16,

[0053] Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions. ;

[0054] In the formula, denoted as thermal conductivity, r as polar coordinate, and z as vertical coordinate.

[0055] Preferably, in step 3, according to and The specific process for obtaining the temperature distribution of each encapsulation in a dry-type air-core reactor during a non-metallic inter-turn short-circuit fault is as follows:

[0056] When a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, if the encapsulation does not contain the short-circuit coil, according to... The heat generation rate per unit volume of the internal coil of each package is:

[0057] Formula 17,

[0058] In the formula, For the first The volume of the coil;

[0059] If the encapsulation contains a short-circuited coil, according to The heat generation rate per unit volume of the internal coil of each package is:

[0060] Formula 18,

[0061] In the formula, For the first Heat generation rate per unit volume of the encapsulated internal coil , This represents the total number of packages. This represents the number of coils inside the m-th envelope.

[0062] According to the heat conduction equation for each unit volume of the enclosure:

[0063] or Formula 19,

[0064] Obtain the temperature distribution of each encapsulation under fault conditions of dry-type air-core reactor. ;

[0065] In the formula, denoted as thermal conductivity, r as polar coordinate, and z as vertical coordinate.

[0066] Preferably, the power factor threshold Represented as:

[0067] Formula 20;

[0068] Temperature threshold for each package Represented as:

[0069] Formula 21.

[0070] Preferably, in step 5, the real-time power factor is calculated based on the real-time collected voltage and current. The specific process is as follows:

[0071] The initial phase of the real-time acquired voltage signal is calculated using harmonic analysis. and the initial phase of the current signal They are respectively:

[0072] Formula 22,

[0073] Formula 23,

[0074] In the formula, This represents the real part of the first voltage harmonic component. This represents the imaginary part of the first voltage harmonic component. This represents the real part of the first current harmonic component. This represents the imaginary part of the first harmonic component of the current. , , , , This is the voltage collected in real time. The current is collected in real time. The fundamental frequency;

[0075] The real-time power factor is obtained based on the initial phase of the voltage and current signals. for:

[0076] Formula 24.

[0077] Preferably, in step 5, the temperature value of each package is collected in real time, specifically as follows:

[0078] Real-time collection of each package height The temperature value at that location.

[0079] A non-metallic inter-turn insulation short-circuit fault protection system for dry-type air-core reactors, the system comprising a current transformer and a voltage transformer. The system includes a temperature sensor, signal conditioning circuit, A / D converter, embedded computer, optocoupler isolator, photoelectric converter, host computer, station control layer monitoring module, and protection action module.

[0080] One temperature sensor is used to collect data in real time. The temperature signal of each package is sent to the signal conditioning circuit;

[0081] The voltage transformer and current transformer respectively collect the voltage and current across the dry-type air-core reactor in real time and send them to the signal conditioning circuit;

[0082] Signal conditioning circuit, used for... The temperature signal of the package, the voltage and current across the dry air reactor are adjusted, and then input to the A / D converter for analog-to-digital conversion. The output digital signal is then input to the embedded computer.

[0083] An embedded computer is used to calculate the initial phase of the voltage and current signals of a dry-type air-core reactor using harmonic analysis. The temperature signal of each package is transmitted to the host computer sequentially through an optocoupler isolator and a photoelectric converter.

[0084] The host computer is used to calculate the real-time power factor based on the initial phase of the received voltage and current signals from the dry-type air-core reactor, and then compare the real-time power factor with... The temperature signal of each package is transmitted to the station control layer monitoring module;

[0085] The station control layer monitoring module establishes a power factor threshold. and the temperature threshold for each package When the real-time power factor value differs from the normal power factor The difference is greater than the power factor threshold. Meanwhile, when the temperature value of any package is detected in real time to be greater than the temperature threshold of the corresponding package... When a fault is detected in the dry-type air-core reactor, the control protection action module switches off the dry-type air-core reactor.

