An end monitoring module and railway signal cable end monitoring system

Abstract

The application discloses an end monitoring module and a railway signal cable end monitoring system. The module comprises: a lightning peak monitoring unit for monitoring the lightning current peak at the end of the railway signal cable; a wide-range power frequency current acquisition unit for monitoring the wide-range power frequency fault current of the grounding loop at the end of the railway signal cable; a full-temperature-zone linear temperature monitoring unit for monitoring the operating temperature in the full-temperature-zone at the end of the railway signal cable; and a threshold-adjustable arc monitoring unit for monitoring the early hidden arc fault at the end of the railway signal cable and issuing a warning. The application integrates multiple parameter monitoring units, simplifies the wiring structure, optimizes the spatial layout, reduces the number of field wiring from the root, and reduces the construction complexity and safety hazards.

Description

Technical Field

[0001] This invention belongs to the field of railway termination monitoring technology, and particularly relates to a termination monitoring module and a railway signal cable termination monitoring system. Background Technology

[0002] Signal cables are the physical links for transmitting control commands and monitoring signals in railway signaling systems. The cable termination grounding structure is the protective node of the signal cable. It must not only ensure the reliable grounding of the cable's aluminum sheath and armored steel tape to discharge and guide lightning surges and power frequency interference, but also ensure the insulation performance and electrical continuity of the cable termination.

[0003] Traditional railway signal cable termination and grounding processes mostly employ standardized mechanical connection structures. These structures directly and rigidly connect the cable's outer aluminum sheath and steel armor layer to the grounding main line via dedicated grounding terminals and copper busbar connectors. This only achieves basic grounding continuity and completely lacks the capability for online monitoring and early warning of operational anomalies. In actual railway field maintenance, cable termination points are highly susceptible to hidden faults such as abnormally high grounding resistance, lightning strike damage, localized overheating, and insulation layer damage. These faults cannot be quickly diagnosed through manual inspections and often require post-incident repairs only after signal interruption or grounding failure. This significantly increases the workload and cost of railway field maintenance and poses substantial safety hazards, making it difficult to meet the demands of modern railway proactive safety and intelligent maintenance.

[0004] To address the shortcomings of traditional grounding structures lacking monitoring capabilities, existing technologies have gradually introduced online monitoring devices for the termination of railway signal cables. These devices collect core parameters in real time, such as grounding frequency leakage current, lightning strike amplitude, and ambient temperature at the termination point, attempting to predict grounding fault risks in advance. Among these, Chinese utility model patent CN221899310U, entitled "Termination Monitoring Box and Cable Termination Monitoring Device," discloses a termination monitoring box with a channel structure open at both ends. The grounding component of the termination box can pass through this channel structure, achieving non-intrusive installation without altering the original grounding bolt connection structure. This, to some extent, solves the problem of early monitoring devices requiring disruption of the original grounding connection.

[0005] Another Chinese utility model patent, CN219123983U, entitled "Online Monitoring System for Termination of Railway Signal Cables," discloses a split-type monitoring system. This system employs a structure of termination maintenance terminals and termination data acquisition equipment, enabling lightning monitoring of termination grounding wires and monitoring of ambient temperature and humidity. However, this split-type design requires prior on-site surveys and customized acquisition boxes, resulting in poor versatility; the external sensor wiring is complex, leading to a long construction and commissioning cycle.

[0006] Existing technologies require separate installation of dedicated sensor modules for three core indicators: current monitoring, lightning strike amplitude, and temperature monitoring. Each sensor necessitates its own power supply and signal transmission cables, lacking a unified power supply and signal integration solution. During on-site construction, multiple independent cables must be laid and secured within confined cable termination boxes, leading to cumbersome construction procedures, a significant increase in wiring workload, and a chaotic and disorganized cable arrangement within the termination boxes. More importantly, the dense arrangement of numerous independent cables in a confined space exposes them to long-term exposure to railway vibrations, temperature and humidity variations, and electromagnetic interference, making them highly susceptible to insulation aging and damage, short circuits, and signal crosstalk. This not only reduces the accuracy of monitoring data but also significantly increases the safety risks of electrical fires and grounding failures, violating the engineering design principles of high safety, high reliability, low maintenance, and intensive operation of railway signaling systems. Summary of the Invention

[0007] The purpose of this invention is to provide an end-of-line monitoring module and a railway signal cable end-of-line monitoring system, which partially solves or alleviates the above-mentioned deficiencies in the prior art, integrates multi-parameter monitoring units, simplifies the wiring structure, optimizes the spatial layout, reduces the amount of on-site wiring from the source, and reduces construction complexity and safety hazards.

[0008] To solve the aforementioned technical problems, the present invention specifically adopts the following technical solution: A first aspect of the present invention is to provide an end-to-end monitoring module, comprising: Lightning peak current monitoring unit is used to monitor the peak lightning current at the termination of railway signal cables; Wide-range power frequency current acquisition unit is used to monitor the wide-range power frequency fault current of the grounding circuit at the end of railway signal cables; A full-temperature-range linear temperature monitoring unit is used to monitor the operating temperature of railway signal cables across the entire temperature range at the termination point. The threshold adjustable arc monitoring unit is used to monitor early latent arc faults at the termination of railway signal cables and issue early warnings.

[0009] Furthermore, the lightning peak monitoring unit uses a Rogowski coil sleeved on the ground wire as a sensing element. The output terminal of the Rogowski coil is connected in sequence to a reference lifting circuit, an RC integral circuit, a precision full-wave rectifier circuit, and a peak hold circuit. The output terminal of the peak hold circuit is connected to a control unit. The differential signal generated by the lightning strike current induced by the Rogowski coil is raised by the reference lifting circuit, restored to the original lightning strike current waveform by the RC integrating circuit, converted into a unipolar signal by the precision full-wave rectifier circuit, and then the peak voltage is maintained by the peak holding circuit for acquisition by the control unit, so as to obtain the peak value of the lightning strike current through the control unit calculation.

[0010] Furthermore, the method for the control unit to calculate the peak lightning current includes: The peak voltage induced by the Rogowski coil is acquired through a peak hold circuit. Quantile statistics were performed on each frame of lightning strike sampling data to obtain the first quantile, the second quantile, and the third quantile; The difference between the third quantile and the first quantile is used as the platform flatness criterion, and combined with continuous p-frame data to confirm and prevent false triggering; After a valid lightning strike event is determined, the peak lightning current is released, and a clear pulse is generated to reset the peak holding circuit.

[0011] Furthermore, the wide-range power frequency current acquisition unit includes a power frequency transformer, a reference rise circuit, a sampling resistor, and a dual-range AC amplifier circuit. The secondary output terminal of the power frequency transformer is connected to the reference rise circuit. After being converted into a voltage signal by the sampling resistor, the signal is sent to the dual-range AC amplifier circuit. The output terminal of the dual-range AC amplifier circuit is connected to the control unit. The power frequency transformer senses and collects the power frequency current of the grounding circuit. The secondary side of the transformer outputs a standard small current signal after attenuation, which is converted into a corresponding voltage signal by a high-precision sampling resistor. After being synchronously conditioned by a dual-range amplifier circuit, it is sent to the control unit for acquisition, so that the actual value of the power frequency current can be obtained by the control unit.

