Voltage alarm method

Abstract

The present invention is a voltage alarm method, which relates to the technology of the power system and is a method that can issue an alarm in a timely manner when the voltage is abnormal. According to the data of the acquisition device, this method automatically calculates the lower limit value of the current operation and the normal voltage value of the voltage operation, and then calculates the low-voltage alarm value, the unbalanced voltage alarm value, and the negative-sequence voltage alarm value based on the real-time voltage. Combining with the current mutation value, it can automatically adapt the voltage and current judgment values according to the acquired information, will not affect the judgment of the current protection under normal operation conditions, and can issue a voltage alarm in case of abnormality, thus improving the protection reliability.

Description

Technical Field

[0001] The present invention relates to the technology of power systems, and particularly to a technology for a voltage alarm method of a collection device. Background Art

[0002] For an ideal high-voltage power system, the voltage is symmetric three-phase, with equal amplitude for each phase voltage and a phase difference of 120 degrees. When the voltage is unbalanced, various situations may occur, such as unequal amplitudes and a phase difference deviating from 120 degrees. When the imbalance reaches a certain degree, the voltage will affect the safe operation of power equipment. At the lightest, it may cause stalling, and at the worst, the equipment may be damaged. At this time, voltage protection is required to decide whether to cut off the power to protect the normal operation of the equipment.

[0003] Power data is usually collected using a power meter collection device. The collected data is based on a power circuit unit and usually collects three-phase information. To calculate the power, the current and voltage of the circuit need to be collected. The current is collected through a current transformer, and the voltage is collected through a voltage transformer. In the collection device, the data collection period is less than 1 millisecond.

[0004] The conventional voltage alarm method of comparing fixed values may give false alarms for normal power outages and miss alarms for asymmetric voltage faults. Summary of the Invention

[0005] Aiming at the defects existing in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a method that can issue an alarm in time when the voltage is abnormal.

[0006] To solve the above technical problem, a voltage alarm method provided by the present invention is characterized in that the specific steps are as follows:

[0007] 1) Obtain the three-phase current values, three-phase voltage values, and overcurrent signals of the nearest N points of the sampling point k from the collection device. Each point includes seven values: the A, B, and C phase voltages, the A, B, and C phase current values, and the overcurrent signal of the point k. Find all the target points M that can simultaneously meet Condition 1, Condition 2, and Condition 3 from the current, voltage values, and overcurrent signals of the N points;

[0008] Condition 1:

[0009] 1.1×Uaver>U(ka)>0.1×Uaver, and 1.1×Uaver>U(kb)>0.1×Uaver, and 1.1×Uaver>U(kc)>0.1×Uaver;

[0010] In the formula, Uaver is the average value of the three-phase voltage acquisition values of the N sampling points in the sampling point sequence S, U(ka) is the A-phase voltage acquisition value of the sampling point k, U(kb) is the B-phase voltage acquisition value of the sampling point k, and U(kc) is the C-phase voltage acquisition value of the sampling point k;

[0011] Condition 2:

[0012] 1.1 × Iaver > I(ka) > 0.1 × Iaver, and 1.1 × Iaver > I(kb) > 0.1 × Iaver, and 1.1 × Iaver > I(kc) > 0.1 × Iaver;

[0013] Wherein, Iaver is the average value of the three - phase current acquisition values of N sampling points in the sampling point sequence S, I(ka) is the A - phase current acquisition value of sampling point k, I(kb) is the B - phase current acquisition value of sampling point k, and I(kc) is the C - phase current acquisition value of sampling point k;

[0014] Condition 3:

[0015] Wherein, Condition 3 is that there is no over - current signal at the k - th point of the power line collected by the power data collection device;

[0016] The collection device is any publicly available power meter collection device applicable to this application.

[0017] 2) When calculating the lower limit value of the current operation when the sampling point belongs to the loop power supply, the calculation method is: sort the current values at point M from small to large, and take out the current value ranked 35% as the lower limit value of the current operation Idz;

[0018] 3) When calculating the normal voltage value of the voltage operation when the sampling point belongs to the loop power supply, the calculation method is: sort the voltage values at point M from small to large, and take out the voltage value ranked 50% as the normal voltage value of the voltage operation Udz;

[0019] 4) At the current k - th moment, the three - phase voltage values and three - phase current values can be obtained, and the initial voltage alarm value Uflag = 0 and the current alarm value Iflag = 1 are set;

[0020] 5) Calculate the low - voltage alarm value as follows:

[0021]

[0022] Wherein, U(k) is the voltage value at the k - th moment, U(k)max is the maximum value of the three - phase voltages collected at the k - th moment, and I(k) is the current value of the phase where the maximum value is located at the k - th moment;