[0086] Preferably, a power factor threshold is established within the station control layer monitoring module. and the temperature threshold for each package The process is as follows:

[0087] Based on the structural parameters of the dry-type air-core reactor, a set of voltage equations is established, and the phasor values ​​of the coil currents in each layer of the dry-type air-core reactor under normal conditions are solved. Based on this phasor value, the coil loss values ​​of each layer of the dry-type air-core reactor under normal conditions are obtained. Normal power factor value of dry-type air-core reactor under normal conditions ;

[0088] Preset fault power factor of dry-type air-core reactor under non-metallic inter-turn insulation short-circuit fault conditions ,according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. ;

[0089] according to Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions; based on and Obtain the temperature distribution of each encapsulation when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor;

[0090] Based on the temperature distribution of each enclosure when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, the average value of all temperatures along the height direction of each enclosure is calculated as the average temperature of each enclosure. The average temperature of each package is selected from the temperature distribution of each package when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor. Equal temperature points correspond to heights Under normal circumstances, the dry-type air-core reactor is encapsulated at the corresponding height. Temperature at the location ;

[0091] according to and Establish power factor threshold ;according to and Establish temperature thresholds for each encapsulation. ;

[0092] A temperature sensor is set sequentially The height corresponding to each package This location is used to collect the height of each package in real time. Temperature signal at the location.

[0093] The beneficial effects of this invention are:

[0094] When the difference between the real-time power factor and the normal power factor obtained at the same time exceeds the corresponding threshold for any of the envelope temperatures, the dry-type air-core reactor is disconnected, thus protecting the dry-type air-core reactor. This invention uses both temperature and power factor as alarm conditions simultaneously, effectively avoiding false alarms caused by transient processes during the switching on or off of the dry-type air-core reactor, as well as by sudden changes in power factor due to grid voltage fluctuations, thereby increasing the accuracy and reliability of early warning.

[0095] This invention obtains the temperature distribution and average temperature of non-metallic inter-turn insulation short-circuit faults, accurately calculates the reactor encapsulation temperature, and sets alarm thresholds. At the same time, it clarifies the installation location of the temperature sensor, avoiding the uncertainty of the location of inter-turn short circuits in dry-type air-core reactors, which leads to the blind installation of temperature sensors and makes it impossible to accurately measure the reactor temperature. Attached Figure Description

[0096] Figure 1 This is the equivalent circuit diagram of a dry-type air-core reactor under normal conditions.

[0097] Figure 2 Equivalent circuit diagram of a dry-type air-core reactor for inter-turn short-circuit fault;

[0098] Figure 3 Diagram showing the installation location of the temperature sensor;

[0099] Figure 4 This is a schematic diagram of a non-metallic inter-turn insulation short-circuit fault protection system for dry-type air-core reactors.

[0100] Figure 5 This is a schematic diagram of the internal workings of the host computer.

[0101] Figure 6A flowchart of a method for protecting dry-type air-core reactors against non-metallic inter-turn insulation short-circuit faults.

[0102] Figure 7 A comparison chart of encapsulation loss values ​​under normal conditions and non-metallic inter-turn short-circuit faults;

[0103] Figure 8 A comparison chart of the average temperatures of each encapsulation under normal conditions and non-metallic inter-turn short-circuit faults;

[0104] Figure 9 This is a comparison diagram of the axial height temperature distribution of each encapsulation under normal conditions and non-metallic inter-turn short-circuit faults. Detailed Implementation

[0105] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0106] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0107] Example 1:

[0108] Combination Figure 6 This embodiment describes a method for protecting a dry-type air-core reactor against non-metallic inter-turn insulation short-circuit faults. The method includes the following:

[0109] Step 1: Based on the structural parameters of the dry-type air-core reactor, establish a system of voltage equations and solve for the phasor values ​​of the coil currents in each layer of the dry-type air-core reactor under normal conditions. Based on this phasor value, the coil loss values ​​of each layer of the dry-type air-core reactor under normal conditions are obtained. Normal power factor value of dry-type air-core reactor under normal conditions ;

[0110] Step 2: Preset the fault power factor of the dry-type air-core reactor under non-metallic inter-turn insulation short-circuit fault conditions. ,according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. ;

[0111] Step 3, according to Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions; based on and Obtain the temperature distribution of each encapsulation when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor;

[0112] Based on the temperature distribution of each enclosure when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, the average value of all temperatures along the height direction of each enclosure is calculated as the average temperature of each enclosure. The average temperature of each package is selected from the temperature distribution of each package when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor. Equal temperature points correspond to heights Under normal circumstances, the dry-type air-core reactor is encapsulated at the corresponding height. Temperature at the location ;

[0113] Step 4, according to and Establish power factor threshold ;according to and Establish temperature thresholds for each encapsulation. ;

[0114] Step 5: Real-time acquisition of voltage and current across the dry-type air-core reactor, and real-time acquisition of temperature values ​​for each package. Based on the real-time acquired voltage and current, calculate the real-time power factor. When the real-time power factor differs from the normal power factor... The difference is greater than the power factor threshold. At the same time, when the temperature value of any package is collected in real time and is greater than the temperature threshold of the corresponding package... When a fault is detected in the dry-type air-core reactor, the dry-type air-core reactor is disconnected, thus achieving protection for the dry-type air-core reactor.

