A TV disconnection discrimination method, system and storage medium for the factory branch composite voltage overcurrent

Abstract

The present invention discloses a method, a system and a storage medium for discriminating TV disconnection of factory branch complex overcurrent. The method includes the following steps: 1) When the protection operates normally, the TV disconnection operates normally, and the TV disconnection is judged as "no", and the protection export is not blocked; 2) When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "no", the protection export is not blocked, and at the same time, the main protection criterion is satisfied, and the protection reliably operates and exports; 3) When the protection operates normally and turns to a TV three-phase disconnection, the TV disconnection is judged as "yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction. The method of the present invention can effectively solve the deficiencies of the existing solutions that cannot take into account the anti-misoperation of the protection device during the starting overcurrent of the factory branch motor and the reliable operation of the protection device during the three-phase short-circuit fault.

Description

Technical Field

[0001] The present invention relates to a method for adaptively discriminating TV disconnection in factory branch composite voltage overcurrent, belonging to the field of relay protection in power systems. Background Art

[0002] When a short circuit occurs in a transformer or an element adjacent to the transformer, if the main protection or the corresponding circuit breaker fails to operate due to reasons, the backup protection will act. Generally, strict selective coordination requirements are imposed on the backup protection. As the backup protection for the phase-to-phase faults of the factory branch busbar and adjacent elements, the factory branch composite voltage overcurrent protection not only needs to consider the protection coordination with the short circuit faults of the factory branch busbar and adjacent elements, but also needs to consider the influence of the large current during the self-starting of the self-starting motor in the factory branch on the protection. The traditional protection logic block diagram is as Figure 1 shown, including:

[0003] (1) Overcurrent setting value I g

[0004] The current is taken from the current transformer of the factory transformer branch, and its operating current I g should be set according to the rated current of the transformer during normal operation, that is

[0005] I g =K rel I e / 0.95

[0006] In the formula: K rel —— Reliability coefficient;

[0007] I e —— Transformer rated current, secondary value of TA.

[0008] (2) Low voltage setting value U l

[0009] The voltage is taken from the factory branch busbar voltage, and its low voltage setting value U l , is set according to the lowest voltage that appears during the start-up of the motors on the factory branch busbar on the low voltage side of the high-voltage factory transformer. Usually

[0010] U l =(0.55~0.6)U e , U e —— Transformer rated voltage, secondary value of TV (voltage transformer).

[0011] (3) Negative sequence voltage operating value U 2g

[0012] The voltage is taken from the factory branch busbar voltage, and the negative sequence voltage operating value U 2gThe setting principle is: avoid the maximum negative-sequence voltage of the transformer during normal operation. The negative-sequence voltage value can be determined by actual measurement. If there is no actual measurement value, the negative-sequence voltage operating value U 2g takes 6.0% - 8.0% of the rated voltage of the transformer.

[0013] The current is taken from the current transformer of the plant transformer branch. Its operating current I g is set according to avoiding the rated current of the transformer during normal operation. When the secondary circuit of the branch voltage transformer is disconnected, for asymmetric disconnection, that is, one-phase or two-phase TV disconnection, the negative-sequence voltage criterion is satisfied; for symmetric disconnection, that is, three-phase TV disconnection, the low-voltage criterion is satisfied, and the protection is blocked by the over-current criterion. However, on-site, there are often cases where the TV disconnection is not processed in a short time, and then when the motors on the branch bus start self-starting, the self-starting current of the motors is very large, generally far exceeding the branch rated current, and the over-current criterion is satisfied, resulting in misoperation of the protection.

[0014] In view of the above deficiencies of the traditional complex-voltage over-current protection for the plant use branch, currently, the protection logic block diagrams as Figure 2 and Figure 3 shown are generally adopted, which is Scheme 2:

[0015] The suggestions for setting the protection settings in Scheme 2 are the same as those in Scheme 1. The settings for TV disconnection are:

[0016] (1) The negative-sequence voltage setting value U 2.ptop :

[0017] It is set according to avoiding the maximum negative-sequence voltage of the transformer during normal operation. The setting value is built-in. When the input voltage is phase voltage, the setting value is 5.74V; when the input voltage is line voltage, the setting value is 10V;

[0018] (2) The negative-sequence current setting value I 2.ptop :

[0019] It is set according to avoiding the maximum unbalanced current of the transformer during normal operation. The setting value is built-in and takes 0.1I N , I N is the secondary rated value of the TA;

[0020] (3) The low-voltage setting value U ptop :

[0021] It is set according to avoiding the lowest voltage that appears in the transformer during normal operation. The setting value is built-in and takes 30V;

[0022] (4) The current setting values I ptopL 、I ptopH :

[0023] I ptopL : It is set according to avoiding the zero drift of the channel. The setting value is built-in and takes 0.04IN ;

[0024] I ptopH : (a) It is set according to avoiding the rated current of the transformer during normal operation, that is

[0025] I ptopH =K rel I e

[0026] In the formula: K rel —— Reliability coefficient, taking 1.3 - 1.5;

[0027] I e —— Rated current of the transformer, secondary value of TA;

[0028] (b) It is set according to avoiding the maximum self - starting current of the motors connected to this branch busbar that need to participate in self - starting, that is

[0029] I ptopH =K rel I M

[0030] In the formula: K rel —— Reliability coefficient, taking 1.3 - 1.5;

[0031] I M —— Maximum self - starting current of the motors connected to this branch busbar that need to participate in self - starting.

