CN114518506B - Method and system for detecting fault of direct-current transmission line - Google Patents

Method and system for detecting fault of direct-current transmission line Download PDF

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CN114518506B
CN114518506B CN202111303570.4A CN202111303570A CN114518506B CN 114518506 B CN114518506 B CN 114518506B CN 202111303570 A CN202111303570 A CN 202111303570A CN 114518506 B CN114518506 B CN 114518506B
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line
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modulus
data
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CN114518506A (en
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束洪春
王锐
杨竞及
李文龙
唐玉涛
马海心
薄志谦
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Kunming University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • 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
    • G01R31/088—Aspects of digital computing
    • 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
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Abstract

The invention relates to a fault detection method and system for a direct current transmission line, and belongs to the field of relay protection of power systems. Firstly, acquiring single-end electric quantity data of a direct-current line in real time to obtain a space modulus signal of the single-end electric quantity; calculating the cumulant of the power transformation of the space modulus signal variation of the single-end electric quantity in a set time window, and constructing a fault detection signal; and continuously judging at least three adjacent fault detection signals, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continuously collect and calculate the single-end electric quantity, and if so, sending a protection starting signal for the line fault. The invention also provides a system for detecting the fault of the direct current line. The method provided by the invention can quickly and reliably detect the line fault, and has sensitivity, reliability and quick action.

Description

Method and system for detecting fault of direct-current transmission line
Technical Field
The invention relates to a fault detection method and system for a direct current transmission line, and belongs to the field of relay protection of power systems.
Background
With the rapid development of economy in China, alternating current transmission can not meet the electricity consumption requirements of residents in China. Because the energy distribution and the power load demand distribution of China are in the opposite phase, the direct-current transmission line becomes the main direction of the power transmission development of China in the future by virtue of the advantages of large capacity, long transmission distance, convenience in power grid interconnection and the like. When a direct current transmission line breaks down, the direct current transmission system is locked due to protection misoperation, so that the direct current transmission system is unnecessarily stopped. In addition, the direct current lines are mostly arranged in remote mountainous areas, the natural environment is severe, and the overhaul is very inconvenient, so that the direct current transmission line fault detection system has high requirements. Therefore, the fault detection capability for the direct current power transmission is improved, which is beneficial to improving the stability of the direct current power transmission system.
The existing direct current transmission protection method mainly comprises traveling wave protection, transient quantity protection, differential undervoltage protection, low-voltage protection and pilot current differential protection. The traveling wave protection is the main protection of the direct current line, and has the advantages of quickly and accurately determining a fault line; differential under-voltage protection is not only main protection of a direct-current line, but also backup protection of traveling wave protection, and has the advantages that compared with traveling wave protection, the differential under-voltage protection is low in protection speed but high in sensitivity and reliability, but the technical problem that protection can be mistakenly operated in high-resistance faults exists in both the differential under-voltage protection and the traveling wave protection is not solved. The low-voltage protection is backup protection of traveling wave protection and differential undervoltage protection, and the protection is divided into line low-voltage protection and pole-controlled line voltage protection. The pilot differential protection is backup protection of a direct-current transmission line, and has the advantages that high-resistance faults can be reliably cut off, but the problem that any voltage change can cause protection misoperation due to the fact that capacitance current is not considered is not solved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method and a system for detecting a direct current transmission line, thereby solving the problem.
The technical scheme of the invention is as follows: a method for detecting faults of a direct-current transmission line includes the steps of firstly collecting single-end electric quantity data of a direct-current line in real time, obtaining cumulant of power transformation of space modulus signal variation of the single-end electric quantity in a set time window after a series of calculations, constructing fault detection signals according to the cumulant of power transformation, and comparing the signals with a set detection threshold value to obtain line faults or normal operation results of a system.
The method comprises the following specific steps:
step 1: collecting single-end electric quantity data of a direct-current line to obtain a space modulus signal C of the single-end electric quantityΣ。
Step 2: power transformation C for obtaining space modulus signal variation delta C of single-end electric quantitymbhThe cumulative quantity of N in the set time window is used to construct fault detection signal CLJ。
Step 3: and continuously judging fault detection signals of at least three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continue collecting and calculating, and if so, judging that the line has a fault and sending a protection starting signal.
