Method for monitoring insulation resistance of cross-core screw

Abstract

The invention provides a cross-core screw insulation resistance monitoring method, and relates to the technical field of generator monitoring, an insulation resistance monitoring circuit comprises cross-core screws of a generator, isolation resistors and a ping-pong switching circuit, the cross-core screws and the isolation resistors are alternately connected in series to form a series circuit, and the ping-pong switching circuit is connected with the cross-core screws. The method comprises the following steps: applying direct-current excitation voltage to a series circuit, determining a first insulation resistance value, and judging whether a one-point grounding fault of the cross-core screw exists or not according to the first insulation resistance value; when the one-point grounding fault of the cross-core screw exists, determining a first grounding point in the cross-core screw; under the condition that the one-point grounding fault of the cross-core screw exists, the resistance value of a second insulation resistor is determined, and whether the two-point grounding fault of the cross-core screw exists or not is judged according to the resistance value of the second insulation resistor; and when a two-point grounding fault of the cross-core screw exists, determining two grounding points in the cross-core screw, so that the insulation resistance of the stator cross-core screw can be monitored, and the grounding condition of the stator cross-core screw can be found in time.

Description

Technical Field

[0001] The present invention relates to the technical field of generator monitoring, and more particularly, to a method for monitoring the insulation resistance of a through-bolt. Background Art

[0002] The stator through-bolt is a key fastening component of the generator stator core. It passes through the stator core laminations and is isolated from the core by insulating materials to ensure the tight fixation of the core laminations and the stability of electromagnetic performance. However, under the action of long-term high-load operation, mechanical vibration or environmental humidity, the insulation layer of the through-bolt is prone to deterioration, resulting in a decrease in its insulation resistance to ground and a grounding fault.

[0003] The existing monitoring technologies for stator through-bolts are difficult to effectively monitor the insulation resistance of stator through-bolts, and thus it is difficult to accurately know the degree of decline in the insulation ability of stator through-bolts. As a result, it is difficult to predict and prevent possible faults, and it is difficult to determine the location of the grounding point, which will increase the difficulty of fault repair. Summary of the Invention

[0004] The problem solved by the present invention is how to monitor the insulation performance of the stator through-bolt and reduce the difficulty of fault repair.

[0005] To solve the above problems, the present invention provides a method for monitoring the insulation resistance of a through-bolt, based on an insulation resistance monitoring circuit. The insulation resistance monitoring circuit includes each through-bolt of the generator, an isolation resistor, and a ping-pong switching circuit. Each of the through-bolts is alternately connected in series with the isolation resistor to form a series circuit, and the series circuit is connected to the ping-pong switching circuit. The method for monitoring the insulation resistance of the through-bolt includes:

[0006] Applying a DC excitation voltage to the series circuit, equivalenting the insulation resistance monitoring circuit to a first equivalent circuit assuming a single-point grounding fault occurs in the through-bolt, determining the first circuit parameters of the first equivalent circuit when the corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, determining the first insulation resistance value according to the DC excitation voltage and the first circuit parameters, and judging whether there is a single-point grounding fault in the through-bolt according to the first insulation resistance value;

[0007] Determining the first grounding point in the through-bolt when there is a single-point grounding fault in the through-bolt;

[0008] In the case of a single-point grounding fault of the through bolt, the insulation resistance monitoring circuit is equivalent to a second equivalent circuit assuming a two-point grounding fault of the through bolt. When determining that the corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, the second circuit parameters of the second equivalent circuit are determined. The second insulation resistance value is determined according to the DC excitation voltage and the second circuit parameters, and whether there is a two-point grounding fault of the through bolt is judged according to the second insulation resistance value;

[0009] When there is a two-point grounding fault of the through bolt, two grounding points in the through bolt are determined. Among them, one of the grounding points is the first grounding point in the case of a single-point grounding fault of the through bolt, and the other grounding point is the second grounding point in the case of a two-point grounding fault of the through bolt.

[0010] Optionally, the first equivalent circuit includes an equivalent excitation power supply corresponding to the DC excitation voltage, a first series equivalent circuit corresponding to the series circuit, a first insulation resistance, and a corresponding equivalent circuit of the ping-pong switching circuit. The first series equivalent circuit is connected in parallel with the equivalent excitation power supply. The first series equivalent circuit includes a first isolation resistance and a second isolation resistance connected in series. The first isolation resistance is the equivalent resistance of all isolation resistances between the first assumed grounding point in the through bolt assuming a single-point grounding fault and the positive pole of the equivalent excitation power supply. The second isolation resistance is the equivalent resistance of all isolation resistances between the first assumed grounding point and the negative pole of the equivalent excitation power supply. The first insulation resistance is the insulation resistance of the first assumed grounding point;

[0011] The corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit includes a first sampling resistance and a first switching resistance connected in series, and a first switching switch connected in parallel with the first switching resistance, a second sampling resistance and a second switching resistance connected in series, and a second switching switch connected in parallel with the second switching resistance. One end of the first switching resistance far from the first sampling resistance and one end of the second switching resistance far from the second sampling resistance are respectively connected to both ends of the first series equivalent circuit. One end of the first sampling resistance far from the first switching resistance and one end of the second sampling resistance far from the second switching resistance are connected to form a second connection point. The second connection point is connected to a first connection point between the first isolation resistance and the second isolation resistance through the first insulation resistance.

