CN118100094A - Transformer quick-break protection method and device based on electric quantity abrupt change starting time difference - Google Patents
Transformer quick-break protection method and device based on electric quantity abrupt change starting time difference 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
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
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Abstract
The invention discloses a transformer quick-break protection method and device based on an electric quantity abrupt change starting time difference, wherein the method comprises the following steps: judging whether protection is started or not according to rules for the current sampling point; if the protection starting point is started, the current sampling point is taken as the protection starting point, the protection judging result category is determined through a rule, and the next step is started only when the judging result category is a fault category, otherwise, the protection is directly locked; determining a gear which is protected by a rule, and determining the starting moment of current integration; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected; starting from the starting time of voltage integration to the 12 th sampling point after the protection starting point, obtaining the absolute value integration of the three-phase current variation; respectively determining a basic action threshold curve and a total peak braking increment curve; and allowing the sampling point to act as an outlet only when any sampling point after the current integration starting moment completely meets the preset requirement.
Description
Technical Field
The invention relates to the technical field of electricity, in particular to a method and a device for protecting a transformer from quick break based on an electric quantity abrupt change starting time difference.
Background
The safe and reliable operation of the power transformer as a main device of a power system is important. After the internal faults of the transformer occur, the fault detection and fault removal are realized by the relay protection device of the transformer, so that the equipment safety of the transformer and the stable operation of a power system are ensured.
The current differential protection is used as the main protection of the transformer, and is widely applied due to the simple principle and good selectivity. Conventional differential protection is configured with corresponding latch elements in order to avoid malfunction due to non-internal fault abnormal states such as CT saturation and magnetizing inrush current. Thus, the actuation time of conventional differential protection is closely related to the performance of these latching elements. Meanwhile, in order to avoid that the protection action speed is affected by the blocking element and the fault cannot be quickly removed when the internal serious fault occurs in the transformer, a differential quick-break protection element without any blocking is generally arranged in the transformer protection device. According to the requirements of related technical standards, the action time of differential protection is not more than 30ms, and the differential breaking action time is not more than 20ms. However, in recent years, when serious faults occur, the rising speed of fault current is extremely high, energy is rapidly accumulated in a short time, heat cannot be released in time, and finally the explosion and combustion of the transformer are caused, so that the differential breaking protection of the transformer is required to identify faults and act within 5ms in the serious fault scene; however, the conventional transformer has higher differential breaking protection fixed value and slower action speed, and is difficult to meet the quick action requirement in principle. Therefore, a differential protection method capable of rapidly identifying the inrush current characteristics in the inrush current scene, guaranteeing the protection safety and reliability, rapidly identifying the fault characteristics in the fault scene and realizing the ultra-high-speed and ultra-sensitive actions is needed to be provided.
Disclosure of Invention
The invention provides a transformer quick-break protection method and device based on an electric quantity abrupt change starting time difference, which aims to solve the problems of insufficient sensitivity and slower action speed of the quick-differential quick-break protection based on sampling values under the serious faults of the existing transformer.
According to one aspect of the invention, there is provided a method for protecting a transformer from rapid disconnection based on an electrical quantity abrupt change start time difference, comprising:
Judging whether protection is started or not according to a preset protection starting time judging rule for the current sampling point t;
If the protection is started, taking the current sampling point as a protection starting point t start, then determining a protection judging result category through a preset voltage integration starting moment judging rule, and entering a current integration starting moment judging step only when the judging result category is a fault category, otherwise directly locking the protection;
Determining a gear which is protected by a preset current integration starting moment judgment rule, and determining a current integration starting moment t Cur; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected;
Starting from a voltage integration starting time t Vol to a 12 th sampling point after a protection starting point, obtaining the absolute value integration of the three-phase current variation; respectively determining a basic action threshold curve K threshold (t) and a total peak braking increment curve S threshold (t) in a preset mode;
Any sampling point is fully satisfied only after the current integration starting time When the sampling point is allowed to act as an outlet: in the/>Integrating the absolute value of the three-phase current variation quantity,/>Representing each phase, K threshold (t) is the base action threshold curve, S threshold (t) is the total peak brake delta curve,/>The three-phase ratio is regulated.
Optionally, the protection start time judgment rule is determined by:
Defining the protection starting time as t start, and setting t start to 0; defining three-phase currents at the high-voltage side of the transformer as i A、iB、iC respectively, and obtaining the variation of the three-phase currents according to the formula (1) Wherein t is the current time:
then the square sum of the inter-phase current difference is defined according to the formula (2)
Defining rated starting current I σ according to formula (3);
Wherein, I e is the effective value of the rated current value marked on the transformer nameplate, and I n is the CT rated current;
then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (4)
For the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to the formula (5):
In the middle of For the starting coefficient, when the difference flow reaches 0.5p.u., the starting setting can be sensitively started; when the three formulas in the formula (5) are all satisfied, defining the time t-2 as the suspected starting time/>
And defining a high-voltage side zero sequence current i 0 according to a formula (6):
i0(t)＝(iA(t)+iB(t)+iC(t))/3 (6)
and defining a high-voltage side zero sequence current maximum value i 0MAX according to the formula (7):
i0MAX(t)＝max{i0(t)|t∈[t-24,t-12]} (7)
for the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to a formula (8):
In the middle of The zero sequence starting coefficient is set by sensitively starting when the difference flow reaches 0.5 p.u.; when the three formulas in the formula (8) are all satisfied, defining the time t-2 as the suspected starting time/>For any sampling point, when the sampling point belongs to suspected starting time/>Or suspected start-up time/>In any case, judging the sampling point as the protection starting time, and covering the time stamp of the sampling point with the value of t start; and once t start is not equal to 0, stopping the protection starting time criterion judgment of all subsequent sampling points.
