CN112816902A - Method and device for monitoring alternating current leakage current of surge protector and surge protector - Google Patents
Method and device for monitoring alternating current leakage current of surge protector and surge protector Download PDFInfo
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Abstract
The invention provides a method and a device for monitoring alternating current leakage current of a surge protector, and the surge protector, wherein the method comprises the following steps: measuring the alternating current leakage current of the surge protector; measuring the working voltage and/or working temperature of the surge protector; calculating an alarm threshold value under the working voltage based on the measured working voltage and/or working temperature; and comparing the alternating current leakage current with the alarm threshold, and sending an alarm signal when the alternating current leakage current is larger than the alarm threshold, and/or comparing the average value of the alternating current leakage current with the average value of the alarm threshold, and sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold.
Description
Technical Field
The invention relates to the field of electronic detection, in particular to a method and a device for monitoring alternating current leakage current of a surge protector, and the surge protector comprising the device.
Background
Surge Protectors (SPDs) are widely used in fields such as lightning current Protection. During use, the SPD may be affected by lightning or overvoltage, and performance degradation occurs, resulting in a reduction or even failure of the protection function. Therefore, the SPD needs to be checked periodically to monitor the degradation state of the SPD.
Measuring leakage current of the SPD is commonly employed to determine the degradation state. When the performance of the SPD degrades, the leakage current through the SPD increases. If the measured leakage current value exceeds a certain reference value, it can be determined that the SPD performance degradation exceeds a normal level, which needs to be replaced.
However, currently, the leakage current of the SPD is usually measured by offline manual detection, i.e. the SPD is powered off or a piezoresistor module on the SPD is taken out, and an SPD parameter tester is used for measurement. The measuring method needs to be regularly detected on the using site, the using and maintaining cost is high, and the measured leakage current is direct current leakage current which is different from the alternating current working condition of the SPD in actual work.
Disclosure of Invention
The invention aims to provide a method and a device for monitoring alternating current leakage current of a surge protector, and the surge protector comprising the device. The method calculates an alarm threshold based on the measured operating voltage and/or operating temperature, compares the AC leakage current with the alarm threshold, and sends an alarm signal when the AC leakage current is greater than the alarm threshold. The method can dynamically determine the alarm threshold value of the alternating current leakage current, and the threshold value dynamically changes along with the working voltage and/or the working temperature, so that the proper alarm threshold value can be determined according to different alternating current working voltages and/or working temperatures.
An embodiment of the present invention provides a method for monitoring ac leakage current of a surge protector, the method including: measuring the alternating current leakage current of the surge protector; measuring the working voltage and/or working temperature of the surge protector; calculating an alarm threshold value under the working voltage and/or the working temperature based on the measured working voltage and/or the working temperature; and comparing the alternating current leakage current with the alarm threshold, and sending an alarm signal when the alternating current leakage current is larger than the alarm threshold, and/or comparing the average value of the alternating current leakage current with the average value of the alarm threshold, and sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold.
In some examples, where the operating voltage is measured, the calculating comprises calculating by a calculation function that represents an alarm threshold magnitude at a certain operating voltage.
In some examples, the calculation function is:
when U is turnedn≤U≤UmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
u is the measured working voltage of the surge protector;
Ialarm(U)represents an alarm threshold at the operating voltage U;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminRepresents the minimum operating voltage of the surge protector, and Un、UmaxAnd UminAre all known constants;
In some examples, where the operating temperature is measured, the calculating comprises calculating by a calculation function that represents an alarm threshold magnitude at a certain operating temperature.
In some examples, the calculation function is:
when T isn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when T ismin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
t is the measured working temperature of the surge protector;
Ialarm(T)represents an alarm threshold at the operating voltage T;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
In some examples, where the operating voltage and the operating temperature are measured, the calculating includes calculating by a calculation function that represents an alarm threshold magnitude at a certain operating temperature.
In some examples, the calculated function is a fitting matrix of the alarm threshold with respect to the operating voltage and the operating temperature.
