Residual current protection method and residual current protection electric appliance
By performing frequency component analysis on the residual current, the problem of non-operation or false operation in the existing technology is solved, and the safety and reliability of residual current protection are improved.
Patent Information
- Application Number
- CN202511120162.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-12
- Publication Date
- 2025-11-18
AI Technical Summary
Existing Type B residual current operated circuit breakers cannot accurately distinguish between electric shock and electrical fire when faced with complex waveform currents, resulting in failure to operate or false operation, which reduces the safety and reliability of residual current protection.
By sampling the residual current in the line, signal components in different frequency ranges (0~400Hz, 0~1kHz, 0~20kHz) are extracted, and the type of residual current is determined based on the differences between the signal components. The corresponding setting current value is selected for protection, thus differentiating between electric shock and electrical fire.
It improves the safety and reliability of residual current protection, reduces the probability of failure to operate and false operation, and achieves precise protection of residual current at different frequencies.
Smart Images
Figure CN120978628A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a residual current protection method, belonging to the field of low-voltage electrical appliance technology. Background Technology
[0002] Installing residual current devices (RCDs) in low-voltage power distribution systems is an effective measure to prevent electric shock accidents and a technical measure to prevent electrical fires and equipment damage caused by residual current. With the development of power electronics technology, the application of equipment such as frequency converters, inverters, and UPS is becoming increasingly widespread. The residual current generated when these devices experience leakage faults is no longer just a sinusoidal current at the power frequency, but includes high-frequency AC current, pulsating DC current, and even smooth DC current. When the residual current contains complex waveform current components, traditional AC-type and A-type residual current protection devices suffer from reduced sensitivity or even fail to operate because the residual current transformer cannot accurately sense the residual current signal. In such cases, it is necessary to replace them with full-current residual current protection devices sensitive to both AC and DC currents, i.e., B-type or B+-type residual current circuit breakers.
[0003] According to the relevant specifications, in addition to ensuring tripping like AC and A type circuit breakers, Type B residual current operated circuit breakers also need to ensure tripping when induced by the following currents: sinusoidal AC residual current of 1kHz and below; AC residual current superimposed with smoothed DC current; pulsating DC residual current superimposed with smoothed DC residual current. In addition to ensuring tripping like AC and A type circuit breakers, Type B+ residual current operated circuit breakers also need to ensure tripping when induced by the following currents: sinusoidal AC residual current of 20kHz and below; AC residual current superimposed with smoothed DC current; pulsating DC residual current superimposed with smoothed DC residual current.
[0004] Based on current usage requirements, the protection range of residual current circuit breakers is generally 30mA for personal injury protection and 300mA for electrical fire protection.
[0005] Existing Type B residual current circuit breakers have two approaches for handling sinusoidal AC residual currents with frequencies greater than 1kHz: one approach uses filtering to remove high-frequency residual current components greater than 1kHz before calculating the fault residual current. This results in the residual current circuit breaker failing to trip when the high-frequency residual current component exceeds 300mA, potentially causing an electrical fire due to the high-frequency residual current. The other approach collects all residual current signals regardless of frequency and calculates the fault residual current accordingly, which can lead to malfunctions when the high-frequency residual current in the line increases. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a residual current protection method. By sampling different frequency components of the residual current, it can achieve differentiated protection against electric shock and electrical fire, reduce the probability of failure to operate or false operation, and improve the safety and reliability of residual current protection.
[0007] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:
[0008] A residual current protection method includes the following steps:
[0009] S1. Sample the residual current in the line to obtain the residual current sampling signal;
[0010] S2. Extract the signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz.
[0011] S3. Calculate the corresponding residual currents I1, I2, and I3 based on the three signal components respectively; and determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the corresponding setting current value for protection:
[0012] Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. △ The preset current threshold is used;
[0013] Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
[0014] Preferably, three low-pass filters with cutoff frequencies of 400Hz, 1kHz, and 20kHz are used to extract signal components in three different frequency ranges from the residual current signal.
