CN118100094A - Transformer quick-break protection method and device based on starting time difference of electrical quantity mutation - Google Patents

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

Transformer quick-break protection method and device based on starting time difference of electrical quantity mutation

Technical Field

The present invention relates to the field of electrical technology, and more specifically, to a transformer quick-break protection method and device based on a start time difference of electrical quantity mutation.

Background technique

As the main equipment of the power system, the safe and reliable operation of the power transformer is of vital importance. When an internal fault occurs in the transformer, the transformer relay protection device can detect and remove the fault, thereby ensuring the equipment safety of the transformer and the stable operation of the power system.

As the main protection of transformers, current differential protection is widely used because of its simple principle and good selectivity. Conventional differential protection is equipped with corresponding locking elements to avoid false operation due to abnormal conditions such as CT saturation and excitation inrush current, which are not caused by internal faults. Therefore, the action time of conventional differential protection is closely related to the performance of these locking elements. At the same time, in order to avoid the protection action speed being affected by the above-mentioned locking elements and unable to quickly cut off the fault when a serious internal fault occurs in the transformer, a differential quick-break protection element without any locking is usually configured in the transformer protection device. According to the requirements of relevant technical standards, the action time of differential protection shall not exceed 30ms, and the differential breaking action time shall not exceed 20ms. However, in recent years, in the case of serious faults, the fault current rises very fast, the energy accumulates rapidly in a short time, and the heat cannot be released in time, which eventually leads to explosion and combustion of the transformer. In order to solve this problem, the transformer differential breaking protection is required to identify the fault and act within 5ms in the case of serious faults; however, the conventional transformer differential breaking protection has a high setting value and a slow action speed, which is difficult to meet the speed requirements in principle. Therefore, it is urgent to propose a differential protection method that can quickly identify surge characteristics in surge scenarios, ensure protection safety and reliability, and quickly identify fault characteristics in fault scenarios to achieve ultra-high-speed and ultra-sensitive action.

Summary of the invention

In order to solve the problems of insufficient sensitivity and slow action speed of the existing fast differential quick-trip protection based on sampling values under severe transformer faults, the present invention provides a transformer quick-trip protection method and device based on the starting time difference of electrical quantity mutation.

According to one aspect of the present invention, there is provided a transformer quick-break protection method based on the starting time difference of electrical quantity mutation, comprising:

For the current sampling point t, determine whether the protection is started by using the predetermined protection start time judgment rule;

If the protection is started, the current sampling point is used as the protection start point t _start , and then the protection judgment result category is determined by the predetermined voltage integration start time judgment rule. Only when the judgment result category is a fault type, the current integration start time judgment step is entered, otherwise the protection is directly locked;

Determine the gear position entered by the protection through the predetermined current integration starting time judgment rule, and determine the current integration starting time t _Cur ; determine the basic action threshold curve parameters and peak braking coefficient according to the gear position entered by the protection;

From the voltage integration start time t _Vol to the 12th sampling point after the protection start point, the absolute value integral of the three-phase current change is obtained; the basic action threshold curve K _threshold (t) and the total peak braking increment curve S _threshold (t) are determined respectively by a preset method;

Only when any sampling point after the start of current integration completely satisfies When , the sampling point is allowed to act as an export: In the formula, /> is the absolute value integral of the three-phase current change, /> represents each phase, K _threshold (t) is the basic action threshold curve, S _threshold (t) is the total peak braking increment curve, /> is the three-phase ratio braking amount.

Optionally, the protection start time judgment rule is determined in the following manner:

Define the protection start time as t _start and set t _start to 0; define the three-phase currents on the high-voltage side of the transformer as i _A , i _B , and i _C , and calculate the change of the three-phase current according to formula (1): Where t is the current time:

Then define the sum of squares of the phase current difference according to formula (2):

Then define the rated starting current I _σ according to formula (3);

Where, _Ie is the effective value of the rated current marked on the transformer nameplate, and _In is the CT rated current;

Then, according to formula (4), the maximum value of the sum of squares of the phase current difference within a specific time window is defined as:

For the current time t, the previous sampling point time t-1, and the previous two sampling points time t-2, the three sampling points are started according to formula (5):

