CN110146780B - Ferromagnetic resonance distinguishing method for neutral point ungrounded flexible power distribution network system - Google Patents

Ferromagnetic resonance distinguishing method for neutral point ungrounded flexible power distribution network system Download PDF

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CN110146780B
CN110146780B CN201910336859.2A CN201910336859A CN110146780B CN 110146780 B CN110146780 B CN 110146780B CN 201910336859 A CN201910336859 A CN 201910336859A CN 110146780 B CN110146780 B CN 110146780B
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CN110146780A (en
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吴楠
史明明
袁宇波
周建华
陈久林
黄成�
孙健
杨雄
焦昊
祁承磊
周涛
张刘冬
曾飞
方鑫
陈雯嘉
袁晓冬
陈兵
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State Grid Corp of China SGCC
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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State Grid Corp of China SGCC
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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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
    • 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
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Abstract

The invention discloses a ferromagnetic resonance distinguishing method for a neutral point ungrounded flexible power distribution network system, which is used for detecting phasor values of zero-sequence voltage and three-phase voltage of a bus after normal operation and fault and the frequency f of the bus voltage0After the fundamental frequency resonance, the frequency multiplication resonance and the fundamental frequency resonance are judged, the relative amplitude error of the j-phase voltage is calculated
Figure DDA0002038270570000011
Phase voltage relative phase error
Figure DDA0002038270570000012
If 0 < epsilonampiXi and 0 < epsilonphiAnd if yes, ferromagnetic resonance is judged to occur, otherwise, non-ferromagnetic resonance is judged. The method can be used for judging the ferromagnetic resonance of the neutral point ungrounded system, and the high accuracy of judging the ferromagnetic resonance fault is ensured.

Description

Ferromagnetic resonance distinguishing method for neutral point ungrounded flexible power distribution network system
Technical Field
The invention relates to a ferromagnetic resonance distinguishing method for a neutral point ungrounded flexible power distribution network system, and belongs to the technical field of power distribution automation of power systems.
Background
At present, ferromagnetic resonance overvoltage is a common form of internal overvoltage, and is due to nonlinear resonance formed by iron cores of a voltage transformer (PT) and a power grid ground capacitor after the PT is saturated. The current flexible power electronic technology becomes an important trend for transforming a power distribution network, and the power factor of the power distribution network is increased and the loss of the power network is reduced by changing the line capacitance to ground based on a flexible power distribution network system transformed by technologies such as Thyristor Switched Capacitor (TSC) and the like. The flexible power distribution network system changes the line parameters of the traditional power distribution network, ferromagnetic resonance occurs usually when single-phase earth fault is recovered or electrical equipment is suddenly switched, at the moment, phase voltage can be increased to 3-5 times of a rated value, the insulation weak point of a power grid is easy to break down, and the fuse wire is easy to fuse or even PT is easy to crack due to large current of PT, so that the safe and stable operation of the power grid is influenced. Therefore, the ferromagnetic resonance fault of the flexible power distribution network system is very important to be rapidly judged.
Ferromagnetic resonance can be divided into frequency division resonance, fundamental frequency resonance, and frequency multiplication resonance. The frequency division resonance and the fundamental frequency resonance are common in practice. And when in frequency multiplication resonance and frequency division resonance, the zero sequence voltage presents the characteristics of frequency multiplication and frequency division and is easy to identify. And when the fundamental frequency resonates, the zero sequence voltage is the power frequency, and when the fundamental frequency resonates, one-phase or multi-phase voltage is reduced, the characteristics of the fundamental frequency resonant voltage are similar to those of a single-phase grounding fault, and the fundamental frequency resonant voltage and the single-phase grounding fault are difficult to directly distinguish. Therefore, how to distinguish the ferroresonance from the single-phase earth fault becomes a problem to be solved in the field of power grid fault judgment.
Disclosure of Invention
The purpose is as follows: in order to overcome the defects in the prior art, the invention provides a ferromagnetic resonance judging method for a non-grounded neutral point flexible power distribution network system, and accuracy of ferromagnetic resonance fault judgment is ensured.
