A data acquisition instrument for cathodic protection of natural gas pipelines

Abstract

The present invention relates to the technical field of natural gas pipeline protection, and more specifically, to a collector for cathodic protection of natural gas pipelines, comprising a pile body, a solar panel fixedly mounted on the top of the pile body, an equipment cavity defined within the pile body, a collector mounted within the equipment cavity, the collector electrically connected to an insulated wiring board, the input end of the insulated wiring board being connected to a polarization probe via an integrated wire assembly, the input end of the insulated wiring board also being connected to a pipeline cable, the other end of the pipeline cable being connected to the pipeline. A cathodic protection circuit, comprised of an AC potential test circuit, a DC potential test circuit, and a relay group circuit, is capable of measuring the AC interference voltage around the pipeline and the DC potential difference between the pipeline and a reference electrode, thereby providing comprehensive monitoring capabilities for the pipeline's cathodic protection status. Integrated signal processing algorithms and resistivity compensation algorithms improve the accuracy of collected data, thereby better reflecting the pipeline's true condition.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas pipeline protection, and in particular to a collector for cathodic protection of natural gas pipelines. Background Art

[0002] The cathodic protection data acquisition device is used to measure and record the power-on potential, natural potential, power-off potential, pipe-to-ground AC voltage, pipeline AC current density, pipeline DC current density, sacrificial anode open-circuit potential, and sacrificial anode protection current of pipeline cathodic protection in the field; by integrating multiple sensors, controllers, and communication modules, it can realize comprehensive monitoring of the cathodic protection system status, and use cloud computing and artificial intelligence technologies to process and analyze data, accurately judge the corrosion status of facilities, and provide a scientific basis for facility operation and maintenance; in recent years, with the rapid development of national modernization construction, ultra-high voltage transmission lines and towers, acid rain, urban rail transit 110KV transmission line modification, high-speed rail electrification tracks, signal base stations, highways and other facilities have caused buried steel pipelines to be greatly interfered with by AC and DC stray currents. Long-term interference corrosion of pipelines will cause hazards such as pipeline perforation and gas leakage.

[0003] At present, traditional test piles mainly rely on manual field multimeters to perform cathodic protection data detection. The collected data is single, inefficient, unreliable, and highly dangerous. The management of cathodic protection effects and daily patrols are extremely difficult, making it difficult to meet the increasing demand for cathodic protection data monitoring of long-distance pipelines. In view of this, a data collector for cathodic protection of natural gas pipelines is provided. Summary of the Invention

[0004] The main purpose of the present invention is to provide a data collector for cathodic protection of natural gas pipelines, so as to solve the problem proposed in the related art that the current traditional test piles mainly rely on manual field multimeters to detect cathodic protection data, the collected data is single, the efficiency is low, the reliability is poor, the risk is high, the management of cathodic protection effects and daily patrols are extremely difficult, and it is difficult to meet the needs of more and more long-distance pipeline cathodic protection data monitoring.

[0005] To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a collector for cathodic protection of a natural gas pipeline, comprising a pile body, a solar panel fixedly mounted on the top of the pile body, an equipment cavity defined in the pile body, a collector mounted in the equipment cavity, the collector being electrically connected to an insulating wiring board, an input end of the insulating wiring board being connected to a polarization probe via an integrated wire assembly, the input end of the insulating wiring board being further connected to a pipeline cable, the other end of the pipeline cable being connected to a pipeline;

[0006] Among them, the integrated wire group includes sacrificial anode wire, long-term reference wire, AC test wire, polarization test wire and self-corrosion test wire.

[0007] Furthermore, the acquisition device includes:

[0008] An AD data acquisition unit, the AD data acquisition unit is used to collect voltage information in the cathode protection circuit, the cathode protection circuit is composed of an AC potential test circuit, a DC potential test circuit and a relay group circuit;

[0009] A wireless transmission module, which is used to transmit the collected data to a remote monitoring center wirelessly;

[0010] A positioning module, which is used to determine the specific location of the monitoring point;

[0011] The microprocessor unit is used to process information between the various unit modules and is integrated with a signal processing algorithm and a resistivity compensation algorithm to improve the accuracy of the collected data.

[0012] Furthermore, the AD data acquisition unit includes:

[0013] A collection unit, the collection unit is used to transmit the cathode voltage on the gas pipeline to the cathodic protection circuit;

[0014] A voltage sensor receives the cathode voltage of the analog signal from the acquisition unit at a certain sampling time interval, converts the cathode voltage of the analog signal into a digital signal through the ADC, and sends the digital signal to the first input terminal of the comparator;

[0015] a voltage module, the voltage module being configured to send the received reference voltage to the second input terminal of the comparator;

[0016] A comparator, the comparator being configured to compare a cathode voltage received at a first input terminal with a reference voltage received at a second input terminal, and to issue an alarm signal through an output terminal if the cathode voltage is higher than the reference voltage, and to loop and wait for the next acquisition and comparison if the cathode voltage is equal to or lower than the reference voltage;

[0017] An alarm signal transmitter is used to send an alarm signal wirelessly.

[0018] Furthermore, in the cathode protection circuit:

[0019] The AC potential test circuit is used to measure the AC interference voltage in the soil around the pipeline;

[0020] The DC potential test circuit is used to measure the DC potential difference between the pipeline and the reference electrode;

[0021] The relay group circuit is used to control and switch different test modes or disconnect certain circuits when an abnormality is detected to protect the equipment from damage.

[0022] The relay group circuit changes state according to the instructions of the microprocessor unit, thereby adjusting the cathodic protection system or isolating the faulty part.

[0023] Furthermore, the AC potential test circuit includes an operational amplifier U64, wherein the input terminal VIN of the operational amplifier U64 is connected to a capacitor C234, a capacitor C235 and a resistor R328, wherein one end of the capacitor C234 is connected to the cathode of the diode D3, and the anode of the diode D3 is connected to the -5V input voltage, one end of the capacitor C235 is connected to the anode of the diode D4, and the cathode of the diode D4 is connected to the +5V input voltage, and the common node of the capacitors C234 and C235 serves as an input terminal for receiving a current test signal, and the other end of the capacitor C234 shares a node with C235 and is connected to the input terminal VIN of the operational amplifier; a clamping circuit is formed by diodes D3 and D4 to protect the input terminal of the operational amplifier U64, and the common node of C234 and C235 is used to receive a current test signal.

[0024] The OUTPUT terminal of the operational amplifier U64 is connected to a resistor R329 and a capacitor C238, the other end of the capacitor C238 is grounded, and a common node of the resistor R329 and the capacitor C238 is used as an AC potential output;

[0025] Resistor R329 acts as a load resistor, converting the output signal of operational amplifier U64 into a voltage signal for adjusting the output signal amplitude and impedance matching. Capacitor C238 provides a high-frequency bypass at the output of operational amplifier U64 to improve the quality and stability of the output signal. It helps eliminate high-frequency noise and ensures the accuracy of the output signal.

