Cable insulation state detection method

Abstract

The invention discloses a cable insulation state detection method, and the method comprises the steps: controlling a first relay and a second relay to maintain a normally open state and a third relay to maintain a normally closed state after a to-be-measured cable is connected with a cable wiring module, and enabling the to-be-measured cable to be in a charging state, obtaining a first polarization current of the to-be-measured cable through a first current measurement module; the first relay is adjusted to be in a normally-closed state, so that the to-be-measured cable is in a discharging state, and first depolarization current of the to-be-measured cable is obtained through a first current measurement module; the third relay is adjusted to be in a normally-open state, and the first voltage of the cable to be measured is obtained through the voltage measurement module; and determining the insulation state of the to-be-measured cable according to the first polarization current, the first depolarization current and the first voltage of the to-be-measured cable. According to the invention, simultaneous or sequential measurement of polarization current, depolarization current and voltage of the to-be-measured cable can be realized, and the accuracy and convenience of insulation state analysis of the to-be-measured cable are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable insulation state detection, and in particular to a method for detecting the insulation state of a cable. Background Art

[0002] Power cables are widely used because of their stable transmission and economy, and laying them underground reduces the occupation of space resources. Existing power cables are mainly cross-linked polyethylene (XLPE) cables. However, cables are affected by factors such as electricity, heat, and mechanical stress in complex environments, and may have insulation defects or structural damage, resulting in insulation aging and reducing the performance of the cables.

[0003] Regarding the problem of cable insulation aging, there are various methods for detection. Classified according to the degree of damage to the equipment caused by the test, it can be divided into non-destructive tests and destructive tests. Non-destructive tests do not damage the insulation material and can be repeatedly tested. The dielectric response method is a non-destructive test. By measuring the polarization / depolarization current (PDC) of the cable, the return voltage (RV), and the frequency domain dielectric spectroscopy (FDS), the insulation state of the cable is studied. By calculating and analyzing the polarization / depolarization current of the measured cable, the insulation resistance, aging factor, and trap parameters of the cable can be obtained, and then the insulation condition of the cable can be evaluated; the insulation state of the equipment can be evaluated using the return voltage parameter; the frequency domain dielectric spectroscopy method measures the polarization response of the cable insulation layer under an alternating current electric field, detects the dielectric loss frequency characteristics and capacitance changes of the insulation system in a relatively wide frequency range, and obtains the insulation condition of the equipment according to the dielectric loss and capacitance indicators.

[0004] The existing Chinese patent CN 205427124U discloses a device for measuring the return voltage. This device realizes the control of the polarization and depolarization time and the measurement of the return voltage through a CPU. However, this device can only measure the return voltage and cannot measure the polarization / depolarization current at the same time. Summary of the Invention

[0005] An embodiment of the present invention provides a method for detecting the insulation state of a cable, which can realize the simultaneous or sequential measurement of the polarization current, depolarization current, and voltage of the cable to be measured, and improve the accuracy and convenience of analyzing the insulation state of the cable to be measured.

[0006] An embodiment of the present invention provides a method for detecting the insulation state of a cable, which is applied to the host computer of a cable measuring device. The cable measuring device includes: a host computer, a power supply, a first relay, a second relay, a third relay, a first current measurement module, a voltage measurement module, and a cable wiring module; wherein, the first relay includes a first normally open contact, a first normally closed contact, and a first fixed contact; the second relay includes a second normally open contact, a second normally closed contact, and a second fixed contact; the third relay includes a third normally open contact, a third normally closed contact, and a third fixed contact; the power supply is connected to the first normally open contact, the first fixed contact is connected to the second fixed contact, the first normally closed contact is grounded, the second normally closed contact is connected to the third normally closed contact, the second normally open contact is connected to the third normally closed contact through the first current measurement module, the third normally open contact is connected to the voltage measurement module, and the third fixed contact is connected to the cable wiring module; the host computer establishes communication connections with the first relay, the second relay, the third relay, the first current measurement module, and the voltage measurement module;

[0007] The method for detecting the insulation state of the cable includes:

[0008] After the cable to be measured is connected to the cable wiring module, control the first relay and the second relay to remain in the normally open state, and the third relay to remain in the normally closed state, so that the cable to be measured is in a charging state, and obtain the first polarization current of the cable to be measured through the first current measurement module;

[0009] After obtaining the first polarization current, adjust the first relay to the normally closed state, so that the cable to be measured is in a discharging state, and obtain the first depolarization current of the cable to be measured through the first current measurement module;

[0010] After obtaining the first depolarization current, adjust the third relay to the normally open state, and obtain the first voltage of the cable to be measured through the voltage measurement module;

[0011] Determine the insulation state of the cable to be measured according to the first polarization current, the first depolarization current, and the first voltage of the cable to be measured.

