Contact failure early warning method and switch device

Abstract

The application relates to the field of low-voltage electrical apparatuses, in particular to a contact failure early warning method, which measures the contact resistance of a switch electrical apparatus, obtains the average value of the contact resistance according to the contact resistance, fits a plurality of average values of the contact resistance, obtains a contact resistance fitting line according to the fitting, judges whether one or a plurality of continuously obtained average values of the contact resistance exceeds the early warning line, and early warns the contact failure of the switch electrical apparatus, without changing the original structure of the switch electrical apparatus, with good universality, a simple measurement method, high measurement precision and accurate early warning results.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-voltage electrical apparatus, in particular to a contact failure early warning method and a switch electrical apparatus applying the method. BACKGROUND

[0002] Contactor is generally used for quickly cutting off AC and DC main circuit and frequently turning on and off large current control circuit, so it is often used for controlling motor as control object, and can also be used for controlling factory equipment, electric heater, working mother machine and various power loads, etc. Contactor not only can turn on and off circuit, but also has low voltage release protection function, and is one of important elements in automatic control system.

[0003] With the continuous improvement of electrical level, the reliability and stability of power distribution system are also increasingly high. If contactor fails, it will affect the whole control system due to its large control capacity, frequent operation and remote control characteristics. However, there is no mature contactor product on the market that can be used to find contactor failure and give early warning, so as to replace the contactor early, eliminate the hidden danger of power safety and reduce economic loss.

[0004] Some existing technical patents, such as Chinese patent with application number CN2016108534909 and name of Contactor Fault Early Warning Method and Early Warning Device, obtain the time difference between contactor control instruction sending and completion to judge the wear of each part of the mechanism, and give early warning to the contactor. This kind of method belongs to indirect measurement method, and the precision is not high. In addition, the decay of main spring force value and the wear of some non-weight parts will affect the measurement result. In addition, different contactor products will have different change rules of control instruction time difference after use due to different mechanism characteristics, and do not have universality. SUMMARY

[0005] The present application aims to overcome the defects of the prior art, and provides two contact failure early warning methods, which are simple in method, accurate in early warning result and good in universality. The present application also provides a switch electrical apparatus applying the early warning method, which is simple in structure, easy to operate and good in universality.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A contact failure early warning method, comprising the following steps:

[0008] Step one: obtaining contact resistance value of switch electrical apparatus, and obtaining contact resistance average value of n contact resistance values every time n contact resistance values are obtained, n is an integer greater than or equal to 1;

[0009] Step two: after obtaining m1 contact resistance averages, m1 is an integer greater than or equal to 2, fitting the obtained contact resistance averages to obtain a fitted contact resistance fitting line, and obtaining the slope of the contact resistance fitting line;

[0010] Step three: offsetting the obtained contact resistance fitting line to the slope of the fitting line by a preset warning threshold to obtain a contact resistance warning line;

[0011] Step four: after obtaining the contact resistance warning line, one or more consecutive contact resistance averages obtained subsequently exceed the contact resistance warning line in the trend direction, and a warning signal is sent.

[0012] Preferably,

[0013] Step one: obtaining the contact resistance value of the switch electric appliance, and then obtaining the contact resistance average of n contact resistance values, n being an integer greater than or equal to 1;

[0014] Step two: after obtaining m2 contact resistance averages, m2 being an integer greater than or equal to 2, first fitting the obtained contact resistance averages to obtain a first fitted contact resistance fitting line, and recording the slope of the contact resistance fitting line, then every p1 contact resistance averages, p1 being an integer greater than or equal to 1, fitting the current contact resistance averages to obtain a contact resistance fitting line, and recording the slope of the contact resistance fitting line, and when p2 slopes are obtained, p2 being an integer greater than or equal to 2, verifying the slopes, if the verification is passed, proceeding to step three, if the verification is not passed, every p1 contact resistance averages, p1 being an integer greater than or equal to 1, fitting the current contact resistance averages to obtain a contact resistance fitting line, and obtaining the slope of the current contact resistance fitting line, and verifying the slope, until the verification is passed, and then proceeding to step three;

[0015] Step three: offsetting the verified contact resistance fitting line to the slope of the fitting line by a preset warning threshold to obtain a contact resistance warning line;

[0016] Step four: after obtaining the contact resistance warning line, one or more consecutive contact resistance averages obtained subsequently exceed the contact resistance warning line in the trend direction, and a warning signal is sent.