[0012] Optionally, when determining that the corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, the first circuit parameters of the first equivalent circuit, and determining the first insulation resistance value according to the DC excitation voltage and the first circuit parameters include:

[0013] Determine the first parameter of the first equivalent circuit in the first switch state and the second parameter of the first equivalent circuit in the second switch state;

[0014] Based on Kirchhoff's law, construct a first set of equations according to the first loop, the second loop, and the third loop;

[0015] Substitute the DC excitation voltage and the first parameter into the first set of equations to obtain a first parameter set of equations;

[0016] Substitute the DC excitation voltage and the second parameter into the first set of equations to obtain a second parameter set of equations;

[0017] Confirm the value of the first insulation resistance according to the first parameter set of equations and the second parameter set of equations;

[0018] Wherein, in the first equivalent circuit, the first sampling resistor, the first switching resistor, the first isolation resistor, and the first insulation resistor form the first loop, the second sampling resistor, the second switching resistor, the second isolation resistor, and the first insulation resistor form the second loop, the first switch state includes the first switching switch being disconnected and the second switching switch being closed, the second switch state includes the first switching switch being closed and the second switching switch being disconnected, and the first circuit parameters include the first parameter and the second parameter.

[0019] Optionally, the determining the first grounding point in the through-bolt when there is a single-point grounding fault of the through-bolt includes:

[0020] Determine the resistance values of the first isolation resistor and the second isolation resistor according to the value of the first insulation resistance;

[0021] Determine the position of the first assumed grounding point relative to the DC excitation voltage according to the relationship between the resistance value of the first isolation resistor and / or the resistance value of the second isolation resistor and the total resistance value of the isolation resistors, wherein the sum of the resistance value of the first isolation resistor and the resistance value of the second isolation resistor is equal to the total resistance value of the isolation resistors.

[0022] Optionally, the determining whether there is a single-point grounding fault of the through-bolt according to the value of the first insulation resistance includes:

[0023] When the value of the first insulation resistance is less than the first preset insulation resistance value, it is determined that there is a single-point grounding fault of the through-bolt;

[0024] When the value of the first insulation resistance is greater than or equal to the first preset insulation resistance value, it is determined that there is no single-point grounding fault of the through-bolt.

[0025] Optionally, the second equivalent circuit includes an equivalent excitation power supply corresponding to the DC excitation voltage, a second series equivalent circuit corresponding to the series circuit, a first insulation resistor, a second insulation resistor and a corresponding equivalent circuit of the ping-pong switching circuit, the second series equivalent circuit is connected in parallel with the equivalent excitation power supply, the second series equivalent circuit includes a third isolation resistor, a fourth isolation resistor and a fifth isolation resistor connected in series with each other, the third isolation resistor is the equivalent resistance of all isolation resistors between the first grounding point and one end of the equivalent excitation power supply, the fifth isolation resistor is the equivalent resistance of all isolation resistors between the second assumed grounding point in the through screw and the other end of the equivalent excitation power supply when a two-point grounding fault is assumed, the fourth isolation resistor is the equivalent resistance of all isolation resistors between the first grounding point and the second assumed grounding point, the first insulation resistor is the insulation resistance of the first grounding point, and the second insulation resistance is the insulation resistance of the second assumed grounding point;

[0026] The corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit includes a first sampling resistor and a first switching resistor connected in series, a first switching switch connected in parallel with the first switching resistor, a second sampling resistor and a second switching resistor connected in series, and a second switching switch connected in parallel with the second switching resistor. An end of the first switching resistor away from the first sampling resistor and an end of the second switching resistor away from the second sampling resistor are respectively connected to two ends of the second series equivalent circuit. An end of the first sampling resistor away from the first switching resistor and an end of the second sampling resistor away from the second switching resistor are connected to form a third connection point. A fourth connection point between the third isolation resistor and the fourth isolation resistor is connected to the third connection point via the first insulation resistor. A fifth connection point between the fourth isolation resistor and the fifth isolation resistor is connected to the third connection point via the second insulation resistor.

