CN114720905A - Single-phase high-resistance grounding fault identification and protection method and device for flexible grounding system - Google Patents

Single-phase high-resistance grounding fault identification and protection method and device for flexible grounding system Download PDF

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CN114720905A
CN114720905A CN202210205513.0A CN202210205513A CN114720905A CN 114720905 A CN114720905 A CN 114720905A CN 202210205513 A CN202210205513 A CN 202210205513A CN 114720905 A CN114720905 A CN 114720905A
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sequence
zero
fault
bus
feeder
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汤涛
李晓涵
曾祥君
周宇
肖辉
吴学斌
李安乐
陈春
杨忠毅
罗春辉
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Changsha University of Science and Technology
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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
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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Abstract

The invention provides a method and a device for identifying and protecting a single-phase high-resistance earth fault of a flexible earth system, wherein the fault identification method comprises the following steps: step 1, sampling fault data in real time to obtain a bus zero sequence voltage sequence and zero sequence current sequences of all feeder lines; after the system detects a single-phase high-resistance earth fault, a small resistor is connected in parallel; step 2, obtaining a bus transient zero-sequence voltage sequence and each feeder line transient zero-sequence current sequence based on the bus zero-sequence voltage sequence and the feeder line zero-sequence current sequence acquired in the step 1; step 3, calculating an evaluation transition resistance value of each feeder line based on the bus transient zero-sequence voltage sequence and each feeder line transient zero-sequence current sequence obtained in the step 2; and 4, comparing the evaluation transition resistance of each feeder line obtained in the step 3 with a setting threshold value, and judging a fault line according to a comparison result. And after the fault line is identified, immediately cutting off the fault line. The invention is simple to realize and has strong applicability.

Description

Single-phase high-resistance grounding fault identification and protection method and device for flexible grounding system
Technical Field
The invention belongs to the technical field of relay protection of power systems, and relates to a method and a device for identifying and protecting a single-phase high-resistance earth fault of a flexible earth system.
Background
When the flexible grounding (arc suppression coil and small resistor grounding) system normally operates, the fault is sensed in a resonance grounding mode, and after the single-phase grounding fault occurs, the system delays to put in the small resistor and removes the fault. The flexible grounding system is beneficial to automatic arc quenching of single-phase grounding faults and can reduce the tripping rate of instantaneous grounding fault lines. Therefore, the flexible grounding system integrates the advantages of a resonance grounding system and a small-resistance grounding system, and is widely popularized and applied in China at present.
However, the flexible grounding system mostly uses the fixed time zero sequence overcurrent protection of the small resistance grounding system, and the fixed value of the protection action current is relatively large, so that the protection action current can only react to the fault of which the transition resistance is below 140 Ω generally, and when the system has a single-phase high-resistance fault (the transition resistance is more than 140 Ω), the protection action is often refused.
Aiming at the problems of insufficient recognition and protection sensitivity and the like when a single-phase high-resistance earth fault occurs in a flexible earth system, a fault recognition and protection method and device with higher sensitivity and stronger applicability are needed to be designed.
Disclosure of Invention
The invention aims to solve the technical problem that aiming at the defects of the prior art, the invention provides a method and a device for identifying and protecting the single-phase high-resistance grounding fault of the flexible grounding system, which have strong applicability.
The technical scheme provided by the invention is as follows:
a single-phase high-resistance grounding fault identification method for a flexible grounding system comprises the following steps:
step 1, sampling fault data in real time by using a bus zero sequence voltage transformer and a feeder zero sequence current transformer to obtain a bus zero sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n), k represents the kth feeder line, n is the nth sampling point, and n is 1,2,3 …, wherein, after the system detects the single-phase high-resistance ground fault, a small resistor is put in parallel;
step 2, obtaining a bus transient zero-sequence voltage sequence u based on the bus zero-sequence voltage sequence and the feeder zero-sequence current sequence acquired in the step 10,T(n) and each feeder transient zero sequence current sequence ik0,T(n)；
Step 3, obtaining a bus transient zero sequence voltage sequence u based on the step 20,T(n) and each feeder transient zero sequence current sequence ik0,T(n) calculating an estimated transition resistance value of each feeder line;
step 4, the estimated transition resistance and setting threshold R of each feeder line obtained in the step 3setAnd (taking empirical values) to be compared, and judging a fault line according to a comparison result.