The Step1 comprises the following specific steps:
step1.1: the method comprises the steps of collecting single-ended electrical quantity data of a direct-current line in real time, wherein the single end refers to any end of a direct-current transmission line, namely a first end or a second end of the line; the real-time acquisition of the single-ended electrical quantity data of the direct-current line refers to the real-time acquisition of the voltage quantity and the current quantity U of the positive pole and the negative pole of the direct-current transmission line+、U-、I+、I-。
Step1.2: spatial modulus signal CΣThe method is obtained through phase-mode conversion of single-end electric quantity data, and is shown in a formula (1):
Figure GDA0003530044950000021
in the formula (1), u1(n)、i1And (n) respectively represents the numerical values of the voltage and the current of the nth sampling point.
Step1.3: selecting a spatial modulus signal u1、i1As fault characteristic valueCΣAs shown in formula (2):
CΣ(n)＝u1(n)、CΣ(n)＝i1(n) (2)
in the formula (2), CΣ(n) represents the nth spatial modulus semaphore.
The Step2 comprises the following specific steps:
step 2.1: calculating space modulus signal variation C of single-end electric quantityΣAs shown in formula (3):
ΔC(n)＝CΣ(n+1)-CΣ(n) (3)
in the formula (3), Δ C (n) represents a difference calculation value of the nth sampling point, CΣ(n +1) represents the (n +1) th spatial modulus semaphore.
Step 2.2: power transformation C for calculating space modulus signal variation of single-ended electric quantitymbhAs shown in formula (4):
Cmbh(n)＝(ΔC(n))α (4)
in the formula (4), Cmbh(n) represents a power conversion value of the difference calculation value of the nth sampling point, and alpha is an exponential operation value, and the value depends on the actual line condition.
Step2.3: multiplying according to different sampling periods and an integral time window to obtain a set sampling number N, as shown in formula (5):
Figure GDA0003530044950000022
in the formula (5), f is the sampling frequency,
Figure GDA0003530044950000031
is a sampling period, t is an integral time window, and N is the sampling times; in the same integration time, the larger the sampling frequency is, the more the sampling times are, the better the obtained waveform effect is, and under the condition of permission, the larger the set time window is, the better the anti-interference performance is.
Step2.4: and (3) performing integral change on the power transformation of the space modulus change amount in a set time window to obtain an accumulated amount, and constructing a fault detection signal according to the accumulated amount, wherein the formula (6) is as follows:
Figure GDA0003530044950000032
in formula (6), CLJ(k) Representing the kth fault detection signal.
The Step3 comprises the following specific steps:
step3.1: after receiving the detection signal sent by the numerical calculation module, the detection system selects three consecutive detection signals CLJ(k)、CLJ(k+1)、CLJ(k+2)。
Wherein, CLJ(k) Denotes the kth detection signal, CLJ(k +1) denotes the (k +1) th detection signal, CLJ(k +2) denotes the (k +2) th detection signal.
Step3.2: comparing the three detection signals selected by the system with a set detection threshold value, and judging whether the subtraction of the two values is 0 or not, as shown in formula (7):
Figure GDA0003530044950000033
in the formula (7), CedA detection threshold value representing the rating of the line, the value of which is set according to the actual line conditions.
Step3.3: if the sent signal is 'no', returning to continue Step1 to continue collecting and calculating the single-end electrical quantity, and if the sent signal is 'yes', determining that the line has a fault and sending a protection starting signal.
A dc line fault detection system comprising:
and the data acquisition module is used for acquiring the single-end electrical quantity data of the direct-current line in real time and calculating the space modulus signal of the single-end electrical quantity, namely calculating and acquiring the voltage and current values of the positive pole and the negative pole of the direct-current line.
And the numerical value calculation module is used for calculating the cumulant of the power transformation of the space modulus signal variation of the single-ended electrical quantity in a set time window and constructing a fault detection signal.
And the fault detection module is used for continuously collecting the fault detection signals of three adjacent times and judging whether the fault detection signals are all larger than a set detection threshold value. If not, returning to continue collecting and calculating, if yes, determining that the line is in fault, and sending a protection starting signal.