[0032] Add the TV disconnection criterion to the original protection logic. If the voltage is abnormal and the current is normal, it is judged that the TV is disconnected and the protection is blocked. When the TV has an asymmetric disconnection, different from the asymmetric phase - to - phase fault, there is an unbalanced voltage during the asymmetric TV disconnection, the three - phase load current is normal, and there is no unbalanced current; when the TV has a three - phase disconnection, different from the three - phase short - circuit fault, the three - phase voltage is low during the three - phase TV disconnection, but the three - phase load current is normal. When the motors on the branch busbar start self - starting, it will cause the voltage of the branch busbar to drop and the branch current to increase. There is an overlapping area between this operating condition and the operating condition during the three - phase short - circuit fault. Then, the high - current setting value for judging the TV disconnection is very important.

[0033] (1) If the current I in the TV disconnection ptopH is set according to avoiding the rated current of the branch, generally taking 1.3 - 1.5 times of the rated current of the branch, considering the following operating conditions:

[0034] While a symmetrical disconnection occurs in the secondary circuit of the branch voltage transformer (TV three-phase disconnection), the motors on the branch bus start self-starting. The low-voltage criterion in the overcurrent protection with composite voltage for the auxiliary branch is satisfied, and the overcurrent criterion is satisfied (at the instant of starting, it is close to the three-phase short-circuit fault current and then gradually decays to the load current (the decay period is very long, far exceeding the protection operation time). Considering the decay amplitude during the protection operation time, the maximum self-starting current may reach 2 - 4 times the branch rated current, which is greater than I ptopH ). At this time, the low-voltage criterion in the TV disconnection logic is satisfied, but the current criterion is not satisfied. The TV disconnection is judged as "no", and the protection will not be blocked, resulting in misoperation of the overcurrent protection with composite voltage for the branch.

[0035] (2) If the current I in the TV disconnection ptopH is set according to the maximum self-starting current of the motors that need to participate in self-starting connected to this branch bus, generally taking 1.3 - 1.5 times the maximum self-starting current of the motors that need to participate in self-starting connected to this branch bus, which is approximately 3 - 6 times the branch rated current. Consider the following operating conditions:

[0036] When a three-phase short-circuit fault occurs in the branch bus or adjacent components, the low-voltage criterion in the overcurrent protection with composite voltage for the auxiliary branch is satisfied, the overcurrent criterion is satisfied, and at the same time, the low-voltage criterion in the TV disconnection logic is satisfied. If the three-phase fault current is less than the current setting value I ptopH , then the current criterion in the TV disconnection is also satisfied, and the TV disconnection is misjudged as "yes", wrongly blocking the outlet of the overcurrent protection with composite voltage for the branch, resulting in protection refusal to operate.

[0037] From the actual situation of on-site operation, there are cases where maintenance is not carried out immediately after TV disconnection. Then, after the TV disconnection alarm, the unit and the unit protection will continue to operate. The overcurrent protection with composite voltage for the auxiliary branch needs to add TV disconnection. However, the existing overcurrent protection with composite voltage for the auxiliary branch with TV disconnection also has the defect that the current setting value in the TV disconnection judgment logic is fixed. If the current I in the TV disconnection ptopH is set according to the branch rated current to avoid it, the protection may misoperate when the TV three-phase disconnection occurs and the motors on the branch bus start self-starting, affecting the protection reliability; the current I in the TV disconnection ptopH is set according to the maximum self-starting current of the motors that need to participate in self-starting connected to this branch bus. Because there is an overlapping area between I ptopH and the three-phase short-circuit fault current (that is, the three-phase short-circuit fault current may be less than the setting value I ptopH ), the protection may refuse to operate when a three-phase short-circuit fault occurs in the branch bus or adjacent components, affecting the protection sensitivity and reliability. Summary of the Invention

[0038] The technical problem to be solved by the present invention: In the factory branch composite voltage overcurrent protection, in the existing TV disconnection judgment logic, the current setting value is fixed. If the setting value is too low, the protection device may malfunction, affecting the reliability of the protection device; if the setting value is too high, the protection device may refuse to operate, affecting the protection sensitivity.

[0039] To solve the above technical problems, the present invention adopts the following technical solutions:

[0040] A method for judging TV disconnection in factory branch composite voltage overcurrent, comprising the following steps:

[0041] 1) When the protection is operating normally, the TV disconnection is operating normally, and the TV disconnection is judged as "no", without blocking the protection export. At this time:

[0042] Unbalanced voltage: U2 < U 2.ptop , the negative sequence voltage criterion is not satisfied;

[0043] Unbalanced current: I2 ≤ I 2.ptop , no negative sequence current criterion is satisfied;

[0044] Three-phase voltage: U ab > U ptop , U ca > U ptop , the low voltage criterion is not satisfied;

[0045] Three-phase current: I protL ≤ I 相 ≤ (K1I protH1 + K2I protH2 ), the initial value of TV disconnection judgment is no, K1 is 1, K2 is 0, and I protL ≤ I 相 ≤ I protH1 , the normal phase current criterion is satisfied;

[0046] Among them,

[0047] U2 is the calculated value of the negative sequence voltage of the branch bus voltage; I2 is the calculated value of the negative sequence current of the branch current;

[0048] U 线 is the line voltage of the branch bus; I 相 is the branch phase current I a , I b , I c ;

[0049] U 2.ptop is the negative sequence voltage setting value for judging TV asymmetry disconnection (one-phase or two-phase disconnection) in the TV disconnection criterion;

[0050] I 2.ptopIt is the negative sequence current setting value for judging the asymmetric disconnection of TV (one-phase or two-phase disconnection) in the TV disconnection criterion;

