Current protection unbalanced voltage blocking method

Abstract

The application discloses a current protection unbalanced voltage locking method, and relates to the technical field of power systems.The method first screens target points meeting set conditions from data sampling points of a power data acquisition device in the latest day, then calculates voltage judgment threshold values according to the acquisition data of the target points, calculates voltage unbalance values at the current time according to real-time three-phase voltage acquisition values of the power data acquisition device, compares the calculated voltage unbalance values with the voltage judgment threshold values, and timely sends a locking current protection signal according to the comparison result.The method provided by the application is used for overcurrent protection of a power line.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system, in particular to a current protection unbalanced voltage blocking method. BACKGROUND

[0002] The power data acquisition device of power system all uses current transformer to acquire current value, once finds that the acquired current value is too high, will send corresponding alarm signal to inform the current protection device in system to execute current protection action.

[0003] There are usually more rotating equipment in power system, the starting current of the motor of these rotating equipment is too high instantaneously when starting, which belongs to normal phenomenon, under this condition, current protection action needs to be avoided to be executed; but under normal operation, the instantaneously too high current of motor is not allowed, under this condition, current protection action needs to be executed.

[0004] In order to identify the above two overcurrent states, the existing power data acquisition device is artificially set voltage and current judgment threshold in the device, when the acquired voltage and current exceed the set threshold, the current protection device is informed to execute current protection action. This artificial setting method is not only time-consuming and laborious, but also the voltage and current values of different power lines are not the same, so the voltage and current judgment thresholds required to be set by the power data acquisition devices on different power lines are also not the same, and setting errors are easy to occur, which will cause the current protection device to malfunction. SUMMARY

[0005] In view of the defects in the prior art, the technical problem to be solved by the present application is to provide a current protection unbalanced voltage blocking method which can adaptively set voltage judgment threshold according to the voltage value of power line, so as to avoid the malfunction of current protection device.

[0006] In order to solve the above technical problem, the current protection unbalanced voltage blocking method provided by the present application is characterized in that the specific steps are as follows:

[0007] 1) Set the data sampling times of power data acquisition device per day as n times, then the data sampling points of power data acquisition device per day have n;

[0008] Select the n data sampling points of power data acquisition device in the last day to form a sampling point sequence S, and select all target points from the sampling point sequence S to form a target point sequence M;

[0009] The rule for screening target points is: for any sampling point k in the sampling point sequence S, if the sampling point k can meet conditions 1 and 2 at the same time, the sampling point k is defined as a target point;

[0010] Condition 1:

[0011] and and ;

[0012] wherein, is the average value of the three-phase voltage collection values of n sampling points in the sampling point sequence S, is the A-phase voltage collection value of sampling point k, is the B-phase voltage collection value of sampling point k, is the C-phase voltage collection value of sampling point k;

[0013] Condition 2: At the time of sampling point k, there is no overcurrent signal occurrence in the power line collected by the power data collection device;

[0014] 2) Sort the three-phase voltage collection values of each target point in the target point sequence M from small to large, and define the phase voltage collection values arranged in the first 5% positions as the voltage judgment threshold Udz;

[0015] 3) Define the current data sampling time of the power data collection device as t time;

[0016] 4) Calculate the voltage imbalance value at t time, and the specific calculation formula is:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] wherein, is the voltage imbalance value at t time, is the A-phase voltage value collected by the power data collection device at t-i time, is the B-phase voltage value collected by the power data collection device at t-i time, The C-phase voltage value collected by the electric power data collection device at t-i moment, t-i moment refers to i data sampling moments before t moment, D is the data sampling number of the electric power data collection device within 1000 ms, The electric angle, =360 / D;

[0027] 5) If >Udz, the current protection signal of the current protection device of the electric power line is sent out;

[0028] 6) After waiting for the electric power data collection device to reach the next data sampling moment, returning to step 3).