The technical scheme is as follows: in order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a ferromagnetic resonance distinguishing method for a neutral point ungrounded flexible power distribution network system comprises the following steps,
step 1, detecting zero sequence voltage of fault bus
Figure BDA0002038270550000021
U0Is composed of
Figure BDA0002038270550000022
Effective value of, identify
Figure BDA0002038270550000023
Has a frequency of f0If f is0<Judging that frequency division resonance occurs at 50Hz, if f0>Judging that frequency multiplication resonance occurs at 50 Hz;
step 2, if f050Hz and the effective value U of the zero sequence voltage of the bus after the fault0If the phase voltage exceeds the effective value, the fundamental frequency resonance is judged to occur, or if f is0If the three-phase voltage effective value is increased simultaneously after the fault, judging that fundamental frequency resonance occurs;
step 3, if the situation is not judged in the step 1 or the step 2, detecting the three-phase steady-state voltage magnitude value in normal operation before the fault
Figure BDA0002038270550000024
EA、EB、ECAre respectively as
Figure BDA0002038270550000025
Figure BDA0002038270550000026
Voltage amplitude of (d);
step 4, detecting phasor values of three-phase steady-state voltage and bus zero-sequence voltage after fault
Figure BDA0002038270550000027
Figure BDA0002038270550000028
UA、UB、UC、U0Are respectively as
Figure BDA0002038270550000029
Voltage amplitude of (d); calculating the initial phase reference value ph of a certain phase as a reference phase1iAnd bus starting phase reference value ph2iWherein i is A, B or C, and the formula is as follows:
Figure BDA00020382705500000210
Figure BDA00020382705500000211
wherein i is A or B or C, EiIs i phase voltage amplitude, U 'in normal operation'iReference phase fault voltage amplitude and U 'are taken'0Taking the voltage amplitude of the zero sequence voltage of the bus in fault;
step 5, enabling the voltage amplitude U to be in fault with the reference phaseiAnd a reference phase starting phase reference value ph1iCombined into reference phase voltage phasor reference calculation value
Figure BDA0002038270550000031
The voltage amplitude U of the zero sequence voltage of the bus in fault0And the bus initial phase reference value ph2iCombined bus zero sequence voltage phasor reference calculation value
Figure BDA0002038270550000032
The formula is as follows:
Figure BDA0002038270550000033
Figure BDA0002038270550000034
step (ii) of6. Calculating j-phase phasor calculated values except for reference phase
Figure BDA0002038270550000035
j is A, B or C, and the formula is as follows:
Figure BDA0002038270550000036
wherein the content of the first and second substances,
Figure BDA0002038270550000037
a j-phase steady state voltage magnitude value for normal operation;
step 7, calculating the relative amplitude error epsilon of the j phase voltageampjRelative phase error epsilon of phase voltagephjThe formula is as follows:
Figure BDA0002038270550000038
wherein, i is equal to j,
Figure BDA0002038270550000039
the voltage amplitude of the i-phase three-phase steady-state voltage after the fault;
Figure BDA00020382705500000310
wherein the content of the first and second substances,
Figure BDA00020382705500000311
calculating values for j-phase phasors
Figure BDA00020382705500000312
The phase angle of (a) is determined,
Figure BDA00020382705500000313
reference calculation value for reference phase voltage phasor
Figure BDA00020382705500000314
The phase angle of (a) is determined,
Figure BDA00020382705500000315
the phase angle of the j-phase steady-state voltage magnitude after the fault,
Figure BDA00020382705500000316
a phase angle that is a post-fault reference phase steady-state voltage magnitude value;
step 8, if 0 is more than epsilonampiXi and 0 < epsilonphiAnd if yes, ferromagnetic resonance is judged to occur, otherwise, non-ferromagnetic resonance is judged.
As a preferred solution, if the zero sequence voltage transformer is not provided,
Figure BDA00020382705500000317
by calculation of formula
Figure BDA00020382705500000318
And calculating to obtain the result, wherein,
Figure BDA00020382705500000319
are phase voltage measurements of A, B, C three phases after a fault, respectively, an
Figure BDA0002038270550000041
Are measured values at the same reference phase.
As a preferred scheme, the bus zero sequence voltage is the voltage at the bus of the flexible power distribution network system.
As a preferable scheme, the ξ is less than or equal to 20 percent
Preferably, ξ is 20%.
Preferably, ξ is 10%.
Has the advantages that: the ferromagnetic resonance judging method for the non-grounded neutral point flexible power distribution network system provided by the invention is used for judging the ferromagnetic resonance of the non-grounded neutral point system, so that the high accuracy of judging the ferromagnetic resonance fault is ensured.