[0026] The -VS terminal of the operational amplifier U64 is connected to a capacitor C239, the other end of which is grounded, and a capacitor C241 is connected to a common node between the capacitor C239 and the -VS terminal, the other end of which is connected to the CAV terminal of the operational amplifier U64, and the negative electrode of the capacitor C241 is connected to a -5V input voltage;

[0027] Capacitor C239 is used to provide power decoupling to reduce noise and ripple on the power line and ensure the stable power supply required for the normal operation of the operational amplifier. The other end of capacitor C239 is grounded, which can absorb high-frequency noise from the power supply and prevent such noise from interfering with the internal operation of the operational amplifier.

[0028] The other end of capacitor C241 is connected to the -5V input voltage. Capacitor C241 is used to further stabilize the power supply and also to suppress the noise of the internal circuit of the operational amplifier. The CAV terminal represents the bias voltage of the operational amplifier. The voltage of this terminal determines the operating point of the operational amplifier.

[0029] The negative terminal of capacitor C241 is connected to the -5V input voltage, which means that the -VS terminal of operational amplifier U64 requires a stable -5V power supply to work properly;

[0030] The +VS terminal of the operational amplifier U64 is connected to a capacitor C236, the other end of the capacitor C236 is connected to the COM terminal of the operational amplifier U64, and the common node of the COM terminal and the capacitor C236 is grounded, and the common node of the capacitor C236 and the +VS terminal is connected to a +5V input voltage;

[0031] Capacitor C236 is used to provide power decoupling to reduce noise and ripple on the power line and ensure the stable power supply required for the normal operation of the operational amplifier. The common node of capacitor C236 and the COM terminal is grounded, which helps absorb high-frequency noise from the power supply and prevents such noise from interfering with the internal circuit of the operational amplifier. The common node of capacitor C236 and the +VS terminal is connected to the +5V input voltage, which requires a stable +5V power supply for the +VS terminal of the operational amplifier U64.

[0032] The Cc terminal of the operational amplifier U64 is connected to a capacitor C242 , and the other end of the capacitor C242 is grounded.

[0033] Furthermore, the DC potential test circuit includes a dual operational amplifier LM324, wherein a -IN terminal of the dual operational amplifier LM324 is connected to a pipeline, and a +IN terminal of the dual operational amplifier LM324 is connected to a current test signal;

[0034] The OUT terminal of the dual operational amplifier LM324 is connected to a resistor R327, and the other end of the resistor R327 serves as an output terminal of the current-to-potential signal;

[0035] The VS terminal of the dual operational amplifier LM324 is connected to a capacitor C231, one end of the capacitor C231 and a common node of the VS terminal are connected to a capacitor C233, and a +5V input voltage is connected to the common node of the capacitor C231 and the VS terminal, and the other end of the capacitor C231 and the other end of the capacitor C233 are commonly grounded;

[0036] The OFFSET terminal of the dual operational amplifier LM324 is connected to a resistor R301, the other end of which is connected to a +5V input voltage. A resistor R331 is connected to a common node between the OFFSET terminal and the resistor R301, and a capacitor C243 is connected to a common node between the resistor R331 and the resistor R301. The other end of the capacitor C243 is connected to a common ground with the resistor R331.

[0037] The GND terminal, A1 terminal and A2 terminal of the dual operational amplifier LM324 are grounded in common.

[0038] Furthermore, the relay group circuit includes a current test signal output circuit and a potential test signal output circuit;

[0039] Wherein, the current test signal output circuit includes relay K1, relay K1 and relay K3;

[0040] Contact 3 of relay K1 is connected to resistor R1, the other end of which is connected to resistor R2, the other end of which is connected to contact 5 of relay K1, and the common node of resistors R1 and R2 is connected to the pipeline. The purpose of connecting the common node of resistors R1 and R2 to the natural gas pipeline is to measure the AC interference voltage around the pipeline. Resistors R1 and R2 form a voltage divider, which is used to limit the current flowing into the pipeline to prevent excessive current from damaging the circuit or affecting the normal operation of the pipeline. At the same time, this voltage divider also allows weak AC signals to pass through, allowing the measuring equipment to capture changes in AC potential. When the contacts of relay K1 are closed, the voltage divider is connected to the circuit, thus realizing the AC potential measurement function.

[0041] The contact 4 of the relay K1 is connected to the contact 4 of the relay K3, and the contact 5 of the relay K3 is connected to the sacrificial anode, and the contact 3 of the relay K3 is connected to the contact 4 of the relay K2;

[0042] The contact 5 of the relay K2 is connected to the polarization test piece, and the contact 3 of the relay K2 is connected to the AC test piece.

[0043] Polarization test strips and AC test strips are important components used to monitor and evaluate the corrosion protection performance of natural gas pipelines. Polarization test strips simulate pipeline materials and are used to measure their electrochemical reactions under specific conditions, particularly the extent of redox reactions, to determine whether the pipeline is in good corrosion protection. AC test strips are used to detect the presence and intensity of AC interference voltage, as AC interference may affect the effectiveness of corrosion protection.

[0044] Relays K3 and K2 act as switches in the circuit, selectively connecting or disconnecting the polarization test strip, AC test strip, and sacrificial anode as needed. Sacrificial anodes are a commonly used corrosion prevention method that protects the pipeline by replacing the pipeline with another metal (such as magnesium or zinc) as the target of corrosion. When contact 5 of relay K3 is connected to the sacrificial anode, it monitors the working status of the sacrificial anode to ensure that it effectively consumes itself to protect the pipeline. Relay K2 is responsible for connecting the polarization test strip and AC test strip for related tests.

[0045] The relay group circuit can change state according to the instruction of the microprocessor unit, thereby realizing fast switching between different test modes, or disconnecting certain circuits when an abnormality is detected to protect the equipment from damage.

[0046] Furthermore, the potential test signal output circuit includes relay K4, relay K5, relay K6, relay K7, relay K8 and relay K9;

[0047] Among them, the contact 4 of the relay K4 is connected to the pipeline, the contact 4 of the relay K5 is connected to the polarized test piece, the contact 4 of the relay K6 is connected to the sacrificial anode, and the contact 4 of the relay K7 is connected to the natural test piece. The contacts 3 of the relay K4, relay K5 and relay K6 are connected in parallel;

[0048] The contacts 5 of the relays K4, K5, K6 and K7 are connected in parallel, and the parallel common node of the contacts 5 is connected to the contact 5 of the relay K8, and the contact 3 of the relay K8 serves as the output end of the current-to-potential signal;

[0049] The contact 4 of the relay K8 is connected to a resistor R3, the other end of the resistor R3 is connected to the contact 4 of the relay K9, the common node of the resistor R3 and the contact 4 of the relay K8 is connected to the contact 3 of the relay K9, and the contact 4 of the relay K9 serves as the output end of the potential test signal;

[0050] A common node between the resistor R3 and the contact 4 of the relay K9 is connected to a resistor R4 , and the other end of the resistor R4 is grounded.

