CN111769523A - Double-circuit line inverse time limit zero sequence current protection setting method containing series compensation - Google Patents
Double-circuit line inverse time limit zero sequence current protection setting method containing series compensation Download PDFInfo
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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
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
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Abstract
The invention provides a double-circuit line inverse time-limit zero-sequence current protection setting method with series compensation, which comprises the following steps: s1, determining an inverse time limit zero sequence current protection double-circuit line containing series compensation to be set; s2, judging whether the reverse time-limit zero-sequence current protection is in misoperation, if so, executing a step S3; otherwise, executing the step S4 according to the conventional inverse time limit zero sequence current protection step-by-step setting method; s3, judging whether the reverse time limit zero sequence current protection misoperation is the upper and lower level protection misoperation of the reverse time limit zero sequence current at the side of the series compensation, if so, determining a setting check point matched with the upper and lower level protection of the reverse time limit zero sequence current at the side of the series compensation; otherwise, the reverse time-limited zero-sequence current protection malfunction occurs on the opposite side of the series compensation, and the upper protection starting current is set; s4, setting a lower-level protection time constant on the double-circuit line; s5, setting a superior protection time constant on the double-circuit line; and S6, outputting a setting result. The invention solves the problem of double-circuit line protection misoperation containing series compensation and ensures the selectivity requirement of protection action.
Description
Technical Field
The invention relates to the technical field of inverse time-limit zero-sequence protection setting, in particular to a method for setting inverse time-limit zero-sequence current protection of a double-circuit line with series compensation.
Background
With the explosion of social economy, the transmission power of the power system is increasing. In actual extra-high voltage transmission system engineering, a series compensation device (referred to as series compensation for short) is usually installed on the basis of long-distance double-circuit line transmission to reduce the impedance of a transmission line, improve the transmission capacity limit of the transmission line and enhance the safety and stability of a power system.
In these high-voltage transmission lines, inverse time-limited zero-sequence current protection is usually adopted as backup protection to simplify the matching process of the traditional multi-stage setting of the fixed time-limited protection, and the action time of the upper and lower-stage protection is ensured by a step-by-step setting method to meet the requirement of selectivity.
Chinese patent with publication number CN106711968A and publication number 2017, 5, month 24 discloses a setting method and system for inverse time-limit zero-sequence current protection, which solves the problem that automatic setting can not be realized all the time due to the fact that the inverse time-limit zero-sequence current protection setting involves many matching elements and is influenced by operation modes, ensures the quick action and selectivity of relay protection, improves the working efficiency, however, the precondition requirement of the technical scheme for realizing the normal work of the inverse time-limit zero-sequence current protection is that the parameters of the power transmission line are uniformly distributed, and in the actual engineering, the series compensation device is installed on the basis of long-distance double-circuit line power transmission, the series compensation has the impedance characteristic of centralized parameters, the double-circuit line containing the series compensation destroys the uniformity of line impedance distribution, this will affect the coordination of the inverse time-lag zero-sequence protection, causing the malfunction consequences of the upper and lower level protection.
Disclosure of Invention
In order to overcome the defect that the double-circuit line containing series compensation damages the uniformity of the impedance distribution of the line to cause the malfunction of upper and lower-level protection, the invention discloses a method for setting the inverse time-limit zero-sequence current protection of the double-circuit line containing series compensation, which prevents the malfunction of the inverse time-limit zero-sequence current protection caused by the series compensation and ensures the selectivity requirement of the protection action.
In order to achieve the technical effects, the technical scheme of the invention is as follows:
a method for protecting and setting the inverse time limit zero sequence current of a double-circuit line containing series compensation at least comprises the following steps:
s1, determining an inverse time limit zero sequence current protection double-circuit line containing series compensation to be set;
s2, judging whether the reverse time-limit zero-sequence current protection is in misoperation, if so, executing a step S3; otherwise, executing the step S4 according to the conventional inverse time limit zero sequence current protection step-by-step setting method;
s3, judging whether the inverse time-limit zero-sequence current protection misoperation is the upper and lower level misoperation of the inverse time-limit zero-sequence current protection on the side of the series compensation, and if so, determining a setting check point matched with the upper and lower level protection of the inverse time-limit zero-sequence current on the side of the series compensation; otherwise, the reverse time-limited zero-sequence current protection malfunction is the upper and lower protection malfunction of the reverse time-limited zero-sequence current at the opposite side of the series compensation, and the upper protection starting current is set;
s4, setting a lower-level protection time constant on the double-circuit line;
s5, setting a superior protection time constant on the double-circuit line;
and S6, outputting a setting result of the anti-time-limit zero-sequence current protection of the double-circuit line with the series compensation.