[0051] U ptop It is the low voltage setting value for judging the symmetric disconnection of TV (three-phase disconnection) in the TV disconnection criterion;

[0052] K1 is the no-TV-disconnection state value, and K2 is the yes-TV-disconnection state value;

[0053] Lower limit value I ptopL and the low current threshold value I ptopH1 , the high current threshold value I ptopH2 are all current setting values for judging the symmetric disconnection of TV (three-phase disconnection) in the TV disconnection criterion;

[0054] Lower limit value I ptopL Judges whether the branch three-phase current is loaded. When the branch is open or the branch is unloaded, the lower limit value current criterion does not work;

[0055] The low current threshold value I of the upper limit value ptopH1 , the high current threshold value I of the upper limit value ptopH2 Judge whether the three-phase current conforms to the load current characteristics under non-fault conditions. The low current threshold value I ptopH1 Judges the normal load current condition, and the high current threshold value I ptopH2 Judges the motor starting current condition.

[0056] Lower limit value I ptopL Generally set according to avoiding the zero drift of the channel;

[0057] Low current threshold value I ptopH1 Is set according to avoiding the rated current of the transformer during normal operation;

[0058] 2) When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "no", the protection export is not blocked, and at the same time the main protection criterion is met, and the protection reliably operates and exports;

[0059] 3) When the protection operates normally and turns to a three-phase TV disconnection, the TV disconnection is judged as "yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

[0060] Furthermore, it also includes:

[0061] 4) When the TV disconnection is processed and the protection operation returns to normal, at this time the TV disconnection is judged as "no", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the phase current abnormal criterion threshold becomes: I protL ≤I 相 ≤I protH1 .

[0062] A TV disconnection discrimination system for the complex overcurrent of the auxiliary power branch includes the following functional modules:

[0063] Normal operation module: When the protection operates normally, the TV disconnection operates normally, and the TV disconnection is judged as "No", and the protection export is not blocked. At this time:

[0064] Unbalanced voltage: U2 < U 2.ptop , and the negative sequence voltage criterion is not satisfied;

[0065] Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied;

[0066] Three-phase voltage: U ab > U ptop , U ca > U ptop , and the low voltage criterion is not satisfied;

[0067] Three-phase current: I protL ≤ I 相 ≤ (K1I protH1 + K2I protH2 ), the initial value of the TV disconnection judgment is No, K1 is 1, K2 is 0, and when I protL ≤ I 相 ≤ I protH1 , the normal phase current criterion is satisfied;

[0068] Among them,

[0069] U2 is the calculated value of the negative sequence voltage of the branch bus voltage; I2 is the calculated value of the negative sequence current of the branch current;

[0070] U 线 is the line voltage of the branch bus; I 相 is the branch phase current I a , I b , I c ;

[0071] U 2.ptop is the negative sequence voltage setting value for judging the asymmetrical disconnection (one-phase or two-phase disconnection) of the TV in the TV disconnection criterion;

[0072] I 2.ptop is the negative sequence current setting value for judging the asymmetrical disconnection (one-phase or two-phase disconnection) of the TV in the TV disconnection criterion;

[0073] U ptop is the low voltage setting value for judging the symmetrical disconnection (three-phase disconnection) of the TV in the TV disconnection criterion;

[0074] K1 is the No state value of the TV disconnection, and K2 is the Yes state value of the TV disconnection;

[0075] Lower limit value I ptopL And the low current threshold value I ptopH1 、The high current threshold value I ptopH2 Are both the current setting values for judging the TV symmetry disconnection (three-phase disconnection) in the TV disconnection criterion;

[0076] Lower limit value I ptopL Judge whether the three-phase current of the branch is loaded. When the branch is open or the branch is unloaded, the lower limit current criterion does not work;

[0077] The low current threshold value I of the upper limit value ptopH1 、The high current threshold value I of the upper limit value ptopH2 Judge whether the three-phase current conforms to the load current characteristics under non-fault conditions. The low current threshold value I ptopH1 Judge the normal load current condition, and the high current threshold value I ptopH2 Judge the motor starting current condition.

[0078] Lower limit value I ptopL Generally set according to avoiding the zero drift of the channel;

[0079] Low current threshold value I ptopH1 Set according to avoiding the rated current of the transformer during normal operation;

[0080] Three-phase short-circuit fault module: When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "no", the protection export is not blocked, and at the same time the main protection criterion is met, and the protection reliably operates and exports;

[0081] Three-phase TV disconnection module: When the protection operates normally and turns to a three-phase TV disconnection, the TV disconnection is judged as "yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

[0082] Furthermore, it further includes:

[0083] Recovery module: When the TV disconnection is processed and the protection operation returns to normal, at this time the TV disconnection is judged as "no", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the phase current abnormality criterion threshold becomes: I protL ≤I 相 ≤I protH1 .

[0084] A computer-readable storage medium for storing the TV disconnection discrimination method of the plant branch composite voltage overcurrent described in any one of claims 1-8.

