CN111879996B - Transient overvoltage back calculation method based on electromagnetic voltage transformer - Google Patents
Transient overvoltage back calculation method based on electromagnetic voltage transformer Download PDFInfo
- Publication number
- CN111879996B CN111879996B CN202010649855.2A CN202010649855A CN111879996B CN 111879996 B CN111879996 B CN 111879996B CN 202010649855 A CN202010649855 A CN 202010649855A CN 111879996 B CN111879996 B CN 111879996B
- Authority
- CN
- China
- Prior art keywords
- excitation
- voltage transformer
- voltage
- electromagnetic
- model
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000004364 calculation method Methods 0.000 title claims abstract description 38
- 230000001052 transient effect Effects 0.000 title claims abstract description 29
- 230000005284 excitation Effects 0.000 claims abstract description 121
- 230000009977 dual effect Effects 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 32
- 238000012360 testing method Methods 0.000 claims abstract description 24
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 21
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 18
- 230000005415 magnetization Effects 0.000 claims abstract description 12
- 238000012544 monitoring process Methods 0.000 claims abstract description 6
- 238000004804 winding Methods 0.000 claims description 36
- 230000004907 flux Effects 0.000 claims description 24
- 230000005291 magnetic effect Effects 0.000 claims description 24
- 230000006870 function Effects 0.000 claims description 16
- 230000009466 transformation Effects 0.000 claims description 10
- 238000002955 isolation Methods 0.000 claims description 6
- 238000004422 calculation algorithm Methods 0.000 claims description 5
- 230000008878 coupling Effects 0.000 claims description 4
- 238000010168 coupling process Methods 0.000 claims description 4
- 238000005859 coupling reaction Methods 0.000 claims description 4
- 230000007246 mechanism Effects 0.000 claims description 3
- 230000010354 integration Effects 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 6
- 239000011162 core material Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000011160 research Methods 0.000 description 5
- 238000009413 insulation Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000005350 ferromagnetic resonance Effects 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000012886 linear function Methods 0.000 description 2
- 230000008447 perception Effects 0.000 description 2
- 238000010183 spectrum analysis Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000012795 verification Methods 0.000 description 2
- 229910000976 Electrical steel Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000007726 management method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
- 238000010223 real-time analysis Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000012502 risk assessment Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16504—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the components employed
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0046—Arrangements for measuring currents or voltages or for indicating presence or sign thereof characterised by a specific application or detail not covered by any other subgroup of G01R19/00
- G01R19/0053—Noise discrimination; Analog sampling; Measuring transients
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
- G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
- Protection Of Transformers (AREA)
Abstract
The invention discloses a transient overvoltage back calculation method based on an electromagnetic voltage transformer, which mainly comprises the following steps: 1) Establishing an electromagnetic dual pi model of the voltage transformer; 2) Carrying out open-circuit test on the electromagnetic dual pi model of the voltage transformer; 3) Carrying out a short circuit test on the electromagnetic dual pi model of the voltage transformer; 4) Establishing an excitation curve when the two excitation branches are deeply saturated; 5) Combining a single-value magnetization curve when the two excitation branches are not saturated and an excitation curve when the two excitation branches are deeply saturated, so that the saturation characteristic of the iron core of the voltage transformer is represented; 6) And monitoring the secondary side overvoltage of the voltage transformer in real time, and inverting and calculating the time sequence waveform data of the primary side overvoltage according to the kirchhoff voltage and current law and the volt-ampere relation of each element in the PT electromagnetic dual pi model. The invention can accurately measure the transient overvoltage in the power system through the secondary distortion voltage of the transformer and the transformer model, and can reflect the time sequence evolution process of the real overvoltage accident.
Description
Technical Field
The invention relates to the electric power technology, in particular to a low-frequency or high-amplitude transient overvoltage back calculation method based on an electromagnetic voltage transformer.
Background
Overvoltage is an important expression form of an electromagnetic transient process of a power grid, has important influence on insulation reliability of electrical equipment, insulation coordination of a system, relay protection and operation control, and is one of important factors threatening safe and reliable operation of the power grid. Overvoltage research always penetrates through important stages of power transmission and distribution equipment and system safety of a power system: overvoltage is an important basis for insulation coordination design and verification, is an important factor for accident tracing, equipment insulation risk assessment and maintenance in operation, and is also an important reference for equipment retirement decision. The electric power system has a series of overvoltage protection measures such as lightning rod, lightning conductor, lightning arrester and lightning grounding, but overvoltage phenomenon still occurs and causes a series of accidents such as breakdown, discharge, flashover, explosion and the like of electric equipment. The online overvoltage monitoring can realize online capturing and real-time analysis of overvoltage waveforms, and provides real first-hand data for inversion, management and numerical simulation research of overvoltage accidents.
The voltage transformer is a main device for acquiring overvoltage signals of a power system, a core electromagnetic induction unit is an iron core, and intrinsic physical defects exist when overvoltage (overvoltage full-wave data) with wide width and broadband characteristics is monitored: the high-amplitude overvoltage can cause the saturation of the iron core, so that the waveform of the secondary side voltage is seriously distorted; the dynamic magnetization process of the voltage transformer iron core has frequency dependence, so that the effective sensing frequency of the voltage transformer is not more than 500Hz, and the fundamental problem of limiting the overvoltage full-wave monitoring is solved. In view of the above, from the standpoint of establishing a broadband model of the voltage transformer, a method for truly restoring the primary side voltage waveform is proposed, and a certain research result is obtained, for example, the following two methods:
1) And establishing an overvoltage inversion calculation model according to the secondary side voltage signal and the broadband transmission characteristic of the voltage transformer. The broadband transmission characteristic is obtained by measuring with a vector network analyzer, the excitation signal is small, the network function is linear, and the saturation nonlinear effect of the iron core is not considered.
