CN117169640A - Multiple ratio differential verification method and device under multi-distributed new energy access feeder line - Google Patents
Multiple ratio differential verification method and device under multi-distributed new energy access feeder line Download PDFInfo
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Abstract
The invention relates to a multiple ratio differential verification method and device under a multi-distributed new energy access feeder line, and belongs to the technical field of relay protection of power systems. The method comprises the steps of checking the mobility of the ratio differential protection, checking the reliability and stability of the ratio differential protection and checking the sensitivity of the ratio differential protection; acquisition of CT saturation induced propagation errors for faulty branchesIf (if)Checking passing, otherwise, checking failing; obtaining the ratio of the current flowing out of the bus to the total fault current as Ext, ifAnd if the verification is not passed, the verification is not passed. The invention improves the work by calculating and verifying the differential current and the braking current of the multi-branch compound differential protectionEfficiency, reduced test line, reduced electric wire netting security risk, easily popularization and application.
Description
Technical Field
The invention belongs to the technical field of relay protection of power systems, and particularly relates to a multiple ratio differential verification method and device under a multi-distributed new energy access feeder line.
Background
Most of traditional power distribution systems are single-power radial networks, even if the structure is a closed-loop network, open-loop operation modes are adopted, and the power flow and the fault current of the traditional power distribution systems all have the characteristic of unidirectional flow. Therefore, the traditional power distribution network protection configuration is simpler, and the three-section type current protection can meet the requirements. However, the access of distributed power sources (DG) changes the structure of the distribution network, such that conventional distribution networks are converted into active networks. Under the novel architecture of the active distribution network, the magnitude and the direction of the power flow and the fault current are uncertain, and the sensitivity and the selectivity of the traditional three-section current protection meet important challenges. Under the new situation, a novel bus compound ratio differential protection method suitable for the active distribution network features is needed to be researched. Compared with the protection of other principles, the current differential protection can better adapt to various complex fault conditions such as power system oscillation, asymmetric short circuit and the like, is not influenced by the disconnection of a voltage transformer, and can be widely applied to the power system. In principle, the current differential protection has absolute selectivity, and is one of the most effective ways to solve the new problem of active power distribution network protection at present.
When checking the bus differential protection ratio in the field, two branches are generally selected for addition test, and the specific method is as follows: optionally, two branches with the same transformation ratio on the bus I are added with currents I1 with opposite directions and the same magnitude at a certain phase; then, selecting a branch with the same transformation ratio on the II bus, adding a current I2 in a certain phase, and regulating the current so as to make the II bus act differentially; the applied current was recorded and the large difference ratio coefficient was verified. The bus differential ratio verification for multiple branches has a certain difficulty for field technicians, and under specific conditions, such as actual operation, the bus differential ratio verification for multiple branches needs to be set, so that a great deal of time is consumed.
Existing patent ZL201310038256.7, name: a high-precision electric signal measuring device and method mainly provides a compensation, identification and control and metering method of electric signals, and does not provide a calculation and identification method of bus compound ratio differential motion; patent ZL201610945569.4, name: an arc light protector and its fault diagnosis method features that the corresponding voltage and current signals are collected to prepare the fault diagnosis method, and the calculation and recognition method of bus compound ratio differential is not involved.
At present, unbalanced current often occurs in a circuit, so that sensitivity, rapidness and stability of bus differential protection are difficult to consider, meanwhile, the complexity of bus differential protection logic is high, the complexity of checking the existing bus compound ratio differential protection logic is high, errors are prone to occur, for example, for the ratio checking of more than two branches, factors such as primary current balance, secondary current balance, conversion of reference transformation ratio and the like of the added branches need to be considered, the time of field test personnel is usually very intense, if calculation and checking are not clear, correct differential action results are often difficult to obtain, the time of field test is delayed, the working efficiency and the working quality are reduced, the time of loops, logic and other working is shortened, and potential safety risks of a power grid are buried.
Therefore, how to overcome the defects of the prior art is a problem to be solved in the technical field of relay protection of the power system at present.
Disclosure of Invention
The invention aims to solve the defects of the prior art, overcome the problems of high logic verification complexity and easy error of the existing bus compound ratio differential protection, provide a compound ratio differential verification method and device under a multi-distributed new energy access feeder, and provide a quick multi-branch access ratio differential verification method for field technicians.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the multiple ratio differential verification method under the multi-distributed new energy access feeder line comprises ratio differential protection mobility verification, ratio differential protection reliability stability verification and ratio differential protection sensitivity verification; the method comprises the following steps:
the first step: calculating a theoretical compound ratio Kr; collecting an actual compound ratio setting value Kr';
and a second step of: the ratio differential protection mobility check is: comparing Kr with an actual compound ratio set value Kr ', and judging that the quick action verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
and a third step of: the reliable stability check of the ratio differential protection is as follows: acquisition of CT saturation induced propagation errors for faulty branchesδThen, reliable stability verification is carried out, ifChecking passing, otherwise, checking failing;
fourth step: the ratio differential protection sensitivity check is: acquiring the ratio Ext of the current flowing out of the bus to the total fault current, and then performing sensitivity verification ifThe sensitivity check passes, otherwise, the check does not pass;
Fifth step: in the second step, the third step and the fourth step, when any one of the verification passes, the first step is required to be returned, the compound ratio Kr calculation is carried out again, and when the verification passes in the second step, the third step and the fourth step, the ratio differential verification is considered to pass.