[0012] Further, the cable measuring device further includes: a fourth relay;

[0013] The fourth relay includes: a fourth normally open contact, a fourth normally closed contact, and a fourth fixed contact;

[0014] The fourth fixed contact is connected to the cable wiring module, the fourth normally open contact is connected to the power supply, and the fourth normally closed contact is grounded.

[0015] Further, the cable wiring module includes: a grounding end, a first measurement end, a second measurement end, and a third measurement end;

[0016] The third measurement terminal is connected to the third fixed contact, the second measurement terminal is connected to the fourth fixed contact, and the first measurement terminal is connected to the fourth fixed contact;

[0017] Before the cable to be measured is connected to the cable connection module, it further includes:

[0018] Short-circuit the grounding terminal, the first measurement terminal, the second measurement terminal, and the third measurement terminal to release the residual charge of the grounding terminal, the first measurement terminal, the second measurement terminal, and the third measurement terminal.

[0019] Further, the cable measurement device further includes: a first non-inductive protection resistor and a second non-inductive protection resistor;

[0020] The first end of the first non-inductive protection resistor is connected to the second normally closed contact, and the second end of the first non-inductive protection resistor is connected to the second end of the first current measurement module;

[0021] The first end of the second non-inductive protection resistor is connected to the second normally open contact, and the second end of the second non-inductive protection resistor is connected to the first end of the first current measurement module.

[0022] Further, the cable measurement device further includes: a second current measurement module;

[0023] The first end of the second current measurement module is connected to the second end of the first current measurement module, and the second end of the second current measurement module is connected to the third normally closed contact;

[0024] Controlling the first relay and the second relay to remain in the normally open state and the third relay to remain in the normally closed state, so that the cable to be measured is in the charging state, and obtaining the first polarization current of the cable to be measured through the first current measurement module, includes:

[0025] Controlling the first relay to remain in the normally open state, and the second relay and the third relay to remain in the normally closed state, and obtaining the second polarization current through the second current measurement module;

[0026] If the second polarization current is less than the protection threshold current, send a normally open control signal to the first relay and the second relay, and send a normally closed control signal to the third relay, so that the first relay and the second relay are adjusted to the normally open state according to the normally open control signal, so that the third relay is adjusted to the normally closed state according to the normally closed control signal, so that the cable to be measured is in the charging state, and obtaining the first polarization current of the cable to be measured through the first current measurement module;

[0027] If the second polarization current is not less than the protection threshold current, generate a first warning message according to the second polarization current.

[0028] Further, after obtaining the first polarization current, adjusting the first relay to a normally closed state to put the cable to be measured in a discharging state, and obtaining the first depolarization current of the cable to be measured through the first current measurement module, includes:

[0029] After obtaining the first polarization current, controlling the first relay and the second relay to remain in the normally closed state, and obtaining the second depolarization current through the second current measurement module;

[0030] If the second depolarization current is less than the protection threshold current, sending a normally open control signal to the second relay and a normally closed control signal to the first relay, so that the first relay is adjusted to the normally closed state according to the normally closed control signal, and the second relay is adjusted to the normally open state according to the normally open control signal, to put the cable to be measured in a discharging state, and obtaining the first depolarization current of the cable to be measured through the first current measurement module;

[0031] If the second depolarization current is not less than the protection threshold current, generating a second warning message according to the second depolarization current.

[0032] Further, the cable measurement device further includes: a fifth relay;

[0033] The fifth relay includes: a fifth normally open contact, a fifth normally closed contact, a fifth fixed contact, a sixth normally open contact, a sixth normally closed contact, and a sixth fixed contact;

[0034] The fifth fixed contact is connected to the second measurement terminal, the fifth normally closed contact is connected to the fourth fixed contact, the fifth normally open contact is connected to the third normally open contact, the fifth normally open contact is connected to the voltage measurement module, the sixth fixed contact is connected to the first measurement terminal, the sixth normally closed contact is connected to the fourth fixed contact, and the sixth normally open contact is connected to the voltage measurement module.

