Temperature measuring RTD grounding protection system and control method thereof

Abstract

The application relates to a temperature measuring RTD grounding protection system, a multi-path grounding execution matrix module comprising a plurality of electromagnetic relays connected to and controlled by a master control unit, each lead of the RTD being connected to a common end of a relay contact; the normally open end of the relay contact being used for connection to a grounding bus. A grounding state inspection module comprises a sampling resistor connected in series in each grounding loop, and a measurement circuit connected to the master control unit, the measurement circuit being connected to the sampling circuit and detecting an electrical parameter between the two ends of each sampling resistor; a safety interlocking interface module is connected to the master control unit. The control method of the temperature measuring RTD grounding protection system is based on the temperature measuring RTD grounding protection system. The temperature measuring RTD grounding protection system and the control method thereof provided by the application adopt a relay contact array driven by a master control unit, and each lead of each RTD is independently connected to a corresponding relay contact, thereby realizing centralized switching of the grounding states of all RTD leads and improving operation efficiency and reliability.

Description

Technical Field

[0001] This invention relates to the field of power equipment safety protection technology, and in particular to a temperature-measuring RTD grounding protection system and its control method. Background Technology

[0002] Dozens to hundreds of RTDs (Resistance Temperature Detectors) are typically embedded in the stator slots of a generator for online monitoring of the operating temperature of the stator core and windings. To ensure the reliability and redundancy of temperature measurement, each measuring point usually employs a dual-branch, three-wire RTD configuration, meaning each measuring point contains two independent RTD sensors, typically connected in a three-wire configuration with a total of six leads. During AC or DC withstand voltage tests on the stator windings, such as those performed before commissioning or after major overhauls, the test voltage can reach several kilovolts to tens of kilovolts. Since the operating voltage of the RTDs is usually in the volt range, to prevent high voltage from entering through the leads and damaging the delicate RTDs, all RTD leads must be reliably short-circuited and grounded before the test.

[0003] Currently, there are two main types of grounding methods commonly used:

[0004] The first method is the traditional manual wiring method, which uses fuses or jumper wires and manually shorts and tightens each lead on the terminal block before connecting it to the grounding terminal. For a generator with 100 double three-wire test points, 600 leads need to be handled, and the construction time can take several hours. Moreover, grounding problems are easily caused by factors such as personnel fatigue and loose jumper wire connections.

[0005] The second method uses a simple centralized grounding device, employing multi-core cables and aviation plugs to gather the dispersed RTD leads into a single plug. Collective grounding is achieved by plugging and unplugging this plug. While this method improves efficiency, it still has the following inherent drawbacks: it cannot confirm whether the plug is properly inserted or whether the internal contacts are making good contact, posing a risk of "false grounding." Furthermore, this method lacks a safety interlock mechanism; the grounding operation is completely independent of the high-voltage testing system, relying on personnel memory and procedures, posing a serious safety hazard of accidental voltage increases without proper grounding. Additionally, it lacks management and traceability; the operation process is not electronically recorded, hindering standardized management and post-event traceability analysis. Summary of the Invention

[0006] This invention addresses the technical problem in the prior art where equipment with a large number of buried temperature measuring RTDs suffers from low RTD grounding efficiency during withstand voltage tests, and is prone to voltage boosting tests under false grounding or ungrounded conditions, which can lead to serious safety accidents. The invention provides a temperature measuring RTD grounding protection system and its control method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A grounding protection system for a temperature measurement RTD includes: a main control unit, a multi-channel grounding execution matrix module, a grounding status inspection module, and a safety interlock interface module; The multi-path grounding execution matrix module includes multiple electromagnetic relays connected to and controlled by the main control unit. Each lead of the RTD is connected to the common terminal of a relay contact, and the multiple relay contacts are provided by at least one electromagnetic relay. The normally open terminals of the relay contacts are used to connect to the grounding bus. The grounding status inspection module includes a sampling resistor connected in series in each grounding loop, and a measurement circuit connected to the main control unit. The measurement circuit and the sampling circuit are connected to detect the electrical parameters across each sampling resistor. The main control unit is used to determine the grounding status of each grounding loop based on the electrical parameters. The safety interlock interface module is connected to the main control unit and is used to output a grounding ready signal, which is then used to connect to the control circuit of the withstand voltage test equipment.

[0008] Furthermore, the RTD is a three-wire RTD, which has three leads with different functions: the excitation current positive lead, the voltage detection positive lead, and the common circuit lead. Each RTD's three leads are connected to the common terminals of three independent electromagnetic relays, or to the three common terminals of a three-pole relay.

[0009] Furthermore, electromagnetic relays also have normally closed terminals; The normally closed terminals of the electromagnetic relays corresponding to the three leads of each RTD are respectively connected to the corresponding functional ports of the temperature measuring device. Specifically, the normally closed terminal corresponding to the excitation current positive lead is connected to the excitation current positive port of the temperature measuring device, the normally closed terminal corresponding to the voltage detection positive lead is connected to the voltage detection positive port of the temperature measuring device, and the normally closed terminal corresponding to the common circuit lead is connected to the common circuit port of the temperature measuring device. The common terminal of all electromagnetic relays is connected to the normally open terminal, which is used to short-circuit all leads of the RTD to the ground bus in the ground protection state.

[0010] Furthermore, the electromagnetic relay is a magnetically shielded electromagnetic relay; A magnetically shielded electromagnetic relay includes a shielding cover made of highly permeable magnetic material. The shielding cover encloses the coil and magnetic circuit of the electromagnetic relay, forming a magnetic shielding structure. The electromagnetic relay has a reinforced insulation structure between the coil and the contacts.

