CN111682513A - Power distribution network fault protection method and system based on system resistance-capacitance ratio - Google Patents
Power distribution network fault protection method and system based on system resistance-capacitance ratio Download PDFInfo
- Publication number
- CN111682513A CN111682513A CN202010528132.7A CN202010528132A CN111682513A CN 111682513 A CN111682513 A CN 111682513A CN 202010528132 A CN202010528132 A CN 202010528132A CN 111682513 A CN111682513 A CN 111682513A
- Authority
- CN
- China
- Prior art keywords
- resistance
- capacitance ratio
- line
- zero
- fault
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 35
- 230000007935 neutral effect Effects 0.000 claims abstract description 43
- 230000001360 synchronised effect Effects 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 3
- 230000007704 transition Effects 0.000 description 14
- 238000010586 diagram Methods 0.000 description 4
- 230000001629 suppression Effects 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
Images
Classifications
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
The application discloses a power distribution network fault protection method and system based on system resistance-capacitance ratio, wherein the method comprises the following steps: when a single-phase earth fault occurs to a neutral point through a small-resistance earth system, firstly, calculating zero-sequence current of a non-fault line and zero-sequence current of a fault line, then unifying formats of the zero-sequence voltage and the zero-sequence current of each feeder line, calculating a resistance-capacitance ratio coefficient of each feeder line by using a formula, then calculating a resistance-capacitance ratio coefficient threshold value by using the formula according to the total earth-capacitance current level of the system, and finally, adopting zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio to select the line. The system comprises: the circuit comprises a first zero sequence current calculation module, a second zero sequence current calculation module, a format unification module, a resistance-capacitance ratio coefficient calculation module, a resistance-capacitance ratio coefficient threshold value calculation module and a line selection module. Through the method and the device, the reliability and the safety of ground fault protection can be effectively improved, and the safety and the stability of operation of the power distribution network are further improved.
Description
Technical Field
The application relates to the technical field of relay protection of power distribution networks, in particular to a power distribution network fault protection method and system based on system resistance-capacitance ratio.
Background
In an urban power distribution network, a power distribution network with a neutral point grounded through a small resistor is widely applied. Particularly, with the enlargement of the scale of the power grid, the capacitance current of the system to the ground is continuously increased, so that the compensation capacity of the arc suppression coil is insufficient, and because some transformer substations have difficulty in expanding the arc suppression coil, a neutral point is gradually changed into a mode that the neutral point is grounded through a small resistor through the arc suppression coil system. With the application of a mode that a neutral point in a power distribution network is grounded through a small resistor, when a single-phase ground fault occurs in the power distribution network with the grounding mode, how to perform power distribution protection is an important technical problem.
When the existing power distribution network with a neutral point grounded through a small resistor has a ground fault, the zero-sequence overcurrent protection is usually adopted to quickly remove the ground fault. Specifically, the neutral point is a 10kV system through a small-resistance grounding system, when a single-phase grounding fault occurs, the fault point and the small-resistance of the neutral point form a zero-sequence current path to form a large fault current, and therefore the grounding fault is cut off rapidly. And the current protection method is suitable for the ground fault with the transition resistance below 100 omega.
However, in the current power distribution protection method, the zero-sequence overcurrent protection can only reflect the ground fault below the transition resistance 100 Ω at the fixed value setting timing, when a high-resistance ground fault above 100 Ω occurs, for example, the transition resistance is within the range of 200-. Therefore, in the current zero sequence current protection method in the power distribution network, the accuracy and reliability of ground fault detection are not high enough, so that the protection efficiency is low, the safety is low, and the safety and the stability of the power distribution network operation are affected.
Disclosure of Invention
The application provides a power distribution network fault protection method and system based on a system resistance-capacitance ratio, and aims to solve the problems that in the prior art, the power distribution network fault protection efficiency is low, the safety is low, and the running safety and stability of the power distribution network are low.
