An intelligent monitoring system for reverse state and grounding fault of submersible electric pump

Abstract

The application discloses an intelligent monitoring system for reverse state and grounding fault of an electric submersible pump, and relates to the technical field of operation state monitoring and electrical protection of the electric submersible pump, which comprises the following steps: in a grounding fault effective data window, a single-phase-to-ground offset judgment is performed, and a starting locking signal and a grounding fault locking signal are generated according to a distinguishing result; and through a sampling chain credibility checking mechanism, the system has real-time self-awareness ability for the health of a detection link, can confirm the credibility of sampling data in advance before diagnosis, and therefore, a diagnosis conclusion is no longer a blind output of only judgment without responsibility, but a reliable decision with credibility guarantee.

Description

Technical Field

[0001] This invention relates to the field of submersible electric pump operation status monitoring and electrical protection technology, and in particular to an intelligent monitoring system for submersible electric pump reverse state and grounding fault. Background Technology

[0002] Submersible electric pumps (SAPs) are key equipment in oil and gas well lifting systems. Their supporting electrical control technology has gradually evolved from early start-stop control and conventional protection to comprehensive monitoring and protection technology that integrates voltage monitoring, anomaly identification, and interlocking control. In existing technologies, the three-phase voltage on the high-pressure side of the SSP, the residual voltage after shutdown, and the protection output are usually collected and processed to improve the operational safety and control reliability under high-pressure conditions at the well site.

[0003] However, existing technologies generally assume that the voltage transient process after the submersible electric pump stops is noise that is difficult to identify. Therefore, protection strategies are stuck at the level of delay waiting + steady-state judgment. This strategy implies an unnoticed defect: it sacrifices the ability to analyze the internal information of the transient process. When multiple physical effects such as cable energy storage, driver residue, and motor reverse induction are superimposed over time, existing technologies can only wait for them to decay on their own, and cannot decouple and deal with them separately during the transient process. This blind spot in understanding leads to the fundamental contradiction of protection vacuum and false lockout. Summary of the Invention

[0004] In a first aspect, the present invention provides an intelligent monitoring system for the reverse state and grounding fault of a submersible electric pump, comprising: a high-voltage divider unit, an isolated voltage conversion unit, an isolated reverse voltage detection unit, a control chip unit, an output indicator unit, and a control power supply unit;

[0005] The high-voltage terminal of the aforementioned high-voltage divider unit is used to connect to the three-phase power supply line of the submersible electric pump, and its low-voltage tap terminal is simultaneously connected to the three-phase input terminals of the isolated voltage conversion unit and the isolated back pressure detection unit.

[0006] The aforementioned control chip unit is configured as follows:

[0007] The three-phase ground sampling voltage is obtained from the isolated voltage conversion unit through the analog-to-digital sampling port, and the reverse voltage zero-crossing pulse is obtained from the isolated reverse voltage detection unit through the pulse capture port.

[0008] The sampling time base of the analog-to-digital sampling port and the aforementioned pulse capture port is consistent.

[0009] After receiving the shutdown signal of the submersible electric pump, a shutdown event recording area is established. Based on the envelope change characteristics of the three-phase ground sampling voltage and the phase sequence characteristics of the reverse voltage zero-crossing pulse, under a unified sampling time base, the sampling points corresponding to cable energy storage release, drive-side residual or motor reverse induction after shutdown are marked and excluded to form an effective ground fault data window for ground fault judgment.

[0010] Within the valid data window for ground faults, a single-phase ground offset judgment is performed, and based on the distinction result, a start-up blocking signal and a ground fault lockout signal are generated.

[0011] As a preferred embodiment of the intelligent monitoring system for the reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit sets status markers for the sampling points, including cable energy storage release markers, drive-side residual markers, motor reverse induction markers, and grounding effective markers.

[0012] Sampling points with cable energy storage release markers, drive-side residual markers, and motor reverse induction markers are not included in the single-phase ground offset judgment.

[0013] As a preferred embodiment of the intelligent monitoring system for the reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit marks sampling points that meet the following conditions as cable energy storage release:

[0014] The amplitude envelope of the three-phase ground sampling voltage decreases synchronously after shutdown;

[0015] The rate of decline in the voltage change characteristic decreases with time, and within the corresponding time period, the pulse capture port does not capture continuous reverse voltage zero-crossing pulses with reverse phase sequence.

[0016] As a preferred embodiment of the intelligent monitoring system for the reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit, after excluding sampling points with cable energy storage release markers, marks sampling points that meet one of the following conditions as drive-side residuals:

[0017] When powered by the frequency converter driver, the AC component of the three-phase ground sampling voltage has a short-term holding characteristic that matches the frequency converter driver output frequency recorded before shutdown, and no reverse phase sequence pulse is formed;

[0018] The three-phase ground sampling voltage showed a discontinuous decrease, and the reverse voltage zero-crossing pulse did not form a reverse phase sequence;

[0019] Discontinuous descent refers to the decrease in amplitude envelope between adjacent sampling windows exceeding a preset amplitude threshold, or the occurrence of a transient plateau before resuming descent during the amplitude envelope descent process.

[0020] The interval between adjacent zero-crossing pulses of the reverse voltage did not increase continuously.

[0021] As a preferred embodiment of the intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump described in this invention, the control chip unit marks sampling points that simultaneously meet the following conditions as motor reverse induction and generates a start-lock signal:

[0022] The phase sequence direction of the reverse voltage zero-crossing pulse is opposite to the pre-stored normal operation phase sequence direction;

[0023] The interval between adjacent zero-crossing pulses of the reverse voltage increases over K consecutive zero-crossing cycles;

[0024] The voltage amplitude envelope decreases as the interval between adjacent zero crossings increases.

[0025] As a preferred embodiment of the intelligent monitoring system for reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit forms an equivalent value of reverse induction energy based on sampling points marked with motor reverse induction.

[0026] The equivalent value of the reverse induction energy is given by the following formula:

[0027] ;

[0028] in, This is the equivalent value of the reverse induction energy. The number of sampling windows with motor reverse induction markers. The duration of a single sampling window, For the first The interval between adjacent zero crossings of each sampling window, This refers to the zero-crossing interval at the normal operating frequency of the submersible electric pump. For the first Within a sampling window, the voltages of phase A, phase B, and phase C to ground are sampled, and the positive sequence voltage amplitude is obtained by calculating using the symmetrical component method.

[0029] When the equivalent value of the reverse induced energy is higher than the safety threshold, the output branch of the first relay is controlled by the start-lock signal, so that the start-permission circuit of the submersible pump remains open.

[0030] As a preferred embodiment of the intelligent monitoring system for the reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit is further configured to perform sampling chain reliability verification.

[0031] Under the same sampling time base, compare the zero-crossing time of the three-phase ground sampling voltage of the same electrical phase with the zero-crossing pulse edge time of the reverse voltage. If the time deviation exceeds the limit within N consecutive sampling periods, the sampling chain is marked as unreliable.

[0032] As a preferred embodiment of the intelligent monitoring system for reverse state and grounding fault of the submersible electric pump described in this invention, the control chip unit marks sampling points that do not have cable energy release markers, drive-side residual markers, motor reverse induction markers, and unreliable sampling chain markers as grounding effective markers.

[0033] The continuously distributed effective ground fault sampling points constitute the effective ground fault data window.

[0034] As a preferred embodiment of the intelligent monitoring system for the reverse state and ground fault of the submersible electric pump described in this invention, in the effective data window of the ground fault, for any phase, the offset of its amplitude envelope relative to the average amplitude envelope of the other two phases is calculated. When the offset exceeds the preset offset threshold for a preset confirmation time, the single-phase ground offset judgment is established, and a ground fault locking signal is generated.

[0035] As a preferred embodiment of the intelligent monitoring system for the reverse state and grounding fault of the submersible electric pump described in this invention, the output indication unit includes a first relay output branch and a second relay output branch, and their contacts are all connected in series to the submersible electric pump start-up permission circuit.

[0036] The aforementioned first relay output branch closes after the start-up interlocking condition is released;

[0037] The output branch of the second relay mentioned above remains disconnected after receiving a ground fault lockout signal.