Furthermore, when the reliability and stability verification of the ratio differential protection is carried out, the fault condition outside the bus area needs to be simulated, and the specific method is as follows:
1) Optionally, two branches with the same transformation ratio on the same bus are added with a certain phase of current at the same time, wherein the currents are equal in magnitude and opposite in direction;
2) The bus differential protection should not act;
3) The large and small difference currents should be equal to zero.
Further, in performing the sensitivity check of the ratio differential protection, it is necessary to simulate a fault condition in the bus area, and the specific method includes the steps of: step (1), verifying a differential threshold fixed value:
a) Optionally adding a certain current into a certain phase of a branch on the bus, wherein the current is larger than a differential threshold constant value;
b) The bus differential protection should act instantaneously, cut off the bus and all branches on the bus where this branch is located, the bus differential action signal lamp should be on;
step (2), verifying that the differential ratio coefficient is high:
a) The bus-tie switch is closed;
b) Optionally, two branches with the same transformation ratio are arranged on the bus I, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio high-value coefficient;
step (3), verifying that the differential ratio coefficient is low:
a) The bus is switched off;
b) Optionally, two branches with the same transformation ratio are arranged on the bus I, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio low value coefficient;
step (4), verifying a small difference ratio coefficient:
a) Optionally selecting two branches with the same transformation ratio on the same bus, and adding currents with opposite directions and different magnitudes on a certain phase;
b) Fixing the current of one branch, and adjusting the current of the other branch to make the bus act differentially;
c) The applied current was recorded and the small difference ratio coefficient was verified.
Further, in the step (2), the specific method for verifying the differential ratio high value coefficient is as follows: the differential ratio high value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device, IdThe calculation method of (1) is as follows: after the bus is combined, the sum of all branch current vectors except the bus is combined;I r the brake current is the sum of absolute values of all branches;
；
wherein,representation ofL n Current transformer transformation ratio of branch circuit; />Secondary current quantity for each corresponding branch; />In the differential motion, inLxThe amount of current added by the branch; s represents a reference transformation ratio;if the equation is true, the verification is passed.
Further, in the step (3), the specific method for verifying the differential ratio low value coefficient is as follows:
differential ratio low value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is disconnected, the sum of all branch current vectors on the bus;I r the brake current is the sum of absolute values of all branches; />If the equation is true, the verification is passed.
Further, in the step (4), the specific method for verifying the small difference ratio coefficient is as follows:representing the coefficient of the small difference ratio,Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: the sum of all branch current vectors on the I or II bus,I r the braking current is the sum of absolute values of all branches of the I master or the II master; />If the equation is true, the verification is passed. Furthermore, when the sensitivity verification of the ratio differential protection is performed, the fault condition in the bus area in the double bus switching operation process needs to be simulated, and the specific method is as follows:
1) Optionally, a branch on a certain bus is closed, and a mother I and a mother II of the branch are closed;
2) Loading a single-phase current in the branch, wherein the current value is larger than the differential threshold fixed value;
3) The bus differential protection should act instantaneously, cutting off the bus and all branches on the bus;
4) I and II are differential to turn on the signal lamp. Further, in the fourth step,the value range is more than or equal to 1.5 and less than or equal to 3. Further, in the fourth step, the ∈ ->The value is 2. The invention also provides a multiple ratio differential check device under the multi-distributed new energy access feeder, which adopts the multiple ratio differential check method under the multi-distributed new energy access feeder and comprises the following steps:
the acquisition module is used for acquiring the actual complex ratio set value Kr' and the transmission error caused by CT saturation of the fault branchThe ratio of the current flowing out of the bus to the total fault current exists; the first processing module is connected with the acquisition module and is used for calculating theoretical compound ratio Kr, then carrying out ratio differential protection mobility verification, comparing Kr with an actual compound ratio set value Kr ', and judging that the mobility verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed; the second processing module is connected with the acquisition module and used for carrying out reliable stability verification, if +. >Checking passing, otherwise, checking failing; the third processing module is connected with the acquisition module and is used for performing sensitivity verification, if +.>The sensitivity check passes, otherwise, the check does not pass; the display processing module is respectively connected with the acquisition module, the first processing module, the second processing module and the third processing module and is used for displaying the verification result; if any one of the checks fails, the check is required to be returned to the acquisition module again for acquisition and the subsequent check is carried out again; if both checks pass, the ratio differential check is considered to pass.
Compared with the prior art, the invention has the beneficial effects that: in general, in the verification of bus differential ratio and differential protection in the field, the selected branch does not exceed three branches, and in a specific environment, multiple branches are required to be connected for bus differential element ratio verification, so that a great amount of time is required for a technician to calculate. By calculating and verifying differential current and braking current of multi-branch compound differential protection, the working efficiency is improved, test lines are reduced, and the safety risk of a power grid is reduced.