In order to solve the technical problem, the embodiment of the application discloses the following technical scheme:
a fault protection method for a power distribution network based on system resistance-capacitance ratio is disclosed, wherein the power distribution network adopts a mode that a neutral point is grounded through a small resistor, and the method comprises the following steps:
when a single-phase earth fault occurs to a neutral point through a small-resistance earth system, calculating zero-sequence current of a non-fault line;
calculating zero sequence current of a fault line;
using formulas
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Is the real part, representing the resistive part of the line, XCOIs the imaginary part, representing the capacitive part of the line;
according to the proportional relation between resistive current and capacitive current when the neutral point has single-phase earth fault via small-resistance earthing system, the formula is used
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient;
according to the total capacitance-to-ground current level of the system, using a formula
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, wherein KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrA neutral point small resistance;
and selecting the line by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the threshold value of the resistance-capacitance ratio coefficient.
Optionally, the method for calculating the zero sequence current of the non-fault line includes:
using formulas
Calculating to obtain the sum of three relative earth capacitance currents, wherein n represents a non-fault line,
is not failedZero sequence current of the line, j is an imaginary number unit, omega is a power frequency synchronous angular velocity, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage;
and taking the sum of the three-phase capacitance-to-ground currents as the zero-sequence current of the non-fault line.
Optionally, the calculating the zero sequence current of the fault line specifically includes:
according to kirchhoff's law, using the formula
And calculating the zero sequence current of the fault line, wherein,
zero sequence current of faulty line, sigma C is the sum of system earth capacitances, C4Is the capacitance to ground of the faulty line.
Optionally, the formula is used according to a proportional relation between resistive current and capacitive current when a single-phase earth fault occurs in the system with the neutral point grounded through the small resistor
Calculating the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, including:
the resistance-capacitance ratio coefficient of the non-fault line is 0;
the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
Optionally, the zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio is as follows:
A system resistance-to-capacitance ratio based fault protection system for a power distribution network, the system comprising:
the first zero sequence current calculation module is used for calculating the zero sequence current of a non-fault line when a single-phase earth fault occurs to a neutral point through a small-resistance earth system;
the second zero sequence current calculation module is used for calculating the zero sequence current of a fault line when a single-phase earth fault occurs to a neutral point through a small-resistance earth system;
a format unification module for utilizing the formula
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Is the real part, representing the resistive part of the line, XCOIs the imaginary part, representing the capacitive part of the line;
a resistance-capacitance ratio coefficient calculating module for calculating the proportional relation between the resistive current and the capacitive current according to the formula when the neutral point has single-phase earth fault via the small-resistance earth system
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient;
a module for calculating threshold value of resistance-capacitance ratio coefficient, which is used for utilizing a formula according to the total current level of the ground capacitor of the system
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, wherein KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrIs small in neutral pointA resistance;
and the line selection module is used for selecting lines by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value.
Optionally, the first zero sequence current calculation module is configured to utilize a formula
Calculating to obtain the sum of three phase-to-ground capacitance currents, and taking the sum of the three phase-to-ground capacitance currents as the zero sequence current of the non-fault line, wherein n represents the non-fault line,
is zero-sequence current of non-fault line, j is imaginary unit, omega is power frequency synchronous angular speed, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage.
Optionally, the second zero-sequence current calculating module is configured to utilize a formula according to kirchhoff's law
And calculating the zero sequence current of the fault line, wherein,
zero sequence current of faulty line, sigma C is the sum of system earth capacitances, C4Is the capacitance to ground of the faulty line.
Optionally, the resistance-capacitance ratio coefficient calculating module includes:
a first resistance-capacitance ratio coefficient calculation unit for using the formula
Calculating to obtain non-fault in power distribution networkThe resistance-capacitance ratio coefficient of the line and the resistance-capacitance ratio coefficient of the non-fault line are 0;
a second resistance-capacitance ratio coefficient calculating unit for using the formula
And calculating to obtain the resistance-capacitance ratio coefficient of the fault line in the power distribution network, wherein the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
Optionally, the line selection module is configured to adopt a zero-sequence overcurrent protection criterion according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value:
selecting lines, wherein, 3I0.setZero-current setting value, K, for zero-sequence overcurrent protection0.setIs the threshold value of the resistance-capacitance ratio coefficient.