[0051] Furthermore, the microprocessor unit receives the digital signal converted from the ADC, and uses a signal processing algorithm to identify and remove AC and DC stray current interference, and calibrates the effect of soil resistivity changes with temperature on the signal through a resistivity compensation algorithm;

[0052] The specific steps involved in the signal processing algorithm to remove AC stray current interference are:

[0053] The voltage signal in the cathodic protection circuit is collected for T seconds, and the sampling frequency is f sHz, the total number of sampling points is N;

[0054] Perform discrete Fourier transform on the collected voltage signal x[n] to obtain the frequency domain signal X[k];

[0055]

[0056] Calculate the amplitude of the spectrum |X[k]| to identify the interference frequency in the voltage signal;

[0057]

[0058] Where X[k] represents the kth component of the frequency domain signal, which is the spectral component of the discrete time signal x[n] at frequency k; k represents the frequency index; x[n] represents the nth sampling point of the time domain signal; n represents the time index; e -j2πkn / N represents a complex exponential function, represents a complex rotation factor at frequency k; j represents an imaginary unit, and j 2 =-1; |X[k]| represents the amplitude of the frequency domain signal X[k]; Re(X[k]) represents the real part of the frequency domain signal X[k]; Im(X[k]) represents the imaginary part of the frequency domain signal X[k];

[0059] A second-order band-stop filter is designed and applied to the original signal to remove the identified interference frequency. The transfer function of the second-order band-stop filter is:

[0060]

[0061] Where ω0 = 2πf0 represents the center angular frequency, f0 represents the center frequency; Q represents the quality factor, which determines the bandwidth and selectivity of the filter; ζ represents the damping ratio; and s represents the Laplace transform variable, which is used to describe the frequency characteristics of the filter.

[0062] Furthermore, the resistivity compensation algorithm is used to calibrate the effect of soil resistivity changes with temperature on the signal. The specific expression involved is:

[0063] ρ(T)=ρ0·[1+α·(T-T0)];

[0064] Where ρ(T) represents the soil resistivity at temperature T; ρ0 represents the soil resistivity at reference temperature t0; α represents the temperature coefficient of soil resistivity; T0 represents the reference temperature; T represents the currently measured soil temperature;

[0065] At the same time, considering the influence of humidity H and salinity S on soil resistivity, the calibrated soil resistivity ρ is obtained eff :

[0066] ρ eff=ρ0·[1+α·(T-T0)+β·(H-H0)+γ·(S-S0)];

[0067] Where β represents the humidity coefficient; γ represents the salinity coefficient; H0 represents the reference humidity; H represents the currently measured soil humidity; S0 represents the reference salinity; S represents the currently measured soil salinity;

[0068] And use the outlier detection method to calculate the invalid interference term Δρ eff , the final soil resistivity ρ(T, H, S) is obtained by removing the invalid interference terms:

[0069] ρ(T, H, S) = ρ eff -Δρ eff ;

[0070] ρ(T,H,S)=ρ0·[1+α·(T-T0)+β·(H-H0)+γ·(S-S0)]-Δρ eff .

[0071] The microprocessor unit reads the current temperature T, humidity H, and salinity S and the measured soil resistivity ρ(T, H, S), and then uses the resistivity compensation algorithm to calculate the corrected soil resistivity ρ(T, H, S). The values ​​of α, β, and γ depend on the specific composition of the soil and other environmental factors. Therefore, in actual application, α, β, and γ need to be determined through experimental data.

[0072] By calculating the corrected soil resistivity ρ(T, H, S), any changes or failures in the cathodic protection system, such as insufficient or excessive protection current, can be promptly detected, allowing necessary adjustments to be made. Accurate soil resistivity data helps maintain effective cathodic protection levels, avoiding corrosion caused by insufficient protection or material loss due to excessive protection, thereby extending the service life of natural gas pipelines.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] 1. In this data collector for cathodic protection of natural gas pipelines, online monitoring of cathodic protection of gas pipelines realizes real-time, wireless data transmission between each monitoring point and the monitoring center; intensively collects cathodic protection parameter data, and uploads the collected data to the monitoring center via 4G wireless transmission. The monitoring center receives the data and analyzes and processes the data, realizing real-time monitoring and prediction of the corrosion status of the gas pipeline, thereby improving the reliability and efficiency of the cathodic protection system.

[0075] 2. This data acquisition instrument for natural gas pipeline cathodic protection is equipped with a cathodic protection circuit consisting of an AC potential test circuit, a DC potential test circuit, and a relay group circuit. It can measure the AC interference voltage around the pipeline (AC potential test circuit) and the DC potential difference between the pipeline and the reference electrode (DC potential test circuit), thereby providing comprehensive monitoring capabilities for the pipeline's cathodic protection status.

[0076] Through the integrated signal processing algorithm and resistivity compensation algorithm, the accuracy of the collected data can be improved, thereby better reflecting the actual condition of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 This is a schematic diagram of the overall structure of the collector in a preferred embodiment of the present invention;

[0078] Figure 2 This is a schematic diagram of the acquisition instrument system module in a preferred embodiment of the present invention;

[0079] Figure 3 Schematic diagram of an AC potential test circuit in a preferred embodiment of the present invention;

[0080] Figure 4 Schematic diagram of a DC potential test circuit in a preferred embodiment of the present invention;

[0081] Figure 5 Schematic diagram of the relay group circuit in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0082] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0083] See also Figure 1-Figure 5 As shown, the purpose of this embodiment is to provide a collector for cathodic protection of natural gas pipelines, including a pile body 1, a solar panel 2 is fixedly installed on the top of the pile body 1, the solar panel 2 is used to power a collector 3, the device for the solar panel 2 to power the collector 3 also includes at least a battery, the solar panel power is ≥5W, and the solar battery capacity is ≥20Wh; an equipment cavity is opened in the pile body 1, and the collector 3 is installed in the equipment cavity. The collector 3 is electrically connected to an insulating terminal block 4, and the input end of the insulating terminal block 4 is connected to a polarization probe 5 through an integrated wire group 41. The input end of the insulating terminal block 4 is also connected to a pipeline cable, and the other end of the pipeline cable is connected to a pipeline 6;

[0084] The integrated wire group 41 includes a sacrificial anode wire, a long-term reference wire, an AC test wire, a polarization test wire, and a self-corrosion test wire, and the polarization probe 5 is buried around the pipeline.

[0085] The polarization probe 5 is provided with a polarization test piece, an AC test piece, a sacrificial anode test piece, a long-term reference test piece, and a self-corrosion test piece, and the above test pieces are buried in the soil around the pipeline 6;

[0086] Among them, the sacrificial anode wire is connected to the polarization test piece; the long-term reference wire is connected to the long-term reference test piece; the AC test piece wire is connected to the AC test piece; the polarization test piece wire is connected to the polarization test piece; and the self-corrosion test piece wire is connected to the self-corrosion test piece.

[0087] In soil or freshwater environments, a copper-saturated copper sulfate reference electrode (hereinafter referred to as saturated copper sulfate reference electrode, abbreviated as CSE) should be used. In soil environments, a high-purity zinc reference electrode (abbreviated as ZRE, purity not less than 99.995%) can also be used. This reference electrode needs to be coated with 75% gypsum, 20% bentonite, and 5% sodium sulfate backfill. The potential relative to the copper sulfate electrode -850mV is: +250mV (25°C), and the operating temperature should not exceed 60°C. In seawater environments, a silver-silver chloride reference electrode (abbreviated as SSC) is suitable.