[0115] Specifically, when a dry-type air-core reactor experiences an inter-turn short-circuit fault, monitoring the temperature of each encapsulation can pinpoint the location of the faulty encapsulation, facilitating subsequent reactor maintenance; for example, if the temperature of the first encapsulation exceeds the corresponding encapsulation temperature threshold... If so, it indicates that the package is faulty.

[0116] Further specifying, in step 1, based on this phasor value, the coil loss values ​​P of each layer of the dry-type air-core reactor under normal conditions are obtained. i Normal power factor value of dry-type air-core reactor under normal conditions The specific process is as follows:

[0117] Phasor values ​​of current in each layer of a dry-type air-core reactor under normal conditions Represented as:

[0118] Formula 1,

[0119] In the formula, This represents the real part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions. The imaginary unit, This represents the imaginary part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions.

[0120] Total current phasor value flowing through dry-type air-core reactor Represented as:

[0121] Formula 2,

[0122] according to and The current amplitude of each layer of the dry-type air-core reactor under normal conditions was obtained. and total current amplitude :

[0123] Formula 3,

[0124] Formula 4,

[0125] according to Obtain the coil loss values ​​of each layer of a dry-type air-core reactor under normal conditions. for:

[0126] Formula 5,

[0127] In the formula, The resistance of each layer of coils in a dry-type air-core reactor;

[0128] according to Obtain normal power factor for:

[0129] Formula 6,

[0130] In the formula, It is a resistive current. , This represents the total number of coils.

[0131] Specifically, a dry-type air-core reactor has an axisymmetric structure, consisting of multiple layers of coils wound in parallel. Each layer of coil can be equivalently represented by the induced potential formed by the resistance of the conductors, self-inductance, and mutual inductance. The equivalent circuit established on a layer-by-layer basis is as follows: Figure 1 As shown in the figure: For external voltage, The current flowing through the reactor, R is the current flowing through each layer of coils. L1 ~RLn Let L1~L be the resistance of the wires in each layer of the coil. n The self-inductance of each layer of coils, e1~e n It is the algebraic sum of the induced electromotive forces formed by the mutual inductance between each layer of coils and other coils.

[0132] The permeability of free space, and The number of turns per unit length for the two coils. and The height of the two coils, and Let be the radii of the two coils. The center-to-center distance between two coils, and the mutual inductance between any two coils. for:

[0133]

[0134] In the formula:

[0135] ,

[0136] , , , .

[0137] Pick and The self-inductance of any coil can be obtained. for:

[0138]

[0139] Each coil is wound with aluminum wire, where ρ is the resistivity of the aluminum wire at 20°C, α is the temperature coefficient, and d... i Let t be the diameter, t be the reactor operating temperature, t0 be 20°C, and the resistance of any coil be:

[0140]

[0141] The algebraic sum of the induced potentials of the i-th layer coil is:

[0142]

[0143] Establish Figure 1 The voltage equations:

[0144]

[0145] Further specifying, in step 2, according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. The specific process:

[0146] Assuming a nonmetallic inter-turn short-circuit fault occurs in the k-th layer coil of a dry-type air-core reactor, in the initial short period of the fault, the self-inductance and mutual inductance of all layers of coils and the short-circuited coil remain unchanged. The resistance of all layers of coils, except for the short-circuited coil, also remains unchanged. During the inter-turn short circuit, only the current of the faulted layer coil changes, while the currents of the other layers remain constant. For the faulted layer coil, the real part of the reactor current increases, while the imaginary part remains unchanged. The equivalent circuit of the reactor containing the inter-turn short-circuit fault is as follows: Figure 2 As shown.

[0147] In the picture, For external voltage, The current flowing through the reactor, R is the current flowing through each layer of coils and the short-circuit turns. L1 ~R Ln+1 The resistance of each layer of coil and short-circuit turn, L1~L n+1 For the self-inductance of each layer of coils and short-circuit turns, e1~e n+1 This refers to the induced potential formed by the mutual inductance between each layer of coils and the short-circuit turns and other coils.