The technical scheme provided by the embodiment of the application can have the following beneficial effects:
the method comprises the steps of firstly calculating zero sequence current of a non-fault line and zero sequence current of a fault line when a neutral point is in single-phase earth fault through a small-resistance earth system, then carrying out format unification on the zero sequence voltage and the zero sequence current of each feeder line by using a format unification formula, secondly calculating a resistance-capacitance ratio coefficient of each feeder line by using the formula according to a proportional relation between the resistive current and the capacitive current when the earth fault occurs, and then calculating a resistance-capacitance ratio coefficient of each feeder line by using the formula according to the total earth-capacitance current level of the system
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, and finally adopting a method based on the resistance-capacitance ratio coefficient and the threshold value of the resistance-capacitance ratioAnd selecting the line according to the zero-sequence overcurrent protection criterion of the resistance-capacitance ratio. In the embodiment, the zero sequence currents of the non-fault line and the fault line during fault are collected and unified in format, the resistance-capacitance ratio coefficient is calculated, then the line selection is carried out according to the zero sequence overcurrent protection criterion based on the resistance-capacitance ratio coefficient, and finally the overcurrent protection of the power distribution network is realized. Because the difference between the resistance-capacitance ratio coefficient of the fault line and the resistance-capacitance ratio coefficient of the non-fault line is obvious in the embodiment, the line selection is carried out according to the zero-sequence overcurrent protection criterion determined by the resistance-capacitance ratio coefficient, the overcurrent protection can be realized more quickly and accurately, and the protection efficiency and the safety of the power distribution network fault are improved. Moreover, because the variable of the transition resistance is not in the resistance-capacitance ratio coefficient, the method is not influenced by the transition resistance, when the transition resistance is in a high resistance state such as 200-500 omega, a fault can be detected in time and a fault alarm is sent out, so that the protection efficiency of the fault of the power distribution network is favorably improved, and the operation safety of the power distribution network is improved. And the resistance-capacitance ratio coefficient has no transition resistance, so that the method has better applicability to single-phase metal ground faults and high-resistance ground faults, and finally, the method has wider application range and is convenient to popularize and use. In addition, in the calculation of the resistance-capacitance ratio coefficient in this embodiment, taking an absolute value, whether the polarities of a CT (Current transformer) and a PT (Potential transformer) are reversed or not does not affect the correctness of the calculation result, that is, taking the resistance-capacitance ratio coefficient condition as a locking condition of zero-sequence overcurrent protection can avoid the influence of reversed polarity of a special zero-sequence CT, and this method is favorable for improving the reliability and safety of ground fault protection, and further improves the safety and stability of the operation of the power distribution network.
