CN220084968U - Ground impedance test circuit and ground impedance test system - Google Patents

Abstract

The embodiment of the utility model relates to the field of control of safety inspection testers, and discloses a grounding impedance testing circuit and a grounding impedance testing system. The ground impedance test circuit includes: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port; the suppression module is used for suppressing alternating current test voltage between the first port and the second port; the detection module is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state; the delay module is used for judging whether to provide time delay for the switching module according to the working state of the detection module; the switching module is used for detecting whether the delay module provides time delay or not and controlling the working state of the switching module according to the delay detection result; and the output module is used for controlling the output state of the third port according to the working state of the switching module.

Description

Ground impedance test circuit and ground impedance test system

Technical Field

The embodiment of the utility model relates to the field of control of safety standard testers, in particular to a grounding impedance testing circuit and a grounding impedance testing system.

Background

At present, a 'safety inspection' station is usually arranged on a production line of an electrical equipment production enterprise, and naturally, the station also comprises a grounding impedance parameter test. The general process is as follows: when a grounding impedance testing link is entered, an operator is prompted by acoustic signals and/or optical signals to directly contact and communicate a CURRENT probe with a related TEST point of tested equipment, then a 'TEST (or START)' button on a front panel of a safety tester is pressed to START a grounding impedance testing process, the safety tester outputs an alternating CURRENT testing CURRENT source I1 with an open circuit voltage not higher than 8V50 Hz/60Hz through a 'CURRENT probe', the alternating CURRENT testing CURRENT source I1 is applied to the related TEST point of the tested equipment through the 'CURRENT probe', and the alternating CURRENT is returned to a 'RETURN' port of the safety tester through the tested 'grounding impedance', so that a large CURRENT of several to tens of amperes is formed; the safety tester monitors and analyzes the AC voltage drop between the CURRENT port and the RETURN port simultaneously, and can judge whether the grounding impedance of the tested equipment is higher than the safety limit value.

In order to eliminate the above-described actuation step by the operator pressing the "TEST button" on the front panel, fig. 1 presents a solution that is currently more common. In the above scheme, an "EXTECH 7440 grounding impedance test current probe automatic starting system" is provided, comprising: the current probe grounding detection circuit, FX1S series PLC controller, RS-232 serial port, PC computer, IEEE-488 serial port, DC power supply and other links have the functions that: the electrical connection state of the current probe is sent to the GPIB INTERFACE of the safety tester to automatically start the grounding impedance test. The working principle is as follows: when the CURRENT probe contacts and is communicated with the tested equipment, the CURRENT probe grounding detection circuit outputs a logic H level, the FX1S series PLC controller is connected with a PC computer through an RS-232 serial port, the PC computer is delayed by a time T, and then is connected with a GPIB INTERFACE of an EXTECH 7440 safety dielectric analyzer through an IEEE-488 serial port, a test power switch SW1 is closed, an alternating CURRENT test CURRENT source I1 is output to a CURRENT port, and the CURRENT is returned to a RETURN port through the tested equipment; and then analyzing the alternating CURRENT voltage drop between the CURRENT port and the RETURN port to judge whether the grounding impedance of the tested equipment is higher than the safety limit value.

The automatic starting system has simple functions, but one control link cannot be reduced, and high-cost circuit modules such as a PC (personal computer) and a PLC (programmable logic controller) are needed to be used, so that the defects of large equipment size, high cost, long control link, poor reliability and the like of the automatic starting system are obvious.

Disclosure of Invention

The embodiment of the utility model aims to provide a grounding impedance testing circuit and a grounding impedance testing system, which can simplify the grounding impedance testing circuit, greatly reduce the equipment volume, reduce the cost of the grounding impedance testing circuit and improve the reliability of the grounding impedance testing circuit.

To solve the above technical problem, an embodiment of the present utility model provides a ground impedance test circuit, including: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port; the suppression module is used for suppressing alternating current test voltage between the first port and the second port; the detection module is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state; the delay module is used for judging whether to provide time delay for the switching module according to the working state of the detection module; the switching module is used for detecting whether the delay module provides the time delay or not and controlling the working state of the switching module according to a delay detection result; the output module is used for controlling the output state of the third port according to the working state of the switching module.

Embodiments of the present utility model also provide a ground impedance test circuitry, the system comprising: the device comprises a safety dielectric analyzer module, tested equipment connected with the safety dielectric analyzer module and the grounding impedance testing circuit; the safety dielectric analyzer module is used for testing the grounding impedance of the tested equipment based on the grounding impedance testing circuit.

