Ground grid system multi-point grounding detection device and method

Abstract

The present application relates to a kind of ground net system multipoint grounding detection device and method.Ground net system multipoint grounding detection device includes variable frequency power supply, multiple current transformers connected with variable frequency power supply on input side, multiple current sensors respectively arranged on each ground wire and direct grounding end, multiple channel data acquisition card connected with each current sensor, and host computer connected with multiple channel data acquisition card and carrying out data analysis.Ground net system multipoint grounding detection method is: by current transformer, frequency a current signal is applied to corresponding ground wire;Current signal is detected, and preliminary data analysis is carried out;By current transformer, frequency b current signal is applied;Current signal is detected, and secondary data analysis is carried out to obtain secondary analysis result, confirm whether there is grounding between two ground wires.The present application has the advantages of strong anti-interference ability, high timeliness, no interference and damage to other equipment.

Description

Technical Field

[0001] This invention relates to grounding detection technology, specifically to a detection device and method for detecting whether a grounding grid system has multiple grounding points. Background Technology

[0002] Existing grounding detection methods for grounding grids include grounding resistance measurement methods for detecting short circuits to ground, grounding resistance measurement methods using megohmmeters, and measurement methods using voltage and current transformers and sensors. These methods apply an excitation pulse signal to the grounding loop under test, inducing a pulse potential E in the loop. Under the influence of potential E, a current I is generated in the loop. The sensor measures E and I, and the resistance of the loop under test can be obtained using the formula R = E / I, thereby determining the single-point short circuit to ground. In other words, existing technologies mostly involve directly or indirectly applying voltage to the grounding grid using current sensors, megohmmeters, etc., thereby generating current in the loop, calculating the loop resistance, and thus determining the grounding condition.

[0003] For a single-point grounded multi-grounding independent grounding grid system, the grounding wires can be divided into various types according to their function, such as working, diagnostic, measurement shielding, and protection, depending on their purpose. If a short circuit occurs in the middle of the independent grounding system or to ground during system operation, it can lead to a series of problems such as protection and measurement failure.

[0004] In complex environments such as factories, laboratories, and testing sites, numerous devices are connected to grounding networks with various functions and purposes. These grounding networks may contain voltage or current signals across multiple frequency bands. Conventional methods, such as simply applying voltage to the grounding network, are insufficient to directly assess the independence of the grounding networks and may even interfere with ongoing experiments and tests. Therefore, real-time testing of the grounding network is not possible in operational environments like laboratories, factories, and testing sites; in other words, real-time grounding network detection is impossible. Furthermore, current technologies can only detect short circuits to ground, not short circuits between different ground wires.

[0005] Therefore, it is particularly important to develop a method for detecting multiple grounding points in the grounding system, and to detect in real time whether multiple grounding points exist in the grounding system, so as to ensure the independence of the system's grounding grid. Summary of the Invention

[0006] The purpose of this invention is to provide a grounding detection device for a grounding grid system that can perform multi-point grounding detection (including short circuits to ground and short circuits between different ground wires) while ensuring independence.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A multi-point grounding detection device for a grounding grid system is provided for multi-point grounding detection of the grounding grid system. The grounding grid system includes n independent ground wires and direct grounding terminals connected to each of the ground wires, where n is 2, 3, or 4. The ground wires include at least two of the following: working ground wire, diagnostic ground wire, shielding ground wire, and protective ground wire. The multi-point grounding detection device includes a frequency converter capable of outputting voltage signals of different frequencies, n or n-1 current transformers connected to the input side of the frequency converter, n+1 current sensors respectively installed on each of the ground wires and the direct grounding terminals, a multi-channel data acquisition card connected to each of the current sensors, and a host computer connected to the multi-channel data acquisition card to perform data analysis to obtain the detection results. When the ground wire includes the protective ground wire, the multi-point grounding detection device of the grounding grid system includes n-1 current transformers, and the output side of each current transformer is connected to each of the ground wires except the protective ground wire; when the ground wire does not include the protective ground wire, the multi-point grounding detection device of the grounding grid system includes n current transformers, and the output side of each current transformer is connected to each of the ground wires.