[0035] Further, it further includes:

[0036] After the cable to be measured is connected to the cable connection module, controlling the first relay and the fourth relay to remain in the normally open state, and the second relay, the third relay, and the fifth relay to remain in the normally closed state, to put the cable to be measured in a charging state, and obtaining the third polarization current through the second current measurement module;

[0037] If the third polarization current is less than the protection threshold current, sending a normally open control signal to the second relay, so that the second relay is adjusted to the normally open state according to the normally open control signal, and obtaining the fourth polarization current of the cable to be measured through the first current measurement module;

[0038] After obtaining the fourth polarization current, a normally closed control signal is sent to the first relay and the fourth relay, so that the first relay and the fourth relay are adjusted to the normally closed state according to the normally closed control signal, the cable to be measured is in a discharge state, and the third depolarization current corresponding to the third measurement end of the cable to be measured is obtained through the first current measurement module;

[0039] Meanwhile, a normally open control signal is sent to the fourth relay and the fifth relay, so that the fourth relay and the fifth relay are adjusted to the normally open state according to the normally open control signal, and the second voltage corresponding to the first measurement end and the second measurement end of the cable to be measured is obtained through the voltage measurement module;

[0040] Determine the insulation state of the cable to be measured according to the fourth polarization current, the third depolarization current and the second voltage of the cable to be measured;

[0041] If the third polarization current is not less than the protection threshold current, a third warning message is generated according to the third polarization current.

[0042] Further, the determining the insulation state of the cable to be measured according to the first polarization current, the first depolarization current and the first voltage of the cable to be measured includes:

[0043] Determine the insulation resistance and low-frequency dielectric loss parameters of the cable to be measured according to the first polarization current of the cable to be measured;

[0044] Determine the aging factor, charge and trap parameters of the cable to be measured according to the first depolarization current of the cable to be measured;

[0045] Determine the voltage peak value, peak time and voltage waveform during the measurement period of the cable to be measured according to the first voltage of the cable to be measured;

[0046] Determine the insulation state of the cable to be measured according to the insulation resistance, low-frequency dielectric loss parameters, aging factor, charge, trap parameters, voltage peak value, peak time and voltage waveform during the measurement period of the cable to be measured.

[0047] Further, the power supply is a high-voltage DC power supply.

[0048] By implementing the present invention, the following beneficial effects are achieved:

[0049] The present invention provides a method for detecting the insulation state of a cable. This method is applied to a cable measuring device, which includes: a power supply, a first relay, a second relay, a third relay, a first current measuring module, a voltage measuring module, and a cable connection module. After connecting the cable to be measured to the cable connection module, the first relay and the second relay are controlled to remain normally open, and the third relay is controlled to remain normally closed, so that the cable to be measured is in a charging state. The first polarization current of the cable to be measured is obtained through the first current measuring module. After obtaining the first polarization current, the first relay is adjusted to the normally closed state, so that the cable to be measured is in a discharging state. The first depolarization current of the cable to be measured is obtained through the first current measuring module. After obtaining the first depolarization current, the third relay is adjusted to the normally open state, and the first voltage of the cable to be measured is obtained through the voltage measuring module. By adjusting the relays on the cable measuring device, the wiring mode can be flexibly adjusted, so that the cable to be measured is in polarization and depolarization states, realizing the measurement of the polarization current and depolarization current of the cable to be measured, and making up for the defect that the prior art can only measure voltage but not polarization current and depolarization current. Furthermore, the insulation state of the cable to be measured is determined according to the first polarization current, the first depolarization current, and the first voltage of the cable to be measured, simplifying the operation of analyzing the insulation state of the cable to be measured, and improving the accuracy and convenience of analyzing the insulation state of the cable to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 FIG. is a schematic flowchart of a method for detecting the insulation state of a cable according to an embodiment of the present invention.

[0051] Figure 2 FIG. is a schematic structural diagram of a cable measuring device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0055] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0056] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0057] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0058] In the description of the embodiments of this application, the term "a plurality" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0059] In the description of the embodiments of this application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0060] As Figure 1 shown, it is a method for detecting the insulation state of a cable provided by an embodiment of the present invention, which is applied to as Figure 2The host computer of the cable measuring device shown.

[0061] In a preferred embodiment, the power supply is a high-voltage DC power supply.

[0062] As Figure 2 As shown, the cable measuring device includes: a host computer 21, a power supply 1, a first relay 2, a second relay 3, a third relay 5, a first current measurement module 9, a voltage measurement module 15, and a cable wiring module 14. Among them, the power supply 1 is a high-voltage DC power supply for outputting high voltage. For the voltage level of the cable to be measured, the polarization voltage is generally selected as the cable insulation thickness d (mm) × 400 (V / mm). The first relay 2, the second relay 3, and the third relay 5 are all single-pole double-throw high-voltage relays. The first current measurement module 9 is a weak current measurement module.

