CN116544895B - Pumped storage power station cable sheath fault grading protection method based on induced parameters - Google Patents

Pumped storage power station cable sheath fault grading protection method based on induced parameters Download PDF

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Publication number
CN116544895B
CN116544895B CN202310819964.8A CN202310819964A CN116544895B CN 116544895 B CN116544895 B CN 116544895B CN 202310819964 A CN202310819964 A CN 202310819964A CN 116544895 B CN116544895 B CN 116544895B
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sheath
protector
cable
phase
cable sheath
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CN116544895A (en
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刘德亮
郑欢
刘吉沼
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Shanwei Power Supply Bureau of Guangdong Power Grid Co Ltd
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Shanwei Power Supply Bureau of Guangdong Power Grid Co Ltd
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    • 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
    • H02H7/22—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 for distribution gear, e.g. bus-bar systems; for switching devices
    • H02H7/226—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 for distribution gear, e.g. bus-bar systems; for switching devices for wires or cables, e.g. heating wires
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/20—Hydro energy

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Abstract

The invention discloses a pumped storage power station cable sheath fault grading protection method based on induced parameters. The method comprises the following steps: according to the actually measured induction parameter data, calculating the impedance of each phase of cable sheath, and calculating the induction overvoltage level of each phase of cable sheath according to an impedance matrix; determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the sheath protector of the cable sheath comprises a high threshold protector and a low threshold protector; parameters are configured for the high threshold protector and the low threshold protector. On the basis of meeting the standard, the protector of one phase of cable sheath is set to be a lower threshold value, and the other two phases are set to be a higher threshold value. In the occasion that the overvoltage condition is lower, only the low threshold value phase is conducted first, and the low threshold value phase and the ground form an energy discharge channel, so that the insulation safety of the cable sheath is ensured. The method prolongs the phase cable sheath insulation where the high threshold protector is located and the service life of the protector.

Description

Pumped storage power station cable sheath fault grading protection method based on induced parameters
Technical Field
The invention relates to the technical field of cable protection, in particular to a pumped storage power station cable sheath fault grading protection method based on induced parameters.
Background
The 500kV pumped storage power station underground factory building is commonly laid in a high-voltage cable hole in a single-end connection mode after a main power cable is out of line. When a ground fault or lightning wave invasion occurs, overvoltage is induced at the non-grounding end of the cable sheath, and the cable sheath insulation is jeopardized. Therefore, a voltage limiter called a sheath protector, which is a high-resistance state in normal operation and a low-resistance state in overvoltage occurrence, is required to be added at the tail end of each phase of metal sheath of the cable to limit the sheath voltage.
The GB50217-2018 power engineering cable design standard specifies the basic conditions that the sheath protector needs to meet. At present, the value of the protector is calculated through a single-phase cable, three identical models are selected after standard indexes are met, three identical protection layer protectors are adopted, the overvoltage exceeds the action voltage of the protector, and the three protectors all act, so that the service life of the protector is reduced simultaneously.
Disclosure of Invention
The invention provides a pumped storage power station cable sheath fault grading protection method based on induced parameters, which is used for realizing that only a low-threshold protector is required to be conducted under the condition of low overvoltage, and prolonging the service life of the protector.
According to one aspect of the invention, a pumped storage power station cable sheath fault grading protection method based on induced parameters is provided, comprising the following steps: according to the actually measured induction parameter data, calculating the impedance of each phase of cable sheath, and calculating the induction overvoltage level of each phase of cable sheath according to an impedance matrix; the actually measured induction parameters comprise cable grounding resistance, induced voltage of each phase of cable sheath and induced circulation of return wire;
determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable protection layer protector comprises a high threshold protector and a low threshold protector;
parameters are configured for the high threshold protector and the low threshold protector.
