CN109459657A - A kind of method of isolated neutral system ferromagnetic resonance real-time detection and diagnosis - Google Patents
A kind of method of isolated neutral system ferromagnetic resonance real-time detection and diagnosis Download PDFInfo
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- CN109459657A CN109459657A CN201811199931.3A CN201811199931A CN109459657A CN 109459657 A CN109459657 A CN 109459657A CN 201811199931 A CN201811199931 A CN 201811199931A CN 109459657 A CN109459657 A CN 109459657A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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Abstract
The present invention relates to the methods of a kind of isolated neutral system ferromagnetic resonance real-time detection and diagnosis.It include: that the resonant tank differential equation is established, and derived the calculation method of ferromagnetic resonance operating point according to ferromagnetic resonance parallel inductance-capacitance resonance computation model；The accuracy that parallel inductance-capacitance model and numerical value calculate is demonstrated using electromagnetical transient emulation method；On the basis of foregoing work, resonant operational point magnetic flux virtual value is calculated according to C-V characteristic data；Compared with the aforementioned resonant operational point magnetic flux for calculating determination, whether diagnosis voltage transformer enters resonant operational point.To realize in isolated neutral system fluctuation, judge that voltage transformer whether close to resonant operational point, that is, realizes the real-time detection and diagnosis of ferromagnetic resonance.
Description
The present invention relates to isolated neutral power distribution network operational safety fields, ferromagnetic when fluctuating more particularly, to electric system
The diagnosis of resonance.
Background technique
Ferromagnetic resonance is one of the main inducing that overvoltage is generated in Operation of Electric Systems, in recent years in low and medium voltage distribution network
In frequently occur；Domestic and foreign scholars generate process to ferromagnetic resonance and calculation method has carried out numerous studies, and propose inhibition
The measure of resonance, but the application effect of certain measures is bad, and viewpoint is different.Analyzing reason is the mathematical modulo of ferromagnetic resonance
Type is incomplete, causes to be biased the analysis of resonance suppressing method.
In isolated neutral distribution network, it is electric over the ground that electromagnetic potential transformer (TV) is widely used in monitoring system
Pressure.In recent years, since cable largely uses, grid structure and load type more sophisticated；Route switching and generation single-phase short circuit
When failure, transformer or mutual inductor iron core is be easy to cause to be saturated, coil induction reactance value reduces humorous with the generation of system direct-to-ground capacitance circuit
Vibration causes ferro-resonance over-voltage, endangers power network safety operation.Therefore accurate to calculate ferro-resonance over-voltage and analysis
Its influence factor is of great significance.
Summary of the invention
The object of the invention is in order to guarantee power network safety operation, can in real time Accurate Diagnosis ferromagnetic resonance and
A kind of new method provided.This method utilizes ferromagnetic resonance parallel inductance-capacitance resonance computation model, and analysis system is disturbed
When dynamic, whether voltage transformer, which can enter resonant operational point, occurs resonance to cause whole system, while according to inductance-electricity
Hold parallel resonance and calculate resonant operational point magnetic flux numerical value, proposes a kind of new ferromagnetic resonance real-time detection and diagnostic method, prediction
Its potential risk that may be present, to carry out maintenance preparation or prevention work in advance.,
To achieve the above object, can be realized by following technical approach: isolated neutral system ferromagnetic resonance is real
When detection with diagnosis new method, which comprises the following steps:
Step 1 establishes the resonant tank differential equation according to ferromagnetic resonance parallel inductance-capacitance resonance computation model, derives
The calculation method of ferromagnetic resonance operating point, voltage, the current value of voltage transformer at solving system resonant operational point；
Step 2 is according to the fitting formula of electromagnetic potential transformer magnetization curve, voltage at computing system resonant operational point
Mutual inductor magnetic flux virtual value；
Step 3 is directed to practical power distribution network, the exciting current of real-time detection voltage transformer, and then according to voltage transformer magnetic
Change curve and calculates magnetic flux virtual value；
The resonant operational point magnetic flux that step 4 calculates voltage transformer magnetic flux virtual value that step 3 calculates and step 2 is effective
Value compares, when voltage transformer magnetic flux virtual value is more than resonant operational point magnetic flux virtual value, it is believed that power distribution network occurs ferromagnetic humorous
Vibration.
Detailed description of the invention
Fig. 1 is ferromagnetic resonance real-time detection flow chart of the invention.