And the data preprocessing module is used for analyzing and processing the collected electric quantity of the direct current transmission line, so that the calculated quantity of the system is reduced, and the time is saved.
The data acquisition module comprises:
and the direct current line current acquisition unit is used for acquiring current signals from the direct current line.
And the direct current line voltage acquisition unit is used for acquiring voltage signals from the direct current line.
And the signal output unit is used for sending the data acquired by the data acquisition module to the next module unit.
The numerical calculation module includes:
and the signal receiving unit is used for receiving the signals sent by the data acquisition module.
And the modulus change calculation unit is used for performing space modulus transformation on the acquired data on the direct current line so as to obtain a zero modulus and a one modulus.
And the difference calculation unit is used for performing difference calculation on the data obtained by the modulus conversion.
And a power transformation calculation unit for performing power transformation on the data after the difference calculation.
And the integral calculation unit is used for performing integral operation on the data subjected to the power transformation.
And the signal output unit is used for sending the data processed by the numerical calculation module to the fault detection module.
The fault detection module includes:
and the signal receiving unit is used for receiving the signal sent by the numerical calculation module.
And the logic comparison unit is used for comparing the data sent by the numerical value calculation module with a set detection threshold value so as to judge whether the line has a fault or not and transmitting a yes/no signal to the next unit.
And the execution output unit is used for executing the signal from the logic comparison unit. If a "yes" signal is received, a protection signal is issued. If no signal is received, returning to the data acquisition module and continuously acquiring the real-time signal.
The invention discloses a method and a system for protecting a direct current transmission line, which improve the rapidity of the detection technology by arranging a data preprocessing module and collecting and calculating real-time electrical variation; by carrying out differential change, power conversion and integral conversion on the modulus of the voltage and the current, the difference between the fault quantity and the non-fault quantity is increased, so that the sensitivity of the detection technology is improved; the detection signal is compared with the protected threshold value three times in succession, so that the reliability of the detection technology is improved. Compared with the traditional fault transient component-based detection method, the technology amplifies the transient fault component through phase-mode transformation, differential transformation and integral transformation. The method provided by the technology can quickly and reliably detect the line fault, and has sensitivity, reliability and quick action.
The beneficial effects of the invention are:
1. the invention uses the fault analysis component as the judgment basis, and compared with the invention of longitudinal differential protection, the protection speed is faster.
2. The invention has a data preprocessing part and three times of diagnosis in the detection part, thereby improving the reliability of the invention.
3. According to the invention, the difference between the fault quantity and the non-fault quantity is increased by carrying out difference, power transformation and integral transformation on the fault components, so that the sensitivity of the invention is improved.
4. Compared with the existing protection method, the method greatly improves the identification degree of fault signals by constructing differential change, power conversion and integral conversion, thereby reducing the possibility of protection refusal caused by weak faults and further improving the reliability of the system.
5. Compared with the existing protection method, the method can be flexibly configured on the direct current transmission line under various situations, and can be used for calibrating different types of faults under different sampling rates.
Drawings
In order to more clearly illustrate the embodiments of the present invention 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, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained based on these drawings without implementing inventive efforts.
Fig. 1 is a flow chart of a method for detecting a fault of a dc transmission line according to an embodiment of the present invention;
fig. 2 is a detailed flowchart of step S1 in embodiment 1 of the present invention;
FIG. 3 is a flowchart showing the detailed procedure of step S2 in embodiment 1 of the present invention
Fig. 4 is a detailed flowchart of step S3 in embodiment 1 of the present invention;
fig. 5 is a graph of sampling data in the case where far-end high-impedance unipolar grounding occurs in embodiment 1 of the present invention;
fig. 6 is a diagram of the result of the failure detection in embodiment 1 of the present invention;
fig. 7 is a diagram of the result of the failure detection in embodiment 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art based on the embodiments of the present invention without inventive step, are within the scope of the present invention.
The invention aims to provide a method and a system for detecting faults of a direct current transmission line, which aim to solve the problem that the existing direct current line cannot be fast and reliable when high-resistance faults and long-distance faults occur. Accurate action problem. According to the method, a direct current transmission line model with the voltage grade of 800kV and the line length of 1500km is built on a PSCAD/EMTDC mode, normal operation and abnormal operation under different sampling frequencies are set in the model, and the abnormal operation comprises multiple conditions such as single-pole faults, high-resistance faults and long-distance faults.