Drawings
FIG. 1 is a schematic diagram of a multiple ratio differential verification method under a multiple distributed new energy access feeder;
FIG. 2 is a graph showing the operational characteristics of a multiple ratio differential element;
FIG. 3 is a logic diagram of the current of each loop in case of branch fault;
FIG. 4 is a logic diagram of the current of each branch when the bus fails;
fig. 5 is a schematic structural diagram of a multiple ratio differential check device under a multi-distributed new energy access feeder.
Detailed Description
The present invention will be described in further detail with reference to examples.
It will be appreciated by those skilled in the art that the following examples are illustrative of the present invention and should not be construed as limiting the scope of the invention. The specific techniques or conditions are not identified in the examples and are performed according to techniques or conditions described in the literature in this field or according to the product specifications. The materials or equipment used are conventional products available from commercial sources, not identified to the manufacturer.
The embodiment 1 is that a multiple ratio differential verification method under a multi-distributed new energy access feeder line comprises ratio differential protection mobility verification, ratio differential protection reliability stability verification and ratio differential protection sensitivity verification; the method comprises the following steps:
the first step: calculating a theoretical compound ratio Kr; collecting an actual compound ratio setting value Kr';
And a second step of: the ratio differential protection mobility check is: comparing Kr with an actual compound ratio set value Kr ', and judging that the quick action verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
and a third step of: the reliable stability check of the ratio differential protection is as follows: acquisition of CT saturation induced propagation errors for faulty branchesThen, reliable stability check is carried out, if +.>Checking passing, otherwise, checking failing;
fourth step: the ratio differential protection sensitivity check is: acquiring the ratio Ext of the current flowing out of the bus to the total fault current, and then performing sensitivity verification ifThe sensitivity check passes, otherwise, the check does not pass;
fifth step: in the second step, the third step and the fourth step, when any one of the verification passes, the first step is required to be returned, the compound ratio Kr calculation is carried out again, and when the verification passes in the second step, the third step and the fourth step, the ratio differential verification is considered to pass.
The embodiment 2 is that the multiple ratio differential verification method under the multi-distributed new energy access feeder line comprises ratio differential protection mobility verification, ratio differential protection reliability stability verification and ratio differential protection sensitivity verification; the method comprises the following steps:
The first step: calculating a theoretical compound ratio Kr; collecting an actual compound ratio setting value Kr';
and a second step of: the ratio differential protection mobility check is: comparing Kr with an actual compound ratio set value Kr ', and judging that the quick action verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
and a third step of: the reliable stability check of the ratio differential protection is as follows: acquisition of CT saturation induced propagation errors for faulty branchesThen, reliable stability check is carried out, if +.>Checking passing, otherwise, checking failing;
fourth step: the ratio differential protection sensitivity check is: acquiring the ratio Ext of the current flowing out of the bus to the total fault current, and then performing sensitivity verification ifThe sensitivity check passes, otherwise, the check does not pass; fifth step: in the second step, the third step and the fourth step, when any one of the verification passes, the first step is required to be returned, the compound ratio Kr calculation is carried out again, and when the verification passes in the second step, the third step and the fourth step, the ratio differential verification is considered to pass.
When the reliability and stability verification of the ratio differential protection is carried out, the fault condition outside the bus area needs to be simulated, and the specific method is as follows:
1) Optionally, two branches with the same transformation ratio on the same bus are added with a certain phase of current at the same time, wherein the currents are equal in magnitude and opposite in direction;
2) The bus differential protection should not act;
3) The large and small difference currents should be equal to zero.
When the sensitivity check of the ratio differential protection is carried out, the fault condition in the bus area needs to be simulated, and the specific method comprises the following steps:
step (1), verifying a differential threshold fixed value:
a) Optionally adding a certain current into a certain phase of a branch on the bus, wherein the current is larger than a differential threshold constant value;
b) The bus differential protection should act instantaneously, cut off the bus and all branches on the bus where this branch is located, the bus differential action signal lamp should be on;
step (2), verifying that the differential ratio coefficient is high:
a) The bus-tie switch is closed;
b) Optionally, two branches with the same transformation ratio are arranged on the bus I, and currents with opposite directions are added in a certain phase; c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio high-value coefficient;
step (3), verifying that the differential ratio coefficient is low:
a) The bus is switched off;
b) Optionally, two branches with the same transformation ratio are arranged on the I bus, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio low value coefficient;
step (4), verifying a small difference ratio coefficient:
a) Optionally selecting two branches with the same transformation ratio on the same bus, and adding currents with opposite directions and different magnitudes on a certain phase;
b) Fixing the current of one branch, and adjusting the current of the other branch to make the bus act differentially;
c) The applied current was recorded and the small difference ratio coefficient was verified.