[0088] In this embodiment, the cross-sectional area of ​​the AC test wire, long-term reference wire, pipeline cable, polarization test wire and solar panel 2 power supply cable should be ≥2.5mm 2 The standard length is 5 meters, which is convenient for welding and installation;

[0089] The collector 3 includes:

[0090] AD data acquisition unit, the AD data acquisition unit is used to collect voltage information in the cathodic protection circuit, the cathodic protection circuit is composed of an AC potential test circuit, a DC potential test circuit and a relay group circuit;

[0091] During long-term use, oil and gas pipelines are prone to corrosion due to environmental factors such as soil, moisture, and oxygen. Therefore, by applying electric current, a protective film is formed on the surface of the pipeline to prevent corrosion.

[0092] In the cathodic protection circuit, the long-term reference test piece uses a pre-packaged long-term copper sulfate reference electrode. The long-term reference electrode should be installed as close to the pipeline as possible, vertically buried, 0.1m from the exposed surface of the test piece, and 0.20-0.3m from the pipe wall. Before burial, the long-term reference electrode should be soaked in clean water for at least 12 hours to ensure sufficient moisture and good contact with the soil. The long-term reference electrode should be handled with care during installation to prevent rupture of the long-term reference electrode casing.

[0093] Specifically, the sacrificial anode test piece and the long-term reference test piece are buried at the same depth in the pipeline, 45 cm laterally along the pipeline, and the distance between the sacrificial anode test piece and the long-term reference test piece is 2-3 meters;

[0094] The AC test piece, polarization test piece, and self-corrosion test piece are placed about 10-20 cm around the long-term reference test piece, and the test pieces are spaced about 10-20 cm apart.

[0095] The pile body 1 is buried above the long-term reference test piece at a depth of 1 meter.

[0096] The AD data acquisition unit includes a cathodic protection test probe, including basic components such as a test piece and a reference electrode. The exposed area of ​​the test piece should be 1 to 50 cm 2 When the AC and DC stray current interference is low, the test piece area used to evaluate the effectiveness of cathodic protection can be selected according to the type of anti-corrosion layer; when evaluating the AC and DC interference level or evaluating the effectiveness of cathodic protection in the presence of AC and DC stray current interference, the test piece area should be 1cm 2 The area of ​​the self-corrosion test piece can be selected from 6.5 to 50 cm 2 ;Except for the exposed surface, the rest of the test piece should be well insulated against corrosion;The area and number of the selected test pieces should not affect the output current of the cathodic protection system;

[0097] A wireless transmission module is used to transmit the collected data to a remote monitoring center wirelessly, preferably using 4G full-network communication and TCP / IP communication protocol;

[0098] A positioning module is used to determine the specific location of the monitoring point using GPS or other positioning technologies;

[0099] A microprocessor unit, which is used to process information between the various unit modules and integrates a signal processing algorithm and a resistivity compensation algorithm to improve the accuracy of the collected data;

[0100] When the AC voltage is higher than 4V, there is interference, and a solid-state decoupler should be installed for drainage.

[0101] Wherein, the AD data acquisition unit includes:

[0102] A collection unit, the collection unit is used to transmit the cathode voltage on the gas pipeline to the cathodic protection circuit, and the collection unit is electrically connected to the gas pipeline through a cathodic protection cable;

[0103] A voltage sensor receives the cathode voltage of the analog signal from the acquisition unit at a certain sampling time interval, converts the cathode voltage of the analog signal into a digital signal through the ADC, and sends the digital signal to the first input terminal of the comparator;

[0104] a voltage module, the voltage module being configured to send the received reference voltage to the second input terminal of the comparator;

[0105] A comparator, the comparator being configured to compare a cathode voltage received at a first input terminal with a reference voltage received at a second input terminal, and to issue an alarm signal through an output terminal if the cathode voltage is higher than the reference voltage, and to loop and wait for the next acquisition and comparison if the cathode voltage is equal to or lower than the reference voltage;

[0106] The alarm signal transmitter is used to send out the alarm signal in a wireless form. The alarm signal transmitter is specifically a wireless transmitting device such as an RF antenna.

[0107] In this embodiment, in the cathode protection circuit:

[0108] The AC potential test circuit is used to measure the AC interference voltage in the soil around the pipeline;

[0109] The DC potential test circuit is used to measure the DC potential difference between the pipeline and the reference electrode;

[0110] The relay group circuit is used to control and switch different test modes or disconnect certain circuits when an abnormality is detected to protect the equipment from damage.

[0111] The relay group circuit changes state according to the instructions of the microprocessor unit, thereby adjusting the cathodic protection system or isolating the faulty part.

[0112] In this embodiment, in the cathode protection circuit:

[0113] The microprocessor unit triggers the AC potential test circuit and the DC potential test circuit to perform measurements according to a predetermined schedule or condition;

[0114] After the test circuit completes the measurement, it transmits the data back to the microprocessor unit for processing;

[0115] The microprocessor unit analyses the received data and determines whether the cathodic protection system is functioning properly based on pre-set criteria;

[0116] If an anomaly is detected, such as low or high cathode voltage, the microprocessor unit sends instructions to the relay bank circuit to adjust the settings of the cathodic protection system or, if necessary, shut down the system to prevent further damage;

[0117] At the same time, if the alarm condition is triggered, the alarm signal transmitter will start and send an alarm signal to the remote monitoring center.

[0118] In this embodiment, the AC potential test circuit includes an operational amplifier U64, wherein the input terminal VIN of the operational amplifier U64 is connected to a capacitor C234, a capacitor C235 and a resistor R328, wherein one end of the capacitor C234 is connected to the cathode of the diode D3, and the anode of the diode D3 is connected to the -5V input voltage, one end of the capacitor C235 is connected to the anode of the diode D4, and the cathode of the diode D4 is connected to the +5V input voltage, and the common node of the capacitors C234 and C235 serves as an input terminal for receiving a current test signal, and the other end of the capacitor C234 shares a node with C235 and is connected to the input terminal VIN of the operational amplifier; a clamping circuit is formed by diodes D3 and D4 to protect the input terminal of the operational amplifier U64, and the common node of C234 and C235 is used to receive a current test signal.

[0119] The OUTPUT terminal of the operational amplifier U64 is connected to a resistor R329 and a capacitor C238, the other end of the capacitor C238 is grounded, and a common node of the resistor R329 and the capacitor C238 is used as an AC potential output;

[0120] Resistor R329 acts as a load resistor to convert the output signal of operational amplifier U64 into a voltage signal for adjusting the amplitude and impedance matching of the output signal. Capacitor C238 provides a high-frequency bypass at the output of operational amplifier U64 to improve the quality and stability of the output signal, help eliminate high-frequency noise, and ensure the accuracy of the output signal.