Optionally, the voltage integration start time judgment rule is determined by:
defining the three-phase voltage of the high-voltage side of the transformer as u A、uB、uC; defining the effective value of the high-voltage side phase voltage as U e; for any sampling point needed to judge the starting moment of voltage integration, the change amount of the three-phase voltage is obtained according to the formula (9)
Then the square sum of the inter-phase current difference is defined according to (10)
Then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (11)
Under the condition that the protection starting point t start is determined, dividing the judging result into three types of inrush current, fault and CT disconnection according to the protection starting point and the conditions of all sampling points nearby the protection starting point; defining voltage integration starting time t Vol according to different categories of judgment results;
When the class of the judgment result is the inrush class, for the sampling point t start -1 (i.e., the sampling point immediately before the protection starting point), it is judged whether it satisfies the formula (12):
In the middle of Setting the initial low voltage value according to the maximum unbalance of the system, and setting according to the condition that the sampling point (namely the sampling point t start -1) before the protection starting moment is not satisfied with the formula (12); if the sampling point meets the above formula, judging that the protection enters the inrush current locking logic, and setting t Vol to 0; otherwise, judging the fault class;
When the type of the judging result is a fault type, the fixed value is set according to the condition that the protection starting time meets the formula (12) and the sampling point before the protection starting time does not meet the formula (12) under the condition of the fault in the minimum area; for a sampling point t start, judging whether the sampling point t start meets the formula (12); if yes, judging that protection enters fault action logic, and taking the time stamp of the sampling point as a voltage integration starting time t Vol; otherwise, judging the CT broken line;
when the type of the judgment result is the CT disconnection type, judging whether the sampling point t start +1 (namely, the sampling point after the protection starting point) meets the formula (13):
In the method, in the process of the invention, Setting the voltage integration initial high fixed value according to 2 times of the right bracket in the formula (12); if yes, the same protection enters fault action logic, and the time stamp of the sampling point is taken as a voltage starting time t Vol; otherwise, the protection is determined to enter CT broken line locking logic, and t Vol is set to 0.
Alternatively, the current integration start time judgment rule is determined by:
When the scene is determined to be gear 0, on the condition that the protection starting point t start has been determined and t Vol is not equal to 0, for the sampling point t start, whether the formula (13) is established is determined:
In the middle of Starting a constant value for current integration of the gear 0; if so, the protection starting point t start is considered to meet the current integration starting condition, a protection entering gear 0 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, trying to enter the gear 1 to continue judgment;
When the scene is determined to be gear 1, on the condition that the protection starting point t start is determined and t Vol is not equal to 0, for the sampling point t start +1, whether the formula (14) is established is determined:
In the method, in the process of the invention, Starting a constant value for current integration of the gear 1;
if so, the sampling point t start +1 is considered to meet the current integration starting condition, a protection entering gear 1 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, judging that the protection enters other gears, and directly locking the protection by a current integration starting moment judging method.
Optionally, from the voltage integration starting time t Vol to the 12 th sampling point after the protection starting point, the absolute value integration of the three-phase current variation is obtained, including:
defining the low-voltage side three-phase current of the transformer as i a,ib,ic, and obtaining the variation of the low-voltage side three-phase current according to the formula (15) Wherein t is the current time:
then, the absolute value of the three-phase small difference flow variation is obtained according to the formula (16), namely:
Under the condition that the current integration starting moment is not found after the protection is started, the absolute value of the three-phase small difference current variation at the current moment is set to be 0;
After the protection is started and under the condition that the voltage integration starting moment t Vol is found, starting from the voltage integration starting moment t Vol to the 12 th sampling point after the protection starting point, summing the absolute value of the three-phase small-difference current variation of each sampling point according to the formula (17) to obtain three-phase current variation absolute value integration:
Optionally, the determining the base action threshold curve K threshold (t) and the total peak brake increment curve S threshold (t) in a preset manner includes:
After the protection starting point t start has been determined, but under the condition that the current starting time t Cur has not been found, making the temporary basic action threshold from the protection starting time t start to the current time t be K threshold (t) =9p.u.;
under the condition that the protection starting point t start has been determined and the current start time t Cur has been found, first a parameter describing the shape of the base action threshold curve is defined according to the gear into which the protection is entered:
If the gear is protected to be in the gear 0, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., and the fixed value of the t start +4 point to the t start +12 point is 90p.u.;
If the gear 1 is protected, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., the fixed value of the t start +4 point is 5p.u., and the fixed value of the t start +6 point to the t start +12 point is 90p.u.
Optionally, the method further comprises:
defining three-phase peak value braking action threshold increment function as Defining a total peak brake actuation threshold delta function S threshold (t);
Under the condition that the guard start point t start has been determined and the current integration start time t Cur has been found, from time t Cur, the value of the total peak brake actuation threshold delta function for each sample point is determined as per equation (18):
wherein S coe is a peak brake coefficient, which is used to adjust the sensitivity of the protection method.