2) A traditional T-shaped equivalent circuit of the voltage transformer is connected with a black box model in parallel, a broadband nonlinear parallel extension model of the voltage transformer is established, the saturation effect of an iron core can be considered, but the T-shaped equivalent circuit has inherent physical defects when simulating the deep saturation of the iron core, and has larger errors when simulating a low-frequency or high-amplitude transient process.
Disclosure of Invention
The invention aims to provide a low-frequency or high-amplitude transient overvoltage back calculation method based on an electromagnetic voltage transformer so as to improve the perceptibility of the voltage transformer for low-frequency transient voltages. The low-frequency or high-amplitude transient overvoltage back calculation method based on the electromagnetic voltage transformer mainly comprises the following steps of:
1) And establishing a voltage transformer electromagnetic dual pi model considering the geometric and physical structure based on the transformer electromagnetic dual model and a winding and iron core electromagnetic coupling mechanism. The primary winding of the voltage transformer is equivalent to an ideal transformer I, and the secondary winding is equivalent to an ideal transformer II. The electromagnetic dual pi model of the voltage transformer is provided with two excitation branches which are respectively marked as an excitation branch I and an excitation branch II. The capacitance between the primary winding and the secondary winding in the electromagnetic dual pi model of the voltage transformer and the capacitance of the secondary side of the voltage transformer can be ignored when the working characteristics of low-frequency or high-amplitude transient voltage are studied.
2) Standard open circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that the exciting resistance R of two exciting branches of the electromagnetic dual pi model is determined m1 、R m2 And respectively establishing single-value magnetization curves when the two excitation branches are not saturated.
3) Short-circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that leakage inductance L of the electromagnetic dual pi model is determined s And winding resistance R s Is a numerical value of (2). Measuring the DC resistance of the winding, and setting the winding resistance R according to the DC resistance s The winding resistance distributed to two sides of the electromagnetic dual pi model of the voltage transformer is set as R s1 The winding resistance of the secondary side is R s2 。
4) The method comprises the steps of taking an alternating current/direct current hybrid power supply as an excitation source, testing excitation inductances of a voltage transformer iron core under different saturation degrees, considering the difference of excitation characteristics of excitation branches of different ports of the voltage transformer, providing a port excitation curve distribution method based on a circuit model, and respectively obtaining deep saturation inductances L of two excitation branches according to a distribution principle m1_s And deep saturation inductance L m2_s . Deep saturation of two excitation branchesThe inductance is converted into a data point of a deep saturation section of the excitation curve, and the excitation curve when the two excitation branches are deeply saturated is established. The AC/DC hybrid power supply comprises a function generator and a power amplifier. The function generator generates excitation pulses, amplifies the excitation pulses by the power amplifier and sends the excitation pulses to the voltage transformer.
When the voltage transformer works in a non-saturation region, two excitation inductances of the pi model are far larger than leakage inductance, the influence of the leakage inductance can be ignored, and the method for distributing the port excitation inductances comprises the following steps: the magnetic flux and the excitation resistance are equally distributed to the two excitation branches.
Wherein, the magnetic flux, current and resistance of the two excitation curves respectively satisfy the following formula:
ψ 1 ＝ψ 2 ＝ψ (1)
R m1 ＝R m2 ＝2R m (3)
where ψ represents magnetic flux. i represents current, R m Representing the resistance. The subscript 1 indicates the excitation branch I. The subscript 2 indicates the excitation branch II.
When the voltage transformer works in a saturation region, the deep saturation inductance L of the two excitation curves m1_s And deep saturation inductance L m2_s The allocation is as follows:
where n is the secondary side discrete data sequence number, n=1, 2,3, … …. Psi phi type s1 (n)、ψ s2 (n) represents the nth discrete magnetic flux data of the two excitation curves, respectively. i.e s1 (n)、i s2 (n) represents the nth discrete current data of the two excitation curves, respectively.
The currents of the two excitation curves respectively meet the following formula:
i s1 (n)+i s2 (n)＝i s (n) (7)
wherein i is s (n) is the nth discrete total current data of the two excitation curves.
5) And combining a single-value magnetization curve when the two excitation branches are not saturated and an excitation curve when the two excitation branches are deeply saturated, so that the saturation characteristic of the iron core of the voltage transformer is represented.
6) And deducing the volt-ampere characteristics of the electromagnetic element in the dual pi model based on the kirchhoff voltage, the current law and the PT electromagnetic to obtain a discrete inversion algorithm based on a back calculation circuit model, monitoring the secondary side voltage data of the voltage transformer in real time, and performing inversion calculation to obtain the time sequence waveform data of the primary side overvoltage.