[0017] Preferably, in step two, the method for verifying the slope of the fitting line is that when at least two consecutive slopes are less than a preset slope threshold, the verification is passed, otherwise the verification is not passed.

[0018] Preferably, in step two, the method for verifying the slope of the fitting line is to calculate the variance S of the last p3 contact resistance slopes, p3 is an integer greater than or equal to 2, when the variance S is greater than or equal to a preset variance threshold S0, the verification fails, and when the variance S is less than the variance threshold S0, the verification passes.

[0019] Preferably, the early warning threshold is a preset fixed constant or a preset proportional value.

[0020] Preferably, in step three, the contact resistance fitting line is offset by a preset fixed constant according to the trend direction of the contact resistance fitting line, and then the contact resistance early warning line is obtained.

[0021] Alternatively, in step three, the contact resistance fitting line is offset by a preset proportional value x% according to the trend direction of the contact resistance fitting line, and then the contact resistance early warning line is obtained.

[0022] Preferably, in step one, after obtaining the contact resistance value when the switch electric appliance is closed for the first time, the contact resistance value is obtained every k times of closing, k is an integer greater than or equal to 1.

[0023] Preferably, the contact resistance value is calculated by the current flowing through the moving contact and the static contact, and the voltage across the moving contact and the static contact after the switch electric appliance is closed.

[0024] Preferably, the contact resistance average value is calculated by using the mean algorithm on n contact resistance values.

[0025] Preferably, 0.005≤S0≤0.015.

[0026] Preferably, the fixed constant is 0.001-0.003, and the proportional value x% is 5%-15%.

[0027] A switch electric appliance characterized in that it applies the contact failure early warning method.

[0028] The contact failure early warning method of the present application can early warn the contact failure of the switch electric appliance by measuring the contact resistance of the switch electric appliance, without changing the original structure of the switch electric appliance, and has good universality, simple measurement method, high measurement accuracy and accurate early warning result.

[0029] The switch electric appliance of the present application adopts the contact failure early warning method of the present application, and has simple structure, simple operation and good universality. The detection device is preferably a contactor, and can also be a switch electric appliance such as a circuit breaker. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structure diagram of the cooperation of the moving contact and the static contact of the contactor of the present application;

[0031] Figure 2 is a logic block diagram of the contactor contact failure early warning method of the present application;

[0032] Figure 3 is a curve diagram of the contact resistance average value, the contact resistance slope, the contact resistance fitting line and the contact resistance early warning line in the coordinate system of the present application. DETAILED DESCRIPTION

[0033] The embodiments given below in conjunction with the accompanying Figure 1 -3 further illustrate the specific implementation of the contact failure early warning method of the present application. The contact failure early warning method of the present application is not limited to the description of the following embodiments.

[0034] The switch electric appliance of the present application applies the contact failure early warning method of the present application. The switch electric appliance is preferably a contactor, and can also be a circuit breaker or other switch electric appliance. The contact failure early warning method of the present application is further illustrated below taking the contactor as an example.

[0035] As Figure 1 shown, it is a schematic diagram of the cooperation of the moving contact 10 and the static contact 20 of the contactor. The moving contact 10 moves up and down and closes / disconnects with the static contact 20. Each time the moving contact 10 and the static contact 20 are closed and disconnected, the moving contact 10 and the static contact 20 will be worn due to the collision and arc ablation, and the wear of the surfaces of the moving contact 10 and the static contact 20 will form a non-smooth surface, which will inevitably cause the reduction of the contact area between the two, thereby causing the increase of the contact resistance of the two. The contact failure early warning method of the present application is based on the above process and principle, and measures the contact resistance of the moving contact 10 and the static contact 20, thereby realizing the accurate early warning of the contact failure of the contactor and ensuring the reliable and effective work of the contactor, thereby ensuring the normal operation of the entire circuit where the contactor is located.

[0036] The first contact failure early warning method disclosed by the present application comprises the following steps:

[0037] Step one: obtaining the contact resistance value of the contactor, and then obtaining the contact resistance average value of n contact resistance values each time n contact resistance values are obtained, wherein n is an integer greater than or equal to 1.

[0038] Step two: obtaining m contact resistance average values, wherein m1 is an integer greater than or equal to 2, fitting the obtained contact resistance average values to obtain a fitted contact resistance fitting line, and obtaining the slope of the fitting line of the contact resistance fitting line.