[0038] The beneficial effects of this invention are as follows: By unifying the three-phase ground sampling voltage and the reverse voltage zero-crossing pulse under the same sampling time base, this invention enables different physical excitation sources such as cable distributed capacitance energy storage release, frequency converter residual output, and liquid column reflux driving motor reversal to be distinguished and identified based on their respective envelope changes, phase sequence changes, and frequency change characteristics.

[0039] Based on this, the present invention achieves decoupling of the hybrid transient process after shutdown:

[0040] On the one hand, the accuracy of ground fault diagnosis no longer depends on the empirical assumption of waiting for a sufficient amount of time. Instead, it performs judgment within the effective data window of ground fault formed after eliminating various non-fault interference sources. This eliminates the contamination of single-phase ground fault criteria by cable residual voltage and motor reverse induction voltage, and makes the identification of ground faults based on clean data that has eliminated non-fault factors.

[0041] On the other hand, through the sampling chain credibility verification mechanism, the system has the ability to self-awareness of the health of the detection chain itself in real time. It can confirm the credibility of the sampling data before diagnosis. Therefore, the diagnostic conclusion is no longer a blind output that only gives judgment without taking responsibility, but a reliable decision with credibility guarantee.

[0042] In summary, this invention effectively solves the long-standing problem of misjudgment in medium-voltage, ungrounded long-cable submersible pump systems during shutdown. While improving the accuracy of protection and control, it reduces unnecessary shutdowns and maintenance caused by misjudgments, thus ensuring the continuity of oil and gas well production. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the intelligent monitoring system for the reverse rotation state and grounding fault of the submersible electric pump in Example 1.

[0045] Figure 2 This is a flowchart of grounding judgment and interlocking output in Example 1.

[0046] Figure 3 This is a schematic diagram of the intelligent monitoring system for the reverse rotation state and grounding fault of the submersible electric pump in Example 4.

[0047] Figure 4 This is a circuit diagram of the high-voltage divider unit in Example 4.

[0048] Figure 5 This is a circuit diagram of the isolated voltage conversion unit in Example 4.

[0049] Figure 6 This is a circuit diagram of the isolated high-sensitivity reverse voltage detection unit in Example 4.

[0050] Figure 7 This is a circuit diagram of the control chip unit and wiring terminals in Example 4.

[0051] Figure 8 This is a circuit diagram of the output indicator unit in Example 4.

[0052] Figure 9 This is a circuit diagram of the control power supply unit in Example 4. Detailed Implementation

[0053] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0054] Example 1, referring to Figure 1 and Figure 2This is the first embodiment of the present invention. This embodiment provides an intelligent monitoring system for the reverse state and grounding fault of a submersible electric pump, including: a high-voltage divider unit, an isolated voltage conversion unit, an isolated reverse voltage detection unit, a control chip unit, an output indicator unit, and a control power supply unit.

[0055] The high-voltage terminal of the aforementioned high-voltage divider unit is used to connect to the three-phase power supply line of the submersible electric pump, and its low-voltage tap terminal is simultaneously connected to the three-phase input terminals of the isolated voltage conversion unit and the isolated back pressure detection unit.

[0056] The aforementioned control chip unit is configured as follows:

[0057] The three-phase ground sampling voltage is obtained from the isolated voltage conversion unit through the analog-to-digital sampling port, and the reverse voltage zero-crossing pulse is obtained from the isolated reverse voltage detection unit through the pulse capture port.

[0058] The sampling time base of the analog-to-digital sampling port and the aforementioned pulse capture port is consistent.

[0059] After receiving the shutdown signal of the submersible electric pump, a shutdown event recording area is established. Based on the envelope change characteristics of the three-phase ground sampling voltage and the phase sequence characteristics of the reverse voltage zero-crossing pulse, under a unified sampling time base, the sampling points corresponding to cable energy storage release, drive-side residual or motor reverse induction after shutdown are marked and excluded. The time window consisting of the remaining continuous sampling points after exclusion is used to form an effective ground fault data window for ground fault judgment.

[0060] Within the valid data window of the ground fault, perform single-phase ground offset judgment, and generate start-up blocking signal and ground fault lockout signal based on the discrimination result;

[0061] In this embodiment, an intelligent monitoring system for the reverse state and grounding fault of a submersible electric pump is provided, which is applied to the ground control cabinet of a long cable submersible electric pump that uses a neutral point ungrounded power supply method.

[0062] The aforementioned long-cable submersible pump refers to a submersible pump system in which the surface control cabinet and the downhole submersible pump motor are connected by a three-core high-voltage cable.

[0063] After such systems are shut down, residual voltage in the cables, reverse induced voltage in the motor, and single-phase voltage deviation to ground are likely to occur simultaneously.

[0064] The aforementioned residual voltage in the cable refers to the short-time voltage formed in a three-core high-voltage cable after power outage due to the release of distributed capacitance.

[0065] The aforementioned reverse induced voltage of the motor refers to the induced voltage generated by the motor windings and fed back to the ground detection end when the well fluid column flows back and drives the motor to rotate in the reverse direction after the submersible pump stops.

[0066] The aforementioned single-phase-to-ground voltage deviation refers to the state in which the voltage of a certain phase to ground deviates continuously from the voltages of the other two phases to ground in a neutral-point ungrounded power supply system. It is used to indicate the risk of single-phase insulation degradation or single-phase grounding.

[0067] This system includes a high-voltage divider unit, an isolated voltage conversion unit, an isolated reverse voltage detection unit, a control chip unit, an output indicator unit, and a control power supply unit.

[0068] The three-phase input terminals of the high-voltage divider unit are respectively connected to the A-phase, B-phase, and C-phase high-voltage power supply lines of the submersible electric pump;

[0069] The high voltage divider unit is equipped with an A-phase voltage divider resistor chain, a B-phase voltage divider resistor chain, and a C-phase voltage divider resistor chain. The voltage division ratio of the three voltage divider resistor chains is the same.

[0070] Each voltage-resistance chain consists of several high-voltage resistors connected in series. The number of series stages of the high-voltage resistors is determined based on the rated line voltage of the submersible electric pump and the allowable operating voltage of a single high-voltage resistor.

[0071] This ensures that the voltage across a single high-voltage resistor does not exceed its allowable operating voltage, and that the low-voltage terminal voltage after voltage division falls within the input range of the subsequent isolation detection circuit.

[0072] Among them, the voltage divider resistor chain of phase A leads to the low voltage terminal of phase A, the voltage divider resistor chain of phase B leads to the low voltage terminal of phase B, and the voltage divider resistor chain of phase C leads to the low voltage terminal of phase C.

[0073] The low-voltage terminals of phase A, phase B, and phase C are respectively connected to the three-phase input terminals of the isolated voltage conversion unit, and also to the three-phase input terminals of the isolated reverse voltage detection unit.

[0074] The isolated voltage conversion unit and the isolated reverse voltage detection unit share the same set of three-phase low-voltage terminals output by the high-voltage divider unit, so that the three-phase ground sampling voltage and the reverse voltage zero-crossing pulse have the same voltage source. This provides a physical basis for distinguishing cable residual voltage, motor reverse induced voltage and single-phase ground voltage deviation on the same shutdown time line.

[0075] An isolated voltage conversion unit includes three isolated conversion channels with the same structure.

[0076] The three isolation conversion channels correspond to the low-voltage terminals of phase A, phase B, and phase C, respectively.

[0077] Each isolation conversion channel includes an input current limiting resistor, an isolation transformer, a DC bias circuit, a low-pass filter circuit, and a limiting protection circuit;

[0078] The input current-limiting resistor is used to limit the current entering the primary side of the isolation transformer from the low-voltage side;

[0079] Isolation transformers are used to achieve electrical isolation between the high-voltage divider side and the control chip unit;

[0080] The DC bias circuit boosts the AC signal output from the secondary side of the isolation transformer to the input range allowed by the analog-to-digital sampling port of the control chip unit;

[0081] Low-pass filter circuits are used to filter out high-frequency spikes and switching noise;

[0082] The limiting protection circuit is used to prevent abnormal voltage from impacting the analog-to-digital sampling port;

[0083] After processing by the isolated voltage conversion unit, the control chip unit obtains the A-to-ground sampled voltage, the B-to-ground sampled voltage, and the C-to-ground sampled voltage through the analog-to-digital sampling port.