Fig. 2 is isolated neutral system equivalent parallel resonant illustraton of model of the invention.
Fig. 3 is φ-i performance data matched curve figure of the invention.
Fig. 4 is isolated neutral system actual track illustraton of model of the invention.
Fig. 5 is voltage transformer flux curve figure of the invention.
Fig. 6 is middle 10kV busbar voltage waveform diagram of the invention.
Specific embodiment
The present invention is described in detail with reference to the accompanying drawing.
As shown in Figure 1, isolated neutral system ferromagnetic resonance real-time detection and diagnostic method, which is characterized in that including
Following steps:
Step 1 establishes resonance according to ferromagnetic resonance parallel inductance-capacitance resonance computation model according to circuit correlation theory
The circuit differential equation, and derived the calculation method of ferromagnetic resonance operating point；Its detailed process includes:
As shown in Figure 2 wherein, E is electrical source voltage, X to the parallel circuit model of equivalent ferromagnetic resonanceSFor source reactance, C is
System direct-to-ground capacitance, L and R are respectively voltage transformer equivalent inductance and resistance, indicate voltage transformer mould using cascade
Type.WithIt is X respectivelySWith voltage transformer both end voltage, iLIt is voltage transformer exciting current.Nonlinear inductance L's
Magnetization characteristic is shown below
iL=f (φ)=a φ+b φ3+…+φk(k=5 ..., 2n-1) (1)
In formula, φ is transformer magnetic linkage, and ω is system frequency.
Generally exciting current is analyzed in the case where k=3, magnetization characteristic formula is as follows at this time.
Wherein, a, b > 0, φ are voltage transformer magnetic fluxs.It is availableWithExpression formula:
IfThe circuit differential equation is obtained using Kirchhoff's second law (KVL):
Using harmonic wave equilibrium method, the solution of nonlinear equation is set as to the form of each harmonic superposition, only takes fundametal compoment, suddenly
Slightly other harmonic components.Assuming that:
The circuit differential equation is substituted into, only retains fundamental component, and handle using triangle relation, obtains:
Formula (7) is about φ2Cubic equation, ignore the influence of inductive resistance R, enable x=φ2, it is converted into one about x
First cubic equation f (x).To equation derivation, derived function discriminate is obtained:
Δ=482b2[XS(aXS-CXSω2)+48bω]2-108(b2ω2+b2XS 2)[(aXS-CXSω2)2+1] (8)
Meet aXS-CXSω2When≤0, Δ≤0.Then f (x) is monotonically increasing function.
Second derived function f " (x) discriminate of f (x):
Δ '=48bXS(aXS-CXSω2)+48bω≥0 (9)
Resonant operational state is not present without real root, i.e. system in equation φ at this time, and there is no φ to meet KVL equation, that is, uses
Now disturbance makes φ change, and is also regulated and controled due to resonant operational point is not present for circuit by power supply E, thus disturbance suppression.Abbreviation is
a≥Cω2.So only meeting a >=C ω2, it is likely to generate fundamental-frequency ferroresonce.
By formula (2) to t derivation, primary conditionWhen, it can obtainAccording to inductance element characteristic
Derivation obtainsTherefore it under primary condition, can obtainWherein L0It is the initial inductance of TV nonlinear inductance, it is humorous
Vibration condition can be changed toPhysical significance be TV primary side nonlinear inductance value be greater than system direct-to-ground capacitance value be ferromagnetic
The necessary condition that resonance occurs.
The practical distribution network line parameter of step 2 pair carries out equivalent calculation, voltage transformer at solving system resonant operational point
Voltage, current value and according to the fitting formula of step 3 electromagnetic potential transformer magnetization curve, computing system resonant operational
Voltage transformer magnetic flux virtual value at point.
(1) voltage transformer magnetization characteristic
Select the φ-i performance data of 10kV bus-bar potential transformer as shown in table 1.
1 voltage transformer φ-i performance data of table
It is fitted back magnetization characteristic curve using formula (1), fitting result is as shown in Figure 3.Root-mean-square error 5.802 is fitted excellent
Degree is 0.9648, and degree of fitting is higher.φ-i function expression is i after fittingL+ 0.001031 φ of=- 0.5229 φ3, i.e. a=-
0.5229, b=0.001031.