[0029] The current protection unbalanced voltage blocking method provided by the application calculates the voltage judgment threshold according to the historical collection data of the last day, calculates the current voltage unbalance value according to the real-time three-phase voltage collection value, and judges whether the current protection blocking signal needs to be sent out through the comparison between the voltage unbalance value and the voltage judgment threshold, so that the voltage judgment threshold of the electric power line can be automatically adapted according to the collection information, manual setting is not needed, the judgment of the current protection will not be affected in the normal operation, the current protection can be blocked in the abnormal situation, and the misoperation of the current protection device can be avoided. DETAILED DESCRIPTION

[0030] The technical solutions of the application are further described in detail below in combination with specific embodiments, but the embodiments are not used to limit the application, any similar structure and similar changes thereof should be included in the protection scope of the application, the dots in the application represent the relationship of sum, and the English letters in the application are case-sensitive.

[0031] The current protection unbalanced voltage blocking method provided by the embodiment of the application has the characteristics that the specific steps are as follows:

[0032] 1) If the data sampling number of the electric power data collection device is n times per day, then the data sampling points of the electric power data collection device are n per day;

[0033] Selecting the n data sampling points of the electric power data collection device in the last day to form a sampling point sequence S, and selecting all target points from the sampling point sequence S to form a target point sequence M;

[0034] The rule for screening the target points is that if any sampling point k in the sampling point sequence S meets conditions 1 and 2 at the same time, the sampling point k is defined as a target point;

[0035] Condition 1:

[0036] And And ;

[0037] In the formula, is the average value of the three-phase voltage collection values of n sampling points in the sampling point sequence S, is the A-phase voltage collection value of sampling point k, is the B-phase voltage collection value of sampling point k, is the C-phase voltage collection value of sampling point k;

[0038] Condition 2: At the time of sampling point k, there is no overcurrent signal of the power line collected by the power data collection device;

[0039] 2) Sort the three-phase voltage collection values of each target point in the target point sequence M from small to large, and define the phase voltage collection values arranged in the first 5% positions as the voltage judgment threshold Udz;

[0040] 3) Define the current data sampling time of the power data collection device as t time;

[0041] 4) Calculate the voltage imbalance value at t time, and the specific calculation formula is:

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051] In the formula, is the voltage imbalance value at t time, is the A-phase voltage value collected by the power data collection device at t-i time, is the B-phase voltage value collected by the power data collection device at t-i time, is the C-phase voltage value collected by the power data collection device at t-i time, t-i time refers to the previous i data sampling times of t time, and D is the data sampling number of the power data collection device within 1000 ms, is the electric angle, = 360 / D;

[0052] 5) If > Udz, then send a lockout current protection signal to the current protection device of the power line;

[0053] 6) Wait until the next data sampling time is reached by the power data acquisition device, and return to step 3).

Claims

1. A current protection unbalanced voltage blocking method, characterized in that, The specific steps are as follows: 1) If the power data acquisition device samples data n times per day, then the power data acquisition device has n data sampling points per day; Select n data sampling points from the power data acquisition device on the most recent day to form a sampling point sequence S, and then filter all target points from the sampling point sequence S to form a target point sequence M; The rule for selecting target points is: for any sampling point k in the sampling point sequence S, if the sampling point k can satisfy both condition 1 and condition 2 at the same time, then the sampling point k is defined as the target point; Condition 1: ,and ,and ; In the formula, This represents the average value of the three-phase voltage collected from n sampling points in the sampling point sequence S. The voltage acquisition value of phase A at sampling point k. The voltage acquisition value of phase B at sampling point k. The sampled value of phase C voltage at sampling point k; Condition 2: At sampling point k, no overcurrent signal occurs in the power line collected by the power data acquisition device; 2) Sort the three-phase voltage acquisition values ​​of each target point in the target point sequence M from smallest to largest, and then define the phase voltage acquisition values ​​in the first 5% as the voltage judgment threshold Udz; 3) Define the current data sampling time of the power data acquisition device as time t; 4) Calculate the voltage imbalance value at time t. The specific calculation formula is as follows: ， ， ， ， ， ， ， ， ， In the formula, Let be the voltage imbalance value at time t. This represents the A-phase voltage value acquired by the power data acquisition device at time ti. This represents the B-phase voltage value acquired by the power data acquisition device at time ti. Let be the C-phase voltage value collected by the power data acquisition device at time ti, where time ti refers to the i-th data sampling time preceding time t. D is the number of data samples collected by the power data acquisition device within 1000ms. For electrical angle, =360 / D; 5) If >Udz, then a blocking current protection signal is sent to the current protection equipment of the power line; 6) After the power data acquisition device reaches the next data sampling time, return to step 3).

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