In the formula is the starting coefficient, and it can be sensitively started and adjusted when the differential current reaches 0.5pu; when all three equations in equation (5) are satisfied, the time t-2 is defined as the suspected starting time/>

Then define the high voltage side zero sequence current i ₀ according to formula (6):

i ₀ (t) = (i _A (t) + i _B (t) + i _C (t)) / 3 (6)

Then define the maximum value of the zero-sequence current i _0MAX on the high-voltage side according to formula (7):

i _{0 MAX} ( t ) = max { i ₀ ( t ) | t ∈ [ t - 24 , t - 12 ] } (7)

For the current time t, the previous sampling point time t-1, and the previous two sampling points time t-2, the three sampling points are started according to formula (8):

In the formula is the zero-sequence starting coefficient, and can be sensitively started and adjusted when the differential current reaches 0.5pu; when all three equations in equation (8) are satisfied, the time t-2 is defined as the suspected starting time/> For any sampling point, when the sampling point belongs to the suspected start time/> Or suspected start time/> If any of the above conditions is met, the sampling point is judged as the protection start time, and the timestamp of the sampling point is overwritten with the value of t _start ; once t _start ≠ 0, the protection start time judgment criteria of all subsequent sampling points are stopped.

Optionally, the voltage integration start time judgment rule is determined in the following manner:

Define the three-phase voltage on the high-voltage side of the transformer as u _A , u _B , and u _C ; define the effective value of the phase voltage on the high-voltage side as U _e ; for any sampling point where the voltage integration start time needs to be determined, calculate the change in the three-phase voltage according to formula (9):

Then define the sum of squares of the phase current difference according to formula (10):

Then, according to formula (11), the maximum value of the sum of squares of the phase current difference within a specific time window is defined as:

Under the condition that the protection start point t _start has been determined, the judgment results are divided into three categories: inrush current, fault and CT disconnection according to the conditions of the protection start point and the sampling points nearby; the voltage integration start time t _Vol is defined according to the different categories of the judgment results;

When the category of the judgment result is the surge type, for the sampling point t _start -1 (that is, the sampling point before the protection start point), it is judged whether it satisfies formula (12):

In the formula is the voltage starting low setting value, which is set according to the maximum unbalance of the system and the sampling point before the protection start time (i.e., sampling point t _start -1) when there is no abnormality and does not satisfy equation (12). If the sampling point satisfies the above equation, it is determined that the protection enters the inrush current blocking logic and t _Vol is set to 0; otherwise, it enters the fault type judgment.

When the category of the judgment result is fault type, the setting value is set according to the minimum zone fault, the protection start time satisfies formula (12), and the sampling point before the protection start time does not satisfy formula (12); for the sampling point t _start , it is judged whether it satisfies formula (12); if it does, it is determined that the protection enters the fault action logic, and the timestamp of this sampling point is used as the voltage integration start time t _Vol ; otherwise, it enters the CT disconnection type judgment;

When the category of the judgment result is CT disconnection, for the sampling point t _start +1 (that is, the sampling point after the protection start point), it is judged whether it satisfies formula (13):

In the formula, is the starting high set value of voltage integration. The set value is set as twice the value in the bracket on the right side of formula (12). If it is satisfied, it is regarded as the protection entering the fault action logic, and the timestamp of this sampling point is taken as the voltage starting time t _Vol . Otherwise, it is determined that the protection enters the CT disconnection blocking logic, and t _Vol is set to 0.

Optionally, the current integration start time judgment rule is determined in the following manner:

When the judgment scene is gear position 0, under 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 formula (13) is established:

In the formula is the starting value of the current integration at gear 0; if it is established, it is considered that the protection start point t _start meets the current integration starting condition, and the protection is defined to enter gear 0, and the timestamp of this sampling point is the current integration starting time t _Cur , and the next operation is performed; otherwise, try to enter gear 1 to continue the judgment;

When the judgment scene is gear 1, under 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 formula (14) is established:

In the formula, It is the starting value of current integration in gear 1;

If it is established, it is considered that the sampling point t _start +1 meets the current integration starting condition, and the protection is defined to enter gear 1. The timestamp of this sampling point is taken as the current integration starting time t _Cur , and the next operation is performed; otherwise, it is determined that the protection enters other gears, and the current integration starting time judgment method directly locks the protection.