In an embodiment of the present utility model, a ground impedance test circuit includes: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port; the suppression module is used for suppressing alternating current test voltage between the first port and the second port; the detection module is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state; the delay module is used for judging whether to provide time delay for the switching module according to the working state of the detection module; the switching module is used for detecting whether the delay module provides time delay or not and controlling the working state of the switching module according to the delay detection result; the output module is used for controlling the output state of the third port according to the working state of the switching module; the utility model realizes all the electrical functions of an automatic starting system for carrying out the grounding impedance test, which are formed by a current probe grounding detection circuit, an FX1S series PLC controller, an RS-232 serial port, a PC computer, an IEEE-488 serial port, a direct current power supply and the like in the prior art, through five hardware circuit modules, can reduce the cost of the grounding impedance test circuit while simplifying the grounding impedance test circuit, and simultaneously can greatly reduce the volume of equipment and improve the reliability of the grounding impedance test circuit because no computer or software is needed.

Drawings

One or more embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings.

FIG. 1 is a schematic diagram of a prior art ground impedance testing system;

FIG. 2 is a schematic diagram of a ground impedance testing circuit according to an embodiment of the present utility model;

FIG. 3 is a schematic diagram of a second embodiment of a ground impedance testing circuit according to the present utility model;

FIG. 4 is a schematic diagram of a ground impedance testing system according to an embodiment of the present utility model;

FIG. 5 is a schematic waveform diagram of the current probe in the ground impedance test system of FIG. 4.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present utility model more apparent, the embodiments of the present utility model will be described in detail below with reference to the accompanying drawings. However, it will be understood by those of ordinary skill in the art that in various embodiments of the present utility model, numerous specific details are set forth in order to provide a thorough understanding of the present utility model. However, the claimed technical solution of the present utility model can be realized without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not be construed as limiting the specific implementation of the present utility model, and the embodiments can be mutually combined and referred to without contradiction.

The embodiment of the utility model relates to a grounding impedance testing circuit, which is applied to any grounding impedance testing system, as shown in fig. 2, and specifically comprises: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port.

In an example implementation, the suppression module is connected to the first port and the second port, respectively, for suppressing an ac test voltage between the first port and the second port; the first port is a port IN, the second port is a port GND, and the first port and the second port can be regarded as input ports (IN-GND).

In an example implementation, the detection module is connected with the suppression module, and is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state; the circuit state between the first port and the second port comprises three states of open circuit, short circuit and application of alternating current test voltage; when the circuit state between the first port and the second port is an open state, the suppression module can provide bias current for the detection module, and the working state of the detection module is controlled to be a conducting state based on the bias current provided by the suppression module; when the circuit state between the first port and the second port is a short circuit state, the working state of the control detection module is a cut-off state; when the circuit state between the first port and the second port is the alternating current test voltage, controlling the working state of the detection module to be a cut-off state; when the working state of the detection module is in an off state, the working state of the switching module is in an on state, the switching module can provide positive feedback (namely, apply bias voltage) to the detection module, and if the applied bias voltage is greater than a threshold value, the working state of the detection module can be kept in the off state continuously, wherein the threshold value can be set according to the test requirement.

In an example implementation, the delay module is respectively connected with the detection module and the second port, and is used for judging whether to provide time delay for the switching module according to the working state of the detection module; the working state of the detection module comprises two states, namely a cut-off state and a conduction state; when the working state of the detection module is a conducting state, the delay module does not need to provide time delay; when the working state of the detection module is in a cut-off state, the delay module needs to provide a time delay of T seconds; in the period of T seconds, whether the first port and the second port are on or off does not influence the working state of the switching module, namely the utility model has the function of resisting the contact shake of the input end.

In an example implementation, the switching module is connected with the delay module, and is used for detecting whether the delay module provides time delay and controlling the working state of the switching module according to the delay detection result; when the delay module is detected to provide the time delay of T seconds for the switching module, the working state of the switching module is controlled to be in a cut-off state within the time delay of T seconds, and the working state of the switching module is controlled to be in a conduction state after the time delay of T seconds; and when the delay module is detected not to provide the time delay of T seconds for the switching module, controlling the working state of the switching module to be a conducting state.