[0084] An isolated back pressure detection unit is used to acquire the back pressure zero-crossing pulse after the submersible electric pump stops.

[0085] The isolated back pressure detection unit includes two isolated back pressure detection units for phase A and phase B, or three isolated back pressure detection units for phase A, phase B and phase C;

[0086] When using a dual-channel isolated back-voltage detection unit, the control chip unit determines whether there is a reverse phase sequence based on the order of the two back-voltage zero-crossing pulses.

[0087] When using a three-way isolated back pressure detection unit, the control chip unit confirms the phase sequence direction based on the cyclic sequence of the three back pressure zero-crossing pulses;

[0088] Each isolated reverse voltage detection unit includes a current-limiting resistor, an RC low-pass filter circuit, an operational amplifier circuit, a hysteresis comparator circuit, and an opto-isolation circuit.

[0089] The current-limiting resistor and RC low-pass filter circuit are used to suppress the spike interference generated during shutdown.

[0090] Operational amplifier circuits are used to amplify the low amplitude induced voltage after shutdown;

[0091] The hysteresis comparator circuit uses a DC bias reference as a comparison reference to convert the AC change of the induced voltage into a square wave signal.

[0092] The aforementioned DC bias circuit is used to boost the AC signal output from the secondary side of the isolation transformer to a preset DC bias reference voltage Vref. This reference voltage Vref is provided to the hysteresis comparison circuit in the isolated reverse voltage detection unit as a comparison reference to ensure that the two detection channels have the same zero potential reference.

[0093] After isolating the square wave signal, the opto-isolation circuit sends it to the pulse capture port of the control chip unit;

[0094] The aforementioned reverse voltage zero-crossing pulse refers to the digital pulse generated when the reverse voltage signal crosses the comparison reference set by the hysteresis comparator circuit;

[0095] The control chip unit obtains the three-phase ground sampling voltage through the analog-to-digital sampling port and obtains the reverse voltage zero-crossing pulse through the pulse capture port;

[0096] The analog-to-digital sampling port and the pulse capture port use the same internal timer as the sampling time base;

[0097] Among them, consistent sampling time base means that the sampling time of the three-phase ground sampling voltage and the edge recording time of the reverse voltage zero-crossing pulse are both calibrated by the same timer;

[0098] Therefore, the control chip unit can correlate the three-phase ground sampling voltage change at a certain moment with the reverse voltage zero-crossing pulse edge near the same moment, avoiding the misinterpretation of cable residual voltage or motor reverse induced voltage as a ground fault due to the inconsistency of the time bases of the two types of signals.

[0099] After the submersible electric pump stops, the control chip unit first reads the three-phase ground sampling voltage;

[0100] If the amplitude envelopes of the sampling voltages of phases A, B, and C to ground decrease synchronously in the initial stage of shutdown, and the pulse capture port does not record three consecutive reverse voltage zero-crossing pulses with reverse phase sequence, then this voltage segment is treated as cable residual voltage and is not used to generate a ground fault lockout signal.

[0101] The above amplitude envelope refers to the maximum absolute offset of the A-to-ground sampled voltage, B-to-ground sampled voltage, and C-to-ground sampled voltage relative to the DC bias reference within a sampling window.

[0102] When it is necessary to obtain the overall three-phase amplitude, the average value of the maximum absolute offset of the three phases is used as the average amplitude envelope of the sampling window;

[0103] After the residual voltage of the cable decays, if the phase sequence direction of the reverse voltage zero-crossing pulse is opposite to the phase sequence direction of the normal operation of the submersible pump, and the edge times of four consecutive reverse voltage zero-crossing pulses are t1, t2, t3 and t4 respectively, and satisfy t3-t2>t2-t1 and t4-t3>t3-t2, then it is determined that the adjacent zero-crossing interval increases continuously.

[0104] After the submersible electric pump is powered on and running normally, the control chip unit first obtains the reverse voltage zero-crossing pulses of phase A and phase B, or phases A, B, and C, through the pulse capture port. When it is determined that the motor is in normal electric operation, the chip records the order in which the pulses appear. For example, if the phase A pulse leads the phase B pulse, this order is defined as the normal phase sequence direction and stored.

[0105] If the pulse sequence detected after shutdown is reversed, for example, the B phase pulse leads the A phase pulse, it is considered to be a reverse phase sequence.

[0106] At this time, if the amplitude envelope of the three-phase ground sampling voltage decreases as the adjacent zero-crossing interval increases, then this voltage segment is treated as the reverse induced voltage of the motor.

[0107] The control chip unit generates a start-lock signal in this state;

[0108] The first relay output branch is controlled by the start-lock signal, and the normally closed contact of the first relay output branch is connected in series in the submersible electric pump start-permit circuit.

[0109] When the start-lock signal is valid, the output branch of the first relay disconnects the start-permission circuit for the submersible electric pump.

[0110] When the reverse voltage zero-crossing pulse disappears, or the electrical frequency corresponding to the reverse voltage zero-crossing pulse is lower than the safe reversal electrical frequency, the control chip unit enters the grounding confirmation.

[0111] The safe reversal frequency is determined based on the rated speed of the submersible pump and the number of pole pairs of the motor: Assuming the rated speed of the submersible pump is nr and the number of pole pairs of the motor is p, and the safe reversal speed is taken as 5% to 10% of the rated speed, then the safe reversal frequency fs = p × nr × η / 60, where η is taken as 0.05 to 0.10, to avoid judging whether the reversal has disappeared based solely on a fixed waiting time;

[0112] During the grounding confirmation process, the control chip unit performs single-phase ground offset judgment on the three-phase ground sampling voltage after eliminating cable residual voltage and motor reverse induced voltage.

[0113] Specifically, under rated operating conditions, the average amplitude of the three-phase-to-ground sampling voltage is set to Ue, and the offset threshold is set to 0.20Ue to 0.35Ue, preferably 0.25Ue;

[0114] The setting of this offset threshold needs to take into account both the detection sensitivity to single-phase insulation degradation and the tolerance to normal three-phase imbalance of the system.

[0115] In a neutral-point ungrounded system, the three-phase voltage imbalance during normal operation is typically much less than 20%. Therefore, a lower threshold of 0.20Ue is sufficient to avoid the inherent offset under most normal operating conditions, while the preferred value of 0.25Ue provides a balanced choice between sensitivity and disturbance rejection.

[0116] When the offset of any relative ground sampling voltage to the average of the other two relative ground sampling voltages is greater than the offset threshold for more than 2 consecutive seconds, the control chip unit generates a ground fault lockout signal.

[0117] This judgment method ensures that grounding judgment is performed only during the sampling phase, which is not dominated by cable residual voltage and motor reverse induced voltage, thus reducing false locking caused by shutdown transient voltage.

[0118] The output indication unit includes a first relay output branch and a second relay output branch;

[0119] The first relay output branch is controlled by the start-lock signal and connected in series with the submersible pump start-permit circuit;

[0120] The second relay output branch is controlled by the ground fault lockout signal and is connected in series in the ground fault lockout circuit;

[0121] The ground fault locking circuit and the submersible electric pump start-up permission circuit are interlocked by hardware, specifically as follows:

[0122] The normally closed contact of the second relay output branch is connected in series with a ground fault locking circuit, which is then connected in series with the submersible pump start permission circuit.

[0123] When the ground fault lockout signal is valid, the output branch of the second relay is disconnected, thus disconnecting the ground fault lockout circuit. This, through hardware interlocking, prevents the submersible pump start permission circuit from closing.

[0124] Therefore, once the reverse induced voltage of the motor disappears, the first relay output branch can release the start lockout.