[0012] Furthermore, the dual-range AC amplifier circuit includes a low-range power frequency amplifier circuit and a high-range power frequency amplifier circuit. The input terminals of the two amplifier circuits are connected in parallel to the output terminals of the sampling resistor, and the output terminals are respectively connected to different acquisition ports of the control unit. The low-range power frequency amplifier circuit is used to amplify small current signals of 0.5A-5A, and the high-range power frequency amplifier circuit is used to amplify large current signals of 5A-70A.

[0013] Furthermore, the method for the control unit to calculate the actual value of the power frequency current includes: The output signals of the low-frequency amplifier circuit and the high-frequency amplifier circuit are sampled separately; n points are sampled in each cycle, and m cycles constitute one frame. The average value of n*m sampling points in each frame is taken as the DC component, and the AC component is obtained by subtracting the DC component from each sampling point; Calculate the effective value of the AC component, and convert the effective value of the AC component into the actual current value through a piecewise linear fitting table; Determine if the low-frequency amplifier circuit is saturated. If it is saturated, output the current value corresponding to the high-frequency amplifier circuit; otherwise, output the current value corresponding to the low-frequency amplifier circuit.

[0014] Furthermore, the full-temperature-range linear temperature monitoring unit includes a temperature sensor, a first upper resistor, a second upper resistor, a first MOSFET, a second MOSFET, and an operational amplifier circuit; the first MOSFET and the first upper resistor are connected in series to form a first voltage divider branch, the second MOSFET and the second upper resistor are connected in series to form a second voltage divider branch, and the first and second voltage divider branches are connected in parallel between the power supply and the voltage divider node; the temperature sensor is connected between the voltage divider node and ground; the voltage divider node is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the control unit; The control terminals of the first MOSFET and the second MOSFET are respectively connected to the control unit; the control unit controls the on / off state of the first MOSFET and the second MOSFET according to the collected temperature value, switches the resistance value of the upper resistor connected to the voltage divider circuit, corrects the nonlinear temperature acquisition curve of the temperature sensor, and realizes full-temperature monitoring.

[0015] Furthermore, the methods for the control unit to monitor operating temperature include: Collect the average temperature output from the operational amplifier circuit (AD value); A two-section segmented fitting method was used to convert AD values ​​into temperature values, with a low-level fitting table used for the low-temperature region and a high-level fitting table used for the high-temperature region. When the temperature reaches the cutoff boundary, the upper resistor is switched by determining the current slot and then the next slot takes effect.

[0016] Furthermore, the threshold-adjustable arc monitoring unit includes a high-pass active filter, a high-speed window comparator, and a second-order RC filter circuit. The input terminal of the high-pass active filter is connected to the output terminal of the power frequency current acquisition unit, the output terminal of the high-pass active filter is connected to the input terminal of the high-speed window comparator, the PWM output port of the control unit is connected to the second-order RC filter circuit, the output terminal of the second-order RC filter circuit is connected to the threshold input terminal of the high-speed window comparator, and the output terminal of the high-speed window comparator is connected to the control unit. The control unit adjusts the duty cycle of the output PWM wave, generates a dynamically adjustable DC threshold voltage through a second-order RC filter circuit, and controls the detection threshold of the high-speed window comparator; the control unit counts the arc pulses output by the high-speed window comparator, thereby identifying and warning of arc faults.

[0017] Furthermore, the method for the control unit to identify and warn of arc faults includes: The number of pulse edges output by the high-speed window comparator within a natural second is counted using an external interrupt. The pulse count is read and cleared every second. When the count reaches a preset threshold, it is determined as an arc warning and the arc count is accumulated. After an electric arc is triggered, the peak lightning strike release window is temporarily blocked to reduce crosstalk between the electric arc and the lightning strike event.

[0018] Furthermore, it also includes a module housing and a power supply circuit; the lightning peak monitoring unit, the wide-range power frequency current acquisition unit, the full-temperature-range linear temperature monitoring unit (excluding the temperature sensor), the threshold adjustable arc monitoring unit, and the control unit are all integrated within the module housing; the control unit is electrically connected to the power supply circuit. The module housing has a pre-drilled hole for the grounding wire to pass through. The top of the module housing is provided with an external interface for a temperature sensor. The temperature sensor is fixed to the grounding bolt of the steel strip or aluminum sheath at the end of the cable and is electrically connected to the full-temperature-range linear temperature monitoring unit through the external interface for the temperature sensor. The module housing is also provided with at least two integrated interfaces, which are connected to both the power supply circuit and the communication circuit; the terminal monitoring module is connected to the upper and lower level terminal monitoring modules respectively through the two integrated interfaces; The module housing is provided with a buckle for connecting with the guide rail; the buckle includes a fixed block and a sliding block arranged opposite each other, and the sliding block can move towards the fixed block under the action of a pre-tightening spring, thereby clamping the guide rail.

[0019] The present invention also provides a railway signal cable termination monitoring system, including a monitoring host and multiple termination monitoring modules. Each termination monitoring module is cascaded in a daisy-chain manner through an integrated interface and connected to the monitoring host.

[0020] The beneficial effects are:

[0021] The integrated monitoring module provided by this invention, through its integrated design, simultaneously achieves accurate monitoring of four parameters: lightning strike peak value, wide-range power frequency current, full-temperature range temperature, and fault arc. The use of a PCB Rogowski coil solves the magnetic saturation problem of traditional magnetic core sensors, enabling accurate measurement of the lightning strike current peak value. A dual-range power frequency amplifier circuit achieves wide-range monitoring from 0.5A to 70A, balancing accuracy at low currents with preventing overflow at high currents. A temperature correction circuit using a MOSFET switching resistor ensures monitoring accuracy across the entire temperature range of -40℃ to +200℃. A PWM-adjustable threshold arc monitoring circuit effectively distinguishes between real arcs and electromagnetic interference, enabling early fault warning.

[0022] The module adopts 35mm standard DIN rail mounting and a 4-pin daisy-chain interface, requiring no changes to the original grounding connection structure. This shortens on-site construction time, reduces cable usage, and significantly lowers construction and maintenance costs. This module is fully adaptable to the complex operating environment of railway sites, boasting high reliability, high safety, and high integration. It effectively improves the intelligent operation and maintenance level of railway signaling systems, ensuring safe train operation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a lightning strike peak monitoring, wide-range power frequency current acquisition, and threshold adjustable arc monitoring unit.

[0025] Figure 2 This is a schematic diagram of the structural principle of a full-temperature-range linear temperature monitoring unit.

[0026] Figure 3 This is a 3D view of the end-of-line monitoring module.