In some examples, the calculation function is:
when U is turnedn≤U≤UmaxAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedn≤U≤UmaxAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
u is the measured working voltage of the surge protector, and T is the measured working temperature of the surge protector;
Ialarm(U，T)represents the alarm threshold at the operating voltage U and the operating temperature T;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminRepresents the minimum operating voltage of the surge protector, and Un、UmaxAnd UminAre all known constants;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
In some examples, wherein in the case of measuring the operating voltage and the operating temperature, the calculating comprises bilinear interpolation calculating by an alarm threshold list, the alarm threshold list being stored in the processing unit and comprising alarm threshold magnitude values at a certain operating voltage and operating temperature.
In some examples, the measuring the ac leakage current of the surge protector includes measuring an effective value and/or a maximum value of the ac leakage current of the surge protector.
An embodiment of the present invention provides a device for monitoring ac leakage current of a surge protector, the device comprising: the current measuring module is used for measuring the alternating current leakage current of the surge protector; the device comprises a voltage measuring module and/or a temperature measuring module, wherein the voltage measuring module measures the working voltage of the surge protector, and the temperature measuring module measures the working temperature of the surge protector; and the processing unit is configured to calculate an alarm threshold value under the working voltage and/or the working temperature based on the measured working voltage and/or the working temperature, compare the alternating current leakage current with the alarm threshold value, send an alarm signal when the alternating current leakage current is larger than the alarm threshold value, and/or compare an average value of the alternating current leakage current with an average value of the alarm threshold value, and send an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold value.
In some examples, the processing unit is configured to calculate by a calculation function representing an alarm threshold magnitude at a certain operating voltage and/or operating temperature.
In some examples, where the apparatus includes a voltage measurement module and a temperature measurement module, the processing unit is configured to perform bilinear interpolation calculations with an alarm threshold list stored in the processing unit and including alarm threshold magnitude values at an operating voltage and an operating temperature.
The embodiment of the invention also provides a surge protector which comprises the device.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description only relate to some embodiments of the present invention and are not limiting on the present invention.
Fig. 1 shows a flow diagram of a method of monitoring ac leakage current of a surge protector according to an embodiment of the invention;
fig. 2 shows a flow chart of a method of monitoring ac leakage current of a surge protector according to another embodiment of the invention;
fig. 3 shows leakage current scatter plots of surge protectors of different degrees of degradation;
fig. 4 shows leakage current scatter plots of the surge protector for different degradation levels at different operating voltages;
FIG. 5 illustrates an alarm threshold-operating voltage fit curve according to an embodiment of the present invention;
FIG. 6 shows a graph of the alarm threshold fit curve of FIG. 5 versus the leakage current curve of a surge protector of different degradation levels;
fig. 7 shows a flow chart of a method of monitoring ac leakage current of a surge protector according to a further embodiment of the invention;
FIG. 8 illustrates an alarm threshold-operating voltage operating temperature relationship curve according to the embodiment shown in FIG. 7.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of specific embodiments of the present invention. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
Surge Protectors (SPDs) are widely used in fields such as lightning current Protection. During use, the SPD may be affected by lightning or overvoltage, and performance degradation occurs, resulting in a reduction or even failure of the protection function. Therefore, the SPD needs to be checked periodically to monitor the degradation state of the SPD.
The leakage current is a current formed between mutually insulated parts or between a charged part and a grounded part in an electric element through a surrounding medium or an insulating surface when a voltage is applied. Measuring the leakage current of the SPD to determine the degradation state is a common method in the industry. When the performance of the SPD deteriorates, the leakage current through the SPD increases. If the measured leakage current value exceeds a certain reference value, it can be determined that the SPD performance degradation exceeds a normal level, which needs to be replaced.
At present, the leakage current of the SPD is generally measured by off-line manual detection, namely, the SPD is powered off or a piezoresistor module on the SPD is taken out, and an SPD parameter tester is used for measuring. The measurement method needs to be regularly detected at a use site, and the use and maintenance cost is high. The SPD parameter tester used in the method is direct current detection equipment, and the detected leakage current is direct current leakage current which is different from the alternating current working condition of the SPD in actual work. When the direct current leakage current exceeds a certain direct current reference value, the SPD needs to be replaced.