In an example implementation, the output module is connected to the switching module, the third port and the second port, respectively, and is configured to control an output state of the third port according to an operating state of the switching module; the output state of the third port is related to the working state of the switching module; when the working state of the switching module is a cut-off state, controlling the output state of the third port to be a high-resistance state; when the working state of the switching module is a conducting state, controlling the output state of the third port to be a low-resistance state; the third port is the port OUT, and the third port and the second port can be regarded as output ports (OUT-GND).

In an embodiment of the present utility model, a ground impedance test circuit includes: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port; the suppression module is used for suppressing alternating current test voltage between the first port and the second port; the detection module is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state; the delay module is used for judging whether to provide time delay for the switching module according to the working state of the detection module; the switching module is used for detecting whether the delay module provides time delay or not and controlling the working state of the switching module according to the delay detection result; the output module is used for controlling the output state of the third port according to the working state of the switching module; the utility model realizes all the electrical functions of an automatic starting system for carrying out the grounding impedance test, which are formed by a current probe grounding detection circuit, an FX1S series PLC controller, an RS-232 serial port, a PC computer, an IEEE-488 serial port, a direct current power supply and the like in the prior art, through five hardware circuit modules, can simplify the grounding impedance test circuit, greatly reduce the equipment volume and simultaneously reduce the cost of the grounding impedance test circuit, and meanwhile, can improve the reliability of the grounding impedance test circuit because a computer and software are not needed.

The embodiment of the utility model relates to a grounding impedance testing circuit, which is applied to any grounding impedance testing system, as shown in fig. 3, and specifically comprises: the device comprises a first port IN, a second port GND, a suppression module comprising a fourth resistor R4, a fifth resistor R5 and a first capacitor C1, a detection module comprising a second triode Q2, a delay module comprising a second resistor R2 and a second capacitor C2, a switching module comprising a first triode Q1, an output module comprising a first resistor R1 and a third resistor R3 and a third port OUT.

In an example implementation, the ground impedance test circuit may be divided into 7 networks, network n1: the port 1 of the first resistor R1, the port 1 of the second resistor R2 and the port 1 of the fourth resistor R4 are connected with the third port OUT; network n2: the port 2 of the third resistor R3, the port 2 of the first capacitor C1 and the port 2 of the second capacitor C2 are connected to the second port GND; network n3: the port 2 of the fourth resistor R4 and the port 1 of the fifth resistor R5 are connected to the first port IN; network n4: the port 2 of the first resistor R1 is connected with the collector C of the first triode Q1; network n5: an emitter E of the second triode Q2 and a port 1 of the third resistor R3 are connected with the emitter E of the first triode Q1; network n6: the collector C of the second triode Q2, the port 2 of the second resistor R2 and the port 1 of the second capacitor C2 are connected with the base B of the first triode Q1; network n7: the port 2 of the fifth resistor R5 and the port 1 of the first capacitor C1 are connected to the base B of the second transistor Q2.

IN an example implementation, the fifth resistor R5 and the first capacitor C1 form a resistor-capacitor voltage divider, which is used for suppressing the ac test voltage at the input port, and when the ac test voltage is applied between the first port IN and the second port GND, the capacitance reactance of the first capacitor C1 is small, so that the ac voltage amplitude at both ends of the first capacitor C1 can be effectively suppressed.

IN an example implementation, the second transistor Q2 may be regarded as an input state switch, and is configured to detect the on-off state of the first port IN and the second port GND; when the first port IN and the second port GND are IN an open state, the base bias current provided by the fourth resistor R4 and the fifth resistor R5 IN series enables the second triode Q2 to be IN a saturated conduction state; when the first port IN and the second port GND are IN a short circuit state, the second triode Q2 is IN a cut-off state; when alternating test voltage is applied between the first port IN and the second port GND, the second triode Q2 is cut off; when the second transistor Q2 is in the off state, the first transistor Q1 is in the on state, the first transistor Q1 may provide positive feedback (i.e., apply bias voltage) to the second transistor Q2, and if the applied bias voltage is greater than a threshold, the second transistor Q2 may be continuously kept in the off state, where the threshold may be set according to the test requirement.

In an example implementation, the function of the second resistor R2 and the second capacitor C2 is to provide a T seconds time delay; when the second triode Q2 is in a cut-off state, a time delay of T seconds is provided by the second resistor R2 and the second capacitor C2, the first triode Q1 is in the cut-off state within the time delay of T seconds, and the first triode Q1 is turned on again after the time delay of T seconds is finished; IN the period of T seconds, the on/off state of the input port (IN-GND) does not affect the off state of the first transistor Q1, i.e., the present circuit has a function of resisting the contact jitter of the input port.