[0125] However, the second relay output branch remains open until the ground fault lockout signal is released;

[0126] The control power supply unit provides low-voltage DC power to the isolated voltage conversion unit, the isolated reverse voltage detection unit, the control chip unit, and the output indication unit;

[0127] The control power supply unit and the high-voltage power supply line of the submersible pump are electrically isolated to ensure that the low-voltage control circuit operates stably in a high-voltage environment.

[0128] This system focuses on the unique electrical processes after a long-cable submersible electric pump stops, and separately handles the residual voltage of the cable formed by the release of the cable's distributed capacitance, the reverse induced voltage of the motor formed by the motor's reversal, and the single-phase-to-ground voltage offset under a neutral-point ungrounded system.

[0129] The three-phase ground sampling voltage and the reverse voltage zero-crossing pulse come from the same set of three-phase low-voltage terminals, reducing the phase difference and amplitude difference caused by different sampling points;

[0130] The analog-to-digital sampling port and the pulse capture port use the same time base, enabling the control chip unit to determine the relationship between voltage attenuation, phase sequence reversal, and single-phase offset based on the same time base.

[0131] The first relay output branch and the second relay output branch correspond to reverse start lockout and ground fault lockout, respectively, to avoid confusing the reverse risk that can be automatically released with the ground risk that requires maintenance confirmation.

[0132] Example 2, a second embodiment of the present invention, provides an intelligent monitoring system for the reverse rotation state and grounding fault of a submersible electric pump, comprising:

[0133] The control chip unit sets status markers for the sampling points, including cable energy storage release marker, drive-side residual marker, motor reverse induction marker, and grounding effective marker;

[0134] Sampling points with cable energy storage release markers, drive-side residual markers, and motor reverse induction markers are not included in the single-phase ground offset judgment;

[0135] The control chip unit will mark sampling points that meet the following conditions as cable energy storage release:

[0136] The amplitude envelope of the three-phase ground sampling voltage decreases synchronously after shutdown;

[0137] The rate of decline in the voltage change characteristic quantity decreases with time, and within the corresponding time period, the pulse capture port does not capture continuous reverse voltage zero-crossing pulses with reverse phase sequence;

[0138] After excluding sampling points with cable energy storage release markers, the control chip unit marks sampling points that meet one of the following conditions as drive-side remnants:

[0139] When the submersible electric pump is powered by a variable frequency drive, the AC component of the three-phase ground sampling voltage has a short-term holding characteristic that matches the output frequency of the variable frequency drive recorded before shutdown, and no reverse phase sequence pulse is formed.

[0140] The three-phase ground sampling voltage showed a discontinuous decrease, and the reverse voltage zero-crossing pulse did not form a reverse phase sequence;

[0141] Discontinuous descent refers to the decrease in amplitude envelope between adjacent sampling windows exceeding a preset amplitude threshold, or the occurrence of a transient plateau before resuming descent during the amplitude envelope descent process.

[0142] The interval between adjacent zero-crossing pulses of the reverse voltage does not increase continuously;

[0143] The control chip unit marks sampling points that simultaneously meet the following conditions as motor reverse induction and generates a start-lock signal:

[0144] The phase sequence direction of the reverse voltage zero-crossing pulse is opposite to the pre-stored normal operation phase sequence direction;

[0145] The interval between adjacent zero-crossing pulses of the reverse voltage increases over K consecutive zero-crossing cycles;

[0146] The voltage amplitude envelope decreases as the interval between adjacent zero crossings increases.

[0147] The control chip unit forms an equivalent value of reverse induction energy based on sampling points marked with motor reverse induction.

[0148] The equivalent value of the reverse induction energy is given by the following formula:

[0149] ;

[0150] in, This is the equivalent value of the reverse induction energy. The number of sampling windows with motor reverse induction markers. The duration of a single sampling window, For the first The interval between adjacent zero crossings of each sampling window, This refers to the zero-crossing interval at the normal operating frequency of the submersible electric pump. For the first Within a sampling window, the voltages of phase A, phase B, and phase C to ground are sampled, and the positive sequence voltage amplitude is obtained by calculating using the symmetrical component method.

[0151] It should be noted that for any sampling window with a motor reverse induction mark, the control chip unit first acquires the waveform data of the A-phase, B-phase and C-phase ground sampling voltages within the window, and extracts the fundamental frequency component corresponding to the adjacent zero-crossing interval of the reverse voltage zero-crossing pulse by performing Fourier transform or bandpass filtering on the waveform data.

[0152] Based on the amplitude and phase of the extracted fundamental voltage components of phases A, B, and C, three-phase voltage phasors are constructed, and the positive sequence voltage amplitude is then calculated using the symmetrical component method.

[0153] The equivalent value of reverse induced energy is an empirical indicator used to quantify the potential impact risk generated by the reverse induction of the motor after shutdown. The formula uses the voltage square term, which is based on the basic electrical relationship that energy is proportional to the square of voltage. The frequency attenuation coefficient is introduced because when the frequency of the induced voltage decreases, that is, increases, the same amplitude voltage applies a unidirectional torque to the system for a longer time within half a cycle, resulting in a greater potential impact and shaft damage risk. Therefore, this coefficient is used to weight the risk.

[0154] By summing the contributions of each sampling window, an equivalent value representing the total risk level of the reversal shock is obtained;

[0155] When the equivalent value of the reverse induced energy is higher than the safety threshold, the output branch of the first relay is controlled by the start-lock signal, so that the start-permission circuit of the submersible electric pump remains open.

[0156] In this embodiment, based on Embodiment 1, the formation method of the shutdown event recording area, status marker, residual voltage recording, motor reverse induced voltage recording, and the equivalent value of reverse induced energy is further explained;

[0157] This embodiment still takes the ground control cabinet of a long cable submersible oil pump with a neutral point ungrounded power supply as the object, and addresses the problem of the cable energy release, the residual output of the frequency converter driver and the reverse induced voltage of the motor being mixed at the same sampling end after the submersible oil pump stops;

[0158] The sampling points in this embodiment use the same sampling time base as in Embodiment 1;

[0159] Each sampling point corresponds to a set of data formed by the control chip unit within a sampling window;

[0160] A sampling window is a basic analysis time unit with a preset fixed duration, which is divided based on the sampling time base.

[0161] Among them, the sampling of the three-phase ground sampling voltage and the calculation of the amplitude envelope, as well as the attribution of the reverse voltage zero-crossing pulse edge, are all based on this sampling window as the basic unit.

[0162] This set of data includes the A-to-ground sampled voltage, the B-to-ground sampled voltage, the C-to-ground sampled voltage, and the timing of the reverse voltage zero-crossing pulse edge falling within the sampling window;

[0163] If no back-voltage zero-crossing pulse appears within a sampling window, the back-voltage zero-crossing pulse information at that sampling point is recorded as a null value.

[0164] After receiving the shutdown signal from the submersible electric pump, the control chip unit establishes a shutdown event recording area;

[0165] The aforementioned shutdown event recording area refers to the area that records the above data in chronological order of the sampling points, and records the adjacent zero-crossing interval calculated from the timing of the adjacent reverse voltage zero-crossing pulse edges.

[0166] The control chip unit generates voltage change characteristic quantities, including the falling slope and amplitude envelope, based on the A-relative-to-ground sampled voltage, the B-relative-to-ground sampled voltage, and the C-relative-to-ground sampled voltage.

[0167] The amplitude envelope refers to the maximum absolute offset of the three-phase ground sampling voltage relative to the DC bias reference within a sampling window.

[0168] The descent slope is the ratio of the change in amplitude envelope between adjacent sampling windows to the time interval.

[0169] To reduce the impact of a single spike on the judgment result, the amplitude envelope can be first processed by median within three adjacent sampling windows, and then used for the calculation of the descent slope;

[0170] In the initial stage of shutdown, if the amplitude envelopes of the sampling voltages of phases A, B, and C to ground are all lower than the amplitude envelopes of their respective previous sampling windows, and the change direction of the three phase amplitude envelopes is consistent, and at the same time, the pulse capture port does not record three consecutive reverse voltage zero-crossing pulses with reverse phase sequence, then the control chip unit will assign the corresponding sampling point to the cable energy storage release mark.