[0027] Figure 4 This is a cross-sectional view of the end-of-line monitoring module.

[0028] Figure 5 This is the rear view of the end-to-end monitoring module.

[0029] Figure 6 This is a schematic diagram of the installation of a railway signal cable termination monitoring system.

[0030] Summary of attached labeling and identification: 1-Module housing, 2-Wire hole, 3-Integrated interface, 4-External interface for temperature sensor, 5-PCB board, 6-Fixing block, 7-Sliding block, 8-Preload spring, 9-Rogowski coil, 100-Grounding wire, 200-Guide rail. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] In this document, suffixes such as "module," "part," or "unit" used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves. Therefore, "module," "part," or "unit" may be used interchangeably.

[0033] In this document, the terms "upper," "lower," "inner," "outer," "front," "rear," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In this document, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0036] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0037] Example 1:

[0038] This invention provides a termination monitoring module for real-time online monitoring of cable status at primary and secondary termination points of railway signal cables. The module adopts an integrated design, combining lightning peak monitoring, wide-range power frequency current acquisition, full-temperature linear temperature monitoring, and adjustable-threshold arc monitoring within the same module housing. It is fixed to the field via a 35mm standard DIN rail mounting structure, without requiring changes to the existing grounding connection. The module enables daisy-chaining networking for power supply and RS485 communication through a 4-pin integrated interface, significantly simplifying field wiring and reducing construction and maintenance costs.

[0039] In this embodiment, the module control unit (MCU) has a built-in AD converter to meet the requirements of multi-channel high-speed sampling. The power supply circuit uses a DC-DC converter chip with a wide voltage range, supporting an input voltage of 12V-24V DC and a stable output of 3.3V to power all circuits. The input stage integrates a TVS surge protection device, which can withstand surge impacts of ±2kV.

[0040] Figure 1 The structural principles of the lightning peak monitoring, wide-range power frequency current acquisition, and threshold-adjustable arc monitoring unit were demonstrated. Figure 2 The structural principle of the full-temperature-range linear temperature monitoring unit is demonstrated. The four functional modules are described in detail below.

[0041] I. Lightning Strike Peak Monitoring Unit: A lightning strike peak monitoring unit is used to monitor the peak lightning current at the termination of railway signal cables. Specifically, the lightning strike peak monitoring unit uses a Rogowski coil sleeved on the ground wire as the sensing element. The output terminal of the Rogowski coil is sequentially connected to a reference lift circuit, an RC integrator circuit, a precision full-wave rectifier circuit, and a peak hold circuit. The output terminal of the peak hold circuit is connected to a control unit. The differential signal generated by the lightning strike current induced by the Rogowski coil is raised by the reference lifting circuit, restored to the original lightning strike current waveform by the RC integrating circuit, converted into a unipolar signal by the precision full-wave rectifier circuit, and then the peak voltage is maintained by the peak holding circuit for acquisition by the control unit, so as to obtain the peak value of the lightning strike current through the control unit calculation.

[0042] In this embodiment, the lightning peak monitoring unit uses a PCB Rogowski coil as the sensing element. A circular channel coaxial with the wiring hole in the module housing is pre-reserved in the center. The grounding wire under test passes directly through this channel, achieving a completely non-intrusive installation. This eliminates the need to disconnect the original grounding loop or lengthen the grounding bolts, avoiding the safety hazards of poor grounding caused by altering the grounding structure. Based on Faraday's law of electromagnetic induction, when a lightning current passes through the grounding wire, a changing magnetic field is generated around the Rogowski coil, inducing a differential voltage signal proportional to the rate of change of current at both ends of the coil.

[0043] The differential signal output by the PCB Rogowski coil is a bipolar signal with alternating positive and negative values, while the control unit used in this invention only supports unipolar voltage input of 0~3.3V. If directly acquired, the negative half-cycle of the signal will be truncated by the AD converter, resulting in the loss of lightning strike peak values ​​and severe distortion of measurement results. The function of the 1.65V reference rise circuit is to superimpose a 1.65V DC bias onto the bipolar differential signal, shifting the entire signal to the 0~3.3V AD acquisition range while ensuring that the waveform and amplitude of the signal remain unchanged.

[0044] The output of a PCB Rogowski coil is a differential signal proportional to the rate of change of current (di / dt), not a direct current signal. Directly acquiring this differential signal only yields the rate of change of current, not the actual amplitude and waveform. The core function of the RC integrator circuit is to integrate the differential signal, restoring it to a voltage signal proportional to the original lightning strike current.

[0045] The polarity of lightning strike current is random, potentially positive or negative, resulting in a correspondingly positive or negative integral output signal. If directly fed into the peak hold circuit, the peak value of the negative half-cycle will be lost, leading to an underestimation of the lightning strike peak value. The function of the precision full-wave rectifier circuit is to convert the bipolar lightning strike signal into a unipolar positive voltage signal, enabling the peak hold circuit to capture lightning strike peak values ​​of any polarity.

[0046] Lightning strike signals are transient signals with extremely short durations, their rise time being only a few microseconds, and the entire pulse duration not exceeding 200μs. However, the maximum sampling rate of the AD converter in the control unit is typically 1MHz, requiring 1μs for a single sample, which is insufficient to complete enough sampling points within the duration of the lightning strike signal to accurately capture the peak value. The core function of the peak hold circuit is to capture and hold the maximum peak voltage of the lightning strike signal for an extended period until the control unit completes its acquisition, thus solving the problem of the control unit's sampling speed not keeping up with transient signals.

[0047] In this embodiment, the method for the control unit to calculate the peak lightning current includes: S101 acquires the peak voltage induced by the lightning strike through the Rogowski coil via a peak hold circuit.

[0048] When lightning current flows through the grounding wire, the Rogowski coil on the PCB induces a differential signal. This signal is then boosted by a 1.65V reference, integrated by an RC circuit, and rectified by a precision full-wave rectifier before being sent to the peak hold circuit. The peak hold circuit quickly charges the output voltage to the maximum value of the lightning signal and maintains this voltage. Within each 250ms slot cycle, the MCU continuously acquires 160 output voltage values ​​from the peak hold circuit and stores them in an internal buffer for subsequent processing. No filtering is performed during the acquisition process, preserving the original characteristics of the signal completely.

[0049] S102 performs quantile statistics on each frame of lightning strike sampling data to obtain the first quantile, the second quantile, and the third quantile.

[0050] A quantile is a value that ranks at a specific percentile after a set of data has been sorted from smallest to largest. This example uses three quantiles.

[0051] The first quantile, q10, is the value at the 10th percentile when the sorted data is arranged in ascending order. It indicates that 10% of the sample points are less than this value, reflecting the lower limit of the data.

[0052] The second quantile, q50, is the median, located at the 50th percentile. It indicates that half of the sampled points are less than this value and half are greater than it, making it the most robust measure of central tendency in a dataset.