Further, in the step 1, the bus zero sequence voltage sequence u obtained by sampling is detected in real time0And (n) after the zero sequence voltage of the bus tends to be stable, putting the small parallel resistor in order to avoid the transient component influence after the transient component influence on the transition resistance evaluation.
Further, in step 1, after the zero-sequence voltage of the bus tends to be stable, the time when the absolute value of the zero-sequence voltage of the bus is maximum in one period is selected as the time t when the small parallel resistor is put into use1. The parallel small resistor is put into the position with the maximum zero sequence voltage absolute value of the bus, so that the amplitude of the transient quantity can be increased, and the fault feature can be conveniently extracted.
Further, after a single-phase high-resistance earth fault occurs and the time delay delta t (an empirical value is taken), the zero sequence voltage of the bus is judged to tend to be stable.
Further, Δ t was taken to be 0.3 s.
Further, t1And adding 0.02s to the maximum sampling absolute value moment of the bus zero sequence voltage in the last cycle in the delay interval.
Further, in the step 2, the bus zero-sequence voltage sequence and the feeder zero-sequence current sequence collected in the step 1 are filtered by a low-pass filter to remove high-frequency components, so as to obtain a bus zero-sequence voltage sequence of a low frequency band and each feeder zero-sequence current sequence of the low frequency band; based on the bus zero sequence voltage sequence of the low frequency band and the zero sequence current sequence of each feeder line of the low frequency band, subtracting the data after the small resistance is put into the bus to obtain the data after the stable state is achieved by the data after the small resistance is put into the bus to obtain the bus transient zero sequence voltage sequence u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n) of (a). The data after the high-frequency components are filtered by the low-pass filter is used for calculation, so that the influence of the high-frequency disturbance components on the evaluation of the transition resistance can be avoided.
Further, the passband and stopband cutoff frequencies of the low-pass filter are set to 120Hz and 180Hz, respectively.
Furthermore, the data after the small resistance is input is data of 2 cycles after the small resistance is input; the data after the small resistor is put into the stable state is the data of 2 cycles after the stable state is reached.
Further, after a small resistance is put in and a delay of Δ t is delayed, it is determined that a steady state is reached.
Further, the estimated transition resistance value of each feeder line is calculated by the formula (1):
Figure BDA0003529109290000021
in the formula, RkfEvaluation of the transition resistance u for the feed line k0,T(n) represents the bus transient zero sequence voltage of the nth sampling point, i0k,T(N) represents the transient zero-sequence current of the feeder line k at the nth sampling point, wherein N is the number of the sampling points; for a faulty line, the estimated transition resistance calculated by equation (1) is close to the actual connectionThe ground transition resistance is less than or equal to the setting threshold; for a sound line, the evaluation transition resistance calculated by the formula (1) is far larger than a setting threshold, so that the single-phase high-resistance grounding fault identification of the flexible grounding system can be realized.
Further, in step 4, if the evaluated transition resistance of a certain feeder line is greater than RsetIf the estimated transition resistance of a feeder line is less than or equal to R, the feeder line is a sound linesetAnd the feeder line is a fault line.
Further, RsetSet to 5000 omega.
The invention also provides a single-phase high-resistance grounding fault protection method of the flexible grounding system, which is characterized in that the fault line is identified by adopting the fault identification method, and then the fault line is cut off through protection action.
The invention also provides a single-phase high-resistance grounding fault recognition device of the flexible grounding system, which comprises a data acquisition module and a data processing module;
the data acquisition module comprises a bus zero sequence voltage transformer and a feeder zero sequence current transformer and is used for sampling fault data of the flexible grounding system in real time to obtain a bus zero sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n)；
The data processing module is connected with the data acquisition module and used for calculating to obtain a bus transient zero sequence voltage sequence u based on the data acquired by the data acquisition module0,T(n) and each feeder transient zero sequence current sequence ik0,T(n); based on the bus transient state zero sequence voltage sequence u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n) calculating an evaluation transition resistance value of each feeder line; finally, the estimated transition resistance and setting threshold R of each feeder linesetAnd comparing, and judging a fault line according to a comparison result.