The main steps of back-calculating the time sequence waveform data of the primary side overvoltage are as follows:
6.1 According to the transformation characteristic and the isolation characteristic of the voltage transformer, the number of turns of the primary side coil and the number of turns of the secondary side coil of the voltage transformer are set to satisfy the following formula:
wherein N is 1 : n represents the transformation characteristic of the voltage transformer, k is the transformation ratio of the electromagnetic voltage transformer, and the value of k depends on the turn ratio of the primary side winding and the secondary side winding. N: n (N) 2 And the isolation characteristic of the electromagnetic voltage transformer is represented.
6.2 When low-frequency or high-amplitude transient overvoltage acts on PT, the voltage transformer works in a saturated or deep saturated state, and current i flowing through the exciting inductance at the moment Lm1 And i Lm2 The magnetic flux shows nonlinear characteristics with the excitation inductance, namely, the following nonlinear function is satisfied:
i Lm1 ＝f Lm1 (ψ 1 )。i Lm2 ＝f Lm2 (ψ 2 ) (9)
wherein f Lm1 (ψ 1 )、f Lm2 (ψ 2 ) Respectively represent the magnetic flux psi with respect to the excitation branch I 1 And magnetic flux ψ about the excitation branch II 2 Is a non-linear function of (2).
Wherein, excitation inductance L m2 The interlinkage magnetic flux ψ of (2) satisfies the following equation:
wherein u is 3 Exciting inductance L for secondary side exciting branch of voltage transformer m2 A voltage across the terminals. Δt is the nth discrete voltage data u 3 (n) and n-1 th discrete voltage data u 3 (n-1) time difference between the two.
6.3 Calculating the secondary side excitation branch voltage u 3 The method comprises the following steps:
wherein u is 2 Is the secondary side voltage of the voltage transformer.
6.4 From leakage inductance L s The leakage inductance voltage is calculated according to the volt-ampere characteristic of the transformer, and the main steps are as follows:
6.4.1 Establishment of leakage inductance voltage u) Ls Is a continuous integral function of (1), namely:
wherein i is Rm1 For flowing through exciting resistor R m1 Is set in the above-described range).
6.4.2 -converting the continuous integral function (12) into a differential algebraic equation, namely:
wherein i is Ls (n) is the leakage inductance L s Is the nth discrete current data of (a).
6.4.3 Solving the formula (13) to obtain leakage inductance voltage u Ls 。
6.5 Calculating primary side excitation branch voltage u 5 The method comprises the following steps:
6.6 Calculating primary side current i of voltage transformer Rs1 The method comprises the following steps:
6.8 Calculating the primary-side port voltage u) 1 The method comprises the following steps:
u 1 ＝u 5 +i Rs1 ·R s1 (16)
the over-voltage back calculation process is to obtain time sequence waveform data of the over-voltage of the primary side by back calculation from the secondary side to the primary side sequentially according to kirchhoff voltage and current law and the voltage and current relation of each element under the condition that the over-voltage waveform of the secondary side is known.
The technical effect of the invention is that the representation accuracy of the gradual change saturation characteristic of the electromagnetic voltage transformer iron core has larger influence on the error of voltage back calculation, and the gradual change saturation region of the accurate representation excitation curve is the premise of realizing accurate back calculation. The electrical connection mode of the existing primary side equipment is not changed, no nonstandard primary equipment is introduced, and only a secondary side acquisition device and a storage device are needed to be added on the basis of the existing voltage transformer, so that the cost is low; the method can accurately measure low-frequency or high-amplitude transient overvoltage caused by core nonlinearity in the power system, and can reflect the time sequence evolution process of real overvoltage accidents.
The algorithm provided by the invention restores the real waveform of the primary side, greatly reduces the maximum error, can not add any nonstandard primary equipment, and greatly improves the accurate measurement and perception capability of PT (potential transformer) on low-frequency transient voltage.
Drawings
FIG. 1 is a block diagram of an electromagnetic voltage transformer;
FIG. 2 is an electromagnetic dual schematic diagram I;
FIG. 3 is an electromagnetic dual schematic diagram II;
fig. 4 is a schematic diagram of an electromagnetic voltage transformer circuit taking into account the core;
FIG. 5 is a low frequency or high amplitude transient overvoltage back calculation model of an electromagnetic voltage transformer;
FIG. 6 shows hysteresis loops and basic magnetization curves obtained by an open circuit test at different voltages;
FIG. 7 is a schematic diagram of an electromagnetic voltage transformer deep saturation test platform;
FIG. 8 is a fitted curve of two excitation branches of an electromagnetic voltage transformer pi model;
FIG. 9 is a measured and back-calculated waveform of a high-amplitude high-frequency resonant voltage of the voltage transformer;
FIG. 10 is a measured and back-calculated waveform of a high-amplitude transient voltage of a voltage transformer;
FIG. 11 is a comparison of the back calculation voltage spectrum of the voltage transformer;
Detailed Description
The present invention is further described below with reference to examples, but it should not be construed that the scope of the above subject matter of the present invention is limited to the following examples. Various substitutions and alterations are made according to the ordinary skill and familiar means of the art without departing from the technical spirit of the invention, and all such substitutions and alterations are intended to be included in the scope of the invention.