The time of the inverse time-limited zero-sequence current protection action is changed along with the change of the magnitude of the fault zero-sequence measurement current, the fault adaptability is strong, and the conventional inverse time-limited zero-sequence current protection action characteristic t (I)M0) The formula of (1) is:
wherein, IM0For protection of the measurement current, the value is 3 times the zero sequence current, T, flowing through the protectionPIs a time constant, IPTo protect the starting current; in the conventional inverse time limit zero sequence current protection step-by-step setting method, the time constant T is setPAnd protection of the starting current IPRespectively setting: starting current IPSetting an unbalanced current which needs to be avoided when the line normally runs; time constant TPSetting meets the requirement that the upper and lower stage protection action time difference is guaranteed to be a set time difference delta t larger than zero at the most difficult-to-match setting check point, and the upper and lower stage protection action time is naturally matched along with the uniform distribution of line impedance according to the time current action characteristic of inverse time limit protection, so that the selectivity of upper and lower stage protection can be ensured.
The lower protection outlet fault point is used as the setting check point which is most difficult to be matched with the upper and lower protection, and when the setting check point of the upper and lower protection is in fault, the upper protection acts for a time teIs shorter than the lower level protection operation time tsOne more fixed time step Δ t, the formula is:
te＝ts+Δt
wherein the upper protection time constant is determined by the protection action time teDetermination of teIndicates the upper level protection operation time, tsRepresents the lower protection operation time, and Δ t represents the set time level difference; the two protections have the minimum action time difference when the upper and lower protection has a fault at the setting check point, and the two protections are far away from one end of the protection along with the fault pointThe action time difference is naturally prolonged, the condition that the protection action time difference is smaller than the set time step difference delta t can not occur, so the time is set according to the conventional inverse time limit zero sequence current protection step-by-step setting method, and the setting of the upper protection time constant adopts the upper protection action time teAnd (6) setting.
Preferably, the staff judges whether the inverse time-lag zero-sequence current protection is in misoperation or not by analyzing the fault zero-sequence current distribution condition when the earth fault occurs on the double-circuit line containing the series compensation; the ratio of the impedance value of the series compensation installation position to the impedance value of one end of the double-circuit line to the impedance value of the whole length of the line is kCWherein k isCLess than 50 percent; two protections of a line adjacent to one end with the distance a from the installation position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation, two protections of a line adjacent to one end with the distance b from the installation position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation, wherein b>a; the anti-time-limit zero-sequence current protection misoperation comprises upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is located and upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is located.
Here, b > a also indicates that two adjacent line protections at one end close to the mounting position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation, and two adjacent line protections at one end far away from the mounting position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation.
Preferably, when the fault zero-sequence current of the lower-stage protection outlet installed on the double-circuit line is smaller than the fault zero-sequence current of the series compensation outlet, the upper-stage protection action time difference delta t and the lower-stage protection action time difference delta t of the side inverse time-limit zero-sequence current of the series compensation outletLAnd when the time level difference delta t is less than the set time level difference, the upper and lower level protection misoperation of the side inverse time limit zero sequence current of the series compensation position occurs, namely the upper and lower level protection misoperation occurs on the series compensation outlet section line.
Preferably, when the lower-level protection zero-sequence measurement current installed on the double-circuit line is smaller than the zero-sequence protection starting current and the upper-level protection zero-sequence measurement current is larger than the zero-sequence protection starting current, the upper-level and lower-level protection action time difference delta t of the opposite-side inverse time-limited zero-sequence current is compensated in seriesRLess than a set time step delta t, series compensation contralateral reaction occursThe time limit zero sequence current upper and lower level protection is malfunction.
Preferably, when the reverse time-limit zero-sequence current protection malfunction is the upper and lower level protection malfunction of the reverse time-limit zero-sequence current at the side of the series compensation, the zero-sequence measurement current I for protecting the outlet fault on the double-circuit line is selectedrAnd zero sequence measurement current I of series compensation outlet fault on double-circuit linecThe larger one of the two is used as a setting check point of the upper-level protection and the lower-level protection of the side inverse time limit zero sequence current of the series compensation place, namely, the setting check point passes through:
Is＝max(Ir,Ic)
wherein, IsRepresenting the setting current of the head end of the lower protection on the double-circuit line at the setting check point; i isrRepresenting the fault zero-sequence measurement current of a protection outlet on the double-circuit line; i iscAnd the zero sequence measurement current of the series compensation outlet fault on the double-circuit line is shown.