In the step (2), the specific method for verifying the differential ratio high value coefficient is as follows:
the differential ratio high value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is combined, the sum of all branch current vectors except the bus is combined;I r the brake current is the sum of absolute values of all branches;
；
wherein,representation->Current transformer transformation ratio of branch circuit; />Secondary current quantity for each corresponding branch; />In the differential motion, inLxThe amount of current added by the branch; s represents a reference transformation ratio; If the equation is true, the verification is passed. In the step (3), the specific method for verifying the differential ratio low value coefficient is as follows:
differential ratio low value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is disconnected, the sum of all branch current vectors on the bus;I r for braking current, all branchesSum of way absolute values; />If the equation is true, the verification is passed. In the step (4), the specific method for verifying the small difference ratio coefficient is as follows: />Representing the coefficient of the small difference ratio,Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: the sum of all branch current vectors on the I or II bus,I r for the braking current, the sum of the absolute values of all branches of the I or II master is +.>If the equation is true, the verification is passed. When the sensitivity verification of the ratio differential protection is carried out, the fault condition in the bus area in the double bus switching operation process is also required to be simulated, and the specific method is as follows:
1) Optionally, a branch on a certain bus is closed, and a mother I and a mother II of the branch are closed;
2) Loading a single-phase current in the branch, wherein the current value is larger than the differential threshold fixed value;
3) The bus differential protection should act instantaneously, cutting off the bus and all branches on the bus;
4) I and II are differential to turn on the signal lamp.
The embodiment 3 is that the multiple ratio differential verification method under the multi-distributed new energy access feeder line comprises ratio differential protection mobility verification, ratio differential protection reliability stability verification and ratio differential protection sensitivity verification; the method comprises the following steps:
the first step: calculating a theoretical compound ratio Kr; collecting an actual compound ratio setting value Kr';
and a second step of: the ratio differential protection mobility check is: comparing Kr with an actual compound ratio set value Kr ', and judging that the quick action verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
third stepStep (c) of: the reliable stability check of the ratio differential protection is as follows: acquisition of CT saturation induced propagation errors for faulty branchesThen, reliable stability check is carried out, if +.>Checking passing, otherwise, checking failing; fourth step: the ratio differential protection sensitivity check is: acquiring the ratio Ext of the current flowing out of the bus to the total fault current, and then performing sensitivity verification, if +.>The sensitivity check passes, otherwise, the check does not pass; fifth step: in the second step, the third step and the fourth step, when any one of the verification passes, the first step is required to be returned, the compound ratio Kr calculation is carried out again, and when the verification passes in the second step, the third step and the fourth step, the ratio differential verification is considered to pass.
When the reliability and stability verification of the ratio differential protection is carried out, the fault condition outside the bus area needs to be simulated, and the specific method is as follows:
1) Optionally, two branches with the same transformation ratio on the same bus are added with a certain phase of current at the same time, wherein the currents are equal in magnitude and opposite in direction;
2) The bus differential protection should not act;
3) The large and small difference currents should be equal to zero.
When the sensitivity check of the ratio differential protection is carried out, the fault condition in the bus area needs to be simulated, and the specific method comprises the following steps:
step (1), verifying a differential threshold fixed value:
a) Optionally adding a certain current into a certain phase of a branch on the bus, wherein the current is larger than a differential threshold constant value; b) The bus differential protection should act instantaneously, cut off the bus and all branches on the bus where this branch is located, the bus differential action signal lamp should be on;
step (2), verifying that the differential ratio coefficient is high:
a) The bus-tie switch is closed;
b) Optionally, two branches with the same transformation ratio are arranged on the bus I, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio high-value coefficient;
step (3), verifying that the differential ratio coefficient is low:
a) The bus is switched off;
b) Optionally, two branches with the same transformation ratio are arranged on the I bus, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio low value coefficient;
step (4), verifying a small difference ratio coefficient:
a) Optionally selecting two branches with the same transformation ratio on the same bus, and adding currents with opposite directions and different magnitudes on a certain phase;
b) Fixing the current of one branch, and adjusting the current of the other branch to make the bus act differentially;
c) The applied current was recorded and the small difference ratio coefficient was verified.
In the step (2), the specific method for verifying the differential ratio high value coefficient is as follows: the differential ratio high value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is combined, the sum of all branch current vectors except the bus is combined;I r the brake current is the sum of absolute values of all branches;
；
wherein,representation ofLnCurrent transformer transformation ratio of branch circuit; />Secondary current quantity for each corresponding branch; / >In the differential motion, inLxThe amount of current added by the branch; s represents a reference transformation ratio;if the equation is true, the verification is passed.
In the step (3), the specific method for verifying the differential ratio low value coefficient is as follows:
differential ratio low value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is disconnected, the sum of all branch current vectors on the bus;I r the brake current is the sum of absolute values of all branches; />If the equation is true, the verification is passed.
In the step (4), the specific method for verifying the small difference ratio coefficient is as follows:representing the coefficient of the small difference ratio,Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: the sum of all branch current vectors on either the I or II bus,I r the braking current is the sum of absolute values of all branches of the I master or the II master; />If the equation is true, the verification is passed. In the fourth step, < >>The value range is more than or equal to 1.5 and less than or equal to 3, preferably, the value range is>The value is 2.