Drawings
FIG. 1 is a schematic flow chart of a determination method according to the present invention;
FIG. 2 is a waveform diagram of wave recording at a bus of a section II of a flexible power distribution network system;
fig. 3 is a phasor diagram with the a-phase phasor as the starting phase.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, in which it is understood that the embodiments described are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
A ferromagnetic resonance distinguishing method for a neutral point ungrounded flexible power distribution network system comprises the following steps:
step 1, detecting zero sequence voltage of fault bus
Figure BDA0002038270550000042
U0Is composed of
Figure BDA0002038270550000043
Effective value of, identify
Figure BDA0002038270550000051
Has a frequency of f0If f is0<Judging that frequency division resonance occurs at 50Hz, if f0>And judging that frequency multiplication resonance occurs at 50 Hz.
If under the condition of having the zero sequence voltage transformer,
Figure BDA0002038270550000052
the signal can be directly acquired by a zero sequence voltage transformer;
if the zero sequence voltage transformer is not available,
Figure BDA0002038270550000053
can be calculated by
Figure BDA0002038270550000054
The calculation results in that,wherein the content of the first and second substances,
Figure BDA0002038270550000055
are phase voltage measurements of A, B, C three phases after a fault, respectively, an
Figure BDA0002038270550000056
Are measured values at the same reference phase.
The voltage involved throughout is the voltage at the bus of the overall flexible power distribution system.
Step 2, if f050Hz and the effective value U of the zero sequence voltage of the bus after the fault0If the phase voltage exceeds the effective value, the fundamental frequency resonance is judged to occur, or if f is0If the three-phase voltage effective value is increased simultaneously after the fault, judging that fundamental frequency resonance occurs;
step 3, if the situation is not judged in the step 1 or the step 2, detecting the three-phase steady-state voltage magnitude value in normal operation before the fault
Figure BDA0002038270550000057
EA、EB、ECAre respectively as
Figure BDA0002038270550000058
Figure BDA0002038270550000059
Voltage amplitude of (d);
step 4, detecting phasor values of three-phase steady-state voltage and bus zero-sequence voltage after fault
Figure BDA00020382705500000510
Figure BDA00020382705500000511
UA、UB、UC、U0Are respectively as
Figure BDA00020382705500000512
Voltage amplitude of (d); calculating the initial phase reference value ph of a certain phase as a reference phase1iAnd bus starting phase reference value ph2iWherein i is A, B or C, and the formula is as follows:
Figure BDA00020382705500000513
Figure BDA00020382705500000514
wherein i is A or B or C, EiIs i phase voltage amplitude, U 'in normal operation'iReference phase fault voltage amplitude and U 'are taken'0And (4) taking the voltage amplitude of the zero sequence voltage of the bus in fault.
Step 5, enabling the voltage amplitude U to be in fault with the reference phaseiAnd a reference phase starting phase reference value ph1iCombined into reference phase voltage phasor reference calculation value
Figure BDA0002038270550000061
The voltage amplitude U of the zero sequence voltage of the bus in fault0And the bus initial phase reference value ph2iCombined bus zero sequence voltage phasor reference calculation value
Figure BDA0002038270550000062
The formula is as follows:
Figure BDA0002038270550000063
Figure BDA0002038270550000064
step 6, calculating the calculated value of the j phase phasor except the reference phase
Figure BDA0002038270550000065
j is A, B or C, and the formula is as follows:
Figure BDA0002038270550000066
wherein the content of the first and second substances,
Figure BDA0002038270550000067
the j-phase steady state voltage magnitude value is for normal operation.
Step 7, calculating the relative amplitude error epsilon of the j phase voltageampjRelative phase error epsilon of phase voltagephjThe formula is as follows:
Figure BDA0002038270550000068
wherein, i is equal to j,
Figure BDA0002038270550000069
the voltage amplitude of the i-phase three-phase steady-state voltage after the fault.
Figure BDA00020382705500000610
Wherein the content of the first and second substances,
Figure BDA00020382705500000611
calculating values for j-phase phasors
Figure BDA00020382705500000612
The phase angle of (a) is determined,
Figure BDA00020382705500000613
reference calculation value for reference phase voltage phasor
Figure BDA00020382705500000614
The phase angle of (a) is determined,
Figure BDA00020382705500000615
the phase angle of the j-phase steady-state voltage magnitude after the fault,
Figure BDA00020382705500000616
a phase angle that is a post-fault reference phase steady-state voltage magnitude value.
Step 8, if 0 is more than epsilonampiXi and 0 < epsilonphiAnd if yes, ferromagnetic resonance is judged to occur, otherwise, non-ferromagnetic resonance is judged.