[0008] The multi-point grounding detection device of the grounding grid system also includes n or n-1 switching devices that correspond one-to-one with the current transformer, and the switching devices are connected between the frequency converter and the current transformer.

[0009] The multi-point grounding detection device for the grounding grid system also includes a tester for detecting the current on the grounding wire.

[0010] The current transformer is a single-turn through-core current transformer.

[0011] The current sensor is a Hall current sensor.

[0012] This invention also provides a method for multi-point grounding detection of a grounding grid system, which can perform multi-point grounding detection (including short circuits to ground and short circuits between different ground wires) while ensuring independence. The method is as follows: A grounding detection method for a grounding grid system using the aforementioned multi-point grounding detection device includes the following steps: Step 1: Start the frequency converter, apply a current signal of frequency a to each of the corresponding ground wires through the current transformer, and then execute Step 2; Step 2: Detect the current signal at the corresponding position using each of the current sensors, and send the detected current signal to the host computer via the multi-channel data acquisition card for preliminary data analysis to obtain preliminary analysis results. If the preliminary analysis indicates that there is a grounding between the two ground wires, proceed to Step 3. Step 3: Start the frequency converter power supply. Based on the preliminary analysis, apply a current signal with frequency b to the current transformer corresponding to either of the two ground wires that are grounded (b ≠ a). Then proceed to step 4. Step 4: The current signal at the location corresponding to the current sensor of the two ground wires that are grounded is detected, and the detected current signal is sent to the host computer through the multi-channel data acquisition card for secondary data analysis to obtain the secondary analysis result, and to confirm whether there is a grounding between the two ground wires.

[0013] In step 2, if a current signal of frequency a is applied to each of the corresponding ground wires through all the current transformers and none of the current sensors detect a current signal, then the preliminary analysis result is that the grounding grid system has no multi-point grounding. If a current signal of frequency a is applied to the corresponding ground wire through any one of the current transformers, and the two current sensors detect the corresponding current signal, then the preliminary analysis result is that there is a grounding between the ground wires corresponding to the two current sensors that can detect the corresponding current signal.

[0014] In step 4, if, through preliminary analysis, it is determined that when a current transformer corresponding to either of the two ground wires that are grounded applies a current signal of frequency b, and the current sensor corresponding to the two ground wires detects the corresponding current signal, then it is confirmed that there is a grounding between the ground wires corresponding to the two current sensors that can detect the corresponding current signal.

[0015] The multi-point grounding detection method for the grounding grid system also includes: Step 5: For the two ground wires that are confirmed to be grounded, detect the current signal at different locations to determine the grounding location.

[0016] In the host computer, the current signal acquired by the multi-channel data acquisition card is subjected to FFT analysis to obtain the test current value, and data analysis is performed based on the test current value.

[0017] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: the present invention can perform real-time and effective grounding detection on a grounding grid system with multiple independent ground wires, and has the advantages of strong anti-interference ability, high timeliness, and no interference or damage to other equipment. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the multi-point grounding detection device for the grounding grid system of the present invention.

[0019] Appendix Figure 2 This is a schematic diagram of short-circuit detection between independent ground wires in the multi-point grounding detection method of the grounding grid system of the present invention.

[0020] Appendix Figure 3 This is a schematic diagram of short circuit detection between an independent ground wire and the earth in the multi-point grounding detection method of the grounding grid system of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0022] Example 1: As shown in the attached document Figure 1 As shown, a single-point grounding multi-grounding independent grounding network system includes n (n can be 2, 3, or 4) independent grounding wires and direct grounding terminals connected to each grounding wire. The grounding wires include at least two of the following: working ground, diagnostic ground, shielding ground, and protective ground. This embodiment includes all four types of grounding wires.