The application also provides a distribution network fault protection system based on system resistance-capacitance ratio, and the system mainly comprises: the circuit comprises a first zero sequence current calculation module, a second zero sequence current calculation module, a format unification module, a resistance-capacitance ratio coefficient calculation module, a resistance-capacitance ratio coefficient threshold value calculation module and a line selection module. The method comprises the steps of providing parameters for calculating a resistance-capacitance ratio coefficient through a first zero-sequence current calculating module, a second zero-sequence current calculating module and a format unifying module, calculating the resistance-capacitance ratio coefficient according to the resistance-capacitance ratio coefficient calculating module, calculating a resistance-capacitance ratio coefficient threshold value according to the total ground capacitance current level of a system, and finally selecting lines through a line selecting module according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value and adopting a zero-sequence current protection criterion based on the resistance-capacitance ratio to realize the fault protection of the power distribution network. The resistance-capacitance ratio coefficient in the embodiment has no variable of transition resistance, and the resistance-capacitance ratio coefficient calculation module is arranged, so that the system in the embodiment is not affected by the transition resistance, when the transition resistance is in a high resistance state such as 200-500 omega, the system can timely detect a fault and send out a fault alarm, the protection efficiency of the fault of the power distribution network is favorably improved, and the operation safety of the power distribution network is improved. And the parameter of the transition resistance is not arranged in the resistance-capacitance ratio coefficient calculation module, so that the system has better applicability to single-phase metal ground faults and high-resistance ground faults, and is favorable for popularization and use of the system. In addition, in this embodiment, the absolute value of the resistance-capacitance ratio coefficient calculated by the resistance-capacitance ratio coefficient calculation module is used as the locking condition of the zero-sequence overcurrent protection, and the influence of reverse polarity of the special zero-sequence CT can be avoided.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flowchart of a power distribution network fault protection method based on a system resistance-capacitance ratio according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a single-phase earth fault of a system with a neutral point earthed via a small resistor;
fig. 3 is a schematic structural diagram of a power distribution network fault protection system based on a system resistance-capacitance ratio according to an embodiment of the present application.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
For a better understanding of the present application, embodiments of the present application are explained in detail below with reference to the accompanying drawings.
Example one
Referring to fig. 1, fig. 1 is a schematic flowchart of a power distribution network fault protection method based on a system resistance-capacitance ratio according to an embodiment of the present application. As can be seen from fig. 1, the method for protecting a power distribution network from a fault based on a system resistance-capacitance ratio in this embodiment mainly includes the following steps:
s1: when the neutral point has single-phase earth fault through a small resistance earthing system, the zero sequence current of the non-fault line is calculated.
The operations in this embodiment are performed after a single-phase earth fault occurs in the neutral point via the low-resistance earth system. Specifically, step S1 includes:
s11: using formulas
And calculating to obtain the sum of the three relative earth capacitance currents.
Where n represents a non-faulty line,
is zero-sequence current of non-fault line, j is imaginary unit, omega is power frequency synchronous angular speed, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage. A schematic diagram of a single-phase ground fault of a system in which a neutral point is grounded via a small resistor in the present embodiment can be seen in fig. 2. As can be seen from fig. 2, n is 1, 2, and 3, and represents 3 non-faulty lines.
S12: and taking the sum of the three-phase capacitance-to-ground currents as the zero-sequence current of the non-fault line.
The neutral point requires the 10kV part of the load side transformer to be in a triangular connection mode through a small resistance grounding system, so that the sum of three-phase load currents of each line is zero, and for a non-fault line, the zero-sequence current is calculated by calculating the sum of three-phase capacitance-to-ground currents in this embodiment, so that the zero-sequence current of the non-fault cable can be accurately and quickly obtained.
S2: and calculating the zero sequence current of the fault line.
That is, when a single-phase earth fault occurs in the neutral point via the low-resistance earth system, the zero-sequence current of the fault line is calculated. Specifically, step S2 may employ the following method:
according to kirchhoff's law, using the formula
And calculating to obtain the zero sequence current of the fault line. Wherein,
zero sequence current for the faulty line, i.e. zero sequence current for line 4 in fig. 2, Σ C being the sum of the system capacitances to ground, C4Is the capacitance to ground of the faulty line. Zero sequence voltage U0Will vary with the location of the fault point due to the effect of the pressure dropIn response, it is changed to be maximum at the occurrence of a metallic short-circuit ground fault at the bus, approximately at the phase voltage.
From the above formula
It can be known that, for a faulty line, according to kirchhoff's law, zero-sequence currents of all non-faulty lines flow, and zero-sequence currents of a neutral point small resistor flow, and the zero-sequence currents flowing through the neutral point small resistor are
Wherein the minus sign indicates: the zero sequence currents of the faulted line and the non-faulted line and the neutral point small resistor are kept to be 0 in total.
S3: using formulas
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Is the real part, representing the resistive part of the line, XCOIs the imaginary part, representing the capacitive part of the line.