[0011] Furthermore, the measurement circuit of the grounding status inspection module includes a multiplexer, a constant current source, and an analog-to-digital converter; The sampling resistor is a four-wire precision sampling resistor. The four-wire precision sampling resistor has a pair of current terminals and a pair of voltage terminals. The pair of current terminals are connected in series in the grounding main circuit, and the pair of voltage terminals are connected to the main control unit through a multiplexer and an analog-to-digital converter. The sampling resistor uses the Kelvin connection method.

[0012] Furthermore, the multiplexing switch is connected to the main control unit and is used to sequentially connect the voltage terminal of each sampling resistor to the analog-to-digital converter; A constant current source is connected to a sampling resistor and a constant current is input to it; The analog-to-digital converter is used to measure the voltage across the sampling resistor; the main control unit is used to calculate the grounding resistance value based on the constant current and voltage value, and compare it with a preset threshold to determine the grounding status.

[0013] Furthermore, it also includes: a human-computer interaction unit; The human-machine interaction unit is connected to the main control unit. The human-machine interaction unit includes a touch screen and / or indicator panel, which is used to display the grounding status of all RTD channels in a graphical manner and provide an operation command input interface. The operation instructions include at least one of the following: one-key grounding instruction, one-key recovery instruction, and system self-test instruction.

[0014] Furthermore, it also includes: a communication interface module; The communication interface module is connected to the main control unit and is used to upload at least one of the system status information, alarm information and operation log to the upper monitoring system. The communication interface module supports at least one of the following communication protocols: RS485 / Modbus RTU protocol, Ethernet / Modbus TCP protocol, and IEC 61850 protocol.

[0015] Furthermore, it also includes: a system self-diagnosis module; The system self-diagnostic module is used to perform fault detection on at least one of the main control unit, the multi-channel grounding execution matrix module, the grounding status inspection module, and the communication interface module when the system is powered on or in response to a received self-test command, and output the diagnostic results.

[0016] Furthermore, the grounding ready signal output by the safety interlock interface module is a dry contact signal; The dry contact signal closes only when the grounding state inspection module determines that the grounding resistance of all channels is lower than the preset threshold; when the grounding resistance of any channel is higher than or equal to the preset threshold, the dry contact signal remains open.

[0017] Furthermore, it also includes: a sampling resistor lifetime assessment model, which includes: The first analysis module is used to collect the voltage values ​​of all connected sampling resistors in real time and store them temporarily; it presets the reference voltage value of the sampling resistor, iterates through the temporarily stored voltage values ​​of the sampling resistors and compares them one by one with the reference voltage value, and calculates the deviation of the voltage values ​​from the reference voltage value. The second analysis module stores the voltage value of the current sampling resistor if the deviation amplitude between the current sampling resistor voltage value and the reference voltage value is within the set range; otherwise, it discards the current sampling resistor voltage value if the deviation amplitude exceeds the set range. The third analysis module fits the voltage values ​​of the centrally stored sampling resistors in the coordinate system and generates a distribution curve. A dynamic update mechanism is adopted for the voltage values ​​of the centrally stored sampling resistors. That is, the number of voltage values ​​of the centrally stored sampling resistors is fixed, and a strategy of "adding the latest data and discarding the oldest data" is adopted to make the centrally stored data dynamically updated and always keep the number constant, thereby realizing the dynamic correction of the distribution curve. The fourth analysis module sets the normal distribution range of the sampling resistor voltage value and monitors the distribution curve in real time. If the data on the distribution curve reaches a set ratio that exceeds the normal distribution range of the sampling resistor voltage value, it indicates that the overall lifespan of the sampling resistor has reached the warning value.

[0018] This invention also provides a control method for a temperature-measuring RTD grounding protection system, applied to a temperature-measuring RTD grounding protection system, characterized by comprising the following steps: Step S1. Start the self-test program of the temperature measurement RTD grounding protection system and generate the self-test results; Step S2. Receive and respond to the grounding command, and the main control unit controls all electromagnetic relays of the multi-channel grounding execution matrix module to operate; connect the common terminal of all electromagnetic relays to the normally open terminal, and short-circuit all RTD leads to the grounding bus; Step S3. Start the grounding status inspection module, input a constant current into the sampling resistor in each grounding loop and measure the voltage across its two ends, and indirectly determine the resistance value through the voltage; detect the grounding resistance of each grounding loop one by one; and determine whether the grounding resistance of all channels is lower than the preset threshold. Step S4. When the grounding resistance of all channels is lower than the preset threshold, the grounding ready state is determined; a grounding ready signal is output through the safety interlock interface to allow the withstand voltage test equipment to increase the voltage; Step S5. During the withstand voltage test, continuously monitor the grounding status of each channel. If the grounding resistance of any channel is detected to be higher than or equal to the preset threshold, interrupt the grounding ready signal. Step S6. Receive and respond to the recovery command, control all electromagnetic relays to reset, connect the common terminal of all electromagnetic relays to the normally closed terminal, switch each lead of RTD back to the corresponding functional port of the temperature measuring device, restore the three-wire temperature measuring circuit, and generate an operation record.

[0019] Further, in step S1, the self-test procedure of the temperature-measuring RTD grounding protection system is initiated, including: The system detects at least one of the following: the working status of the main control unit; the driving circuits of each electromagnetic relay in the multi-channel grounding execution matrix module are normal; the measurement channels in the grounding status inspection module are normal; and the communication link of the communication interface module is normal.

[0020] Further, in step S2, a grounding command is received and responded to, and the main control unit controls the operation of all electromagnetic relays in the multi-path grounding execution matrix module, including: The main control unit drives each group of electromagnetic relays in a preset order, with the driving pulse width of each group of electromagnetic relays ranging from 30 milliseconds to 80 milliseconds.

[0021] Further, in step S3, by inputting a constant current into the sampling resistor in each grounding loop and measuring the voltage across it, the resistance value is indirectly determined by the voltage, including: A constant current is input to the current terminal of the currently detected sampling resistor through a constant current source; The voltage across the sampling resistor is measured using an analog-to-digital converter. The main control unit calculates the grounding resistance value based on the constant current and voltage values. The calculation formula is R = V / I, where R is the grounding resistance value, V is the voltage value, and I is the constant current value.