[0023] The multi-point grounding detection device for the aforementioned grounding grid system includes one (programmable) frequency converter, n or n-1 current transformers, n+1 current sensors, a multi-channel data acquisition card, and a host computer (the multi-channel data acquisition card and host computer are not shown in the diagram). The frequency converter can output voltage signals of different frequencies, and its input is connected to 220V AC mains power. The input side of the current transformer is connected to the frequency converter, and the output side is connected to the ground wires other than the protective ground wire. That is, when the ground wires include the protective ground wire, the multi-point grounding detection device includes n-1 current transformers, and the output side of each current transformer is connected to each ground wire except the protective ground wire; when the ground wires do not include the protective ground wire, the multi-point grounding detection device includes n current transformers, and the output side of each current transformer is connected to each ground wire. The current sensors are respectively installed on each ground wire and the direct grounding terminal to detect the current signal at their respective locations. The input side of the multi-channel data acquisition card is connected to each current sensor, and the output side is connected to a host computer. The host computer is used to perform data analysis to obtain the detection results. In this embodiment, the multi-point grounding detection device of the grounding grid system includes three current transformers T1~T3, which are respectively connected to the working ground wire, the diagnostic ground wire, and the shielding ground wire, and five current sensors CT1~CT5, which are respectively installed on each ground wire and the direct grounding terminal.

[0024] The multi-point grounding detection device for the grounding grid system also includes n or n-1 switching devices corresponding one-to-one with the current transformers. These switching devices are connected between the frequency converter and the current transformers. Therefore, this embodiment includes three switching devices QF1~QF3, respectively located between the frequency converter and the current transformer T1 on the working ground wire, between the frequency converter and the current transformer T2 on the diagnostic ground wire, and between the frequency converter and the current transformer T3 on the shield ground wire.

[0025] In the above scheme, the current transformer is a single-turn through-core current transformer, and the current sensor is a Hall current sensor.

[0026] Furthermore, the multi-point grounding detection device for the grounding grid system may also include a handheld tester for detecting the current on the ground wire.

[0027] The multi-point grounding detection method for a grounding grid system based on the above-mentioned multi-point grounding detection device includes the following steps: Step 1: Start the frequency converter power supply and apply a current signal of frequency a to each of the corresponding ground wires through the current transformer, and then proceed to step 2; Step 2: Detect the current signal at the corresponding position using each current sensor, and send the detected current signal to the host computer via a multi-channel data acquisition card for preliminary data analysis to obtain preliminary analysis results. If the preliminary analysis indicates that there is a grounding between the two ground wires, proceed to Step 3. Step 3: Start the frequency converter power supply. Based on the preliminary analysis, apply a current signal with frequency b to the current transformer corresponding to any one of the two ground wires that are grounded, where b ≠ a. Then proceed to step 4. Step 4: Detect the current signal at the location using current sensors corresponding to the two ground wires that are grounded. Send the detected current signal to the host computer via a multi-channel data acquisition card for secondary data analysis to obtain the secondary analysis results and confirm whether there is a grounding between the two ground wires.

[0028] In step 2, if a current signal of frequency a is applied to each of the corresponding ground wires through all current transformers and none of the current sensors detect a current signal, the preliminary analysis result is that the grounding grid system has no multi-point grounding; if a current signal of frequency a is applied to the corresponding ground wire through any one of the current transformers and two current sensors detect the corresponding current signal, the preliminary analysis result is that there is a grounding between the ground wires corresponding to the two current sensors that can detect the corresponding current signal.

[0029] In step 4, if, through preliminary analysis, a current transformer corresponding to any one of the two ground wires that are grounded is applied with a current signal of frequency b, and the current sensor corresponding to the two ground wires detects the corresponding current signal, then it is confirmed that there is a ground between the ground wires corresponding to the two current sensors that can detect the corresponding current signal.