As shown in fig. 5, the multiple ratio differential check device under the multiple distributed new energy access feeder line adopts the multiple ratio differential check method under the multiple distributed new energy access feeder line, and includes:
An acquisition module 101 for acquiring the actual complex ratio set value Kr', and the transmission error caused by CT saturation of the fault branchThe ratio of the current flowing out of the bus to the total fault current exists; the first processing module 102 is connected with the acquisition module 101 and is used for calculating a theoretical compound ratio Kr, then carrying out ratio differential protection mobility verification, comparing Kr with an actual compound ratio set value Kr ', and judging that the mobility verification passes if the Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
a second processing module 103 connected to the acquisition module 101 for performing reliability and stability verification ifChecking passing, otherwise, checking failing; a third processing module 104, connected to the acquisition module 101, for performing a sensitivity check, if +.>The sensitivity check passes, otherwise, the check does not pass; the display processing module 105 is respectively connected with the acquisition module 101, the first processing module 102, the second processing module 103 and the third processing module 104 and is used for displaying the verification result; if any check fails, the system needs to return to the acquisition module 101 again for acquisition and perform subsequent check again; if both checks pass, the ratio differential check is considered to pass.
Embodiment 4 the multiple ratio differential verification method under the multi-distributed new energy access feeder line of the invention mainly verifies the four properties of the protection device: the method for checking the bus fault current comprises the steps of checking the composite ratio (the slope Kr of a boundary line between an action area and a brake area, as shown in figure 2), checking the speed of the differential protection, avoiding a transmission error delta caused by the saturation of a fault branch CT (namely, checking the reliability and the stability of the differential protection), and the proportion Ext of the fault current of a flowing bus to the total current of the bus (namely, checking the sensitivity of the differential protection).
The following describes the verification method in detail for these 3 key indexes:
A. multi-branch compound ratio brake ratio calculation:
for bus compound ratio differential large-difference ratio verification of multiple branches, one branch of two sections of buses is selectedLxAs differential branch, the initial current value is 0A, then all the branches remained on the two buses are taken as a whole, the branch flowing out of the buses isIm, the branch flowing into the bus is as a whole In, and let flow outIm is equal toIn is equal in magnitude and finally is atLx
Adding secondary current quantity to the branch circuit until the differential action lamp is lighted, wherein the added secondary current quantity is the action current quantity of differential protectionId，Secondary brake current flow as differential protectionIrWherein, the method comprises the steps of, wherein,Ixrepresenting a newly added current value of a certain phase, the current value being a vector, which can be obtained byLxThe secondary current value added on the upper part is used for calculating the large difference ratio, and if the large difference ratio is known, the large difference ratio can also be calculatedLxThe secondary current value to be added is specifically as follows: 1) As shown in fig. 1, it is assumed that the branch current outflow bus is positive, i.e., 0 degrees; the branch current flowing into the bus is negative, namely 180 degrees,Ixwithout application.
The current of the bus-tie branch circuit flows from I busTo the mother II, the secondary current value before each branch is not converted satisfies the formula (1), whenIxWith the application.
The current of the bus-tie branch flows from the I bus to the II bus, and the secondary current value before each branch is not converted satisfies the formula (2), specifically as follows:
wherein:
branch circuitL1Is a double bus connecting circuit, a branch circuitL2Branch circuitL3Branch circuitL4… branchLnThe feeder line branch circuit is a feeder line branch circuit of distributed photovoltaic access. Branch circuitLxBranch for testing applied quantity。
Secondary current quantity for each corresponding branch; 1) Assume that L X The initial current of the branch is 0A, the branchL2Branch circuitL1And branch circuitL4+L5+L6...LnThe current amplitude is the same and,L2and (3) withL4+L5+L6...LnIs opposite in phase.
2) In the branchL3And branch circuitL4+L5+L6...LnAdding current amounts with equal amplitude and opposite phases.
On the I bus and the II bus except the bus connection branch, the bus flows inL2、L3The primary current of the branch is equal to the outflow busL4、L5、L6...LnThe primary current amount of the branch circuit satisfies the formula:
i.e. the bus differential protection current is zero at this time.
Representing feeder->Current transformer transformation ratio of branch circuit, +.>Representing feeder->Current transformer ratio of branch, and the like, < ->Representing feederLnThe transformation ratio of the current transformer of the branch, S represents the reference transformation ratio.
3) At the position ofLxOn the branch, the step size is set to 0.01A from the initial secondary current amount of 0A, the current amount is gradually increased until the protection device is operated with big differenceLxThe added current is the differential action。
4) Bus large difference braking current amountIrThe secondary current of each branch on the I bus and the II bus is the sum of absolute value currents converted by the reference transformation ratio except the branch of the bus.
I.e.Knowing the inflow bus from 2) -4)L2、L3The secondary current quantity of the branch circuit is equal to the outflow busL4、L5、L6...LnThe amount of current in the branch, i.e I r For the amount of braking current;the transformation ratio of the current transformer corresponding to each branch is; / >The reference transformation ratio of the current transformer;for the secondary current quantity of each branch.