[0148] Establish Figure 2 The voltage equations are:

[0149]

[0150] The equations consist of n+1 equations and have n+1 current variables. When the reactor forms a non-metallic short circuit, the short-circuit turn resistance cannot be obtained through theoretical calculation. Therefore, this set of voltage equations cannot be analyzed.

[0151] Let the phasor current of the k-th layer coil be the value of a nonmetallic short-circuit fault. for:

[0152]

[0153] In the formula: Let b be the real part of the current in the k-th layer coil during a nonmetallic inter-turn short-circuit fault. k This represents the imaginary part of the current in the k-th layer coil of the reactor under normal conditions, where j is the imaginary unit.

[0154] Assuming a nonmetallic inter-turn short-circuit fault occurs in the k-th layer coil of a dry-type air-core reactor, the magnitude of the resistive current in the faulty reactor is... For the sum of total current amplitude They are represented as follows:

[0155] Formula 7,

[0156] Formula 8,

[0157] In the formula, Let be the real part of the current in the k-th layer coil during a nonmetallic inter-turn short-circuit fault. This represents the real part of the current in each layer of the coils of a dry-type air-core reactor under normal conditions.

[0158] Represented as:

[0159] Formula 9,

[0160] Transform Equation 9 into:

[0161] Formula 10,

[0162] Set the preset fault power factor value Substituting into Equation 10, we obtain the real part of the current in the k-th layer coil during a nonmetallic inter-turn short-circuit fault. ;

[0163] according to Obtain the current amplitude of the k-th layer coil. :

[0164] Formula 11,

[0165] according to Obtain the loss value of the k-th layer coil. :

[0166] Formula 12,

[0167] In the formula, The resistance of the k-th layer coil of a dry-type air-core reactor under normal conditions;

[0168] according to Obtain the short-circuit turn loss of the dry-type air-core reactor. :

[0169] Formula 13,

[0170] In the formula, , This represents the total loss of a dry-type air-core reactor during non-metallic inter-turn short-circuit faults. Apply an external voltage to both ends of the dry-type air-core reactor. This represents the total current amplitude of the dry-type air-core reactor. This refers to the coil loss in the non-short-circuit fault layer;

[0171] according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. for:

[0172] Formula 14.

[0173] Further specifying, in step 3, according to The specific process for obtaining the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions is as follows:

[0174] Under normal circumstances, dry-type air-core reactors, according to The heat generation rate per unit volume of the internal coil of each package is:

[0175] Formula 15,

[0176] In the formula, For the first Heat generation rate per unit volume of the encapsulated internal coil , This represents the total number of packages. Let m be the number of coils inside the m-th envelope. For the first The volume of the coil;

[0177] According to the heat conduction equation for each unit volume of the enclosure:

[0178] Formula 16,

[0179] Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions. ;

[0180] In the formula, denoted as thermal conductivity, r as polar coordinate, and z as vertical coordinate.

[0181] Further specifying, in step 3, according to and The specific process for obtaining the temperature distribution of each encapsulation in a dry-type air-core reactor during a non-metallic inter-turn short-circuit fault is as follows:

[0182] When a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, if the encapsulation does not contain the short-circuit coil, according to... The heat generation rate per unit volume of the internal coil of each package is:

[0183] Formula 17,

[0184] In the formula, For the first The volume of the coil;

[0185] If the encapsulation contains a short-circuited coil, according to The heat generation rate per unit volume of the internal coil of each package is:

[0186] Formula 18,

[0187] In the formula, For the first Heat generation rate per unit volume of the encapsulated internal coil , This represents the total number of packages. This represents the number of coils inside the m-th envelope.

[0188] According to the heat conduction equation for each unit volume of the enclosure:

[0189] or Formula 19,

[0190] Obtain the temperature distribution of each encapsulation under fault conditions of dry-type air-core reactor. ;

[0191] In the formula, denoted as thermal conductivity, r as polar coordinate, and z as vertical coordinate.

[0192] Specifically, the dry-type air-core reactor dissipates heat through thermal conduction inside the package. Each package consists of multiple branch coils. Therefore, the heat conduction equation is established using the heat generation rate per unit volume of each package.

[0193] Further restrictions, power factor threshold Represented as:

[0194] Formula 20;

[0195] Temperature threshold for each package Represented as:

[0196] Formula 21.