Example 1:
referring to fig. 1 to 5, the low-frequency or high-amplitude transient overvoltage back calculation method based on the electromagnetic voltage transformer mainly comprises the following steps:
1) Referring to fig. 2 to 4, a voltage transformer electromagnetic dual pi model considering a geometric physical structure is established based on a transformer electromagnetic dual model and a winding and iron core electromagnetic coupling mechanism. In FIG. 2, F 1 、F 2 For the excitation power supply, 1,2 denote excitation branch I and excitation branch II, respectively. In FIG. 3, i 1 、i 2 Respectively as deep saturation inductances L m1 And deep saturation inductance L m2 Is provided. The primary winding of the voltage transformer is equivalent to an ideal transformer I, and the secondary winding is equivalent to an ideal transformer II. The electromagnetic dual pi model of the voltage transformer is provided with two excitation branches which are respectively marked as an excitation branch I and an excitation branch II. Aiming at the back calculation research of low-frequency or high-amplitude transient voltage of the electromagnetic voltage transformer, the influence of stray capacitance can be ignored in modeling.
2) Open-circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that the exciting resistance R of two exciting branches of the electromagnetic dual pi model is determined m1 Exciting resistor R m2 And respectively establishing single-value magnetization curves when the two excitation branches are not saturated.
3) Short-circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that leakage inductance L of the electromagnetic dual pi model is determined s And winding resistance R s Is a numerical value of (2). Measuring the DC resistance of the winding, and setting the winding resistance R according to the DC resistance s The winding resistance distributed to two sides of the electromagnetic dual pi model of the voltage transformer is set as R s1 The winding resistance of the secondary side is R s2 。
4) The method comprises the steps of using an alternating current/direct current hybrid power supply as an excitation source, testing excitation inductances of a voltage transformer iron core under different saturation degrees, and respectively obtaining deep saturation inductances L of two excitation branches according to an allocation principle m1_s And deep saturation inductance L m2_s . And converting the deep saturation inductances of the two excitation branches into data points of deep saturation sections of the excitation curves, and establishing the excitation curves of the two excitation branches when the two excitation branches are deeply saturated. The AC/DC hybrid power supply comprises a function generator and a power amplifier. The function generator generates excitation pulse and sends the excitation pulse to the power amplifier after amplifying the excitation pulseA voltage transformer. When the voltage transformer works in a non-saturation region, the method for distributing the port excitation inductance comprises the following steps: the magnetic flux and the excitation resistance are equally distributed to the two excitation branches.
Wherein, the magnetic flux, current and resistance of the two excitation curves respectively satisfy the following formula:
ψ 1 ＝ψ 2 ＝ψ (1)
R m1 ＝R m2 ＝2R m (3)
where ψ represents magnetic flux. i represents current, R m Representing the resistance. The subscript 1 indicates the excitation branch I. The subscript 2 indicates the excitation branch II.
When the voltage transformer works in a saturation region, the deep saturation inductance L of the two excitation curves m1_s And deep saturation inductance L m2_s The allocation is as follows:
where n is the secondary side discrete voltage data sequence number, n=1, 2,3, … …. Psi phi type s1 (n)、ψ s2 (n) represents the nth discrete magnetic flux data of the two excitation curves, respectively. i.e s1 (n)、i s2 (n) represents the nth discrete current data of the two excitation curves, respectively.
The currents of the two excitation curves respectively meet the following formula:
i s1 (n)+i s2 (n)＝i s (n) (7)
wherein i is s (n) is the nth discrete total current data of the two excitation curves.
5) And combining a single-value magnetization curve when the two excitation branches are not saturated and an excitation curve when the two excitation branches are deeply saturated, so that the saturation characteristic of the iron core of the voltage transformer is represented.
6) And deducing the volt-ampere characteristics of the electromagnetic element in the dual pi model based on the kirchhoff voltage, the current law and the PT electromagnetic to obtain a discrete inversion algorithm based on a back calculation circuit model, monitoring the secondary side voltage data of the voltage transformer in real time, and performing inversion calculation to obtain the time sequence waveform data of the primary side overvoltage. .
The main steps of back-calculating the time sequence waveform data of the primary side overvoltage are as follows:
6.1 According to the transformation characteristic and the isolation characteristic of the voltage transformer, the number of turns of the primary side coil and the number of turns of the secondary side coil of the voltage transformer are set to satisfy the following formula:
wherein N is 1 : n represents the transformation characteristic of the voltage transformer, N is the transformation ratio of the electromagnetic voltage transformer, and the value of N depends on the turn ratio of the primary side winding and the secondary side winding. N: n (N) 2 And the isolation characteristic of the electromagnetic voltage transformer is represented.
6.2 When low-frequency or high-amplitude transient overvoltage acts on PT, the voltage transformer works in a saturated or deep saturated state, and current i flowing through the exciting inductance at the moment Lm1 And i Lm2 The magnetic flux shows nonlinear characteristics with the excitation inductance, namely, the following nonlinear function is satisfied:
i Lm1 ＝f Lm1 (ψ 1 )。i Lm2 ＝f Lm2 (ψ 2 ) (9)
wherein f Lm1 (ψ 1 )、f Lm2 (ψ 2 ) Respectively represent the magnetic flux psi with respect to the excitation branch I 1 And magnetic flux ψ about the excitation branch II 2 Is a non-linear function of (2).