[0121] The -VS terminal of the operational amplifier U64 is connected to a capacitor C239, the other end of which is grounded, and a capacitor C241 is connected to a common node between the capacitor C239 and the -VS terminal, the other end of which is connected to the CAV terminal of the operational amplifier U64, and the negative electrode of the capacitor C241 is connected to a -5V input voltage;

[0122] Capacitor C239 is used to provide power decoupling to reduce noise and ripple on the power line and ensure the stable power supply required for the normal operation of the operational amplifier. The other end of capacitor C239 is grounded, which can absorb high-frequency noise from the power supply and prevent such noise from interfering with the internal operation of the operational amplifier.

[0123] The other end of capacitor C241 is connected to the -5V input voltage. Capacitor C241 is used to further stabilize the power supply and also to suppress the noise of the internal circuit of the operational amplifier. The CAV terminal represents the bias voltage of the operational amplifier. The voltage of this terminal determines the operating point of the operational amplifier.

[0124] The negative terminal of capacitor C241 is connected to the -5V input voltage, which means that the -VS terminal of operational amplifier U64 requires a stable -5V power supply to work properly;

[0125] The +VS terminal of the operational amplifier U64 is connected to a capacitor C236, the other end of the capacitor C236 is connected to the COM terminal of the operational amplifier U64, and the common node of the COM terminal and the capacitor C236 is grounded, and the common node of the capacitor C236 and the +VS terminal is connected to a +5V input voltage;

[0126] Capacitor C236 is used to provide power decoupling to reduce noise and ripple on the power line and ensure the stable power supply required for the normal operation of the operational amplifier. The common node of capacitor C236 and the COM terminal is grounded, which helps absorb high-frequency noise from the power supply and prevents such noise from interfering with the internal circuit of the operational amplifier. The common node of capacitor C236 and the +VS terminal is connected to the +5V input voltage, which requires a stable +5V power supply for the +VS terminal of the operational amplifier U64.

[0127] The Cc terminal of the operational amplifier U64 is connected to a capacitor C242 , and the other end of the capacitor C242 is grounded.

[0128] The DC potential test circuit includes a dual operational amplifier LM324, wherein the -IN terminal of the dual operational amplifier LM324 is connected to the pipeline, and the +IN terminal of the dual operational amplifier LM324 is connected to the current test signal;

[0129] The OUT terminal of the dual operational amplifier LM324 is connected to a resistor R327, and the other end of the resistor R327 serves as an output terminal of the current-to-potential signal;

[0130] The VS terminal of the dual operational amplifier LM324 is connected to a capacitor C231, one end of the capacitor C231 and a common node of the VS terminal are connected to a capacitor C233, and a +5V input voltage is connected to the common node of the capacitor C231 and the VS terminal, and the other end of the capacitor C231 and the other end of the capacitor C233 are commonly grounded;

[0131] The OFFSET terminal of the dual operational amplifier LM324 is connected to a resistor R301, the other end of which is connected to a +5V input voltage. A resistor R331 is connected to a common node between the OFFSET terminal and the resistor R301, and a capacitor C243 is connected to a common node between the resistor R331 and the resistor R301. The other end of the capacitor C243 is connected to a common ground with the resistor R331.

[0132] The GND terminal, A1 terminal and A2 terminal of the dual operational amplifier LM324 are grounded in common.

[0133] The DC potential test circuit can accurately evaluate the effectiveness of cathodic protection by directly measuring the DC potential difference between the pipeline and the reference electrode, thereby ensuring that the pipeline is in the best anti-corrosion protection state. The DC potential test circuit is not affected by AC interference, so its measurement results are more reliable.

[0134] In this embodiment, the relay group circuit includes a current test signal output circuit and a potential test signal output circuit;

[0135] Wherein, the current test signal output circuit includes relay K1, relay K1 and relay K3;

[0136] Contact 3 of relay K1 is connected to resistor R1, the other end of which is connected to resistor R2, the other end of which is connected to contact 5 of relay K1, and the common node of resistors R1 and R2 is connected to the pipeline. The purpose of connecting the common node of resistors R1 and R2 to the natural gas pipeline is to measure the AC interference voltage around the pipeline. Resistors R1 and R2 form a voltage divider, which is used to limit the current flowing into the pipeline to prevent excessive current from damaging the circuit or affecting the normal operation of the pipeline. At the same time, this voltage divider also allows weak AC signals to pass through, allowing the measuring equipment to capture changes in AC potential. When the contacts of relay K1 are closed, the voltage divider is connected to the circuit, thus realizing the AC potential measurement function.

[0137] The contact 4 of the relay K1 is connected to the contact 4 of the relay K3, and the contact 5 of the relay K3 is connected to the sacrificial anode, and the contact 3 of the relay K3 is connected to the contact 4 of the relay K2;

[0138] The contact 5 of the relay K2 is connected to the polarization test piece, and the contact 3 of the relay K2 is connected to the AC test piece.

[0139] Polarization test strips and AC test strips are important components used to monitor and evaluate the corrosion protection performance of natural gas pipelines. Polarization test strips simulate pipeline materials and are used to measure their electrochemical reactions under specific conditions, particularly the extent of redox reactions, to determine whether the pipeline is in good corrosion protection. AC test strips are used to detect the presence and intensity of AC interference voltage, as AC interference may affect the effectiveness of corrosion protection.

[0140] Relays K3 and K2 act as switches in the circuit, selectively connecting or disconnecting the polarization test strip, AC test strip, and sacrificial anode as needed. Sacrificial anodes are a commonly used corrosion prevention method that protects the pipeline by replacing the pipeline with another metal (such as magnesium or zinc) as the target of corrosion. When contact 5 of relay K3 is connected to the sacrificial anode, it monitors the working status of the sacrificial anode to ensure that it effectively consumes itself to protect the pipeline. Relay K2 is responsible for connecting the polarization test strip and AC test strip for related tests.

[0141] The relay group circuit can change state according to the instruction of the microprocessor unit, thereby realizing fast switching between different test modes, or disconnecting certain circuits when an abnormality is detected to protect the equipment from damage.

[0142] In this embodiment, the potential test signal output circuit includes relay K4, relay K5, relay K6, relay K7, relay K8 and relay K9;

[0143] Among them, the contact 4 of the relay K4 is connected to the pipeline, the contact 4 of the relay K5 is connected to the polarized test piece, the contact 4 of the relay K6 is connected to the sacrificial anode, and the contact 4 of the relay K7 is connected to the natural test piece. The contacts 3 of the relay K4, relay K5 and relay K6 are connected in parallel;

[0144] The contacts 5 of the relays K4, K5, K6 and K7 are connected in parallel, and the parallel common node of the contacts 5 is connected to the contact 5 of the relay K8, and the contact 3 of the relay K8 serves as the output end of the current-to-potential signal;

[0145] The contact 4 of the relay K8 is connected to a resistor R3, the other end of the resistor R3 is connected to the contact 4 of the relay K9, the common node of the resistor R3 and the contact 4 of the relay K8 is connected to the contact 3 of the relay K9, and the contact 4 of the relay K9 serves as the output end of the potential test signal;

[0146] A common node between the resistor R3 and the contact 4 of the relay K9 is connected to a resistor R4 , and the other end of the resistor R4 is grounded.