[0022] Furthermore, in step S3, the step of detecting the grounding resistance of each grounding loop includes: The main control unit controls the multi-channel selection switch to sequentially connect the voltage terminal of each sampling resistor to the analog-to-digital converter, thereby realizing the cyclic detection of multiple channels.

[0023] Further, in step S4, a grounding ready signal is output through the safety interlock interface, including: When the grounding ready state is determined, the main control unit controls the safety interlock interface module to close the dry contact to output a grounding ready signal; When the system is determined to be in a non-grounded ready state, the main control unit controls the safety interlock interface module to disconnect the dry contacts.

[0024] Furthermore, in step S5, during the withstand voltage test, the grounding status of each channel is continuously monitored, including: During the withstand voltage test, the grounding status inspection module is periodically activated at a preset frequency of 0.5Hz to 2Hz to detect the grounding resistance of all channels.

[0025] Furthermore, in step S5, the preset threshold for the grounding resistance is 10 milliohms.

[0026] Furthermore, in step S5, if the grounding resistance of any channel is detected to be higher than or equal to a preset threshold, after interrupting the grounding ready signal, the following steps are also performed: The communication interface module sends emergency interruption commands and abnormal channel information to the upper-level monitoring system.

[0027] Furthermore, in step S6, the generated operation record includes at least one of the following: operation time, operator identity information, grounding duration, and final state of each channel.

[0028] Furthermore, after generating the operation log, the following steps are performed: The operation records are stored in local memory and / or uploaded to the upper-level monitoring system via the communication interface module.

[0029] The grounding protection system and control method for a temperature measuring RTD provided by this invention have at least the following beneficial effects: The grounding protection system and control method for temperature measuring RTDs provided by this invention adopts a relay contact array driven by a main control unit, and each lead of each RTD is independently connected to the corresponding relay contact, realizing centralized switching of the grounding status of all RTD leads, shortening the tedious manual operation to an automatic operation in a short time, and improving the operation efficiency and reliability.

[0030] Furthermore, the normally closed terminals of the relay contacts corresponding to the three leads of each RTD are connected to the corresponding functional terminals of the temperature measuring device to ensure the integrity of the three-wire RTD measurement circuit and the normal operation of the lead resistance compensation mechanism in non-test conditions. Accurate temperature measurement can be automatically restored after the test.

[0031] Furthermore, it integrates a grounding status inspection module, which uses a four-wire Kelvin connection to periodically and accurately measure the continuity resistance of each grounding loop. It uses a constant current source to convert the resistance under test into an easily measurable voltage signal, achieving high-precision detection of milliohm-level grounding resistance and providing feedback on the results in a visual manner, thus eliminating the hidden dangers of ungrounded and false grounding.

[0032] Furthermore, by outputting a ground-ready hard-connect signal, the control circuit of the withstand voltage test equipment is forcibly connected in series, thus solving the possibility of accidental voltage increase from the technical source. The complete management process covers multiple procedures such as self-inspection, instruction execution, status verification, continuous monitoring, anomaly handling, and record generation, meeting the information needs of modern factories. Attached Figure Description

[0033] Figure 1 This is a block diagram of the overall structure of the temperature measurement RTD grounding protection system provided in an embodiment of the present invention; Figure 2 This is a control logic diagram of the grounding status inspection module of the multi-channel grounding execution matrix module provided in an embodiment of the present invention; Figure 3 This is a control logic diagram of the safety interlocking interface module provided in an embodiment of the present invention; Figure 4 The flowchart illustrates the control method for the temperature-measuring RTD grounding protection system provided in this embodiment of the invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be thorough and complete.

[0035] In this embodiment of the invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items.

[0036] The technical solution of the present invention will be described in detail below with specific embodiments. The same or similar concepts or processes may not be repeated in some embodiments.

[0037] Figure 1 This is an overall structural block diagram of a grounding protection system for a temperature-measuring RTD provided in an embodiment of the present invention. In this embodiment, a system with 600 RTD inputs is used as an example. It includes 100 dual three-wire measurement points, each containing two independent RTD sensors. Each sensor is three-wire, and a total of 600 leads need to be grounded.

[0038] like Figures 1-3As shown, the grounding protection system of the temperature measurement RTD includes a main control unit 1, a multi-channel grounding execution matrix module 2, a grounding status inspection module 3, a human-machine interface unit, a safety interlock interface module 4, a communication interface module, and a system self-diagnosis module. Among them: The multi-path grounding execution matrix module 2 includes multiple electromagnetic relays connected to and controlled by the main control unit 1. Each lead of the RTD is connected to the common terminal of a relay contact, and the multiple relay contacts are provided by at least one electromagnetic relay. The normally open terminals of the relay contacts are used to connect to the grounding bus.

[0039] The grounding status inspection module 3 includes a sampling resistor connected in series in each grounding loop, and a measurement circuit connected to the main control unit 1. The measurement circuit and the sampling circuit are connected to detect the electrical parameters across each sampling resistor. The main control unit 1 is used to determine the grounding status of each grounding loop based on the electrical parameters. The safety interlock interface module 4 is connected to the main control unit 1 and is used to output a grounding ready signal. The grounding ready signal is used to access the control circuit 5 of the withstand voltage test equipment.

[0040] The main control unit 1 is a PLC (Programmable Logic Controller), which serves as the system's control center, responsible for executing control logic, processing status signals, and managing the communication interfaces of each module. The main control unit 1 has embedded calculation and logic judgment functions, used for threshold comparison and status determination based on data collected by the grounding status inspection module 3. Alternatively, the main control unit 1 can be an industrial computer with a real-time operating system, connected to the relay matrix and detection circuit via expansion I / O boards.