Wherein, excitation inductance L m2 The interlinkage magnetic flux ψ of (2) satisfies the following equation:
wherein u is 3 Exciting inductance L for secondary side exciting branch of voltage transformer m2 A voltage across the terminals. Δt is the nth discrete voltage data u 3 (n) and n-1 th discrete voltage data u 3 (n-1) time difference between the two.
6.3 Calculating the secondary side excitation branch voltage u 3 The method comprises the following steps:
6.4 From leakage inductance L s The leakage inductance voltage is calculated according to the volt-ampere characteristic of the transformer, and the main steps are as follows:
6.4.1 Establishment of leakage inductance voltage u) Ls Is a continuous integral function of (1), namely:
wherein i is Rm1 For flowing through exciting resistor R m1 Is set in the above-described range).
6.4.2 -converting the continuous integral function (12) into a differential algebraic equation, namely:
wherein i is Ls (n) is the leakage inductance L s Is the nth discrete current data of (a).
6.4.3 Solving the formula (13) to obtain leakage inductance voltage u Ls 。
6.5 Calculating primary side excitation branch voltage u 5 The method comprises the following steps:
6.6 Calculating primary side current i of voltage transformer Rs1 The method comprises the following steps:
6.8 Calculating the primary-side port voltage u) 1 The method comprises the following steps:
u 1 ＝u 5 +i Rs1 ·R s1 (16)
example 2:
referring to fig. 6 to 11, experiments of the transient overvoltage back calculation method based on the electromagnetic voltage transformer are mainly as follows:
1) Modeling: the model is built by taking a 10kV single-phase electromagnetic voltage transformer as a research object, the model is JDZ10 (G) -10B3, the capacity is 15VA, and the iron core material is 10JNEX900 non-oriented silicon steel.
2) Open circuit test: to obtain a single-valued hysteresis-free magnetization curve of the core, a plurality of sets of open circuit tests were performed, and the voltage applied to the secondary side of PT (voltage transformer) was gradually increased from 0.1 pu. Since the PT rated operating point is low and the rated capacity is 15VA, the maximum voltage of the open circuit test is applied to 1.4pu in combination with laboratory conditions, the test data are shown in table 1, the corresponding hysteresis loop and single-value magnetization curve are shown in fig. 4, and the exciting resistance of the voltage transformer is 1237.7 ohms. Analysis shows that when the voltage u=141.4v, the peak current is 0.822A, which is 5 to 6 times the rated current (0.15A) on the PT secondary side, and the core saturation degree is high.
Table 1 single value magnetization curve data of electromagnetic voltage transformer
3) Short circuit test: the secondary side (1 a-1b end) of the voltage transformer is short-circuited, and voltage is applied to the primary side. Gradually increasing the voltage to bring the current to the nominal value (0.15A), measuring and recording the electricityVoltage and current. The calculated winding resistance and leakage inductance parameters: obtaining leakage inductance L s =1.96 mH, winding resistance R s = 0.6756 Ω, the test transformer primary and secondary windings direct current resistor R dc1 ＝2.2677kΩ，R dc2 = 0.3945 Ω, and the calculated electromagnetic dual pi model first and second side winding resistances are respectively: r's' s1 ＝0.25Ω，R s2 ＝0.43Ω。
4) Deep saturation test: the voltage transformer deep saturation inductance test platform is built, as shown in fig. 5, the function generator generates direct current voltage with alternating current coupling signals, and the power amplifier is used for providing enough power supply capacity. After the deep saturation inductances of the two excitation branches of the electromagnetic dual pi model of the voltage transformer are measured, the deep saturation inductances are converted into data on a deep saturation excitation curve, and the results are shown in table 2. By combining the excitation curves obtained by the above-described open circuit test, two excitation curves considering deep saturation are obtained, as shown in fig. 8.
Table 2 data allocation results at different saturation states
5) According to the data, an inverse calculation program of the transient overvoltage based on the electromagnetic voltage transformer is written in Matlab, and inverse calculation verification of the frequency division ferromagnetic resonance overvoltage is performed. The frequency division ferromagnetic resonance test platform of the electromagnetic voltage transformer is built, frequency division ferromagnetic resonance overvoltage is generated on the primary side of the transformer, the response waveform is measured on the secondary side of the transformer, and the voltage waveform of the secondary side of the voltage transformer is reversely calculated to the primary side according to the transient overvoltage reverse calculation method proposed by the embodiment 1, and the result is shown in fig. 9 and 10. As can be seen from the back-calculation waveform comparison chart, the distorted portion of the PT secondary side voltage is restored to a higher degree.
The back calculation result relative error can be expressed as:
wherein: u's' 1 And (3) performing back calculation on the primary side obtained by back calculation according to the method. U (U) 1 Is the primary side true voltage value, V. E (E) r Is the relative error of the back-calculated voltage with respect to the true voltage.N is the PT port collected data quantity for the overall error of the back calculation waveform. n=0, 1,2, … … N.
TABLE 3 comparison of back-calculated voltage and reduced voltage errors
And carrying out Fourier decomposition on the back-calculated voltage, the primary real voltage and the secondary reduced voltage in the power frequency overvoltage test of the electromagnetic voltage transformer, wherein the main harmonic components of the discrete voltage data are shown in figure 11.