According to still another aspect of the present invention, there is provided a transformer quick-break protection device based on an electrical quantity abrupt change start time difference, comprising:
the first judging module is used for judging whether protection is started or not according to a preset protection starting moment judging rule for the current sampling point t;
The second judging module is used for taking the current sampling point as a protection starting point t start if the protection is started, then determining a protection judging result category through a preset voltage integration starting moment judging rule, entering a current integration starting moment judging step only when the judging result category is a fault category, and directly locking the protection if the judging result category is not a fault category;
the third judging module is used for determining the gear which is protected and enters through a preset current integration starting moment judging rule, and determining a current integration starting moment t Cur; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected;
The determining module is used for obtaining the absolute value integral of the three-phase current variation from the voltage integral starting time t Vol to the 12 th sampling point after the protection starting point; respectively determining a basic action threshold curve K threshold (t) and a total peak braking increment curve S threshold (t) in a preset mode;
an action module for completely satisfying any sampling point only after the current integration starting time When the sampling point is allowed to act as an outlet: in the/>Integrating the absolute value of the three-phase current variation quantity,/>Representing each phase, K threshold (t) is the base action threshold curve, S threshold (t) is the total peak brake delta curve,/>The three-phase ratio is regulated.
According to a further aspect of the present invention there is provided a computer readable storage medium storing a computer program for performing the method according to any one of the above aspects of the present invention.
According to still another aspect of the present invention, there is provided an electronic device including: a processor; a memory for storing the processor-executable instructions; the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any of the above aspects of the present invention.
The invention judges whether protection is started or not according to rules for the current sampling point; if the protection starting point is started, the current sampling point is taken as the protection starting point, the protection judging result category is determined through a rule, and the next step is started only when the judging result category is a fault category, otherwise, the protection is directly locked; determining a gear which is protected by a rule, and determining the starting moment of current integration; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected; starting from the starting time of voltage integration to the 12 th sampling point after the protection starting point, obtaining the absolute value integration of the three-phase current variation; respectively determining a basic action threshold curve and a total peak braking increment curve; and allowing the sampling point to act as an outlet only when any sampling point after the current integration starting moment completely meets the preset requirement. The invention can realize the action within 2ms under the serious faults of the transformer, and reliably does not act in the occasions such as inrush current, CT disconnection, out-of-zone faults and the like, and has excellent performance, thereby obviously improving the reliability of the stable operation of the transformer.
Drawings
Exemplary embodiments of the present invention may be more completely understood in consideration of the following drawings:
FIG. 1 is a schematic diagram of a transformer fault simulation model in an embodiment of the invention;
FIG. 2 is a block diagram of protection initiation logic in an embodiment of the present invention;
FIG. 3 is a logical block diagram of actions in an embodiment of the invention;
FIG. 4 is a schematic diagram of the voltage and current integration start time under a severe fault of phase A in a zone according to an embodiment of the present invention;
FIG. 5 is a graph showing the current variation integral criterion and floating threshold curve under the serious fault of phase A in the area according to the embodiment of the invention;
FIG. 6 is a schematic diagram of a basic action threshold curve and a ratio peak brake delta curve for a severe phase A fault in a zone according to an embodiment of the present invention;
FIG. 7 is a graph showing the rate braking results under severe phase A failure in the zone in an embodiment of the present invention;
FIG. 8 is a schematic diagram of the voltage and current integration onset time under a phase A high resistance fault in a zone according to an embodiment of the present invention;
FIG. 9 is a graph showing the current variation integration criteria and floating threshold curves under a phase A high resistance fault in a zone according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a basic action threshold curve and a ratio peak brake delta curve under a phase A high resistance fault in a zone according to an embodiment of the present invention;
FIG. 11 is a graph showing the ratio brake results under a zone A phase high resistance fault in an embodiment of the present invention;
FIG. 12 is a schematic diagram of the voltage and current integration onset time under an out-of-zone phase A ground fault in an embodiment of the present invention;
FIG. 13 is a schematic diagram of the starting time of voltage and current integration under A-phase space charge surge in an embodiment of the present invention;
fig. 14 is a schematic structural diagram of an electronic device according to an embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements throughout the different drawings, unless indicated otherwise. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be understood that in the description of all embodiments of the invention, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
According to the invention, the traditional alternating current protection device is considered to realize the protection function under the conditions of 50Hz frequency and 1200Hz sampling rate, so that only 6 sampling points can be used for protection operation within 5ms after self-protection starting, and less information can be utilized. On the one hand, only 6 sampling points cannot snoop the full-cycle time domain characteristics of the electric quantity of each phase after the fault, and a frequency domain extraction method based on a short time window has great errors, so that great difficulty exists in the aspect of fault characteristic analysis; on the other hand, even if the time-frequency domain characteristics of the phase electric quantity can be predicted and obtained by certain methods, faults and other anomalies can be successfully distinguished, incorrect actions can be possibly caused by too few sampling points meeting the action conditions, and the safety of the transformer is seriously threatened. Therefore, the design should not keep the conventional idea.
Since the voltage leads the magnetic flux by 90 DEG, and the current is slowly changed due to the hysteresis loop characteristic of the ferromagnetic element; when the ferromagnetic original is saturated after a certain time, the magnetic flux continuously rises to rapidly rise, namely the initial moment of voltage change of the transformer is advanced to the initial moment of current change when in inrush current, and the advance is obvious; the voltage and the current are not changed at the same time in case of failure, and the change is obvious. Therefore, if the time difference between the voltage change time and the current change time can be detected, the excitation surge current can be easily avoided, and a solid foundation is provided for designing differential break protection of the ultra-high-performance transformer purely aiming at the problems of fault scenes, abnormal large numbers, CT broken lines and the like.