Optionally, the step of obtaining the absolute value integral of the three-phase current variation from the voltage integration start time t _Vol to the 12th sampling point after the protection start point includes:

Define the three-phase currents on the low-voltage side of the transformer as i _a , i _b , i _c , and calculate the change of the three-phase current on the low-voltage side according to formula (15): Where t is the current time:

Then, the absolute value of the change in the three-phase small differential current is calculated according to formula (16), that is:

After the protection is started but the starting time of current integration is not found, the absolute value of the change of the three-phase small differential current at the current moment is set to 0;

After the protection is started and the voltage integration start time t _Vol has been found, from the voltage integration start time t _Vol to the 12th sampling point after the protection start point, the absolute value of the three-phase small differential current change at each sampling point is summed according to formula (17) to obtain the absolute value integral of the three-phase current change:

Optionally, the determining the basic action threshold curve K _threshold (t) and the total peak braking increment curve S _threshold (t) respectively by a preset manner includes:

After the protection start point t _start has been determined, but the current start time t _Cur has not been found, the temporary basic action threshold from the protection start time t _start to the current time t is set to K _threshold (t) = 9 p.u.;

Under the condition that the protection start point t _start has been determined and the current start time t _Cur has been found, the parameters describing the shape of the basic action threshold curve are first defined according to the gear entered by the protection:

If the protection enters gear 0, the fixed value at point t _start +2 is set to 4 p.u., the fixed value at point t _start +3 is set to 4.5 pu, and the fixed values from point t _start +4 to point t _start +12 are set to 90 p.u.;

If the protection enters gear position 1, the fixed value at point t _start + 2 is set to 4 p.u., the fixed value at point t _start + 3 is set to 4.5 pu, the fixed value at point t _start + 4 is set to 5 p.u., and the fixed values from point t _start + 6 to point t _start + 12 are set to 90 p.u.

Optionally, the method further comprises:

The three-phase peak braking action threshold increment function is defined as Define the total peak braking action threshold increment function S _threshold (t);

Under the condition that the protection start point t _start has been determined and the current integration start time t _Cur has been found, starting from time t _Cur , the value of the total peak braking action threshold increment function of each sampling point is determined according to formula (18):

Among them, _Scoe is the peak braking coefficient, which is used to adjust the sensitivity of the protection method.

According to another aspect of the present invention, there is provided a transformer quick-break protection device based on the starting time difference of electrical quantity mutation, comprising:

A first judgment module is used to judge whether the protection is started according to a predetermined protection start time judgment rule for the current sampling point t;

The second judgment module is used to, if the protection is started, take the current sampling point as the protection start point t _start , and then determine the protection judgment result category according to the predetermined voltage integration start time judgment rule, and only when the judgment result category is a fault category, enter the current integration start time judgment step, otherwise directly lock the protection;

The third judgment module is used to determine the gear entered by the protection through a predetermined current integration start time judgment rule, and determine the current integration start time t _Cur ; determine the basic action threshold curve parameters and the peak braking coefficient according to the gear entered by the protection;

The determination module is used to obtain the absolute value integral of the three-phase current change from the voltage integration start time t _Vol to the 12th sampling point after the protection start point; determine the basic action threshold curve K _threshold (t) and the total peak braking increment curve S _threshold (t) respectively by a preset method;

Action module, used only when any sampling point after the current integration start moment completely satisfies When , the sampling point is allowed to act as an export: In the formula, /> is the absolute value integral of the three-phase current change, /> represents each phase, K _threshold (t) is the basic action threshold curve, S _threshold (t) is the total peak braking increment curve, /> is the three-phase ratio braking amount.

According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method described in any one of the above aspects of the present invention.

According to another aspect of the present invention, an electronic device is provided, comprising: a processor; a memory for storing instructions executable by the processor; the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of the above aspects of the present invention.