Example 1: as shown in fig. 1, a method for detecting a single-pole ground fault of a direct current transmission line under a long-distance high-resistance condition includes the following steps:
step 1: the method includes the steps of collecting single-end electrical quantity data of a direct-current line in real time to obtain a space modulus signal of the single-end electrical quantity, as shown in fig. 2, and specifically includes the following steps:
step1.1: the method comprises the steps of collecting single-ended electrical quantity data of a direct-current line in real time, wherein the single end refers to any end of a direct-current transmission line, namely a first end or a second end of the line. The real-time acquisition of the single-ended electrical quantity data of the direct-current line refers to the real-time acquisition of the voltage quantity and the current quantity U of the positive pole and the negative pole of the direct-current transmission line+、U-；
Step1.2: calculating the collected voltage and current through DC line phase-mode conversion to obtain space modulus signal u0、u1And, as shown in formula (1):
Figure GDA0003530044950000061
in the formula (1), u0(n)、u1And (n) respectively represents the voltage values of the zero module and the one module of the nth sampling point.
Step1.3: selecting a spatial modulus signal u1As a fault characteristic value CΣAs shown in equation (2):
CΣ(n)＝u1(n) (2)
in the formula (2), CΣ(n) represents the nth spatial modulus semaphore.
Step 2: obtaining the cumulant of the power transformation of the space modulus signal variation of the single-end electrical quantity in a set time window, and constructing a fault detection signal, as shown in fig. 3, specifically comprising the steps of:
step 2.1: the obtained space modulus signal CΣThe spatial modulus variation Δ C is calculated by differential transformation, as shown in equation (3):
ΔC(n)＝CΣ(n+1)-CΣ(n) (3)
in the formula (3), Δ C (n) represents a difference calculation value of the nth sampling point, CΣ(n +1) represents the (n +1) th spatial modulus semaphore.
Step2.2: performing power transformation on the obtained space modulus variable quantity by exponential operation, as shown in formula (4):
Cmbh(n)＝(ΔC(n))α (4)
in the formula (4), CmbhAnd (n) represents a power conversion value of the difference calculation value of the nth sampling point, wherein alpha is a numerical value of exponential operation and takes a value of 3.
Step2.3: different sampling frequencies and integration time windows are set according to different application scenes, and the product of the sampling frequencies and the integration time windows is changed to obtain a set time window N, as shown in a formula (5):
Figure GDA0003530044950000062
in the formula (5), f is the sampling frequency and is 20kHz,
Figure GDA0003530044950000063
is a sampling period, and takes 5 × 10-5T is an integral time window, and the value is 4 ms; n is the number of samples.
Step2.4: and (3) integrating and changing the power transformation of the space modulus variation in a set time window to obtain an accumulated quantity, and constructing a fault detection signal according to the accumulated quantity, wherein the accumulated quantity is expressed by the formula (6):
Figure GDA0003530044950000071
in formula (6), CLJ(k) Indicating the kth fault detection signal.
Step 3: and continuously judging fault detection signals of at least three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continuously collect and calculate the single-end electric quantity, and if so, sending a protection starting signal for the line fault. As shown in fig. 4, the specific steps include:
step3.1: after receiving the detection signal sent by the numerical calculation module, the detection system selects three adjacent detection signals CLJ(k)、CLJ(k+1)、CLJ(k+2)。
Wherein, CLJ(k) Denotes the kth detection signal, CLJ(k +1) denotes the (k +1) th detection signal, CLJ(k +2) denotes the (k +2) th detection signal.
Step3.2: and judging whether the three detection signals selected by the system are greater than a set detection threshold value or not, and sending out 'yes' and 'no' signals.
Comparing the three detection signals selected by the system with a set detection threshold value, as shown in formula (7):
Figure GDA0003530044950000072
the set detection threshold Ced is set according to data acquired by an actual line in a stable operation state, and the value is 0.4021.