[0041] See Figure 2 Taking the i-th RTD measurement point as an example, this measurement point contains two independent RTD sensors, namely RTD-i resistor one and RTD-i resistor two, each with a three-wire configuration. Each three-wire RTD has three leads with different functions, labeled A, B, and C. Among them, line A is the positive lead for the excitation current, labeled I+; line B is the positive lead for voltage detection, labeled V+; and line C is the common loop lead, serving as both the current loop I- and the voltage reference point V-.

[0042] Each lead of each RTD corresponds to a relay contact. Specifically, for the three leads A, B, and C of resistor one of RTD-i, they are connected to the common terminal COM of three independent electromagnetic relays K-i1-A, K-i1-B, and K-i1-C, respectively. Similarly, for the three leads A, B, and C of resistor two of RTD-i, they are connected to the common terminal of three independent electromagnetic relays K-i2-A, K-i2-B, and K-i2-C, respectively. A total of 6 independent electromagnetic relays are required for each measurement point.

[0043] In some feasible implementations, a three-pole relay can also be used, with one three-pole relay configured for each RTD. The three poles correspond to the three leads A, B, and C respectively. In this case, the relay contacts corresponding to the three leads of each RTD are provided by the three poles of one three-pole relay.

[0044] The embodiments of the present invention do not limit the specific implementation of the relay contacts, as long as each lead of each RTD can be independently controlled.

[0045] Each relay contact also has a normally closed terminal (NC) and a normally open terminal (NO). Under normal operating conditions, i.e., when the relay coil is de-energized, the common terminal is connected to the normally closed terminal. At this time, the normally closed terminal of relay K-i1-A corresponding to line A of RTD-i resistor 1 is connected to the excitation current positive terminal I+ of the temperature measuring device; the normally closed terminal of relay K-i1-B corresponding to line B is connected to the voltage detection positive terminal V+ of the temperature measuring device; and the normally closed terminal of relay K-i1-C corresponding to line C is connected to the common circuit terminal I- / V- of the temperature measuring device. This connection method ensures the integrity of the three-wire RTD measurement circuit: the constant current source inputs the excitation current through line A, and the current returns through line C after flowing through the RTD; the voltage detection circuit measures the voltage across the RTD through lines B and C. Since the input impedance of the voltage detection circuit is extremely high, typically greater than 10MΩ, the current on lines B and C is negligible, thus effectively eliminating the influence of lead resistance on the measurement results. If the three normally closed terminals are simply short-circuited and connected to the temperature measurement circuit, the above lead resistance compensation mechanism will be destroyed: the current input from the constant current source will be shunted through both line A and line B, and the same current will no longer flow through line B as through line A. The lead resistance compensation formula will fail, and the measurement result will contain unpredictable lead resistance errors, which may even damage the temperature measuring instrument.

[0046] In the grounding protection state, i.e., when the relay coil is energized, the common terminal is connected to the normally open terminal. The normally open terminals of all relay contacts are connected to the system ground bus GND. At this time, all leads of each RTD, including leads A, B, and C, are switched to the ground bus, achieving three-wire short-circuiting and reliable grounding.

[0047] In some feasible implementations, the electromagnetic relay providing the relay contacts is a magnetically shielded electromagnetic relay with a shielding cover made of a high-permeability material, such as permalloy. The shielding cover encloses the coil and magnetic circuit of the electromagnetic relay, forming a closed magnetic shielding structure to prevent external strong magnetic fields from interfering with the normal operation of the relay; for example, it is used to shield the strong magnetic field generated during generator operation. Simultaneously, a reinforced insulation structure is provided between the coil and contacts of the electromagnetic relay, such as adding insulating partitions or using high-voltage resistant insulating materials, to enable it to withstand high-voltage testing environments.

[0048] See Figure 2 The grounding status inspection module 3 includes a multi-channel selector switch, a four-wire precision sampling resistor network, a constant current source, and a 24-bit analog-to-digital converter.

[0049] Each grounding loop includes a 10mΩ four-wire precision sampling resistor connected in series. Taking the A-line loop of the i-th RTD measurement point as an example, the sampling resistor Rs-i1-A is connected in series between the normally open terminal of the relay K-i1-A and the system ground bus GND. This sampling resistor uses a four-wire Kelvin connection and has a pair of current terminals I+ and I- and a pair of voltage terminals V+ and V-. The current terminal I+ is connected to the normally open terminal of the relay K-i1-A, and the current terminal I- is connected to the system ground bus GND, forming the main grounding loop. The voltage terminals V+ and V- are connected to the two input terminals of the multiplexer switch through independent shielded wires.

[0050] The sampling resistor uses a four-wire connection. The input impedance of the voltage detection circuit V+ and V- is extremely high. The input impedance of the analog-to-digital converter is typically greater than 10MΩ. Therefore, the current flowing through the V+ and V- lines is negligible, and the voltage drop across the V+ and V- lines is almost zero. The measurement results accurately reflect the voltage across the sampling resistor, unaffected by lead resistance and contact resistance, thus achieving high-precision measurement of milliohm-level resistance.

[0051] The multiplexing switch uses an analog switch array, controlled by the main control unit 1, to sequentially connect the voltage terminals V+ and V- of each sampling resistor to the input terminals of the analog-to-digital converter. A constant current source is used to input a constant current, such as 10mA, to the current terminal of the currently selected sampling resistor. The output terminals of the constant current source are connected to the I+ and I- terminals of the sampling resistor, forming a complete current loop.

[0052] A constant current source is applied to convert the resistance of the grounding loop to be measured, including relay contact resistance, connecting wire resistance, and contact resistance, into a voltage signal that is easier to measure. According to Ohm's law R = V / I, when I is a known constant, R can be accurately calculated by measuring V.