An intelligent accessory device (Smart SPD) for an SPD provides an automatic online detection method, and leakage current of the SPD can be remotely monitored. The SPD is applied to an alternating current power frequency power system, so that the online measured leakage current value is the alternating current leakage current in the practical use of the SPD. When the leakage current exceeds a preset alarm threshold value, the Smart SPD sends an alarm to prompt a user to replace the SPD with the leakage current exceeding the standard.
Since the SPD is a non-linear varistor, its resistance is very sensitive to voltage. The inventors found during testing that the measured value of the ac leakage current changed significantly when different operating voltages were applied. In contrast, the range of variation of the dc leakage current is small at different operating voltages. Therefore, unlike the dc leakage current reference value, the ac leakage current alarm threshold is a completely new parameter, which needs to be defined by a new method.
In addition, the operating temperature is also a factor of the ac leakage current value. This sometimes needs to be taken into account when actually measuring.
In the present invention, the ac leakage current is an effective value and/or a maximum value of the ac leakage current. In the following description of the embodiments, the effective value of the ac leakage current is used to represent the ac leakage current value, but the present invention is not limited thereto, and the maximum value of the ac leakage current may be used depending on the measurement function of the current measurement module.
In addition, the working temperature of the present invention may refer to an ambient temperature of the surge protector, a housing temperature of the surge protector, or an internal temperature of the surge protector, but the present invention is not limited thereto. In the following description of the embodiments, the operating temperature of the surge protector is represented by the surge protector case temperature.
An embodiment of the present invention provides a method of monitoring an ac leakage current of a surge protector, the method comprising: measuring the alternating current leakage current of the surge protector; measuring the working voltage and/or working temperature of the surge protector; calculating an alarm threshold value under the working voltage and/or the working temperature based on the measured working voltage and/or the working temperature; and comparing the alternating current leakage current with the alarm threshold, and sending an alarm signal when the alternating current leakage current is larger than the alarm threshold, and/or comparing the average value of the alternating current leakage current with the average value of the alarm threshold, and sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold.
Fig. 1 shows a flow chart of a method of monitoring ac leakage current of a surge protector according to an embodiment of the invention. As shown in fig. 1, the steps of the method include:
measuring the alternating current leakage current of the surge protector;
measuring the working voltage of the surge protector;
calculating an alarm threshold;
comparing the alternating current leakage current with the alarm threshold, sending an alarm signal when the alternating current leakage current is larger than the alarm threshold, and repeatedly measuring the working voltage of the surge protector and subsequent steps when the alternating current leakage current is smaller than or equal to the alarm threshold.
According to an embodiment of the invention, an alarm threshold value at the operating voltage is calculated based on the measured operating voltage. Specifically, the calculation includes calculating by a calculation function, the calculation function representing a magnitude of the alarm threshold at a certain operating voltage.
The determination method of the calculation function will be described in detail below with reference to fig. 3 to 6 and tables 1 to 2. Fig. 3 shows leakage current scatter diagrams of the surge protectors with different degradation degrees, fig. 4 shows leakage current scatter diagrams of the surge protectors with different degradation degrees under different working voltages, fig. 5 shows a fitting curve of an alarm threshold value and a working voltage according to an embodiment of the present invention, and fig. 6 shows a comparison graph of the fitting curve of the alarm threshold value shown in fig. 5 and the leakage current curve of the surge protectors with different degradation degrees. Table 1 shows the leakage current values of the surge protector with different degrees of degradation in the dc voltage and the ac voltage, and table 2 shows the ac leakage current values of the surge protector with different degrees of degradation in the operating voltage.
Firstly, based on the existing reference value of the direct current leakage current, the appropriate alarm threshold value of the alternating current leakage current is determined through test data. A batch of SPDs with different degrees of degradation can be "manufactured" in a laboratory by means of transient overvoltage.
TABLE 1 leakage Current values of Surge protectors of different degradation degrees
As can be seen from table 1, when the SPD is severely degraded, the dc leakage current thereof is significantly increased, and thus the magnitude of the dc leakage current can be used as a reference for determining the degradation degree of the SPD. Thus, is composed of
Table 1 can determine that three SPDs numbered 37, 41, and 44 are severely deteriorated SPDs, seven SPDs numbered 36, 25, 8, 19, 29, 14, 42, and 5 are primarily deteriorated SPDs, and three SPDs numbered a1, a2, and A3 are completely new SPDs, which can be considered to be almost not deteriorated.