The invention firstly provides a starting time judging method. The starting time judging method is divided into three parts: 1) A protection starting moment judging method; 2) A voltage integration starting time judging method; 3) A method for judging the starting time of current integration. The implementation mode is as follows:
1) Protection starting time judging method
First, a protection start time is defined as t start and set to 0. Defining three-phase currents at the high-voltage side of the transformer as i A、iB、iC respectively, and obtaining the variation of the three-phase currents according to the formula (1)Wherein t is the current time:
then the square sum of the inter-phase current difference is defined according to the formula (2)
The rated start-up current I σ is defined according to equation (3).
Wherein I e is the effective value of the rated current value marked on the transformer nameplate, and I n is the CT rated current.
Then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (4)
For the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to the formula (5):
In the middle of For the starting coefficient, when the difference flow reaches 0.5p.u., the starting setting can be sensitively started. When the three formulas in the formula (5) are all satisfied, defining the time t-2 as the suspected starting time/>
And defining a high-voltage side zero sequence current i 0 according to a formula (6):
i0(t)＝(iA(t)+iB(t)+iC(t))/3 (6)
and defining a high-voltage side zero sequence current maximum value i 0MAX according to the formula (7):
i0MAX(t)＝max{i0(t)|t∈[t-24,t-12]} (7)
for the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to a formula (8):
In the middle of The zero sequence starting coefficient can be flexibly started and set when the zero sequence starting coefficient reaches 0.5p.u. according to the difference flow. When the three formulas in the formula (8) are all satisfied, defining the time t-2 as the suspected starting time/>For any sampling point, when the sampling point belongs to suspected starting time/>Or suspected start-up time/>In any case, judging the sampling point as the protection starting time, and covering the time stamp of the sampling point with the value of t start; and once t start is not equal to 0, stopping the protection starting time criterion judgment of all subsequent sampling points.
2) Method for judging starting time of voltage integration
The voltage integration start time judgment method is similar to the protection start time judgment method in (1). Firstly, defining the three-phase voltage of the high-voltage side of the transformer as u A、uB、uC; defining the effective value of the high-voltage side phase voltage as U e; for any sampling point needed to judge the starting moment of voltage integration, the change amount of the three-phase voltage is obtained according to the formula (9)
Then the square sum of the inter-phase current difference is defined according to (10)
Then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (11)
Specifically, under the condition that the protection starting point t start has been determined, the judgment result of the method can be classified into the following three types according to the conditions of the protection starting point and each sampling point in the vicinity thereof. The method defines voltage integration starting time t Vol according to different judgment result categories.
① Inrush current
For sample point t start -1 (i.e., the sample point immediately before the guard start point), it is determined whether it satisfies equation (12):
In the middle of For the voltage initial low fixed value, the fixed value is set according to the maximum unbalance of the system, and according to the condition that the sampling point (namely the sampling point t start -1) before the protection starting moment is not satisfied with the formula (12). If the sampling point meets the above formula, judging that the protection enters the inrush current locking logic, and setting t Vol to 0; otherwise, the fault class discrimination is entered.
② Failure class
The fixed value is set according to the condition that the protection starting time (namely, the sampling point t start) meets the formula (12) and the sampling point (namely, the sampling point t start -1) before the protection starting time does not meet the formula (12) under the condition that the fault in the minimum area (within 20ms after the protection starting) is about 2.8p.u. of the effective value of the fault phase small difference flow fundamental wave. For a sampling point t start (i.e., a protection starting point), judging whether the sampling point t start meets the formula (12); if yes, judging that protection enters fault action logic, and taking the time stamp of the sampling point as a voltage integration starting time t Vol; otherwise, judging the CT disconnection type.
③ CT wire breakage
For sample point t start +1 (i.e., the sample point after the protection start point), it is determined whether it satisfies formula (13):
In the middle of For the initial high constant value of voltage integration, the constant value setting is set according to 2 times of the right bracket in the formula (12), so as to reduce the sensitivity of voltage initiation as much as possible and improve the protection reliability. If yes, the same protection enters fault action logic, and the time stamp of the sampling point is taken as a voltage starting time t Vol; otherwise, the protection is determined to enter CT broken line locking logic, and t Vol is set to 0.
3) Method for judging starting time of current integration
The current integration start time judgment method is similar to the protection start time judgment method in (1). The judgment method retains the operation results of the formulas (1) to (4) in the method 1), and is divided into two judgment scenes. The invention refers to the two scenes as gear 0 and gear 1, and the judging process is introduced as follows:
① Gear 0
On the condition that the protection start point t start has been determined and t Vol +.0, for the sampling point t start, it is judged whether or not the expression (13) holds:
In the middle of The starting value is integrated for the gear 0 current. If so, the protection starting point t start is considered to meet the current integration starting condition, a protection entering gear 0 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, trying to enter the gear 1 continues to judge.
② Gear 1
On the condition that the protection start point t start has been determined and t Vol +.0, for the sampling point t start +1, it is judged whether or not the expression (14) holds:
In the middle of The starting value is integrated for the gear 1 current. If so, the sampling point t start +1 is considered to meet the current integration starting condition, a protection entering gear 1 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, judging that the protection enters other gears, and directly locking the protection by a current integration starting moment judging method.
Furthermore, the invention also provides a current variation absolute value integration method. The absolute value integration method of the current variation is divided into two sub-methods: 1) A method for solving the absolute value of the three-phase small difference flow variation; 2) And (3) integrating the absolute value of the current variation.