[0053] The third quantile q90 is the value located at the 90th percentile. It indicates that 90% of the sampled points are less than this value, reflecting the upper limit of the data.

[0054] S103 uses the difference between the third quantile and the first quantile as the platform flatness criterion, and combines continuous p-frame data to confirm and prevent false triggering.

[0055] A real lightning strike signal, after passing through a peak hold circuit, forms a flat voltage plateau lasting ≥500ms. During this plateau, the values ​​of the 160 sampling points acquired by the MCU are very close, with extremely low data dispersion. In contrast, electromagnetic interference signals fluctuate randomly, cannot form a stable plateau, and exhibit extremely high data dispersion.

[0056] This invention uses the difference between the third quantile and the first quantile, Δq = q90 - q10, as a quantitative indicator of platform flatness. The smaller Δq is, the more concentrated the data, the flatter the platform, and the more likely it is a genuine lightning strike. The larger Δq is, the more dispersed the data, the greater the fluctuation, and the more likely it is noise interference. Based on extensive on-site railway measurement data, this invention sets the flatness threshold to 50mV. That is, when Δq≤50mV, the frame data is determined to be a suspected lightning strike platform; when Δq>50mV, the frame data is determined to be noise interference and is discarded directly.

[0057] To further reduce the false trigger rate, this invention introduces a two-frame cross-confirmation mechanism. When the first frame of data is determined to be a suspected lightning strike platform, the system does not trigger immediately but continues to wait for the next frame of data. Only when both consecutive frames of data meet the flatness condition of Δq≤50mV is it finally determined to be a valid lightning strike event. If the second frame of data does not meet the condition, the first frame is determined to be transient interference, and the suspected status is cleared.

[0058] After S104 determines that a lightning strike event is valid, it publishes the peak value of the lightning current and generates a clear pulse to reset the peak holding circuit.

[0059] After determining it to be a valid lightning strike event, the system selects the q50 value from the second frame of data as the final peak voltage. This is because q50 is the median, unaffected by individual abnormal sampling points, and best represents the platform's true voltage. The second frame of data is in the stable holding phase of the peak hold circuit, resulting in smaller voltage fluctuations and higher measurement accuracy.

[0060] The peak voltage is substituted into the pre-calibrated coefficient to convert it into the actual peak lightning current.

[0061] The MCU transmits lightning strike event information to the background monitoring host via the RS485 bus. After the event is transmitted, the MCU outputs a high-level clear pulse MCU_CLEAN through the IO port to quickly discharge the holding capacitor, resetting the output voltage of the peak holding circuit to the 1.65V reference level, preparing for the next lightning strike detection.

[0062] II. Wide-range power frequency current acquisition unit: A wide-range power frequency current acquisition unit is used to monitor the wide-range power frequency fault current of the grounding loop at the termination of railway signal cables. Specifically, the wide-range power frequency current acquisition unit includes a power frequency transformer, a reference rise circuit, a sampling resistor, and a dual-range AC amplifier circuit. The secondary output terminal of the power frequency transformer is connected to the reference rise circuit, and the signal is converted into a voltage signal by the sampling resistor and then sent to the dual-range AC amplifier circuit. The output terminal of the dual-range AC amplifier circuit is connected to a control unit. The power frequency transformer senses and collects the power frequency current of the grounding circuit. The secondary side of the transformer outputs a standard small current signal after attenuation, which is converted into a corresponding voltage signal by a high-precision sampling resistor. After being synchronously conditioned by a dual-range amplifier circuit, it is sent to the control unit for acquisition, so that the actual value of the power frequency current can be obtained by the control unit.

[0063] This embodiment uses a through-hole precision current transformer. The through-hole structure enables completely non-intrusive installation. The grounding wire under test passes directly through the center hole of the transformer, without cutting the cable or modifying the original grounding connection, thus avoiding the risk of affecting the reliability of the grounding system from the source.

[0064] Power frequency current is a sinusoidal signal with alternating positive and negative values, while the MCU used in this invention only supports 0-3.3V unipolar voltage input via its AD converter. Direct acquisition would result in the negative half-cycle of the signal being truncated by the AD converter, leading to waveform distortion and incorrect RMS value calculation. The 1.65V reference lift-up circuit superimposes a 1.65V DC bias onto the alternating current signal, shifting the signal to the midpoint of the 0-3.3V AD acquisition range, maximizing the dynamic range of the AD converter while maintaining the signal's waveform and amplitude.

[0065] A current transformer outputs a current signal, while an A / D converter can only acquire voltage signals. The sampling resistor converts the current signal on the secondary side into a corresponding voltage signal according to Ohm's law.

[0066] Existing terminal monitoring devices generally use single-range amplifier circuits. If the gain is set too high, the accuracy is sufficient for small current signals, but large current signals will exceed the 3.3V upper limit of the AD converter, causing signal overflow and distortion. If the gain is set too low, large current signals will not overflow, but the amplitude of small current signals is too small, and the resolution of the AD converter cannot be fully utilized, resulting in a large measurement error. For example, when using a single-range 1x gain, a 0.5A primary current corresponds to a 0.5mA secondary current, and the sampling resistor voltage is 0.05V. A 12-bit AD converter with a resolution of 3.3V / 4096≈0.8mV can only distinguish about 62 scales, resulting in a measurement error exceeding 1.5%, which fails to meet the requirements.

[0067] To address the aforementioned issues, in this embodiment, the dual-range AC amplifier circuit includes a low-range power frequency amplifier circuit and a high-range power frequency amplifier circuit. The input terminals of the two amplifier circuits are connected in parallel to the output terminals of the sampling resistor, and their output terminals are respectively connected to different acquisition ports of the control unit. The low-range power frequency amplifier circuit is used to amplify small current signals of 0.5A-5A, and the high-range power frequency amplifier circuit is used to amplify large current signals of 5A-70A.

[0068] The inputs of the two amplifier circuits are connected in parallel to the output of the sampling resistor, and their outputs are connected to the two independent AD acquisition ports of the MCU, achieving fully synchronous sampling. This ensures that, under any current value, one amplifier circuit always operates in the optimal linear range, making full use of the resolution of the AD converter.

[0069] In this embodiment, the method for the control unit to calculate the actual value of the power frequency current includes: S201 samples the output signals of the low-frequency amplifier circuit and the high-frequency amplifier circuit respectively; n points are sampled in each cycle, and m cycles constitute one frame.

[0070] This invention employs a dual-level parallel amplification architecture, with two amplification circuits simultaneously outputting signals with different gains. To ensure the accuracy of automatic routing and the continuity of current measurement, the two signals must be sampled completely synchronously. If there is a time difference between the two samplings, when the current changes rapidly, the sampled values ​​of the lower-level channel and the higher-level channel will correspond to different current moments, leading to errors in the automatic routing logic and even current value jumps.

[0071] The number of sampling points per cycle, n=80, corresponds to a 50Hz power frequency cycle, with a sampling frequency of 4kHz. The number of cycles per frame, m=2, means that each frame contains 2 consecutive power frequency cycles, for a total of 160 sampling points. Using 2 cycles per frame can effectively suppress random noise interference within a single cycle and improve measurement stability.