Optionally, calculating the impedance of each phase of the cable sheath according to the measured sensing parameter data, and calculating the sensing overvoltage level of each phase of the cable sheath according to the impedance matrix includes:
measuring the grounding resistance of the cable sheath, the three-phase sheath induced voltage, the three-phase load current and the return wire induced circulation;
obtaining an inductive reactance matrix of the cable sheath according to the grounding resistance, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation;
and calculating the induced overvoltage of each phase of cable sheath according to the inductance matrix of the cable sheath.
Optionally, calculating the induced overvoltage of the cable sheath of each phase according to the inductance matrix of the cable sheath includes:
acquiring a short-circuit current full current and a preset short-circuit current;
and calculating the induction overvoltage of each phase of cable sheath according to the grounding resistance of the cable sheath, the total current of the short-circuit current, the preset short-circuit current and the inductance matrix of the cable sheath.
Optionally, determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath includes:
sequencing according to the magnitude of the induced overvoltage, and sequentially carrying out priority assignment according to the sequencing;
respectively calculating the comprehensive installation priority of each phase of cable sheath according to the priority assignment;
and selecting the one-phase cable with the highest comprehensive installation priority as the installation phase of the low-threshold protector.
Optionally, before sorting according to the magnitude of the induced overvoltage and sequentially assigning priority according to the sorting, the method further comprises:
defining a sheath installation priority;
an installation priority array is defined.
Optionally, sorting according to the magnitude of the induced overvoltage, and sequentially assigning priority according to the sorting includes:
when the induced overvoltage represents self-induced voltage between the cable core and the cable protection layer, sequencing the induced overvoltage from small to large, and giving corresponding protection layer installation priority to an installation priority array corresponding to the induced overvoltage according to sequencing; wherein, the smaller the induced overvoltage, the higher the sheath installation priority;
when the induced overvoltage represents the mutual inductance voltage between the cable core and the cable sheath, sequencing the induced overvoltage from large to small, and giving corresponding sheath installation priority to an installation priority array corresponding to the induced overvoltage according to sequencing; wherein, the greater the induced overvoltage, the higher the sheath installation priority.
The configuration parameters of the sheath protector of each cable sheath include rated voltage, operating voltage, residual voltage and maximum absorption capacity.
Optionally, configuring parameters for the high threshold protector and the low threshold protector includes:
calculating rated voltage of the sheath protector of each cable sheath according to the action condition and the fault voltage of the sheath protector of each cable sheath;
calculating the action voltage of the sheath protector of each cable sheath according to the rated voltage of the sheath protector of each cable sheath;
selecting residual voltage of the sheath protector of each cable sheath according to the impulse voltage tolerance value of the cable sheath;
and calculating the maximum absorption capacity of the sheath protector of each cable sheath according to the residual voltage, the square wave through current and the square wave through current time of the sheath protector of each cable sheath.
Optionally, after calculating the maximum absorption capacity of the sheath protector of each cable sheath according to the residual voltage, the square wave through current and the square wave through current time of the sheath protector of each cable sheath, the method further comprises:
calculating the energy absorbed by the sheath protector of each cable sheath during the action;
and adjusting square wave through current of the sheath protector of each cable sheath to ensure that the maximum absorption capacity of the sheath protector of each cable sheath is larger than the energy absorbed by the sheath protector of each cable sheath during the action.