The present invention determines whether the protection is started for the current sampling point through rules; if it is started, the current sampling point is used as the protection start point, and the protection judgment result category is determined through rules. Only when the judgment result category is a fault category, the next step is entered, otherwise the protection is directly locked; the gear entered by the protection is determined through rules, and the current integration start time is determined; the basic action threshold curve parameters and peak braking coefficient are determined according to the gear entered by the protection; from the start time of voltage integration to the 12th sampling point after the protection start point, the absolute value integral of the three-phase current change is obtained; the basic action threshold curve and the total peak braking increment curve are determined respectively; only when any sampling point after the current integration start time fully meets the preset requirements, the sampling point is allowed to act. The present invention can realize action within 2ms under severe transformer faults, and reliably not act in occasions such as inrush current, CT disconnection, and out-of-zone faults, with superior performance, thereby significantly improving the reliability of stable operation of the transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

FIG1 is a schematic diagram of a transformer fault simulation model in an embodiment of the present invention;

FIG2 is a protection start logic block diagram in an embodiment of the present invention;

FIG3 is an action logic block diagram of an embodiment of the present invention;

4 is a schematic diagram of the voltage and current integration start time under a severe fault of phase A in the zone according to an embodiment of the present invention;

5 is a schematic diagram of a current change integral criterion and a floating threshold curve under a severe fault of phase A in a zone in an embodiment of the present invention;

6 is a schematic diagram of a basic action threshold curve and a ratio peak braking increment curve under a severe fault of phase A in the zone according to an embodiment of the present invention;

7 is a schematic diagram of the ratio braking result under a severe fault of phase A in the zone according to an embodiment of the present invention;

8 is a schematic diagram of the voltage and current integration start time under a high-resistance fault of phase A in the zone according to an embodiment of the present invention;

9 is a schematic diagram of a current change integral criterion and a floating threshold curve under a phase A high-resistance fault in the zone according to an embodiment of the present invention;

10 is a schematic diagram of a basic action threshold curve and a ratio peak braking increment curve under a high-resistance fault of phase A in the zone according to an embodiment of the present invention;

11 is a schematic diagram of a ratio braking result under a high-resistance fault of phase A in the zone according to an embodiment of the present invention;

12 is a schematic diagram of the voltage and current integration start time under an out-of-zone A phase grounding fault in an embodiment of the present invention;

13 is a schematic diagram of the voltage and current integration start time of the A-phase empty-charge inrush current in an embodiment of the present invention;

FIG. 14 is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

It should be understood that in the description of all embodiments of the present invention, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The present invention takes into account that traditional AC protection devices usually implement protection functions at a frequency of 50Hz and a sampling rate of 1200Hz. Therefore, there are only 6 sampling points available for protection calculation within 5ms after the protection is started, and there is less information available. On the one hand, only 6 sampling points cannot peek into the full-cycle time domain characteristics of each phase electrical quantity after the fault, and the frequency domain extraction method based on the short-time window will also have a large error, so there are great difficulties in the fault feature analysis level; on the other hand, even if the time-frequency domain characteristics of the phase electrical quantity can be predicted and obtained by certain methods, and the fault and other abnormalities can be successfully distinguished, too few sampling points that meet the action conditions may also cause incorrect protection action, seriously threatening the safety of the transformer. Therefore, the design should not stick to traditional ideas.

Since the voltage leads the flux change by 90°, and due to the hysteresis loop characteristics of the ferromagnetic element, the current will change slowly at first; after a certain period of time, when the ferromagnetic element is saturated, the current will rise rapidly because the flux continues to rise, that is, during inrush current, the starting time of the transformer voltage change will be ahead of the starting time of the current change, and the leading time will be more obvious; but during a fault, it will not be the case, the voltage and current will change at the same time, and the change will be very obvious. In this way, if the time difference between the voltage change time and the current change time can be detected, the excitation inrush current can be easily avoided, thereby simply targeting fault scenarios, abnormally large numbers and CT disconnection problems, providing a solid foundation for the design of ultra-high performance transformer differential disconnection protection.

The present invention first proposes a method for determining the start time. The method for determining the start time is divided into three parts: 1) a method for determining the protection start time; 2) a method for determining the voltage integration start time; 3) a method for determining the current integration start time. The implementation method is as follows:

1) Protection start time judgment method

First, define the protection start time as t _start and set it to 0. Define the three-phase currents on the high-voltage side of the transformer as i _A , i _B , and i _C , and calculate the change of the three-phase current according to formula (1): Where t is the current time:

Then define the sum of squares of the phase current difference according to formula (2):

Then define the rated starting current I _σ according to formula (3).