Step3.3: if the sent signal is 'no', returning to continue Step1 to continue collecting and calculating the single-end electric quantity, and if the sent signal is 'yes', sending a protection starting signal for the line fault.
As shown in fig. 5 and 6, the dc line fault detection result is a signal of the detection result transmitted to the branch breaker that performs output on the faulty line, and the faulty line is cut off.
A dc line fault detection system comprising:
and the data acquisition module is used for acquiring the single-end electrical quantity data of the direct-current line in real time and calculating the space modulus signal of the single-end electrical quantity, namely calculating and acquiring the voltage and current values of the positive pole and the negative pole of the direct-current line.
And the numerical value calculation module is used for calculating the cumulant of the power transformation of the space modulus signal variation of the single-ended electrical quantity in a set time window and constructing a fault detection signal.
And the fault detection module is used for continuously collecting the fault detection signals of three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continue collecting and calculating, and if so, sending a protection starting signal for the line fault.
And the data preprocessing module is used for analyzing and processing the collected electric quantity of the direct current transmission line, so that the calculated quantity of the system is reduced, and the time is saved.
The data acquisition module comprises:
and the direct current line current acquisition unit is used for acquiring current signals from the direct current line.
And the direct current line voltage acquisition unit is used for acquiring voltage signals from the direct current line.
And the signal output unit is used for transmitting the data acquired by the data acquisition module to the next module unit.
The numerical calculation module includes:
and the signal receiving unit is used for receiving the signals sent by the data acquisition module.
And the modulus change calculation unit is used for performing space modulus transformation on the acquired data on the direct current line so as to obtain a zero modulus and a one modulus.
And the difference calculating unit is used for performing difference calculation on the data obtained by the modulus transformation.
And a power transformation calculation unit for performing power transformation on the data after the difference calculation.
And the integral calculation unit is used for carrying out integral operation on the data subjected to the power transformation.
And the signal output unit is used for sending the data processed by the numerical calculation module to the fault detection module.
The fault detection module includes:
and the signal receiving unit is used for receiving the signal sent by the numerical calculation module.
And the logic comparison unit is used for comparing the data sent by the numerical value calculation module with a set detection threshold value so as to judge whether the line has a fault or not and transmitting a yes/no signal to the next unit.
And the execution output unit is used for executing the signal from the logic comparison unit and sending out a protection signal if receiving the 'yes' signal. If no, returning to the data acquisition module to continue to acquire the real-time signals.
Example 2: a method for detecting an interelectrode short-circuit fault of a direct current transmission line under a long-distance high-resistance fault comprises the following specific steps:
step 1: the method comprises the following steps of collecting single-end electric quantity data of a direct-current line in real time to obtain a space modulus signal of the single-end electric quantity, and specifically comprises the following steps:
step1.1: the method comprises the steps of collecting single-ended electrical quantity data of a direct-current line in real time, wherein the single end refers to any end of a direct-current transmission line, namely a first end or a second end of the line; the real-time acquisition of the single-ended electrical quantity data of the direct-current line refers to the real-time acquisition of the voltage quantity and the current quantity U of the positive pole and the negative pole of the direct-current transmission line+、U-；
Step1.2: calculating the collected voltage and current amount through direct current line phase-mode conversion to obtain a space modulus signal u+、u-And, as shown in formula (1):
Figure GDA0003530044950000091
in the formula (1), u0(n)、u1And (n) respectively represents the values of the zero-mode voltage and the one-mode voltage of the nth sampling point.
Step1.3: selecting a spatial modulus signal u1As a fault characteristic value CΣAs shown in equation (2):
CΣ(n)＝u1(n) (2)
in the formula (2), CΣ(n) represents the nth spatial modulus semaphore.
Step 2: obtaining the cumulant of the power transformation of the space modulus signal variation of the single-ended electrical quantity in a set time window, and constructing a fault detection signal, wherein the method specifically comprises the following steps of:
step2.1: the obtained space modulus signal CΣComputing nulls by differential transformationThe change Δ C in the inter-modulus, as shown in formula (3):
ΔC(n)＝CΣ(n+1)-CΣ(n) (3)
in the formula (3), Δ C (n) represents a difference calculation value of the nth sample point, CΣ(n +1) represents the (n +1) th spatial modulus semaphore.