[0063] The first relay 2 includes a first normally open contact NO1, a first normally closed contact NC1, and a first fixed contact; the second relay 3 includes a second normally open contact NO2, a second normally closed contact NC2, and a second fixed contact; the third relay 5 includes a third normally open contact NO3, a third normally closed contact NC3, and a third fixed contact; one end of the power supply 1 is connected to the first normally open contact NO1, the first fixed contact is connected to the second fixed contact, the first normally closed contact NC1 is grounded, the other end of the power supply 1 is grounded, the second normally closed contact NC2 is connected to the third normally closed contact NC3, the second normally open contact NO2 is connected to the third normally closed contact NC3 through the first current measurement module 9, the third normally open contact NO3 is connected to the voltage measurement module 15, and the third fixed contact is connected to the cable wiring module 14; the host computer 21 establishes communication connections with the first relay 2, the second relay 3, the third relay 5, the first current measurement module 9, and the voltage measurement module 15.

[0064] In a preferred embodiment, the cable measuring device further includes: a fourth relay 4; the fourth relay 4 includes: a fourth normally open contact NO4, a fourth normally closed contact NC4, and a fourth fixed contact; the fourth fixed contact is connected to the cable wiring module 14, the fourth normally open contact NO4 is connected to the power supply 1, and the fourth normally closed contact NC4 is grounded.

[0065] In a preferred embodiment, the cable wiring module 14 includes: a grounding end, a first measurement end 11, a second measurement end 12, and a third measurement end 13; the third measurement end 13 is connected to the third fixed contact, the second measurement end 12 is connected to the fourth fixed contact, and the first measurement end 11 is connected to the fourth fixed contact; before the cable to be measured is connected to the cable wiring module, it further includes: short-circuiting the grounding end, the first measurement end 11, the second measurement end 12, and the third measurement end 13 so that the first measurement end 11, the second measurement end 12, and the third measurement end 13 release residual charges through the grounding end.

[0066] In a preferred embodiment, the cable measuring device further includes a first non-inductive protection resistor 7 and a second non-inductive protection resistor 8. The first end of the first non-inductive protection resistor 7 is connected to the second normally closed contact NC2, and the second end of the first non-inductive protection resistor 7 is connected to the second end of the first current measuring module 9. The first end of the second non-inductive protection resistor 8 is connected to the second normally open contact NO2, and the second end of the second non-inductive protection resistor 8 is connected to the first end of the first current measuring module 9.

[0067] In a preferred embodiment, the cable measuring device further includes a fifth relay 6, and the fifth relay 6 is a double-pole double-throw high-voltage relay. The fifth relay 6 includes a fifth normally open contact NO5, a fifth normally closed contact NC5, a fifth fixed contact, a sixth normally open contact NO6, a sixth normally closed contact NC6, and a sixth fixed contact. The fifth fixed contact is connected to the second measuring end 12, the fifth normally closed contact NC5 is connected to the fourth fixed contact, the fifth normally open contact NO5 is connected to the third normally open contact NO3, the fifth normally open contact NO5 is connected to the voltage measuring module 15, the sixth fixed contact is connected to the first measuring end 11, the sixth normally closed contact NC6 is connected to the fourth fixed contact, and the sixth normally open contact NO6 is connected to the voltage measuring module 15.

[0068] Preferably, the cable measuring device further includes a first wireless module 16, a second wireless module 17, a third wireless module 18, a control unit 19, and a lithium battery 20. The control unit 19 establishes a communication connection with the upper computer 21 through the third wireless module 18 and the first wireless module 16. The control unit 19 is configured to receive instructions issued by the upper computer 21, and after obtaining the polarization / depolarization current data acquired by the first current measuring module 9, transmit the data to the upper computer 21 through the first wireless module 16 and the third wireless module 18. The control unit 19 is further configured to receive control instructions issued by the upper computer 21 and control the first relay 2, the second relay 3, the third relay 5, the fourth relay 4, and the fifth relay 6. The lithium battery 20 can provide a 24V voltage to supply power to the first current measuring module 9 and the control unit 19, which can avoid interference from the ground wire and improve the accuracy and anti-interference ability of weak current measurement.

[0069] As Figure 1 shown, the cable insulation state detection method includes:

[0070] Step S1: After the cable to be measured is connected to the cable connection module, control the first relay and the second relay to remain in the normally open state, and the third relay to remain in the normally closed state, so that the cable to be measured is in a charging state, and obtain the first polarization current of the cable to be measured through the first current measuring module;

[0071] Step S2: After obtaining the first polarization current, adjust the first relay to the normally closed state to put the cable to be measured in a discharging state, and obtain the first depolarization current of the cable to be measured through the first current measurement module;

[0072] Step S3: After obtaining the first depolarization current, adjust the third relay to the normally open state, and obtain the first voltage of the cable to be measured through the voltage measurement module;

[0073] Step S4: Determine the insulation state of the cable to be measured according to the first polarization current, the first depolarization current, and the first voltage of the cable to be measured.