1) Method for solving absolute value of three-phase small difference flow variation
Defining the low-voltage side three-phase current of the transformer as i a,ib,ic, and obtaining the variation of the low-voltage side three-phase current according to the formula (15)Wherein t is the current time:
then, the absolute value of the three-phase small difference flow variation is obtained according to the formula (16), namely:
Specifically, the absolute value of the three-phase small difference current variation at the current time is set to 0 under the condition that the current integration starting time is not found after the protection is started.
2) Method for obtaining absolute value integral of current variation
After the protection is started and under the condition that the voltage integration starting moment t Vol is found, starting from the voltage integration starting moment t Vol to the 12 th sampling point after the protection starting point, summing the absolute value of the three-phase small-difference current variation of each sampling point to obtain three-phase current variation absolute value integration:
the invention determines a basic action threshold curve by the following steps:
The base action threshold is defined as K threshold(t).Kthreshold (t) as an enumeration function that exhibits a high degree of discretization within 12 sampling points (i.e., within 5 ms) after the guard is initiated. The method is divided into the following steps, wherein the per unit value is taken as a reference value by taking the rated effective value of the high-voltage side phase current.
(1) After the protection starting point t start has been determined, but under the condition that the current starting time t Cur has not been found, making the temporary basic action threshold from the protection starting time t start to the current time t be K threshold (t) =9p.u.;
(2) Under the condition that the protection starting point t start has been determined and the current start time t Cur has been found, first a parameter describing the shape of the base action threshold curve is defined according to the gear into which the protection is entered:
1) If the gear is protected to be in the gear 0, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., and the fixed value of the t start +4 point to the t start +12 point is 90p.u.;
2) If the gear 1 is protected, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., the fixed value of the t start +4 point is 5p.u., and the fixed value of the t start +6 point to the t start +12 point is 90p.u.
The invention also provides a peak braking method, which defines the increment function of the three-phase peak braking action threshold asA total peak brake actuation threshold delta function S threshold (t) is defined. Under the condition that the guard start point t start has been determined and the current integration start time t Cur has been found, from time t Cur, the value of the total peak brake actuation threshold delta function for each sample point is determined as per equation (18):
Wherein S coe is a peak brake coefficient, which is used to adjust the sensitivity of the protection method. The peak brake coefficient S coe is determined by a number of steps:
1) Basic brake coefficient definition step
When the protection starting point t start is determined, if the protection enters the gear 0 through the current integration starting moment judging method, entering the step 2); otherwise S coe =1.5.
2) Zero sequence quantity reducing brake coefficient step
When the protection start point t start has been determined and the protection enters gear 0, it is judged whether the protection start point satisfies the mathematical relationship of expression (19):
If the protection starting point t start satisfies both the first expression and the second expression in expression (19), S coe =0.6; otherwise, S coe =1.2.
The invention also provides a ratio braking method for ensuring the reliability of the protection method, so that the protection method is reliable and does not act under the condition of off-zone faults. The phase separation ratio braking amount is determined according to the formula (20):
Where k BK is the ratio brake coefficient. When the protection starting point t start has been determined, the absolute value of the three-phase current variation shown in the formula (17) is integrated only And when the operation is larger than B A、BB、BC defined by the formula (20), the corresponding phase protection device is allowed to operate.
Fig. 1 is a schematic diagram of a transformer fault simulation model, fig. 2 is a protection start logic block diagram, and fig. 3 is an action logic block diagram. Referring to fig. 1 to 3, the protection method of the present invention determines whether to operate according to the following steps:
1) Judging whether protection is started or not by a protection starting moment judging method for the current sampling point t; if the protection is started, taking the current sampling point as a protection starting point t start; then determining a protection judging result category by a voltage integration starting moment judging method, entering a current integration starting moment judging step only when the judging result category is a fault category, otherwise directly locking protection;
2) Determining a gear which is protected by a current integration starting moment judging method, and determining a current integration starting moment t Cur; and determining a basic action threshold curve parameter and a peak braking coefficient according to the gear which is protected.
3) Starting from a voltage integration starting time t Vol to a 12 th sampling point after a protection starting point, obtaining the absolute value integration of the three-phase current variation; determining a basic action threshold curve K threshold and a total peak brake increment curve S threshold through a method (3) and a method (4) respectively;
4) Equation (21) is fully satisfied only at any sampling point after the current integration start time (inclusive):
Then its action outlet is allowed. Wherein the method comprises the steps of Representing the phases.
The present invention utilizes the transformer fault simulation model shown in fig. 1 to perform in-and-out fault simulation verification.
(1) The simulation verification of the serious faults of the phase A in the development area of the transformer fault simulation model is utilized, the obtained voltage and current integration initial time is shown in fig. 4, the current variation quantity integration criterion and the floating threshold curve are shown in fig. 5, the basic action threshold curve and the ratio peak value braking increment curve are shown in fig. 6, and the ratio braking result is shown in fig. 7. Therefore, the protection method can act correctly, sensitively and rapidly under the fault scene, and the action time is within 2.5 ms.
(2) The voltage and current integration starting time is shown in figure 8, the current variation integration criterion and the floating threshold curve are shown in figure 9, the basic action threshold curve and the ratio peak value braking increment curve are shown in figure 10, and the ratio braking result is shown in figure 11. The protection method can accurately, sensitively and rapidly act in the fault scene, and the action time is within 2 ms.
(3) The voltage and current integration starting time is shown in fig. 12 by utilizing the simulation verification of the ground fault of the A phase outside the transformer fault simulation model development area. Therefore, the protection method can reliably and non-act in the fault scene, the sampling point meeting the condition cannot be found by the current integration starting time method, and the protection is directly locked.