In an example implementation, the first transistor Q1 functions as an output resistor network switch, and the on and off of the first transistor Q1 is determined based on the T seconds time delay provided by the second resistor R2 and the second capacitor C2.

In an example implementation, the functions of the first resistor R1 and the third resistor R3 are: when the first triode Q1 is saturated and conducted, the output port (OUT-GND) is in a low-impedance state (R1+R3), wherein the third resistor R3 is also used as a direct current coupling resistor; when the second transistor Q2 is turned off and the first transistor Q1 is saturated and turned on, the voltage drop (v5=4.91V) across the third resistor R3 provides a reverse bias voltage to the second transistor Q2, and at this time, the second transistor Q2 may be turned back on only when the base level of the second transistor Q2 is higher than the reverse bias voltage; the capacity of the normal logic function of the circuit, which is not interfered by the alternating voltage of the input port, is greatly enhanced by being matched with the suppression module of the resistor-capacitor voltage divider formed by the fifth resistor R5 and the first capacitor C1.

In an example implementation, the fourth resistor R4 and the fifth resistor R5 function as a base bias resistor for the second transistor Q2, providing a base bias current for the second transistor Q2; when the current probe is open, the base bias current provided by the fourth resistor R4 and the fifth resistor R5 in series causes the second transistor Q2 to be saturated on.

In an example implementation, the present circuit is a 3-port circuit: a first port IN, a second port GND, and a third port OUT; the first port IN and the second port GND constitute an input port (IN-GND), and the third port OUT and the second port GND constitute an output port (OUT-GND); the input port has 3 working states: open circuit, short circuit, apply and is not higher than 8V50/60Hz alternating current test voltage; the output port has 2 states: high resistance state, low resistance state (r1+r3). The state correspondence of the input port and the output port of the present circuit is shown in table 1.

Table 1 state correspondence table of input port and output port

Input port (IN-GND)	Output port (OUT-GND)
		Open circuit	High resistance
Short circuit	Low resistance (R1+R3)
		8V50/60Hz AC test voltage	Low resistance (R1+R3)

In an exemplary implementation, the ground impedance test circuit provided in the embodiments of the present utility model has 3 states, state one: when the input port (IN-GND) is open, the base bias current provided by the fourth resistor R4 and the fifth resistor R5 IN series enables the second triode Q2 to be saturated and conductive, enables the first triode Q1 to be cut off, and enables the output port (OUT-GND) to be IN a high-resistance state; state two: when the input port (IN-GND) is short-circuited, the voltage at two ends of the fifth resistor R5 is zero, the second triode Q2 is cut off due to the loss of base bias current, the second resistor R2 and the second capacitor C2 provide a time delay of T seconds, and then the first triode Q1 is IN saturated conduction again, so that the first resistor R1 is connected with the third resistor R3 IN series, and the output port (OUT-GND) is IN a low-resistance state (R1+R3); state three: when an alternating current test voltage of not higher than 8V50/60Hz is applied to the input port (IN-GND), the alternating current capacitance of the first capacitor C1 is very small, the voltage division effect of the resistor-capacitor voltage divider formed by the fifth resistor R5 and the first capacitor C1 on the alternating current test voltage effectively inhibits the amplitude of the alternating current voltage at two ends of the first capacitor C1, the average value of the alternating current test voltage of not higher than 8V50/60Hz is zero, so that the direct current component of the voltage at two ends of the fifth resistor R5 is zero, the second triode Q2 is further turned off, the first triode Q1 is saturated and conducted, the first resistor R1 is connected with the third resistor R3 IN series, and the output port (OUT-GND) is IN a low-resistance state (R1+R3).

According to the embodiment of the utility model, on the basis of other embodiments, all the electrical functions of the existing comparison technical scheme can be covered only by 9 discrete components (2 NPN triodes, 5 resistors and 2 capacitors): the method comprises the steps of obtaining a working power supply, detecting the grounding of a current probe, delaying time T, resisting contact shake of the current probe, closing a test power switch SW1, outputting an alternating current test current source I1 and automatically starting a test process; the advantages in terms of equipment cost, bulk, simplicity, reliability, etc. are apparent.