Where _{Ie is} the effective value of the rated current marked on the transformer nameplate, and _In is the CT rated current.

Then, according to formula (4), the maximum value of the sum of squares of the phase current difference within a specific time window is defined as:

For the current time t, the previous sampling point time t-1, and the previous two sampling points time t-2, the three sampling points are started according to formula (5):

In the formula is the starting coefficient, and it can be sensitively started and adjusted when the differential current reaches 0.5pu. When all three equations in equation (5) are satisfied, the time t-2 is defined as the suspected starting time/>

Then define the high voltage side zero sequence current i ₀ according to formula (6):

i ₀ (t) = (i _A (t) + i _B (t) + i _C (t)) / 3 (6)

Then define the maximum value of the zero-sequence current i _0MAX on the high-voltage side according to formula (7):

i _{0 MAX} ( t ) = max { i ₀ ( t ) | t ∈ [ t - 24 , t - 12 ] } (7)

For the current time t, the previous sampling point time t-1, and the previous two sampling points time t-2, the three sampling points are started according to formula (8):

In the formula is the zero-sequence starting coefficient, and can be sensitively started and adjusted when the differential current reaches 0.5pu. When all three equations in equation (8) are satisfied, the time t-2 is defined as the suspected starting time/> For any sampling point, when the sampling point belongs to the suspected start time/> Or suspected start time/> If any of the above conditions is met, the sampling point is judged as the protection start time, and the timestamp of the sampling point is overwritten with the value of t _start ; once t _start ≠ 0, the protection start time judgment criteria of all subsequent sampling points are stopped.

2) Method for determining the starting time of voltage integration

The method for determining the start time of voltage integration is similar to the method for determining the protection start time in (1). First, define the three-phase voltage on the high-voltage side of the transformer as _uA , _uB , and _uC ; define the effective value of the phase voltage on the high-voltage side as _Ue ; for any sampling point that needs to determine the start time of voltage integration, calculate the change in the three-phase voltage according to formula (9):

Then define the sum of squares of the phase current difference according to formula (10):

Then, according to formula (11), the maximum value of the sum of squares of the phase current difference within a specific time window is defined as:

In particular, under the condition that the protection start point t _start has been determined, according to the conditions of the protection start point and the sampling points nearby, the judgment results of this method can be divided into the following three categories: This method defines the voltage integration start time t _Vol according to different judgment result categories.

① Surge type

For the sampling point t _start -1 (i.e., the sampling point before the protection start point), determine whether it satisfies formula (12):

In the formula is the voltage starting low value, which is set according to the maximum unbalance of the system and the sampling point before the protection start time (i.e., sampling point t _start -1) when there is no abnormality and does not satisfy equation (12). If the sampling point satisfies the above equation, it is determined that the protection enters the inrush current blocking logic and t _Vol is set to 0; otherwise, it enters the fault type judgment.

②Fault type

The setting value is set according to the minimum zone fault (within 20ms after the protection is started, the fault phase small differential current fundamental effective value is about 2.8pu), the protection start time (i.e. sampling point t _start ) satisfies formula (12), and the sampling point before the protection start time (i.e. sampling point t _start -1) does not satisfy formula (12). For the sampling point t _start (i.e. the protection start point), it is judged whether it satisfies formula (12); if it does, it is determined that the protection enters the fault action logic, and the timestamp of this sampling point is used as the voltage integration start time t _Vol ; otherwise, it enters the CT disconnection type judgment.

③CT disconnection

For the sampling point t _start +1 (i.e., the sampling point after the protection start point), determine whether it satisfies formula (13):

In the formula is the voltage integral starting high set value, and the set value is set to 2 times the value in the right bracket of formula (12), in order to reduce the voltage starting sensitivity as much as possible and improve the protection reliability. If it is satisfied, it is regarded as the protection entering the fault action logic, and the timestamp of this sampling point is taken as the voltage starting time t _Vol ; otherwise, it is judged that the protection enters the CT disconnection blocking logic, and t _Vol is set to 0.