And xi in the step 5 can be set according to the actual field condition, and the value is generally 20% or less.
Example (b):
as shown in fig. 2, the measured waveform at the bus in the section II is taken at two times T1 and T2 in the figure, wherein the time T1 is a normal operation state, and the bus voltage at the time T1 and the phasor of the three-phase voltage A, B, C are obtained, as shown in table 1:
Figure BDA0002038270550000072
table 1.
And at the time of T2, when the flexible power distribution network fails, the failure phenomena are that a C-phase voltage transformation fuse of a bus of a section II in the station is damaged, and a C-phase lightning arrester is exploded. The bus voltage and A, B, C three-phase voltage phasor at the time of T2 are obtained, and are shown in Table 2:
Figure BDA0002038270550000073
table 2.
The occurrence of single-phase grounding or ferromagnetic resonance faults cannot be directly judged by the waveform and phasor table.
Now calculate the relative amplitude error ε of the B phaseampBRelative phase error epsilonphBFor example, the details are as follows:
step 1: when the device is normally operated before a fault, A, B, C three-phase steady-state voltage magnitude values are detected as follows:
Figure BDA0002038270550000071
step 2: after the fault, A, B, C three-phase steady-state voltage and bus zero-sequence voltage are detectedThe effective values are respectively: u shapeA＝45.05V、UB＝65.60V、UC＝69.72V、U0The phasor values of the A, B, C three-phase steady-state voltage are 14.59V:
Figure BDA0002038270550000081
Figure BDA0002038270550000082
and step 3: in data analysis, since the phases of the a-phase detection voltages at times T1 and T2 are both 0 °, a starting phase reference value is calculated using the a-phase amount, and the starting phase reference value includes: the reference value of the phase A starting phase and the reference value of the bus starting phase.
And 4, step 4: as shown in FIG. 3, EA＝59.44V、U′0＝U0＝14.59V、U′A＝UA＝45.05V，EAIs composed of
Figure BDA0002038270550000083
Voltage effective value of (1), U'0Is a calculated value of bus zero sequence voltage, U'ACalculating the A-phase voltage values, and respectively calculating the A-phase initial phase reference values ph by using the cosine law1Bus starting phase reference value ph2：
Figure BDA0002038270550000084
Figure BDA0002038270550000085
And 5: the effective value U of the A-phase steady-state voltage during faultABus zero sequence voltage effective value U0And the A phase initial phase reference value ph1Bus starting phase reference value ph2Reference calculated value of phasor of composition A-phase voltage
Figure BDA0002038270550000086
Bus zero sequence voltage phasor reference calculationValue of
Figure BDA0002038270550000087
Calculating the calculated value of the phase B phasor according to the formula 5
Figure BDA0002038270550000088
Figure BDA0002038270550000089
Figure BDA00020382705500000810
Figure BDA00020382705500000811
Step 6: will be provided with
Figure BDA00020382705500000812
Substituting the amplitude value of the phase voltage into a formula 6 to obtain a relative amplitude error epsilon of the B phase voltageampB。
Figure BDA0002038270550000091
And 7: will be provided with
Figure BDA0002038270550000092
Substituting the phase angle in each phasor into equation 7 to obtain the relative phase error epsilon of the phase voltage of BphB。
Figure BDA0002038270550000093
And 8: from the equations (6) and (7), ε is obtainedampB＝12.88％，εphBAnd when the sum is 7.79 percent and xi is 20 percent, the sum is less than xi, so that the fault is judged to be ferromagnetic resonance.