The inventors found that the alternating current leakage current also exhibits a variation law similar to that of the direct current leakage current, that is, as the degree of deterioration increases, the value of the alternating current leakage current also increases, in comparison with the variation law of the direct current leakage current. This means that the alarm threshold for the ac leakage current can be determined with reference to the reference value determined for the dc leakage current. As shown in fig. 3, the alarm threshold may be determined to be 57 μ a. It should be noted that the determination of the alarm threshold is based on experience and practical conditions, and is not limited to the specific value of the embodiment, for example, the alarm threshold may be selected from 55 to 60 μ a.
Table 2 shows the ac leakage current values of the surge protector for different degrees of degradation at three different ac operating voltages (176V, 220V and 264V). The inventor finds that the change rule of the alternating current leakage current is similar to that of the direct current leakage current, but the change range of the alternating current leakage current is obviously smaller than that of the direct current leakage current, and the resistance value of the SPD is sensitive to the voltage because the SPD is a nonlinear voltage dependent resistor. This results in different alarm thresholds being required for different ac operating voltages, namely an alarm threshold of 42 μ a for 176V operating voltage, 57 μ a for 220V operating voltage and 75 μ a for 264V operating voltage. In addition, the use of a single current reference value may also result in false detection or missed detection. For example, if the alarm threshold is selected to be 42 μ a, a new SPD at 264V operating voltage may also be considered as a severely degraded SPD causing false detection, or if the alarm threshold is selected to be 75 μ a, a severely degraded SPD at 176V operating voltage may also be considered as a normal SPD causing missed detection.
The single current reference value currently determined for the dc leakage current cannot be adapted to the ac leakage current. The respective alarm thresholds need to be determined for different ac operating voltages.
TABLE 2 leakage current values of surge protectors of different degradation degrees under different AC working voltages
In the present embodiment, the calculation function is calculated by using the principle of linear interpolation, and specifically, the calculation function expression is as follows (in the following description, as not explicitly stated, "operating voltage" refers specifically to ac operating voltage):
when U is turnedn≤U≤UmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnWhen the temperature of the water is higher than the set temperature,
wherein, U is the measured working voltage of the surge protector;
Ialarm(U)represents an alarm threshold at the operating voltage U;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminIndicating minimum of surge protectorOperating voltage, and Un、UmaxAnd UminAre all known constants;
In this embodiment, Un＝220V，Umax＝264V，Umin＝176V，
Alternatively, the above parameters may be changed according to the actual working conditions. The alarm threshold-operating voltage fitting curve shown in fig. 5 can be obtained from the calculation function expression.
Fig. 6 shows a comparison graph of the alarm threshold fitting curve shown in fig. 5 and leakage current curves of surge protectors with different degradation degrees, and it can be seen from fig. 6 that the alarm threshold calculated according to the fitting curve can better distinguish a normal SPD (a new SPD or a preliminarily degraded SPD) from a severely degraded SPD, and does not cause missing detection and false detection, and has better accuracy and reliability.
Therefore, the measured working voltage of the surge protector is substituted into the calculation function, and the alarm threshold value under the working voltage can be obtained. This step may be performed by the processing unit. Illustratively, the processing Unit may be a Micro Controller Unit (MCU), a Field Programmable Gate Array (FPGA), a digital signal processor, or other processing units commonly used in the art.
And further, comparing the measured alternating current leakage current with an alarm threshold, and sending an alarm signal to prompt a user to replace the SPD when the alternating current leakage current is greater than the alarm threshold. For example, the alarm signal may be an alarm sound, an alarm image displayed on the interactive interface, or an alarm prompt directly transmitted to the user terminal, but the embodiment of the present invention is not limited thereto, as long as the alarm signal can play an alarm role. And conversely, when the average value of the alternating current leakage current is less than or equal to the average value of the alarm threshold value, the real-time working voltage of the surge protector and the subsequent steps are repeatedly measured, namely the cycle is repeated.