[0072] Slot cycle = 250ms, one frame of data is acquired and processed every 250ms, and 4 frames of data can be processed per second. Publish cycle = 1s, the average value of 4 frames of data is summarized every 1 second and published via RS485 bus.

[0073] S202 calculates the average value of n*m sampling points in each frame as the DC component, and subtracts the DC component from each sampling point to obtain the AC component.

[0074] In practical circuits, a slowly changing DC component is always superimposed on the sampled signal. If this DC component is not eliminated and the effective value is calculated directly, the measurement result will be severely overestimated. For example, a 100mV DC bias will cause the measurement error of a small current of 0.5A to exceed 20%, which completely fails to meet the accuracy requirements.

[0075] This embodiment uses the average value per frame as a correction method for the DC component, calculating the arithmetic mean of 160 sampling points in one frame. Subtracting this average value from each sampling point yields the pure AC component.

[0076] The DC component is recalculated for each frame, enabling real-time tracking of slowly changing DC interference such as reference voltage drift and op-amp offset drift.

[0077] S203 calculates the effective value of the AC component and converts the effective value of the AC component into the actual current value through a piecewise linear fitting table.

[0078] In electrical measurements, the effective value is a standard quantity that reflects the equivalent heating capacity of the current. For non-sinusoidal distorted currents, neither the peak value nor the average value can accurately reflect their actual harm; only the effective value can truly reflect the degree of thermal damage that the current causes to the cable insulation and grounding system.

[0079] Traditional algorithms often use the peak value divided by √2 to calculate the effective value, but this method is only applicable to ideal sinusoidal waves. For non-sinusoidal currents containing harmonics, this method will produce a large error. For example, for a current containing 30% third harmonics, the effective value calculated using the peak value method will have an error exceeding 10%.

[0080] This embodiment uses the discrete RMS calculation formula, which does not rely on any waveform assumptions and can accurately calculate the current for any waveform.

[0081] Because the linearity of the current transformer, sampling resistor, and amplifier circuit is not perfect across the entire measurement range, a certain degree of nonlinear error exists. To further improve measurement accuracy, this algorithm uses a piecewise linear fitting method to correct the RMS value.

[0082] First, using a high-precision standard current source, select 20 calibration points within the range of 0-70A, and record the RMS AD value and the actual current value corresponding to each calibration point.

[0083] The full measurement range was divided into two intervals: 0-5A and 5-70A. Linear fitting was performed on the calibration points of each interval, resulting in two linear equations. By using piecewise linear fitting, the measurement error across the entire range can be reduced.

[0084] S204 determines whether the low-frequency amplifier circuit is saturated. If it is saturated, it outputs the current value corresponding to the high-frequency amplifier circuit; otherwise, it outputs the current value corresponding to the low-frequency amplifier circuit.

[0085] Prioritize lower-gain channels to ensure signal integrity without signal overflow. Lower-gain channels offer higher gain, resulting in better AD resolution utilization and measurement accuracy. Only switch to higher-gain channels when the lower-gain channels are saturated.

[0086] Because the two signals are sampled synchronously and processed simultaneously, the automatic path selection process is completely seamless. After each frame of data is processed, the current values ​​corresponding to the low-end and high-end channels are obtained simultaneously. Based on the saturation judgment result, one of the current values ​​is selected as the final output. There is no data interruption or jump during the switching process, ensuring the continuity of current monitoring.

[0087] III. Full-range linear temperature monitoring unit: The full-temperature-range linear temperature monitoring unit is used to monitor the operating temperature across the entire temperature range at the termination point of railway signal cables. Specifically, the full-temperature-range linear temperature monitoring unit includes a temperature sensor, a first upper resistor, a second upper resistor, a first MOSFET, a second MOSFET, and an operational amplifier circuit. The first MOSFET and the first upper resistor are connected in series to form a first voltage divider branch, and the second MOSFET and the second upper resistor are connected in series to form a second voltage divider branch. The first and second voltage divider branches are connected in parallel between the power supply and the voltage divider node. The temperature sensor is connected between the voltage divider node and ground. The voltage divider node is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the control unit. The control terminals of the first MOSFET and the second MOSFET are respectively connected to the control unit; the control unit controls the on / off state of the first MOSFET and the second MOSFET according to the collected temperature value, switches the resistance value of the upper resistor connected to the voltage divider circuit, corrects the nonlinear temperature acquisition curve of the temperature sensor, and realizes full-temperature monitoring.

[0088] Abnormal temperatures at cable terminations are the most direct early sign of electrical faults. Poor contact leads to increased contact resistance, generating Joule heating when current flows; insulation aging leads to increased leakage current, also causing localized heating. This embodiment uses an NTC thermistor as the temperature sensor, which has the advantages of high sensitivity, small size, low cost, and fast response speed, making it the preferred sensing element for industrial temperature monitoring. The NTC thermistor is directly fastened to the steel strip or aluminum sheath grounding bolt at the cable termination using M4 stainless steel bolts, ensuring tight contact with the measured metal surface and guaranteeing efficient heat conduction. The sensor leads use high-temperature shielded wire, adaptable to different field installation requirements.

[0089] Current technologies generally employ piecewise linear fitting software to correct the nonlinearity error of NTCs. However, this method can only reduce the error to a certain extent and cannot fundamentally solve the problem of insufficient resolution in high-temperature regions. For example, when the temperature rises from 100℃ to 200℃, the NTC resistance decreases from 1.3kΩ to 100Ω, and the corresponding voltage drop is only 0.2V. A 12-bit AD converter can only resolve about 250 graduations, averaging one graduation every 4℃, which is completely insufficient to meet monitoring requirements.

[0090] This invention employs two completely independent parallel voltage divider branches. By switching the upper resistors with different values, the voltage division ratio is changed, thereby achieving a sufficiently large voltage variation range across different temperature ranges and fully utilizing the resolution of the AD converter. Both branches share the same NTC thermistor, and the upper resistor is selected by switching the MOSFET on and off, ensuring that the divided voltage covers most of the dynamic range of the AD converter in any temperature range.

[0091] Both MOSFETs are used as contactless electronic switches, with their gates connected to two general-purpose I / O ports of the MCU. When the MCU outputs a high level, the MOSFETs are turned on, and the corresponding branch is connected to the voltage divider circuit; when the output is low, the MOSFETs are turned off, and the corresponding branch is disconnected.

[0092] Furthermore, the input impedance of an MCU's AD converter is typically in the MΩ range, while the output impedance of a voltage divider circuit can drop to several hundred ohms in high-temperature regions. If the voltage divider node is directly connected to the AD port, the AD input impedance will be in parallel with the NTC resistor, leading to errors in the voltage division result. The op-amp voltage follower acts as an impedance transformer, possessing extremely high input impedance (≥1GΩ) and extremely low output impedance (≤1Ω), completely isolating the voltage divider circuit from the AD input impedance and ensuring the accuracy of the voltage division result.