[0053] A constant current source is used instead of a constant voltage source. When the grounding resistance is very small, such as 10mΩ, a constant voltage source would generate a huge current, such as 1V / 0.01Ω=100A, which could easily burn out the circuit. However, with a 10mA constant current source, the voltage across the sampling resistor is only 0.1mV, which, combined with a 24-bit ADC, can achieve high-precision measurement. At the same time, the constant current source solution can achieve a wide dynamic range of resistance detection, from 1mΩ to hundreds of Ω, and the calculation is simple, reducing the burden on the main control unit 1.

[0054] An analog-to-digital converter (ADC) measures the voltage across the sampling resistor and converts the measured value into a digital signal, which is then transmitted to the main control unit 1. The main control unit 1 calculates the grounding resistance value based on the constant current and voltage values ​​using the formula R = V / I. Then, the main control unit 1 compares the calculated grounding resistance value with a preset threshold, such as 10mΩ. If the grounding resistance value is less than the preset threshold, the channel is determined to be in a "good grounding" state; if the grounding resistance value is greater than or equal to the preset threshold, or an open circuit is detected, the channel is determined to be in a "termination anomaly" state.

[0055] In practical applications, research has revealed that with increasing usage, under the same temperature and humidity conditions, the resistance value of the sampling resistor will generally age or drift. Under slight aging or drift, the sampling resistor can still function normally; this stage represents normal variation and not substantial damage. Therefore, it is necessary to test and evaluate the overall performance of the sampling resistor to maximize its lifespan. To achieve this, this embodiment proposes a sampling resistor lifespan assessment model, which specifically includes: The first analysis module is used to collect the voltage values ​​of all connected sampling resistors in real time and store them temporarily. It presets the reference voltage value of the sampling resistor, traverses the temporarily stored voltage values ​​of the sampling resistors and compares them one by one with the reference voltage value, and calculates the deviation of the voltage values ​​from the reference voltage value.

[0056] The second analysis module stores the voltage value of the current sampling resistor if the deviation amplitude between the current sampling resistor voltage value and the reference voltage value is within a set range, such as ±10%; otherwise, it discards the voltage value of the current sampling resistor if the deviation amplitude exceeds the set range.

[0057] The third analysis module fits the voltage values ​​of the centrally stored sampling resistors onto a coordinate system and generates a distribution curve. A dynamic update mechanism is used for the centrally stored voltage values. This means that the number of centrally stored voltage values ​​is fixed, for example, 500 sets of data. A strategy of "adding the latest data and discarding the oldest data" is employed to dynamically update the centrally stored data while maintaining a constant number, thereby achieving dynamic correction of the distribution curve.

[0058] The fourth analysis module sets the normal distribution range of the sampling resistor voltage value and monitors the distribution curve in real time. If the data on the distribution curve reaches a set ratio (such as 20% of the total data) that exceeds the normal distribution range of the sampling resistor voltage value (such as 5mV-15mV), it indicates that the overall lifespan of the sampling resistor has reached the warning value. It is necessary to improve the environment and / or replace the entire sampling resistor to ensure the reliable operation of the grounding protection system of the temperature measuring RTD and prevent accidents.

[0059] The human-machine interface unit is equipped with a 7-inch touchscreen, connected to the main control unit 1, and is used to display the real-time status of all channels graphically. For example, a green icon indicates a "good grounding" status, a red icon indicates a "bad grounding" status, and a yellow icon indicates a "testing" status. The human-machine interface unit also provides local operation buttons such as "one-click grounding," "one-click recovery," and "system self-test."

[0060] Figure 3 This is a schematic diagram of the safety interlocking logic provided in an embodiment of the present invention. The safety interlocking interface module 4 is connected to the main control unit 1 and provides two sets of independent "ground-ready" dry contacts with a contact capacity of 250V / 5A. Figure 3 As shown, this dry contact must be connected in series in the control circuit of the withstand voltage test equipment. Specifically, one end of the dry contact is connected to the allowable voltage boost signal input terminal of the withstand voltage test equipment, and the other end is connected to the reference ground or control power supply. Only when the main control unit 1 determines that all channels are properly grounded, i.e., the grounding resistance of all channels is less than 10mΩ, will the main control unit 1 control the safety interlock interface module 4 to close the dry contact. At this time, the allowable voltage boost signal of the withstand voltage test equipment is valid, and the test equipment is allowed to perform voltage boosting operation. When any channel is grounded abnormally, the dry contact remains open, forcibly prohibiting voltage boosting from an electrical principle perspective.

[0061] The communication interface module is configured with an Ethernet port to support the Modbus TCP protocol, while also retaining an RS485 interface to support the Modbus RTU protocol, which is used to upload system status, alarm information, and operation logs to the power plant monitoring system in real time.

[0062] In some feasible implementations, fiber optic communication interfaces can be used in environments with strong electromagnetic interference; in renovation projects where wiring is difficult, industrial-grade wireless communication modules, such as Wi-Fi 6 industrial version or 5G private network modules, can be used.

[0063] The system self-diagnostic module operates under the control of the main control unit 1 and is used to automatically detect the integrity of each module when the system is powered on. Specifically, it can detect the working status of the main control unit 1, detect whether the drive circuit of each relay contact is normal, detect whether each measurement channel is normal, and detect whether the communication link is normal.

[0064] In some feasible implementations, the "channel diagnosis" mode can also be manually activated through the human-machine interaction unit to accurately locate faulty relays or lines.

[0065] Figure 4 This is a flowchart of the intelligent grounding state control method provided in an embodiment of the present invention. Based on the above system, this embodiment provides an intelligent grounding state control method, which includes the following steps: S1. Start the self-test program of the temperature measurement RTD grounding protection system and generate the self-test results.