That is, the formulas in steps S11 and S2 are formally changed and converted into calculations
The expression represents that the zero-sequence current of the fault line and the non-fault line are different in composition. Using formulas
After unifying the format, the calculation result of the non-fault line is
The calculation result of the faulty line is
In practical application, there may be the case that the polarities of PT and CT are reversed, and R is corresponding to the reversed polarity0、XC0Can make it possible toPositive or negative, for non-faulty lines, R0Theoretically 0, but actually affected by the line distribution parameters, the actual value is not 0, but the value is small.
With continued reference to fig. 1, after formatting the zero-sequence voltage and the zero-sequence current of each feeder line in the power distribution network, step S4 is executed: according to the proportional relation between resistive current and capacitive current when the neutral point has single-phase earth fault via small-resistance earthing system, the formula is used
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient.
In particular, using formulas
The calculation of the resistance-capacitance ratio coefficient of each feeder line in the power distribution network mainly comprises the following steps: and calculating the resistance-capacitance ratio coefficient of the non-fault line and the resistance-capacitance ratio coefficient of the fault line.
According to the formula
Calculating to obtain that the resistance-capacitance ratio coefficient of the non-fault line is 0, and the value is a theoretical value; the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
Wherein,
is a constant that depends on the system parameters of the distribution network.
From the above calculation results, when a single-phase earth fault occurs in a system with a neutral point grounded through a small resistor, the fault line has a characteristic that the resistance-capacitance ratio coefficient is larger than a system constant, but the resistance-capacitance ratio coefficient of the non-fault line is about 0, and the characteristic has obvious characteristicDistinguishing degree; and the formula of the resistance-capacitance ratio coefficient of the fault line
The variable of the transition resistance is not involved, so that the method in the embodiment meets the condition no matter how large the transition resistance is when the transition resistance earth fault occurs, and therefore, the method in the embodiment can be applied to the conditions of single-phase metallic earth and high-resistance earth, the application range is wider, and the fault protection is more reliable.
S5: according to the total capacitance-to-ground current level of the system, using a formula
And calculating to obtain a threshold value of the resistance-capacitance ratio coefficient.
Wherein, KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrIs a neutral point small resistance. Reliability factor K in this exampleKRated phase voltage U with value of 0.8 and 10kV systemph.nThe value was 5.77 kV.
After the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value are obtained, step S6 is executed: and selecting the line by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the threshold value of the resistance-capacitance ratio coefficient.
Specifically, in this embodiment, the zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio is as follows:
therein, 3I0.setZero-current setting value, K, for zero-sequence overcurrent protection0.setIs the threshold value of the resistance-capacitance ratio coefficient.
Example two
Referring to fig. 3 on the basis of the embodiments shown in fig. 1 and fig. 2, fig. 3 is a schematic structural diagram of a power distribution network fault protection system based on a system resistance-capacitance ratio according to an embodiment of the present application. As can be seen from fig. 3, the system fault protection system based on the system resistance-capacitance ratio in this embodiment mainly includes: the circuit comprises a first zero sequence current calculation module, a second zero sequence current calculation module, a format unification module, a resistance-capacitance ratio coefficient calculation module, a resistance-capacitance ratio coefficient threshold value calculation module and a line selection module.
The first zero sequence current calculation module is used for calculating the zero sequence current of a non-fault line when a single-phase earth fault occurs to a neutral point through a small-resistance earth system. And the second zero sequence current calculating module is used for calculating the zero sequence current of the fault line when the neutral point has single-phase earth fault through the small-resistance earth system. A format unification module for utilizing the formula
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Representing the resistive part of the zero-sequence voltage and current as the real part, XCOAnd the imaginary part represents the capacitive part of the zero-sequence voltage and the zero-sequence current. A resistance-capacitance ratio coefficient calculating module for calculating the proportional relation between the resistive current and the capacitive current according to the formula when the neutral point has single-phase earth fault via the small-resistance earth system
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient. A module for calculating threshold value of resistance-capacitance ratio coefficient, which is used for utilizing a formula according to the total current level of the ground capacitor of the system
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, wherein KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrIs a neutral point small resistance. And the line selection module is used for selecting lines by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the threshold value of the resistance-capacitance ratio coefficient.