In the differential motion, inLxThe amount of current added by the branch; id is the amount of action current; 5) Thereby, can obtain:
wherein,a differential ratio high value coefficient representing a high value ratio of a large difference;Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is combined, the sum of all branch current vectors except the bus is combined;I r the brake current is the sum of absolute values of all branches; />Wherein (1)>A differential ratio low value coefficient representing a low value ratio of a large difference;Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the busbar is disconnected, the sum of all branch current vectors on the independent busbar is calculated;I r the brake current is the sum of absolute values of all branches; />Wherein (1)>Is a watchA small difference ratio coefficient is shown and,Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: the sum of all branch current vectors on the bus-bar and the individual bus-bars,I r the brake current is the sum of absolute values of all branches; />，/>According to the calculation of the I parent or the II parent, the action current Id is different, and the calculation formula is not repeated.
B. Consider the transmission error caused by CT saturation of fault branch when internal and external faults of bus area δ(%): if the transmission error caused by CT saturation of the fault branch is considered to be the out-of-zone faultδWhile CT errors of the rest branches are ignored，/>Thus (2)。
As shown in FIG. 3, when the bus inflow current is 1, the differential current loop current isFault branch current is +.>。
According to the action criterion of the compound ratio differential relay, the differential action must be satisfied in order to ensure that the differential action is not false when the fault is out of the zoneI.e. +.>The bus compound ratio differential protection secondary wiring under normal condition is connected with the special protection level winding, namelyA 5P-level protection winding and a 10P-level protection winding, wherein the transmission error limit caused by the saturation of the 5P-level protection winding is 5%,
i.e.δ=5%，Kr>0.05/(2-0.10)=2.63%；
The transmission error limit caused by the saturation of the 10P-level protection winding is 10%,
i.e.δ=10%，Kr>0.1/(2-0.20)=5.56%。
C. When considering the fault in the zone, the ratio of the fault current of the outgoing bus to the total current of the bus exists (%): if the ratio of the current flowing out of the bus to the total fault current is Ext when considering the fault in the zone, letIdIf=1, thenIr=1+ext; as shown in fig. 4, when a fault occurs in the bus, if the total current of the bus fault differential loop is 1 and the current flowing out of a certain branch of the bus is Ext, the current flowing into the rest of the branches is 1+ext.
According to the action criterion of the compound ratio differential relay, the differential action must be satisfied in order to ensure the fault in the zone I.e. +.>I.e. +.>The secondary wiring of the bus compound ratio differential protection is connected into the corresponding junction box without error under the normal condition, the compound bus compound ratio differential protection needs higher sensitivity, the existing outgoing bus fault current accounts for the ratio Ext of the total bus current, and the value interval is generally more than or equal to 10 percent and less than or equal to 15 percent, namely more than or equal to 3.33 and less than or equal to 5 percent;
this factor need not be taken into account when considering a bus out fault.
The calculation and value-taking methods of the 3 key indexes are discussed above, and are shown in formulas (6) - (10).
Formulas (6) - (10) need to be considered simultaneously when checking the faults in the bus compound ratio differential area, and formulas (6) - (9) need to be considered simultaneously when checking the faults outside the bus compound ratio differential area.
Application example: 5 branches are chosen as an example, as shown in fig. 1.
It is known that: assuming that the branch inflow bus is negative, the branch outflow bus is positive, and the branch transformation ratios are respectively:L1=2000/5；L2=2000/5；L3=1000/5；L4=2500/5；Lx=2500/5; the reference transformation ratio was 2500/5. If the secondary currents of L2 and L4 are the same current Y and the secondary current value of the L3 branch is Z, if the current amounts of the L2, L3 and L4 branches are balanced, the primary current value balance of the three branches needs to be satisfied firstly, namely, the balance is calculated by the formula Yielding 400y+200z=500y, i.e. y=2z;
at this time, the secondary current added by the L2 branch is 1A, and the secondary current of the L4 branch is 1A, which is known from the previous analysis=x, X is an argument; />From the ratio formula->Meanwhile, according to different CT protection level winding accuracy grades and different bus-bar protection sensitivities, proper delta and Ext are selected, so that three key indexes can be checked rapidly.
Testing soft and hard pressing plates and control words: 1) Testing the influence of a soft pressing plate and a hard pressing plate and a control word on protection:
the technical requirements are as follows: when both the soft and hard pressing plates and the control words are thrown, the protection can act.
The testing method comprises the following steps: inputting a differential soft pressing plate, a hard pressing plate and control words, wherein the adding amount meets the differential protection action condition, and observing the action condition of the device; and respectively withdrawing the soft pressing plate, the hard pressing plate and the control word, and observing whether the protection acts (if the X value is modified and the calculation is performed again until the calculation is satisfied, which is different from the theoretical result).
The test records are shown in Table 1.
TABLE 1
| Test conditions | Theoretical results |
| Hard platen=1, control word=1, soft platen=1 | Differential motion |
| Hard platen=0, control word=1, soft platen=1 | Differential non-action |
| Hard platen=1, control word=0, soft platen=1 | Differential non-action |
| Hard platen=1, control word=1, soft platen=0 | Differential non-action |
2) And (3) checking a mother-difference compound ratio differential threshold value:
the technical requirements are as follows: the error of the action value is not more than 3%.