According to a variant embodiment of the invention, the steps of the method comprise:
measuring the alternating current leakage current of the surge protector;
measuring the working temperature of the surge protector;
calculating an alarm threshold;
comparing the alternating current leakage current with the alarm threshold, sending an alarm signal when the alternating current leakage current is larger than the alarm threshold, and repeatedly measuring the working voltage of the surge protector and subsequent steps when the alternating current leakage current is smaller than or equal to the alarm threshold.
In the case of measuring the operating temperature, the calculation comprises a calculation by means of a calculation function, which represents the magnitude of the alarm threshold at a certain operating temperature.
For example, the calculation function is:
when T isn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when T ismin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
t is the measured working temperature of the surge protector;
Ialarm(T)represents an alarm threshold at the operating voltage T;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
Fig. 2 shows a flow chart of a method of monitoring ac leakage current of a surge protector according to another embodiment of the invention. In this embodiment, the method includes the steps of:
measuring the alternating current leakage current of the surge protector;
measuring the real-time working voltage of the surge protector;
calculating an alarm threshold value under the current working voltage;
taking an average value of alternating current leakage current and an average value of an alarm threshold value within a certain time;
and comparing the average value of the alternating current leakage current with the average value of the alarm threshold, sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold, and repeatedly measuring the real-time working voltage of the surge protector and subsequent steps when the average value of the alternating current leakage current is smaller than or equal to the average value of the alarm threshold.
The method described in this embodiment differs from the previous embodiment in that the average value of the ac leakage current over a certain time period and the average value of the alarm threshold are taken and used for comparison. Therefore, false detection or missing detection caused by single measurement error can be eliminated, and the accuracy and reliability are further improved. Alternatively, in a variant embodiment of the invention, the measurement of the real-time operating voltage of the surge protector may be changed to the measurement of the real-time operating temperature of the surge protector, with the remaining steps being modified accordingly.
Fig. 7 shows a flow chart of a method of monitoring ac leakage current of a surge protector according to a further embodiment of the invention. In this embodiment, the method includes the steps of:
measuring the alternating current leakage current of the surge protector;
measuring the real-time working voltage of the surge protector;
measuring the real-time working temperature of the surge protector;
calculating alarm threshold values under the current working voltage and the working temperature;
taking an average value of alternating current leakage current and an average value of an alarm threshold value within a certain time;
and comparing the average value of the alternating current leakage current with the average value of the alarm threshold, sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold, and repeatedly measuring the real-time working voltage of the surge protector and subsequent steps when the average value of the alternating current leakage current is smaller than or equal to the average value of the alarm threshold.
The method described in this embodiment is different from the previous embodiment in that two variables (operating voltage and operating temperature) are measured simultaneously, and a fitting matrix is required to calculate the linear fit of the alarm threshold. Specifically, the calculation function is:
when U is turnedn≤U≤UmaxAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedn≤U≤UmaxAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
u is the measured working voltage of the surge protector, and T is the measured working temperature of the surge protector;
Ialarm(U，T)represents the alarm threshold at the operating voltage U and the operating temperature T;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminRepresents the minimum operating voltage of the surge protector, and Un、UmaxAnd UminAre all known constants;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
FIG. 8 illustrates an alarm threshold-operating voltage operating temperature relationship curve according to the embodiment shown in FIG. 7. U can be determined according to actual conditionsn、Umax、Umin、Tn、TmaxAnd Tmin. E.g. Un＝220V，Umax＝264V，Umin＝176V，Tn＝25℃，Tmax＝70℃，Tmin-25 ℃ and calculated from experimental data
And
the value of (c). Therefore, the alarm threshold-working voltage working temperature relation curved surface shown in the figure 8 can be obtained according to the calculation function expression.
Therefore, the measured real-time working voltage and real-time working temperature of the surge protector are substituted into the calculation function, and the alarm threshold value under the working voltage and the working temperature can be obtained. And taking the average value of the alternating leakage current in a certain time and the average value of the alarm threshold value.
Further, the average value of the alternating current leakage current is compared with the average value of the alarm threshold value, and when the average value of the alternating current leakage current is larger than the average value of the alarm threshold value, an alarm signal is sent out. And conversely, when the average value of the alternating current leakage current is less than or equal to the average value of the alarm threshold value, the real-time working voltage of the surge protector and the subsequent steps are repeatedly measured, namely the cycle is repeated.