As can be obtained from the error analysis in table 3 and the spectrum analysis in fig. 10, the overall back calculation error of the back calculation voltage calculated by the electromagnetic voltage transformer based back calculation algorithm provided herein is only 4.6%, and the maximum error is reduced from the original 65.64% to 9%, so that the perception level of the transient voltage of the voltage transformer is obviously improved. In addition, according to spectrum analysis, more higher harmonics exist in the calculated voltage, the back-calculation voltage is basically consistent with harmonic components of the real voltage, and the back-calculation voltage is proved to be capable of accurately obtaining primary-side real voltage data.
Claims (4)
1. The transient overvoltage back calculation method based on the electromagnetic voltage transformer is characterized by comprising the following steps of:
1) Establishing a voltage transformer electromagnetic dual pi model considering a geometric physical structure based on a voltage transformer electromagnetic dual model and a winding and iron core electromagnetic coupling mechanism; the primary winding of the voltage transformer is equivalent to an ideal transformer I, and the secondary winding is equivalent to an ideal transformer II; the electromagnetic dual pi model of the voltage transformer is provided with two excitation branches which are respectively marked as an excitation branch I and an excitation branch II;
2) Open circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that the exciting resistance R of two exciting branches of the electromagnetic dual pi model is determined m1 、R m2 Respectively establishing single-value magnetization curves of the two excitation branches when the two excitation branches are not saturated based on a trapezoidal integration method;
3) Short-circuit test is carried out on the electromagnetic dual pi model of the voltage transformer, so that leakage inductance L of the electromagnetic dual pi model is determined s And winding resistance R s Is a numerical value of (2); measuring the DC resistance of the winding, and setting the winding resistance R according to the DC resistance s The winding resistance distributed to two sides of the electromagnetic dual pi model of the voltage transformer is set as R s1 The winding resistance of the secondary side is R s2 ；
4) Exciting and testing excitation inductances of the voltage transformer iron cores under different saturation degrees by taking an alternating current/direct current hybrid power supply as an excitation source; distributing the port excitation inductance according to the parameters of the two excitation branches of the pi model of the voltage transformer and the pi model circuit structure of the voltage transformer to obtain the deep saturation inductance L of the two excitation branches m1 And deep saturation inductance L m2 The method comprises the steps of carrying out a first treatment on the surface of the Converting the deep saturation inductances of the two excitation branches into data points of the deep saturation section of the excitation curve, and establishing an excitation curve when the two excitation branches are deeply saturated;
5) Combining a single-value magnetization curve when the two excitation branches are not saturated and an excitation curve when the two excitation branches are deeply saturated, so that the saturation characteristic of the iron core of the voltage transformer is represented;
6) Deriving the volt-ampere characteristics of an electromagnetic element in a dual pi model based on kirchhoff voltage and current law and PT electromagnetic to obtain a discrete inversion algorithm based on a back calculation circuit model, monitoring the secondary side voltage data of a voltage transformer in real time, and performing inversion calculation to obtain time sequence waveform data of primary side overvoltage;
the step of back-calculating the time-series waveform data of the primary-side overvoltage is as follows:
1) According to the transformation characteristic and isolation characteristic of the voltage transformer, the number of turns of the primary side coil and the number of turns of the secondary side coil of the voltage transformer are set to satisfy the following formula:
wherein N is 1 : n represents the transformation characteristic of the electromagnetic voltage transformer, k is the transformation ratio of the voltage transformer, and the value of the transformation ratio depends on the turn ratio of the primary side winding to the secondary side winding; n: n (N) 2 Characterizing the isolation characteristic of the electromagnetic voltage transformer;
2) When low-frequency or high-amplitude transient overvoltage acts on PT, the voltage transformer works in a saturated or deep saturated state, and at the moment, current i flowing through the exciting inductance Lm1 And i Lm2 The magnetic flux shows nonlinear characteristics with the excitation inductance, namely, the following nonlinear function is satisfied:
i Lm1 ＝f Lm1 (ψ 1 )；i Lm2 ＝f Lm2 (ψ 2 ) (2)
wherein f Lm1 (ψ 1 )、f Lm2 (ψ 2 ) Respectively represent the magnetic flux psi with respect to the excitation branch I 1 And magnetic flux ψ about the excitation branch II 2 Is a nonlinear function of (2);
wherein, excitation inductance L m2 Is set to have the interlinkage magnetic flux psi 2 (n) satisfies the following formula:
wherein u is 3 Exciting inductance L for secondary side exciting branch of voltage transformer m2 A voltage across the two terminals; Δt is the nth discrete voltage data u 3 (n) and n-1 th discrete voltage data u 3 (n-1) a time difference between;
3) Calculating the secondary side excitation branch voltage u 3 The method comprises the following steps:
wherein u is 2 The secondary side voltage of the voltage transformer;
4) From leakage inductance L s The leakage inductance voltage is calculated according to the volt-ampere characteristic of the transformer, and the steps are as follows:
4.1 Establishment of leakage inductance voltage u) Ls Is a continuous integral function of (1), namely:
wherein i is Rm1 For flowing through exciting resistor R m1 Is set to be a current of (a);
4.2 -converting the continuous integral function (5) into a differential algebraic equation, namely:
wherein i is Ls (n) is the leakage inductance L s Is the nth discrete current data of (a);
4.3 Solving the formula (6) to obtain leakage inductance voltage u Ls ；
5) Calculating primary side excitation branch voltage u 5 The method comprises the following steps:
6) Calculating primary side current i of voltage transformer Rs1 The method comprises the following steps:
7) Calculating the primary-side port voltage u 1 The method comprises the following steps:
u 1 ＝u 5 +i Rs1 ·R s1 (9)。
2. the method for back calculation of transient overvoltage based on electromagnetic voltage transformer according to claim 1, wherein when the voltage transformer works in a non-saturation region, two excitation inductances of pi model are far larger than leakage inductance, and the method for distributing port excitation inductances is as follows: the magnetic flux and the exciting resistor are evenly distributed to two exciting branches;
wherein, the magnetic flux, current and resistance of the two excitation curves respectively satisfy the following formula:
ψ 1 ＝ψ 2 ＝ψ (10)
R m1 ＝R m2 ＝2R m (12)
wherein ψ represents magnetic flux; i represents current, R m Representing the resistance; subscript 1 denotes an excitation branch I; the subscript 2 indicates the excitation branch II.