The testing method comprises the following steps: the setting value Idset is 0.1In (In is rated current, 0.1In represents 0.1 times of rated current), the x-th interval is positioned In the I parent, the x-interval single-phase current is added by 0.95 times of Idset, the current value is continuously increased, the current maximum value is 1.05 times of Idset, the action condition of ratio differential is observed, whether the action is performed In (0.97-1.03) Idset is observed, if the action is performed, the action value error is not more than 3%, and otherwise, the error requirement is not met.
If the differential ratio is known, the value of the branch X is only greater than 2A, i.e. the differential protection action, when k=1, and the value of the branch X is only greater than 1A, i.e. the differential protection action, and so on, the magnitude of the current of the X branch can be known quickly and efficiently. If the differential ratio is not known, the secondary current can be gradually added to the X branch, so that the current value of the differential action is brought into the ratio formula, and the ratio value of the differential element can be rapidly obtained.
The bus differential protection checking and debugging process comprises the following steps: 1. simulating bus zone external fault conditions: no voltage is applied to turn on the "blocked-open" lamp:
1) Optionally, two branches with the same transformation ratio on the same bus are added with current of phase A (or phase B or phase C) at the same time, and the current is equal in magnitude (1-10A) and opposite in direction;
2) The bus differential protection should not act;
3) In the observation panel display: the large and small difference currents should be equal to zero.
2. Simulating fault conditions in the bus area: no voltage is applied to turn on the "blocked-open" lamp:
1) Verifying a differential threshold constant value:
a) Optionally adding a branch on the bus, wherein the B-phase current is added in the branch, and the current value is larger than the differential threshold fixed value; b) The bus differential protection should act instantaneously, cut off the bus and all branches on the bus where this branch is located, the bus differential action signal lamp should be on;
2) Verifying a differential ratio coefficient high value:
a) The master switch is closed (only the normally open contact of the master switch is positively charged);
b) Optionally, two branches with the same transformation ratio on the bus I are added with currents with opposite directions in the phase A;
c) And then optionally adding current into the phase A by selecting a branch with the same transformation ratio on the bus II, regulating the current to make the bus II act in a differential mode, and uniformly converting by taking the maximum transformation ratio as a reference if the transformation ratios are different. For example: main transformation ratio: 600/5; line transformation ratio: 1600/5; the coefficient ratios of each side are as follows: 600/1600=0.375: 1.
d) The applied current is recorded and the differential ratio high value coefficient is verified.
3) Validating the differential ratio coefficient low value:
a) The bus switch is turned off (only the normally-closed contact of the bus switch is positively charged);
b) Optionally adding current with opposite directions into the phase A by two branches with the same transformation ratio on the bus I;
c) Then, optionally adding current into the phase A by a branch with the same transformation ratio on the bus II, and regulating the current so as to enable the bus II to act in a differential mode;
d) The applied current is recorded and the differential ratio low value coefficient is verified.
4) Verifying a small difference ratio coefficient:
a) Optionally, two branches with the same transformation ratio on the same bus are added with currents with opposite directions and different magnitudes in the phase A;
b) Fixing the current of one branch, and adjusting the current of the other branch to make the bus act differentially;
c) The applied current was recorded and the small difference ratio coefficient was verified.
3. Simulating fault conditions in a bus area in the double-bus switching operation process: no voltage is applied to turn on the "blocked-open" lamp:
1) Optionally, a branch on a certain bus is closed, and a mother I and a mother II of the branch are closed;
2) Loading C-phase current in the branch, wherein the current value is larger than the differential threshold fixed value;
3) The bus differential protection should act instantaneously, cutting off the bus and all branches on the bus;
4) I and II are differential to turn on the signal lamp.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. The multiple ratio differential verification method under the multi-distributed new energy access feeder line is characterized by comprising ratio differential protection mobility verification, ratio differential protection reliability stability verification and ratio differential protection sensitivity verification; the method comprises the following steps:
the first step: calculating a theoretical compound ratio Kr; collecting an actual compound ratio setting value Kr';
and a second step of: the ratio differential protection mobility check is: comparing Kr with an actual compound ratio set value Kr ', and judging that the quick action verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
And a third step of: the reliable stability check of the ratio differential protection is as follows: acquisition of CT saturation induced propagation errors for faulty branchesδThen, reliable stability verification is carried out, ifChecking passing, otherwise, checking failing;
fourth step: the ratio differential protection sensitivity check is: acquiring the ratio Ext of the current flowing out of the bus to the total fault current, and then performing sensitivity verification ifThe sensitivity check passes, otherwise, the check does not pass;
fifth step: in the second step, the third step and the fourth step, when any one of the verification passes, the first step is required to be returned, the compound ratio Kr calculation is carried out again, and when the verification passes in the second step, the third step and the fourth step, the ratio differential verification is considered to pass.
2. The multiple ratio differential verification method under the multiple distributed new energy access feeder line according to claim 1, wherein when the ratio differential protection reliability and stability verification is performed, the fault condition outside the bus area needs to be simulated, and the specific method is as follows:
1) Optionally, two branches with the same transformation ratio on the same bus are added with a certain phase of current at the same time, wherein the currents are equal in magnitude and opposite in direction;
2) The bus differential protection should not act;
3) The large and small difference currents should be equal to zero.