[0015] Preferably, I △ = (75% ~ 100%)I △ n, I △ n = 30mA.
[0016] Based on the same inventive concept, the following technical solutions can also be obtained:
[0017] A residual current protection device, comprising:
[0018] The residual current sampling unit is used to sample the residual current in the line to obtain the residual current sampling signal;
[0019] The frequency selection unit is used to extract signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz.
[0020] The residual current control unit is used to calculate the corresponding residual currents I1, I2, and I3 based on the three signal components; and to determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the appropriate setting current value for protection.
[0021] Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. △ The preset current threshold is used;
[0022] Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
[0023] Preferably, the frequency selection unit uses three low-pass filters with cutoff frequencies of 400Hz, 1kHz, and 20kHz to extract signal components from the residual current signal in three different frequency ranges.
[0024] Preferably, I △ = (75% ~ 100%)I △ n, I △ n = 30mA.
[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0026] This invention classifies and identifies the frequency distribution of residual current by simultaneously acquiring and comparing multiple components of different frequency ranges in the residual current sampling signal. Based on the different effects of residual current at different frequencies on electric shock and electrical fires, different setting current values are used to differentiate protection against electric shock and electrical fires, significantly reducing the probability of failure to operate and false operation, and greatly improving the safety and reliability of residual current protection. Attached Figure Description
[0027] Figure 1 This is a structural block diagram of a specific embodiment of the residual current protection device of the present invention;
[0028] Figure 2 This is a schematic diagram of the specific structure of the frequency selection unit;
[0029] Figure 3 This is a specific implementation circuit diagram of a frequency selection unit;
[0030] Figure 4 A schematic diagram illustrating the workflow for residual current protection in a residual current control unit. Detailed Implementation
[0031] To address the shortcomings of existing technologies, the present invention addresses this issue by simultaneously acquiring and comparing multiple components with different frequency ranges in the residual current sampling signal to classify and identify the frequency distribution of the residual current. Based on the different impacts of residual current at different frequencies on electric shock and electrical fires, different setting current values are used to differentiate protection against electric shock and electrical fires, thereby reducing the probability of failure to operate and false operation, and improving the safety and reliability of residual current protection.
[0032] The residual current setting for personal electric shock protection is generally 30mA. This setting is for fault residual current frequencies between 0 and 100Hz. For fault residual current frequencies between 100 and 1kHz, the setting can be gradually increased. At 1kHz, the protection setting is generally no more than 300mA, meaning the hazardous value of a 1kHz high-frequency residual current is 300mA. For ultra-high-frequency residual currents exceeding 20kHz, even if the value exceeds 300mA, it will not pose a danger to the human body.
[0033] The setting value for electrical fire protection is generally 300mA. Regardless of the frequency of the residual fault current, even if it exceeds 20kHz, an electrical fire can still occur when the residual fault current exceeds 300mA.
[0034] Conventional Type B residual current circuit breakers can detect sinusoidal residual currents of 1kHz and below, but cannot provide proper protection for sinusoidal residual currents exceeding 1kHz. As a result, when the ultra-high frequency residual current is greater than 300mA, the detected current value is too low, leading to failure to trip and potentially causing an electrical fire.
[0035] Conventional Type B residual current circuit breakers are used in complex waveform applications and employ fixed setting values. If the setting value is too low (e.g., 30mA), they are prone to malfunction, while if the setting value is too high (e.g., 300mA), they cannot provide personal protection.
[0036] The residual fault current in the line is a composite wave composed of multiple different frequencies, including AC residual fault current of 400Hz; residual fault current containing high-frequency components within 1kHz; and residual fault current containing high-frequency components within 20kHz.
[0037] Based on the above analysis, the present invention proposes the following technical solution:
[0038] A residual current protection method includes the following steps:
[0039] S1. Sample the residual current in the line to obtain the residual current sampling signal;
[0040] S2. Extract the signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz.