3. The method for back calculation of transient overvoltage based on electromagnetic voltage transformer according to claim 1, wherein when the voltage transformer works in saturation region, the depth saturation inductance L of two excitation curves m1_s And deep saturation inductance L m2_s The allocation is as follows:
in the psi- s1 (n)、ψ s2 (n) each represents two excitation curvesLine nth discrete magnetic flux data; i.e s1 (n)、i s2 (n) n represents the nth discrete current data of the two excitation curves, respectively;
the currents of the two excitation curves respectively satisfy the following formulas:
i s1 (n)+i s2 (n)＝i s (n) (16)
wherein n is a secondary side discrete data sequence number, n=1, 2,3, … …; i.e s (n) is the nth discrete total current data of the two excitation curves.
4. The electromagnetic voltage transformer-based transient overvoltage back calculation method according to claim 1, wherein: the transient overvoltage back calculation method based on the electromagnetic voltage transformer is used for restoring the real waveform of the primary side.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010649855.2A CN111879996B (en) | 2020-07-08 | 2020-07-08 | Transient overvoltage back calculation method based on electromagnetic voltage transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010649855.2A CN111879996B (en) | 2020-07-08 | 2020-07-08 | Transient overvoltage back calculation method based on electromagnetic voltage transformer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111879996A CN111879996A (en) | 2020-11-03 |
| CN111879996B true CN111879996B (en) | 2023-12-05 |
Family
ID=73150358
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010649855.2A Active CN111879996B (en) | 2020-07-08 | 2020-07-08 | Transient overvoltage back calculation method based on electromagnetic voltage transformer |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111879996B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112668168A (en) * | 2020-12-21 | 2021-04-16 | 广东电网有限责任公司电力科学研究院 | CVT power frequency simulation model and simulation method under super-excitation working condition of intermediate transformer |
| CN112583013A (en) * | 2020-12-30 | 2021-03-30 | 广东电网有限责任公司电力科学研究院 | Capacitor bank operation harmonic environment monitoring method, device and equipment |
| CN113536596A (en) * | 2021-08-11 | 2021-10-22 | 国网宁夏电力有限公司电力科学研究院 | Direct-current control protection inversion method and system based on circuit simulation model |
| CN114204612A (en) * | 2021-12-15 | 2022-03-18 | 华北电力大学 | Power interaction algorithm for universal electromagnetic transient black box model and external control |
| CN114325057B (en) * | 2021-12-31 | 2023-09-19 | 重庆大学 | PT primary voltage reconstruction method based on inverse black box and inverse electromagnetic dual model |
| CN114996972B (en) * | 2022-07-12 | 2024-02-13 | 沈阳工程学院 | Modeling method of three-phase eight-column type magnetically controlled shunt reactor |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101388648A (en) * | 2007-09-14 | 2009-03-18 | 财团法人工业技术研究院 | Multi-frequency multi-mode power amplifier and operating method thereof |
| CN102570428A (en) * | 2012-02-29 | 2012-07-11 | 山东电力集团公司莱芜供电公司 | Fault location and distance protection method based on differential output of electronic mutual inductor |
| CN103559347A (en) * | 2013-10-31 | 2014-02-05 | 浙江大学 | Method for establishing electromagnetic transient simulation model of large-scale AC-DC (Alternating Current - Direct Current) power system |
| WO2014121438A1 (en) * | 2013-02-05 | 2014-08-14 | Alstom Technology Ltd. | Method and apparatus for current differential protection for uhvdc transmission line |
| CN106681959A (en) * | 2016-11-17 | 2017-05-17 | 云南电网有限责任公司电力科学研究院 | Method for calculating voltage fluctuation in power distribution network |
| CN107958125A (en) * | 2017-12-12 | 2018-04-24 | 中国电力科学研究院有限公司 | Low frequency model modeling method and system in a kind of three-phase transformer electro-magnetic transient |
| CN108256196A (en) * | 2018-01-10 | 2018-07-06 | 重庆大学 | A kind of single-phase two-winding transformer for considering iron core depth saturated characteristic improves π model acquisition methods |
| CN108957369A (en) * | 2018-03-30 | 2018-12-07 | 广东电网有限责任公司电力科学研究院 | A kind of single-phase two-winding transformer excitation curve distribution method and device |
| CN110231582A (en) * | 2019-06-18 | 2019-09-13 | 贵州电网有限责任公司 | A method of measurement and calculating transformer π model are saturated excitation curve |
-
2020
- 2020-07-08 CN CN202010649855.2A patent/CN111879996B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101388648A (en) * | 2007-09-14 | 2009-03-18 | 财团法人工业技术研究院 | Multi-frequency multi-mode power amplifier and operating method thereof |