3. The multiple ratio differential verification method under the multi-distributed new energy access feeder line according to claim 1, wherein the fault condition in the bus area needs to be simulated when the ratio differential protection sensitivity verification is performed, the specific method comprises the following steps:
step (1), verifying a differential threshold fixed value:
a) Optionally adding a certain current into a certain phase of a branch on the bus, wherein the current is larger than a differential threshold constant value;
b) The bus differential protection should act instantaneously, cut off the bus and all branches on the bus where this branch is located, the bus differential action signal lamp should be on;
step (2), verifying that the differential ratio coefficient is high:
a) The bus-tie switch is closed;
b) Optionally, two branches with the same transformation ratio are arranged on the bus I, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio high-value coefficient;
step (3), verifying that the differential ratio coefficient is low:
a) The bus is switched off;
b) Optionally, two branches with the same transformation ratio are arranged on the I bus, and currents with opposite directions are added in a certain phase;
c) Then, selecting a branch with the same transformation ratio on the II bus, adding current to the certain phase, and regulating the current to make the II bus act in a differential mode;
d) Recording the applied current, and verifying the differential ratio low value coefficient;
step (4), verifying a small difference ratio coefficient:
a) Optionally selecting two branches with the same transformation ratio on the same bus, and adding currents with opposite directions and different magnitudes on a certain phase;
b) Fixing the current of one branch, and adjusting the current of the other branch to make the bus act differentially;
c) The applied current was recorded and the small difference ratio coefficient was verified.
4. The multiple ratio differential verification method under a multi-distributed new energy access feeder line according to claim 3, wherein in the step (2), the specific method for verifying the differential ratio high value coefficient is as follows:
the differential ratio high value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is combined, the sum of all branch current vectors except the bus is combined;I r the brake current is the sum of absolute values of all branches;
；
wherein,representation->Current transformer transformation ratio of branch circuit; />Secondary current quantity for each corresponding branch; />In the differential motion, inLxThe amount of current added by the branch; s represents a reference transformation ratio; If the equation is true, the verification is passed.
5. The multiple ratio differential verification method under a multi-distributed new energy access feeder line according to claim 3, wherein in the step (3), the specific method for verifying the differential ratio low value coefficient is as follows:
differential ratio low value coefficient is，IdThe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: after the bus is disconnected, the sum of all branch current vectors on the bus;I r the brake current is the sum of absolute values of all branches; />If the equation is true, the verification is passed.
6. The multiple ratio differential verification method under a multi-distributed new energy access feeder line according to claim 3, wherein in the step (4), the specific method for verifying the small difference ratio coefficient is as follows:representing the coefficient of the small difference ratio,Idthe amount of operating current for differential protection; at this time, the liquid crystal display device,Idthe calculation method of (1) is as follows: the sum of all branch current vectors on the I or II bus,I r the brake current is the sum of absolute values of all branches of the I master or the II master; />If the equation is true, the verification is passed.
7. The multiple-distributed new energy access feeder line lower compound ratio differential verification method according to claim 1, wherein when the ratio differential protection sensitivity verification is performed, the fault condition in the bus area in the double bus switching operation process is also required to be simulated, and the specific method is as follows:
1) Optionally, a branch on a certain bus is closed, and a mother I and a mother II of the branch are closed;
2) Loading a single-phase current in the branch, wherein the current value is larger than the differential threshold fixed value;
3) The bus differential protection should act instantaneously, cutting off the bus and all branches on the bus;
4) I and II are differential to turn on the signal lamp.
8. The multiple distributed new energy access feeder lower compound ratio differential verification method of claim 1, wherein in the fourth step,the value range is more than or equal to 1.5 and less than or equal to 3.
9. The multiple distributed new energy access feeder lower compound ratio differential verification method of claim 8, wherein,the value is 2.
10. The multiple ratio differential verification device under a multiple distributed new energy access feeder line adopts the multiple ratio differential verification method under the multiple distributed new energy access feeder line as claimed in any one of claims 1 to 9, and is characterized by comprising the following steps:
the acquisition module is used for acquiring the actual complex ratio set value Kr' and the transmission error caused by CT saturation of the fault branchδThe ratio of the current flowing out of the bus to the total fault current exists;
the first processing module is connected with the acquisition module and is used for calculating theoretical compound ratio Kr, then carrying out ratio differential protection mobility verification, comparing Kr with an actual compound ratio set value Kr ', and judging that the mobility verification passes if Kr is equal to the actual compound ratio set value Kr'; if Kr is greater than or less than the actual complex ratio setting value Kr', judging that the quick action check is not passed;
The second processing module is connected with the acquisition module and is used for carrying out reliable stability verification ifChecking passing, otherwise, checking failing;
a third processing module connected with the acquisition module for performing sensitivity verification ifThe sensitivity check passes, otherwise, the check does not pass;
the display processing module is respectively connected with the acquisition module, the first processing module, the second processing module and the third processing module and is used for displaying the verification result; if any one of the checks fails, the check is required to be returned to the acquisition module again for acquisition and the subsequent check is carried out again; if both checks pass, the ratio differential check is considered to pass.
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