According to the technical scheme, the induced overvoltage of each phase of cable protective layer is calculated by measuring the parameters of the cable, and the installation position of the protective layer protector of each cable protective layer is determined according to the induced overvoltage of each phase of cable protective layer; the sheath protector of one phase of cable sheath can be set as a low threshold protector on the basis of meeting the standard, and the sheath protector of the other two phases of cable sheath can be set as a high threshold protector. For the occasion with lower overvoltage, only the low-threshold protector is needed to be conducted, the phase cable sheath and the ground form a loop, and the loop becomes an energy discharge channel, so that the overvoltage of the cable sheath can be effectively restrained, the cable sheath is protected, and the service life of the other two-phase protector is prolonged.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a pumped storage power station cable sheath fault grading protection method based on induced parameters provided by an embodiment of the invention;
fig. 2 is a schematic circuit diagram of a cable according to an embodiment of the present invention;
FIG. 3 is a flow chart of another pumped storage power station cable sheath fault classification protection method based on induced parameters according to an embodiment of the present invention;
FIG. 4 is a flow chart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention;
FIG. 5 is a flow chart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention;
FIG. 6 is a flow chart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention;
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The embodiment of the invention provides a pumped storage power station cable sheath fault grading protection method based on induced parameters, which can be executed by a 500kV pumped storage power station single-end grounding cable sheath fault grading protection position determining device based on the induced parameters, and the device can be realized by software and/or hardware. Fig. 1 is a flowchart of a pumped storage power station cable sheath fault grading protection method based on induced parameters, which is provided in an embodiment of the present invention, as shown in fig. 1, and the method includes:
s101, calculating the impedance of each phase of cable sheath according to the actually measured induction parameter data, and calculating the induction overvoltage level of each phase of cable sheath according to an impedance matrix; the actually measured induction parameters comprise cable grounding resistance, induced voltage of each phase of cable sheath and induced circulation of return wire.
Specifically, fig. 2 is a schematic circuit diagram of a cable according to an embodiment of the present invention, and as shown in fig. 2, the cable may be a three-phase cable, and the three-phase cable is numbered, for example, an a-phase subscript 1, a b-phase subscript 2, and a c-phase subscript 3. And measuring parameters of the cable, obtaining actually measured induction parameter data, and calculating induction overvoltage of each phase of cable sheath, wherein the actually measured induction parameters comprise cable grounding resistance, each phase of cable sheath induction voltage and return line induction circulation.
For example, three-phase sheath induced voltages U1, U2, U3 are actually measuredThree-phase load currents I1, I2 and I3 are actually measured, and return line induction loop current I is actually measured p 。
The sheath inductance matrix X is calculated according to the following formula:
；
three-phase load current matrix；
Cable sheath induced voltage matrix；
Wherein, the current flowing into the ground,/>Indicating the cable ground resistance.
S102, determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable sheath protector comprises a high threshold protector and a low threshold protector.
The induced overvoltage of the cable sheath represents the induced voltage when the cable where the cable sheath is located has a single-phase earth fault, the action voltage of the sheath protector of the cable sheath can be set to be lower, namely the low-threshold protector, and the action voltage of the sheath protector of the cable sheath can be set to be higher, namely the high-threshold protector. And determining the priority of each phase of cable according to the induced overvoltage of each phase of cable sheath, and determining the installation position of the sheath protector of each cable sheath according to the priority. For example, the sheath protector of one phase of cable sheath is set as a low threshold protector, and the sheath protector of the other two phases of cable sheath is set as a high threshold protector, so that the low threshold protector is only required to be conducted for protection under the condition of low overvoltage, and the service life of the other two phases of cable sheath is prolonged.
S103, configuring parameters for a high threshold protector and a low threshold protector.
Namely, respectively determining parameters of the sheath protector of each cable sheath; parameters of the sheath protector of each cable sheath can include rated voltage, action voltage, residual voltage and maximum absorption capacity.
Specifically, parameters of the sheath protectors of the cable sheaths are respectively determined through calculation, so that the sheath protectors of the cable sheaths can ensure that the cable can work normally under normal working conditions and fault conditions, and the situation that only the low-threshold protector acts to protect the cable sheath in the occasion with lower overvoltage can be met, and the sheath protectors of the three cable sheaths are conducted when the overvoltage is higher. The rated voltage of the sheath protector of the cable sheath is the voltage when the sheath protector of the cable sheath works normally. The action voltage is that the sheath protector of the cable sheath detects the cable short circuit and conducts itself, so that the phase cable sheath and the ground form a loop and become the voltage of the energy discharge channel. The residual voltage is the peak voltage at the sheath protector designated end of the cable sheath when a discharge current flows. The maximum absorption capacity is the maximum capacity of the sheath protector of the cable sheath to absorb energy generated when the cable is operated or short-circuited.