The invention also provides a single-phase high-resistance earth fault protection device of the flexible earth system, which comprises the fault identification device and the fault removal module, wherein after the fault line is judged by the fault identification device, the fault line is removed by the fault removal module.
Has the advantages that:
the invention is simple to realize and has strong applicability. Has the following characteristics:
(1) fault characteristic analysis is carried out through transient components generated by the parallel small resistors, and the fault characteristic analysis is basically not influenced by a fault voltage initial phase angle; (2) by reasonably regulating and controlling the input time of the small resistors connected in parallel, the maximum extraction of the fault component amplitude can be realized; (3) the difference of transition resistance evaluated by a fault line and a sound line is obvious, and the transition resistance capability is up to 5k omega; (4) the principle and the calculation process are simple and convenient to realize.
Drawings
Fig. 1 is a simulation model diagram of a power distribution network according to an embodiment of the present invention.
Fig. 2 is a zero sequence equivalent circuit diagram of a power distribution network simulation model according to an embodiment of the invention.
Fig. 3 is a waveform diagram of a bus zero-sequence current and a transient component sequence thereof according to an embodiment of the present invention. Fig. 3(a) shows the parallel small resistance (θ is 90 °) when the absolute value of the zero-sequence voltage sample is the maximum, fig. 3(b) shows the parallel small resistance (θ is 0 °) when the absolute value of the zero-sequence voltage sample is the maximum, and fig. 3(c) shows the parallel small resistance (θ is 90 °) when the absolute value of the zero-sequence voltage sample is 0.
Fig. 4 is a waveform diagram of zero sequence current and its transient component sequence of each feeder line according to the embodiment of the present invention. Fig. 4(a) shows the zero sequence current (θ is 90 °) of each feeder line, and fig. 4(b) shows the transient zero sequence current (θ is 90 °) of each feeder line.
Fig. 5 is a flowchart of transient protection according to an embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific examples.
Example 1:
this embodiment provides a method for identifying a single-phase high-impedance ground fault of a flexible ground system, as shown in fig. 1, the flexible ground system in this embodiment is a 10kV single-ended power supply radial simulation model, in the figure, there are 5 feeders, and the lengths of the feeders are 15km, 20km, 8km, 12km, and 12km, respectively, where the feeders 1 and 5 are an overhead-cable hybrid line, the feeders 2 and 4 are overhead lines, and the feeder 3 is a cableAnd (4) a line. The system neutral point is grounded through a grounding variable arc suppression coil and a parallel small resistor RNThe value was 10 Ω. The system sampling frequency is set uniformly to 5 kHz. Suppose that the feeder 5 has a single-phase earth fault, the transition resistance is 2000 omega, and the distance between a fault point and a bus is 8 km.
For simplicity, the line parameters in this embodiment are set to be the same, and the specific line parameters are:
overhead line:
the positive sequence resistance, the inductance and the capacitance are respectively as follows: r is1＝0.178Ω/km、l1＝1.21mH/km、c1＝0.012uF/km；
The zero sequence resistance, the inductance and the capacitance are respectively as follows: r is0＝0.25Ω/km、l0＝5.54mH/km、c0＝0.008uF/km。
Cable lines:
the positive sequence resistance, the inductance and the capacitance are respectively as follows: r is1＝0.27Ω/km、l1＝0.255mH/km、c1＝0.379uF/km；
The zero sequence resistance, the inductance and the capacitance are respectively as follows: r is0＝2.7Ω/km、l0＝1.109mH/km、c0＝0.280uF/km。
In this embodiment, a transient protection method for a single-phase high-resistance ground fault of a flexible ground system includes the following specific steps:
step 1, sampling data in real time by a bus zero sequence voltage transformer and a feeder zero sequence current transformer at a sampling frequency of 5kHz, delaying for 0.5s after a feeder 5 has a single-phase high-resistance earth fault and is identified as the single-phase high-resistance earth fault by a system, acquiring the time when the zero sequence voltage sampling absolute value is maximum in the last cycle of a delay interval, and then, after 0.02s later (the time is t1) Putting in parallel small resistors, and sampling by a mutual inductor to obtain a faulted bus zero-sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n)，k＝1,2,3,4,5。
Step 2, filtering out high-frequency components of bus zero-sequence voltage and high-frequency components of 5 feeder zero-sequence currents through a low-pass filter, wherein the pass-band cut-off frequency and the stop-band cut-off frequency of the low-pass filter are set to be 120Hz and 180 Hz;
subtracting the data of 2 cycles after the small resistor is put in by the data of 2 cycles after the small resistor is put in for obtaining the bus zero sequence voltage u0(n) and its transient component sequence u0,T(n) is shown in FIG. 3. FIG. 4 is a zero sequence current and its transient component sequence i of 5 feeder linesk0,T(n)；。
And step 3, calculating the estimated transition resistance values of the feeder lines 1-5 by using the formula (1), wherein the estimated transition resistance values are 13.411k omega, 132.3k omega, 8.438k omega, 220.73k omega and 1.93k omega respectively.