[0197] Further specifying step 5, the real-time power factor is calculated based on the real-time collected voltage and current. The specific process is as follows:

[0198] The initial phase of the real-time acquired voltage signal is calculated using harmonic analysis. and the initial phase of the current signal They are respectively:

[0199] Formula 22,

[0200] Formula 23,

[0201] In the formula, This represents the real part of the first voltage harmonic component. This represents the imaginary part of the first voltage harmonic component. This represents the real part of the first current harmonic component. This represents the imaginary part of the first harmonic component of the current. , , , , This is the voltage collected in real time. The current is collected in real time. The fundamental frequency;

[0202] The real-time power factor is obtained based on the initial phase of the voltage and current signals. for:

[0203] Formula 24.

[0204] Specifically, let the voltage and current of the detected signal on the dry-type air-core reactor be U(t) and I(t), respectively, which can be expressed as follows through Fourier series expansion:

[0205]

[0206]

[0207] In the formula: f is the fundamental frequency, A uk and A ik Let a be the amplitude of the kth harmonic. uk and a ik b is the real part of the k-th harmonic component; uk and b ik φ is the imaginary part of the k-th harmonic component. uk and φ ik This represents the initial phase of the kth harmonic.

[0208] Further specifying, in step 5, the temperature value of each package is collected in real time, specifically as follows:

[0209] Real-time collection of each package height The temperature value at that location.

[0210] Specifically, the temperature sensor of the outermost enclosure of the reactor is installed on the inner surface of the enclosure, while the other enclosure sensors are installed on the outer surface of the enclosure. A schematic diagram of the temperature sensor installation positions is shown below. Figure 3 As shown.

[0211] Example 2:

[0212] Combination Figure 4 and Figure 5 This embodiment describes a non-metallic inter-turn insulation short-circuit fault protection system for dry-type air-core reactors. The system includes a current transformer, a voltage transformer, and... The system includes a temperature sensor, signal conditioning circuit, A / D converter, embedded computer, optocoupler isolator, photoelectric converter, host computer, station control layer monitoring module, and protection action module.

[0213] One temperature sensor is used to collect data in real time. The temperature signal of each package is sent to the signal conditioning circuit;

[0214] The voltage transformer and current transformer respectively collect the voltage and current across the dry-type air-core reactor in real time and send them to the signal conditioning circuit;

[0215] Signal conditioning circuit, used for... The temperature signal of the package, the voltage and current across the dry air reactor are adjusted, and then input to the A / D converter for analog-to-digital conversion. The output digital signal is then input to the embedded computer.

[0216] An embedded computer is used to calculate the initial phase of the voltage and current signals of a dry-type air-core reactor using harmonic analysis. The temperature signal of each package is transmitted to the host computer sequentially through an optocoupler isolator and a photoelectric converter.

[0217] The host computer is used to calculate the real-time power factor based on the initial phase of the received voltage and current signals from the dry-type air-core reactor, and then compare the real-time power factor with... The temperature signal of each package is transmitted to the station control layer monitoring module;

[0218] The station control layer monitoring module establishes a power factor threshold. and the temperature threshold for each package When the real-time power factor value differs from the normal power factor The difference is greater than the power factor threshold. Meanwhile, when the temperature value of any package is detected in real time to be greater than the temperature threshold of the corresponding package... When a fault is detected in the dry-type air-core reactor, the control protection action module switches off the dry-type air-core reactor.

[0219] Further restrictions are imposed, and a power factor threshold is established within the station control layer monitoring module. and the temperature threshold for each package The process is as follows:

[0220] Based on the structural parameters of the dry-type air-core reactor, a set of voltage equations is established, and the phasor values ​​of the coil currents in each layer of the dry-type air-core reactor under normal conditions are solved. Based on this phasor value, the coil loss values ​​of each layer of the dry-type air-core reactor under normal conditions are obtained. Normal power factor value of dry-type air-core reactor under normal conditions ;

[0221] Preset fault power factor of dry-type air-core reactor under non-metallic inter-turn insulation short-circuit fault conditions ,according to Obtain the total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor. ;

[0222] according to Obtain the temperature distribution of each encapsulation in a dry-type air-core reactor under normal conditions; based on and Obtain the temperature distribution of each encapsulation when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor;

[0223] Based on the temperature distribution of each enclosure when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor, the average value of all temperatures along the height direction of each enclosure is calculated as the average temperature of each enclosure. The average temperature of each package is selected from the temperature distribution of each package when a nonmetallic inter-turn short-circuit fault occurs in a dry-type air-core reactor. Equal temperature points correspond to heights Under normal circumstances, the dry-type air-core reactor is encapsulated at the corresponding height. Temperature at the location ;

[0224] according to and Establish power factor threshold ;according to and Establish temperature thresholds for each encapsulation. ;

[0225] A temperature sensor is set sequentially The height corresponding to each package This location is used to collect the height of each package in real time. Temperature signal at the location.