According to the technical scheme, the induction overvoltage of each phase of cable protective layer is calculated by measuring the parameters of the cable, and the installation position of the protective layer protector of each cable protective layer is determined according to the induction overvoltage of each phase of cable protective layer; for example, the sheath protector of one of the two-phase cable sheaths may be set as a low threshold protector and the sheath protector of the other two-phase cable sheath may be set as a high threshold protector on the basis of satisfaction of the criteria. For the occasion with lower overvoltage, only the low-threshold protector is needed to be conducted, the phase cable sheath and the ground form a loop, and the loop becomes an energy discharge channel, so that the overvoltage of the cable sheath can be effectively restrained, the cable sheath is protected, and the service life of the other two-phase protector is prolonged.
Fig. 3 is a flowchart of another pumped storage power station cable sheath fault classification protection method based on induced parameters according to an embodiment of the present invention, optionally, referring to fig. 3, the method includes:
and S201, measuring the grounding resistance of the cable sheath, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation.
S202, obtaining an inductance matrix of the cable sheath according to the grounding resistance, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation.
Calculating a sheath inductance matrix X:
；
obtaining a sheath inductance matrix:
X=；
wherein, mutual inductance X of the cable 12 、X 13 、X 21 、X 23 、X 31 、X 32 And self-inductance X resistance of cable core and cable sheath s1 、X s2 、X s3 。
S203, calculating the induction overvoltage of each phase of cable sheath according to the inductance matrix of the cable sheath.
Specifically, according to the inductance matrix of the cable sheath, calculating the induced voltage when single-phase earth faults occur to each phase cable with the single-phase earth of the cable sheath; wherein, according to annex B of the high-voltage cable selection guide rule (DL/T401-2017), the formula for calculating the induced overvoltage of each phase cable sheath is as follows:
（1）
wherein, thereinRepresenting the induction voltage generated on the i-phase cable protective layer when the j-phase cable cell has short circuit fault; />Representing short-circuit currentA current; />Representing a preset short-circuit current, ">Representing the single-end ground resistance of the cable way.
S204, determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable sheath protector comprises a high threshold protector and a low threshold protector.
S205, configuring parameters for a high threshold protector and a low threshold protector.
Fig. 4 is a flowchart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention, optionally, referring to fig. 4, the method includes:
and S301, measuring the grounding resistance of the cable sheath, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation.
S302, obtaining an inductance matrix of the cable sheath according to the grounding resistance, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation.
S303, acquiring the total current of the short-circuit current and the preset short-circuit current.
Specifically, obtaining a short-circuit current full current and a preset short-circuit current through measurement; the short-circuit current total current is the current flowing when short circuit occurs between phases or between phases and ground in the operation of the power system; the preset short-circuit current is the short-circuit current provided by the power station.
S304, according to the grounding resistance of the cable sheath, the total current of the short-circuit current, the preset short-circuit current and the inductive reactance matrix of the cable sheath, the inductive overvoltage of each phase of cable sheath is calculated.
Specifically, the grounding resistance, the total short-circuit current, the preset short-circuit current and the inductive reactance matrix of the cable sheath are substituted into the formula (1), so that the induced overvoltage of each phase of cable sheath can be obtained. Illustratively, the induced overvoltage of each phase sheath of the three-phase cable is:
s305, determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable sheath protector comprises a high threshold protector and a low threshold protector.
According to the technical scheme, parameters of the cable are measured, induced overvoltage of each phase of cable protection layer is calculated by substituting the parameters into a formula, and the installation position of the protection layer protector of each cable protection layer is determined according to the induced overvoltage of each phase of cable protection layer; and on the basis of meeting the standard, the sheath protector of one phase of cable sheath is set as a low threshold protector, and the sheath protector of the other two phases of cable sheath is set as a high threshold protector. For the occasion with lower overvoltage, only the low-threshold protector is needed to be conducted, the phase cable sheath and the ground form a loop, and the loop becomes an energy discharge channel, so that the overvoltage of the cable sheath can be effectively restrained, the cable sheath is protected, and the service life of the other two-phase protector is prolonged.