Step 2.2: performing exponential transformation on the obtained space phasor variation by exponential amplification, as shown in formula (4):
Cmbh(n)＝(ΔC(n))α (4)
in the formula (4), CmbhAnd (n) represents a power conversion value of the difference calculation value of the nth sampling point, wherein alpha is a numerical value of exponential operation and takes a value of 2.
Step2.3: the set sampling times N are obtained by multiplying the sampling periods and the integration time windows, as shown in equation (5):
Figure GDA0003530044950000092
in the formula (5), f is sampling frequency and takes 1MHz,
Figure GDA0003530044950000093
for a sampling period, take a value of 10-6T is an integral time window, and the value is 5 ms; n is the number of samples.
Step2.4: the accumulated quantity obtained by integrating and changing the power transformation of the space modulus variation in a set time window is used as a fault detection signal, and the fault detection signal is expressed by the following formula (6):
Figure GDA0003530044950000101
in the formula (6), CLJ(k) Indicating the kth fault detection signal.
Step 3: continuously judging the fault detection signals of three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continue collecting and calculating, if so, sending a protection starting signal for the line fault, and specifically comprising the following steps:
step3.1: after receiving the detection signal sent by the numerical calculation module, the detection system selects three consecutive detection signals CLJ(k)、CLJ(k+1)、CLJ(k+2)。
CLJ(k) Denotes the kth detection signal, CLJ(k +1) denotes the (k +1) th detection signal, CLJ(k +2) denotes the (k +2) th detection signal.
Step3.2: comparing the three detection signals selected by the system with a set detection threshold, as shown in formula (7):
Figure GDA0003530044950000102
in the equation (7), the set detection threshold Ced is set according to the data acquired by the actual line in the stable operation state, and the value is 0.0056.
Step3.3: as shown in fig. 7, the dc line fault detection result is a signal of the detection result transmitted to the branch breaker that performs output on the faulty line, and the faulty line is cut off.
The invention uses the fault analysis component as the judgment basis, compared with the invention of longitudinal differential protection, the protection speed of the invention is faster; the invention has a data preprocessing part and diagnoses on the detecting part for three times continuously, thus improving the reliability of the invention; the invention increases the difference between the fault quantity and the non-fault quantity by carrying out differential change, power conversion and integral conversion on the fault component, thereby improving the sensitivity of the invention.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.

Claims (9)

1. A fault detection method for a direct current transmission line is characterized by comprising the following steps:
step 1: acquiring single-end electric quantity data of a direct-current line to obtain a space modulus signal of the single-end electric quantity;
step 2: obtaining the cumulant of the power transformation of the space modulus signal variation of the single-end electrical quantity in a set time window, and constructing a fault detection signal;
step 3: continuously judging fault detection signals of at least three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continue collecting and calculating, and if so, sending a protection starting signal for the line fault;
the Step1 comprises the following specific steps:
step1.1: the real-time acquisition of the single-end electrical quantity data of the direct-current line refers to the real-time acquisition of the voltage quantity and the current quantity U of the positive pole and the negative pole of the direct-current transmission line+、U-、I+、I-；
Step1.2: calculating the acquired voltage and current magnitude through the modulus transformation of the direct current line to obtain a space modulus signal;
spatial modulus signal CΣThe method is obtained through phase-mode conversion of single-end electric quantity data, and is shown in a formula (1):
Figure FDA0003695958740000011
in the formula (1), u1(n)、i1(n) respectively representing the values of the voltage and the current of the nth sampling point;
step1.3: selecting a spatial modulus signal u1、i1As a fault characteristic value CΣAs shown in formula (2):
CΣ(n)＝u1(n)、CΣ(n)＝i1(n) (2)
in the formula (2), CΣ(n) represents the nth spatial modulus semaphore.
2. The method for detecting the fault of the direct current transmission line according to claim 1, characterized in that: the single end of the direct current line refers to any end of the direct current transmission line, namely the first end or the second end of the line.