[0226] Specifically, the protection action module is implemented using a circuit breaker.

[0227] Experimental verification:

[0228] Taking a BKK-20000 / 63 dry-type air-core reactor as an example, the reactor loss and temperature distribution are calculated. The reactor parameters are shown in Table 1.

[0229] Table 1 Overall parameters of dry-type air-core reactors

[0230]

[0231] Set power factor The alarm threshold is 0.1%. Taking a non-metallic inter-turn short-circuit fault in the first-layer coil as an example, calculate the encapsulation losses of each component in the reactor. The encapsulation losses under normal conditions and non-metallic inter-turn short-circuit faults are as follows: Figure 7 As shown.

[0232] Further calculations of the temperature distribution in the dry-type air-core reactor, under normal conditions and non-metallic inter-turn short-circuit faults, show the average temperature distribution of each encapsulation and the axial height temperature distribution of the first encapsulation as follows: Figure 8 and Figure 9 As shown.

[0233] from Figure 9 It can be seen that the average temperature of the first package of the nonmetallic inter-turn short-circuit fault reactor is... The temperature is 97℃, corresponding to an axial height of 1.25 meters. Therefore, the temperature sensor is installed at a height of 1.17 meters above the inner surface of the first package. At this axial height, the temperature of the first package under normal conditions... The temperature is 52℃. Therefore, the first packaging temperature alarm threshold is... Set to 45℃.

[0234] Similarly, the loss value and temperature distribution of each package are calculated sequentially to determine the installation location of the temperature sensor and set the temperature alarm threshold for each package.

[0235] The system compares real-time voltage, current, and temperature readings with alarm thresholds to detect dry-type air-core reactors.

[0236] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for protection against a non-metallic turn-to-turn insulation short circuit fault in a dry-type air-core reactor, characterized in that, The method comprises the following contents: Step 1, according to the structure parameters of the dry-type air-core reactor, a voltage equation set is established, and the current phasor value of each layer coil of the dry-type air-core reactor under normal condition is solved , according to the phasor value, the loss value of each layer coil of the dry-type air-core reactor under normal condition is obtained and the normal power factor value of the dry-type air-core reactor under normal condition ; Step 2, fault power factor value of preset dry-type air-core reactor under non-metallic inter-turn insulation short-circuit fault condition , according to obtaining total loss value of inter-turn short-circuit fault layer coil of dry-type air-core reactor ; Step 3, according to obtain the temperature distribution of each package of the dry-type air-core reactor under normal conditions; according to and obtain the temperature distribution of each package of the dry-type air-core reactor when a non-metallic turn-to-turn short circuit fault occurs According to the temperature distribution of each package when the non-metallic turn-to-turn short circuit fault occurs in the dry-type air-core reactor, the average value of all temperatures in the height direction of each package is calculated as the average temperature of each package , the average temperature of each package is selected from the temperature distribution of each package when the non-metallic turn-to-turn short circuit fault occurs in the dry-type air-core reactor The height corresponding to the equal temperature point , the temperature of each package at the corresponding height of the dry-type air-core reactor under normal conditions is selected ; Step 4, establishing a power factor threshold value and Step 5, establishing a temperature threshold value for each package ; according to and Step 6, establishing a temperature threshold value for each package ; Step 5, real-time acquisition of the voltage and current at both ends of the dry-type air-core reactor, and real-time acquisition of the temperature value of each package, according to the real-time acquisition of the voltage and current, calculation of the real-time power factor value, when the difference between the real-time power factor value and the normal power factor value is greater than the power factor threshold value , and at the same time when the temperature value of any one package is greater than the temperature threshold of the corresponding package , it is determined that the dry-type air-core reactor is faulty, and the dry-type air-core reactor is removed, thereby realizing protection of the dry-type air-core reactor.