[0171] Among them, the cable energy storage release marker is used to indicate the voltage change corresponding to the sampling point, which mainly comes from the energy storage release of the distributed capacitance of the long cable after shutdown;

[0172] For sampling points marked with cable energy storage release, a cable energy storage release record is formed. This record is part of the residual voltage record and is not subsequently used for single-phase ground offset judgment.

[0173] When the submersible electric pump is powered by the frequency converter driver, the control chip unit records the frequency output of the frequency converter driver before the shutdown in the last operating sampling window before receiving the shutdown signal.

[0174] After shutdown, if the frequency of the AC component of the three-phase ground sampling voltage does not deviate from the output frequency of the inverter driver before shutdown by more than 10% within no less than three consecutive sampling windows, and does not form a continuous reverse voltage zero-crossing pulse that is opposite to the phase sequence of normal operation, then the control chip unit will assign the corresponding sampling point to the residual mark on the drive side.

[0175] Among them, the drive-side residual marker is used to indicate the voltage change corresponding to the sampling point, which mainly comes from the short-time residual output after the frequency converter driver stops;

[0176] When the three-phase ground sampling voltage drops discontinuously and the reverse voltage zero-crossing pulse does not form a reverse phase sequence, the control chip unit will also assign the corresponding sampling point to the residual mark on the drive side.

[0177] Among them, discontinuous decrease refers to the decrease in the amplitude envelope of the three-phase ground sampling voltage between two adjacent sampling windows, and the decrease is greater than 30% of the amplitude envelope of the previous sampling window;

[0178] Alternatively, the amplitude envelope may decrease again after a plateau lasting for at least two sampling windows during its descent.

[0179] The preset amplitude threshold is determined based on the maximum possible decrease in the amplitude envelope between adjacent sampling windows during the natural attenuation of cable energy storage.

[0180] Since the discharge of cable distributed capacitance is a smooth exponential decay, the decrease between adjacent windows changes gradually. In this embodiment, the preset amplitude threshold is set to 30% of the amplitude envelope of the previous sampling window, which significantly exceeds the normal fluctuation range that may be generated by the natural decay of cable energy storage, thereby effectively distinguishing between the continuous decrease caused by cable energy storage release and the discontinuous decrease caused by the residual of the driver.

[0181] The aforementioned plateau segment refers to the time period in which the change in the amplitude envelope of two adjacent sampling windows is less than 5% of the amplitude envelope of the previous sampling window.

[0182] For sampling points that are assigned a driving-side residual label, a driving-side residual record is formed;

[0183] Among them, the residual record on the driving side is also part of the residual voltage record and is not included in the single-phase ground offset judgment.

[0184] During the normal operation of the submersible electric pump, the control chip unit records the phase sequence direction of normal operation.

[0185] After shutdown, if the phase sequence direction of the reverse voltage zero-crossing pulse is opposite to the normal operating phase sequence direction, then the adjacent zero-crossing interval judgment is entered. Specifically:

[0186] Let the edge times of four consecutive reverse voltage zero-crossing pulses be t1, t2, t3 and t4 respectively, and the corresponding adjacent zero-crossing intervals be T1=t2-t1, T2=t3-t2 and T3=t4-t3;

[0187] When T2 > T1 and T3 > T2, the adjacent zero-crossing interval is considered to increase continuously;

[0188] In this embodiment, K is 3, that is, three consecutive adjacent zero-crossing intervals satisfying an increasing relationship are used as the judgment condition for the motor reverse induction mark;

[0189] When the reverse phase sequence condition and the condition of continuously increasing adjacent zero-crossing intervals are met, the control chip unit further verifies the amplitude envelope change within the same time range:

[0190] If, within the time range of the increasing adjacent zero-crossing intervals T1, T2, and T3, the amplitude envelope of the corresponding sampling window is not higher than the amplitude envelope of the previous sampling window, and the amplitude envelope decreases by more than 5% of the amplitude envelope of the previous sampling window for at least two consecutive sampling windows, then it is determined that the amplitude envelope decreases as the adjacent zero-crossing intervals increase.

[0191] Sampling points that meet the above conditions are marked as having reverse induction of the motor;

[0192] Among them, the motor reverse induction mark is used to indicate the voltage change corresponding to the sampling point, which mainly comes from the induced voltage formed by the well fluid backflow driving the motor to rotate in the reverse direction after the submersible pump stops;

[0193] For the sampling points that are marked with the motor reverse induction, a record of the motor reverse induction voltage is formed;

[0194] Although the reverse induced voltage of the motor may cause changes in the three-phase ground sampling voltage, its source is the induced generation during the shutdown and reversal process, rather than a single-phase insulation drop or a single-phase grounding.

[0195] If this voltage segment is directly used for grounding detection, it can easily lead to false grounding.

[0196] Therefore, sampling points with motor reverse induced voltage records are not included in the single-phase ground offset judgment.

[0197] Since an increase in the interval between adjacent zero crossings represents a decrease in the frequency of the reverse induced voltage, the formula is adopted. As a frequency attenuation coefficient, the equivalent value of the reverse induced energy decreases with the attenuation of the frequency and amplitude of the reverse induced voltage. Specifically:

[0198] The control chip unit generates an equivalent value of the reverse induced energy based on the sampling points of the motor's reverse induction markers. This value represents the magnitude of the impact risk caused by the reverse induced voltage after shutdown to restart. The formula is as follows:

[0199] ;

[0200] in, This is the equivalent value of the reverse induction energy. The number of sampling windows with motor reverse induction markers. The duration of a single sampling window, For the first The interval between adjacent zero crossings of each sampling window, This refers to the zero-crossing interval at the normal operating frequency of the submersible electric pump.

[0201] The safety threshold is determined based on the rated relative-to-ground sampling voltage of the submersible electric pump, the normal operating zero-crossing interval, and the allowable reverse induction ratio, including:

[0202] Assume that, under rated operating conditions, the average amplitude envelope of the three-phase-to-ground sampled voltage is... The allowed reverse induction ratio is Let the minimum verification time before grounding confirmation be... Then the safety threshold The formula is:

[0203] ;

[0204] The above-mentioned allowable reverse induction ratio , which represents the maximum reverse impact energy that the submersible electric pump can tolerate for starting, as a percentage of the rated starting energy;

[0205] The basis is the rotational inertia and mechanical shock resistance characteristics of the submersible electric pump unit and its drive system, while also taking into account the speed of start-stop control;

[0206] For systems with large inertia or that are sensitive to impact, a smaller value can be used to enhance protection. The value range can be 0.05 to 0.15. In this embodiment, λ is preferably 0.10.

[0207] The aforementioned minimum verification time is the shortest time requirement set to continuously meet the single-phase ground offset judgment conditions in order to form a reliable ground fault judgment. It aims to avoid short-term offsets caused by instantaneous disturbances being misjudged as permanent ground faults.

[0208] The minimum verification time is related to the voltage recovery characteristics and insulation withstand level of the submersible pump system, and is typically 1.5s to 3s. In this embodiment, it is preferably 2s.

[0209] When the equivalent value of the reverse induced energy is higher than the safety threshold, the first relay output branch keeps the submersible pump start permission circuit disconnected.

[0210] When the equivalent value of the reverse induction energy is less than or equal to the safety threshold, the reverse state will no longer maintain the start-up interlocking independently.

[0211] If the subsequent ground fault lockout signal still exists, the start-up permission circuit will remain disconnected by the output branch of the second relay.

[0212] The shutdown event recording area unifies the three-phase ground sampling voltage, the reverse voltage zero-crossing pulse edge time, and the adjacent zero-crossing intervals to the same sampling time base, making it easier to distinguish different voltage sources on the same shutdown timeline;

[0213] Cable energy storage release markers are used to eliminate short-time voltage caused by the discharge of distributed capacitance in long cables.

[0214] The drive-side residual marker is used to exclude residual output during the initial shutdown of the frequency converter drive;

[0215] The motor reverse induction marker is used to identify the induced voltage generated by the reverse rotation of the motor driven by the well fluid reflux.