[0030] A specific example of a detection method is as follows: Step 1: Start the frequency converter power supply and apply 400Hz current signals one by one through the current transformers T1~T3; Step 2: Detect the current signal at the corresponding location using each current sensor CT1~CT5. If none of the current sensors CT1~CT5 can detect a 400Hz current signal, the preliminary analysis result is that the grounding grid system has no multi-point grounding. Step 3: Start the frequency converter power supply and apply a 400Hz current signal to the corresponding ground wire through any one of the current transformers T1, T2 or T3; Step 4: Detect the current signal at the corresponding position using each current sensor CT1~CT5 and perform preliminary analysis, including the following cases: a) When a 400Hz current signal is applied through current transformer T1 and current transformers T2 and T3 are not working, if current sensors CT1 and CT2 detect a 400Hz current signal, but current sensors CT3~CT5 do not detect a 400Hz current signal, it is preliminarily determined that there is a grounding between the working ground wire and the diagnostic ground wire. b) When a 400Hz current signal is applied through current transformer T2 and current transformers T1 and T3 are not working, if current sensors CT2 and CT3 detect a 400Hz current signal, but current sensors CT1, CT4~CT5 do not detect a 400Hz current signal, it is preliminarily determined that there is a grounding between the diagnostic ground wire and the shield ground wire. c) When a 400Hz current signal is applied through current transformer T3 and current transformers T1 and T2 are not working, if current sensors CT3 and CT4 detect a 400Hz current signal, but current sensors CT1~CT2 and CT5 do not detect a 400Hz current signal, it is preliminarily determined that there is a grounding between the shield ground wire and the protective ground wire.

[0031] Step 5: Start the frequency converter power supply. Based on preliminary analysis, apply a 300Hz current signal to the current transformer corresponding to any one of the two ground wires that are grounded. This includes the following situations: a) Apply a 300Hz current signal through current transformer T1; b) Apply a 300Hz current signal through current transformer T2; c) Apply a 300Hz current signal through current transformer T3.

[0032] Step 6: Detect the current signal at the corresponding position using each current sensor CT1~CT5, and perform secondary analysis to confirm the detection results, including the following situations: a) When a 300Hz current signal is applied through the current transformer T1, if the current sensors CT1 and CT2 detect the 300Hz current signal, but the current sensors CT3~CT5 do not detect the 300Hz current signal, then it is confirmed that there is a grounding between the working ground wire and the diagnostic ground wire. b) When a 300Hz current signal is applied through the current transformer T2, if the current sensors CT2 and CT3 detect the 300Hz current signal, while the current sensors CT1, CT4~CT5 do not detect the 300Hz current signal, then it is confirmed that there is a grounding between the diagnostic ground wire and the shield ground wire. c) When a 300Hz current signal is applied through the current transformer T3, if the current sensors CT3 and CT4 detect the 300Hz current signal, while the current sensors CT1~CT2 and CT5 do not detect the 300Hz current signal, then it is confirmed that there is a grounding between the shield ground wire and the protective ground wire.

[0033] In the above scheme, current sensors CT1~CT5 only monitor currents at frequencies of 400Hz or 300Hz, eliminating other interference. Current sensors CT1~CT5 only recognize test signals emitted by current transformers T1~T3; they can measure the current signal from the grounding grid system itself, but do not process it. When current transformers T1~T3 are not outputting, if current sensors CT1~CT5 detect a signal, it must be generated by the grounding system. Theoretically, the equipment can perform corresponding identification based on the user's provided criteria.

[0034] Furthermore, after determining that a grounding has occurred between ground wires, the location of the grounding can also be detected. Therefore, the multi-point grounding detection method for the grounding grid system also includes: Step 5: For the two ground wires that are confirmed to be grounded, detect the current signal at different locations to determine the grounding location.

[0035] If two ground wires are confirmed to be grounded, and the grounding location is located after the corresponding current sensor (i.e., on the output side of the current transformer), the current will flow through the two corresponding current sensors. As long as the current values ​​measured by the two current sensors are equal, the grounding location between the two ground wires can be determined.

[0036] For example, as shown in the appendix Figure 2 As shown, assuming there are two or more groundings through the protective grounding wire in the working ground, current sensors CT1 and CT4 should be placed as close as possible to the current transformer T1. Since multiple groundings occur within the test hall, the test current emitted from the current transformer T1 will return via current sensor CT4. If the test current values ​​measured by current sensors CT1 and CT4 are equal, it can be determined that there is an external working branch grounded through a protective branch.