[0023] If Uflag == 1, go to step 9);

[0024] 6) Calculate the unbalanced voltage alarm value as follows:

[0025]

[0026] Wherein, U(k)min is the minimum value of the three-phase voltage collected at time k;

[0027] If Uflag == 1, go to step 9);

[0028] 7) Calculate the negative-sequence voltage alarm value as follows:

[0029]

[0030] Wherein, U2(k) is the negative-sequence value of the voltage at time k, which can be calculated by using the conventional power system method;

[0031] If Uflag == 1, go to step 9);

[0032] 8) Calculate the current mutation value as follows:

[0033]

[0034] Wherein, I(k)max is the maximum value of the three-phase current at time k, and I(k), I(k - 1) are the current values corresponding to the maximum value of the three-phase current at times k and k - 1;

[0035] 9) If Uflag == 1 and Iflag == 1, issue an alarm.

[0036] Furthermore, the M point calculated in step 1) is greater than 1440 points, and the voltage and current values are all three-phase collected values.

[0037] The voltage alarm method provided by the present invention automatically calculates the lower limit value of current operation and the normal voltage value of voltage operation according to the data of the acquisition device, then calculates the low-voltage alarm value, unbalanced voltage alarm value, and negative-sequence voltage alarm value according to the real-time voltage, and combines the current mutation value, so that the voltage and current judgment values can be automatically adapted according to the acquired information, which will not affect the judgment of current protection during normal operation, and can issue a voltage alarm during abnormality, improving the protection reliability. Detailed implementation manners

[0038] The following further describes the technical solution of the present invention in detail with specific embodiments, but these embodiments do not limit the present invention. Any similar structure and its similar changes using the present invention shall be included in the protection scope of the present invention. The commas in the present invention all represent the relationship of "and", and the English letters in the present invention are case-sensitive.

[0039] A voltage alarm method provided by an embodiment of the present invention specifically includes the following steps:

[0040] 1) Obtain the three-phase current values, three-phase voltage values, and overcurrent signals of the N nearest points to the sampling point k from the acquisition device. Each point contains seven values, namely the voltages of phases A, B, and C, the current values of phases A, B, and C, and the overcurrent signal at the point k. Find all the target points M that can simultaneously meet Condition 1, Condition 2, and Condition 3 from the current, voltage values, and overcurrent signals of the N points.

[0041] Condition 1:

[0042] 1.1×Uaver > U(ka) > 0.1×Uaver, and 1.1×Uaver > U(kb) > 0.1×Uaver, and 1.1×Uaver > U(kc) > 0.1×Uaver;

[0043] Wherein, Uaver is the average value of the three-phase voltage acquisition values of the N sampling points in the sampling point sequence S, U(ka) is the A-phase voltage acquisition value of the sampling point k, U(kb) is the B-phase voltage acquisition value of the sampling point k, and U(kc) is the C-phase voltage acquisition value of the sampling point k;

[0044] Condition 2:

[0045] 1.1×Iaver > I(ka) > 0.1×Iaver, and 1.1×Iaver > I(kb) > 0.1×Iaver, and 1.1×Iaver > I(kc) > 0.1×Iaver;

[0046] Wherein, Iaver is the average value of the three-phase current acquisition values of the N sampling points in the sampling point sequence S, I(ka) is the A-phase current acquisition value of the sampling point k, I(kb) is the B-phase current acquisition value of the sampling point k, and I(kc) is the C-phase current acquisition value of the sampling point k;

[0047] Condition 3:

[0048] Wherein, Condition 3 is that no overcurrent signal occurs at the kth point of the power line collected by the power data acquisition device;

[0049] The calculated number of M points is greater than 1440 points, and the voltage and current values are all three-phase acquisition values;

[0050] 2) Calculate the lower limit value of the current operation when the sampling point belongs to the loop power supply. The calculation method is as follows: Sort the current values of the M points from small to large, and take out the current value at the 35th percentile as the lower limit value of the current operation, Idz;

[0051] 3) Calculate the normal voltage value of the voltage operation when the sampling point belongs to the loop power supply. The calculation method is as follows: Sort the voltage values of the M points from small to large, and take out the voltage value at the 50th percentile as the normal voltage value of the voltage operation, Udz;

[0052] 4) At the current k moment, the three-phase voltage values and three-phase current values can be obtained, and the initial voltage alarm value Uflag = 0 and the current alarm value Iflag = 1 are set;

[0053] 5) Calculate the low-voltage alarm value as follows:

[0054]

[0055] Where U(k) is the voltage value at the k moment, U(k)max is the maximum value of the three-phase voltages collected at the k moment, and I(k) is the current value of the phase where the maximum value is located at the k moment;