[0216] With the above markings, the single-phase ground offset judgment no longer uses all shutdown sampling points directly, but is performed after excluding non-grounding sources;

[0217] The equivalent value of reverse induced energy further transforms the start-up interlocking from a fixed waiting mode to a judgment mode based on the induced voltage state after shutdown. This avoids erroneous start-up when the reverse inversion has not disappeared and also reduces the invalid downtime caused by fixed waiting.

[0218] Example 3, the third embodiment of the present invention, provides an intelligent monitoring system for the reverse rotation state and grounding fault of a submersible electric pump, comprising:

[0219] The control chip unit is also configured to perform sampling chain reliability verification:

[0220] Under the same sampling time base, compare the zero-crossing time of the three-phase ground sampling voltage of the same electrical phase with the edge time of the reverse voltage zero-crossing pulse. If the time deviation exceeds the limit within N consecutive sampling periods, the sampling chain is marked as unreliable.

[0221] The control chip unit marks sampling points that lack cable energy storage release markers, drive-side residual markers, motor reverse induction markers, and untrusted sampling chain markers as effectively grounded.

[0222] Continuously distributed effective ground fault sampling points constitute an effective ground fault data window;

[0223] Within the aforementioned effective data window for ground faults, for any phase, the offset of its amplitude envelope relative to the average amplitude envelope of the other two phases is calculated. When the offset exceeds the preset offset threshold for an extended period of time, the single-phase ground offset judgment is established, and a ground fault locking signal is generated.

[0224] The output indication unit includes a first relay output branch and a second relay output branch, and their contacts are connected in series to the submersible electric pump start permission circuit.

[0225] The aforementioned first relay output branch closes after the start-up interlocking condition is released;

[0226] The aforementioned second relay output branch remains disconnected after receiving a ground fault lockout signal;

[0227] In this embodiment, based on Embodiment 1 and Embodiment 2, the specific implementation methods of sampling chain reliability verification, grounding effective mark, grounding fault effective data window, single-phase ground offset judgment, and relay interlocking relationship are further explained.

[0228] This embodiment is still applied to the ground control cabinet of a long cable submersible oil pump with a neutral point ungrounded power supply mode, in order to reduce the impact of isolation conversion channel delay, isolation type reverse voltage detection unit drift or instantaneous interference on grounding judgment;

[0229] The above-mentioned sampling chain reliability verification refers to checking the time correspondence between the three-phase ground sampling voltage generated by the isolated voltage conversion unit and the reverse voltage zero-crossing pulse generated by the isolated reverse voltage detection unit under the same sampling time base.

[0230] Among them, the zero-crossing time of the three-phase ground sampling voltage relative to the DC bias reference refers to the timing value corresponding to the AC component of the three-phase ground sampling voltage crossing the DC bias reference.

[0231] The edge time of the reverse zero-crossing pulse refers to the timing value corresponding to the high-low level transition of the reverse zero-crossing pulse;

[0232] When verifying the reliability of the sampling chain, the zero-crossing time of the three-phase ground sampling voltage of the same phase is compared with the edge time of the zero-crossing pulse of the same phase voltage.

[0233] When the isolated back pressure detection unit includes two isolated back pressure detection units for phase A and phase B, the comparison objects are limited to phase A and phase B;

[0234] Phase C does not perform reverse voltage edge comparison separately because there is no corresponding reverse voltage zero-crossing pulse for phase C. The control chip unit does not perform the same comparison.

[0235] Therefore, the reliability of the C-phase sampling chain is confirmed based on the following two conditions:

[0236] First, the comparison results of the sampling chains of phases A and B did not show any unreliable sampling chain markers;

[0237] Secondly, the C-phase sampling voltage did not exhibit any isolated jumps within the same time period;

[0238] The aforementioned isolated jump refers to the situation where the amplitude envelope change of the C-phase ground sampling voltage within a sampling window exceeds 30% of the amplitude envelope of the previous sampling window, while the A-phase and B-phase do not show amplitude changes in the same direction within the same sampling window;

[0239] When the isolated back pressure detection unit includes three isolated back pressure detection units of phase A, phase B and phase C, phase A, phase B and phase C are respectively compared with the zero crossing time and the pulse edge time;

[0240] If the time deviation between the zero-crossing moment of the same phase and the edge of the reverse voltage zero-crossing pulse exceeds the deviation threshold for N consecutive sampling periods, the corresponding sampling point of that phase is assigned an untrusted sampling chain marker.

[0241] Where N is the number of consecutive sampling periods, ranging from 3 to 5, with 3 being the preferred value;

[0242] The deviation threshold is determined based on the sampling period, and is 2 to 5 times the sampling period. When the sampling period is 1ms, the deviation threshold is preferably 5ms.

[0243] The sampling chain untrusted marker is an identifier used to indicate that the corresponding data at that sampling point is not suitable as a basis for grounding judgment;

[0244] After the sampling chain credibility verification is completed, sampling points that were not assigned cable energy release, drive-side residual, motor reverse induction, or untrusted sampling chain markers are assigned grounding valid markers.

[0245] The above-mentioned effective grounding mark refers to the sampling point having eliminated the influence of cable energy storage release, drive-side residual, motor reverse induction, and sampling chain abnormalities, and can be used for single-phase ground offset judgment.

[0246] The continuously distributed effective grounding marker sampling points directly constitute the effective data window for grounding faults;

[0247] If there is an interval between adjacent valid grounding marker sampling points, and the interval does not exceed the preset interval, these sampling points will be included in the same candidate window.

[0248] Within the candidate window, only the time period consisting of consecutive valid grounding marker sampling points is used as the valid grounding fault data window for single-phase ground offset confirmation;

[0249] The interval is only used to prevent the candidate window from being interrupted by a single abnormal sampling point and is not included in the confirmation time of single relative offset judgment.

[0250] The aforementioned preset interval is determined based on the sampling period and is 50 to 100 times the sampling period;

[0251] When the sampling period is 1ms, the preset interval is preferably 100ms;

[0252] It should be noted that the interval is only used to prevent the candidate window from being interrupted by a single abnormal sampling point. In the subsequent single-phase ground offset judgment, the confirmation time only accumulates the actual duration of the valid marker sampling points that are continuously grounded, and does not include the interval in the confirmation time.

[0253] Within the valid data window for ground faults, a single-phase ground offset determination is performed, specifically:

[0254] Calculate the offset of each phase-to-ground sampling voltage relative to the average value of the other two phase-to-ground sampling voltages at the same sampling point, and confirm whether there is a risk of single-phase insulation degradation or single-phase grounding based on the persistence of the offset.

[0255] Taking phase A as an example, the phase A offset is calculated according to the following formula:

[0256] ;

[0257] in, for Phase offset, , as well as For the same sampling point Mutually, phase and Phase-to-ground sampling voltage;

[0258] When the offset of any phase continues to exceed the offset threshold within the confirmation time, the single-phase ground offset judgment is valid.

[0259] The aforementioned preset confirmation time is the duration requirement for continuously meeting the single-phase ground offset condition. It aims to filter out short-term offsets that may be caused by transient voltage disturbances and ensure that a ground fault is only identified when the offset state has a clear continuity.

[0260] Since the confirmation time only accumulates the actual duration of continuous grounding valid marker sampling points, cable energy storage release, drive-side residuals, motor reverse induction, and unreliable sampling points in the sampling chain will not be included in the single-phase ground offset confirmation process.

[0261] The output indication unit includes a first relay output branch and a second relay output branch;

[0262] The first relay output branch is a resettable start-lock branch, used to handle the start-up risk when the reverse induced voltage of the motor has not yet subsided;

[0263] When the first relay output branch releases the start-up lockout, the equivalent value of the reverse induced energy should drop below the safety threshold, and no continuous single-phase ground offset should be formed within the effective data window of the ground fault.

[0264] If no effective grounding marker sampling point has been formed in the shutdown event recording area, the first relay output branch maintains the start-up lockout;

[0265] The second relay output branch is a holding-type ground lockout branch, used to handle the risk of single-phase grounding or continuous insulation degradation;

[0266] After the ground fault lockout signal is generated, the output branch of the second relay remains locked;

[0267] The ground fault locking circuit and the submersible electric pump start-up permission circuit are interlocked by hardware, specifically as follows:

[0268] The normally closed contact of the second relay output branch is connected in series in the ground fault locking circuit, and the ground fault locking circuit is then connected in series with the submersible electric pump start permission circuit.