The embodiment of the present utility model relates to a ground impedance testing system, and details of the ground impedance testing system of the present embodiment are specifically described below, which are provided for understanding only, but not necessarily for implementing the present embodiment, and fig. 4 is a schematic structural diagram of the ground impedance testing system of the present embodiment, including: the device comprises a safety dielectric analyzer module, a grounding impedance testing circuit and tested equipment.

In an example implementation, the safety dielectric analyzer module may employ an EXTECH 7440 safety dielectric analyzer, an equivalent relationship diagram of the interior of the instrument is shown in fig. 4, and the front panel portion includes: a CURRENT output port CURRENT and a CURRENT loop port RETURN; the rear panel portion includes: INPUT inverter IC1 at the "REMOTE I/O SIGNAL INPUT" interface INPUT-3 port; an equivalent pull-up resistor R6; +24v dc power V1; test power switch SW1, ac test CURRENT source I1, CURRENT output port CURRENT, and CURRENT loop port RETURN.

In an example implementation, the ground impedance test circuit in the ground impedance test system is any one of the ground impedance test circuits of the embodiments of the present utility model.

In an example implementation, an equivalent schematic diagram of the ground impedance of the device under test is shown in fig. 4, and is connected to the safety dielectric analyzer through a current probe.

In an example implementation, the electrical principle in the present system is: the first port IN of the grounding impedance test circuit is connected with the CURRENT port of EXTECH 7440, the main electrical characteristics of the CURRENT port are that the CURRENT port presents high impedance when not started, and the output open-circuit voltage is not higher than 8V50 Hz/60Hz alternating CURRENT test CURRENT source I1 when started; the third port OUT of the grounding impedance testing circuit is connected with the INPUT-3 port of the remote control INPUT interface of EXTECH 7440, and the main electrical characteristics of the INPUT-3 port are open circuit voltage (V1) +24V, short circuit current 2mA and equivalent pull-up resistor (R6) 12kΩ; the input characteristic of the inverter IC1 in the safety dielectric analyzer is an open circuit (H) level >18.5V, and a start-up (L) level <17.5V.

In an example implementation, during a ground impedance test of a device under test, a measured waveform of a current probe is shown in fig. 5, specifically, at time t1: the current probe is in contact with and communicated with a test point of the tested equipment; the first port IN is short-circuited with the second port GND, and the input port voltage vin=0; time t2: after a delay of 944mS, the ac test current source I1 is applied to the test point of the "device under test" to form an ac test voltage (vin=i1×the measured ground impedance) at the first port IN; time t3: ending the network impedance test and analysis, closing the alternating current test current source I1, wherein vin=0; time t4: the current probe is disconnected with the test point of the tested equipment; time t5: the input port IN reverts to the initial state.

In an example implementation, the ground impedance test circuit of the ground impedance test system has a total of two circuit states, circuit state one: the "current probe" is open: the fourth resistor R4 and the fifth resistor R5 are connected in series to charge the first capacitor C1, the base level Vb2 of the second triode Q2 rises, the second triode Q2 is saturated and turned on, and the first triode Q1 is turned off; the output port is in a high-resistance state; at this time, the steady-state levels of the networks n1 to n7 are respectively: vn1=23.08v; vn2=0v; vn3=6.61V; vn4=23.08v; vn5=0.39v; vn6=0.42V; vn7=0.80V; network level vn1=23.08v is equivalent to inverter IC1 input "open circuit (H) level". Circuit state two: the current probe is in contact and communication with the tested equipment: the first port IN is short-circuited with the second port GND, the base level Vb2=0V of the second triode Q2, the second triode Q2 is cut off, the second resistor R2 charges the second capacitor C2, and the first triode Q1 is saturated and conducted after the time T delays; the output port (OUT-GND) presents a low impedance (r3+r1=12.6kΩ); at this time, the steady-state levels of the networks n1 to n7 are respectively: vn1=12.17V; vn2=0v; vn3=0v; vn4=5.05v; vn5=4.91V; vn6=5.37V; vn7=0v; network level vn1=12.17v, equivalent to IC1 input "start (L) level"; then, the test power switch SW1 is turned on, the EXTECH 7440 outputs an ac test CURRENT source I1 with an open-circuit voltage not greater than 8V through the CURRENT port, and the safety tester module monitors and analyzes the ac voltage drop between the CURRENT port and the RETURN port at the same time, so as to determine whether the ground impedance of the tested device is higher than the safety limit value, the fifth resistor R5 and the first capacitor C1 form a voltage divider for the ac voltage drop of the CURRENT port, and under the conditions that the fifth resistor r5=180kΩ, the first capacitor c1=1uf, vin < = V, f =50 Hz, the base level Vb2< = 0.14Vac of the second triode Q2; in addition, at this time, v5=4.91V, the emitter junction of the second triode Q2 is reverse biased, and the second triode Q2 is still in a deep cut-off state, that is, the ac test current source I1 does not interfere with the logic state of the circuit; the non-zero level Vn1 in the two circuit states provides the working power supply for the circuit.