3) Method for determining the starting time of current integration

The current integration start time determination method is similar to the protection start time determination method in (1). This determination method retains the calculation results of equations (1) to (4) in method 1) and is divided into two determination scenarios. The present invention refers to these two scenarios as gear position 0 and gear position 1. The determination process is described below:

① Gear position 0

Under the condition that the protection start point t _start has been determined and t _Vol ≠ 0, for the sampling point t _start , determine whether equation (13) holds:

In the formula is the starting value of the current integration at gear 0. If it is established, it is considered that the protection start point t _start meets the current integration starting condition, and the protection is defined to enter gear 0, and the timestamp of this sampling point is taken as the current integration starting time t _Cur , and the next operation is performed; otherwise, try to enter gear 1 to continue the judgment.

② Position 1

Under the condition that the protection start point t _start has been determined and t _Vol ≠ 0, for the sampling point t _start +1, determine whether equation (14) is established:

In the formula is the starting value of the current integration of gear 1. If it is established, it is considered that the sampling point t _start +1 meets the current integration starting condition, and the protection is defined to enter gear 1. The timestamp of this sampling point is taken as the current integration starting time t _Cur , and the next operation is performed; otherwise, it is determined that the protection enters other gears, and the current integration starting time judgment method directly locks the protection.

Furthermore, the present invention also proposes a method for integrating the absolute value of current variation. The method for integrating the absolute value of current variation is divided into two sub-methods: 1) a method for obtaining the absolute value of three-phase small differential current variation; 2) a method for obtaining the absolute value integral of current variation.

1) Method for obtaining the absolute value of the change in the three-phase small differential current

Define the three-phase currents on the low-voltage side of the transformer as i _a , i _b , i _c , and calculate the change of the three-phase current on the low-voltage side according to formula (15): Where t is the current time:

Then, the absolute value of the change in the three-phase small differential current is calculated according to formula (16), that is:

In particular, after the protection is started but the starting time of current integration is not found, the absolute value of the change of the three-phase small differential current at the current moment is set to 0.

2) Method for obtaining the absolute value integral of current change

After the protection is started and the voltage integration start time t _Vol has been found, the absolute value of the three-phase small differential current change at each sampling point is summed from the voltage integration start time t _Vol to the 12th sampling point after the protection start point to obtain the absolute value integral of the three-phase current change:

The present invention determines the basic action threshold curve through the following steps:

The basic action threshold is defined as K _threshold (t). K _threshold (t) is an enumeration function, which is highly discretized within 12 sampling points (i.e., within 5ms) after the protection is started. This method is divided into the following steps. The per-unit value described below is based on the rated effective value of the high-voltage side phase current.

(1) After the protection start point t _start has been determined, but the current start time t _Cur has not yet been found, the temporary basic action threshold from the protection start time t _start to the current time t is set to K _threshold (t) = 9 p.u.;

(2) When the protection start point t _start has been determined and the current start time t _Cur has been found, the parameters describing the shape of the basic action threshold curve are first defined according to the gear entered by the protection:

1) If the protection enters gear 0, the fixed value at point t _start +2 is set to 4 p.u., the fixed value at point t _start +3 is set to 4.5 pu, and the fixed value from point t _start +4 to point t _start +12 is set to 90 p.u.;

2) If the protection enters gear position 1, the fixed value at point t _start +2 is set to 4 p.u., the fixed value at point t _start +3 is set to 4.5 pu, the fixed value at point t _start +4 is set to 5 p.u., and the fixed values from point t _start +6 to point t _start +12 are set to 90 p.u.

The present invention also proposes a peak braking method, defining the three-phase peak braking action threshold increment function as: Define the total peak braking action threshold increment function S _threshold (t). Under the condition that the protection start point t _start has been determined and the current integration start time t _Cur has been found, starting from time t _Cur , the value of the total peak braking action threshold increment function of each sampling point is determined according to formula (18):

Among them, _Scoe is the peak braking coefficient, which is used to adjust the sensitivity of the protection method. The peak braking coefficient _Scoe is determined by multiple steps:

1) Basic braking coefficient definition steps

When the protection start point t _start has been determined, if the protection enters the gear 0 through the current integration start time judgment method, then go to step 2); otherwise S _coe =1.5.