[0074] For Step S1, before connecting the cable to be measured to the cable connection module, short-circuit the grounding terminal, the first measurement terminal 11, the second measurement terminal 12, and the third measurement terminal 13 of the cable connection module. After releasing the residual charge on the cable after a short time, connect the three phases of the cable to be measured to the first measurement terminal 11, the second measurement terminal 12, and the third measurement terminal 13 of the cable connection module 14 respectively. Through this connection method, the polarization and depolarization currents and voltages of the three-phase cable can be measured. After connecting the cable to be measured to the cable connection module 14, control the first relay 2 and the second relay 3 to remain in the normally open state, and the third relay 5 to remain in the normally closed state, so that the cable to be measured is in a charging state at this time, and obtain the first polarization current of the cable to be measured through the first current measurement module 9.

[0075] In a preferred embodiment, the cable measurement device further includes: a second current measurement module 10; the first end of the second current measurement module 10 is connected to the second end of the first current measurement module 9, and the second end of the second current measurement module 10 is connected to the third normally closed contact NC3;

[0076] Controlling the first relay 2 and the second relay 3 to remain in the normally open state and the third relay 5 to remain in the normally closed state to put the cable to be measured in a charging state and obtaining the first polarization current of the cable to be measured through the first current measurement module 9 includes: controlling the first relay 2 to remain in the normally open state, the second relay 3 and the third relay 5 to remain in the normally closed state, and obtaining the second polarization current through the second current measurement module 10; if the second polarization current is less than the protection threshold current, send a normally open control signal to the first relay 2 and the second relay 3, and send a normally closed control signal to the third relay 5, so that the first relay 2 and the second relay 3 are adjusted to the normally open state according to the normally open control signal, so that the third relay 5 is adjusted to the normally closed state according to the normally closed control signal, to put the cable to be measured in a charging state, and obtain the first polarization current of the cable to be measured through the first current measurement module 9; if the second polarization current is not less than the protection threshold current, generate a first warning message according to the second polarization current.

[0077] Specifically, control the first relay 2 to remain normally open, and the second relay 3 and the third relay 5 to remain normally closed. At this time, the high-voltage direct current output by the power supply 1 flows through the first normally open contact NO1 and into the first relay 2, the second relay 3, the first non-inductive protection resistor 7, the second current measurement module 10, the third relay 5, and the third measurement terminal 13 in sequence. At this time, the current flowing through can be obtained through the second current measurement module 10 (i.e., the above-mentioned second polarization current). If the second polarization current is less than the protection threshold current, it proves that the current at this time will not damage the first current measurement module 9. At this time, send a normally open control signal to the first relay 2 and the second relay 3, and send a normally closed control signal to the third relay 5, so that the first relay 2 and the second relay 3 are adjusted to the normally open state according to the normally open control signal, so that the third relay 5 is adjusted to the normally closed state according to the normally closed control signal, and the cable to be measured is in the charging state. At this time, the high-voltage direct current output by the power supply 1 flows through the first normally open contact NO1 and into the first relay 2, the second relay 3, the second non-inductive protection resistor 8, the first current measurement module 9, the second current measurement module 10, the third relay 5, and the third measurement terminal 13 in sequence. At this time, the first polarization current is obtained through the first current measurement module 9. If the second polarization current is not less than the protection threshold current, generate a first warning message according to the second polarization current. By setting the second current measurement module 10 to pre-detect the polarization current in the circuit before the first current measurement module 9 measures the polarization current, it can protect the first current measurement module 9 from equipment failures caused by excessive current and other problems, and improve the durability of the first current measurement module 9.

[0078] For step S2: In a preferred embodiment, after obtaining the first polarization current, adjusting the first relay 2 to the normally closed state to make the cable to be measured in the discharge state, and obtaining the first depolarization current of the cable to be measured through the first current measurement module 9 includes: after obtaining the first polarization current, controlling the first relay 2 and the second relay 3 to remain normally closed, and obtaining the second depolarization current through the second current measurement module 10; if the second depolarization current is less than the protection threshold current, send a normally open control signal to the second relay 3 and a normally closed control signal to the first relay 2, so that the first relay 2 is adjusted to the normally closed state according to the normally closed control signal, so that the second relay 3 is adjusted to the normally open state according to the normally open control signal, and the cable to be measured is in the discharge state, and the first depolarization current of the cable to be measured is obtained through the first current measurement module 9; if the second depolarization current is not less than the protection threshold current, generate a second warning message according to the second depolarization current.