Preferably, when the inverse time-limited zero-sequence current protection malfunction is a series compensation opposite inverse time-limited zero-sequence current upper and lower level protection malfunction, the protection setting action time satisfies:
ts+Δt＝min(tr+Δt,tc+Δt)
wherein, tsProtecting and setting action time for the head end of the lower-level protection on the double-circuit line at the protection and setting check point; delta t is the step difference of the fixed time; t is trRepresenting the protection action time of the fault of the protection outlet on the double circuit line; t is tcAnd the protection action time of the outlet fault is compensated for on the double circuit line in series.
Preferably, when the inverse time-lag zero-sequence current protection malfunction is a series compensation opposite-side inverse time-lag zero-sequence current upper-lower level protection malfunction, the formula for setting the upper level protection starting current in step S3 is as follows:
IP.next＝KP·Ical.P
wherein, Ical.PThe lower-level protection zero-sequence measurement current for the fault on the double circuit line is equal to the starting current IPZero sequence measurement current value, K, of upper protection on double circuit linePFor a reliability factor, KP∈[1.1～1.3]；IP.nextAnd representing the upper-level protection starting current setting value.
The starting current of the upper-level protection is reasonably set, the starting current setting value of the upper-level protection on the side of the series compensation is increased, the upper-level protection action time can be avoided from the lower-level protection action time on the double-circuit line, and the misoperation of the upper-level protection is avoided.
Preferably, when the upper-stage protection starting current setting value IP.nextGreater than a starting current threshold value Ith.PAnd in time, the anti-time-limit zero-sequence current protection cannot avoid the load current of the line in normal operation, and the anti-time-limit zero-sequence current protection exits, so that the selectivity of the protection action is ensured.
Preferably, when the upper-level protection and the lower-level protection of the side inverse time-limited zero-sequence current at the series compensation location are set, the process of setting the lower-level protection time constant on the double-circuit line in step S4 includes:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxAccording to the current characteristic of the inverse time-limited zero-sequence current protection time, the lower protection time constant T on the double-circuit line is subjected toP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 includes:
lower-level protection setting current I combined with fault at setting check points.dlTime t of operations.dlUpper stage protection setting current Ie.nextAnd upper-level protection setting action time
te.next＝ts.dl+Δt,
Wherein, delta t is a set time step difference and an upper-level protection set current Ie.nextUpper protection operation time te.nextZero sequence current protection according to inverse time limitThe current characteristic of the protection time is obtained to obtain the setting value T of the upper protection time constantP.next：
TP.next＝te.next[(Ie.next/IP)0.02-1]/0.14
Wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
Preferably, when the upper-lower level protection of the inverse time-limited zero-sequence current on the opposite side of the series compensation is set, the process of setting the lower level protection time constant on the double-circuit line in step S4 includes:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxFor lower protection time constant T on double-circuit lineP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 further includes:
lower-level protection setting current I in combination with protection outlet faults.dlTime t of operations.dlProtective setting current I with upper stagee.nextAnd upper protection action time:
te.next＝ts.dl+Δt，
wherein, the delta t is a set time step difference and passes through a set current Ie.nextTime t of operatione.nextAnd upper-level protection starting current setting value IP.nextObtaining the upper-level protection time constant setting value T according to the current characteristic of the inverse time limit zero-sequence current protection timeP.nextThe formula is as follows:
TP.next＝te.next[(Ie.next/IP.next)0.02-1]/0.14
wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
the invention provides a double-circuit line inverse time-limit zero-sequence current protection setting method with series compensation, which analyzes two working conditions of the inverse time-limit zero-sequence current protection misoperation at the side of the double-circuit line where the series compensation is located and the opposite side of the series compensation, determines a setting check point of upper and lower protection coordination of the inverse time-limit zero-sequence current at the side of the series compensation, sets a starting current at the opposite side of the series compensation, improves the conventional step-by-step setting scheme of the inverse time-limit zero-sequence protection, further sets time constants of upper and lower protection at the two sides of the double-circuit line according to the conventional step-by-step setting method of the inverse time-limit zero-sequence current protection after improvement, solves the problem of the protection misoperation of the double-circuit line with the series compensation caused by the series compensation, ensures the selectivity of the protection, and has practical engineering significance for the setting of the inverse time-limit zero-sequence current.