2. The dry-type air-core reactor non-metallic inter-turn insulation short circuit fault protection method according to claim 1, characterized in that, In step 1, according to the phasor value, the loss value P of each layer coil of the dry-type air-core reactor under normal condition is obtained i and the normal power factor value under normal condition of the dry-type air-core reactor The specific process is as follows: The phase value of each layer coil current of dry-type air-core reactor under normal condition is represented as: Formula 1, wherein is the real part of the current of each layer of the dry-type air-core reactor under normal conditions, is the imaginary unit, is the imaginary part of the current of each layer of the dry-type air-core reactor under normal conditions; Total current phasor value flowing through dry-type air-core reactor is expressed as: Formula 2, According to and , the current amplitude of each layer of the dry-type air-core reactor under normal conditions and the total current amplitude are obtained, respectively: Formula 3, Formula 4, According to Obtaining the loss value of each layer coil of the dry-type air-core reactor under normal conditions is: Formula 5, In the formula, R is the resistance of each layer of the dry-type air-core reactor coil; According to obtaining normal power factor values is: Formula 6, wherein is a resistive current, , is the total number of coils.

3. The dry-type air-core reactor non-metallic inter-turn insulation short circuit fault protection method according to claim 2, characterized in that, In step 2, according to The total loss value of the inter-turn short-circuit fault layer coil of the dry-type air-core reactor is obtained The specific process is as follows: Assuming that the kth layer coil of the dry-type air-core reactor has a non-metallic turn-to-turn short circuit fault, the resistive current amplitude of the fault reactor is The total current amplitude is Respectively, Formula 7, Formula 8, In the formula, is the real part of the current of the kth layer of coils for the non-metallic inter-turn short circuit fault, is the real part of the current of each layer of coils under normal conditions of the dry-type air-core reactor; is represented as: Formula 9, The formula 9 is transformed into: Formula 10, The preset fault power factor value Bringing formula 10, the current real part of the kth layer coil of the non-metallic inter-turn short circuit fault is obtained ; According to , the k-th layer coil current amplitude : Formula 11, According to , obtaining a kth layer coil loss value : Formula 12, In the formula, Rk is the resistance of the kth layer of the dry-type air-core reactor under normal conditions. According to , the short-circuit turn loss of the dry-type air-core reactor is obtained : Formula 13, In the formula, , is the total loss of the dry-type air-core reactor for non-metallic inter-turn short-circuit fault, is the external voltage applied to the dry-type air-core reactor, is the total current amplitude of the dry-type air-core reactor, is the loss of the layer coil for non-short-circuit fault; According to , the total loss value of the dry-type air-core reactor inter-turn short-circuit fault layer coil is obtained : Formula 14.

4. The dry-type air-core reactor non-metallic inter-turn insulation short circuit fault protection method according to claim 2, characterized in that, In step 3, according to The temperature distribution of each package of the dry-type air-core reactor under normal conditions is obtained, and the specific process is as follows: Under normal circumstances, according to The heat generation rate per unit volume of the encapsulated internal coil is obtained as: Formula 15, wherein is the total number of encapsulations, is the volumetric heat generation rate of the mthencapsulated internal coil, , is the total number of encapsulations, is the number of the mthencapsulated internal coil, is the volumetric heat generation rate of the mthencapsulated internal coil, is the volume of the coil; According to the heat conduction equation of each encapsulated unit volume: Formula 16, Obtaining temperature distribution of each package of dry-type air-core reactor under normal condition ; wherein k is the thermal conductivity, r is the polar coordinate, and z is the vertical coordinate.

5. The dry-type air-core reactor non-metallic turn-to-turn insulation short circuit fault protection method according to claim 4, characterized in that, In step 3, according to and obtain the temperature distribution of each package when the dry-type air-core reactor occurs a non-metallic inter-turn short circuit fault, the specific process is as follows: When the non-metallic turn-to-turn short circuit fault occurs in the dry-type air-core reactor, if the short-circuit turn coil is not contained in the encapsulation inner part, according to The heat generation rate per unit volume of the coil in each encapsulation inner part is obtained as: Formula 17, In the formula, is the first Volume of the coil; If the encapsulated interior contains a shorted turn coil, according to The volumetric heat generation rate per encapsulated interior coil unit is obtained as: Formula 18, wherein is the total number of encapsulations, is the heat generation rate per volume of the mthencapsulated internal coil, , is the total number of encapsulations, is the number of mthencapsulated internal coils; According to the heat conduction equation of each encapsulated unit volume: or Equation 19, Obtaining temperature distribution of each package under fault condition of dry-type air-core reactor ; wherein k is the thermal conductivity, r is the polar coordinate, and z is the vertical coordinate.

6. The dry-type air-core reactor non-metallic turn-to-turn insulation short circuit fault protection method according to claim 5, characterized in that, Power factor threshold is represented as: Formula 20; Temperature threshold for each package is represented as: Formula 21.