[0085] Advantages achieved by the present invention: The method for discriminating TV disconnection in the factory branch composite voltage overcurrent provided by the present invention can effectively improve the reliability and sensitivity of the protection action under two different working conditions, namely, the starting overcurrent of the factory branch motor and the three-phase short-circuit fault, by identifying the TV disconnection working condition and automatically adjusting the threshold of the TV disconnection discrimination criterion. When the protection is in the normal operation state and the TV operates normally, the phase current abnormal discrimination criterion for the protection to judge TV disconnection is a low threshold. At this time, if an interphase fault occurs between the factory branch and adjacent components, especially a three-phase short-circuit fault, the lower the threshold of the phase current abnormal discrimination criterion for judging TV disconnection, the less likely it is to be misjudged as TV disconnection, and then the protection is misblocked, thus fully ensuring that the protection device can act reliably; when the TV is disconnected during the normal operation state of the protection, after the protection judges the TV disconnection, the phase current abnormal discrimination criterion for judging TV disconnection automatically changes from a low threshold to a high threshold. Even if the TV disconnection is not processed immediately for a short time, during this process, when the branch motor starts and the branch current increases, but the current is less than the high current threshold for the phase current abnormal discrimination of TV disconnection, the TV disconnection is not lifted, and the protection export is still reliably blocked, ensuring that the protection device does not malfunction. The method of the present invention can effectively solve the deficiency of the existing scheme that cannot take into account the anti-misoperation of the protection device during the starting overcurrent of the factory branch motor and the reliable action of the protection device during the three-phase short-circuit fault. Description of the Drawings

[0086] Figure 1 is the logic block diagram of the factory branch composite voltage overcurrent protection of the existing scheme one;

[0087] Figure 2 is the logic block diagram of the factory branch composite voltage overcurrent protection of the existing scheme two;

[0088] Figure 3 is the TV disconnection logic block diagram of the existing scheme two;

[0089] Figure 4 is the adaptive TV disconnection logic block diagram of the present invention;

[0090] Figure 5 is the TV disconnection program flow chart of the present invention;

[0091] Figure 6 is the schematic diagram of the protection action area of the three schemes under the three-phase short-circuit fault working condition;

[0092] Figure 7 is the schematic diagram of the protection action area of the three schemes under the three-phase short-circuit fault working condition;

[0093] Figure 8 is the schematic diagram of the protection action area of the three schemes under the three-phase TV disconnection + motor self-starting working condition;

[0094] Figure 9Schematic diagram of the protection action areas of three schemes under the condition of three-phase TV disconnection + motor self-starting

[0095] Figure 10 Schematic diagram of the action area with inconsistent initial setting values of TV disconnection Specific implementation mode

[0096] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0097] Figure 4 Adaptive TV disconnection logic block diagram Figure 5 TV disconnection program flow chart in the present invention

[0098] The present invention proposes a method for discriminating TV disconnection of factory branch composite voltage overcurrent. The working principle is to adopt a floating threshold for judging abnormal phase current in the TV disconnection criterion, that is, two state values K1 and K2 of TV disconnection and two current threshold values I ptopH1 、I ptopH2 are introduced, and I protL ≤ I 相 ≤ (K1I protH1 + K2I protH2 );

[0099] K1 is the "no" state value of TV disconnection, and K2 is the "yes" state value of TV disconnection. When the TV disconnection is judged as "no", K1 is 1 and K2 is 0; when the TV disconnection is judged as "yes", K2 is 1 and K1 is 0;

[0100] The low current threshold value I ptopH1 is set according to avoiding the branch rated current, and the high current threshold value I ptopH2 is set according to avoiding the maximum self-starting current of the motors that need to participate in self-starting connected to the bus of this branch;

[0101] According to the state of TV disconnection, the no state value K1 and the yes state value K2 automatically adjust the threshold for judging abnormal phase current in the TV disconnection criterion, that is, when the TV disconnection is judged as "no", the threshold for judging abnormal phase current of TV disconnection is the low current threshold value I ptopH1 ; when the TV disconnection is judged as "yes", the threshold for judging abnormal phase current of TV disconnection is the high current threshold value I ptopH2 , so as to ensure that the protection has higher adaptability under different working conditions and takes into account the reliability and sensitivity of the protection.

[0102] Embodiment 1

[0103] A method for discriminating TV disconnection of factory branch composite voltage overcurrent includes the following steps:

[0104] 1) When the protection operates normally, the TV disconnection operates normally, the TV disconnection is judged as "no", and the protection export is not blocked;

[0105] At this time, the electrical quantity characteristics are that the voltage is normal, that is, the three-phase voltage is balanced and operates at the rated voltage value; the current is normal, that is, the three-phase current is balanced and operates at the load current value, where:

[0106] Unbalanced voltage: U2 < U 2.ptop , and the negative sequence voltage criterion is not satisfied;

[0107] Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied;

[0108] Three-phase voltage: U ab > U ptop , U ca > U ptop , and the low voltage criterion is not satisfied;

[0109] Three-phase current: I protL ≤ I 相 ≤ (K1I protH1 + K2I protH2 ), the initial value of the TV disconnection judgment is NO, the NO state value K1 is 1, the YES state value K2 is 0, and when I protL ≤ I 相 ≤ I protH1 , the normal phase current criterion is satisfied;

[0110] Among them,

[0111] U2 is the calculated value of the negative sequence voltage of the branch bus voltage; I2 is the calculated value of the negative sequence current of the branch current;

[0112] U ab , U bc are the line voltages of the branch bus; I 相 is the branch phase current I a , I b , I c ;

[0113] U 2.ptop is the negative sequence voltage setting value for judging the asymmetric disconnection (one-phase or two-phase disconnection) of the TV in the TV disconnection criterion;

[0114] I 2.ptop is the negative sequence current setting value for judging the asymmetric disconnection (one-phase or two-phase disconnection) of the TV in the TV disconnection criterion;

[0115] U ptop is the low voltage setting value for judging the symmetric disconnection (three-phase disconnection) of the TV in the TV disconnection criterion;

[0116] K1 is the NO state value of the TV disconnection, and K2 is the YES state value of the TV disconnection;

[0117] Lower limit value I ptopL It is the current setting value for judging the symmetrical disconnection (three-phase disconnection) of TV in the TV disconnection criterion. Generally, it is set by avoiding the zero drift of the channel, and the setting value is built-in, taking 0.04I N , to judge whether the branch is loaded;

[0118] Low current threshold value I ptopH1 and high current threshold value I ptopH2 They are the current setting values for judging the symmetrical disconnection (three-phase disconnection) of TV in the TV disconnection criterion, and judge whether the branch current operates within the normal load current range.