[0269] When the output branch of the second relay is disconnected, even if the reverse start lockout of the output branch of the first relay has been released, the submersible electric pump start permission circuit still cannot be closed.

[0270] The locked state is released after on-site confirmation that the insulation condition has been restored or after maintenance reset.

[0271] The sampling chain reliability verification ensures that grounding judgment no longer assumes that the isolated voltage transformation unit and the isolated reverse voltage detection unit are always reliable. Instead, it first excludes unreliable data caused by channel delay, comparison shaping anomalies, or sampling drift.

[0272] The effective grounding marker and the effective grounding fault data window limit the single-phase ground offset judgment to the sampling range after excluding cable energy storage release, drive-side residual, motor reverse induction and sampling chain abnormality, which can reduce grounding false lockout caused by shutdown transient voltage.

[0273] The release condition of the first relay output branch is simultaneously associated with the equivalent value of reverse induced energy and the effective data window of ground fault, so as to avoid directly granting start permission after the reverse blocking is released.

[0274] The second relay output branch adopts a holding type lock and is hardware interlocked with the start permit circuit, which can continuously block the submersible pump start permit circuit when the ground fault is not cleared.

[0275] Example 4, refer to Figures 3 to 9 This is the fourth embodiment of the present invention. Based on embodiments 1 to 3, this embodiment further describes the circuit implementation of the high-voltage divider unit, the isolated voltage conversion unit, the isolated reverse voltage detection unit, the control chip unit, the output indicator unit, and the control power supply unit.

[0276] In this embodiment, the device principle block diagram is as follows: Figure 3 As shown, the detection signal of the entire system is split from the high voltage divider unit to the isolated voltage conversion unit and the isolated reverse voltage detection unit, and then sent to the control chip unit for unified acquisition and calculation. The control power supply unit supplies power to each functional unit from bottom to top. The output indicator unit is connected to the control chip unit and is used to output start-up lockout signal and ground fault lockout signal.

[0277] The circuit description corresponding to the above device block diagram is as follows:

[0278] The three-phase high-voltage side signals are first stepped down by the high-voltage divider unit to form low-voltage detection signals. One low-voltage detection signal enters the isolated voltage conversion unit to form a three-phase ground sampling voltage that can be sampled by analog and digital methods. The other low-voltage detection signal enters the isolated reverse voltage detection unit to form a reverse voltage zero-crossing pulse that can be captured by pulse.

[0279] The control chip unit receives two detection results under a unified time base and completes shutdown event recording, status marking, reverse identification, grounding confirmation and interlocking output control, thereby forming a complete hardware detection link from high voltage sampling, isolation transformation, reverse voltage identification, logic judgment to relay output.

[0280] In this embodiment, the high-voltage divider unit is as follows: Figure 4 As shown, the circuit diagram of this unit is as follows:

[0281] High-voltage input terminals J1, J2 and J3 are respectively connected to the high-voltage power supply lines of phase A, phase B and phase C of the submersible pump;

[0282] The three-phase high-voltage input terminals are connected to independent resistor series voltage divider networks. The resistor series voltage divider network consists of three-phase symmetrically arranged voltage divider resistor chains from RN1 to RN66. The low-voltage side of each phase voltage divider resistor chain has three low-voltage taps: INA, INB, and INC. The common reference terminal of the voltage divider network is PE.

[0283] The three-phase voltage divider resistor chains mentioned above are set independently to ensure the consistency of three-phase sampling and reduce inter-phase interference;

[0284] INA, INB, and INC serve as the input signal sources for both the isolated voltage conversion unit and the isolated reverse voltage detection unit, ensuring that the three-phase ground sampling voltage and the reverse voltage zero-crossing pulse have the same voltage source.

[0285] Therefore, this high-voltage divider unit achieves a safe interface between the high-voltage power circuit and the subsequent low-voltage detection circuit by using a pure resistor series voltage divider method, while ensuring high withstand voltage, high input impedance and three-phase symmetrical sampling.

[0286] In this embodiment, the isolated voltage conversion unit is as follows: Figure 5 As shown, the circuit diagram of this unit is as follows:

[0287] Phase A channel includes input matching attenuation resistors R2 and R3, isolation transformer T1, DC bias establishment network composed of REF1V65, R1 and R4, low-pass filter network composed of C4, C5, C7 and R4, R5, and limiting protection network composed of D1.

[0288] Phase B channels include R6, R7, T2, R8, R9, C8, C9, C11, C12, and D3;

[0289] The C-phase channels include R10, R11, T3, R12, R13, R14, R15, R16, R17, C14, C15, C16, C17, and D5;

[0290] The three-phase AC low-voltage input signal is isolated, biased, filtered and limited by its respective channel to form three conditioned low-voltage analog signals, namely UA, UB and UC, which are then sent to the analog-to-digital sampling port of the control chip unit.

[0291] The REF1V65 mentioned above is a common precision voltage reference source, used to provide a consistent DC bias reference for the three-phase sampling channels, enabling the control chip unit to acquire the three-phase ground sampling voltage waveform under a unified reference.

[0292] Therefore, this unit converts the voltage-divided AC signal into a low-voltage bias signal that is compatible with the analog-to-digital sampling range of the microcontroller, while also providing isolation, protection against spike interference, and input protection.

[0293] In this embodiment, the isolated back pressure detection unit adopts a high-sensitivity implementation method, such as... Figure 6 As shown, it includes at least two detection channels, phase A and phase B. The circuit description of this unit is as follows:

[0294] Phase A channel includes an input current limiting and voltage divider network composed of R19, R20 and R25, a filter network composed of R21 and C20, a clamping protection network composed of D6 and D7, an amplifier circuit composed of U6B, a post-stage filter network composed of R26 and C21, a hysteresis comparator shaping circuit composed of R23, R29, R30 and U6A, and an opto-isolated output circuit composed of R24, U5, R18, R22 and C19.

[0295] The B-phase channel includes an input current limiting and voltage divider network composed of R32, R33 and R34, a filter network composed of R24 and C23, an amplifier circuit composed of U6C, a post-stage filter network composed of R39 and C24, a hysteresis comparator shaping circuit composed of R36, R42, R43 and U6D, and an opto-isolated output circuit composed of R37, U7, R31, R35 and C22.

[0296] After the above current limiting, filtering, amplification, comparison shaping and isolation output, the control chip unit obtains the reverse voltage zero-crossing pulse, and identifies the phase sequence direction and frequency change after shutdown based on the pulse sequence and adjacent zero-crossing interval;

[0297] Therefore, this unit converts the low-amplitude reverse voltage signal after the machine stops into a digital pulse signal that is easy for the chip to capture, thereby realizing the identification of the motor's reverse state;

[0298] In this embodiment, the circuit structure of the control chip unit and the wiring terminals is as follows: Figure 7 As shown, the circuit diagram for this part is as follows:

[0299] The control chip unit includes a main control chip U1, a power-on reset circuit composed of R11 and C18, a decoupling circuit composed of C10, C12, C13 and C14, and a debugging interface P2.

[0300] The terminal block includes an external indicator light interface CN3 and an input / output interface CN2. CN2 is equipped with INA, INB, INC and VE input terminals and two sets of relay conversion output terminals T-RL1A, T-RL1B, T-RL1C and T-RL2A, T-RL2B, T-RL2C.

[0301] The control chip unit receives three analog sampling signals (UA, UB, and UC) from the isolated voltage conversion unit and a reverse voltage zero-crossing pulse signal from the isolated reverse voltage detection unit. Following the steps of Examples 1 to 3, it completes the establishment of the shutdown event recording area, status marking, calculation of the equivalent value of reverse induced energy, verification of the sampling chain reliability, construction of the effective data window for ground faults, and relay output control.

[0302] Therefore, this part constitutes the core of the entire system's logical operation and external interface.