| CN102570428A (en) * | 2012-02-29 | 2012-07-11 | 山东电力集团公司莱芜供电公司 | Fault location and distance protection method based on differential output of electronic mutual inductor |
| WO2014121438A1 (en) * | 2013-02-05 | 2014-08-14 | Alstom Technology Ltd. | Method and apparatus for current differential protection for uhvdc transmission line |
| CN103559347A (en) * | 2013-10-31 | 2014-02-05 | 浙江大学 | Method for establishing electromagnetic transient simulation model of large-scale AC-DC (Alternating Current - Direct Current) power system |
| CN106681959A (en) * | 2016-11-17 | 2017-05-17 | 云南电网有限责任公司电力科学研究院 | Method for calculating voltage fluctuation in power distribution network |
| CN107958125A (en) * | 2017-12-12 | 2018-04-24 | 中国电力科学研究院有限公司 | Low frequency model modeling method and system in a kind of three-phase transformer electro-magnetic transient |
| CN108256196A (en) * | 2018-01-10 | 2018-07-06 | 重庆大学 | A kind of single-phase two-winding transformer for considering iron core depth saturated characteristic improves π model acquisition methods |
| CN108957369A (en) * | 2018-03-30 | 2018-12-07 | 广东电网有限责任公司电力科学研究院 | A kind of single-phase two-winding transformer excitation curve distribution method and device |
| CN110231582A (en) * | 2019-06-18 | 2019-09-13 | 贵州电网有限责任公司 | A method of measurement and calculating transformer π model are saturated excitation curve |
Non-Patent Citations (3)
| Title |
|---|
| 片上变压器的建模和参数提取方法的研究;陈媛;《中国优秀硕士学位论文全文数据库工程科技Ⅱ辑》(第2期);第C042-437页 * |
| 考虑铁心深度饱和的单相双绕组变压器改进π模型;司马文霞 等;《中国电机工程学报》;第38卷(第24期);第7131-7140页 * |
| 计及磁滞效应的变压器低频电磁暂态模型及其在铁磁谐振中的应用;邹密;《中国博士学位论文全文数据库工程科技Ⅱ辑》(第4期);第C042-44页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111879996A (en) | 2020-11-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111879996B (en) | Transient overvoltage back calculation method based on electromagnetic voltage transformer | |
| Ala et al. | Design and performance evaluation of a high power-density EMI filter for PWM inverter-fed induction-motor drives | |
| CN108957183B (en) | Method and device for monitoring direct current magnetic bias of transformer | |
| Filipović-Grčić et al. | High-frequency model of the power transformer based on frequency-response measurements | |
| CN102592062B (en) | Method for calculating DC (direct current) magnetic bias dynamic leakage inductance of transformer | |
| CN111460605B (en) | Transformer broadband hybrid model considering core nonlinearity and building method thereof | |
| CN105510742A (en) | Experiment method and analysis calculation method for testing transformer volt-ampere characteristic by using low-frequency power supply | |
| Unsar et al. | Identification of harmonic current contributions of iron and steel plants based on time-synchronized field measurements—Part I: At PCC | |
| CN107390156A (en) | A kind of electric power mutual-inductor state monitoring method and device based on fundamental wave zero sequence feature | |
| Schöttke et al. | Transfer characteristic of a MV/LV transformer in the frequency range between 2 kHz and 150 kHz | |
| Amaripadath et al. | Power quality disturbances on smart grids: Overview and grid measurement configurations | |
| Denboer et al. | Frequency scan based screening technique for harmonic interactions of HVDC systems | |
| Xie et al. | Network impedance measurements for three-phase high-voltage power systems | |
| Lin et al. | A new model for transformer saturation characteristics by including hysteresis loops | |
| Zhou et al. | A model considering deep saturation of the iron core for 10 kV potential transformers | |
| CN104614688A (en) | C-type sensor for DC magnetic bias dynamic magnetic-flux measurement and detection method thereof | |
| Elhaffar et al. | High frequency current transformer modeling for traveling waves detection | |
| CN104166048A (en) | Power frequency interference resistant insulation resistor testing apparatus and testing method based on resonance network | |
| Miličević et al. | Modeling of nonlinear coil in a ferroresonant circuit | |
| CN207601204U (en) | A kind of typical structure transformer DC magnetic bias research project experimental rig | |
| Sima et al. | Reconstructing primary voltages across inductive VTs—Part I: Methodology | |
| Wu et al. | Analysis of the Influence of DC Magnetic Bias Induced by Rail Transit Stray Current on Harmonic Characteristics of Transformer Neutral Current | |
| CN110244146A (en) | Transformer core pulsactor measurement method based on distributed AC and DC electricity | |
| Wang et al. | Residual Flux Density Measurement Method of the Single-Phase Transformer Based on Phase Difference | |
| CN204065241U (en) | Based on the test device for insulation resistance of the anti-Hz noise of resonant network |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |