CN116736033A - Fault sensing method, device, equipment and medium of power distribution network resonance grounding system - Google Patents

Fault sensing method, device, equipment and medium of power distribution network resonance grounding system Download PDF

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Publication number
CN116736033A
CN116736033A CN202310576319.8A CN202310576319A CN116736033A CN 116736033 A CN116736033 A CN 116736033A CN 202310576319 A CN202310576319 A CN 202310576319A CN 116736033 A CN116736033 A CN 116736033A
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China
Prior art keywords
distribution network
power distribution
ground
target frequency
grounding
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Inventor
刘红文
柴晨超
杨莉
张春丽
杨金东
唐立军
邓正东
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Electric Power Research Institute of Yunnan Power Grid Co Ltd
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Electric Power Research Institute of Yunnan Power Grid Co Ltd
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Priority to CN202310576319.8A priority Critical patent/CN116736033A/en
Publication of CN116736033A publication Critical patent/CN116736033A/en
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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
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
    • 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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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

The embodiment of the application discloses a fault sensing method, device, equipment and medium of a resonant grounding system of a power distribution network, and the method, device, equipment and medium are used for acquiring a target frequency of a detection current; determining reference power distribution network impedance under the detection current of the target frequency and ground power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network through injecting the detection current of the target frequency; determining the parallel impedance of the capacitance converted from the distributed capacitance of the arc suppression coil inductance of the power distribution network to the ground to the PT secondary side and the grounding transitional resistance; further determining the loss tangent value of the power distribution network to the ground under the detection current of the injection target frequency; for determining a fault condition of a resonant ground system of the distribution network. The dielectric loss factor of the detection current of the target frequency is detected in real time through the detection current of the target frequency, so that the size of the insulation resistance of the distribution network to the ground is reflected, the ground fault can be detected rapidly, and the sensing reliability and sensitivity can be improved by reducing the frequency of the injection current signal.

Description

Fault sensing method, device, equipment and medium of power distribution network resonance grounding system
Technical Field
The application relates to the technical field of power distribution network ground fault detection, in particular to a fault sensing method, device, equipment and medium of a power distribution network resonance ground system.
Background
The high-resistance grounding faults of the distribution network are usually accompanied by the generation of electric arcs, the faults of the distribution lines falling on the ground and overhead insulated wires are usually high-resistance, the active arc extinction and protection equipment cannot sense the faults of the lines, the electric arcs cannot be restrained for a long time, and the overvoltage and leakage current of fault points can cause personal electric shock, forest fire and interphase faults; therefore, on the premise of actively suppressing and isolating the ground fault, the occurrence of the high-resistance fault needs to be detected quickly, and in order to accurately detect the high-resistance ground fault, the generation and extinction characteristics of the ground fault arc need to be analyzed, and a sensing method suitable for the high-resistance arc ground fault is provided.
In the prior art, the sensing of the high-resistance fault mainly adopts two methods of passive sensing and active sensing, wherein the passive sensing is used for judging the transient state and steady-state voltage and current characteristic quantity generated before and after the occurrence of the ground fault; the active sensing senses the ground fault through actively injecting power frequency or high frequency signals, extracting and analyzing the fed back voltage and current characteristics; however, the high-resistance fault sensing method has large calculated amount in engineering application, has insufficient sensing reliability and sensitivity, and can only sense the high-resistance fault below 2kΩ in the current engineering application.
In general, a large amount of neutral points of the power distribution network are grounded by resonance, and under the condition of the resonance grounding, as arc suppression coil inductance is introduced, such as injection of a low-frequency signal, the arc suppression coil inductance presents a low resistance state, so that fault perception sensitivity of the power distribution network is affected, and independent analysis on a resonance grounding system is necessary.
Disclosure of Invention
Based on this, it is necessary to provide a fault sensing method, device, equipment and medium for a resonant grounding system of a power distribution network in order to solve the above problems.
To achieve the above object, a first aspect of the present application provides a fault sensing method of a resonant ground system of a power distribution network, the method comprising:
acquiring a target frequency of the detection current;
determining reference power distribution network impedance under the detection current of the target frequency and ground power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network through injecting the detection current of the target frequency;
determining the parallel impedance of the capacitor converted from the arc suppression coil inductance of the power distribution network to the distributed capacitance of the ground to the PT secondary side and the grounding transition resistance according to the reference power distribution network impedance and the grounding power distribution network impedance;
according to the parallel impedance of the capacitance of the arc suppression coil inductance of the power distribution network, which is converted into the capacitance of the PT secondary side and the grounding transitional resistance, determining the dielectric loss tangent value of the power distribution network to the ground under the detection current of the injection target frequency;
and determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value.
Further, the acquiring the target frequency of the detection current includes:
acquiring a distribution network ground distributed capacitance and an arc suppression coil inductance;
and determining the target frequency of the detected current according to the distribution network ground distributed capacitance and the arc suppression coil inductance.
Further, the determining the target frequency of the injection detection current according to the distribution network ground distributed capacitance and the arc suppression coil inductance specifically includes:
according to the formulaDetermining a target frequency of the injection detection current, wherein f 0 To detect the target frequency of the current, f offset Outputting the signal for the current sourceThe deviation value of the resonant frequency of the distributed capacitance to ground and the arc suppression coil inductance of the number frequency deviation distribution network is round () which is a round function, L S For arc-suppression coil inductance, C S The capacitance is distributed for the distribution network to ground.
Further, the determining, by injecting the detection current of the target frequency, the reference power distribution network impedance under the detection current of the target frequency when the power distribution network operates normally and the ground power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding specifically includes:
according to the formulaDetermining a reference power distribution network impedance;
according to the formulaDetermining the impedance of a grounded power distribution network;
wherein Z' 02 With reference to the distribution network impedance,// represents impedance parallel;injecting current into the current source; />Is the voltage at two ends of the current source during normal operation; r is R 2 Is PT DC resistance and line resistance R L The resistor is converted to the secondary side of the electromagnetic voltage transformer PT; l (L) 2 Converting PT leakage inductance and line inductance into PT secondary side inductance; l (L) S2 Is arc suppression coil inductance L S Inductance converted to PT secondary side; c (C) S2 For converting the distribution network capacitance to the PT secondary side capacitance, Z' 02 For grounding the impedance of the distribution network>Is the voltage across the current source when the ground fault occurs; r is R d2 The transition resistance to ground translates to the resistance on the secondary side of PT.
Further, the determining, according to the reference power distribution network impedance and the ground power distribution network impedance, the parallel impedance of the capacitance of the power distribution network arc suppression coil inductance to the ground distributed capacitance converted to the PT secondary side and the ground transition resistance specifically includes:
according to the formulaDetermining the parallel impedance of a capacitor of the distribution network arc suppression coil inductance to the ground distributed capacitance converted to the PT secondary side and the grounding transition resistance;
wherein Z is f02 To eliminate R 2 、L 2 Arc suppression coil inductance L of affected power distribution network resonant grounding system S Capacitance C converted from ground distributed capacitance to PT secondary side S2 And a ground transition resistance R d2 Is Z f02 。
Further, the determining the dielectric loss tangent value of the distribution network to the ground under the detection current of the injection target frequency according to the parallel impedance of the capacitance of the distribution network arc suppression coil inductance to the distributed capacitance to the ground to the PT secondary side and the grounding transition resistance specifically includes:
according to the formulaDetermining the loss tangent value of the power distribution network to the ground under the current signal of the injection target frequency; wherein omega 0 Is to inject a current source with a frequency f 0 Corresponding angular frequency, delta f0 Is Z f02 Residual angle of impedance angle, I n Is a single-phase grounding transition resistance.
Further, the determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value comprises the following steps:
determining a dielectric loss tangent to ground at a detected current at a target frequency;
if the dielectric loss tangent value to the ground is larger than the threshold value, the resonant grounding system of the power distribution network has a grounding fault;
and if the dielectric loss tangent value to the ground is smaller than or equal to the threshold value, the power distribution network resonance grounding system normally operates.
To achieve the above object, a second aspect of the present application provides a fault sensing apparatus for a resonant ground system of a power distribution network, the apparatus comprising:
an acquisition unit configured to acquire a target frequency of the detection current;
the control unit is used for determining reference power distribution network impedance under the detection current of the target frequency and grounding power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network through injecting the detection current of the target frequency;
the control unit is also used for determining the parallel impedance of the capacitor of the arc suppression coil inductance of the power distribution network, which is converted to the capacitance of the PT secondary side and the grounding transition resistance, to the ground distributed capacitance according to the reference power distribution network impedance and the grounding power distribution network impedance;
the control unit is further used for determining the dielectric loss tangent value of the distribution network to the ground under the detection current of the injection target frequency according to the parallel impedance of the capacitance of the distribution network arc suppression coil inductance to the PT secondary side and the grounding transition resistance;
and a failure judgment unit. And the fault state of the resonant grounding system of the power distribution network is determined according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value.
To achieve the above object, a third aspect of the present application provides a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of the method according to the first aspect.
To achieve the above object, a fourth aspect of the present application provides a computer-readable storage medium storing a computer program, which when executed by a processor causes the processor to perform the steps of the method according to the first aspect.
The embodiment of the application has the following beneficial effects:
the application obtains the target frequency of the detection current by injecting the targetDetecting current of frequency, and detecting dielectric loss tangent value of detecting current of power distribution network at target frequency in real time Reflects the size of the insulation resistance of the distribution network to the ground, when +.>And when the set threshold value is exceeded, judging that the power distribution network has a ground fault. The target frequency of the detection current determined by the application is near the resonance point, and the dielectric loss tangent value tg delta of the resonance grounding system to the ground f0 The sensitivity of detecting the ground fault is improved, whether the single-phase ground fault occurs in the system can be judged rapidly, and calculation is simpler.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Wherein:
FIG. 1 is a flow chart of a method for sensing a ground fault in a resonant ground system of a power distribution network according to one embodiment;
FIG. 2 is an equivalent zero sequence loop diagram of a ground fault sensing device in a resonant ground system of a power distribution network in one embodiment;
FIG. 3 is an equivalent simplified zero sequence loop diagram of a ground fault sensing device in a resonant ground system of a power distribution network in one embodiment;
FIG. 4 is a graph showing a change in dielectric loss tangent of a ground fault sensing device in a resonant ground system of a power distribution network at a ground fault of 10A in accordance with one embodiment;
FIG. 5 is a graph showing a change in dielectric loss tangent of a ground fault sensing device in a resonant ground system of a power distribution network at a ground fault of 100A in one embodiment;
fig. 6 is a schematic structural diagram of a ground fault sensing device in a resonant ground system of a power distribution network according to an embodiment.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In an embodiment of the present application, referring to fig. 1, fig. 1 is a schematic flow diagram of a method for sensing a ground fault in a resonant ground system of a power distribution network in an embodiment, and the method for sensing a ground fault in a resonant ground system of a power distribution network includes steps S110 to S150.
Step S110, obtaining a target frequency of the detection current;
in an embodiment of the present application, fig. 2 shows an equivalent zero sequence loop diagram of a ground fault sensing device in a resonant ground system of a power distribution network in one embodiment,to detect a current source; c (C) S Distributing capacitance to the ground for the distribution network; r is R d Is a single-phase grounding transition resistance; the N point is the neutral point of the distribution system, and the voltage of the N point is +.>PT is an electromagnetic voltage transformer, one side of PT, which is connected with a neutral point of a power distribution network, is a primary side, and the transformation ratio is n; r is R L The direct current resistor is a system line direct current resistor; l is the inductance of the system line, L S Is the arc suppression coil inductance.
Ignoring the excitation impedance of the PT, looking into from the PT secondary side,an equivalent simplified zero sequence loop diagram of a ground fault sensing device in a resonant ground system of a power distribution network in one embodiment as shown in fig. 3 is obtained, and in fig. 3, R 2 Converting the PT direct current resistance and the line resistance RL into a PT secondary side resistance; l (L) 2 Converting PT leakage inductance and line inductance into PT secondary side inductance; c (C) S2 Converting the distributed capacitance of the power distribution network to the capacitance of the PT secondary side; r is R d2 The transition resistance to ground is converted into a resistor on the PT secondary side; l (L) S2 Is arc suppression coil inductance L S Inductance converted to PT secondary side, i.e. L S2 ＝L S n 2 ；C S2 And C S The calculation relation between the two is as follows: c (C) S2 ＝n 2 C s ，R d And R is d2 The calculation relation between the two is as follows: r is R d2 ＝R d /n 2 。
In the embodiment of the application, in order to improve the sensitivity of detecting the ground fault, for the resonant ground system of the power distribution network, a current source injects a target frequency f of a detection current 0 Should be near the resonance point and need to deviate from a certain value. Therefore, the current source output frequency of the resonant grounding system is controlled by the arc suppression coil inductance L S And distribution network to ground distributed capacitance C S Decision, according to L of each distribution network S And C S The current injected into the corresponding frequency is adjusted.
Further, the step S110 specifically includes:
acquiring a distribution network ground distributed capacitance and an arc suppression coil inductance; specifically, the distribution network distributes the capacitance C to the ground S This can be achieved in a number of ways, for example by injecting a pilot current.
Determining the target frequency of the detection current according to the distribution network ground distributed capacitance and the arc suppression coil inductance; the method specifically comprises the following steps:
according to the formulaDetermining a target frequency of the injected detection current, wherein f 0 To detect the target frequency of the current, f offset Distributing capacitance and extinction of power distribution network to ground for frequency offset of current source output signalThe deviation value of the coil inductance resonance frequency is 1-5 Hz in the embodiment, round () is a round function, L S For arc-suppression coil inductance, C S The capacitance is distributed for the distribution network to ground.
More specifically, f offset The smaller f 0 The closer to the resonant frequency, the larger the parallel impedance of the arc suppression coil and the system capacitor is, the larger the dielectric loss tangent value is under a certain grounding transition resistance, and the fault perception sensitivity is improved.
Step S120, determining reference power distribution network impedance under the detection current of the target frequency and ground power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network by injecting the detection current of the target frequency;
in the embodiment of the application, the detection current with the target frequency is injected into the power distribution network between the neutral point and the ground of the power distribution network through the electromagnetic voltage transformer, and preferably, the output frequency of the signal detection power supply is f 0 When the current is detected, the primary side of the electromagnetic voltage transformer, namely the frequency of the neutral point of the system is f 0 Is not more than 10% of the nominal phase voltage amplitude of the system.
Further, step S120 specifically includes:
according to the formulaDetermining a reference power distribution network impedance;
according to the formulaDetermining the impedance of a grounded power distribution network;
wherein Z' 02 With reference to the distribution network impedance,// represents impedance parallel;injecting current into the current source; />For normally operating current sourceThe voltage across the terminals; r is R 2 Is PT DC resistance and line resistance R L The resistor is converted to the secondary side of the electromagnetic voltage transformer PT; l (L) 2 Converting PT leakage inductance and line inductance into PT secondary side inductance; l (L) S2 Is arc suppression coil inductance L S Inductance converted to PT secondary side; c (C) S2 For converting the distribution network capacitance to the PT secondary side capacitance, Z' 02 For grounding the impedance of the distribution network>Is the voltage across the current source when the ground fault occurs; r is R d2 The transition resistance to ground translates to the resistance on the secondary side of PT.
Step S130, determining the parallel impedance of the capacitor of the arc suppression coil inductance of the power distribution network, which is converted to the capacitance of the PT secondary side and the grounding transition resistance, to the ground distributed capacitance according to the reference power distribution network impedance and the grounding power distribution network impedance;
further, step S130 specifically includes:
according to the formulaDetermining the parallel impedance of a capacitor of the distribution network arc suppression coil inductance to the ground distributed capacitance converted to the PT secondary side and the grounding transition resistance;
wherein Z is f02 To eliminate R 2 、L 2 Arc suppression coil inductance L of affected power distribution network resonant grounding system S Capacitance C converted from ground distributed capacitance to PT secondary side S2 And a ground transition resistance R d2 Is Z f02 。
Step S140, determining the dielectric loss tangent value of the distribution network to the ground under the detection current of the injection target frequency according to the parallel impedance of the capacitance of the distribution network arc suppression coil inductance to the PT secondary side and the grounding transition resistance;
further, step S140 specifically includes:
according to the formulaDetermining the loss tangent value of the power distribution network to the ground under the current signal of the injection target frequency; wherein omega 0 Is to inject a current source with a frequency f 0 Corresponding angular frequency, delta f0 Is Z f02 Residual angle of impedance angle, R d Is a single-phase grounding transition resistance.
In a specific embodiment, a concept of dielectric loss tangent is introduced, the ground fault of the distribution line breaks the system insulation, the ground transition resistance increases the loss, and the tg delta is known from the above formula f0 And (3) withInversely proportional. Observing the above, the distribution network is to ground distributed capacitance C S Arc suppression coil inductance L S And the target frequency f of current source injection 0 All can affect the dielectric loss tangent, when f 0 Equal to L S And C S Is>Zero, resonant ground system dielectric loss tangent tgdelta to ground f0 Towards infinity, thereby determining the injection frequency of the current source.
tgδ f0 With the target frequency f of the detected current 0 And distribution network to ground distributed capacitance C S Inversely proportional. tg delta f0 Reflects the magnitude of the leakage resistance of the distribution network to the ground, and when tg delta f0 When the power distribution network is increased to a certain value, the occurrence of the ground fault of the power distribution network can be judged.
Step S150, determining a fault state of the resonant grounding system of the power distribution network according to a comparison relation between the dielectric loss tangent value to the ground and a threshold value;
further, step S150 specifically includes:
determining a dielectric loss tangent to ground at a detected current at a target frequency;
if the loss tangent value of the dielectric material to the ground is larger than the threshold value, the resonant grounding system of the power distribution network has a grounding fault;
and if the dielectric loss tangent value to the ground is smaller than or equal to the threshold value, the resonant grounding system of the power distribution network normally operates.
In an embodiment of the application, tgδ f0 Reflects the size of the insulation resistance of the distribution network to the ground, when tg delta f0 When the threshold value is exceeded, the occurrence of the ground fault of the power distribution network can be judged, and the threshold value is generally set to be 0.01-0.2.
According to the fault sensing method of the power distribution network resonant grounding system, the ground dielectric loss tangent value of the power distribution network under the detection current of the injected target frequency is determined through the detection current of the injected target frequency, so that the fault state of the power distribution network resonant grounding system is determined, the calculation is simpler, and the fault sensing is faster and more efficient.
In some embodiments, assuming a 10kV power distribution network resonant grounding system, the capacitance current is 10A, the arc suppression coil overcompensates 1A-10A, the grounding transition resistance is 1kΩ -100 kΩ, according to the followingObtainable f offset Tg delta at 2Hz f0 The situation is changed.
As shown in fig. 4, fig. 4 is a graph of dielectric loss tangent change of a ground fault sensing device in a resonant ground system of a power distribution network when the capacitance current is 10A during a ground fault in an embodiment; as can be seen from fig. 4, under the condition of a certain capacitance current of the power distribution network, the larger the ground fault transition resistance is, tg delta is f0 The smaller; the compensation degree of the arc suppression coil is relative to tg delta f0 Is not so much affected. For a 10kV power distribution network resonance grounding system, the capacitance current is 10A, the arc suppression coil overcompensates 1A-10A, the grounding transition resistance is 1kΩ -100 kΩ, and f offset At 2Hz tg delta f0 The variation is shown in fig. 4. When the power distribution network operates normally, tg delta f0 Near zero, in dielectric loss delta Δtgδ f0 =0.05 is the ground fault determination limit, and when the distribution network dielectric loss tangent variation exceeds this value, single-phase grounding occurs. The method can identify ground faults with a transition resistance of 100kΩ and less for systems with a capacitance current of 10A and arc suppression coil overcompensation of 1A to 10A.
In some embodimentsIn the formula, a 10kV power distribution network resonance grounding system is assumed, the capacitance current is 100A, the arc suppression coil overcompensates 1A-10A, the grounding transition resistance is 1kΩ -100 kΩ, and the formula is based onObtainable f offset Tg delta at 2Hz f0 The situation is changed.
As shown in fig. 5, fig. 5 is a graph of dielectric loss tangent change of a ground fault sensing device in a resonant ground system of a power distribution network at a ground fault of 100A capacitive current according to an embodiment. For a 10kV power distribution network resonance grounding system, the capacitance current is 100A, the arc suppression coil overcompensates 1A-10A, the grounding transition resistance is 1kΩ -100 kΩ, and f offset At 2Hz tg delta f0 The variation is shown in fig. 5. Still in Δtgδ f0 =0.05 as a limit, i.e. tg δ f0 When the amount of change exceeds 0.05, it is considered that single-phase grounding occurs. The method can identify ground faults with a transition resistance of 11kΩ and below for a system with a capacitive current of 100A and overcompensation of the arc suppression coil 1A to 10A.
In summary, for the resonant grounding system of the power distribution network, the current source injection frequency is determined byDetermining when f offset =2hz, Δtgδ f0 =0.05 as a limit value, and adopting a ground fault sensing method of dielectric loss increment, as the capacitance current of the power distribution network increases, the fault sensing capability gradually decreases. The capacitive current is below 100A, the sensing capability of the ground fault transition resistor is between 11kΩ and 100kΩ, and the detection sensitivity meets the engineering application requirements.
According to the national standard GB/T50064 alternating current electric device overvoltage protection and insulation fit design specification, the capacitance current of the distribution network is larger than 10A, an arc suppression coil is adopted for grounding, and the residual fault current of an arc suppression coil grounding system is not larger than 10A, so that the high-resistance fault sensing method has higher sensitivity.
By adopting the technical scheme of the embodiment, the detection current of the target frequency is injected by acquiring the target frequency of the detection current, so that the parallel impedance of the capacitance converted from the inductance of the arc suppression coil of the power distribution network to the ground distributed capacitance to the capacitance of the PT secondary side and the grounding transition resistance is determined; further determining the loss tangent value of the power distribution network to the ground under the detection current of the injection target frequency according to the loss tangent value; and determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value. The fault sensing method has the advantages that the detection sensitivity is improved, the engineering application requirements can be met, and the practicability and the safety are better.
In an embodiment of the present application, referring to fig. 6, fig. 6 is a schematic structural diagram of a ground fault sensing device in a resonant ground system of a power distribution network, where the fault sensing device of the resonant ground system of the power distribution network includes: an acquisition unit 102, a control unit 104, and a failure determination unit 106.
Wherein the acquisition unit 102 is configured to acquire a target frequency of the detection current; the specific function and processing of the acquisition unit 102 is also referred to in step S110.
A control unit 104 configured to determine, by injecting a detection current of a target frequency, a reference distribution network impedance at the detection current of the target frequency when the distribution network is operating normally and a ground distribution network impedance at the detection current of the target frequency when the system is single-phase grounded; the specific function and process of the control unit 104 is also referred to as step S120.
The control unit 104 is further configured to determine, according to the reference power distribution network impedance and the ground power distribution network impedance, the parallel impedance of the capacitance converted from the arc suppression coil inductance of the power distribution network to the ground distributed capacitance to the capacitance of the PT secondary side and the ground transition resistance; the specific function and processing of the control unit 104 is also referred to in step S130.
The control unit 104 is further configured to determine a dielectric loss tangent value to the ground of the power distribution network under the detection current of the injection target frequency according to the parallel impedance of the power distribution network arc suppression coil inductance to the capacitance of the PT secondary side and the grounding transition resistance; the specific function and process of the control unit 104 also refer to step S140.
A fault determination unit 106 configured to determine a fault state of the resonant ground system of the power distribution network according to a comparison relationship between the dielectric loss tangent value to ground and a threshold value; the specific function and processing of the failure determination unit 106 is also referred to step S150.
By adopting the technical scheme of the embodiment, the parallel impedance of the capacitance of the distribution network arc suppression coil inductance to the ground distributed capacitance converted to the PT secondary side and the grounding transition resistance is determined by acquiring the target frequency of the detection current and injecting the detection current of the target frequency under different states of the system; further determining the loss tangent value of the power distribution network to the ground under the detection current of the injection target frequency according to the loss tangent value; and determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value. Compared with the existing fault sensing method, the sensing capacity range of the ground fault transition resistor is larger, and the sensitivity is higher.
In one embodiment, a computer device is provided, comprising a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the steps of the method embodiments described above.
In one embodiment, a computer-readable storage medium is provided, storing a computer program that, when executed by a processor, causes the processor to perform the steps of the method embodiments described above.
Those skilled in the art will appreciate that all or part of the processes in the methods of the above embodiments may be implemented by a computer program for instructing relevant hardware, where the program may be stored in a non-volatile computer readable storage medium, and where the program, when executed, may include processes in the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), memory bus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (10)

1. A fault sensing method for a resonant ground system of a power distribution network, the method comprising:
acquiring a target frequency of the detection current;
determining reference power distribution network impedance under the detection current of the target frequency and ground power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network through injecting the detection current of the target frequency;
determining the parallel impedance of the capacitor converted from the arc suppression coil inductance of the power distribution network to the distributed capacitance of the ground to the PT secondary side and the grounding transition resistance according to the reference power distribution network impedance and the grounding power distribution network impedance;
according to the parallel impedance of the capacitance of the arc suppression coil inductance of the power distribution network, which is converted into the capacitance of the PT secondary side and the grounding transitional resistance, determining the dielectric loss tangent value of the power distribution network to the ground under the detection current of the injection target frequency;
and determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value.
2. The fault awareness method of a resonant ground system of a power distribution network of claim 1, the obtaining a target frequency of the detected current comprising:
acquiring a distribution network ground distributed capacitance and an arc suppression coil inductance;
and determining the target frequency of the detected current according to the distribution network ground distributed capacitance and the arc suppression coil inductance.
3. The fault sensing method of the resonant grounding system of the power distribution network according to claim 2, wherein the determining the target frequency of the injected detection current according to the power distribution network to ground distributed capacitance and the arc suppression coil inductance specifically comprises:
according to the formulaDetermining a target frequency of the injection detection current, wherein f 0 To detect the target frequency of the current, f offset For the deviation value of the frequency deviation distribution network of the current source output signal to the ground distributed capacitance and the resonance frequency of the arc suppression coil inductance, round () is a round function, L S For arc-suppression coil inductance, C S The capacitance is distributed for the distribution network to ground.
4. A fault sensing method for a resonant ground system of a power distribution network according to claim 3, wherein the determining the reference power distribution network impedance at the detected current of the target frequency when the power distribution network is operating normally and the ground power distribution network impedance at the detected current of the target frequency when the system is single-phase grounded by injecting the detected current of the target frequency specifically comprises:
according to the formulaDetermining a reference power distribution network impedance;
according to the formulaDetermining the impedance of a grounded power distribution network;
wherein Z' 02 With reference to the distribution network impedance,// represents impedance parallel;injecting current into the current source; />Is the voltage at two ends of the current source during normal operation; r is R 2 Is PT DC resistance and line resistance R L The resistor is converted to the secondary side of the electromagnetic voltage transformer PT; l (L) 2 Converting PT leakage inductance and line inductance into PT secondary side inductance; l (L) S2 Is arc suppression coil inductance L S Inductance converted to PT secondary side; c (C) S2 For converting the distribution network capacitance to the PT secondary side capacitance, Z' 02 For grounding the impedance of the distribution network>Is the voltage across the current source when the ground fault occurs; r is R d2 The transition resistance to ground translates to the resistance on the secondary side of PT.
5. The method for sensing faults of a resonant grounding system of a power distribution network according to claim 4, wherein determining a parallel impedance of a capacitor of a distributed capacitor of an arc suppression coil of the power distribution network to ground converted to a capacitor of a PT secondary side and a grounding transition resistance according to the reference power distribution network impedance and the grounding power distribution network impedance specifically comprises:
according to the formulaDetermining the parallel impedance of a capacitor of the distribution network arc suppression coil inductance to the ground distributed capacitance converted to the PT secondary side and the grounding transition resistance;
wherein Z is f02 To eliminate R 2 、L 2 Arc suppression coil inductance L of affected power distribution network resonant grounding system S Capacitance C converted from ground distributed capacitance to PT secondary side S2 And a ground transition resistance R d2 Is Z f02 。
6. The method for sensing faults of a resonant grounding system of a power distribution network according to claim 5, wherein the determining the dielectric loss tangent value of the power distribution network under the detection current of the injected target frequency according to the parallel impedance of the capacitance of the power distribution network arc suppression coil inductance to the secondary side of PT and the grounding transition resistance is specifically comprising:
according to the formulaDetermining the loss tangent value of the power distribution network to the ground under the current signal of the injection target frequency; wherein omega 0 Is to inject a current source with a frequency f 0 Corresponding angular frequency, delta f0 Is Z f02 Residual angle of impedance angle, I n Is a single-phase grounding transition resistance.
7. The method for fault awareness of a resonant ground system of a power distribution network of claim 6, wherein determining a fault condition of the resonant ground system of the power distribution network based on a comparison between a dielectric loss tangent to ground and a threshold value comprises:
determining a dielectric loss tangent to ground at a detected current at a target frequency;
if the dielectric loss tangent value to the ground is larger than the threshold value, the resonant grounding system of the power distribution network has a grounding fault;
and if the dielectric loss tangent value to the ground is smaller than or equal to the threshold value, the power distribution network resonance grounding system normally operates.
8. A fault sensing device for a resonant ground system of a power distribution network, the device comprising:
an acquisition unit configured to acquire a target frequency of the detection current;
the control unit is used for determining reference power distribution network impedance under the detection current of the target frequency and grounding power distribution network impedance under the detection current of the target frequency when the system is in single-phase grounding during normal operation of the power distribution network through injecting the detection current of the target frequency;
the control unit is also used for determining the parallel impedance of the capacitor of the arc suppression coil inductance of the power distribution network, which is converted to the capacitance of the PT secondary side and the grounding transition resistance, to the ground distributed capacitance according to the reference power distribution network impedance and the grounding power distribution network impedance;
the control unit is further used for determining the dielectric loss tangent value of the distribution network to the ground under the detection current of the injection target frequency according to the parallel impedance of the capacitance of the distribution network arc suppression coil inductance to the PT secondary side and the grounding transition resistance;
and the fault judging unit is used for determining the fault state of the resonant grounding system of the power distribution network according to the comparison relation between the dielectric loss tangent value to the ground and the threshold value.
9. A computer device comprising a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the steps of the method of any of claims 1 to 7.
10. A computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of the method of any one of claims 1 to 7.
CN202310576319.8A 2023-05-19 2023-05-19 Fault sensing method, device, equipment and medium of power distribution network resonance grounding system Pending CN116736033A (en)

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