Further, in this embodiment, the first zero-sequence current calculation module mainly uses a formula
And calculating to obtain the sum of the three-phase earth capacitance currents, and taking the sum of the three-phase earth capacitance currents as the zero sequence current of the non-fault line. Where n represents a non-faulty line,
is zero-sequence current of non-fault line, j is imaginary unit, omega is power frequency synchronous angular speed, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage.
The second zero sequence current calculation module utilizes a formula according to kirchhoff's law
And calculating to obtain the zero sequence current of the fault line. Wherein,
zero sequence current of faulty line, sigma C is the sum of system earth capacitances, C4Is the capacitance to ground of the faulty line.
The resistance-capacitance ratio coefficient calculation module comprises: a first resistance-to-capacitance ratio coefficient calculating unit and a second resistance-to-capacitance ratio coefficient calculating unit. Wherein the first resistance-capacitance ratio coefficient calculating unit is used for utilizing a formula
And calculating to obtain the resistance-capacitance ratio coefficient of the non-fault line in the power distribution network, wherein the resistance-capacitance ratio coefficient of the non-fault line is 0. A second resistance-capacitance ratio coefficient calculating unit for using the formula
And calculating to obtain the resistance-capacitance ratio coefficient of the fault line in the power distribution network, wherein the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
The line selection module adopts a zero-sequence overcurrent protection criterion according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value:
and (6) selecting the line. Therein, 3I0.setZero-current setting value, K, for zero-sequence overcurrent protection0.setIs the threshold value of the resistance-capacitance ratio coefficient.
In this embodiment, the working principle and the working method of the power distribution network fault protection system based on the system resistance-capacitance ratio have been explained in detail in the embodiments shown in fig. 1 and fig. 2, and the two embodiments may be referred to each other, and are not described herein again.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A fault protection method for a power distribution network based on a system resistance-capacitance ratio is characterized in that the power distribution network adopts a mode that a neutral point is grounded through a small resistor, and the method comprises the following steps:
when a single-phase earth fault occurs to a neutral point through a small-resistance earth system, calculating zero-sequence current of a non-fault line;
calculating zero sequence current of a fault line;
using formulas
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Is the real part, representing the resistive part of the line, XCOIs the imaginary part, representing the capacitive part of the line;
according to the proportional relation between resistive current and capacitive current when the neutral point has single-phase earth fault via small-resistance earthing system, the formula is used
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient;
according to the total capacitance-to-ground current level of the system, using a formula
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, wherein KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrA neutral point small resistance;
and selecting the line by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the threshold value of the resistance-capacitance ratio coefficient.
2. The method for fault protection of the power distribution network based on the system resistance-capacitance ratio is characterized in that the method for calculating the zero sequence current of the non-fault line comprises the following steps:
using formulas
Calculating to obtain the sum of three relative earth capacitance currents, wherein n represents a non-fault line,
is zero-sequence current of non-fault line, j is imaginary unit, omega is power frequency synchronous angular speed, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage;
and taking the sum of the three-phase capacitance-to-ground currents as the zero-sequence current of the non-fault line.
3. The method according to claim 1, wherein the calculating of the zero sequence current of the fault line is specifically:
according to kirchhoff's law, using the formula
And calculating the zero sequence current of the fault line, wherein,
zero sequence current of faulty line, sigma C is the sum of system earth capacitances, C4Is the capacitance to ground of the faulty line.