Drawings
FIG. 1 is a schematic flow chart of an inverse time-lag zero-sequence current protection setting method for a double-circuit line with series compensation according to the present invention;
FIG. 2 is a schematic diagram illustrating a conventional inverse time-lag zero-sequence current protection step-by-step setting proposed in an embodiment of the present invention;
fig. 3 is a schematic diagram of a double-circuit line structure with series compensation according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a trend of upper and lower protection current distribution characteristics of a side where a series compensation of a double-circuit line including the series compensation is provided in an embodiment of the present invention;
fig. 5 is a schematic diagram illustrating a trend of upper and lower protection current distribution characteristics at opposite sides of a series compensation of a double-circuit line including a series compensation according to an embodiment of the present invention;
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for better illustration of the present embodiment, certain parts of the drawings may be omitted, enlarged or reduced, and do not represent actual dimensions;
it will be understood by those skilled in the art that certain well-known descriptions of the figures may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, a schematic flow chart of an inverse time-lag zero-sequence current protection setting method for a double-circuit line with series compensation, the method includes the following steps:
s1, determining an inverse time limit zero sequence current protection double-circuit line containing series compensation to be set;
s2, judging whether the reverse time-limit zero-sequence current protection is in misoperation, if so, executing a step S3; otherwise, executing the step S4 according to the conventional inverse time limit zero sequence current protection step-by-step setting method;
in specific implementation, the inverse time-limit zero-sequence current protection action time is changed along with the change of the magnitude of the fault zero-sequence measurement current, the fault adaptability is strong, and the conventional inverse time-limit zero-sequence current protection action characteristic t (I)M0) The formula is as follows:
wherein, IM0For protection of the measurement current, the value is 3 times the zero sequence current, T, flowing through the protectionPIs a time constant, IPTo protect the starting current; in the conventional inverse time limit zero sequence current protection step-by-step setting method, the time constant T is setPAnd protection of the starting current IPRespectively setting: starting current IPSetting an unbalanced current which needs to be avoided when the line normally runs; time constant TPSetting a setting time step difference delta t which meets the condition that the upper and lower stage protection action time difference is ensured to be larger than zero at the most difficult matched setting check point, and then according to the inverse time limitThe time current action characteristic of protection is distributed uniformly along with the line impedance, and the action time of the upper and lower protection is naturally matched, so that the selectivity of the upper and lower protection can be ensured.
The lower protection outlet fault point is used as the setting check point of the upper and lower protection, and when the setting check point of the upper and lower protection is in fault, the upper protection acts for a time teIs shorter than the lower level protection operation time tsOne more fixed time step Δ t, the formula is:
te＝ts+Δt
wherein the upper protection time constant is determined by the protection action time teDetermining, as a schematic diagram of the conventional inverse time-limited zero-sequence current protection step-by-step setting shown in fig. 2, kk denotes a place where an earth fault occurs, A, B, C denotes node buses, the inverse time-limited zero-sequence current protection of each line is 1, 2, 3 in fig. 2, and the relationship of each protection action time t along with the change of the fault position l is shown in fig. 2. When the fault occurrence point kk is at the exit of the lower-stage protection 3, namely the setting check point, the action time of the protection 3 is tsThe time difference between two protection actions is minimum when the upper and lower protection has a fault at the setting check point, and is the time difference delta t, the time difference between the two protection actions is naturally prolonged along with the distance of the fault point kk from one end of the protection, and the time difference between the two protection actions is larger and larger as can be seen from figure 2, but the condition that the time difference between the two protection actions is smaller than the setting time difference delta t can not occur, so when the setting is performed according to the conventional inverse time-limit zero-sequence current protection step-by-step setting method, the setting of the upper protection time constant adopts the upper protection action time teAnd (6) setting.