[0093] In this embodiment, the method for the control unit to monitor the operating temperature includes: S301 collects the average temperature output from the operational amplifier circuit using an AD converter.

[0094] Strong electromagnetic interference exists at railway sites, which can couple into the temperature acquisition circuit, causing random spikes in single AD sampling values. Directly using single sampling values ​​for temperature calculations results in frequent temperature reading jumps and extremely poor stability.

[0095] Multiple sampling averaging is the simplest and most effective digital filtering method, which can effectively suppress random noise interference and improve measurement stability. Its principle is that the average value of random noise is 0; by sampling multiple times and averaging, the influence of noise can be reduced.

[0096] S302 uses a dual-section segmented fitting method to convert AD values ​​into temperature values. The low-temperature zone uses a low-level fitting table, while the high-temperature zone uses a high-level fitting table.

[0097] The voltage change rate of an NTC thermistor has an exponential relationship with temperature; the higher the temperature, the smaller the voltage change rate. When the voltage change rate is less than the resolution of the A / D converter, the measurement error increases dramatically.

[0098] This invention employs a 12-bit AD converter with a resolution of 3.3V / 4096≈0.8mV. The optimal boundary for the dual-zone division is determined by calculating the voltage change rate at different temperatures.

[0099] In the low-temperature range (-40℃~70℃), the NTC resistance value decreases from 200kΩ to 1.8kΩ. When using a 10kΩ upper resistor, the voltage change rate decreases from 15mV / ℃ to 0.9mV / ℃, which is always greater than the AD resolution.

[0100] In the high-temperature range (70℃~200℃), the NTC resistance value decreases from 1.8kΩ to 100Ω. When using a 1kΩ upper resistor, the voltage change rate decreases from 1.2mV / ℃ to 0.7mV / ℃, which is still greater than the AD resolution.

[0101] Therefore, choosing 70℃ as the dual-zone switching boundary ensures that the voltage change rate is always greater than or close to the resolution of the AD converter throughout the entire temperature range, thus fundamentally solving the problem of insufficient resolution in the high-temperature zone.

[0102] Piecewise fitting tables can be obtained through laboratory calibration.

[0103] During operation, the MCU reads the valid AD value of the current slot. Based on the currently connected upper resistor branch, it selects the corresponding fitting table. If the first branch (10kΩ upper resistor) is conducting, the low-temperature fitting table is used; if the second branch (1kΩ upper resistor) is conducting, the high-temperature fitting table is used. Substituting the AD value into the corresponding linear equation, the temperature value is calculated.

[0104] When the S303 detects that the temperature has reached the cutoff boundary, it uses the method of determining the current slot and then taking effect in the next slot to complete the upper resistor switching.

[0105] If an instantaneous switching method is used, where the MOSFET is switched immediately upon detecting that the temperature has reached the switching boundary, the switching resistor will cause a sudden jump in the voltage divider, resulting in a step change in the AD value. This will be reflected in the temperature reading as a sudden jump of several degrees Celsius, severely affecting the continuity of monitoring. When the temperature fluctuates near the switching point, the MOSFET will frequently switch on and off, causing frequent temperature reading jumps and extremely poor system stability. If the MOSFET is switched during AD sampling, the sampled value will be invalid, generating erroneous data.

[0106] In this embodiment, the slot switching operation is synchronized with the slot cycle, and the switching is performed during the interval between two slot cycles, without affecting the complete sampling process of any slot.

[0107] Specifically, in the last 10ms of each tank cycle, the AD value of this tank is acquired, averaged, and the temperature is calculated. Based on the calculated temperature value, it is determined whether to switch the upper resistor branch. If the current setting is low temperature and the temperature is ≥70℃, it is determined that it needs to switch to high temperature. If the current setting is high temperature and the temperature is ≤65℃, it is determined that it needs to switch to low temperature.

[0108] During the gap between the end of the current slot cycle and the start of the next slot cycle, a MOSFET switching operation is performed. The MCU outputs a low level until the first branch of Q1's gate is cut off, and outputs a high level until the second branch of Q2's gate is turned on. The MCU outputs a low level until the second branch of Q2's gate is cut off, and outputs a high level until the first branch of Q1's gate is turned on.

[0109] After the MOSFET switching is completed, temperature acquisition for the next cell begins, and calculations are performed using the new upper resistor branch and the corresponding fitting table.

[0110] IV. Threshold-adjustable arc monitoring unit: The threshold-adjustable arc monitoring unit is used to monitor early latent arc faults at the termination of railway signal cables and issue early warnings. Specifically, the threshold-adjustable arc monitoring unit includes a high-pass active filter, a high-speed window comparator, and a second-order RC filter circuit. The input terminal of the high-pass active filter is connected to the output terminal of the power frequency current acquisition unit, the output terminal of the high-pass active filter is connected to the input terminal of the high-speed window comparator, the PWM output port of the control unit is connected to the second-order RC filter circuit, the output terminal of the second-order RC filter circuit is connected to the threshold input terminal of the high-speed window comparator, and the output terminal of the high-speed window comparator is connected to the control unit. The control unit adjusts the duty cycle of the output PWM wave, generates a dynamically adjustable DC threshold voltage through a second-order RC filter circuit, and controls the detection threshold of the high-speed window comparator; the control unit counts the arc pulses output by the high-speed window comparator, thereby identifying and warning of arc faults.

[0111] The current signal in the grounding loop mainly consists of a 50Hz power frequency fundamental wave and low-order harmonics, with amplitudes much larger than the arc signal. If the mixed signal is directly fed into the window comparator, the power frequency signal will completely drown out the arc signal, making it impossible to detect the arc. The core function of the high-pass active filter is to filter out the 50Hz power frequency fundamental wave and low-order harmonic interference below 10kHz, retaining only the high-frequency pulse signal above 10kHz generated by the arc discharge, thus significantly improving the signal-to-noise ratio.

[0112] The high-frequency pulses generated by electric arc discharge are transient signals with extremely short durations, which ordinary comparators cannot accurately capture. High-speed window comparators can detect both the upper and lower limits of the signal simultaneously, and only output a pulse signal when the signal amplitude exceeds a set threshold range, making them ideal devices for detecting high-frequency pulses from electric arcs.

[0113] Traditional arc monitoring devices use a fixed resistor voltage divider to set the comparator threshold, which cannot be dynamically adjusted according to the field environment. In environments with strong electromagnetic interference, a fixed threshold that is too low will lead to frequent false alarms; a threshold that is too high will miss early, weak arcs. The second-order RC filter circuit in this embodiment converts the PWM wave output by the MCU into a smooth DC voltage, which serves as the upper and lower thresholds of the window comparator. By adjusting the duty cycle of the PWM wave, the threshold voltage can be dynamically adjusted in real time to adapt to different electromagnetic environments.