[0056] If Uflag == 1, go to step 9);

[0057] 6) Calculate the unbalanced voltage alarm value as follows:

[0058]

[0059] Where U(k)min is the minimum value of the three-phase voltages collected at the k moment;

[0060] If Uflag == 1, go to step 9);

[0061] 7) Calculate the negative-sequence voltage alarm value as follows:

[0062]

[0063] Where U2(k) is the negative-sequence voltage value at the k moment, which can be calculated by using the conventional power system method;

[0064] If Uflag == 1, go to step 9);

[0065] 8) Calculate the current mutation value as follows:

[0066]

[0067] Where I(k)max is the maximum value of the three-phase currents at the k moment, and I(k), I(k - 1) are the current values corresponding to the phase where the maximum value of the three-phase currents at the k moment is located at the k and k - 1 moments;

[0068] 9) If Uflag == 1 and Iflag == 1, an alarm is issued.

[0069] The voltage alarm method provided by the present invention can not affect the judgment of current protection during normal operation, can issue a voltage alarm during abnormal conditions, and can improve the reliability of protection.

Claims

1. A voltage alarm method, characterized in that, The specific steps are as follows: 1) Obtain the three-phase current values, three-phase voltage values, and overcurrent signals of the N nearest points to the sampling point k from the acquisition device. Each point contains 7 values, namely the voltages of three phases A, B, and C, the current values of three phases A, B, and C, and the overcurrent signal at the point k. Find all the target points M that can simultaneously meet Condition 1, Condition 2, and Condition 3 from the current, voltage values, and overcurrent signals of the N points; Condition 1: 1.1×Uaver > U(ka) > 0.1×Uaver, and 1.1×Uaver > U(kb) > 0.1×Uaver, and 1.1×Uaver > U(kc) > 0.1×Uaver; In the formula, Uaver is the average value of the three-phase voltage acquisition values of the N sampling points in the sampling point sequence S, U(ka) is the A-phase voltage acquisition value of the sampling point k, U(kb) is the B-phase voltage acquisition value of the sampling point k, and U(kc) is the C-phase voltage acquisition value of the sampling point k; Condition 2: 1.1×Iaver > I(ka) > 0.1×Iaver, and 1.1×Iaver > I(kb) > 0.1×Iaver, and 1.1×Iaver > I(kc) > 0.1×Iaver; In the formula, Iaver is the average value of the three-phase current acquisition values of the N sampling points in the sampling point sequence S, I(ka) is the A-phase current acquisition value of the sampling point k, I(kb) is the B-phase current acquisition value of the sampling point k, and I(kc) is the C-phase current acquisition value of the sampling point k; Condition 3: In the formula, Condition 3 is that there is no overcurrent signal occurring at the kth point of the power line collected by the power data acquisition device; 2) Calculate the lower limit value of current operation when the loop to which the sampling point belongs supplies power. The calculation method is as follows: Sort the current values of point M from smallest to largest, and take the current value ranked 35% as the lower limit value of current operation Ida; 3) Calculate the normal voltage value of voltage operation when the loop to which the sampling point belongs supplies power. The calculation method is as follows: Sort the voltage values of point M from smallest to largest, and take the voltage value ranked 50% as the normal voltage value of voltage operation Uda; 4) At the current k moment, the three-phase voltage values and three-phase current values can be obtained. Set the initial voltage alarm value Uflag = 0 and the current alarm value Iflag = 1; 5) Calculate the low voltage alarm value as follows: In the formula, U(k) is the voltage value at the kth moment, U(k)max is the maximum value of the three-phase voltages collected at the kth moment, and I(k) is the current value of the phase where the maximum value is located at the kth moment; If Uflag == 1, go to step 9); 6) Calculate the unbalanced voltage alarm value as follows: In the formula, U(k)min is the minimum value of the three-phase voltages collected at the kth moment; If Uflag == 1, go to step 9); 7) Calculate the negative sequence voltage alarm value as follows: In the formula, U2(k) is the voltage negative sequence value at the kth moment, which can be calculated by the conventional power system method; If Uflag == 1, go to step 9); 8) Calculate the current mutation value as follows: In the formula, I(k)max is the maximum value of the three-phase currents at the kth moment, and I(k), I(k - 1) are the current values corresponding to the phase where the maximum value of the three-phase currents at the kth and k - 1 moments is located; 9) If Uflag == 1 and Iflag == 1, an alarm is issued.

2. The voltage alarm method according to claim 1, characterized in that The M point calculated in step 1) is greater than 1440 points, and the voltage and current values are all three-phase acquisition values.

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