(2) line parameter circuit value model
Choose certain power grid 10kV distribution line as shown in figure 4, power supply be 35kV, be connected to 10kV bus by transformer.
Source reactance XSIt is 5.292, system direct-to-ground capacitance C is 20uF.10kV bus-bar potential transformer uses open delta wiring side
Formula, high-pressure side neutral-point solid ground.
(3) resonance point magnetic flux calculates
Bring parameter above into formula (7)
(9b2ω2+9b2XS 2)φ6+[24bXS(aXS-CXSω2)+24bω]φ4+16[(aXS-CXSω2)2+1]φ2-32E2
=0 calculates, and obtains the numerical solution 36.91Wb of magnetic flux φ.
When the circuit switching method of operation, singlephase earth fault occurs or other failures increase voltage, electric current increases, makes
Voltage transformer magnetic flux saturation, when magnetic flux increases to 36.91Wb, reaches resonant operational point, will be in the route mould of above-mentioned calculating
Ferromagnetic resonance occurs in type.
Step 4 is write program and is calculated in real time voltage transformer flux value, the resonant operational calculated with step 3 formula
Point magnetic flux compares, and whether diagnosis voltage transformer is more than resonant operational point, excites resonance.
Based on the method for magnetization characteristic detection, pass through test voltage mutual inductor voltage-to-current (U-I) data, conversion
Empirical equation according to the voltage transformer exciting current value of actual measurement calculates magnetic three times for magnetic flux shown in an accepted way of doing sth (1) and exciting current
Be connected with valid value, and calculate resonant operational point magnetic flux in conjunction with formula above, judge simulation model in the case where disturbance, voltage
Whether mutual inductor can enter resonant operational point, and then diagnose whether excite ferromagnetic resonance.Detailed process is as shown in Figure 1.
Simulation Model of Ferroresonance is established using PSCAD/EMTDC software, verifies the validity of proposed diagnostic method.
Simulation model is built, A phase short trouble, trouble duration 0.2s occurs when route 0.2s is set.Obtain voltage transformer magnetic
Logical curve is as shown in Figure 5.
As seen from the figure, when system disturbs, overvoltage and overcurrent occur for voltage transformer, and magnetic flux virtual value increases
Greatly, ferromagnetic resonance, electric current and voltage spikes are excited after reaching the i.e. φ set=36.91Wb of resonant operational point calculated above, entirely
Ferromagnetic resonance occurs for system.10kV busbar voltage waveform is as shown in Figure 6.
After single-phase fault disappears, big ups and downs occur for busbar voltage, and peak value is about 1.4 times of normal voltage value.Therefore, it is based on
The ferromagnetic resonance detection and diagnosis method that magnetic flux virtual value calculates has certain practical significance, mutually ties with formula calculation method above
It closes, ferromagnetic resonance is measured in real time in actual track.
The present invention calculates method, solving system resonant operational point, analyzing influence resonance by parallel inductance-capacitance model value
Factor, and verified and be applied in electromagnetic transient simulation software is realized to the real-time detection of ferromagnetic resonance and accurate
Diagnosis guarantees power network safety operation, and it is possible to prevente effectively from accident caused by ferromagnetic resonance.
Claims (5)
1. a kind of isolated neutral system ferromagnetic resonance real-time detection and diagnostic method characterized by comprising
Step 1 establishes the resonant tank differential equation according to ferromagnetic resonance parallel inductance-capacitance resonance computation model, derives ferromagnetic
The calculation method of resonant operational point, voltage, the current value of voltage transformer at solving system resonant operational point；
Step 2 is according to the fitting formula of electromagnetic potential transformer magnetization curve, mutual induction of voltage at computing system resonant operational point
Device magnetic flux virtual value；
Step 3 is directed to practical power distribution network, the exciting current of real-time detection voltage transformer, and then magnetizes song according to voltage transformer
Line computation magnetic flux virtual value；
The resonant operational point magnetic flux virtual value ratio that step 4 calculates the voltage transformer magnetic flux virtual value that step 3 calculates with step 2
Compared with when voltage transformer magnetic flux virtual value is more than resonant operational point magnetic flux virtual value, it is believed that ferromagnetic resonance occurs for power distribution network.
2. ferromagnetic resonance parallel inductance-capacitance resonance computation model according to claim 1, establishes resonant tank differential side
Journey derives the calculation method of ferromagnetic resonance operating point, voltage, the current value of voltage transformer at solving system resonant operational point,
It is characterized in that,WithIt is X respectivelySWith voltage transformer both end voltage, iLIt is voltage transformer exciting current.It is non-linear
The magnetization characteristic of inductance L is shown below
iL=f (φ)=a φ+b φ3+…+φk(k=5 ..., 2n-1) (1)
In formula, φ is transformer magnetic linkage, and ω is system frequency.
Generally exciting current is analyzed in the case where k=3, magnetization characteristic formula is as follows at this time.
Wherein, a, b > 0, φ are voltage transformer magnetic fluxs.It is availableWithExpression formula:
IfThe circuit differential equation is obtained using Kirchhoff's second law (KVL):
Using harmonic wave equilibrium method, the solution of nonlinear equation is set as to the form of each harmonic superposition, fundametal compoment is only taken, ignores it
His harmonic component.Assuming that:
The circuit differential equation is substituted into, only retains fundamental component, and handle using triangle relation, obtains:
Formula (7) is about φ2Cubic equation, ignore the influence of inductive resistance R, enable x=φ2, it is converted into the unitary three about x
Equation of n th order n f (x).To equation derivation, derived function discriminate is obtained:
Δ=482b2[XS(aXS-CXSω2)+48bω]2-108(b2ω2+b2XS 2)[(aXS-CXSω2)2+1] (8)
Meet aXS-CXSω2When≤0, Δ≤0.Then f (x) is monotonically increasing function.
Second derived function f " (x) discriminate of f (x):
Δ '=48bXS(aXS-CXSω2)+48bω≥0 (9)
Resonant operational state is not present without real root, i.e. system in equation φ at this time, and there is no φ to meet KVL equation, even if disturbing
It is dynamic that φ is made to change, also regulated and controled due to resonant operational point is not present for circuit by power supply E, thus disturbance suppression.Abbreviation is a >=C
ω2.So only meeting a >=C ω2, it is likely to generate fundamental-frequency ferroresonce, therefore solve resonant operational point magnetic flux according to formula (7)
φ, that is, system resonance operating point, while the voltage and current at system resonance operating point can be sought according to TV magnetization characteristic
Value.
3. according to claim 1 be directed to practical power distribution network, the exciting current of real-time detection voltage transformer, and then basis
Voltage transformer magnetization curve calculates magnetic flux virtual value, which is characterized in that brings the parameter of practical power systems into formula (7)
(9b2ω2+9b2XS 2)φ6+[24bXS(aXS-CXSω2)+24bω]φ4+16[(aXS-CXSω2)2+1]φ2-32E2=0
It calculates, obtains the numerical solution of magnetic flux φ.
When the circuit switching method of operation, singlephase earth fault occurs or other failures increase voltage, electric current increases, makes voltage
Mutual inductor magnetic flux saturation reaches resonant operational point when magnetic flux increases above magnetic flux φ numerical solution or in the case of other disturbances, just
Ferromagnetic resonance can occur in the circuit model of above-mentioned calculating.
4. the resonant operational that voltage transformer magnetic flux virtual value and step 2 that step 3 according to claim 1 calculates calculate
Point magnetic flux virtual value compares, when voltage transformer magnetic flux virtual value is more than resonant operational point magnetic flux virtual value, it is believed that power distribution network
Ferromagnetic resonance occurs.
5. isolated neutral system ferromagnetic resonance real-time detection according to claim 1 and diagnostic method, described in step 6
The method based on magnetization characteristic detection, which is characterized in that by test voltage mutual inductor voltage-to-current (U-I) data,
It is converted into magnetic flux and exciting current empirical equation three times, according to the voltage transformer exciting current value of actual measurement, it is effective to calculate magnetic flux
Value, and resonant operational point magnetic flux is calculated in conjunction with formula above, simulation model is judged in the case where disturbance, and voltage transformer is
It is no to enter resonant operational point, it is diagnosed to be and whether excites ferromagnetic resonance.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111813000A (en) * | 2020-06-11 | 2020-10-23 | 广西电网有限责任公司电力科学研究院 | Method and device for simulating ferromagnetic resonance of power distribution network real-time test platform |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111813000A (en) * | 2020-06-11 | 2020-10-23 | 广西电网有限责任公司电力科学研究院 | Method and device for simulating ferromagnetic resonance of power distribution network real-time test platform |
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