And 4, because the estimated transition resistance of the fault line is approximate to the actual transition resistance and is smaller than the setting threshold, the estimated transition resistance of the sound line is far larger than the setting threshold. Therefore, the feeder 5 is determined to be a faulty line.
As can be seen from fig. 3, after the flexible grounding system is connected to the small resistors in parallel, the amplitude of the transient component of the flexible grounding system is mainly determined by the connection time of the small resistors, and is hardly affected by the fault time (fault initial phase angle θ); and when the sampling absolute value of the zero sequence voltage of the bus is maximum, a small resistor is put into the bus, and the amplitude of the fault transient component is maximum.
Example 2:
the embodiment provides a single-phase high-resistance grounding fault protection method for a flexible grounding system, which is implemented by identifying a fault line by using the fault identification method in the embodiment 1 and then removing the fault line by tripping.
Example 3:
the embodiment provides a single-phase high-resistance grounding fault recognition device of a flexible grounding system, which comprises a data acquisition module and a data processing module;
the data acquisition module comprises a bus zero sequence voltage transformer and a feeder zero sequence current transformer and is used for sampling fault data of the flexible grounding system in real time to obtain a bus zero sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n)；
The data processing module is connected with the data acquisition module and used for calculating to obtain a bus transient zero sequence voltage sequence u based on the data acquired by the data acquisition module0,T(n) and each feeder transient zero sequence current sequence ik0,T(n); based on the transient zero sequence of the busSequence of voltages u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n) calculating an estimated transition resistance value of each feeder line; finally, the estimated transition resistance and setting threshold R of each feeder linesetAnd comparing, and judging a fault line according to a comparison result.
The device in this embodiment may be used to implement the method described in embodiment 1, and the working principle of each functional module in the device refers to each step of the method described in embodiment 1.
Example 4:
the embodiment provides a single-phase high-resistance grounding fault protection device of a flexible grounding system, which comprises a fault recognition device and a fault removal module, wherein after a fault line is judged by the fault recognition device, the fault line is tripped and removed by the fault removal module.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of the present application, which is to be determined by the claims appended hereto.

Claims (10)

1. A method for identifying a single-phase high-resistance grounding fault of a flexible grounding system is characterized by comprising the following steps:
step 1, sampling fault data in real time to obtain a bus zero sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n), k represents the kth feeder line, n is the nth sampling point, and n is 1,2,3 …, wherein, after the system detects the single-phase high-resistance ground fault, a small resistor is put in parallel;
step 2, obtaining a bus transient zero-sequence voltage sequence u based on the bus zero-sequence voltage sequence and the feeder zero-sequence current sequence acquired in the step 10,T(n) and each feeder transient zero sequence current sequence ik0,T(n)；
Step 3, obtaining the temporary bus based on the step 2State zero sequence voltage sequence u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n) calculating an estimated transition resistance value of each feeder line;
step 4, the estimated transition resistance and setting threshold R of each feeder line obtained in the step 3setAnd comparing, and judging a fault line according to a comparison result.
2. The method for identifying the single-phase high-resistance grounding fault of the flexible grounding system as claimed in claim 1, wherein in the step 1, the sampled bus zero-sequence voltage sequence u is detected in real time0And (n), after the zero sequence voltage of the bus tends to be stable, putting the bus into a small resistor connected in parallel.
3. The method for identifying the single-phase high-resistance ground fault of the flexible grounding system as claimed in claim 2, wherein in the step 1, a time point at which an absolute value of the zero-sequence voltage of the bus is maximum in a period after the zero-sequence voltage of the bus tends to be in a steady state is selected as a time point t for putting the small parallel resistors1。
4. The method for identifying the single-phase high-resistance grounding fault of the flexible grounding system according to claim 3, wherein after the single-phase high-resistance grounding fault occurs and is delayed by Δ t, it is determined that the zero-sequence voltage of the bus tends to be in a steady state.
5. The method according to claim 4, wherein t is t1And adding 0.02s to the maximum sampling absolute value moment of the bus zero sequence voltage in the last cycle in the delay interval.
6. The method for identifying the single-phase high-resistance ground fault of the flexible grounding system according to claim 1, wherein in the step 2, the bus zero-sequence voltage sequence and the feeder zero-sequence current sequence collected in the step 1 are filtered by a low-pass filter to remove high-frequency components, so as to obtain a bus zero-sequence voltage sequence of a low frequency band and each feeder zero-sequence current sequence of the low frequency band; bus bar zero based on low frequency bandThe sequence voltage sequence and the zero sequence current sequence of each feeder line of the low frequency band subtract the data which is obtained after the small resistance is added and reaches the stable state by the data which is obtained after the small resistance is added to obtain the bus transient state zero sequence voltage sequence u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n)。
7. The method for identifying the single-phase high-resistance ground fault of the flexible grounding system according to claim 4, wherein the evaluation transition resistance value of each feeder line is calculated by formula (1):
Figure FDA0003529109280000011
in the formula, RkfEvaluation of the transition resistance u for the feed line k0,T(n) represents the bus transient zero sequence voltage of the nth sampling point, i0k,TAnd (N) represents the transient zero-sequence current of the feeder line k at the nth sampling point, wherein N is the number of the sampling points.
8. A single-phase high-resistance earth fault protection method of a flexible earth system is characterized in that a fault line is identified by the fault identification method of any one of claims 1-7, and then the fault line is cut off.
9. A single-phase high-resistance earth fault recognition device of a flexible earth system is characterized by comprising a data acquisition module and a data processing module;
the data acquisition module comprises a bus zero sequence voltage transformer and a feeder zero sequence current transformer and is used for sampling fault data of the flexible grounding system in real time to obtain a bus zero sequence voltage sequence u0(n) and each feeder zero sequence current sequence ik0(n)；
The data processing module is connected with the data acquisition module and used for calculating to obtain a bus transient zero sequence voltage sequence u based on the data acquired by the data acquisition module0,T(n) and each feeder transient zero sequence current sequence ik0,T(n); based on the bus transient zero sequence voltage sequence u0,T(n) and each feeder transient zero sequence current sequence ik0,T(n) calculating an evaluation transition resistance value of each feeder line; finally, the estimated transition resistance and setting threshold R of each feeder linesetAnd comparing, and judging a fault line according to a comparison result.
10. A single-phase high-resistance earth fault protection device of a flexible earth system, comprising the fault recognition device of claim 9 and a fault removal module, wherein after a fault line is determined by the fault recognition device, the fault line is removed by the fault removal module.
CN202210205513.0A 2022-03-02 2022-03-02 Single-phase high-resistance grounding fault identification and protection method and device for flexible grounding system Pending CN114720905A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115951264A (en) * 2023-03-14 2023-04-11 北京国电通网络技术有限公司 Line ground fault detection method, device, equipment and medium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115951264A (en) * 2023-03-14 2023-04-11 北京国电通网络技术有限公司 Line ground fault detection method, device, equipment and medium
CN115951264B (en) * 2023-03-14 2023-05-23 北京国电通网络技术有限公司 Line ground fault detection method, device, equipment and medium

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