Fig. 5 is a flowchart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention, optionally, referring to fig. 5, the method includes:
s401, calculating the impedance of each phase of cable sheath according to the actually measured sensing parameter data, and calculating the sensing overvoltage level of each phase of cable sheath according to the impedance matrix.
S402, defining the sheath installation priority.
Specifically, the sheath installation priority is defined according to the induced overvoltage of each phase of cable sheath, and the sheath installation priority is sequentially assigned, and the higher the assigned value is, the higher the priority is. Illustratively, the total induced overvoltage of each phase cable sheath of the three-phase cable is 9, so that 9-level sheath installation priorities PR 1-PR 9 are defined, and the sheath installation priorities are sequentially assigned to obtain: pr1=1, pr2=2, pr3=3, … … PR 8=8, pr9=9; the priority of PR9 is highest and the priority of PR1 is lowest.
S403, defining an installation priority array.
Specifically, an installation priority array PR is defined) Wherein PR (>) Representing +.>And (3) taking the value of the contribution of the installation priority of the ith cable sheath. Illustratively, when the cable is a three-phase cable, the installation is definedPriority array PR (+)>) (i, j=1, 2, 3). When i=j, _j->The self-induced voltage between the cable core and the cable protection layer is represented; when i+.j, +.>Representing the mutual inductance voltage between the cable core and the cable sheath.
S404, sorting according to the magnitude of the induced overvoltage, and sequentially carrying out priority assignment according to the sorting.
Specifically, when the induced overvoltage represents the self-induced voltage between the cable core and the cable protection layer, sequencing the induced overvoltage from small to large, and giving corresponding protection layer installation priority to an installation priority array corresponding to the induced overvoltage according to sequencing; wherein, the smaller the induced overvoltage, the higher the sheath installation priority. Illustratively, when the induced overvoltage represents a self-induced voltage between the cable core and the cable jacket, the induced overvoltageComprises->、/>And->According to the induced overvoltage calculated by formula (1)>、/>And->The values of (2) are arranged from small to largeSequencing and sequencing PR (in accordance with the sequencing order)>) (i, j=1, 2,3, i=j) gives the corresponding sheath installation priority. For example, if->、/>And->Ordering from small to large as +.>＜/>＜/>For PR (+)>) Giving the sheath mounting priority PR9 to PR (-)>) Giving the sheath mounting priority PR8 to PR ()>) Giving the sheath mounting priority PR7, namely PR +>)=9，PR(/>)=8，PR(/>)=7。
When the induced overvoltage represents the mutual inductance voltage between the cable core and the cable protection layer, sequencing the induced overvoltage from large to small, andaccording to the sequencing, corresponding sheath installation priority is given to the installation priority array corresponding to the induced overvoltage; wherein, the greater the induced overvoltage, the higher the sheath installation priority. Illustratively, when the induced overvoltage represents a mutual inductance voltage between the cable core and the cable sheath, the induced overvoltageComprises->、/>、/>、/>、/>And->According to the induced overvoltage calculated by formula (1)>、/>、/>、/>、/>And->Ordering the values of (2) from large to small and sequentially ordering PR(s) according to the ordering>) (i, j=1, 2,3, i+.j) gives the corresponding sheath mounting priority. For example, if->、、/>、/>、/>And->Ordering from big to small as +.>＞/>＞/>＞/>＞/>＞/>For PR (+)>) Giving the sheath mounting priority PR6 to PR (-)>) A value of PR5, … …, which gives priority to PR (/ -)>) Giving the sheath mounting priority PR1, namely PR (-/-)>)=6，PR(/>)=5，……，PR(/>) =1, and so on.
And S405, respectively calculating the comprehensive installation priority of each phase of cable sheath according to the priority assignment.
Specifically, according to the comprehensive installation priority calculation formula:
（2）
PR after assignment) And substituting the formula, and respectively calculating the comprehensive installation priority of each phase of cable sheath. Wherein i represents the i-th phase cable sheath, F （i） Indicating the comprehensive installation priority of the i-th phase cable sheath, F （i） The larger the comprehensive installation priority is, the higher the comprehensive installation priority is.