[0041] S3. Calculate the corresponding residual currents I1, I2, and I3 based on the three signal components respectively; and determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the corresponding setting current value for protection:
[0042] Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. △ The preset current threshold is used;
[0043] Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
[0044] Wherein, the current threshold I △ The preferred value range is (75% to 100%). △ n, I △ n = 30mA.
[0045] A residual current protection device, comprising:
[0046] The residual current sampling unit is used to sample the residual current in the line to obtain the residual current sampling signal;
[0047] The frequency selection unit is used to extract signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz.
[0048] The residual current control unit is used to calculate the corresponding residual currents I1, I2, and I3 based on the three signal components; and to determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the appropriate setting current value for protection.
[0049] Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. △ The preset current threshold is used;
[0050] Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
[0051] Wherein, the current threshold I △The preferred value range is (75% to 100%). △ n, I △ n = 30mA.
[0052] To facilitate public understanding, the technical solution of the present invention will be described in detail below through a specific embodiment and in conjunction with the accompanying drawings:
[0053] The residual current protection device in this embodiment has the following structure: Figure 1 As shown, the circuit includes: a circuit breaker unit, a residual current transformer, a power supply circuit, a residual current sampling unit, a residual current control unit, a residual current tripping unit, and a frequency selection unit. The residual current transformer is installed inside the circuit breaker unit and collects the residual current in the three-phase lines. This weak current signal is sampled and amplified by the residual current sampling unit and then sent to the frequency selection unit. The frequency selection unit processes the sampled voltage signal input from the residual current sampling unit, extracting the 0-400Hz, 0-1kHz, and 0-20kHz signal components, which are then sent to the residual current control unit for further processing to determine the fault residual current. Based on the corresponding residual current setting value, the control unit determines whether the residual current-operated circuit breaker should operate and sends an operation signal to the residual current tripping unit, driving the actuator to make the circuit breaker operate instantaneously or with a delay. The power supply circuit provides power to the above circuits.
[0054] like Figure 2 As shown, the frequency selection unit includes a 400Hz frequency selection unit, a 1kHz frequency selection unit, and a 20kHz frequency selection unit, used to extract the signal components of 0-400Hz, 0-1kHz, and 0-20kHz from the residual current sampling signal, respectively. The output terminals of the 400Hz, 1kHz, and 20kHz frequency selection units are respectively connected to the three AD ports of the MCU in the residual current control unit. A specific implementation circuit of the frequency selection unit in this embodiment is shown below. Figure 3As shown, the 400Hz frequency selection unit is a low-pass filter circuit composed of resistors R1-R3, capacitor C1, and operational amplifier N1A, with a cutoff frequency of 400Hz. It can remove high-frequency voltage signal components above 400Hz from the input of the residual current sampling unit, and input the voltage signal after removing the high-frequency voltage signal components into the MCU of the residual current control unit. The 1kHz frequency selection unit is a low-pass filter circuit composed of resistors R4-R6, capacitor C2, and operational amplifier N1B, with a cutoff frequency of 1kHz. It can remove high-frequency voltage signal components above 1kHz from the input of the residual current sampling unit, and input the voltage signal after removing the high-frequency voltage signal components into the MCU of the residual current control unit. The 20kHz frequency selection unit is a low-pass filter circuit composed of resistors R7-R9, capacitor C3, and operational amplifier N1C, with a cutoff frequency of 20kHz. It can remove high-frequency voltage signal components above 20kHz from the input of the residual current sampling unit, and input the voltage signal after removing the high-frequency voltage signal components into the MCU of the residual current control unit.