3. The method for detecting the fault of the direct current transmission line according to claim 1, wherein Step2 comprises the following specific steps:
step2.1: calculating the obtained space modulus signal through differential transformation to obtain space modulus variation;
step 2.2: performing exponential transformation on the obtained space phasor variation to obtain space modulus variation by exponential operation;
step2.3: setting different sampling frequencies and integration time windows according to different application scenes, and carrying out product change on the sampling frequencies and the integration time windows to obtain a set time window N;
step2.4: and integrating and changing the power transformation of the space modulus variation in a set time window to obtain an accumulated quantity, and constructing a fault detection signal according to the accumulated quantity.
4. The method for detecting the fault of the direct current transmission line according to claim 1, wherein Step3 comprises the following specific steps:
step3.1: after receiving the detection signals sent by the numerical calculation module, the detection system selects three adjacent detection signals;
step3.2: judging whether the three detection signals selected by the system are greater than a set detection threshold value or not, and sending a yes signal and a no signal;
step3.3: if the sent signal is 'no', returning to continue Step1 to continue collecting and calculating the single-end electrical quantity, and if the sent signal is 'yes', determining that the line has a fault and sending a protection starting signal.
5. A dc line fault detection system, comprising:
the data acquisition module is used for acquiring single-ended electrical quantity data of the direct-current line in real time and calculating a space modulus signal of the single-ended electrical quantity, namely calculating and acquiring voltage and current values of a positive pole and a negative pole of the direct-current line;
the numerical value calculation module is used for calculating the cumulant of the power transformation of the space modulus signal variation of the single-ended electrical quantity in a set time window and constructing a fault detection signal;
the specific acquisition process of the spatial modulus signal is as follows:
the real-time acquisition of the single-end electrical quantity data of the direct-current line refers to the real-time acquisition of the voltage quantity and the current quantity U of the positive pole and the negative pole of the direct-current transmission line+、U-、I+、I-；
Calculating the acquired voltage and current magnitude through the modulus conversion of the direct current line to obtain a space modulus signal;
spatial modulus signal CΣThe method is obtained through phase-mode conversion of single-end electric quantity data, and is shown as a formula (1):
Figure FDA0003695958740000021
in the formula (1), u1(n)、i1(n) respectively representing the values of the voltage and the current of the nth sampling point;
selecting a spatial modulus signal u1、i1As a fault characteristic value CΣAs shown in formula (2):
CΣ(n)＝u1(n)、CΣ(n)＝i1(n) (2)
in the formula (2), CΣ(n) represents the nth spatial modulus semaphore;
and the fault detection module is used for continuously collecting the fault detection signals of three adjacent times, judging whether the fault detection signals are all larger than a set detection threshold value, if not, returning to continue collecting and calculating, and if so, sending a protection starting signal for the line fault.
6. The dc line fault detection system of claim 5, wherein: the system also comprises a data preprocessing module which is used for analyzing and processing the collected electric quantity of the direct current transmission line.
7. The dc line fault detection system of claim 5, wherein the data acquisition module comprises:
the direct current line current acquisition unit is used for acquiring current signals from a direct current line;
the direct current line voltage acquisition unit is used for acquiring voltage signals from a direct current line;
and the signal output unit is used for sending the data acquired by the data acquisition module to the next module unit.
8. The dc line fault detection system of claim 5, wherein said numerical calculation module comprises:
the signal receiving unit is used for receiving signals sent by the data acquisition module;
the modulus change calculation unit is used for carrying out space modulus transformation on the collected data on the direct current line so as to obtain a zero modulus and a one modulus;
the difference calculation unit is used for carrying out difference calculation on data obtained by the modulus transformation;
a power conversion calculation unit for performing power conversion on the data after the difference calculation;
an integral calculation unit for performing integral operation on the power-transformed data;
and the signal output unit is used for sending the data processed by the numerical calculation module to the fault detection module.
9. The dc line fault detection system of claim 5, wherein the fault detection module comprises:
the signal receiving unit is used for receiving signals sent by the numerical calculation module;
the logic comparison unit is used for comparing the data sent by the numerical value calculation module with a set detection threshold value so as to judge whether a line has a fault or not and transmitting a yes/no signal to the next unit;
the execution output unit is used for executing the signal from the logic comparison unit and sending out a protection signal if receiving a 'yes' signal; if no signal is received, returning to the data acquisition module and continuously acquiring the real-time signal.
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