[0066] Connect all RTD leads to this system. Connect the three leads of each RTD to the common terminal of the corresponding relay contact. Connect the normally closed terminal of each relay contact to the corresponding functional terminal of the temperature measuring device. Connect line A to I+, line B to V+, and line C to I- / V-.

[0067] After the system is powered on, the main control unit 1 triggers the system self-diagnosis module to perform a self-test, which detects the working status of the main control unit 1, the multi-path grounding execution matrix module 2, the grounding status inspection module 3, and the communication interface module.

[0068] After the self-test is completed, the human-computer interaction unit reports "System normal, waiting for instructions".

[0069] S2. Receive and respond to the grounding command, and the main control unit 1 controls all electromagnetic relays of the multi-channel grounding execution matrix module 2 to operate; connect the common terminal of all electromagnetic relays to the normally open terminal, and short-circuit all RTD leads to the grounding bus.

[0070] Specifically, the operator can click the "one-click grounding" button on the touch screen of the local human-machine interaction unit, or send the "one-click grounding" command through the communication interface module on the remote monitoring system 6.

[0071] After receiving the grounding command, the main control unit 1 drives all relay contacts to operate in sequence according to the board order. The drive pulse width is 50ms to ensure that all relay contacts are reliably engaged, so that the common terminal of all relay contacts is connected to the normally open terminal, thereby shorting all RTD leads to the system ground bus GND.

[0072] S3. Start the grounding status inspection module 3, input a constant current to the sampling resistor in each grounding loop and measure the voltage across its two ends, and indirectly determine the resistance value through the voltage; detect the grounding resistance of each grounding loop one by one; and determine whether the grounding resistance of all channels is lower than the preset threshold.

[0073] Specifically, after the relay contacts complete their operation, the main control unit 1 delays for 100ms to allow the contacts to stabilize before starting the grounding status inspection module 3 for cyclic detection. The main control unit 1 controls the multiplexer switch to sequentially connect the voltage terminal of each sampling resistor to the analog-to-digital converter at a rate of 100 channels / second.

[0074] For each channel, a constant current source inputs a constant current of 10mA to the current terminal of the sampling resistor. The analog-to-digital converter measures the voltage across the sampling resistor. The main control unit 1 calculates the grounding resistance value according to R=V / I and takes the average value after three consecutive measurements. If the average value is <10mΩ, the channel is determined to be in a "good grounding" state; if the average value is ≥10mΩ or an open circuit is detected, the channel is determined to be in a "grounding abnormal" state, and the fault channel number is recorded.

[0075] S4. When the grounding resistance of all channels is lower than the preset threshold, it is determined to be in a grounding ready state; a grounding ready signal is output through the safety interlock interface to allow the withstand voltage test equipment to increase the voltage.

[0076] Specifically, the main control unit 1 summarizes the judgment results of all channels.

[0077] The system only determines the "grounding ready" state when all channels are determined to be in a "grounding good" state. At this time, the main control unit 1 controls the safety interlock interface module 4 to close the "grounding ready" dry contact, and at the same time sends a "test allowed" signal to the upper-level monitoring system 6 through the communication interface module.

[0078] If any channel is determined to be in a "grounding abnormality" state, the interlocking contact will remain open, the location of the abnormal channel will be displayed on the human-machine interface unit, and an abnormal alarm message will be sent through the communication interface module.

[0079] S5. During the withstand voltage test, continuously monitor the grounding status of each channel. If the grounding resistance of any channel is detected to be higher than or equal to the preset threshold, interrupt the grounding ready signal.

[0080] Specifically, once the withstand voltage test equipment detects that the "grounding ready" dry contact is closed, the operator is allowed to conduct a voltage boost test.

[0081] During the withstand voltage test, the main control unit 1 continuously activates the grounding status inspection module 3 at a frequency of 1Hz to periodically inspect the grounding status of all channels.

[0082] Once the grounding resistance value of any channel is found to rise to ≥10mΩ, or an open circuit is detected, the main control unit 1 immediately controls the safety interlock interface module 4 to disconnect the "grounding ready" dry contact, and sends an emergency interruption command and abnormal channel information to the upper-level monitoring system 6 through the communication interface module to forcibly interrupt the test.

[0083] S6. Receive and respond to the recovery command, control all electromagnetic relays to reset, connect the common terminal of all electromagnetic relays to the normally closed terminal, switch each lead of RTD back to the corresponding functional port of the temperature measuring device, restore the three-wire temperature measuring circuit, and generate an operation record.

[0084] Specifically, after the pressure test is completed, the operator clicks the "One-Click Restore" button on the touch screen of the human-machine interface unit. After receiving the restore command, the main control unit 1 drives all relay contacts to reset, so that the common terminal of all relay contacts is connected to the normally closed terminal. The three leads of each RTD are switched back to the corresponding functional terminals of the temperature measuring device, with line A connected to I+, line B connected to V+, and line C connected to I- / V-, thus restoring the three-wire temperature measuring circuit.

[0085] Subsequently, the main control unit 1 automatically generates an electronic record sheet for this grounding operation. The electronic record sheet includes: operation time, operator ID, grounding duration, and final status of each channel, such as the total number of channels, the number of good channels, and a list of abnormal channels. This record sheet is stored in local memory and simultaneously uploaded to the upper-level monitoring system 6 via the communication interface module.

[0086] In some feasible implementations, the technical solution provided by this invention is not only applicable to hydroelectric and steam turbine generators, but can also be extended to large synchronous motors, rolling mill motors, wind turbine generators, and other applications requiring winding withstand voltage tests. Furthermore, before conducting induced withstand voltage or partial discharge tests on large power transformers, the leads of their winding thermometers also need to be reliably grounded; this system can be adapted for use.

[0087] The grounding protection system and grounding control method for a temperature measuring RTD provided by this invention have at least the following beneficial effects: The grounding protection system and grounding control method for temperature measuring RTDs provided in this embodiment of the invention adopts a relay contact array driven by the main control unit 1, and each lead of each RTD is independently connected to the corresponding relay contact, realizing centralized switching of the grounding status of all RTD leads, shortening the tedious manual operation to an automatic operation in a short time, and improving the operation efficiency and reliability.