7. The dry-type air-core reactor non-metallic turn-to-turn insulation short circuit fault protection method according to claim 1, characterized in that, In step 5, the real-time power factor value is calculated according to the real-time collected voltage and current The specific process is as follows: The initial phase of the voltage signal and the initial phase of the current signal are calculated using a harmonic analysis method on the real-time collected signals and respectively Formula 22, Formula 23, wherein is the real part of the first voltage harmonic component, is the imaginary part of the first voltage harmonic component, is the real part of the first current harmonic component, is the imaginary part of the first current harmonic component, , , , , is the real-time acquired voltage, is the real-time acquired current, is the fundamental frequency; From the initial phase of the voltage and current signals, a real-time power factor value is obtained is: Formula 24.

8. The dry-type air-core reactor non-metallic inter-turn insulation short circuit fault protection method according to claim 7, characterized in that, In step 5, the temperature value of each encapsulation is collected in real time, specifically: Real-time acquisition of temperature values at each encapsulation height Real-time acquisition of temperature values at each encapsulation height 9. A dry-type air-core reactor non-metallic turn-to-turn insulation short-circuit fault protection system, characterized by, The system comprises a current transformer, a voltage transformer, a temperature sensor, a signal conditioning circuit, an A / D converter, an embedded computer, an optical coupling isolator, an optical-electric converter, an upper computer, a station control layer monitoring module and a protection action module. a temperature sensor for real-time acquisition of an encapsulated temperature signal to the signal conditioning circuit; The voltage transformer and the current transformer collect the voltage and the current at two ends of the dry-type air-core reactor in real time respectively and send to the signal conditioning circuit; Signal conditioning circuit for conditioning the encapsulated temperature signal, the voltage and current across the dry-type air-core reactor, and inputting the conditioned signals to an A / D converter for analog-to-digital conversion, and outputting digital signals to an embedded computer; The embedded computer is used for calculating the initial phase of the dry-type air-core reactor voltage and current signal by using harmonic analysis method, and the initial phase of the dry-type air-core reactor voltage and current signal and The encapsulated temperature signal is transmitted to the upper computer through the optical coupling isolator and the photoelectric converter in sequence. The upper computer is used for calculating real-time power factor value according to the initial phase of the received dry-type air-core reactor voltage and current signals, and transmitting the real-time power factor value and The temperature signal is transmitted to the station control layer monitoring module. The station control layer monitoring module internally establishes a power factor threshold and a temperature threshold for each package ; When the real-time power factor value is different from the normal power factor The difference is greater than the power factor threshold. Meanwhile, when the temperature value of any package is detected in real time to be greater than the temperature threshold of the corresponding package... When a fault is detected in the dry-type air-core reactor, the control protection action module switches off the dry-type air-core reactor.

10. The dry-type air-core reactor non-metallic turn-to-turn insulation short circuit fault protection system according to claim 9, characterized in that, The station control layer monitoring module internally establishes a power factor threshold value and a temperature threshold value for each package The process is as follows: According to the structure parameters of the dry-type air-core reactor, a voltage equation set is established, and each layer coil current phasor value of the dry-type air-core reactor under normal condition is solved According to the phasor value, each layer coil loss value of the dry-type air-core reactor under normal condition is obtained and the normal power factor value of the dry-type air-core reactor under normal condition ; The preset dry-type air-core reactor fault power factor value under the non-metallic inter-turn insulation short circuit fault condition , according to obtaining the total loss value of the inter-turn short circuit fault layer coil of the dry-type air-core reactor ; According to obtain the temperature distribution of each package of the dry-type air-core reactor under normal conditions; according to and obtain the temperature distribution of each package of the dry-type air-core reactor when a non-metallic turn-to-turn short circuit fault occurs According to the temperature distribution of each package when the non-metallic turn-to-turn short circuit fault occurs in the dry-type air-core reactor, the average value of all temperatures in the height direction of each package is calculated as the average temperature of each package , the average temperature of each package is selected from the temperature distribution of each package when the non-metallic turn-to-turn short circuit fault occurs in the dry-type air-core reactor The height corresponding to the equal temperature point , the temperature of each package at the corresponding height of the dry-type air-core reactor under normal conditions is selected ; According to and , a power factor threshold is established; according to and , a temperature threshold is established for each package; A temperature sensor is sequentially arranged at A corresponding height of the package At this height, the temperature signal of each package is collected in real time. At this height, the temperature signal of each package is collected in real time.

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