In this embodiment, a worker determines whether the inverse time-lag zero-sequence current protection is in false operation by analyzing the distribution condition of the fault zero-sequence current when the ground fault occurs on the double-circuit line containing the series compensation; referring to fig. 3, the double-circuit line is MN, the buses on both sides are bus a and bus B, respectively, and the fault occurs on the double-circuit line, ZL0For zero-sequence impedance of the line, ZCTo compensate for impedance, Ik0For zero sequence current at fault point, IAM、IM2、IN2、IBNAnd respectively measuring the current for each line protection zero sequence. Referring to FIG. 3, the series compensation impedance ZCThe ratio of the impedance value of the installation position to the impedance value of one end of the double-circuit line to the impedance value of the whole length of the line is kCWherein k isCLess than 50 percent; two protections of a line adjacent to one end with the distance a from the installation position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation, two protections of a line adjacent to one end with the distance b from the installation position of the series compensation are the upper and lower level protections of the side inverse time-limited zero-sequence current of the series compensation, wherein b>a; namely, two adjacent line protections at the end close to the mounting position of the series compensation are the upper and lower level protections of the reverse time-limited zero-sequence current at the side where the series compensation is located, and two adjacent line protections at the end far away from the mounting position of the series compensation are the upper and lower level protections of the reverse time-limited zero-sequence current at the side where the series compensation is located; the anti-time-limit zero-sequence current protection misoperation comprises upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is positioned and upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is positioned; that is, two adjacent line protections near the series compensation installation position are the upper and lower level protections for the side inverse time-limited zero-sequence current of the series compensation, and two adjacent line protections far away from the series compensation installation position are the upper and lower level protections for the side inverse time-limited zero-sequence current of the series compensation, as shown in fig. 3, when the ground fault occurs on the double-circuit line, the fault occurrence on the left side of the series compensation can be obtained (0)<k<kC) And on the right side of the Heshang (k)C<k<1) The magnitude of zero-sequence measurement current of upper and lower level protection on two sides of a time-double-circuit line is measured, wherein k is the ratio of the length of a fault position from a bus M line to the total length MN of the line, and the zero-sequence measurement current of upper level protection in the upper and lower level protection of the zero-sequence current with inverse time limit on the side where the series compensation is located is IAMThe lower-level protection zero-sequence measurement current is IM2The zero-sequence measurement current of the upper protection level in the upper and lower level protection of the side inverse time-limited zero-sequence current of the series compensation is IBNThe lower-level protection zero-sequence measurement current is IN2。
S3, judging whether the inverse time-limit zero-sequence current protection misoperation is the upper and lower level misoperation of the inverse time-limit zero-sequence current protection on the side of the series compensation, and if so, determining a setting check point matched with the upper and lower level protection of the inverse time-limit zero-sequence current on the side of the series compensation; otherwise, the reverse time-limited zero-sequence current protection malfunction is the upper and lower protection malfunction of the reverse time-limited zero-sequence current at the opposite side of the series compensation, and the upper protection starting current is set;
specifically, for the upper and lower level protection at the side where the series compensation of the double-circuit line is located and the opposite side of the series compensation, whether a malfunction occurs is judged, and different setting measures are taken corresponding to the malfunction of the upper and lower level protection at different sides:
when the fault zero-sequence current of the lower-level protection outlet installed on the double-circuit line is smaller than the fault zero-sequence current of the series compensation outlet, the time difference delta t of the upper-level protection action and the lower-level protection action of the side inverse time-limit zero-sequence current of the series compensation outletLWhen the time level difference is smaller than the set time level difference delta t, the upper and lower level protection misoperation condition of the side inverse time limit zero sequence current of the series compensation place occurs, as shown in fig. 4, the abscissa k is the ratio of the length of the fault position to the bus M line length to the total line length; ordinate IkRepresenting zero sequence measurement current, IPIn order to protect the starting current, a circle region is circled by a kc point on the abscissa axis of the graph 4, and when the line region of the section has a fault, the time difference delta t of the upper-level protection action and the lower-level protection action of the side inverse time-limit zero-sequence current of the series compensation position can occurLThe phenomenon that the time level difference is smaller than the set time level difference delta t, the selectivity requirement of the inverse time-limited zero-sequence current protection cannot be met, the false action is protected, and the false action of the inverse time-limited zero-sequence current protection is generated on the side of the series compensation;
when the reverse time-limit zero-sequence current protection malfunction is the upper and lower level protection malfunction of the reverse time-limit zero-sequence current on the side of the series compensation, the zero-sequence measuring current I for protecting the outlet fault on the double-circuit line is selectedrAnd zero sequence measurement current I of series compensation outlet fault on double-circuit linecThe larger one of the two is used as a setting check point of the upper-level protection and the lower-level protection of the side inverse time limit zero sequence current of the series compensation place, namely, the setting check point passes through:
Is＝max(Ir,Ic)
wherein, IsRepresenting the setting current of the head end of the lower protection on the double-circuit line at the setting check point; i isrRepresenting the fault zero-sequence measurement current of a protection outlet on the double-circuit line; i iscZero sequence measurement current representing a series compensation outlet fault on a double-circuit line;
when the reverse time-limited zero-sequence current protection malfunction is the series compensation opposite-side reverse time-limited zero-sequence current upper and lower level protection malfunction, the protection setting action time satisfies the following conditions:
ts+Δt＝min(tr+Δt,tc+Δt)
wherein, tsProtecting and setting action time for the head end of the lower-level protection on the double-circuit line at the protection and setting check point; delta t is the step difference of the fixed time; t is trRepresenting the protection action time of the fault of the protection outlet on the double circuit line; t is tcAnd the protection action time of the outlet fault is compensated for on the double circuit line in series.