In the same way, the phasor of phase C can be obtainedCalculated value
Figure BDA0002038270550000094
Then the relative amplitude error epsilon of the C phase voltage is calculatedampCRelative phase error epsilon of C phase voltagephC。
Figure BDA0002038270550000095
Determining epsilonampC＝18.83％，εphCAnd when the sum is 9.81 percent and xi is 20 percent, the total sum is less than xi, so that the fault is judged to be ferromagnetic resonance.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (6)

1. A ferromagnetic resonance distinguishing method for a neutral point ungrounded flexible power distribution network system is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
step 1, detecting zero sequence voltage of fault bus
Figure FDA0003022616800000011
U0Is composed of
Figure FDA0003022616800000012
Effective value of, identify
Figure FDA0003022616800000013
Has a frequency of f0If f is0<Judging that frequency division resonance occurs at 50Hz, if f0>Judging that frequency multiplication resonance occurs at 50 Hz;
step 2, if f050Hz and the effective value U of the zero sequence voltage of the bus after the fault0If the phase voltage exceeds the effective value, the fundamental frequency resonance is judged to occur, or if f is0When the three-phase voltage effective value is simultaneously increased after the fault is 50Hz, the three-phase voltage effective value is increasedJudging the occurrence of fundamental frequency resonance;
step 3, if the situation is not judged in the step 1 or the step 2, detecting the three-phase steady-state voltage magnitude value in normal operation before the fault
Figure FDA0003022616800000014
EA、EB、ECAre respectively as
Figure FDA0003022616800000015
Figure FDA0003022616800000016
Voltage amplitude of (d);
step 4, detecting phasor values of three-phase steady-state voltage and bus zero-sequence voltage after fault
Figure FDA0003022616800000017
Figure FDA0003022616800000018
UA、UB、UC、U0Are respectively as
Figure FDA0003022616800000019
Voltage amplitude of (d); calculating the initial phase reference value ph of a certain phase as a reference phase1i′And bus starting phase reference value ph2i′Wherein i' is A, B or C, and the formula is as follows:
Figure FDA00030226168000000110
Figure FDA00030226168000000111
wherein i' is A or B or C, Ei′I' phase voltage amplitude, U, for normal operationi′Taking a reference phaseVoltage amplitude at fault, U0Taking the voltage amplitude of the zero sequence voltage of the bus in fault;
step 5, enabling the voltage amplitude U to be in fault with the reference phasei′And a reference phase starting phase reference value ph1i′Combined into reference phase voltage phasor reference calculation value
Figure FDA00030226168000000112
The voltage amplitude U of the zero sequence voltage of the bus in fault0And the bus initial phase reference value ph2i′Combined bus zero sequence voltage phasor reference calculation value
Figure FDA00030226168000000113
The formula is as follows:
Figure FDA0003022616800000021
Figure FDA0003022616800000022
step 6, calculating the calculated value of the j phase phasor except the reference phase
Figure FDA0003022616800000023
When i ═ a, j takes B or C, when i ═ B, j takes a or C, when i ═ C, j takes a or B, the formula is as follows:
Figure FDA0003022616800000024
wherein the content of the first and second substances,
Figure FDA0003022616800000025
a j-phase steady state voltage magnitude value for normal operation;
step 7, calculating the relative amplitude error epsilon of the j phase voltageampjRelative phase error epsilon of phase voltagephjThe formula is as follows:
Figure FDA0003022616800000026
wherein, i is equal to j,
Figure FDA0003022616800000027
the voltage amplitude of the i-phase three-phase steady-state voltage after the fault;
Figure FDA0003022616800000028
wherein the content of the first and second substances,
Figure FDA0003022616800000029
calculating values for j-phase phasors
Figure FDA00030226168000000210
The phase angle of (a) is determined,
Figure FDA00030226168000000211
reference calculation value for reference phase voltage phasor
Figure FDA00030226168000000212
The phase angle of (a) is determined,
Figure FDA00030226168000000213
the phase angle of the j-phase steady-state voltage magnitude after the fault,
Figure FDA00030226168000000214
a phase angle that is a post-fault reference phase steady-state voltage magnitude value;
step 8, if 0 is more than epsilonampiXi and 0 < epsilonphiAnd if yes, ferromagnetic resonance is judged to occur, otherwise, non-ferromagnetic resonance is judged.
2. The method for discriminating the ferroresonance of a neutral point ungrounded flexible power distribution grid system according to claim 1, wherein: if the zero sequence voltage transformer is not available,
Figure FDA00030226168000000215
by calculation of formula
Figure FDA00030226168000000216
And calculating to obtain the result, wherein,
Figure FDA00030226168000000217
are phase voltage measurements of A, B, C three phases after a fault, respectively, an
Figure FDA00030226168000000218
Are measured values at the same reference phase.
3. The method for discriminating the ferroresonance of a neutral point ungrounded flexible power distribution grid system according to claim 1, wherein: and the bus zero sequence voltage is the voltage at the bus of the flexible power distribution network system.
4. The method for discriminating the ferroresonance of a neutral point ungrounded flexible power distribution grid system according to claim 1, wherein: the xi is less than or equal to 20 percent
5. The method for discriminating the ferroresonance of the neutral point ungrounded flexible power distribution grid system according to claim 4, wherein: and xi is 20%.
6. The method for discriminating the ferroresonance of the neutral point ungrounded flexible power distribution grid system according to claim 4, wherein: and xi is 10%.
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