S406, selecting the one-phase cable with the highest comprehensive installation priority as the installation phase of the low-threshold protector.
Specifically, the one-phase cable with the highest comprehensive installation priority is selected as the installation phase of the low-threshold protector, i.e., the i = { i|max (F （i） I.e. 1,2, 3) } phase cable is used as the installation phase of the low threshold protector, and the other two phase cables are used as the installation phases of the high threshold protector.
According to the technical scheme, the induced overvoltage of each phase of cable sheath is calculated by measuring the parameters of the cables and substituting the parameters into a formula, sequencing and assigning are carried out according to the magnitude of the induced overvoltage of each phase of cable sheath, the comprehensive installation priority of each phase of cable is calculated respectively, one phase of cable with the highest comprehensive installation priority is selected as the installation phase of the low-threshold protector, and the other two phases of cable are selected as the installation phases of the high-threshold protector. For the occasion with lower overvoltage, only the low-threshold protector is needed to be conducted, the phase cable sheath and the ground form a loop, and the loop becomes an energy discharge channel, so that the overvoltage of the cable sheath can be effectively restrained, the cable sheath is protected, and the service life of the other two-phase protector is prolonged.
Fig. 6 is a flowchart of another method for protecting a pumped storage power station cable sheath fault classification based on induced parameters according to an embodiment of the present invention, optionally, referring to fig. 6, the method includes:
s601, calculating the impedance of each phase of cable sheath according to the actually measured sensing parameter data, and calculating the sensing overvoltage level of each phase of cable sheath according to the impedance matrix.
S602, determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable sheath protector comprises a high threshold protector and a low threshold protector.
S603, calculating rated voltage of the sheath protector of each cable sheath according to the action condition and the fault voltage of the sheath protector of each cable sheath.
Specifically, the calculation formula of the rated voltage is:
（3）
wherein the method comprises the steps ofAnd taking the fault voltage value when the j-th phase cable core has single-phase earth fault as the maximum overvoltage under the fault condition. K is a matching coefficient, and the higher the K is, the lower the action voltage of the protective layer protector of the cable protective layer is, the easier the action is, so that the larger the matching coefficient K is set for the installation phase of the low-threshold protector, and 1.2-1.5 is taken as an example; for the installation phase of the other two-phase high threshold protector, a smaller matching coefficient K is set, and 1.1-1.2 is taken as an example.
S604, calculating the action voltage of the sheath protector of each cable sheath according to the rated voltage of the sheath protector of each cable sheath.
Specifically, according to the formula:
（4）
calculating the action voltage of the sheath protector of each cable sheath, wherein,the action voltage of the sheath protector of each cable sheath is +.>Multiple rated voltages.
S605, selecting residual voltage of the sheath protector of each cable sheath according to the surge voltage tolerance value of the cable sheath.
Specifically, the residual voltage of the sheath protector of each of the cable sheaths cannot be greater than a value by which the lightning impulse withstand voltage of the cable sheath is divided by 1.4. According to the rule of high-voltage cable selection (DL/T401-2017) appendix B, the lightning impulse voltage tolerance value of the cable outer sheath can be obtained, as shown in the following table:
table 1 Cable outer sheath lightning impulse voltage withstand value (kV)
Main insulation lightning impulse withstand voltage of cable Lightning impulse withstand voltage of cable outer sheath
380~750 37.5
1050 47.5
1175~1425 62.5
1550 72.5
Referring to the cable outer sheath lightning impulse withstand voltage in table 1, the corresponding cable outer sheath lightning impulse withstand voltage can be selected according to cables with different rated voltage grades, and the selected cable outer sheath lightning impulse withstand voltage is still larger than the residual voltage of the sheath protector of the cable sheath after being divided by 1.4.
S606, calculating the maximum absorption capacity of the sheath protector of each cable sheath according to the residual voltage, the square wave through current and the square wave through current time of the sheath protector of each cable sheath.
Specifically, the formula for calculating the maximum absorption capacity of the sheath protector of the cable sheath is:
（5）
wherein,,for residual pressure, add (L) to>The square wave through current is the square wave through current of the sheath protector of the cable sheath, and t is the square wave through current time. Residual pressure of sheath protector according to each cable sheath>Square wave current->Calculating each cable protection by sum square wave through-flow time tMaximum absorption capacity of the protective layer protector of the layer->。
S607, calculating the energy absorbed by the sheath protector of each cable sheath during the action.
Specifically, to determine the square wave current through the sheath protector of each cable sheathMake square wave current +.>The requirement of through-flow under the fault is met, and the absorption energy W of the sheath protector of each cable sheath under the fault needs to be calculated, namely the absorption energy of the sheath protector of each cable sheath under the fault, namely the energy absorbed by the sheath protector of each cable sheath during the action. According to the formula:
（6）
calculating the absorption energy W of the sheath protector of each cable sheath, wherein、/>In order to obtain the single time of lightning current when lightning strike occurs and the action response time of the high-voltage circuit breaker when short circuit fault occurs, u (t) is the instantaneous value of the voltage of the sheath protector of the cable sheath, and i (t) is the instantaneous value of the current of the sheath protector of the cable sheath.
S608, adjusting square wave through current of the sheath protector of each cable sheath, so that the maximum absorption capacity of the sheath protector of each cable sheath is larger than the energy absorbed by the sheath protector of each cable sheath during operation.
Specifically, the square wave current of the sheath protector of each cable sheath is adjustedMaximum absorption capacity of the sheath protector of each cable sheath>Greater than the energy absorbed by the sheath protector of each cable sheath during operation>。
When lightning stroke or short circuit fault occurs to the cable, the protection layer protector of each cable protection layer can still absorb energy generated by the cable, and the protection layer protector of each cable protection layer is prevented from heating and exploding to harm the normal operation of a cable line.
According to the technical scheme, the parameters of the sheath protectors of the cable sheaths are calculated and determined respectively, so that the low-threshold protector and the high-threshold protector are conducted at different action voltages, the situation that the low-threshold protector is conducted only in the occasion of low overvoltage is realized, the overvoltage of the cable sheath is restrained, the cable sheath is protected, the service lives of other two-phase protectors are prolonged, and the safety and reliability of the sheath protectors of the cable sheaths are improved.
The embodiment of the invention also provides a pumped storage power station cable sheath fault grading protection device based on the induced parameters, which comprises the following steps: the measuring module is used for calculating the impedance of each phase of cable sheath according to the actually measured induction parameter data and calculating the induction overvoltage level of each phase of cable sheath according to the impedance matrix;
the position selection module is used for determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable sheath protector comprises a high threshold protector and a low threshold protector.
And the parameter configuration module is used for configuring parameters for the high threshold protector and the low threshold protector.
The position selection module respectively determines the comprehensive installation priority of each cable according to the parameters of the cables, which are measured by the measurement module, and the induced overvoltage of each phase of cable sheath, and respectively determines the installation phases of the high-threshold protector and the low-threshold protector according to the comprehensive installation priority of each cable.
According to the technical scheme, parameters of the cable are measured through the measuring module, the induced overvoltage of each phase of cable sheath is calculated, and the installation position of the sheath protector of each cable sheath is determined through the position selecting module according to the induced overvoltage of each phase of cable sheath; and on the basis of meeting the standard, the sheath protector of one phase of cable sheath is set as a low threshold protector, and the sheath protector of the other two phases of cable sheath is set as a high threshold protector. For the occasion with lower overvoltage, only the low-threshold protector is needed to be conducted, the phase cable sheath and the ground form a loop, and the loop becomes an energy discharge channel, so that the overvoltage of the cable sheath can be effectively restrained, the cable sheath is protected, and the service life of the other two-phase protector is prolonged.
It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present invention may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution of the present invention are achieved, and the present invention is not limited herein.