[0039] It should be noted that the value of m should not be too small in order to avoid the influence of accidental factors of the obtained contact resistance average values on the accuracy of the detection result. Preferably, m1 is greater than or equal to 100.

[0040] Step three: the obtained contact resistance fitting line is offset to the direction of its fitting line slope by a preset early warning threshold to obtain a contact resistance early warning line.

[0041] Step four: when one or more of the subsequently obtained contact resistance average values exceeds the contact resistance early warning line, an early warning signal is sent out.

[0042] The contact failure early warning method of the application can early warn the contact failure of the switch device by measuring the contact resistance of the contactor, without changing the original structure of the switch device, and has good universality, simple measurement method, high measurement accuracy and accurate early warning result.

[0043] The application further discloses a second contact failure early warning method, which comprises the following steps:

[0044] Step one: the contact resistance values of the contactor are obtained, and the contact resistance average value of n contact resistance values is calculated every time n contact resistance values are obtained, wherein n is an integer greater than or equal to 1. Step two: after obtaining m2 contact resistance averages, m2 is an integer greater than or equal to 2, the first fitting is performed on the obtained contact resistance average values to obtain a contact resistance fitting line, and the fitting line slope of the contact resistance fitting line is recorded, then the fitting is performed on all the currently obtained contact resistance average values every time p1 contact resistance average values are obtained, p1 is an integer greater than or equal to 1, the contact resistance fitting line is obtained, and the fitting line slope of the contact resistance fitting line is obtained, when p2 fitting line slopes are obtained, p2 is an integer greater than or equal to 2, the fitting line slope is verified, if the verification is passed, step three is entered, if the verification is not passed, the fitting is performed on all the currently obtained contact resistance average values every time p1 contact resistance average values are obtained, p1 is an integer greater than or equal to 1, the contact resistance fitting line is obtained, the fitting line slope of the contact resistance fitting line is obtained, and the fitting line slope is verified, until the verification is passed, and then step three is entered.

[0045] Preferably, in step two, the method for verifying the contact resistance slope of the contact resistance fitting line is that the contact resistance slope is less than a preset slope threshold, then the verification is passed, or at least two consecutive fitting line slopes are less than a preset slope threshold, then the verification is passed, otherwise the verification is not passed.

[0046] Preferably, in step two, the method for verifying the fitting line slope is that the variance S of the p3 contact resistance slopes obtained recently is calculated, p3 is an integer greater than or equal to 2, when the variance S is greater than or equal to a preset variance threshold S0, the verification is not passed, and when the variance S is less than the variance threshold S0, the verification is passed.

[0047] Preferably, 0.005≤S0≤0.015. Further preferably, SO can be any one of 0.006, 0.007, 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014.

[0048] Step three: the contact resistance warning line is obtained by offsetting the contact resistance fitting line by a preset warning threshold in the direction of the slope of the fitting line.

[0049] Preferably, the warning threshold is a preset fixed constant or a preset proportion value. When the warning threshold is a preset fixed constant, in step three, the contact resistance fitting line is offset by the preset fixed constant in the direction of the slope of the fitting line, and then the contact resistance warning line is obtained. When the warning threshold is a preset proportion value, in step three, the contact resistance fitting line is offset by the preset proportion value x% in the direction of the slope of the fitting line, and then the contact resistance warning line is obtained.

[0050] Preferably, the fixed constant is 0.001-0.003, and the proportion value x% is 5%-15%. Further preferably, the fixed constant is 0.002, and x% is 10%.

[0051] Step four: when one or more consecutive contact resistance average values obtained subsequently exceed the contact resistance warning line in the trend direction, a warning signal is sent.

[0052] The detection method of the application avoids the influence of accidental factors of the contact resistance fitting line on the contact resistance warning line by verifying the slope of the fitting line, and further improves the accuracy of the detection result.

[0053] Preferably, in step one, after obtaining the contact resistance value when the contactor is closed for the first time, the contact resistance values are obtained every k times of closure, and k is an integer greater than or equal to 1. Specifically, when k=1, the contact resistance value of the contactor is obtained when the contactor is closed for the first time, and then the contact resistance values of the contactor are obtained when the contactor is closed for the third time, the fifth time, and the seventh time. In this way, the contact resistance value of the contactor is obtained every time the contactor is closed between two times of obtaining the contact resistance value. Of course, k can also be 2, 3, 4, 5, or 6, but it should not be too large to avoid amplifying the influence of accidental factors of the contact resistance value.