[0119] Low current threshold value I ptopH1 It is set by avoiding the rated current of the transformer during normal operation, and can take 1.3 - 1.5 times the rated current of the branch;

[0120] High current threshold value I ptopH2 It is set by avoiding the maximum self-starting current of the motors that need to participate in self-starting connected to the bus of this branch, and can take 1.3 - 1.5 times the maximum self-starting current of the motors that need to participate in self-starting connected to the bus of this branch;

[0121] 2) When the protection operates normally and changes to a three-phase short-circuit fault, the TV disconnection is judged as "No", the protection export is not blocked, and at the same time, the main protection criterion is satisfied, and the protection reliably operates and exports;

[0122] The electrical quantity characteristics at this time are that the three-phase voltage is low, the three-phase current is large, and there is no negative-sequence voltage and negative-sequence current;

[0123] Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not satisfied;

[0124] Unbalanced current: I2 ≤ I 2.ptop , no negative-sequence current criterion is satisfied;

[0125] Three-phase voltage: U ab ≤ U ptop , U ca ≤ U ptop , the low-voltage criterion is satisfied;

[0126] Three-phase current: I 相 > I protH1 , the three-phase short-circuit fault current on the auxiliary power branch bus reaches 5 - 10 times the rated current of the branch. When a three-phase short-circuit fault occurs in the adjacent components of the auxiliary power branch bus, considering factors such as connection impedance and non-metallic short circuit, the three-phase fault current is less than the three-phase short-circuit fault current on the auxiliary power branch bus, which is 3 - 8 times the rated current of the branch; and the low current threshold value I ptopH1Set the relay according to the rated current of the bypass branch, generally taking 1.3 - 1.5 times the rated current of the branch. When the three-phase fault current is greater than the low current threshold I ptopH1 , the abnormal phase current criterion for TV disconnection is not met, and the TV disconnection is judged as "No", the protection is not blocked, and the overcurrent protection with composite voltage of the branch operates reliably.

[0127] 3) When the protection is operating normally and then TV three-phase disconnection occurs, the TV disconnection is judged as "Yes", the protection export is blocked by TV disconnection, and the protection does not operate incorrectly.

[0128] At this time, the electrical quantity characteristics are low three-phase voltages, normal phase currents, no negative sequence voltage and negative sequence current;

[0129] Unbalanced voltage: U2 < U 2.ptop , the negative sequence voltage criterion is not met;

[0130] Unbalanced current: I2 ≤ I 2.ptop , no negative sequence current criterion is met;

[0131] Three-phase voltages: U ab ≤ U ptop , U ca ≤ U ptop , the low voltage criterion is met;

[0132] The three-phase currents are normal, I protL ≤ I 相 ≤ I protH1 , the normal phase current criterion is met;

[0133] At this time, the TV disconnection is judged as "Yes", K1 is 0, K2 is 1, so the threshold of the abnormal phase current criterion changes and increases to I protL ≤ I 相 ≤ I protH2 , and the protection export is blocked by TV disconnection.

[0134] 4) When the TV disconnection is repaired and the protection operation returns to normal, the electrical quantity characteristics at this time are the same as in step 1). The TV disconnection is judged as "No", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the threshold of the abnormal phase current criterion changes to: I protL ≤ I 相 ≤ I protH1 .

[0135] Embodiment 2

[0136] A method for discriminating TV disconnection of overcurrent protection with composite voltage for auxiliary power branch, comprising the following steps:

[0137] 1) When the protection is operating normally, the TV disconnection is operating normally, and the TV disconnection is judged as "No", and the protection export is not blocked;

[0138] 2) When the protection is operating normally and a three-phase short-circuit fault occurs, the TV disconnection is judged as "No", the protection export is not blocked, and at the same time, the main protection criterion is met, and the protection reliably operates and exports;

[0139] 3) When the protection is operating normally and a three-phase disconnection of the TV occurs, the TV disconnection is judged as "Yes", and the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

[0140] If a three-phase disconnection occurs in the TV on the branch bus, and the site does not stop the machine for processing within the set short time, during this process, the self-starting motors on the branch of this bus self-start, and the electrical quantity characteristics are low three-phase voltage, increased phase current, no negative-sequence voltage and negative-sequence current.

[0141] Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not met;

[0142] Unbalanced current: I2 ≤ I 2.ptop , no negative-sequence current criterion is met;

[0143] Low three-phase voltage, U ab ≤ U ptop , U ca ≤ U ptop , the low-voltage criterion is met;

[0144] The three-phase current increases. The maximum self-starting current of the motors on the plant-use branch bus is close to the three-phase short-circuit fault current at the moment of starting, and then gradually decays to the load current. The decay period is very long, far exceeding the protection operation time. Considering the decay amplitude of the protection operation time, the maximum self-starting current may reach 2-4 times the branch rated current; while the high-current threshold I ptopH2 is set according to the maximum self-starting current of the motors that need to participate in self-starting connected to this branch bus, generally taking 1.3-1.5 times the maximum self-starting current of the motors that need to participate in self-starting connected to this branch bus. The three-phase current increases due to the self-starting current of the motors, but is less than the high-current threshold I ptopH2 , the phase current abnormal criterion for the protection to judge TV disconnection is not met, and the TV disconnection continues to be judged as "Yes", blocking the protection export.