4. The method according to claim 1, wherein the formula is used according to a proportional relationship between resistive current and capacitive current when a single-phase ground fault occurs in the system with a neutral point grounded via a small resistor, and the system resistance-capacitance ratio-based power distribution network fault protection method is based on
Calculating the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, including:
the resistance-capacitance ratio coefficient of the non-fault line is 0;
the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
5. The power distribution network fault protection method based on the system resistance-capacitance ratio as claimed in claim 1, wherein the zero sequence overcurrent protection criterion based on the resistance-capacitance ratio is:
6. A system resistance-capacitance ratio based fault protection system for a power distribution network, the system comprising:
the first zero sequence current calculation module is used for calculating the zero sequence current of a non-fault line when a single-phase earth fault occurs to a neutral point through a small-resistance earth system;
the second zero sequence current calculation module is used for calculating the zero sequence current of a fault line when a single-phase earth fault occurs to a neutral point through a small-resistance earth system;
a format unification module for utilizing the formula
Unifying the format of the zero sequence voltage and the zero sequence current of each feeder line in the power distribution network, wherein R0Is the real part, representing the resistive part of the line, XCOIs the imaginary part, representing the capacitive part of the line;
a resistance-capacitance ratio coefficient calculating module for calculating the proportional relation between the resistive current and the capacitive current according to the formula when the neutral point has single-phase earth fault via the small-resistance earth system
Calculating to obtain the resistance-capacitance ratio coefficient of each feeder line in the power distribution network, wherein KRCOIs a resistance-to-capacitance ratio coefficient;
a module for calculating threshold value of resistance-capacitance ratio coefficient, which is used for utilizing a formula according to the total current level of the ground capacitor of the system
Calculating to obtain threshold value of resistance-capacitance ratio coefficient, wherein KkFor a reliability factor, Uph.nFor rated phase voltage, Σ ICFor the total system capacitance-to-ground current level, RrA neutral point small resistance;
and the line selection module is used for selecting lines by adopting a zero-sequence overcurrent protection criterion based on the resistance-capacitance ratio according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value.
7. The system of claim 6, wherein the first zero sequence current calculation module is configured to use a formula
Calculating to obtain the sum of three phase-to-ground capacitance currents, and taking the sum of the three phase-to-ground capacitance currents as the zero sequence current of the non-fault line, wherein n represents the non-fault line,
is zero-sequence current of non-fault line, j is imaginary unit, omega is power frequency synchronous angular speed, CnFor the capacitance to ground of each non-faulty line,
is a three-phase voltage, and the voltage of the three-phase voltage,
is a zero sequence voltage.
8. The system of claim 6, wherein the second zero sequence current calculation module is configured to use a formula according to kirchhoff's law
And calculating the zero sequence current of the fault line, wherein,
zero sequence current of faulty line, sigma C is the sum of system earth capacitances, C4Is the capacitance to ground of the faulty line.
9. The system of claim 6, wherein the RC coefficient calculation module comprises:
a first resistance-capacitance ratio coefficient calculation unit for using the formula
Calculating the resistance-capacitance ratio coefficient of a non-fault line in the power distribution network, wherein the resistance-capacitance ratio coefficient of the non-fault line is 0;
a second resistance-capacitance ratio coefficient calculating unit for using the formula
And calculating to obtain the resistance-capacitance ratio coefficient of the fault line in the power distribution network, wherein the resistance-capacitance ratio coefficient of the fault line is as follows:
and is
10. A power distribution network fault protection based on system resistance-to-capacitance ratio as claimed in any one of claims 6-9The line selection module is used for adopting a zero-sequence overcurrent protection criterion according to the resistance-capacitance ratio coefficient and the resistance-capacitance ratio coefficient threshold value:
selecting lines, wherein, 3I0.setZero-current setting value, K, for zero-sequence overcurrent protection0.setIs the threshold value of the resistance-capacitance ratio coefficient.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010528132.7A CN111682513A (en) | 2020-06-11 | 2020-06-11 | Power distribution network fault protection method and system based on system resistance-capacitance ratio |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010528132.7A CN111682513A (en) | 2020-06-11 | 2020-06-11 | Power distribution network fault protection method and system based on system resistance-capacitance ratio |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111682513A true CN111682513A (en) | 2020-09-18 |
Family
ID=72454552
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010528132.7A Pending CN111682513A (en) | 2020-06-11 | 2020-06-11 | Power distribution network fault protection method and system based on system resistance-capacitance ratio |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111682513A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975657A (en) * | 2019-04-04 | 2019-07-05 | 辽宁工程技术大学 | Single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value |
| CN110535116A (en) * | 2019-09-10 | 2019-12-03 | 北京华电瑞通电力工程技术有限公司 | A kind of arc extinction cabinet and small current neutral grounding system |
| CN110635452A (en) * | 2019-09-04 | 2019-12-31 | 南京南瑞继保电气有限公司 | Zero-sequence overcurrent protection method locked through resistance-capacitance ratio |
-
2020
- 2020-06-11 CN CN202010528132.7A patent/CN111682513A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975657A (en) * | 2019-04-04 | 2019-07-05 | 辽宁工程技术大学 | Single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value |
| CN110635452A (en) * | 2019-09-04 | 2019-12-31 | 南京南瑞继保电气有限公司 | Zero-sequence overcurrent protection method locked through resistance-capacitance ratio |
| CN110535116A (en) * | 2019-09-10 | 2019-12-03 | 北京华电瑞通电力工程技术有限公司 | A kind of arc extinction cabinet and small current neutral grounding system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102074950B (en) | Distribution network ground fault arc extinction and protection method | |
| Jena et al. | A positive-sequence directional relaying algorithm for series-compensated line | |
| CN108594071B (en) | Single-phase earth fault detection method for neutral point small-resistance earth distribution network | |
| CN103245879B (en) | Based on the low current grounding localization method in transient reactive power direction | |
| CN110988740B (en) | Single-phase earth fault detection method suitable for neutral point small-resistance earth distribution network | |
| CN103474980B (en) | A kind of power distribution network single-phase ground protection method based on transient power direction | |
| CN110021918B (en) | Single-phase short-circuit protection method for resistance-grounded power distribution network based on zero-sequence current ratio | |
| CN105842583A (en) | Distribution network single-phase grounding section positioning method based on fault phase voltage and current abrupt change | |
| Akke et al. | Some improvements in the three-phase differential equation algorithm for fast transmission line protection | |
| CN107508265B (en) | Small resistance grounding system high resistance earthing protecting method and system | |
| CN113484672B (en) | Small-resistance grounding system single-phase grounding fault protection method based on ground wire current | |
| CN107516878B (en) | Intermittent high resistance earthing protecting method and system | |
| CN106655121A (en) | Low-impedance adaptive protection method of micro-grid bus | |
| CN111948569A (en) | Intermittent arc light grounding fault detection method based on volt-ampere-like characteristics | |
| CN109541369A (en) | A kind of power grid one-way earth fault detection system and its detection method | |
| Abd el-Ghany et al. | A faulted side identification scheme-based integrated distance protection for series-compensated transmission lines | |
| CN114280348B (en) | Small-current ground fault detection method based on active power abrupt change | |
| CN201197073Y (en) | Ground flashover detection circuit for magnetic controlled shunt reactor exciting winding casing tube | |
| CN111900695B (en) | Single-phase earth fault removing method and device | |
| CN111682513A (en) | Power distribution network fault protection method and system based on system resistance-capacitance ratio | |
| CN112578310B (en) | Detection method for single-phase grounding line selection tripping function | |
| CN113949049B (en) | Self-adaptive single-phase reclosing method for 220kV power transmission line | |
| Ren et al. | Research on the countermeasures of the single-phase-to-earth faults in flexibly grounded distribution networks | |
| CN110896214B (en) | Phase selection method of active intervention type arc suppression device | |
| CN109521325B (en) | Calculation method for positioning distribution line fault by using main oscillation frequency |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20200918 |