[0054] Preferably, the contact resistance value is calculated from the current flowing through the moving and stationary contacts of the switching device after the contactor is closed, and the voltage across the moving and stationary contacts. Furthermore, after each contactor closure, the current flowing through the moving and stationary contacts is continuously measured within 20-50 ms, and the voltage across the moving and stationary contacts is also continuously measured.

[0055] Preferably, the average contact resistance is calculated by using an average value algorithm on n contact resistance values.

[0056] like Figure 3 In the coordinate system shown, the broken line a is formed by connecting multiple average values ​​of contact resistance, the curve b is formed by connecting the slopes of multiple contact resistance fitting lines, the line c is the contact resistance fitting line, and the line d is the contact resistance warning line.

[0057] The following is the first embodiment of the second contact failure early warning method of the present invention.

[0058] The contact failure early warning method of this embodiment includes the following steps:

[0059] Step 1: Obtain the contact resistance when the contactor is closed. Calculate the average contact resistance of the five obtained contact resistance values.

[0060] Step 2: After obtaining 100 average contact resistance values, perform an initial fitting on these 100 average contact resistance values ​​to obtain an initial fitted contact resistance line and record its slope. Then, obtain another average contact resistance value and fit it to all the currently obtained average contact resistance values ​​to obtain a new fitted contact resistance line and record its slope. After obtaining two fitted line slopes, verify the slopes. If both slopes are less than a preset slope threshold, the verification is successful, and proceed to Step 3. Otherwise, the verification fails. For each additional average contact resistance value obtained, fit it to all the currently obtained average contact resistance values ​​to obtain a new fitted contact resistance line and record its slope. Then, compare the slopes of the two most recently obtained fitted lines with the preset slope threshold until the verification is successful, and proceed to Step 3.

[0061] Step 3: After verification, the slope direction of the latest obtained contact resistance fitting line is offset by a preset warning threshold. The warning threshold is a preset fixed constant, thus obtaining the contact resistance warning line.

[0062] Step 4: After obtaining the contact resistance warning line, if one or more of the subsequently obtained average contact resistance values ​​exceed the contact resistance warning line in their trend direction, a warning signal will be issued.

[0063] The following is a second embodiment of the second contact failure early warning method of the application.

[0064] The contact failure early warning method of the embodiment comprises the following steps:

[0065] Step one: obtain the contact resistance when the contactor is closed, and then obtain the average value of the contact resistance of the 10 contact resistance values obtained each time;

[0066] Step two: after obtaining 150 contact resistance average values, perform first fitting on the 150 contact resistance average values obtained, obtain the first fitted contact resistance fitting line, and record the fitting line slope of the first fitted contact resistance fitting line, then obtain 2 contact resistance average values, perform fitting on all the contact resistance average values obtained at present, obtain the contact resistance fitting line, and record the fitting line slope of the contact resistance fitting line, after obtaining the two fitting line slopes, verify the fitting line slopes, if the variance S of the two fitting line slopes is less than the preset variance threshold S0, the verification is passed, and step three is entered, otherwise the verification is failed, every time 2 contact resistance average values are obtained, perform fitting on all the contact resistance average values obtained at present, obtain the contact resistance fitting line, and record the fitting line slope of the contact resistance fitting line, then calculate the variance S of the two fitting line slopes obtained recently, and compare the variance S with the preset variance S0, until the verification is passed and step three is entered.

[0067] Step three: after the verification is passed, the fitting line slope of the latest obtained contact resistance fitting line is offset by a preset early warning threshold in the direction, the early warning threshold is a preset proportion x%, and the contact resistance early warning line is obtained.

[0068] Step four: after the contact resistance early warning line is obtained, one or more in the subsequent obtained contact resistance average values exceeds the contact resistance early warning line in the trend direction, and then an early warning signal is sent.

[0069] The application further discloses a switching electric appliance which applies the contact failure early warning method of the application, and the switching electric appliance is a contactor, a circuit breaker or other low-voltage switch. Of course, an independent contact detection device can also be arranged, which comprises a microcontroller, a voltage acquisition module and a current acquisition module connected with the contact of the switching electric appliance, and the contact failure early warning method of the application is applied to detect and warn the switching electric appliance.