(4) The simulation verification of the A-phase space charge surge current is carried out by using a transformer fault simulation model, and the obtained voltage and current integration initial time is shown in figure 13. Therefore, in the scene, the voltage starting criterion of the point after the protection starting point cannot be met due to the large difference between the voltage point and the current point, so that reliable locking and action capturing are protected.
In summary, according to the invention, whether protection is started or not is judged through rules for the current sampling point; if the protection starting point is started, the current sampling point is taken as the protection starting point, the protection judging result category is determined through a rule, and the next step is started only when the judging result category is a fault category, otherwise, the protection is directly locked; determining a gear which is protected by a rule, and determining the starting moment of current integration; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected; starting from the starting time of voltage integration to the 12 th sampling point after the protection starting point, obtaining the absolute value integration of the three-phase current variation; respectively determining a basic action threshold curve and a total peak braking increment curve; and allowing the sampling point to act as an outlet only when any sampling point after the current integration starting moment completely meets the preset requirement. The invention can realize the action within 2ms under the serious faults of the transformer, and reliably does not act in the occasions such as inrush current, CT disconnection, out-of-zone faults and the like, and has excellent performance, thereby obviously improving the reliability of the stable operation of the transformer.
Exemplary apparatus
The invention also provides a transformer quick-break protection device based on the electric quantity abrupt change starting time difference, which comprises:
the first judging module is used for judging whether protection is started or not according to a preset protection starting moment judging rule for the current sampling point t;
The second judging module is used for taking the current sampling point as a protection starting point t start if the protection is started, then determining a protection judging result category through a preset voltage integration starting moment judging rule, entering a current integration starting moment judging step only when the judging result category is a fault category, and directly locking the protection if the judging result category is not a fault category;
the third judging module is used for determining the gear which is protected and enters through a preset current integration starting moment judging rule, and determining a current integration starting moment t Cur; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected;
The determining module is used for obtaining the absolute value integral of the three-phase current variation from the voltage integral starting time t Vol to the 12 th sampling point after the protection starting point; respectively determining a basic action threshold curve K threshold (t) and a total peak braking increment curve S threshold (t) in a preset mode;
an action module for completely satisfying any sampling point only after the current integration starting time When the sampling point is allowed to act as an outlet: in the/>Integrating the absolute value of the three-phase current variation quantity,/>Representing each phase, K threshold (t) is the base action threshold curve, S threshold (t) is the total peak brake delta curve,/>The three-phase ratio is regulated.
The transformer quick-break protection device based on the electric quantity abrupt change starting time difference in the embodiment of the invention corresponds to the transformer quick-break protection method based on the electric quantity abrupt change starting time difference in another embodiment of the invention, and is not described herein.
Exemplary electronic device
Fig. 14 is a structure of an electronic device provided in an exemplary embodiment of the present invention. As shown in fig. 14, the electronic device 140 includes one or more processors 141 and memory 142.
Processor 141 may be a Central Processing Unit (CPU) or other form of processing unit having data processing and/or instruction execution capabilities and may control other components in the electronic device to perform desired functions.
Memory 142 may include one or more computer program products that may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, random Access Memory (RAM) and/or cache memory (cache), and the like. The non-volatile memory may include, for example, read Only Memory (ROM), hard disk, flash memory, and the like. On which one or more computer program instructions may be stored that may be executed by processor 141 to implement the method of information mining historical change records and/or other desired functions of the software program of the various embodiments of the present invention described above. In one example, the electronic device may further include: input device 143 and output device 144, which are interconnected by a bus system and/or other forms of connection mechanisms (not shown).
In addition, the input device 143 may also include, for example, a keyboard, a mouse, and the like.
The output device 144 can output various information to the outside. The output 144 may include, for example, a display, speakers, a printer, and a communication network and remote output devices connected thereto, etc.
Of course, only some of the components of the electronic device relevant to the present invention are shown in fig. 14 for simplicity, components such as buses, input/output interfaces, and the like being omitted. In addition, the electronic device may include any other suitable components depending on the particular application.
Exemplary computer program product and computer readable storage Medium
In addition to the methods and apparatus described above, embodiments of the invention may also be a computer program product comprising computer program instructions which, when executed by a processor, cause the processor to perform steps in a method according to various embodiments of the invention described in the "exemplary methods" section of this specification.
The computer program product may write program code for performing operations of embodiments of the present invention in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server.
Furthermore, embodiments of the present invention may also be a computer-readable storage medium, having stored thereon computer program instructions which, when executed by a processor, cause the processor to perform the steps in a method of mining history change records according to various embodiments of the present invention described in the "exemplary methods" section above in this specification.
The computer readable storage medium may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The basic principles of the present invention have been described above in connection with specific embodiments, but it should be noted that the advantages, benefits, effects, etc. mentioned in the present invention are merely examples and not intended to be limiting, and these advantages, benefits, effects, etc. are not to be construed as necessarily possessed by the various embodiments of the invention. Furthermore, the specific details disclosed herein are for purposes of illustration and understanding only, and are not intended to be limiting, as the invention is not necessarily limited to practice with the above described specific details.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, so that the same or similar parts between the embodiments are mutually referred to. For system embodiments, the description is relatively simple as it essentially corresponds to method embodiments, and reference should be made to the description of method embodiments for relevant points.