[0145] Figure 6 It is a schematic diagram of the protection operation area of three schemes under the three-phase short-circuit fault condition. In Figure 6 , the schematic diagrams of the protection operation area under different working conditions are used to illustrate the differences of the three schemes, among which there are two fixed-value setting methods for Scheme II, which are decomposed into Scheme II(a) and Scheme II(b).

[0146] Working condition 1: Three-phase short circuit within the protected object

[0147] For a three-phase short circuit within the protected object, the protection device should reliably and sensitively operate.

[0148] Scheme 2 is set according to avoiding the rated current of the transformer during normal operation;

[0149] Scheme Serial Number Action Area Comparison Remarks Scheme One A, B, C High protection sensitivity Scheme Two (a) A, B, C High protection sensitivity Scheme Three A, B, C High protection sensitivity

[0150] Figure 7 It is a schematic diagram of the protection action area of the three schemes under the three-phase short-circuit fault condition. Scheme 2 is set according to avoiding the maximum self-starting current of the motors that need to participate in self-starting and are connected to the busbar of this branch.

[0151] Scheme Serial Number Action Area Comparison Remarks Scheme One A, B, C High protection sensitivity Scheme Two (b) A, C Low protection sensitivity Area B is misjudged as TV disconnection and the protection is blocked Scheme Three A, B, C High protection sensitivity

[0152] Motor self-starting during the period when the three-phase disconnection of TV is not processed

[0153] During the period when the three-phase disconnection of TV is not processed and the motor self-starts, the protection should be reliably blocked. Only when the current is very large, greater than I ptopH , it is judged that a three-phase short-circuit fault occurs simultaneously with the disconnection of TV, that is, it enters Area C, and the disconnection lock of TV should be opened.

[0154] Figure 8 It is a schematic diagram of the protection action area of the three schemes under the condition of three-phase disconnection of TV + motor self-starting. Scheme 2 is set according to avoiding the rated current of the transformer during normal operation.

[0155]

[0156]

[0157] Figure 9 It is a schematic diagram of the protection action area of the three schemes under the condition of three-phase disconnection of TV + motor self-starting. Scheme 2 is set according to avoiding the maximum self-starting current of the motors that need to participate in self-starting and are connected to the busbar of this branch.

[0158] Scheme Serial Number Action Area Comparison Remarks Scheme One A, B, C The protection malfunctions in Area A and Area B Scheme Two (b) C The protection does not malfunction Scheme Three C The protection does not malfunction

[0159] Based on the above analysis:

[0160]

[0161] In the discrimination of TV disconnection, the initial setting values of K1 and K2 are the key. If, in the initial state, the protection operates normally and the discrimination of TV disconnection is "no", K1 is set to 0 and K2 is set to 1, and the phase current abnormal criterion for judging TV disconnection is the high current threshold I ptopH2 ; when the TV disconnection occurs during the normal operation of the protection device, K1 is set to 1 and K2 is set to 0, and the phase current abnormal criterion for judging TV disconnection is the low current threshold I ptopH1 , and the TV disconnection cannot operate reliably. Compared with the original scheme (in the initial state, K1 is set to 1 and K2 is set to 0, and the phase current abnormal criterion for judging TV disconnection is the high current threshold IptopH1 ; When TV disconnection occurs during the normal operation of the protection device, K1 is set to 0 and K2 is set to 1. The phase current abnormal criterion for judging TV disconnection is the low setting value I ptopH2 ) is compared as follows:

[0162] Figure 10 is a schematic diagram of the action area for inconsistent initial setting values of TV disconnection,

[0163]

[0164] The adaptive TV disconnection discrimination method for plant branch composite voltage overcurrent based on TV disconnection state recognition of the present invention discriminates TV disconnection according to the protection and automatically adjusts the current threshold for judging TV disconnection. On the one hand, when the TV disconnection judgment is in the "no" state during the normal operation of the protection, the threshold of the phase current abnormal criterion for judging TV disconnection is the low threshold I ptopH1 , which ensures the sensitivity of three-phase short-circuit faults; on the other hand, during the large current of motor self-starting when TV disconnection is not processed, since the TV disconnection judgment is in the "yes" state, the threshold of the phase current abnormal criterion for judging TV disconnection is the high threshold I ptopH2 , avoiding misoperation of the protection at this time.

[0165] A TV disconnection discrimination system for plant branch composite voltage overcurrent includes the following functional modules:

[0166] Normal operation module: When the protection operates normally, the TV disconnection operates normally, the TV disconnection judgment is "no", and the protection export is not blocked. At this time:

[0167] Unbalanced voltage: U2 < U 2.ptop , and the negative sequence voltage criterion is not satisfied;

[0168] Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied;

[0169] Three-phase voltage: U ab > U ptop , U ca > U ptop , and the low voltage criterion is not satisfied;

[0170] Three-phase current: I protL ≤ I 相 ≤ (K1I protH1 + K2I protH2 ), the initial value of TV disconnection judgment is no, K1 is 1, K2 is 0, and it satisfies I protL ≤ I 相 ≤ I protH1 , and the phase current normal criterion is satisfied;

[0171] Among them,

[0172] U2 is the calculated negative-sequence voltage of the branch bus voltage; I2 is the calculated negative-sequence current of the branch current;