It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples of carrying out the utility model and that various changes in form and details may be made therein without departing from the spirit and scope of the utility model.

Claims (10)

1. A ground impedance test circuit, the circuit comprising: the device comprises a first port, a second port, a suppression module, a detection module, a delay module, a switching module, an output module and a third port;

the suppression module is used for suppressing alternating current test voltage between the first port and the second port;

the detection module is used for detecting the circuit state between the first port and the second port and controlling the working state of the detection module according to the working state of the switching module and the detection result of the circuit state;

the delay module is used for judging whether to provide time delay for the switching module according to the working state of the detection module;

the switching module is used for detecting whether the delay module provides the time delay or not and controlling the working state of the switching module according to a delay detection result;

the output module is used for controlling the output state of the third port according to the working state of the switching module.

2. The ground impedance test circuit of claim 1, wherein the detection module is further configured to control an operating state of the detection module to be a conductive state based on a bias current provided by the suppression module when the state detection result is an open state;

the detection module is further used for controlling the working state of the detection module to be a cut-off state when the state detection result is a short circuit state;

and the detection module is also used for controlling the working state of the detection module to be a cut-off state when the state detection result is that the alternating current test voltage is applied.

3. The ground impedance test circuit of claim 2, wherein the detection module is further configured to control the operation state of the detection module to be an off state when the operation state of the detection module is an off state, the operation state of the switching module is an on state, and the bias voltage of the switching module satisfies a preset condition.

4. The ground impedance test circuit of claim 1 wherein the delay module is further configured to provide the time delay to the switching module when the operational state of the detection module is an off state.

5. The ground impedance test circuit of claim 1, wherein the switching module is further configured to control an operating state of the switching module to be an off state during the time delay when the delay detection result is to provide a time delay;

and the switching module is also used for controlling the working state of the switching module to be a conducting state when the delay detection result is that no time delay is provided.

6. The ground impedance test circuit of claim 1, wherein the output module is further configured to control the output state of the third port to be a high-impedance state when the operating state of the switching module is an off state;

and the output module is further used for controlling the output state of the third port to be a low-resistance state when the working state of the switching module is a conducting state.

7. The ground impedance test circuit of claim 1 wherein the rejection module is connected to the first port, the detection module is connected to the rejection module and the switching module, respectively, the delay module is connected to the detection module, the switching module is connected to the delay module, the output module is connected to the switching module, respectively, the third port is connected to the rejection module and the delay module and the output module, and the second port is connected to the rejection module and the delay module and the output module.

8. The ground impedance test circuit of claim 1 wherein the suppression module comprises a fourth resistor, a fifth resistor, and a first capacitor, the detection module comprises a second transistor, the delay module comprises a second resistor and a second capacitor, the switching module comprises a first transistor, and the output module comprises a first resistor and a third resistor.

9. The ground impedance test circuit of claim 8, wherein one end of the first resistor, one end of the second resistor, and one end of the fourth resistor are connected to the third port, the other end of the third resistor, the other end of the first capacitor, and the other end of the second capacitor are connected to the second port, the other end of the fourth resistor and one end of the fifth resistor are connected to the first port, the other end of the first resistor is connected to the collector of the first triode, the emitter of the second triode and one end of the third resistor are connected to the emitter of the first triode, the collector of the second triode is connected to the other end of the second resistor and one end of the second capacitor are connected to the base of the first triode, and the other end of the fifth resistor and one end of the first capacitor are connected to the base of the second triode.

10. A ground impedance testing system, the system comprising: a safety dielectric analyzer module, a device under test connected to the safety dielectric analyzer module, and the ground impedance test circuit of any one of claims 1-9;

the safety dielectric analyzer module is used for testing the grounding impedance of the tested equipment based on the grounding impedance testing circuit.