Alternatively, the step of measuring the operating voltage may be interchanged with the step of measuring the operating temperature in order, or both steps may be performed simultaneously.
Alternatively, a variation of this embodiment may also refer to the way of the embodiment shown in fig. 1, i.e. comparing the ac leakage current with an alarm threshold instead of an average value thereof.
Optionally, in other variations of this embodiment, the calculating includes performing bilinear interpolation calculation through an alarm threshold list stored in the processing unit and including alarm threshold magnitude values at a certain operating voltage and operating temperature. Table 3 illustratively shows a list of alarm thresholds, with only a portion of the data listed due to space limitations.
TABLE 3 alarm threshold List
For example, for a measured operating voltage U of the surge protector and a measured operating temperature T of the surge protector, four groups of voltages and temperatures closest to the operating voltage U and the operating temperature T are selected in table 3, and are denoted as (U) below1,T1)、(U1,T2)、(U2,T1)、(U2,T2) And obtaining corresponding alarm threshold value
According to bilinear interpolation, alarm threshold Ialarm(U,T)The calculation formula of (a) is as follows:
therefore, the alarm threshold I under the working voltage U and the working temperature T can be calculatedalarm(U,T)。
In summary, the method provided by the embodiment of the present invention can dynamically determine the alarm threshold of the ac leakage current, and the threshold dynamically changes with the working voltage and/or the working temperature, so that a suitable alarm threshold can be determined according to different ac working voltages and/or working temperatures, and the method is low in use and maintenance cost, high in detection accuracy and reliability, and suitable for real-time online monitoring.
An embodiment of the present invention provides a device for monitoring ac leakage current of a surge protector, the device comprising: the current measuring module is used for measuring the alternating current leakage current of the surge protector; the device comprises a voltage measuring module and/or a temperature measuring module, wherein the voltage measuring module measures the working voltage of the surge protector, and the temperature measuring module measures the working temperature of the surge protector; and the processing unit is configured to calculate an alarm threshold value under the working voltage and/or the working temperature based on the measured working voltage and/or the working temperature, compare the alternating current leakage current with the alarm threshold value, send an alarm signal when the alternating current leakage current is larger than the alarm threshold value, and/or compare an average value of the alternating current leakage current with an average value of the alarm threshold value, and send an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold value.
The processing unit is exemplarily configured to perform the calculation by means of a calculation function representing the magnitude of the alarm threshold at a certain operating voltage and/or operating temperature. The expression and the calculation method of the calculation function may refer to the related description in the foregoing method embodiments, and are not described herein again.
Illustratively, in case the apparatus comprises a voltage measurement module and a temperature measurement module, the processing unit is configured to perform a bilinear interpolation calculation by means of an alarm threshold list, which is stored in the processing unit and comprises alarm threshold magnitude values at a certain operating voltage and operating temperature. The alarm threshold list and the bilinear interpolation method may refer to the related description in the foregoing method embodiments, and are not described herein again.
The embodiment of the invention also provides a surge protector which comprises the device.
Illustratively, the device may be electrically coupled to the surge protector and the ac leakage current of the surge protection current may be monitored.
Illustratively, the apparatus is an intelligent accessory device (Smart SPD) for SPDs, and leakage currents of the SPDs can be remotely monitored.
The device for monitoring the alternating current leakage current of the surge protector and/or the surge protector comprising the device provided by the embodiment of the invention are particularly suitable for online monitoring of the surge protector, and the use and maintenance cost is low.
The above description is only an exemplary embodiment of the present invention, but the scope of the embodiments of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes, substitutions or combinations within the technical scope of the embodiments of the present invention or within the spirit of the embodiments of the present invention, and all such changes, substitutions or combinations are included in the scope of the embodiments of the present invention.
Claims (14)
1. A method of monitoring a surge protector ac leakage current, the method comprising:
measuring the alternating current leakage current of the surge protector;
measuring the working voltage and/or working temperature of the surge protector;
calculating an alarm threshold value under the working voltage and/or the working temperature based on the measured working voltage and/or the working temperature; and
comparing said AC leakage current with said alarm threshold, and issuing an alarm signal when said AC leakage current is greater than said alarm threshold, and/or
And comparing the average value of the alternating current leakage current with the average value of the alarm threshold, and sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold.