[0114] The MCU adjusts the threshold voltage in real time based on the following two factors: First, the background noise level. During the low-load period in the early morning each day, the system automatically learns one minute of background noise and sets a base threshold based on the noise level. Second, the current power frequency current amplitude. The amplitude of the fault arc is positively correlated with the power frequency current. The larger the power frequency current, the higher the threshold. This dynamic adjustment mechanism ensures both the sensitivity of detecting weak arcs and effectively suppresses false alarms caused by electromagnetic interference.

[0115] In this embodiment, the method for the control unit to identify and warn of arc faults includes: The S401 uses an external interrupt to count the number of pulse edges output by the high-speed window comparator within a natural second.

[0116] Arc pulses are transient signals with extremely short durations. If traditional polling sampling methods are used, the polling period is typically tens of microseconds to milliseconds, resulting in the loss of a large number of microsecond-level arc pulses. Furthermore, polling consumes significant computing resources, affecting the sampling and processing of other channels.

[0117] In this embodiment, an external interrupt is used to capture transient pulses. When the high-speed window comparator outputs a pulse edge, it will immediately trigger the external interrupt of the MCU. The processor will pause the current task to execute the interrupt service routine, complete the pulse counting, and ensure that no valid pulse is lost.

[0118] S402 reads and clears the pulse count every second. When the count reaches a preset threshold, it determines that an arc warning has been issued and accumulates the arc count.

[0119] The pulse frequency of a real fault arc is typically between 10 and 100 pulses per second, while the pulse frequency of common interferences in railway operations, such as motor starting and stopping, switch operations, and electromagnetic radiation, is usually below 10 pulses per second. For example, this study sets 14 pulses per second as the basic warning threshold. When the pulse count per second is ≥14, it is judged as a suspected arc event; when the pulse count per second is <14, it is judged as normal interference and no warning is triggered.

[0120] The base threshold is not fixed; the MCU automatically adjusts it based on the real-time background noise level. When the background noise pulse count is <5 times / second, the threshold remains at 14 times / second. When the background noise pulse count is between 5 and 10 times / second, the threshold increases to 20 times / second. When the background noise pulse count is >10 times / second, the threshold increases to 30 times / second, and a warning message indicating severe electromagnetic interference is reported.

[0121] This embodiment employs a cumulative counting-based hierarchical early warning mechanism: Level 1 warning: If the pulse count is greater than or equal to the threshold for 1 consecutive second, the cumulative arc count is incremented by 1, and a suspected arc warning is reported to remind maintenance personnel to pay attention.

[0122] Level 2 warning: If the cumulative arc count is ≥3 within 3 consecutive seconds, the arc fault information will be reported and an audible and visual alarm will be triggered.

[0123] Fault lockout: If the cumulative arc count is ≥10 within 10 consecutive seconds, the fault status is locked until the maintenance personnel manually reset it.

[0124] After the S403 arc is triggered, the lightning peak value release window is temporarily blocked to reduce crosstalk between the arc and lightning events.

[0125] When a Level 1 arc warning is detected, a shielding mechanism is immediately triggered, only disabling the event publishing function of the lightning peak monitoring unit; its normal data acquisition and processing are not affected. It is important to note that lightning is only shielded when an arc is triggered, not when a lightning strike is triggered.

[0126] During the shielding period, the lightning strike peak monitoring unit continues to collect data normally, but does not release any lightning strike event information. After the shielding ends, the MCU will perform retrospective analysis on the lightning strike data collected during the shielding period.

[0127] V. Hardware Architecture: like Figures 3-5 As shown, the above four functional modules are all integrated on the PCB board 5. In addition, it also includes the module housing 1 and the power supply circuit. The lightning peak monitoring unit, the wide range power frequency current acquisition unit, the full temperature range linear temperature monitoring unit except for the temperature sensor, the threshold adjustable arc monitoring unit and the control unit are all integrated in the module housing 1. The control unit is electrically connected to the power supply circuit. The module housing 1 has a pre-drilled hole 2 for the grounding wire 100 to pass through, and the Rogowski coil 9 is arranged around the hole 2. The top of the module housing 1 is provided with a temperature sensor external interface 4. The temperature sensor is fixed to the steel strip or aluminum sheath grounding bolt at the end of the cable and is electrically connected to the full-temperature-range linear temperature monitoring unit through the temperature sensor external interface 4. The module housing 1 is also provided with at least two integrated interfaces 3, which are connected to both the power supply circuit and the communication circuit; the terminal monitoring module is connected to the upper and lower level terminal monitoring modules respectively through the two integrated interfaces 3. The module housing 1 is provided with a buckle for connecting with the guide rail 200; the buckle includes a fixed block 6 and a sliding block 7 arranged opposite to each other, and the sliding block 7 can move towards the fixed block 6 under the action of the pre-tightening spring 8, thereby clamping the guide rail 200.

[0128] Example 2: like Figure 6 As shown, the present invention also provides a railway signal cable termination monitoring system, including a monitoring host and multiple termination monitoring modules. Each termination monitoring module is cascaded in a daisy-chain manner through an integrated interface and connected to the monitoring host.

[0129] During on-site installation, the grounding wire to be tested is passed sequentially through the wiring holes of each terminal monitoring module, and the NTC thermistor is secured to the corresponding grounding bolt. The input interface of the first module is connected to the on-site 12V-24V DC power supply and the RS485 bus of the back-end monitoring host. The input interfaces of each subsequent module are connected to the output interfaces of the previous module, forming a cascaded network.

[0130] Each terminal monitoring module has a unique slave address. The background monitoring host collects monitoring data from each module through polling, including power frequency current, temperature, lightning peak value, and arc status. The system supports real-time data display, historical data query, fault alarm, and report generation, enabling centralized monitoring and intelligent operation and maintenance of the terminal status of railway signal cables.

[0131] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0132] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a computer terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0133] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. An end-of-life monitoring module, characterized by, include: Lightning peak current monitoring unit is used to monitor the peak lightning current at the termination of railway signal cables; Wide-range power frequency current acquisition unit is used to monitor the wide-range power frequency fault current of the grounding circuit at the end of railway signal cables; A full-temperature-range linear temperature monitoring unit is used to monitor the operating temperature of railway signal cables across the entire temperature range at the termination point. The threshold adjustable arc monitoring unit is used to monitor early latent arc faults at the termination of railway signal cables and issue early warnings.

2. An end-of-run monitoring module according to claim 1, wherein, The lightning peak monitoring unit uses a Rogowski coil mounted on the ground wire as a sensing element. The output of the Rogowski coil is connected in sequence to a reference lift circuit, an RC integral circuit, a precision full-wave rectifier circuit, and a peak hold circuit. The output of the peak hold circuit is connected to a control unit. The differential signal generated by the lightning strike current induced by the Rogowski coil is raised by the reference lifting circuit, restored to the original lightning strike current waveform by the RC integrating circuit, converted into a unipolar signal by the precision full-wave rectifier circuit, and then the peak voltage is maintained by the peak holding circuit for acquisition by the control unit, so as to obtain the peak value of the lightning strike current through the control unit calculation.