2) Steps for zero-sequence quantity reduction braking coefficient

When the protection start point t _start has been determined and the protection enters gear position 0, it is determined whether the protection start point satisfies the mathematical relationship described in formula (19):

If the protection starting point t _start satisfies both the first and second equations in equation (19), then S _coe = 0.6; otherwise, S _coe = 1.2.

The present invention also proposes a ratio braking method to ensure the reliability of the protection method so that it can reliably not operate in the event of an out-of-zone fault. The ratio braking amount is determined according to formula (20):

Where k _BK is the ratio braking coefficient. When the protection start point t _start has been determined, only when the absolute value integral of the three-phase current change amount shown in formula (17) The corresponding phase protection device is allowed to operate only when they are respectively greater than _BA , _BB , and _BC defined in formula (20).

Figure 1 is a schematic diagram of a transformer fault simulation model, Figure 2 is a protection start logic block diagram, and Figure 3 is an action logic block diagram. In conjunction with Figures 1 to 3, the protection method of the present invention determines whether to act according to the following steps:

1) For the current sampling point t, determine whether the protection is started by the protection start time judgment method; if the protection is started, the current sampling point is used as the protection start point t _start ; then determine the protection judgment result category by the voltage integration start time judgment method, and only when the judgment result category is a fault category, enter the current integration start time judgment step, otherwise directly lock the protection;

2) Determine the gear position entered by the protection through the current integration starting time judgment method, and determine the current integration starting time t _Cur ; determine the basic action threshold curve parameters and peak braking coefficient according to the gear position entered by the protection.

3) From the voltage integration start time t _Vol to the 12th sampling point after the protection start point, obtain the absolute value integral of the three-phase current change; through method (3) and method (4), determine the basic action threshold curve K _threshold and the total peak braking increment curve S _threshold respectively;

4) Only when any sampling point after the start time of current integration (inclusive) completely satisfies equation (21):

Then the action export is allowed. Represents each phase.

The present invention uses the transformer fault simulation model shown in FIG1 to carry out internal and external fault simulation verification.

(1) The transformer fault simulation model is used to carry out simulation verification of severe faults in phase A in the area. The voltage and current integration start times are shown in Figure 4, the current change integral criterion and floating threshold curve are shown in Figure 5, the basic action threshold curve and the ratio peak braking increment curve are shown in Figure 6, and the ratio braking result is shown in Figure 7. It can be seen that the protection method of the present invention can act correctly, sensitively and quickly in this fault scenario, and the action time is within 2.5ms.

(2) The transformer fault simulation model is used to carry out the simulation verification of the A-phase high-resistance fault in the area. The voltage and current integration start time obtained are shown in Figure 8, the current change integral criterion and the floating threshold curve are shown in Figure 9, the basic action threshold curve and the ratio peak braking increment curve are shown in Figure 10, and the ratio braking result is shown in Figure 11. It can be seen that the protection method of the present invention can act correctly, sensitively and quickly in this fault scenario, and the action time is within 2ms.

(3) The transformer fault simulation model is used to carry out the simulation verification of the A-phase grounding fault outside the zone, and the voltage and current integration start times are shown in Figure 12. It can be seen that the protection method of the present invention can reliably not act in this fault scenario, and the current integration start time method cannot find a sampling point that meets the conditions, and the protection is directly locked.

(4) The A-phase empty-charging inrush current simulation verification is carried out using the transformer fault simulation model, and the voltage and current integration start time obtained are shown in Figure 13. It can be seen that in this scenario, due to the large voltage and current point difference, the voltage start criterion at one point after the protection start point cannot be met, and the protection is reliably locked and the capture action is achieved.