[0088] The grounding protection system and control method for temperature measuring RTD provided in this embodiment of the invention connects the normally closed terminals of the relay contacts corresponding to the three leads of each RTD to the corresponding functional terminals of the temperature measuring device, ensuring the integrity of the three-wire RTD measurement circuit and the normal operation of the lead resistance compensation mechanism in non-test conditions, and automatically restoring accurate temperature measurement after the test.

[0089] The grounding protection system and control method for temperature measuring RTD provided in this embodiment of the invention integrates a grounding status inspection module 3. It uses a four-wire Kelvin connection to periodically and accurately measure the continuity resistance of each grounding loop. It uses a constant current source to convert the resistance to be measured into an easily measurable voltage signal, realizing high-precision detection of milliohm-level grounding resistance and providing feedback on the results in a visual manner, thus eliminating the hidden dangers of ungrounded and false grounding.

[0090] The grounding protection system and control method for temperature measuring RTD provided in this invention, by outputting a grounding-ready hard contact signal, is forcibly connected in series to the control circuit of the withstand voltage test equipment, thus solving the possibility of false voltage rise from the technical source. The complete management process covers multiple procedures such as self-testing, instruction execution, status verification, continuous monitoring, anomaly handling and record generation, meeting the information needs of modern factories.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A grounding protection system for a temperature-measuring RTD, characterized in that, include: Main control unit, multi-channel grounding execution matrix module, grounding status inspection module and safety interlock interface module; The multi-path grounding execution matrix module includes multiple electromagnetic relays connected to and controlled by the main control unit. Each lead of the RTD is connected to the common terminal of a relay contact, and the multiple relay contacts are provided by at least one electromagnetic relay. The normally open terminals of the relay contacts are used to connect to the grounding bus. The grounding status inspection module includes a sampling resistor connected in series in each grounding loop, and a measurement circuit connected to the main control unit. The measurement circuit and the sampling circuit are connected to detect the electrical parameters across each sampling resistor. The main control unit is used to determine the grounding status of each grounding loop based on the electrical parameters. The safety interlock interface module is connected to the main control unit and is used to output a grounding ready signal, which is then used to connect to the control circuit of the withstand voltage test equipment.

2. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, The RTD is a three-wire RTD, which has three leads with different functions: the excitation current positive lead, the voltage detection positive lead, and the common circuit lead. Each RTD's three leads are connected to the common terminals of three independent electromagnetic relays, or to the three common terminals of a three-pole relay.

3. The temperature measurement RTD grounding protection system according to claim 2, characterized in that, Electromagnetic relays also have normally closed terminals; The normally closed terminals of the electromagnetic relays corresponding to the three leads of each RTD are respectively connected to the corresponding functional ports of the temperature measuring device. Specifically, the normally closed terminal corresponding to the excitation current positive lead is connected to the excitation current positive port of the temperature measuring device, the normally closed terminal corresponding to the voltage detection positive lead is connected to the voltage detection positive port of the temperature measuring device, and the normally closed terminal corresponding to the common circuit lead is connected to the common circuit port of the temperature measuring device. The common terminal of all electromagnetic relays is connected to the normally open terminal, which is used to short-circuit all leads of the RTD to the ground bus in the ground protection state.

4. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, The electromagnetic relay is a magnetically shielded electromagnetic relay; A magnetically shielded electromagnetic relay includes a shielding cover made of highly permeable magnetic material. The shielding cover encloses the coil and magnetic circuit of the electromagnetic relay, forming a magnetic shielding structure. The electromagnetic relay has a reinforced insulation structure between the coil and the contacts.

5. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, The measurement circuit of the grounding status inspection module includes a multiplexer, a constant current source, and an analog-to-digital converter; The sampling resistor is a four-wire precision sampling resistor. The four-wire precision sampling resistor has a pair of current terminals and a pair of voltage terminals. The pair of current terminals are connected in series in the grounding main circuit, and the pair of voltage terminals are connected to the main control unit through a multiplexer and an analog-to-digital converter. The sampling resistor uses the Kelvin connection method.

6. The grounding protection system for temperature-measuring RTD according to claim 5, characterized in that, The multiplexing switch is connected to the main control unit and is used to sequentially connect the voltage terminal of each sampling resistor to the analog-to-digital converter; A constant current source is connected to a sampling resistor and a constant current is input to it; An analog-to-digital converter is used to measure the voltage across a sampling resistor; The main control unit is used to calculate the grounding resistance value based on the constant current and voltage values, and compare it with a preset threshold to determine the grounding status.

7. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, Also includes: Human-computer interaction unit; The human-machine interaction unit is connected to the main control unit. The human-machine interaction unit includes a touch screen and / or indicator panel, which is used to display the grounding status of all RTD channels in a graphical manner and provide an operation command input interface. The operation instructions include at least one of the following: one-key grounding instruction, one-key recovery instruction, and system self-test instruction.

8. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, Also includes: Communication interface module; The communication interface module is connected to the main control unit and is used to upload at least one of the system status information, alarm information and operation log to the upper monitoring system. The communication interface module supports at least one of the following communication protocols: RS485 / Modbus RTU protocol, Ethernet / Modbus TCP protocol, and IEC 61850 protocol.

9. The grounding protection system for temperature-measuring RTD according to claim 1, characterized in that, Also includes: System self-diagnosis module; The system self-diagnostic module is used to perform fault detection on at least one of the main control unit, the multi-channel grounding execution matrix module, the grounding status inspection module, and the communication interface module when the system is powered on or in response to a received self-test command, and output the diagnostic results.