[0055] like Figure 4 As shown, the residual current control unit first receives different residual current sampling signals input from the frequency selection unit and calculates the corresponding residual current respectively. The residual current calculated from the residual current sampling signal input from the 400Hz frequency selection unit after filtering out frequency components above 400Hz is I1; the residual current calculated from the residual current sampling signal input from the 1kHz frequency selection unit after filtering out frequency components above 1kHz is I2; and the residual current calculated from the residual current sampling signal input from the 20kHz frequency selection unit after filtering out frequency components above 20kHz is I3. Then, it determines whether the deviation between I1 and I2 is within a first preset range (in this embodiment, it determines whether the value of I2-I1 is less than 20% of I2) or whether I1 ≥ I2. △ , where I △ = (75% ~ 100%)I △ n, I △ If n = 30mA, then the residual current type in the line is determined to be sinusoidal AC residual current. I1 is used as the fault residual current I0 for output display, and the set current value I is set to... △ n is assigned a value of 30mA for protection; otherwise, it is then determined whether the deviation between I2 and I3 is within the second preset range (in this embodiment, it is determined whether the value of I3-I2 is less than 20% of I3). If so, the residual current type in the line is determined to be high-frequency AC residual current, and I2 is used as the fault residual current I0 for output display, and the set current value I is set to... △ n is assigned a value of 300mA for protection; otherwise, the residual current type in the line is determined to be UHF AC residual current, and I3 is used as the fault residual current I0 for output display, and the set current value I is set to... △n is assigned a value of 300mA for protection.
[0056] In the above embodiments, the type of residual current in the line and the fault residual current I0 are determined based on the differences between I1, I2, and I3. In practice, it can also be determined based on the differences between the filtered residual current sampling signals output by the 400Hz frequency selection unit, the 1kHz frequency selection unit, and the 20kHz frequency selection unit. The judgment process is similar to the above process; it is only necessary to... Figure 4 In the judgment process, I1, I2, and I3 can be replaced with the corresponding filtered residual current sampling signals (i.e., the first to third signal components in the residual current sampling signals output by the residual current sampling unit), which will not be elaborated here.
Claims
1. A residual current protection method, characterized in that, Includes the following steps: S1. Sample the residual current in the line to obtain the residual current sampling signal; S2. Extract the signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz. S3. Calculate the corresponding residual currents I1, I2, and I3 based on the three signal components respectively; and determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the corresponding setting current value for protection: Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. I △ The preset current threshold is used; Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
2. The residual current protection method as described in claim 1, characterized in that, Three low-pass filters with cutoff frequencies of 400Hz, 1kHz, and 20kHz were used to extract signal components from the residual current signal in three different frequency ranges.
3. The residual current protection method as described in claim 1, characterized in that, I △ =(75%~100%)I △ n,I △ n=30mA。 4. A residual current protection device, characterized in that, include: The residual current sampling unit is used to sample the residual current in the line to obtain the residual current sampling signal; The frequency selection unit is used to extract signal components from the residual current sampling signal in three different frequency ranges: the first signal component from 0 to 400 Hz, the second signal component from 0 to 1 kHz, and the third signal component from 0 to 20 kHz. The residual current control unit is used to calculate the corresponding residual currents I1, I2, and I3 based on the three signal components; and to determine the type of residual current in the line and the fault residual current I0 based on the differences between the first and third signal components or the differences between I1, I2, and I3, and select the appropriate setting current value for protection. Determine whether the deviation between the first signal component and the second signal component, or the deviation between I1 and I2, is within a first preset range or whether I1 ≥ I2. △ If so, the residual current type in the line is determined to be sinusoidal AC residual current, and the fault residual current I0 = I1. A setting current value of 30mA is selected for protection. I △ The preset current threshold is used; Otherwise, it is then determined whether the deviation between the second signal component and the third signal component or the deviation between I2 and I3 is within the second preset range. If so, the residual current type in the line is determined to be high-frequency AC residual current, the fault residual current I0 = I2, and a setting current value of 300mA is selected for protection. If not, the residual current type in the line is determined to be ultra-high frequency AC residual current, the fault residual current I0 = I3, and a setting current value of 300mA is selected for protection.
5. The residual current protection device as described in claim 4, characterized in that, I △ =(75%~100%)I △ n,I △ n = 30mA.
6. The residual current protection device as described in claim 4, characterized in that, The frequency selection unit uses three low-pass filters with cutoff frequencies of 400Hz, 1kHz, and 20kHz to extract signal components from the residual current signal in three different frequency ranges.