In summary, the present invention determines whether the protection is activated for the current sampling point through rules; if activated, the current sampling point is used as the protection start point, and the protection judgment result category is determined through rules. Only when the judgment result category is a fault category, the next step is entered, otherwise the protection is directly locked; the gear entered by the protection is determined through rules, and the current integration start time is determined; the basic action threshold curve parameters and peak braking coefficient are determined according to the gear entered by the protection; from the start time of voltage integration to the 12th sampling point after the protection start point, the absolute value integral of the three-phase current change is obtained; the basic action threshold curve and the total peak braking increment curve are determined respectively; only when any sampling point after the current integration start time fully meets the preset requirements, the sampling point is allowed to operate the exit. The present invention can realize the action within 2ms under severe transformer faults, and reliably not act in occasions such as inrush current, CT disconnection, and out-of-zone faults, with superior performance, thereby significantly improving the reliability of the safe and stable operation of the transformer.

Exemplary Devices

The present invention also provides a transformer quick-break protection device based on the starting time difference of electrical quantity mutation, comprising:

A first judgment module is used to judge whether the protection is started according to a predetermined protection start time judgment rule for the current sampling point t;

The second judgment module is used to, if the protection is started, take the current sampling point as the protection start point t _start , and then determine the protection judgment result category according to the predetermined voltage integration start time judgment rule, and only when the judgment result category is a fault category, enter the current integration start time judgment step, otherwise directly lock the protection;

The third judgment module is used to determine the gear entered by the protection through a predetermined current integration start time judgment rule, and determine the current integration start time t _Cur ; determine the basic action threshold curve parameters and the peak braking coefficient according to the gear entered by the protection;

The determination module is used to obtain the absolute value integral of the three-phase current change from the voltage integration start time t _Vol to the 12th sampling point after the protection start point; determine the basic action threshold curve K _threshold (t) and the total peak braking increment curve S _threshold (t) respectively by a preset method;

Action module, used only when any sampling point after the current integration start moment completely satisfies When , the sampling point is allowed to act as an export: In the formula, /> is the absolute value integral of the three-phase current change, /> represents each phase, K _threshold (t) is the basic action threshold curve, S _threshold (t) is the total peak braking increment curve, /> is the three-phase ratio braking amount.

The transformer quick-trip protection device based on the starting time difference of electrical quantity mutation in an embodiment of the present invention corresponds to the transformer quick-trip protection method based on the starting time difference of electrical quantity mutation in another embodiment of the present invention, which will not be repeated here.

Exemplary Electronic Devices

FIG14 is a structure of an electronic device provided by an exemplary embodiment of the present invention. As shown in FIG14 , the electronic device 140 includes one or more processors 141 and a memory 142 .

The processor 141 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

The memory 142 may include one or more computer program products, which 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), etc. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 141 may run the program instructions to implement the method for information mining of historical change records and/or other desired functions of the software program of each embodiment of the present invention described above. In one example, the electronic device may also include: an input device 143 and an output device 144, which are interconnected via 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, etc.

The output device 144 can output various information to the outside, and can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

Of course, for simplicity, only some of the components related to the present invention in the electronic device are shown in Fig. 14, omitting components such as a bus, an input/output interface, etc. In addition, the electronic device may further include any other appropriate components according to specific application scenarios.

Exemplary computer program products and computer-readable storage media

In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

The computer program product may be written in any combination of one or more programming languages to write program code for performing the operations of the embodiments of the present invention, including object-oriented programming languages such as Java, C++, etc., and conventional procedural programming languages such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enables the processor to execute the steps of the method for information mining of historical change records according to various embodiments of the present invention described in the above “Exemplary Method” section of this specification.

The computer readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, a system, system or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

The block diagrams of the devices, systems, equipment, and systems involved in the present invention are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and/or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The word "such as" used here refers to the phrase "such as but not limited to", and can be used interchangeably with it.

The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware or any combination of software, hardware, firmware. The above order of steps for the method is only for illustration, and the steps of the method of the present invention are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method 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 should also be noted that in the system, device and method of the present invention, each component or each step can be decomposed and/or recombined. These decompositions and/or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in the field to make or use the present invention. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but in accordance with the widest range consistent with the principles and novel features disclosed here.

The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations 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、i_B、i_C 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)＝(i_A(t)+i_B(t)+i_C(t))/3 (6)

and defining a high-voltage side zero sequence current maximum value i _0MAX according to the formula (7):

i_0MAX(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、u_B、u_C; 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,i_b,i_c, 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.