[0173] U 线 is the line voltage of the branch bus; I 相 is the branch phase current I a 、I b 、I c ;

[0174] U 2.ptop is the negative-sequence voltage setting value for judging TV asymmetry disconnection (one-phase or two-phase disconnection) in the TV disconnection criterion;

[0175] I 2.ptop is the negative-sequence current setting value for judging TV asymmetry disconnection (one-phase or two-phase disconnection) in the TV disconnection criterion;

[0176] U ptop is the low-voltage setting value for judging TV symmetry disconnection (three-phase disconnection) in the TV disconnection criterion;

[0177] K1 is the no-TV-disconnection state value, and K2 is the yes-TV-disconnection state value;

[0178] Lower limit value I ptopL and low current threshold value I ptopH1 、high current threshold value I ptopH2 are all current setting values for judging TV symmetry disconnection (three-phase disconnection) in the TV disconnection criterion;

[0179] Lower limit value I ptopL judges whether the branch three-phase current is loaded. When the branch is open or the branch is unloaded, the lower limit current criterion does not work;

[0180] Low current threshold value I of the upper limit value ptopH1 、high current threshold value I of the upper limit value ptopH2 judge whether the three-phase current conforms to the load current characteristics under non-fault conditions. Low current threshold value I ptopH1 judges the normal load current condition, and high current threshold value I ptopH2 judges the motor starting current condition.

[0181] Lower limit value I ptopL is generally set by avoiding the zero drift of the channel;

[0182] Low current threshold value I ptopH1 is set by avoiding the rated current of the transformer during normal operation;

[0183] Three-phase short-circuit fault module: When the protection operates normally and switches to a three-phase short-circuit fault, the TV disconnection is judged as "no", the protection export is not blocked, and at the same time, the main protection criterion is met, and the protection reliably operates and exports;

[0184] Three-phase TV disconnection module: When the protection operates normally and switches to a three-phase TV disconnection, the TV disconnection is judged as "yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

[0185] Furthermore, it also includes:

[0186] Recovery module: When the TV disconnection is processed and the protection operation returns to normal, at this time, the TV disconnection is judged as "no", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the phase current abnormal criterion threshold becomes: I protL ≤I 相 ≤I protH1 .

[0187] A computer-readable storage medium is used to store the above TV disconnection discrimination method or system for the auxiliary branch composite voltage overcurrent.

[0188] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0189] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the processes and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure One one process or multiple processes and / or blocks Figure One one block or multiple blocks.

[0190] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions in Figure One one process or multiple processes and / or blocksFigure One The functions specified in one or more boxes.

[0191] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide for implementing the steps of the functions specified in one Figure One process or more processes and / or boxes Figure One or more boxes.

[0192] The above are only embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention pending approval of the application.

Claims

1. A method for discriminating TV disconnection in the factory branch complex voltage overcurrent, characterized in that, It includes the following steps: 1) When the protection operates normally, the TV disconnection operates normally, the TV disconnection is judged as "No", and the protection export is not blocked; at this time, Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , no negative-sequence current criterion is satisfied; Three-phase voltage: U ab > U ptop , U ca > U ptop , the low-voltage criterion is not satisfied; Three-phase current: I ptopL ≤I 相 ≤(K1I ptopH1 +K2I ptopH2 ), the initial value of TV disconnection judgment is NO, the state value K1 is 1 for NO state, and the state value K2 is 0 for YES state. When I ptopL ≤I 相 ≤I ptopH1 , the normal criterion of phase current is satisfied; Among them, U2 is the calculated value of the negative-sequence voltage of the branch busbar voltage; I2 is the calculated value of the negative-sequence current of the branch current; U ab , U ca are the line voltages of the branch busbar; I 相 is the branch phase current I a , I b , I c ; U 2.ptop is the negative-sequence voltage setting value for judging the asymmetric disconnection of TV in the TV disconnection criterion; I 2.ptop is the negative-sequence current setting value for judging the asymmetric disconnection of TV in the TV disconnection criterion; U ptop is the low-voltage setting value for judging the symmetric disconnection of TV in the TV disconnection criterion; K1 is the no-TV-disconnection state value, and K2 is the yes-TV-disconnection state value; I ptopL is the current setting value for judging the symmetric disconnection of TV in the TV disconnection criterion to determine whether the branch current is loaded; the low-current threshold I ptopH1 and the high-current threshold I ptopH2 are the current setting values for judging the symmetric disconnection of TV in the TV disconnection criterion to determine whether the branch current is operating within the normal load current range; Current setting value I ptopL Set according to avoiding zero drift of the channel; Low current threshold value I ptopH1 It is set according to avoiding the rated current of the transformer during normal operation; High current threshold value I ptopH2 It is set according to avoiding the maximum self-starting current of the motors that need to participate in self-starting and are connected to the busbar of this branch 2) When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "No", the protection export is not blocked, and at the same time the main protection criterion is met, and the protection reliably operates and exports; at this time: Unbalanced voltage: U2 < U 2.ptop , the negative sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied; Three-phase voltage: U ab ≤U ptop ,U ca ≤U ptop , the low-voltage criterion is satisfied; Three-phase current: I 相 > I ptopH1 , the phase current abnormal criterion for TV disconnection is not satisfied; 3) When the protection operates normally and turns to a three-phase TV disconnection, the TV disconnection is judged as "Yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

2. The method for discriminating TV disconnection in the factory branch complex voltage overcurrent according to claim 1, characterized in that: It also includes 4) When the TV disconnection is processed and the protection operation resumes normal, at this time the TV disconnection is judged as "No", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the phase current abnormal criterion threshold becomes: I ptopL ≤I 相 ≤I ptopH1 .