[0037] A handheld tester can be used to measure the test current at D1. If no test current can be measured at D2, it can be determined that there is no working branch grounding point after D2 via the protection branch. This allows us to determine the grounding location.

[0038] As attached Figure 3 As shown, assuming there are two or more direct groundings in the working ground, the current sensor CT1 should be as close as possible to the current transformer T1. Since multiple groundings occur within the test hall, the test current emitted from the current transformer T1 will return via the current sensor CT5. If the test current values ​​measured by current sensors CT1 and CT5 are equal, it can be determined that there is an external direct grounding. If a handheld tester can measure the test current at point D1 but not at point D2, it can be determined that there is no direct grounding point after D2.

[0039] The first stage of the above solution can detect whether a ground fault exists on a specific ground wire or whether there is a short circuit between ground wires. The second stage uses a portable handheld tester, which, if a ground wire fault is confirmed, allows for manual movement of the handheld device to locate the fault point. Fault current is identified by changing the frequency of the signal generator and analyzing the fault current at multiple frequency points to determine whether it is a fault current or current generated by the ground wire user. Specific testing steps can be designed and adjusted according to the requirements of the site environment.

[0040] The output of the programmable frequency converter couples the detection voltage signal to the ground wire via current transformers T1-T3, converting it into an energy signal with low voltage and high current characteristics. This frequency converter is an independent device. By using a selector switch to cyclically load energy, the detection signal is applied to the primary windings of the three current transformers T1-T3 at a time. Hall current sensors CT1-CT5 detect the presence of a current signal of the corresponding frequency in the circuit in real time. By changing the signal frequency multiple times, the system performs further discrimination to ultimately determine whether there are multiple grounding points in the ground wire circuit.

[0041] The secondary sides of Hall current sensors CT1~CT5 are connected to a multi-channel NI high-speed analog signal acquisition card. The industrial control computer software performs FFT analysis to obtain the test current value. For example, a 400Hz test current is actually the 8th harmonic (with the power frequency as the fundamental frequency). When the first test current is acquired by CT1~CT5, to prevent misjudgment, T1~T3 will emit a second test current with a frequency of 300Hz. Similarly, if the 6th harmonic current value obtained through FFT analysis is equal to the emitted test current value, it can be basically determined that there is a multi-point grounding.

[0042] This solution employs a high-stability programmable frequency converter power supply to boost the current to the grounding grid system via a single-turn through-core current transformer during testing. Using a programmable frequency converter power supply isolates the power grid from the influence of the testing power supply, providing a pure sine wave output that ensures the equivalence of the test results. It also includes overvoltage, overcurrent, and overheat protection functions. The through-core current transformer, with a maximum output voltage of 5V and a maximum output current of 10A, minimizes interference and potential damage to the grounding grid and other equipment within the system without altering the grounding wire connections themselves. High-precision Hall effect sensors monitor the current changes of each ground wire in real time, ensuring the frequency response of the grounding grid system's current sampling and further monitoring and analyzing the independence of the grounding grid system. A multi-channel input, high sampling rate, multi-bit synchronous sampling, and multi-functional PCI are used. The Express data acquisition card ensures the accuracy of the monitored waveforms and can detect high-frequency signals at the MHz level in the grounding grid system, providing data for subsequent analysis. In the host computer, the current signals acquired by the multi-channel data acquisition card are subjected to FFT analysis to obtain the test current value, and data analysis is performed based on the test current value. That is, a multi-band detection method is used, with a detection frequency range of 50~400Hz. The current waveform acquired by the Hall sensor is subjected to FFT analysis by the host computer software. According to the different frequencies of the output signal of the frequency converter, the acquired signal is digitally filtered by a narrow bandwidth bandpass filter and the current value at the corresponding frequency is analyzed to determine the independence of the grounding grid system. It has extremely strong anti-interference ability.

[0043] In non-testing conditions, the host computer can monitor the grounding grid system data in real time. Through professional software, it can analyze and process the current status of the grounding grid system, thereby further analyzing changes in the experimental environment.