The block diagrams of the devices, systems, apparatuses, systems according to the present invention are merely illustrative examples and are not intended to require or imply that the connections, arrangements, configurations must be made in the manner shown in the block diagrams. As will be appreciated by one of skill in the art, the devices, systems, apparatuses, systems may be connected, arranged, configured in any manner. Words such as "including," "comprising," "having," and the like are words of openness and mean "including but not limited to," and are used interchangeably therewith. The terms "or" and "as used herein refer to and are used interchangeably with the term" and/or "unless the context clearly indicates otherwise. The term "such as" as used herein refers to, and is used interchangeably with, the phrase "such as, but not limited to.
The method and system of the present invention may be implemented in a number of ways. For example, the methods and systems of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, firmware. The above-described sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above unless specifically stated otherwise. Furthermore, in some embodiments, the present invention may also be embodied as programs recorded in a recording medium, the programs including machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.
It is also noted that in the systems, devices and methods of the present invention, components or steps may be disassembled and/or assembled. Such decomposition and/or recombination should be considered as equivalent aspects of the present invention. The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the invention to the form disclosed herein. Although a number of example aspects and embodiments have been discussed above, a person of ordinary skill in the art will recognize certain variations, modifications, alterations, additions, and subcombinations thereof.
Claims (10)
1. The method for protecting the quick break of the transformer based on the electric quantity abrupt change starting time difference is characterized by comprising the following steps of:
Judging whether protection is started or not according to a preset protection starting time judging rule for the current sampling point t;
If the protection is started, taking the current sampling point as a protection starting point t start, then determining a protection judging result category through a preset voltage integration starting moment judging rule, and entering a current integration starting moment judging step only when the judging result category is a fault category, otherwise directly locking the protection;
Determining a gear which is protected by a preset current integration starting moment judgment rule, and determining a current integration starting moment t Cur; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected;
Starting from a voltage integration starting time t Vol to a 12 th sampling point after a protection starting point, obtaining the absolute value integration of the three-phase current variation; respectively determining a basic action threshold curve K threshold (t) and a total peak braking increment curve S threshold (t) in a preset mode;
Any sampling point is fully satisfied only after the current integration starting time When the sampling point is allowed to act as an outlet: in the/>Integrating the absolute value of the three-phase current variation quantity,/>Representing each phase, K threshold (t) is the base action threshold curve, S threshold (t) is the total peak brake delta curve,/>The three-phase ratio is regulated.
2. The method according to claim 1, wherein the protection start time judgment rule is determined by:
Defining the protection starting time as t start, and setting t start to 0; defining three-phase currents at the high-voltage side of the transformer as i A、iB、iC respectively, and obtaining the variation of the three-phase currents according to the formula (1) Wherein t is the current time:
then the square sum of the inter-phase current difference is defined according to the formula (2)
Defining rated starting current I σ according to formula (3);
Wherein, I e is the effective value of the rated current value marked on the transformer nameplate, and I n is the CT rated current;
then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (4)
For the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to the formula (5):
In the middle of For the starting coefficient, when the difference flow reaches 0.5p.u., the starting setting can be sensitively started; when the three formulas in the formula (5) are all satisfied, defining the time t-2 as the suspected starting time/>
And defining a high-voltage side zero sequence current i 0 according to a formula (6):
i0(t)＝(iA(t)+iB(t)+iC(t))/3 (6)
and defining a high-voltage side zero sequence current maximum value i 0MAX according to the formula (7):
i0MAX(t)＝max{i0(t)|t∈[t-24,t-12]} (7)
for the current time t, the previous sampling point time t-1 and the previous two sampling point times t-2, starting and judging three sampling points according to a formula (8):
In the middle of The zero sequence starting coefficient is set by sensitively starting when the difference flow reaches 0.5 p.u.; when the three formulas in the formula (8) are all satisfied, defining the time t-2 as the suspected starting time/>For any sampling point, when the sampling point belongs to suspected starting time/>Or suspected start-up time/>In any case, judging the sampling point as the protection starting time, and covering the time stamp of the sampling point with the value of t start; and once t start is not equal to 0, stopping the protection starting time criterion judgment of all subsequent sampling points.
3. The method according to claim 1, characterized in that the voltage integration start time judgment rule is determined by:
defining the three-phase voltage of the high-voltage side of the transformer as u A、uB、uC; defining the effective value of the high-voltage side phase voltage as U e; for any sampling point needed to judge the starting moment of voltage integration, the change amount of the three-phase voltage is obtained according to the formula (9)
Then the square sum of the inter-phase current difference is defined according to (10)
Then defining the square sum maximum value of inter-phase current difference in a specific time window according to the formula (11)
Under the condition that the protection starting point t start is determined, dividing the judging result into three types of inrush current, fault and CT disconnection according to the protection starting point and the conditions of all sampling points nearby the protection starting point; defining voltage integration starting time t Vol according to different categories of judgment results;
When the class of the judgment result is the inrush class, for the sampling point t start -1 (i.e., the sampling point immediately before the protection starting point), it is judged whether it satisfies the formula (12):
In the middle of Setting the initial low voltage value according to the maximum unbalance of the system, and setting according to the condition that the sampling point (namely the sampling point t start -1) before the protection starting moment is not satisfied with the formula (12); if the sampling point meets the above formula, judging that the protection enters the inrush current locking logic, and setting t Vol to 0; otherwise, judging the fault class;
When the type of the judging result is a fault type, the fixed value is set according to the condition that the protection starting time meets the formula (12) and the sampling point before the protection starting time does not meet the formula (12) under the condition of the fault in the minimum area; for a sampling point t start, judging whether the sampling point t start meets the formula (12); if yes, judging that protection enters fault action logic, and taking the time stamp of the sampling point as a voltage integration starting time t Vol; otherwise, judging the CT broken line;
when the type of the judgment result is the CT disconnection type, judging whether the sampling point t start +1 (namely, the sampling point after the protection starting point) meets the formula (13):
In the method, in the process of the invention, Setting the voltage integration initial high fixed value according to 2 times of the right bracket in the formula (12); if yes, the same protection enters fault action logic, and the time stamp of the sampling point is taken as a voltage starting time t Vol; otherwise, the protection is determined to enter CT broken line locking logic, and t Vol is set to 0.