3. The method for discriminating TV disconnection in the factory branch complex voltage overcurrent according to claim 1, characterized in that: For three-phase current, the three-phase short-circuit fault current on the auxiliary power branch bus is 5 to 10 times the branch rated current. When a three-phase short-circuit fault occurs in adjacent components of the auxiliary power branch bus, the three-phase fault current is less than the three-phase short-circuit fault current on the auxiliary power branch bus, and the three-phase fault current is greater than the low current threshold I ptopH1 .

4. The method for discriminating TV disconnection in the factory branch complex voltage overcurrent according to claim 1, characterized in that: In step 3), at this time, Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , no negative-sequence current criterion is satisfied; Three-phase voltage: U ab ≤U ptop ,U ca ≤U ptop , the low-voltage criterion is satisfied; The three-phase current is normal, I ptopL ≤I 相 ≤I ptopH1 , and the normal criterion for phase current is satisfied; At this time, the TV disconnection is judged as "yes", K1 is 0, K2 is 1, and the threshold of the phase current abnormality criterion is I ptopL ≤I 相 ≤I ptopH2 .

5. The method for discriminating TV disconnection in the factory branch complex voltage overcurrent according to claim 1, characterized in that: In step 3), if a three-phase disconnection occurs in the TV on the branch bus, it does not stop the machine for processing within the set time, and the self-starting motor on the corresponding bus branch self-starts. The electrical quantity characteristics are low three-phase voltage, increased phase current, no negative-sequence voltage and negative-sequence current.

6. The method for discriminating TV disconnection in the factory branch complex voltage overcurrent according to claim 5, characterized in that: When a three-phase disconnection occurs in the TV on the branch bus, the self-starting motor on the bus self-starts: Unbalanced voltage: U2 < U 2.ptop , the negative sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied; Three-phase voltage is low, U ab ≤U ptop ,U ca ≤U ptop , the low voltage criterion is met; The three-phase current increases, but is less than the high current threshold value I ptopH2 , the phase current abnormal criterion for the protection to judge TV disconnection is not met, the TV disconnection continues to be judged as "yes", and the protection export is blocked.

7. A TV disconnection discrimination system for the complex overcurrent of the auxiliary power branch, characterized in that It includes the following functional modules: Normal operation module: When the protection operates normally, the TV disconnection operates normally, the TV disconnection is judged as "No", and the protection export is not blocked; at this time, Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , no negative sequence current criterion is satisfied; Three-phase voltage: U ab > U ptop , U ca > U ptop , the low-voltage criterion is not satisfied; Three-phase current: I ptopL ≤I 相 ≤(K1I ptopH1 +K2I ptopH2 ), the initial value of TV disconnection judgment is No, the state value K1 is 1 for No, and the state value K2 is 0 for Yes. When I ptopL ≤I 相 ≤I ptopH1 , the normal criterion of phase current is satisfied; Among them, U2 is the calculated value of the negative-sequence voltage of the branch bus voltage; I2 is the calculated value of the negative-sequence current of the branch current; U ab , U ca are the line voltages of the branch bus; I 相 is the branch phase current I a , I b , I c ; U 2.ptop is the negative-sequence voltage setting value for judging the asymmetric disconnection of TV in the TV disconnection criterion; I 2.ptop is the negative-sequence current setting value for judging the asymmetric disconnection of TV in the TV disconnection criterion; U ptop is the low-voltage setting value for judging the symmetric disconnection of TV in the TV disconnection criterion; K1 is the no-state value of TV disconnection, and K2 is the yes-state value of TV disconnection; I ptopL is the current setting value for judging the symmetric disconnection of TV in the TV disconnection criterion to determine whether the branch current is loaded; the low-current threshold I ptopH1 and the high-current threshold I ptopH2 are the current setting values for judging the symmetric disconnection of TV in the TV disconnection criterion to determine whether the branch current is operating within the normal load current range; Current setting value I ptopL Set according to avoiding zero drift of the channel; Low current threshold value I ptopH1 It is set according to avoiding the rated current of the transformer during normal operation; High current threshold value I ptopH2 It is set according to avoiding the maximum self-starting current of the motors that need to participate in self-starting and are connected to the busbar of this branch Three-phase short-circuit fault module: When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "No", the protection export is not blocked, and at the same time the main protection criterion is met, and the protection reliably operates and exports; at this time: Unbalanced voltage: U2 < U 2.ptop , the negative-sequence voltage criterion is not satisfied; Unbalanced current: I2 ≤ I 2.ptop , and no negative sequence current criterion is satisfied; Three-phase voltage: U ab ≤U ptop ,U ca ≤U ptop ,the low voltage criterion is satisfied; Three-phase current: I 相 > I ptopH1 , the phase current abnormal criterion for TV disconnection is not satisfied; Three-phase TV disconnection module: When the protection operates normally and turns to a three-phase TV disconnection, the TV disconnection is judged as "Yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction.

8. The TV disconnection discrimination system for the complex overcurrent of the auxiliary power branch according to claim 7, characterized in that It also includes: Recovery module: When the TV disconnection is processed and the protection operation resumes normal, at this time the TV disconnection is judged as "No", the protection export is not blocked, K1 is set to 1, K2 is set to 0, and the phase current abnormal criterion threshold is converted to: I ptopL ≤I 相 ≤I ptopH1 .

9. A computer-readable storage medium, characterized in that: Used to store the TV disconnection discrimination method for the factory branch composite voltage overcurrent described in any one of claims 1-6.

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