[0044] The advantages of this solution are: it enables real-time and effective detection, monitoring, and identification of grounding conditions in complex environments such as factories, laboratories, and testing sites, where numerous devices are connected to grounding networks with various functions and purposes, and where these grounding networks may contain voltage or current signals across multiple frequency bands. It can detect grounding conditions between, but not limited to, working ground, diagnostic ground, protective ground, shielding ground, and earth ground, in pairs or multiple locations. It also boasts strong anti-interference capabilities and high timeliness.

[0045] This detection solution will not interfere with or damage other devices connected to the grounding network system. It can perform real-time detection and monitoring and can be used in various complex environments. Abnormal current and voltage signals generated by devices in the grounding network system, including ultra-high frequency signals, will not affect the detection system. Furthermore, it can record and save abnormal signals for analysis using specialized software.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A grounding detection method for a grounding grid system using a multi-point grounding detection device, wherein the grounding grid system includes n independent ground wires and direct grounding terminals connected to each of the ground wires, wherein n is 2, 3 or 4, and the ground wires include at least two of the following: working ground wire, diagnostic ground wire, shielding ground wire, and protective ground wire; The grounding detection device for the grounding system includes a frequency converter power supply capable of outputting voltage signals of different frequencies, n or n-1 current transformers connected to the frequency converter power supply on the input side, n+1 current sensors respectively installed on each of the ground wires and the direct grounding terminal, a multi-channel data acquisition card connected to each of the current sensors, and a host computer connected to the multi-channel data acquisition card to perform data analysis to obtain the detection results. When the ground wire includes the protective ground wire, the multi-point grounding detection device of the grounding grid system includes n-1 current transformers, and the output side of each current transformer is connected to each of the ground wires except the protective ground wire; when the ground wire does not include the protective ground wire, the multi-point grounding detection device of the grounding grid system includes n current transformers, and the output side of each current transformer is connected to each of the ground wires. Its features are: The multi-point grounding detection method for the grounding grid system includes the following steps: Step 1: Start the frequency converter, apply a current signal of frequency a to each of the corresponding ground wires through the current transformer, and then execute Step 2; Step 2: Detect the current signal at the corresponding position using each of the current sensors, and send the detected current signal to the host computer via the multi-channel data acquisition card for preliminary data analysis to obtain preliminary analysis results. If the preliminary analysis indicates that there is a grounding between the two ground wires, proceed to Step 3. Step 3: Start the frequency converter power supply. Based on the preliminary analysis, apply a current signal with frequency b to the current transformer corresponding to either of the two ground wires that are grounded (b ≠ a). Then proceed to step 4. Step 4: The current signal at the location corresponding to the current sensor of the two ground wires that are grounded is detected, and the detected current signal is sent to the host computer through the multi-channel data acquisition card for secondary data analysis to obtain the secondary analysis result, and to confirm whether there is a grounding between the two ground wires.

2. The method of claim 1, wherein: In step 2, if a current signal of frequency a is applied to each of the corresponding ground wires through all the current transformers and none of the current sensors detect a current signal, then the preliminary analysis result is that the grounding grid system has no multi-point grounding. If a current signal of frequency a is applied to the corresponding ground wire through any one of the current transformers, and the two current sensors detect the corresponding current signal, then the preliminary analysis result is that there is a grounding between the ground wires corresponding to the two current sensors that can detect the corresponding current signal.

3. The method of claim 2, wherein: In step 4, if any one of the two ground wires between which the ground exists is determined to apply a current signal with a frequency of b to the corresponding current transformer through preliminary analysis, and the corresponding current sensor of the two ground wires detects the corresponding current signal, it is determined that the ground exists between the two ground wires corresponding to the two current sensors that can detect the corresponding current signal.

4. The method of claim 3, wherein: The multi-point grounding detection method of the grounding grid system further comprises: Step 5: For the two ground wires between which the ground exists, the current signal is detected at different positions to determine the grounding position.

5. The method of claim 1, wherein: In the upper computer, the test current value is obtained by performing FFT analysis on the current signal collected by the multi-channel data acquisition card, and data analysis is performed based on the test current value.

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