4. The method according to claim 1, characterized in that the current integration start time judgment rule is determined by:
When the scene is determined to be gear 0, on the condition that the protection starting point t start has been determined and t Vol is not equal to 0, for the sampling point t start, whether the formula (13) is established is determined:
In the middle of Starting a constant value for current integration of the gear 0; if so, the protection starting point t start is considered to meet the current integration starting condition, a protection entering gear 0 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, trying to enter the gear 1 to continue judgment;
When the scene is determined to be gear 1, on the condition that the protection starting point t start is determined and t Vol is not equal to 0, for the sampling point t start +1, whether the formula (14) is established is determined:
In the method, in the process of the invention, Starting a constant value for current integration of the gear 1;
if so, the sampling point t start +1 is considered to meet the current integration starting condition, a protection entering gear 1 is defined, the time stamp of the sampling point is taken as the current integration starting time t Cur, and the next operation is carried out; otherwise, judging that the protection enters other gears, and directly locking the protection by a current integration starting moment judging method.
5. The method according to claim 1, wherein the step of obtaining the absolute value integral of the three-phase current variation from the voltage integration start time t Vol to the 12 th sampling point after the protection start point includes:
defining the low-voltage side three-phase current of the transformer as i a,ib,ic, and obtaining the variation of the low-voltage side three-phase current according to the formula (15) Wherein t is the current time:
then, the absolute value of the three-phase small difference flow variation is obtained according to the formula (16), namely:
Under the condition that the current integration starting moment is not found after the protection is started, the absolute value of the three-phase small difference current variation at the current moment is set to be 0;
After the protection is started and under the condition that the voltage integration starting moment t Vol is found, starting from the voltage integration starting moment t Vol to the 12 th sampling point after the protection starting point, summing the absolute value of the three-phase small-difference current variation of each sampling point according to the formula (17) to obtain three-phase current variation absolute value integration:
6. The method according to claim 1, wherein the determining, by a preset manner, the base action threshold curve K threshold (t) and the total peak brake increment curve S threshold (t), respectively, comprises:
After the protection starting point t start has been determined, but under the condition that the current starting time t Cur has not been found, making the temporary basic action threshold from the protection starting time t start to the current time t be K threshold (t) =9p.u.;
under the condition that the protection starting point t start has been determined and the current start time t Cur has been found, first a parameter describing the shape of the base action threshold curve is defined according to the gear into which the protection is entered:
If the gear is protected to be in the gear 0, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., and the fixed value of the t start +4 point to the t start +12 point is 90p.u.;
If the gear 1 is protected, the fixed value of the t start +2 point is 4p.u., the fixed value of the t start +3 point is 4.5p.u., the fixed value of the t start +4 point is 5p.u., and the fixed value of the t start +6 point to the t start +12 point is 90p.u.
7. The method as recited in claim 1, further comprising:
defining three-phase peak value braking action threshold increment function as Defining a total peak brake actuation threshold delta function S threshold (t);
Under the condition that the guard start point t start has been determined and the current integration start time t Cur has been found, from time t Cur, the value of the total peak brake actuation threshold delta function for each sample point is determined as per equation (18):
wherein S coe is a peak brake coefficient, which is used to adjust the sensitivity of the protection method.
8. The utility model provides a transformer quick break protection device based on electric quantity abrupt change starting time difference which characterized in that includes:
the first judging module is used for judging whether protection is started or not according to a preset protection starting moment judging rule for the current sampling point t;
The second judging module is used for taking the current sampling point as a protection starting point t start if the protection is started, then determining a protection judging result category through a preset voltage integration starting moment judging rule, entering a current integration starting moment judging step only when the judging result category is a fault category, and directly locking the protection if the judging result category is not a fault category;
the third judging module is used for determining the gear which is protected and enters through a preset current integration starting moment judging rule, and determining a current integration starting moment t Cur; determining basic action threshold curve parameters and peak braking coefficients according to the gear which is protected;
The determining module is used for obtaining the absolute value integral of the three-phase current variation from the voltage integral starting time t Vol to the 12 th sampling point after the protection starting point; respectively determining a basic action threshold curve K threshold (t) and a total peak braking increment curve S threshold (t) in a preset mode;
an action module for completely satisfying any sampling point only after the current integration starting time When the sampling point is allowed to act as an outlet: in the/>Integrating the absolute value of the three-phase current variation quantity,/>Representing each phase, K threshold (t) is the base action threshold curve, S threshold (t) is the total peak brake delta curve,/>The three-phase ratio is regulated.
9. A computer readable storage medium, characterized in that the storage medium stores a computer program for executing the method of any of the preceding claims 1-7.
10. An electronic device, the electronic device comprising:
A processor;
a memory for storing the processor-executable instructions;
The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method of any of the preceding claims 1-7.
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