[0147] Specifically, the specific functions of the microprocessor unit are:

[0148] It is responsible for starting the AD data acquisition unit and controlling the acquisition time interval;

[0149] Used to trigger the voltage sensor to sample;

[0150] It receives digital signals converted from the ADC and uses a signal processing algorithm to identify and remove sources of AC interference. The signal processing algorithm can quickly identify abnormal signals and trigger an alarm mechanism. The microprocessor unit can trigger the alarm mechanism based on pre-programmed logic, promptly notifying maintenance personnel to conduct inspections and repairs, avoiding the escalation of problems caused by delays. Because the signal processing algorithm can effectively remove interference signals, it reduces false alarms caused by interference and improves the stability and reliability of the system. The resistivity compensation algorithm also calibrates the impact of soil resistivity changes with temperature on the signal.

[0151] Used to perform mathematical operations on the collected data, such as average value calculation, maximum and minimum value detection, etc., to obtain more accurate measurement results;

[0152] Used to determine whether the cathodic protection status is normal and identify potential problems by comparing the actual voltage with the preset threshold;

[0153] When it is detected that the cathode voltage exceeds or falls below a predetermined safety range, the microprocessor unit triggers the alarm mechanism according to pre-programmed logic;

[0154] Control the alarm signal transmitter to send alarm signals and record the occurrence time and related data of the alarm event;

[0155] Receive commands from the remote monitoring center and perform corresponding operations according to the instructions, such as changing the sampling frequency and adjusting the alarm threshold.

[0156] Furthermore, the microprocessor unit receives the digital signal converted from the ADC, and uses a signal processing algorithm to identify and remove AC and DC stray current interference, and calibrates the effect of soil resistivity changes with temperature on the (current or voltage) signal through a resistivity compensation algorithm. In a cathodic protection system, the potential (voltage) of the structure relative to the reference electrode is usually measured to evaluate the effectiveness of cathodic protection, because the potential can intuitively reflect whether the metal surface is in an appropriate protection state. If a current signal is used, an additional step may be required to convert it into potential information in order to evaluate the protection status.

[0157] The specific steps involved in the signal processing algorithm to remove AC stray current interference are:

[0158] The voltage signal in the cathodic protection circuit is collected for T seconds, and the sampling frequency is f s Hz, the total number of sampling points is N;

[0159] Perform discrete Fourier transform on the collected voltage signal x[n] to obtain the frequency domain signal X[k];

[0160]

[0161] Calculate the amplitude of the spectrum |X[k]| and set a threshold to identify the frequency points whose amplitudes are significantly higher than the background noise. These frequency points are interference frequencies, and thus the interference frequencies in the voltage signal are identified.

[0162]

[0163] Where X[k] represents the kth component of the frequency domain signal, which is the spectral component of the discrete time signal x[n] at frequency k; k represents the frequency index; x[n] represents the nth sampling point of the time domain signal; n represents the time index; e -j2πkn / N represents a complex exponential function, represents a complex rotation factor at frequency k; j represents an imaginary unit, and j 2 =-1; |X[k]| represents the amplitude of the frequency domain signal X[k]; Re(X[k]) represents the real part of the frequency domain signal X[k]; Im(X[k]) represents the imaginary part of the frequency domain signal X[k];

[0164] A second-order band-stop filter is designed and applied to the original signal to remove the identified interference frequency. The transfer function of the second-order band-stop filter is:

[0165]

[0166] Where ω0 = 2πf0 represents the center angular frequency, f0 represents the center frequency; Q represents the quality factor, which determines the bandwidth and selectivity of the filter; ζ represents the damping ratio; s represents the Laplace transform variable, which is used to describe the frequency characteristics of the filter;

[0167] The transfer function of a second-order band-stop filter describes how the filter alters the input signal to produce the output signal.

[0168] Band-stop filters are mainly used to remove specific frequency components in the signal, such as the grid frequency (usually 50Hz or 60Hz) and its harmonics. In the cathodic protection system, if such AC interference exists, a second-order band-stop filter is used to help remove these unwanted frequency components, thereby improving the accuracy of data acquisition.

[0169] The signal processing algorithm converts the time domain signal into the frequency domain signal through discrete Fourier transform, which allows us to intuitively see which frequency components dominate the signal. Due to the presence of AC interference in the cathodic protection circuit, these interference components will appear as peaks in the frequency domain signal. By calculating the amplitude of the spectrum, we can identify these interference frequency components and design appropriate filters to remove them. After using a second-order band-stop filter to remove the interference frequency components, the signal purity can be significantly improved, that is, the DC signal related to cathodic protection is retained while removing the unnecessary AC interference components. This makes subsequent signal processing and data analysis more accurate.

[0170] By removing AC interference, the actual effect of cathodic protection can be more clearly observed. For example, when the cathode voltage is too low or too high, it can be more accurately identified and the cathodic protection system settings can be adjusted in time to ensure the corrosion protection effect of the pipeline.

[0171] The soil resistivity is measured using the equidistant method;

[0172] Furthermore, the resistivity compensation algorithm is used to calibrate the effect of soil resistivity changes with temperature on the current signal. The specific expression involved is:

[0173] ρ(T)=ρ0·[1+α·(T-T0)];

[0174] Where ρ(T) represents the soil resistivity at temperature T; ρ0 represents the soil resistivity at reference temperature T0; α represents the temperature coefficient of soil resistivity; T0 represents the reference temperature; T represents the currently measured soil temperature;

[0175] At the same time, considering the influence of humidity H and salinity S on soil resistivity, the calibrated soil resistivity ρ is obtained eff :

[0176] ρ eff =ρ0·[1+α·(T-T0)+β·(H-H0)+γ·(S-S0)];

[0177] Where β represents the humidity coefficient; γ represents the salinity coefficient; H0 represents the reference humidity; H represents the currently measured soil humidity; S0 represents the reference salinity; S represents the currently measured soil salinity;

[0178] And use the outlier detection method to calculate the invalid interference term Δρ eff , the final soil resistivity ρ(T, H, S) is obtained by removing the invalid interference terms:

[0179] ρ(T, H, S) = ρ eff -Δρ eff ;

[0180] ρ(T,H,S)=ρ0·[1+α·(T-T0)+β·(H-H0)+γ·(S-S0)]-Δρ eff .

[0181] Specifically, the invalid interference term Δρ eff Indicates measurement deviation due to equipment defects, measurement errors, external noise, etc.

[0182] When calibrating soil resistivity, the reason for removing invalid interference terms rather than adding them is that these represent deviations caused by factors such as equipment defects, external noise, and measurement errors. These deviations do not truly reflect the soil's inherent properties. Therefore, to obtain more accurate soil resistivity measurements, these deviations must be removed. Removing invalid interference terms can help develop more reasonable equipment maintenance plans and avoid measurement errors caused by equipment failures that affect decision-making.