The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims (6)

1. The pumped storage power station cable sheath fault grading protection method based on the induced parameters is characterized by comprising the following steps of:
according to the actually measured induction parameter data, calculating the impedance of each phase of cable sheath, and calculating the induction overvoltage level of each phase of cable sheath according to an impedance matrix; the actually measured induction parameters comprise cable grounding resistance, induced voltage of each phase of cable sheath and induced circulation of return wire;
determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath; the cable protection layer protector comprises a high threshold protector and a low threshold protector; determining the installation position of the sheath protector of each cable sheath according to the induced overvoltage of each phase of cable sheath comprises: sequencing according to the magnitude of the induced overvoltage, and sequentially carrying out priority assignment according to the sequencing; respectively calculating the comprehensive installation priority of each phase of cable sheath according to the priority assignment; selecting the one-phase cable with the highest comprehensive installation priority as the installation phase of the low-threshold protector;
configuring parameters for the high threshold protector and the low threshold protector; the configuration parameters of the sheath protector of each cable sheath comprise rated voltage, action voltage, residual voltage and maximum absorption capacity; the configuring parameters for the high threshold protector and the low threshold protector includes: calculating rated voltage of the sheath protector of each cable sheath according to the action condition and fault voltage of the sheath protector of each cable sheath; calculating the action voltage of the sheath protector of each cable sheath according to the rated voltage of the sheath protector of each cable sheath; selecting the residual voltage of the sheath protector of each cable sheath according to the impulse voltage tolerance value of the cable sheath; and calculating the maximum absorption capacity of the sheath protector of each cable sheath according to the residual voltage, the square wave through current and the square wave through current time of the sheath protector of each cable sheath.
2. The method of claim 1, wherein calculating the impedance of each phase of the sheath based on the measured sensed parameter data and calculating the induced overvoltage level of each phase of the sheath based on the impedance matrix comprises:
measuring the grounding resistance of the cable sheath, the three-phase sheath induced voltage, the three-phase load current and the return wire induced circulation;
obtaining an inductive reactance matrix of the cable sheath according to the grounding resistance, the three-phase sheath induced voltage, the three-phase load current and the return line induced circulation;
and calculating the induction overvoltage of the cable sheath of each phase according to the inductance matrix of the cable sheath.
3. The method of claim 2, wherein said calculating the induced overvoltage of the respective phase sheath from the inductance matrix of the sheath comprises:
acquiring a short-circuit current full current and a preset short-circuit current;
and calculating the induction overvoltage of each phase of cable sheath according to the grounding resistance of the cable sheath, the short-circuit current total current, the preset short-circuit current and the inductance matrix of the cable sheath.
4. The method of claim 1, further comprising, prior to said sorting according to the magnitude of said induced overvoltage and sequentially prioritizing according to said sorting:
defining a sheath installation priority;
an installation priority array is defined.
5. The method of claim 1, wherein the sorting according to the magnitude of the induced overvoltage and the prioritizing in turn according to the sorting comprises:
when the induced overvoltage represents self-induced voltage between a cable core and the cable protection layer, sequencing the induced overvoltage from small to large, and giving corresponding protection layer installation priority to the installation priority array corresponding to the induced overvoltage according to the sequencing; wherein, the smaller the induced overvoltage, the higher the sheath installation priority;
when the induced overvoltage represents the mutual inductance voltage between the cable core and the cable protection layer, sequencing the induced overvoltage from large to small, and giving corresponding installation priority to the installation priority array corresponding to the induced overvoltage according to the sequencing; wherein, the greater the induced overvoltage, the higher the sheath installation priority.
6. The method of claim 1, wherein after calculating the maximum absorption capacity of the sheath protector of each sheath based on the residual voltage, square wave through current, and square wave through current time of the sheath protector of each sheath, further comprising:
calculating the energy absorbed by the sheath protector of each cable sheath during the action;
and adjusting the square wave through current of the sheath protector of each cable sheath to ensure that the maximum absorption capacity of the sheath protector of each cable sheath is larger than the energy absorbed by the sheath protector of each cable sheath during the action.
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