[0070] The above is further detailed description of the present application in combination with specific preferred embodiments, and cannot be deemed as limitation of the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all should be deemed as falling within the protection scope of the present application.

Claims

1. A contact failure early warning method, characterized by, It comprises the following steps: Step one: obtain the contact resistance value of the switch electric appliance, and obtain the contact resistance average value of n contact resistance values every time n contact resistance values are obtained, n is an integer greater than or equal to 1; Step two: after obtaining m1 contact resistance averages, m1 is an integer greater than or equal to 2, fitting the obtained contact resistance averages to obtain a contact resistance fitting line, and obtaining the slope of the contact resistance fitting line; Step three: offset the obtained contact resistance fitting line to the slope of the fitting line by a preset warning threshold to obtain a contact resistance warning line; Step four: after obtaining the contact resistance warning line, one or more consecutive contact resistance averages obtained subsequently exceed the contact resistance warning line in the trend direction, and a warning signal is sent.

2. A contact failure early warning method, characterized by: It comprises the following steps: Step one: obtain the contact resistance value of the switch electric appliance, and obtain the contact resistance average value of n contact resistance values every time n contact resistance values are obtained, n is an integer greater than or equal to 1; Step two: after obtaining m2 contact resistance averages, m2 is an integer greater than or equal to 2, fitting the obtained contact resistance averages to obtain a contact resistance fitting line, and recording the slope of the contact resistance fitting line, then fitting the contact resistance averages every p1 times, p1 is an integer greater than or equal to 1, to obtain a contact resistance fitting line, and recording the slope of the contact resistance fitting line, when p2 slopes are obtained, p2 is an integer greater than or equal to 2, the slope is verified, if the verification is passed, step three is entered, if the verification is not passed, the contact resistance averages are fitted every p1 times, p1 is an integer greater than or equal to 1, to obtain a contact resistance fitting line, and the slope of the current contact resistance fitting line is obtained, and the slope is verified, until the verification is passed, then step three is entered; Step three: offset the verified contact resistance fitting line to the slope of the fitting line by a preset warning threshold to obtain a contact resistance warning line; Step four: after obtaining the contact resistance warning line, one or more consecutive contact resistance averages obtained subsequently exceed the contact resistance warning line in the trend direction, and a warning signal is sent.

3. The contact failure early warning method of claim 2, wherein: In step two, the method for verifying the slope of the fitting line is that when at least two consecutive slopes are less than a preset slope threshold, the verification is passed, otherwise the verification is not passed.

4. The contact failure early warning method of claim 2, wherein: In step two, the method for verifying the slope of the fitting line is that the variance S of the p3 contact resistance slopes obtained recently is calculated, p3 is an integer greater than or equal to 2, when the variance S is greater than or equal to a preset variance threshold S0, the verification is not passed, and when the variance S is less than the variance threshold S0, the verification is passed.

5. The contact failure warning method according to claim 1 or 3, wherein: The warning threshold is a preset fixed constant or a preset proportional value.

6. The contact failure warning method according to claim 5, wherein: In step three, the contact resistance fitting line is offset by a preset fixed constant according to the trend direction of the contact resistance fitting line, and then the contact resistance early warning line is obtained. Alternatively, in step three, the contact resistance fitting line is offset by a preset proportional value x% according to the trend direction of the contact resistance fitting line, and then the contact resistance early warning line is obtained.

7. The contact failure early warning method according to claim 1 or 2, characterized in that: In step one, after obtaining the contact resistance value when the switch device is closed for the first time, the contact resistance value is obtained every k times of closing, and k is an integer greater than or equal to 1.

8. The contact failure early warning method according to claim 1 or 2, characterized in that: The contact resistance value is calculated by the current flowing through the moving contact and the static contact, the voltage between the moving contact and the static contact after the switch device is closed, and the contact between the moving contact and the static contact.

9. The contact failure early warning method according to claim 1 or 3, characterized in that: The contact resistance average value is calculated by using the mean algorithm on n contact resistance values.

10. The contact failure early warning method of claim 4, wherein: 0.005≤S0≤0.015。 11. The contact failure early warning method of claim 6, wherein: The fixed constant is 0.001-0.003, and the proportional value x% is 5%-15%.

12. A switchgear, characterized by The application of the contact failure early warning method according to any one of claims 1-4, 6, 10-11.

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