[0183] Among them, get the invalid interference term Δρ eff The specific method is:

[0184] First, soil resistivity data is collected over a period of time;

[0185] Calculate the mean μ and standard deviation σ of the resistivity data during this period;

[0186] Set a threshold. Usually, data points falling outside μ±kσ are considered outliers, and k is usually 3 (i.e., the 3σ principle).

[0187] Any data point outside μ ± 3σ is considered an outlier;

[0188] The average deviation of outliers is used as the invalid interference term Δρ eff ;

[0189] The microprocessor unit reads the current temperature T, humidity H and salinity S and the measured soil resistivity ρ eff , and then use the resistivity compensation algorithm to calculate the corrected soil resistivity ρ(T, H, S). The values ​​of α, β, and γ depend on the specific composition of the soil and other environmental factors. Therefore, in practical applications, α, β, and γ all need to be determined through experimental data;

[0190] By calculating the corrected soil resistivity ρ(T, H, S), any changes or failures in the cathodic protection system, such as insufficient or excessive protection current, can be promptly detected, allowing necessary adjustments to be made. Accurate soil resistivity data helps maintain effective cathodic protection levels, avoiding corrosion caused by insufficient protection or material loss due to excessive protection, thereby extending the service life of natural gas pipelines.

[0191] The application of the resistivity compensation algorithm simplifies maintenance work. Maintenance personnel can quickly determine the system status based on the corrected data and make corresponding adjustments. There is no need for frequent on-site testing and adjustments, which reduces the difficulty of maintenance.

[0192] In this embodiment, the specific steps involved in removing DC stray current interference by using a signal processing algorithm are:

[0193] Define a fixed-size sliding window w, the window size is W, usually choose a window size large enough to contain enough data points to estimate the DC offset;

[0194] Collect a section of signal data containing DC offset, let this section of data be x 直 [n],x 直 Represents a signal containing a DC offset. n is the index of the sampling point, representing each sampling point in the time series. In the signal processing of the cathodic protection system, the DC offset in the signal needs to be removed to prevent these offsets from affecting subsequent data analysis and processing. Therefore, it is necessary to first collect a section of signal data containing a DC offset, and then process the data to remove the DC component.

[0195] And the sampling length is T 直 seconds, the sampling frequency is f s直 Hz, the total number of sampling points is N 直 ;

[0196] Calculate the average value of all sampling points as the DC component V dc :

[0197]

[0198] Where i represents the starting point of the sliding window;

[0199] Subtract the mean value V from each sample point dc , get the signal y[n] after removing the DC component;

[0200] y[n]=x 直 [n]-V i dc ;

[0201] Whenever a new data point x 直 When [n] arrives, update the position of the sliding window, that is, move forward one sampling point, and recalculate the new DC component V i+1 dc ;

[0202]

[0203] At the same time, the signal y[n] after removing the DC component is updated. When processing signals containing DC offsets, the DC component refers to the constant part of the signal, which does not change with time. In many application scenarios, this constant part is unnecessary and may even interfere with the results of subsequent processing or analysis. In cathodic protection systems, DC stray currents may interfere with the effectiveness evaluation of cathodic protection. By removing these interferences, the status of cathodic protection can be more accurately monitored and evaluated. Specifically, by subtracting the average value from each sampling point, a new signal without a DC component can be obtained. This new signal is more suitable for subsequent analysis and processing, such as evaluating the effectiveness of the cathodic protection circuit.

[0204] Repeating this process over time keeps the sliding window constantly covering the latest data points, and the DC component is updated in real time, thereby reducing cumulative errors. Removing the DC component improves signal quality and makes subsequent processing easier. For example, when performing spectrum analysis, the DC component may mask other important frequency components.

[0205] In the case of slowly changing DC offset, the removal of fixed DC components will lead to error accumulation. Therefore, the sliding window method is introduced to continuously update the DC component to reduce the accumulated error, thereby improving the accuracy of the final signal processing;

[0206] In cathodic protection systems, soil resistivity can change with temperature, humidity, and other factors, leading to DC offsets. The sliding window method can help adjust these changes in real time, ensuring measurement accuracy and reducing invalid interference caused by equipment defects, measurement errors, and other factors.

[0207] Therefore, the estimated value of the DC component V is calibrated again to take into account the change in soil resistivity. i′ dc The specific steps involved are:

[0208] Use the soil resistivity calibration formula to calculate the final soil resistivity ρ(T, H, S) and update the soil resistivity corresponding to the data in the sliding window;

[0209] The estimated value of the DC component V is recalibrated by incorporating the change in soil resistivity i′ dc ;

[0210]

[0211] The estimated value of the DC component is subtracted from the invalid interference term in proportion, so that the DC component is closer to the true value, better adapting to the change of soil resistivity during signal processing, and removing the invalid interference term, thereby improving the reliability and accuracy of the cathodic protection system.

[0212] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above in terms of preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A collector for cathodic protection of natural gas pipelines, characterized in that: The invention comprises a pile body (1), a solar panel (2) is fixedly mounted on the top of the pile body (1), an equipment cavity is opened in the pile body (1), a collector (3) is mounted in the equipment cavity, the collector (3) is electrically connected to an insulating wiring board (4), an input end of the insulating wiring board (4) is connected to a polarization probe (5) via an integrated wire group (41), and the input end of the insulating wiring board (4) is also connected to a pipeline cable, the other end of the pipeline cable is connected to a pipeline (6); The integrated wire group (41) includes a sacrificial anode wire, a long-term reference wire, an AC test wire, a polarization test wire, and a self-corrosion test wire; The collector (3) comprises: An AD data acquisition unit, the AD data acquisition unit is used to collect voltage information in the cathode protection circuit, the cathode protection circuit is composed of an AC potential test circuit, a DC potential test circuit and a relay group circuit; A wireless transmission module, which is used to transmit the collected data to a remote monitoring center wirelessly; A positioning module, which is used to determine the specific location of the monitoring point; A microprocessor unit, which is used to process information between the various unit modules and integrates a signal processing algorithm and a resistivity compensation algorithm to improve the accuracy of the collected data; The microprocessor unit receives the digital signal converted from the ADC, and uses a signal processing algorithm to identify and remove AC and DC stray current interference, and uses a resistivity compensation algorithm to calibrate the effect of soil resistivity changes with temperature on the signal; The specific steps involved in the signal processing algorithm to remove AC stray current interference are: The collection time is The voltage signal in the cathodic protection circuit is The total number of sampling points is ; The collected voltage signal Perform discrete Fourier transform to obtain the frequency domain signal ; ； Calculate the amplitude of the spectrum , to identify the interference frequency in the voltage signal; ； Where, The frequency domain signal Quantity represents the frequency index; The time domain signal sampling points; Represents a time index; represents the complex exponential function; represents the imaginary unit, and ; Represents frequency domain signal the magnitude; Represents frequency domain signal The real part of Represents frequency domain signal The imaginary part of A second-order band-stop filter is designed and applied to the original signal to remove the identified interference frequency. The transfer function of the second-order band-stop filter is: ； Where, represents the center angular frequency, is the center frequency; represents the quality factor; represents the damping ratio; represents the Laplace transform variable; The resistivity compensation algorithm is used to calibrate the effect of soil resistivity changes with temperature on the signal. The specific expression involved is: ； Where, Indicates the temperature Soil resistivity under Indicates reference temperature Soil resistivity under represents the temperature coefficient of soil resistivity; Indicates the reference temperature; Indicates the currently measured soil temperature; Also, consider humidity and salinity Impact on soil resistivity, get calibrated soil resistivity : ； Where, represents the humidity coefficient; represents the salinity coefficient; Indicates reference humidity; Indicates the currently measured soil moisture; represents the reference salinity; Indicates the currently measured soil salinity; And use the outlier detection method to calculate the invalid interference items The invalid interference term represents the deviation caused by equipment defects, external noise, and measurement error factors. The final soil resistivity is obtained by removing the invalid interference term. : ； 。 2. The collector for cathodic protection of natural gas pipelines according to claim 1, characterized in that: The AD data acquisition unit includes: A collection unit, wherein the collection unit is electrically connected to the gas pipeline via a cathodic protection cable; A voltage sensor receives the cathode voltage of the analog signal from the acquisition unit at a certain sampling time interval, converts the cathode voltage of the analog signal into a digital signal through the ADC, and sends the digital signal to the first input terminal of the comparator; a voltage module, the voltage module being configured to send the received reference voltage to the second input terminal of the comparator; A comparator, the comparator being configured to compare a cathode voltage received at a first input terminal with a reference voltage received at a second input terminal, and to issue an alarm signal through an output terminal if the cathode voltage is higher than the reference voltage, and to loop and wait for the next acquisition and comparison if the cathode voltage is equal to or lower than the reference voltage; An alarm signal transmitter is used to send an alarm signal wirelessly.