[0079] Specifically, after obtaining the first polarization current, control the first relay 2 and the second relay 3 to remain normally closed. At this time, the power supply 1 no longer outputs high-voltage direct current outward. The residual current in the circuit (i.e., the above-mentioned second depolarization current) can be obtained through the second current measurement module 10. If the second depolarization current is less than the protection threshold current, it proves that the current at this time will not damage the first current measurement module 9. At this time, send a normally open control signal to the second relay 3 and a normally closed control signal to the first relay 2, so that the first relay 2 is adjusted to the normally closed state according to the normally closed control signal, and the second relay 3 is adjusted to the normally open state according to the normally open control signal, so that the cable to be measured is in a discharge state, and the first depolarization current of the cable to be measured is obtained through the first current measurement module 9. At this time, the first depolarization current is obtained through the first current measurement module 9. If the second depolarization current is not less than the protection threshold current, generate a second warning message according to the second depolarization current. By setting the second current measurement module 10 to pre-detect the depolarization current in the circuit before the first current measurement module 9 measures the depolarization current, it can protect the first current measurement module 9 from equipment failures caused by excessive current and other problems, and improve the durability of the first current measurement module 9.

[0080] By performing step S1 and step S2, the measurement of the polarization current and the depolarization current of the cable to be measured can be realized respectively. Further, it is also necessary to measure the voltage of the cable to be measured to comprehensively analyze the insulation state of the cable to be measured.

[0081] For step S3, after obtaining the first depolarization current, adjust the third relay 5 to the normally open state, and obtain the first voltage of the cable to be measured through the voltage measurement module 15. Specifically, after adjusting the third relay 5 to the normally open state, a loop is formed between the cable connection module 14, the third relay 5 and the voltage measurement module 15 at this time. The first voltage of the cable to be measured can be obtained by measuring the voltage in this loop through the voltage measurement module 15.

[0082] Preferably, by sequentially performing the above steps S1-S3, the measurement of the first polarization current, the first depolarization current and the first voltage of the cable to be measured can be realized. It is possible to measure only any one or a combination of the polarization current, the depolarization current and the voltage according to the actual scenario application requirements.

[0083] For step S4, determine the insulation state of the cable to be measured according to the first polarization current, the first depolarization current and the first voltage of the cable to be measured.

[0084] In a preferred embodiment, determining the insulation state of the cable to be measured based on the first polarization current, the first depolarization current, and the first voltage of the cable to be measured includes: determining the insulation resistance and low-frequency dielectric loss parameters of the cable to be measured according to the first polarization current of the cable to be measured; determining the aging factor, charge, and trap parameters of the cable to be measured according to the first depolarization current of the cable to be measured; determining the voltage peak value, peak time, and voltage waveform within the measurement time period of the cable to be measured according to the first voltage of the cable to be measured; and determining the insulation state of the cable to be measured according to the insulation resistance, low-frequency dielectric loss parameters, aging factor, charge, trap parameters, voltage peak value, peak time, and voltage waveform within the measurement time period of the cable to be measured.

[0085] In a preferred embodiment, it further includes: after the cable to be measured is connected to the cable connection module, controlling the first relay 2 and the fourth relay 4 to remain normally open, and the second relay 3, the third relay 5, and the fifth relay 6 to remain normally closed, so that the cable to be measured is in a charging state, and obtaining the third polarization current through the second current measurement module 10; if the third polarization current is less than the protection threshold current, sending a normally open control signal to the second relay 3, so that the second relay 3 is adjusted to the normally open state according to the normally open control signal, and obtaining the fourth polarization current of the cable to be measured through the first current measurement module 9; after obtaining the fourth polarization current, sending a normally closed control signal to the first relay 2 and the fourth relay 4, so that the first relay 2 and the fourth relay 4 are adjusted to the normally closed state according to the normally closed control signal, making the cable to be measured in a discharging state, and obtaining the third depolarization current corresponding to the third measurement terminal 13 of the cable to be measured through the first current measurement module 9; at the same time, sending a normally open control signal to the fourth relay 4 and the fifth relay 6, so that the fourth relay 4 and the fifth relay 6 are adjusted to the normally open state according to the normally open control signal, and obtaining the second voltage corresponding to the first measurement terminal 11 and the second measurement terminal 12 of the cable to be measured through the voltage measurement module 15; determining the insulation state of the cable to be measured according to the fourth polarization current, the third depolarization current, and the second voltage of the cable to be measured; if the third polarization current is not less than the protection threshold current, generating a third warning message according to the third polarization current.