When the lower-level protection zero-sequence measurement current I installed on the double-circuit lineN2Less than zero sequence protection starting current IpAnd the upper level protects the zero sequence measuring current IBNGreater than zero sequence protection starting current IpTime, series compensation opposite side inverse time limit zero sequence current upper and lower level protection action time difference delta tRAnd when the time level difference is less than the set time level difference delta t, the series compensation is carried out on the upper and lower level protection misoperation of the side inverse time-limited zero-sequence current. In the reverse time-limited zero-sequence current protection of the double-circuit line, the situation that the upper-level protection measuring current is larger than the lower-level protection measuring current on the double-circuit line can occur due to the influence of the other circuit branch line, under the influence of series compensation, as shown in fig. 5, in a circle region encircled by a kc point on the abscissa axis of fig. 5, when the line region has a fault, the series compensation rejects the lower-level protection of the reverse time-limited zero-sequence current, and the action time is just the rejection of the lower-level protection, so that the action time is larger than the action time of the upper-level protection, the maloperation of the upper-level protection is caused, and the action time difference delta t between the upper-level protection and the lower-level protection ofRAnd when the time difference is less than the set time difference delta t, the requirement of protection selectivity cannot be met.
When the inverse time-limited zero-sequence current protection malfunction occurs on the opposite side of the series compensation, the starting current setting value of the upper protection on the opposite side of the series compensation is increased, so that the upper protection action time can avoid the lower protection action time on the double circuit, and the formula for setting the upper protection starting current is as follows:
IP.next＝KP·Ical.P
wherein, Ical.PThe lower-level protection zero-sequence measurement current for the fault on the double circuit line is equal to the starting current IPZero sequence measurement current value, K, of upper protection on double circuit linePFor a reliability factor, KP∈[1.1～1.3]；IP.nextRepresenting a superior protection starting current setting value; when the upper protection starting current setting value IP.nextGreater than a starting current threshold value Ith.PWhen it is used, usually Ith.PAnd taking 500A, protecting the anti-time-limit zero-sequence current so as not to avoid the load current of the line in normal operation, and quitting the protection of the anti-time-limit zero-sequence current so as to ensure the selectivity of the protection action.
After the setting of the setting check points and the starting current on the two sides of the double-circuit line containing series compensation is finished, the time constants of the upper-stage protection and the lower-stage protection on the two sides of the double-circuit line can be further set according to a conventional inverse time limit zero-sequence current protection step-by-step setting method, namely the step S4 and the step S5:
s4, setting a lower-level protection time constant on the double-circuit line;
s5, setting a superior protection time constant on the double-circuit line;
in this embodiment, when the upper-lower protection setting of the side inverse time-lag zero-sequence current at the series compensation location is performed, the process of setting the lower protection time constant on the double-circuit line in step S4 includes:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxAccording to the current characteristic of the inverse time-limited zero-sequence current protection time, the lower protection time constant T on the double-circuit line is subjected toP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 includes:
lower-level protection setting current I combined with fault at setting check points.dlTime t of operations.dlUpper stage protection setting current Ie.nextAnd upper-level protection setting actionTime of day
te.next＝ts.dl+Δt,
Wherein, delta t is a set time step difference and an upper-level protection set current Ie.nextUpper protection operation time te.nextAccording to the current characteristic of the inverse time limit zero sequence current protection time, the upper protection time constant setting value T is obtainedP.next：
TP.next＝te.next[(Ie.next/IP)0.02-1]/0.14
Wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
In this embodiment, when the series compensation sets the upper and lower level protection of the side inverse time zero sequence current, the process of setting the lower level protection time constant on the double-circuit line described in step S4 includes:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxFor lower protection time constant T on double-circuit lineP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 further includes:
lower-level protection setting current I in combination with protection outlet faults.dlTime t of operations.dlProtective setting current I with upper stagee.nextAnd upper protection action time:
te.next＝ts.dl+Δt，
wherein, Delta t is the setting timeStep difference, by setting current Ie.nextTime t of operatione.nextAnd upper-level protection starting current setting value IP.nextObtaining the upper-level protection time constant setting value T according to the current characteristic of the inverse time limit zero-sequence current protection timeP.nextThe formula is as follows:
TP.next＝te.next[(Ie.next/IP.next)0.02-1]/0.14
wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
And S6, outputting a setting result of the anti-time-limit zero-sequence current protection of the double-circuit line with the series compensation.
The relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A method for protecting and setting the inverse time limit zero sequence current of a double-circuit line containing series compensation is characterized by at least comprising the following steps:
s1, determining an inverse time limit zero sequence current protection double-circuit line containing series compensation to be set;
s2, judging whether the reverse time-limit zero-sequence current protection is in misoperation, if so, executing a step S3; otherwise, executing the step S4 according to the conventional inverse time limit zero sequence current protection step-by-step setting method;
s3, judging whether the reverse time limit zero sequence current protection misoperation is the upper and lower level protection misoperation of the reverse time limit zero sequence current at the side of the series compensation, if so, determining a setting check point matched with the upper and lower level protection of the reverse time limit zero sequence current at the side of the series compensation; otherwise, the reverse time-limited zero-sequence current protection malfunction is the upper and lower protection malfunction of the reverse time-limited zero-sequence current at the opposite side of the series compensation, and the upper protection starting current is set;
s4, setting a lower-level protection time constant on the double-circuit line;
s5, setting a superior protection time constant on the double-circuit line;
and S6, outputting a setting result of the anti-time-limit zero-sequence current protection of the double-circuit line with the series compensation.
2. The method for setting inverse time-lag zero-sequence current protection of a double-circuit line with series compensation according to claim 1, wherein whether inverse time-lag zero-sequence current protection is malfunction is judged by analyzing the distribution condition of fault zero-sequence current when a ground fault occurs on the double-circuit line with series compensation;
the ratio of the impedance value of the series compensation installation position to the impedance value of one end of the double-circuit line to the impedance value of the whole length of the line is kCWherein k isCLess than 50 percent, two protections of a line adjacent to one end with the distance a from the installation position of the series compensation are the upper and lower level protections of the reverse time-limited zero-sequence current at the side of the series compensation, two protections of a line adjacent to one end with the distance b from the installation position of the series compensation are the upper and lower level protections of the reverse time-limited zero-sequence current at the opposite side of the series compensation, wherein b>a; the anti-time-limit zero-sequence current protection misoperation comprises upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is located and upper and lower level protection misoperation of the anti-time-limit zero-sequence current on the side where the series compensation is located.
3. The method for setting inverse time-lag zero-sequence current protection of double-circuit line with series compensation of claim 2, wherein when the fault zero-sequence current of the lower protection outlet installed on the double-circuit line is smaller than that of the series compensation outlet, the time difference Δ t of the upper and lower protection actions of the inverse time-lag zero-sequence current of the side where the series compensation is locatedLAnd when the time level difference is less than the set time level difference delta t, the upper and lower level protection misoperation of the reverse time limit zero sequence current on the side where the series compensation is positioned occurs.
4. The method of claim 3The method for protecting and setting the inverse time-limit zero-sequence current of the double-circuit line with series compensation is characterized in that when the lower-level protection zero-sequence measuring current installed on the double-circuit line is smaller than the zero-sequence protection starting current and the upper-level protection zero-sequence measuring current is larger than the zero-sequence protection starting current, the series compensation acts on the time difference delta t of the upper-level protection and the lower-level protection action of the opposite-side inverse time-limit zero-sequence currentRAnd when the time level difference is less than the set time level difference delta t, the series compensation is carried out on the upper and lower level protection misoperation of the side inverse time-limited zero-sequence current.
5. The method for setting inverse time-lag zero-sequence current protection of double-circuit line with series compensation of claim 4, wherein when the inverse time-lag zero-sequence current protection malfunction is the upper and lower level protection malfunction of the inverse time-lag zero-sequence current at the side of the series compensation, the zero-sequence measurement current I of the protection outlet fault on the double-circuit line is selectedrAnd zero sequence measurement current I of series compensation outlet fault on double-circuit linecThe larger one of the two is used as a setting check point of the upper-level protection and the lower-level protection of the side inverse time limit zero sequence current of the series compensation place, namely, the setting check point passes through:
Is＝max(Ir,Ic)
wherein, IsRepresenting the setting current of the head end of the lower protection on the double-circuit line at the setting check point; i isrRepresenting the fault zero-sequence measurement current of a protection outlet on the double-circuit line; i iscAnd the zero sequence measurement current of the series compensation outlet fault on the double-circuit line is shown.