3. An end-of-run monitoring module according to claim 2, wherein, The method for calculating the peak lightning current in the control unit includes: The peak voltage induced by the Rogowski coil is acquired through a peak hold circuit. Quantile statistics were performed on each frame of lightning strike sampling data to obtain the first quantile, the second quantile, and the third quantile; The difference between the third quantile and the first quantile is used as the platform flatness criterion, and combined with continuous p-frame data to confirm and prevent false triggering; After a valid lightning strike event is determined, the peak lightning current is released, and a clear pulse is generated to reset the peak holding circuit.

4. The end-of-line monitoring module according to claim 1, characterized in that, The wide-range power frequency current acquisition unit includes a power frequency transformer, a reference rise circuit, a sampling resistor, and a dual-range AC amplifier circuit. The secondary output terminal of the power frequency transformer is connected to the reference rise circuit. After being converted into a voltage signal by the sampling resistor, the signal is sent to the dual-range AC amplifier circuit. The output terminal of the dual-range AC amplifier circuit is connected to the control unit. The power frequency transformer senses and collects the power frequency current of the grounding circuit. The secondary side of the transformer outputs a standard small current signal after attenuation, which is converted into a corresponding voltage signal by a high-precision sampling resistor. After being synchronously conditioned by a dual-range amplifier circuit, it is sent to the control unit for acquisition, so that the actual value of the power frequency current can be obtained by the control unit.

5. The end-of-line monitoring module according to claim 4, characterized in that, The dual-range AC amplifier circuit includes a low-range power frequency amplifier circuit and a high-range power frequency amplifier circuit. The input terminals of the two amplifier circuits are connected in parallel to the output terminals of the sampling resistor, and the output terminals are respectively connected to different acquisition ports of the control unit. The low-range power frequency amplifier circuit is used to amplify small current signals of 0.5A-5A, and the high-range power frequency amplifier circuit is used to amplify large current signals of 5A-70A.

6. The end-of-line monitoring module according to claim 5, characterized in that, The method for the control unit to calculate the actual value of the power frequency current includes: The output signals of the low-frequency amplifier circuit and the high-frequency amplifier circuit are sampled separately; n points are sampled in each cycle, and m cycles constitute one frame. The average value of n*m sampling points in each frame is taken as the DC component, and the AC component is obtained by subtracting the DC component from each sampling point; Calculate the effective value of the AC component, and convert the effective value of the AC component into the actual current value through a piecewise linear fitting table; Determine if the low-frequency amplifier circuit is saturated. If it is saturated, output the current value corresponding to the high-frequency amplifier circuit; otherwise, output the current value corresponding to the low-frequency amplifier circuit.

7. The terminal monitoring module according to claim 1, characterized in that, The full-temperature-range linear temperature monitoring unit includes a temperature sensor, a first upper resistor, a second upper resistor, a first MOSFET, a second MOSFET, and an operational amplifier circuit. The first MOSFET and the first upper resistor are connected in series to form a first voltage divider branch, and the second MOSFET and the second upper resistor are connected in series to form a second voltage divider branch. The first and second voltage divider branches are connected in parallel between the power supply and the voltage divider node. The temperature sensor is connected between the voltage divider node and ground. The voltage divider node is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the control unit. The control terminals of the first MOSFET and the second MOSFET are respectively connected to the control unit; the control unit controls the on / off state of the first MOSFET and the second MOSFET according to the collected temperature value, switches the resistance value of the upper resistor connected to the voltage divider circuit, corrects the nonlinear temperature acquisition curve of the temperature sensor, and realizes full-temperature monitoring.

8. The terminal monitoring module according to claim 7, characterized in that, Methods for the control unit to monitor operating temperature include: Collect the average temperature output from the operational amplifier circuit (AD value); A two-section segmented fitting method was used to convert AD values ​​into temperature values, with a low-level fitting table used for the low-temperature region and a high-level fitting table used for the high-temperature region. When the temperature reaches the cutoff boundary, the upper resistor is switched by determining the current slot and then the next slot takes effect.

9. The terminal monitoring module according to claim 1, characterized in that, The threshold-adjustable arc monitoring unit includes a high-pass active filter, a high-speed window comparator, and a second-order RC filter circuit. The input terminal of the high-pass active filter is connected to the output terminal of the power frequency current acquisition unit, the output terminal of the high-pass active filter is connected to the input terminal of the high-speed window comparator, the PWM output port of the control unit is connected to the second-order RC filter circuit, the output terminal of the second-order RC filter circuit is connected to the threshold input terminal of the high-speed window comparator, and the output terminal of the high-speed window comparator is connected to the control unit. The control unit adjusts the duty cycle of the output PWM wave, generates a dynamically adjustable DC threshold voltage through a second-order RC filter circuit, and controls the detection threshold of the high-speed window comparator; the control unit counts the arc pulses output by the high-speed window comparator, thereby identifying and warning of arc faults.

10. The end-of-line monitoring module according to claim 9, characterized in that, The method for the control unit to identify and warn of arc faults includes: The number of pulse edges output by the high-speed window comparator within a natural second is counted using an external interrupt. The pulse count is read and cleared every second. When the count reaches a preset threshold, it is determined as an arc warning and the arc count is accumulated. After an electric arc is triggered, the peak lightning strike release window is temporarily blocked to reduce crosstalk between the electric arc and the lightning strike event.

11. The terminal monitoring module according to claim 1, characterized in that, It also includes a module housing and a power supply circuit; the lightning peak monitoring unit, the wide-range power frequency current acquisition unit, the full-temperature-range linear temperature monitoring unit (excluding the temperature sensor), the threshold adjustable arc monitoring unit, and the control unit are all integrated inside the module housing; the control unit is electrically connected to the power supply circuit. The module housing has a pre-drilled hole for the grounding wire to pass through. The top of the module housing is provided with an external interface for a temperature sensor. The temperature sensor is fixed to the grounding bolt of the steel strip or aluminum sheath at the end of the cable and is electrically connected to the full-temperature-range linear temperature monitoring unit through the external interface for the temperature sensor. The module housing is also provided with at least two integrated interfaces, which are connected to both the power supply circuit and the communication circuit; the terminal monitoring module is connected to the upper and lower level terminal monitoring modules respectively through the two integrated interfaces; The module housing is provided with a buckle for connecting with the guide rail; the buckle includes a fixed block and a sliding block arranged opposite each other, and the sliding block can move towards the fixed block under the action of a pre-tightening spring, thereby clamping the guide rail.

12. A railway signal cable termination monitoring system, characterized in that, It includes a monitoring host and multiple end-to-end monitoring modules as described in any one of claims 1 to 11. Each end-to-end monitoring module is cascaded in a daisy-chain manner through an integrated interface and connected to the monitoring host.

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