[0086] Preferably, after the polarization current, depolarization current, and voltage of each phase of the cable to be measured are measured, the third measurement terminal 13 and the grounding terminal of the cable connection module 14 need to be connected by a wire, and the fourth relay 4 and the fifth relay 6 are adjusted to the normally closed state, and the residual charge is released for a short time before the next measurement can be started to avoid the influence of the residual charge on the measurement accuracy.

[0087] In summary, through the cable measurement device and the corresponding cable insulation state detection method provided by the present invention, the overall cable insulation state detection can be realized according to actual needs by flexibly adjusting the wiring method and the combination between various measurement methods.

[0088] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present invention, the connection relationships between the modules indicate that there is a communication connection between them, which can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0089] Those skilled in the art can clearly understand that for the sake of convenience and brevity, the specific working process of the device described above can refer to the corresponding process in the foregoing method embodiment, and will not be elaborated here.

[0090] The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A method for detecting the insulation status of a cable, characterized in that: A host computer applied to a cable measuring device, the cable measuring device comprising: a host computer, a power supply, a first relay, a second relay, a third relay, a first current measuring module, a voltage measuring module and a cable wiring module; wherein the first relay comprises a first normally open contact, a first normally closed contact and a first fixed contact; the second relay comprises a second normally open contact, a second normally closed contact and a second fixed contact; the third relay comprises a third normally open contact, a third normally closed contact and a third fixed contact; the power supply is connected to the first normally open contact, the first fixed contact is connected to the second fixed contact, the first normally closed contact is grounded, the second normally closed contact is connected to the third normally closed contact, the second normally open contact is connected to the third normally closed contact through the first current measuring module, the third normally open contact is connected to the voltage measuring module, and the third fixed contact is connected to the cable wiring module; the host computer establishes a communication connection with the first relay, the second relay, the third relay, the first current measuring module and the voltage measuring module; The cable insulation state detection method comprises: After the cable to be measured is connected to the cable wiring module, the first relay and the second relay are controlled to remain in a normally open state, and the third relay is controlled to remain in a normally closed state, so that the cable to be measured is in a charging state, and a first polarization current of the cable to be measured is obtained through the first current measurement module; After obtaining the first polarization current, adjusting the first relay to a normally closed state, so that the cable to be measured is in a discharge state, and obtaining the first depolarization current of the cable to be measured through the first current measurement module; After obtaining the first depolarization current, adjusting the third relay to a normally open state, and obtaining the first voltage of the cable to be measured through the voltage measurement module; The insulation state of the cable to be measured is determined according to the first polarization current, the first depolarization current and the first voltage of the cable to be measured.

2. A cable insulation status detection method as claimed in claim 1, characterized in that: The cable measuring device further includes: a fourth relay; The fourth relay comprises: a fourth normally open contact, a fourth normally closed contact and a fourth fixed contact; The fourth fixed contact is connected to the cable connection module, the fourth normally open contact is connected to the power supply, and the fourth normally closed contact is grounded.

3. A cable insulation status detection method as claimed in claim 2, characterized in that: The cable connection module comprises: a ground terminal, a first measuring terminal, a second measuring terminal and a third measuring terminal; The third measuring end is connected to the third fixed contact, the second measuring end is connected to the fourth fixed contact, and the first measuring end is connected to the fourth fixed contact; Before the cable to be measured is connected to the cable connection module, it also includes: The ground terminal, the first measuring terminal, the second measuring terminal and the third measuring terminal are short-circuited, so that the first measuring terminal, the second measuring terminal and the third measuring terminal release residual charges through the ground terminal.

4. A cable insulation status detection method as claimed in claim 3, characterized in that: The cable measuring device further comprises: a first non-inductive protection resistor and a second non-inductive protection resistor; The first end of the first non-inductive protection resistor is connected to the second normally closed contact, and the second end of the first non-inductive protection resistor is connected to the second end of the first current measurement module; The first end of the second non-inductive protection resistor is connected to the second normally open contact, and the second end of the second non-inductive protection resistor is connected to the first end of the first current measurement module.