10. The grounding protection system for a temperature-measuring RTD according to claim 1, characterized in that, The grounding ready signal output by the safety interlock interface module is a dry contact signal; The dry contact signal closes only when the grounding state inspection module determines that the grounding resistance of all channels is lower than the preset threshold; when the grounding resistance of any channel is higher than or equal to the preset threshold, the dry contact signal remains open.

11. The grounding protection system for a temperature-measuring RTD according to claim 1, characterized in that, Also includes: The sampling resistor lifetime assessment model includes: The first analysis module is used to collect the voltage values ​​of all connected sampling resistors in real time and store them temporarily; it presets the reference voltage value of the sampling resistor, iterates through the temporarily stored voltage values ​​of the sampling resistors and compares them one by one with the reference voltage value, and calculates the deviation of the voltage values ​​from the reference voltage value. The second analysis module stores the voltage value of the current sampling resistor if the deviation amplitude between the current sampling resistor voltage value and the reference voltage value is within the set range; otherwise, it discards the current sampling resistor voltage value if the deviation amplitude exceeds the set range. The third analysis module fits the voltage values ​​of the centrally stored sampling resistors in the coordinate system and generates a distribution curve. A dynamic update mechanism is adopted for the voltage values ​​of the centrally stored sampling resistors. That is, the number of voltage values ​​of the centrally stored sampling resistors is fixed, and a strategy of "adding the latest data and eliminating the oldest data" is adopted to make the centrally stored data dynamically updated and always keep the number constant, thereby realizing the dynamic correction of the distribution curve. The fourth analysis module sets the normal distribution range of the sampling resistor voltage value and monitors the distribution curve in real time. If the data on the distribution curve reaches a set ratio that exceeds the normal distribution range of the sampling resistor voltage value, it indicates that the overall lifespan of the sampling resistor has reached the warning value.

12. A control method for a temperature-measuring RTD grounding protection system, applied to the temperature-measuring RTD grounding protection system according to any one of claims 1-10, characterized in that, Includes the following steps: Step S1. Start the self-test program of the temperature measurement RTD grounding protection system and generate the self-test results; Step S2. Receive and respond to the grounding command, and the main control unit controls the operation of all electromagnetic relays in the multi-channel grounding execution matrix module; Connect the common terminal of all electromagnetic relays to the normally open terminal, and short-circuit all RTD leads to the ground bus. Step S3. Start the grounding status inspection module, input a constant current into the sampling resistor in each grounding loop and measure the voltage across its two ends, and indirectly determine the resistance value through the voltage; detect the grounding resistance of each grounding loop one by one; and determine whether the grounding resistance of all channels is lower than the preset threshold. Step S4. When the grounding resistance of all channels is lower than the preset threshold, the grounding ready state is determined; a grounding ready signal is output through the safety interlock interface to allow the withstand voltage test equipment to increase the voltage; Step S5. During the withstand voltage test, continuously monitor the grounding status of each channel. If the grounding resistance of any channel is detected to be higher than or equal to the preset threshold, interrupt the grounding ready signal. Step S6. Receive and respond to the recovery command, control all electromagnetic relays to reset, connect the common terminal of all electromagnetic relays to the normally closed terminal, switch each lead of RTD back to the corresponding functional port of the temperature measuring device, restore the three-wire temperature measuring circuit, and generate an operation record.

13. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S1, the self-test program of the temperature measurement RTD grounding protection system is started, including: The system detects at least one of the following: the working status of the main control unit; the driving circuits of each electromagnetic relay in the multi-channel grounding execution matrix module are normal; the measurement channels in the grounding status inspection module are normal; and the communication link of the communication interface module is normal.

14. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S2, a grounding command is received and responded to, and the main control unit controls the operation of all electromagnetic relays in the multi-path grounding execution matrix module, including: The main control unit drives each group of electromagnetic relays in a preset order, with the driving pulse width of each group of electromagnetic relays ranging from 30 milliseconds to 80 milliseconds.

15. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S3, a constant current is input to the sampling resistor in each grounding loop, and the voltage across its terminals is measured. The resistance value is then indirectly determined by the voltage, including: A constant current is input to the current terminal of the currently detected sampling resistor through a constant current source; The voltage across the sampling resistor is measured using an analog-to-digital converter. The main control unit calculates the grounding resistance value based on the constant current and voltage values. The calculation formula is R = V / I, where R is the grounding resistance value, V is the voltage value, and I is the constant current value.

16. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S3, the grounding resistance of each grounding loop is tested, including: The main control unit controls the multi-channel selection switch to sequentially connect the voltage terminal of each sampling resistor to the analog-to-digital converter, thereby realizing the cyclic detection of multiple channels.

17. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S4, a grounding ready signal is output through the safety interlock interface, including: When the grounding ready state is determined, the main control unit controls the safety interlock interface module to close the dry contact to output a grounding ready signal; When the system is determined to be in a non-grounded ready state, the main control unit controls the safety interlock interface module to disconnect the dry contacts.

18. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S5, during the withstand voltage test, the grounding status of each channel is continuously monitored, including: During the withstand voltage test, the grounding status inspection module is periodically activated at a preset frequency of 0.5Hz to 2Hz to detect the grounding resistance of all channels.

19. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S5, the preset threshold for the grounding resistance is 10 milliohms.

20. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S5, if the grounding resistance of any channel is detected to be higher than or equal to a preset threshold, the grounding ready signal is interrupted, and then the following steps are performed: The communication interface module sends emergency interruption commands and abnormal channel information to the upper-level monitoring system.

21. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S6, the generated operation record includes at least one of the following: operation time, operator identity information, grounding duration, and final status of each channel.

22. The control method for the grounding protection system of the temperature measuring RTD according to claim 12, characterized in that, In step S6, after generating the operation record, the following steps are also performed: The operation records are stored in local memory and / or uploaded to the upper-level monitoring system via the communication interface module.

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