[0303] In this embodiment, the output indication unit is as follows: Figure 8 As shown, the circuit diagram of this unit is as follows:

[0304] It includes two relay drive circuits and three LED indicator circuits;

[0305] The upper relay drive circuit consists of R5, R6, Q1, C30, D2 and RL1, while the lower relay drive circuit consists of R12, R17, Q2, C31, D4 and RL2. The two circuits together form two relay output branches for external interlocking control.

[0306] The LED indicator circuit consists of R49 and LED1, R50 and LED2, and R51 and LED3, and is used to display the working status of the device, such as power-on, reverse lock-up, or ground lock-up.

[0307] Both relay output branches are controlled by the control chip unit. One branch is used to output the start-lock signal, and the other branch is used to output the ground fault lockout signal.

[0308] Therefore, the output indicator unit can not only display the status, but also directly participate in the hardware interlocking of the submersible pump start-up permission circuit or fault lockout circuit through the relay contacts.

[0309] In this embodiment, the control power supply unit is as follows: Figure 9 As shown, the circuit diagram of this unit is as follows:

[0310] It includes an AC input terminal CN1, a fuse F1, a varistor RV1, filtering devices C6 and L1, an isolated AC-DC power module U3, and a linear regulator U2;

[0311] After the 220V AC input is connected via CN1, it first undergoes overcurrent and surge protection through F1 and RV1, and then is filtered by L1 and C6 before being sent to U3. U3 outputs an isolated 5V DC power supply.

[0312] One 5V DC power supply directly supplies the relay and isolation detection circuits, while the other is regulated by U2 to form a 3.3V DC power supply, which is used to power the control chip unit and related logic circuits.

[0313] This ensures that the high-pressure sampling side and the low-pressure control side are isolated in terms of power supply, thereby improving the operational stability of the entire monitoring system under the high-pressure environment of the well site.

[0314] Through the above circuit structure setup, this embodiment translates the device principle block diagram and the circuit diagrams of each functional unit into specific hardware implementations corresponding to Embodiments 1 to 3:

[0315] The high-voltage divider unit provides a clear voltage divider structure for sampling three-phase high-voltage signals; the isolated voltage conversion unit provides a clear isolation, bias, and limiting structure for sampling three-phase ground voltages; the isolated reverse voltage detection unit provides a clear amplification, comparison, shaping, and isolation output structure for acquiring reverse voltage zero-crossing pulses; and the control chip unit and output indicator unit provide a clear execution structure for external interlocking of start-up lockout signals and ground fault lockout signals, enabling the present invention to have a directly implementable circuit solution.

Claims

1. An intelligent monitoring system for the reverse rotation state and grounding fault of a submersible electric pump, characterized in that, include: High voltage divider unit, isolated voltage conversion unit, isolated reverse voltage detection unit, control chip unit, output indicator unit, and control power supply unit; The high-voltage terminal of the aforementioned high-voltage divider unit is used to connect to the three-phase power supply line of the submersible electric pump, and its low-voltage tap terminal is simultaneously connected to the three-phase input terminals of the isolated voltage conversion unit and the isolated back pressure detection unit. The aforementioned control chip unit is configured as follows: The three-phase ground sampling voltage is obtained from the isolated voltage conversion unit through the analog-to-digital sampling port, and the reverse voltage zero-crossing pulse is obtained from the isolated reverse voltage detection unit through the pulse capture port. The sampling time base of the analog-to-digital sampling port and the aforementioned pulse capture port is consistent. After receiving the shutdown signal of the submersible electric pump, a shutdown event recording area is established. Based on the envelope change characteristics of the three-phase ground sampling voltage and the phase sequence characteristics of the reverse voltage zero-crossing pulse, under a unified sampling time base, the sampling points corresponding to cable energy storage release, drive-side residual or motor reverse induction after shutdown are marked and excluded to form an effective ground fault data window for ground fault judgment. Within the valid data window for ground faults, a single-phase ground offset judgment is performed, and based on the distinction result, a start-up blocking signal and a ground fault lockout signal are generated.

2. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 1, characterized in that: The control chip unit sets status markers for the sampling points, including cable energy storage release marker, drive-side residual marker, motor reverse induction marker, and grounding effective marker; Sampling points with cable energy storage release markers, drive-side residual markers, and motor reverse induction markers are not included in the single-phase ground offset judgment.

3. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 2, characterized in that: The control chip unit marks sampling points that meet the following conditions as cable energy storage release: The amplitude envelope of the three-phase ground sampling voltage decreases synchronously after shutdown; The rate of decline in the voltage change characteristic decreases with time, and within the corresponding time period, the pulse capture port does not capture continuous reverse voltage zero-crossing pulses with reverse phase sequence.

4. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 3, characterized in that: After excluding sampling points with cable energy storage release markers, the control chip unit marks sampling points that meet one of the following conditions as drive-side remnants: When powered by the frequency converter driver, the AC component of the three-phase ground sampling voltage has a short-term holding characteristic that matches the frequency converter driver output frequency recorded before shutdown, and no reverse phase sequence pulse is formed; The three-phase ground sampling voltage showed a discontinuous decrease, and the reverse voltage zero-crossing pulse did not form a reverse phase sequence; Discontinuous descent refers to the decrease in amplitude envelope between adjacent sampling windows exceeding a preset amplitude threshold, or the occurrence of a transient plateau before resuming descent during the amplitude envelope descent process. The interval between adjacent zero-crossing pulses of the reverse voltage did not increase continuously.

5. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 2, characterized in that: The control chip unit marks sampling points that simultaneously meet the following conditions as motor reverse induction and generates a start-lock signal: The phase sequence direction of the reverse voltage zero-crossing pulse is opposite to the pre-stored normal operation phase sequence direction; The interval between adjacent zero-crossing pulses of the reverse voltage increases over K consecutive zero-crossing cycles, where K is the number of zero-crossing cycles. The voltage amplitude envelope decreases as the interval between adjacent zero crossings increases.

6. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 5, characterized in that: The control chip unit forms an equivalent value of reverse induction energy based on sampling points marked with motor reverse induction. The equivalent value of the reverse induction energy is given by the following formula: ； in, This is the equivalent value of the reverse induction energy. The number of sampling windows with motor reverse induction markers. The duration of a single sampling window, For the first The interval between adjacent zero crossings of each sampling window, This refers to the zero-crossing interval at the normal operating frequency of the submersible electric pump. For the first Within a sampling window, the voltages of phase A, phase B, and phase C to ground are sampled, and the positive sequence voltage amplitude is obtained by calculating using the symmetrical component method. When the equivalent value of the reverse induced energy is higher than the safety threshold, the output branch of the first relay is controlled by the start-lock signal, so that the start-permission circuit of the submersible pump remains open.

7. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 2, characterized in that: The control chip unit is also configured to perform sampling chain reliability verification: Under the same sampling time base, compare the zero-crossing time of the three-phase ground sampling voltage of the same electrical phase with the zero-crossing pulse edge time of the reverse voltage. If the time deviation exceeds the limit within N consecutive sampling periods, the sampling chain is marked as unreliable, where N is the number of consecutive sampling periods.

8. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 7, characterized in that: The control chip unit marks sampling points that lack cable energy storage release markers, drive-side residual markers, motor reverse induction markers, and untrusted sampling chain markers as effectively grounded. The continuously distributed effective ground fault sampling points constitute the effective ground fault data window.

9. The intelligent monitoring system for reverse rotation state and grounding fault of submersible electric pump as described in claim 8, characterized in that: Within the effective data window of the ground fault, for any phase, the offset of its amplitude envelope relative to the average amplitude envelope of the other two phases is calculated. When the offset exceeds the preset offset threshold for a preset confirmation time, the single-phase ground offset judgment is established, and a ground fault locking signal is generated.

10. The intelligent monitoring system for reverse rotation state and grounding fault of the submersible electric pump as described in claim 9, characterized in that: The output indication unit includes a first relay output branch and a second relay output branch, and their contacts are all connected in series to the submersible electric pump start permission circuit. The aforementioned first relay output branch closes after the start-up interlocking condition is released; The output branch of the second relay mentioned above remains disconnected after receiving a ground fault lockout signal.

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