5. A cable insulation status detection method as claimed in claim 4, characterized in that: The cable measuring device further includes: a second current measuring module; The first end of the second current measuring module is connected to the second end of the first current measuring module, and the second end of the second current measuring module is connected to the third normally closed contact; Controlling the first relay and the second relay to remain in a normally open state and the third relay to remain in a normally closed state, so that the cable to be measured is in a charging state, and obtaining a first polarization current of the cable to be measured through a first current measurement module, including: Control the first relay to remain in a normally open state, the second relay and the third relay to remain in a normally closed state, and obtain a second polarization current through a second current measurement module; If the second polarization current is less than the protection threshold current, a normally open control signal is sent to the first relay and the second relay, and a normally closed control signal is sent to the third relay, so that the first relay and the second relay are adjusted to a normally open state according to the normally open control signal, and the third relay is adjusted to a normally closed state according to the normally closed control signal, so that the cable to be measured is in a charging state, and the first polarization current of the cable to be measured is obtained through the first current measurement module; If the second polarization current is not less than the protection threshold current, first warning information is generated according to the second polarization current.

6. A cable insulation status detection method as claimed in claim 5, characterized in that: After obtaining the first polarization current, adjusting the first relay to a normally closed state so that the cable to be measured is in a discharge state, and obtaining the first depolarization current of the cable to be measured through the first current measurement module, comprises: After obtaining the first polarization current, controlling the first relay and the second relay to maintain a normally closed state, and obtaining the second depolarization current through the second current measurement module; If the second depolarization current is less than the protection threshold current, a normally open control signal is sent to the second relay, and a normally closed control signal is sent to the first relay, so that the first relay is adjusted to a normally closed state according to the normally closed control signal, so that the second relay is adjusted to a normally open state according to the normally open control signal, so that the cable to be measured is in a discharge state, and the first depolarization current of the cable to be measured is obtained through the first current measurement module; If the second depolarization current is not less than the protection threshold current, second warning information is generated according to the second depolarization current.

7. A cable insulation status detection method as claimed in claim 6, characterized in that: The cable measuring device further includes: a fifth relay; The fifth relay comprises: a fifth normally open contact, a fifth normally closed contact, a fifth fixed contact, a sixth normally open contact, a sixth normally closed contact and a sixth fixed contact; The fifth fixed contact is connected to the second measuring end, the fifth normally closed contact is connected to the fourth fixed contact, the fifth normally open contact is connected to the third normally open contact, the fifth normally open contact is connected to the voltage measuring module, the sixth fixed contact is connected to the first measuring end, the sixth normally closed contact is connected to the fourth fixed contact, and the sixth normally open contact is connected to the voltage measuring module.

8. A cable insulation status detection method as claimed in claim 7, characterized in that: Also includes: After the cable to be measured is connected to the cable wiring module, the first relay and the fourth relay are controlled to remain in a normally open state, and the second relay, the third relay and the fifth relay are controlled to remain in a normally closed state, so that the cable to be measured is in a charging state, and the third polarization current is obtained through the second current measurement module; If the third polarization current is less than the protection threshold current, a normally open control signal is sent to the second relay, so that the second relay is adjusted to a normally open state according to the normally open control signal, and a fourth polarization current of the cable to be measured is obtained through the first current measurement module; After obtaining the fourth polarization current, sending a normally closed control signal to the first relay and the fourth relay, so that the first relay and the fourth relay are adjusted to a normally closed state according to the normally closed control signal, so that the cable to be measured is in a discharge state, and obtaining a third depolarization current corresponding to the cable to be measured at the third measuring end through the first current measurement module; At the same time, a normally open control signal is sent to the fourth relay and the fifth relay, so that the fourth relay and the fifth relay are adjusted to a normally open state according to the normally open control signal, and a second voltage corresponding to the first measuring end and the second measuring end of the measured cable is obtained through the voltage measurement module; determining the insulation state of the cable to be measured according to the fourth polarization current, the third depolarization current and the second voltage of the cable to be measured; If the third polarization current is not less than the protection threshold current, third warning information is generated according to the third polarization current.

9. A cable insulation status detection method as claimed in claim 8, characterized in that: The step of determining the insulation state of the cable to be measured according to the first polarization current, the first depolarization current and the first voltage of the cable to be measured comprises: Determining the insulation resistance and low-frequency dielectric loss parameter of the cable to be measured according to the first polarization current of the cable to be measured; determining an aging factor, a charge and a trap parameter of the cable to be measured according to a first depolarization current of the cable to be measured; Determine the voltage peak value, peak time and voltage waveform of the cable to be measured within a measurement period according to the first voltage of the cable to be measured; The insulation state of the cable to be measured is determined based on the insulation resistance, low-frequency dielectric loss parameter, aging factor, charge, trap parameter, voltage peak value, peak time and voltage waveform within the measurement time period.

10. A cable insulation status detection method as claimed in claim 9, characterized in that: The power supply is a high voltage direct current power supply.

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