6. The method for setting the inverse time-lag zero-sequence current protection of the double-circuit line with the series compensation of claim 5, wherein when the inverse time-lag zero-sequence current protection malfunction is the upper and lower protection malfunction of the inverse time-lag zero-sequence current at the opposite side of the series compensation, the protection setting action time is satisfied:
ts+Δt＝min(tr+Δt,tc+Δt)
wherein, tsProtecting and setting action time for the head end of the lower-level protection on the double-circuit line at the protection and setting check point; delta t is the step difference of the fixed time; t is trRepresenting the protection action time of the fault of the protection outlet on the double circuit line; t is tcFor series compensation on double circuitThe protection action time of the port fault.
7. The method for setting the inverse time-lag zero-sequence current protection of the double-circuit line with the series compensation as claimed in claim 6, wherein when the inverse time-lag zero-sequence current protection malfunction is the upper and lower protection malfunction of the inverse time-lag zero-sequence current at the opposite side of the series compensation, the formula for setting the upper protection starting current in step S3 is:
IP.next＝KP·Ical.P
wherein, Ical.PThe lower-level protection zero-sequence measurement current for the fault on the double circuit line is equal to the starting current IPZero sequence measurement current value, K, of upper protection on double circuit linePFor a reliability factor, KP∈[1.1～1.3]；IP.nextAnd representing the upper-level protection starting current setting value.
8. The method for setting inverse time-lag zero-sequence current protection of double-circuit line with series compensation of claim 7, wherein the current setting value I is started when upper protection is performedP.nextGreater than a starting current threshold value Ith.PAnd then, the anti-time-limit zero-sequence current protection cannot avoid the load current of the line in normal operation, and the anti-time-limit zero-sequence current protection exits.
9. The method for setting the inverse time-lag zero-sequence current protection of the double-circuit line with the series compensation of claim 8, wherein the step S4 of setting the lower-level protection time constant of the double-circuit line comprises, at the time of the upper-level protection setting and the lower-level protection setting of the inverse time-lag zero-sequence current at the side of the series compensation:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxAccording to the current characteristic of the inverse time-limited zero-sequence current protection time, the lower protection time constant T on the double-circuit line is subjected toP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 includes:
lower-level protection setting current I combined with fault at setting check points.dlTime t of operations.dlUpper stage protection setting current Ie.nextAnd upper-level protection setting action time
te.next＝ts.dl+Δt,
Wherein, delta t is a set time step difference and an upper-level protection set current Ie.nextUpper protection operation time te.nextAccording to the current characteristic of the inverse time limit zero sequence current protection time, the upper protection time constant setting value T is obtainedP.next：
TP.next＝te.next[(Ie.next/IP)0.02-1]/0.14
Wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
10. The method for setting the inverse time-limited zero-sequence current protection of the double-circuit line with the series compensation of claim 9, wherein the step S4 of setting the lower protection time constant of the double-circuit line comprises, at the time of the upper and lower protection setting of the inverse time-limited zero-sequence current at the opposite side of the series compensation:
maximum zero-sequence current I of double-circuit line tail end faultdl.maxAnd the maximum protection action time t of the terminaldl.maxFor lower protection time constant T on double-circuit lineP.dlSetting is carried out, and the formula is as follows:
TP.dl＝tdl.max[(Idl.max/IP)0.02-1]/0.14
wherein, TP.dlRepresenting a lower protection time constant on the double-circuit line; t is tdl.maxRepresenting the terminal maximum protection action time; i isdl.maxRepresenting the maximum zero sequence current of the double-circuit line tail end fault; i isPRepresents the starting current;
the process of setting the upper protection time constant on the double-circuit line in step S5 further includes:
lower-level protection setting current I in combination with protection outlet faults.dlTime t of operations.dlProtective setting current I with upper stagee.nextAnd upper protection action time:
te.next＝ts.dl+Δt，
wherein, the delta t is a set time step difference and passes through a set current Ie.nextTime t of operatione.nextAnd upper-level protection starting current setting value IP.nextObtaining the upper-level protection time constant setting value T according to the current characteristic of the inverse time limit zero-sequence current protection timeP.nextThe formula is as follows:
TP.next＝te.next[(Ie.next/IP.next)0.02-1]/0.14
wherein, TP.nextRepresenting a superior protection time constant setting value; t is te.nextRepresenting the upper protection action time; i ise.nextRepresenting the upper-level protection setting current; i isPIndicating the starting current.
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