3. The collector for cathodic protection of natural gas pipelines according to claim 1, characterized in that: In the cathodic protection circuit: The AC potential test circuit is used to measure the AC interference voltage in the soil around the pipeline; The DC potential test circuit is used to measure the DC potential difference between the pipeline and the reference electrode; The relay group circuit is used to control and switch different test modes.

4. The collector for cathodic protection of natural gas pipelines according to claim 3, characterized in that: The AC potential test circuit includes an operational amplifier U64, wherein an input terminal VIN of the operational amplifier U64 is connected to a capacitor C234, a capacitor C235, and a resistor R328, wherein one end of the capacitor C234 is connected to the cathode of the diode D3, and the anode of the diode D3 is connected to the -5V input voltage, one end of the capacitor C235 is connected to the anode of the diode D4, and the cathode of the diode D4 is connected to the +5V input voltage, and a common node of the capacitors C234 and C235 serves as an input terminal for receiving a current test signal, and the other end of the capacitor C234 shares a node with C235 and is connected to the input terminal VIN of the operational amplifier; The OUTPUT terminal of the operational amplifier U64 is connected to a resistor R329 and a capacitor C238, the other end of the capacitor C238 is grounded, and a common node of the resistor R329 and the capacitor C238 is used as an AC potential output; The -VS terminal of the operational amplifier U64 is connected to a capacitor C239, the other end of which is grounded, and a capacitor C241 is connected to a common node between the capacitor C239 and the -VS terminal, the other end of which is connected to the CAV terminal of the operational amplifier U64, and the negative electrode of the capacitor C241 is connected to a -5V input voltage; The +VS terminal of the operational amplifier U64 is connected to a capacitor C236, the other end of the capacitor C236 is connected to the COM terminal of the operational amplifier U64, and the common node of the COM terminal and the capacitor C236 is grounded, and the common node of the capacitor C236 and the +VS terminal is connected to a +5V input voltage; The Cc terminal of the operational amplifier U64 is connected to a capacitor C242 , and the other end of the capacitor C242 is grounded.

5. The collector for cathodic protection of natural gas pipelines according to claim 3, characterized in that: The DC potential test circuit includes a dual operational amplifier LM324, wherein the -IN terminal of the dual operational amplifier LM324 is connected to a pipe, and the +IN terminal of the dual operational amplifier LM324 is connected to a current test signal; The OUT terminal of the dual operational amplifier LM324 is connected to a resistor R327, and the other end of the resistor R327 serves as an output terminal of the current-to-potential signal; The VS terminal of the dual operational amplifier LM324 is connected to a capacitor C231, one end of the capacitor C231 and a common node of the VS terminal are connected to a capacitor C233, and a +5V input voltage is connected to the common node of the capacitor C231 and the VS terminal, and the other end of the capacitor C231 and the other end of the capacitor C233 are commonly grounded; The OFFSET terminal of the dual operational amplifier LM324 is connected to a resistor R301, the other end of which is connected to a +5V input voltage. A resistor R331 is connected to a common node between the OFFSET terminal and the resistor R301, and a capacitor C243 is connected to a common node between the resistor R331 and the resistor R301. The other end of the capacitor C243 is connected to a common ground with the resistor R331. The GND terminal, A1 terminal and A2 terminal of the dual operational amplifier LM324 are grounded in common.

6. The collector for cathodic protection of natural gas pipelines according to claim 3, characterized in that: The relay group circuit includes a current test signal output circuit and a potential test signal output circuit; Wherein, the current test signal output circuit includes relay K1, relay K1 and relay K3; The contact 3 of the relay K1 is connected to the resistor R1, the other end of the resistor R1 is connected to the resistor R2, the other end of the resistor R2 is connected to the contact 5 of the relay K1, and the common node of the resistor R1 and the resistor R2 is connected to the pipeline; The contact 4 of the relay K1 is connected to the contact 4 of the relay K3, and the contact 5 of the relay K3 is connected to the sacrificial anode, and the contact 3 of the relay K3 is connected to the contact 4 of the relay K2; The contact 5 of the relay K2 is connected to the polarization test piece, and the contact 3 of the relay K2 is connected to the AC test piece.

7. The collector for cathodic protection of natural gas pipelines according to claim 6, characterized in that: The potential test signal output circuit includes relay K4, relay K5, relay K6, relay K7, relay K8 and relay K9; Among them, the contact 4 of the relay K4 is connected to the pipeline, the contact 4 of the relay K5 is connected to the polarized test piece, the contact 4 of the relay K6 is connected to the sacrificial anode, and the contact 4 of the relay K7 is connected to the natural test piece. The contacts 3 of the relay K4, relay K5 and relay K6 are connected in parallel; The contacts 5 of the relays K4, K5, K6 and K7 are connected in parallel, and the parallel common node of the contacts 5 is connected to the contact 5 of the relay K8, and the contact 3 of the relay K8 serves as the output end of the current-to-potential signal; The contact 4 of the relay K8 is connected to a resistor R3, the other end of the resistor R3 is connected to the contact 4 of the relay K9, the common node of the resistor R3 and the contact 4 of the relay K8 is connected to the contact 3 of the relay K9, and the contact 4 of the relay K9 serves as the output end of the potential test signal; A common node between the resistor R3 and the contact 4 of the relay K9 is connected to a resistor R4 , and the other end of the resistor R4 is grounded.

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