2. The method according to claim 1, wherein in case the operating voltage is measured, the calculating comprises calculating by a calculation function representing an alarm threshold magnitude at a certain operating voltage.
3. The method of claim 2, wherein the computational function is:
when U is turnedn≤U≤UmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
u is the measured working voltage of the surge protector;
Ialarm(U)represents an alarm threshold at the operating voltage U;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminRepresents the minimum operating voltage of the surge protector, and Un、UmaxAnd UminAre all known constants；
4. The method according to claim 1, wherein in case the operating temperature is measured, the calculating comprises calculating by a calculation function representing an alarm threshold magnitude at a certain operating temperature.
5. The method of claim 4, wherein the computational function is:
when T isn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when T ismin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
t is the measured working temperature of the surge protector;
Ialarm(T)represents an alarm threshold at the operating voltage T;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
6. The method of claim 1, wherein, in the case of measuring the operating voltage and the operating temperature, the calculating comprises calculating by a calculation function representing an alarm threshold magnitude at a certain operating temperature.
7. The method of claim 6, wherein the computational function is a fitting matrix of alarm thresholds with respect to operating voltage and operating temperature.
8. The method of claim 7, wherein the computational function is:
when U is turnedn≤U≤UmaxAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedn≤U≤UmaxAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tn≤T≤TmaxWhen the temperature of the water is higher than the set temperature,
when U is turnedmin≤U<UnAnd Tmin≤T<TnWhen the temperature of the water is higher than the set temperature,
wherein the content of the first and second substances,
u is the measured working voltage of the surge protector, and T is the measured working temperature of the surge protector;
Ialarm(U，T)represents the alarm threshold at the operating voltage U and the operating temperature T;
Unindicating the rated operating voltage, U, of the surge protectormaxIndicating the maximum operating voltage, U, of the surge protectorminRepresents the minimum operating voltage of the surge protector, and Un、UmaxAnd UminAre all known constants;
Tnindicating the rated operating temperature, T, of the surge protectormaxIndicating the maximum operating temperature, T, of the surge protectorminIndicates the minimum operating temperature of the surge protector, and Tn、TmaxAnd TminAre all known constants;
9. The method of claim 1, wherein in the case of measuring the operating voltage and the operating temperature, the calculating comprises bilinear interpolation calculating through an alarm threshold list, the alarm threshold list being stored in a processing unit and comprising alarm threshold magnitude values at a certain operating voltage and operating temperature.
10. The method according to any of claims 1-9, wherein said measuring the ac leakage current of the surge protector comprises measuring an effective value and/or a maximum value of the ac leakage current of the surge protector.
11. An apparatus for monitoring ac leakage current of a surge protector, comprising:
the current measuring module is used for measuring the alternating current leakage current of the surge protector;
the device comprises a voltage measuring module and/or a temperature measuring module, wherein the voltage measuring module measures the working voltage of the surge protector, and the temperature measuring module measures the working temperature of the surge protector; and
a processing unit configured to calculate an alarm threshold at the operating voltage and/or operating temperature based on the measured operating voltage and/or operating temperature, and configured to compare the alternating leakage current with the alarm threshold, to issue an alarm signal when the alternating leakage current is greater than the alarm threshold, and/or
And comparing the average value of the alternating current leakage current with the average value of the alarm threshold, and sending an alarm signal when the average value of the alternating current leakage current is larger than the average value of the alarm threshold.
12. The apparatus of claim 11, wherein the processing unit is configured to calculate by a calculation function representing an alarm threshold magnitude at a certain operating voltage and/or operating temperature.
13. The apparatus of claim 11, wherein, in the case where the apparatus includes a voltage measurement module and a temperature measurement module, the processing unit is configured to perform bilinear interpolation calculations through an alarm threshold list stored in the processing unit and including alarm threshold magnitude values at a certain operating voltage and operating temperature.
14. A surge protector comprising a device as claimed in any of claims 11 to 13.
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