[0027] Optionally, determining a second circuit parameter of the second equivalent circuit when a corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in a different state, and determining a second insulation resistance value according to the DC excitation voltage and the second circuit parameter includes:

[0028] When the second assumed grounding point is located between the first grounding point and the positive electrode of the equivalent excitation power supply, determining a third parameter of the second equivalent circuit in the first switching state and a fourth parameter of the second equivalent circuit in the second switching state;

[0029] Based on Kirchhoff's law, the second set of equations is constructed according to the fourth loop, the fifth loop and the sixth loop;

[0030] Substitute the DC excitation voltage and the third parameter into the second set of equations to obtain a third set of parameter equations;

[0031] Substitute the DC excitation voltage and the fourth parameter into the second set of equations to obtain a fourth set of parameter equations;

[0032] Confirm the value of the second insulation resistance according to the third set of parameter equations and the fourth set of parameter equations;

[0033] Wherein, the fifth isolation resistance, the first sampling resistance, the first switching resistance, and the second insulation resistance form a fourth loop; the third isolation resistance, the second sampling resistance, the second switching resistance, and the first insulation resistance form a fifth loop, the first insulation resistance, the second insulation resistance, and the fourth isolation resistance form a sixth loop, the second circuit parameters include the third parameter and the fourth parameter, the first switch state includes the first switching switch being off and the second switching switch being on, and the second switch state includes the first switching switch being on and the second switching switch being off.

[0034] Optionally, when determining the second circuit parameters of the second equivalent circuit when the corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, determining the value of the second insulation resistance according to the DC excitation voltage and the second circuit parameters further includes:

[0035] When the second assumed grounding point is between the first grounding point and the negative pole of the equivalent excitation power supply, determine the fifth parameter of the second equivalent circuit in the first switch state and the sixth parameter of the second equivalent circuit in the second switch state;

[0036] Based on Kirchhoff's law, construct a third set of equations according to the seventh loop, the eighth loop, and the ninth loop;

[0037] Substitute the DC excitation voltage and the fifth parameter into the third set of equations to obtain a fifth set of parameter equations;

[0038] Substitute the DC excitation voltage and the sixth parameter into the third set of equations to obtain a sixth set of parameter equations;

[0039] Confirm the value of the second insulation resistance according to the fifth parameter equation set and the sixth parameter equation set. Among them, the third isolation resistance, the first sampling resistance, the first switching resistance and the first insulation resistance form a seventh loop; the fifth isolation resistance, the second sampling resistance, the second switching resistance and the second insulation resistance form an eighth loop, the first insulation resistance, the second insulation resistance and the fourth isolation resistance form a ninth loop, the second circuit parameter further includes the fifth parameter and the sixth parameter, the first switch state includes that the first switching switch is off and the second switching switch is on, and the second switch state includes that the first switching switch is on and the second switching switch is off.

[0040] Optionally, determining the two grounding points in the through bolt when there is a two-point grounding fault of the through bolt includes:

[0041] Determine the resistance values of the third isolation resistance, the fourth isolation resistance and the fifth isolation resistance according to the value of the second insulation resistance;

[0042] Determine the position of the second assumed grounding point relative to the DC excitation voltage according to the relationship between the sum of the resistance values of the third isolation resistance and the fourth isolation resistance and the total isolation resistance value, and / or according to the relationship between the resistance value of the fifth isolation resistance and the total isolation resistance value, where the sum of the resistance values of the third isolation resistance, the fourth isolation resistance and the fifth isolation resistance is equal to the total isolation resistance value.

[0043] Optionally, judging whether there is a two-point grounding fault of the through bolt according to the value of the second insulation resistance includes:

[0044] When the value of the second insulation resistance is less than the second preset insulation resistance value, it is determined that there is a two-point grounding fault of the through bolt;

[0045] When the value of the second insulation resistance is greater than or equal to the second preset insulation resistance value, it is determined that there is no two-point grounding fault of the through bolt and there is a one-point grounding fault of the through bolt.

[0046] The beneficial effects of the monitoring method for the insulation resistance of the through bolts in the present invention are as follows: All the through bolts in the stator are connected in series through the isolation resistance. By using the switch switching of the ping-pong circuit to change the connection mode of the circuit, the circuit parameters in the circuit will change under different switch states. By measuring the circuit parameters, the real-time monitoring and protection of the through bolts can be realized, and the resistance value of the insulation resistance of the through bolts can be further confirmed, so as to accurately know the degree of decline in the insulation ability of the stator through bolts, and the possible faults can be predicted and prevented. And when there is a single-point grounding fault, the grounding point of the through bolt with the grounding fault is determined. Through the accurate positioning of the fault point, the maintenance resources can be reasonably arranged, unnecessary component replacement or large-scale disassembly inspection can be avoided, and the maintenance cost can be reduced. When it is monitored that there is a single-point grounding fault in the through bolt, the circuit parameters in the second equivalent circuit assuming that the through bolt has a two-point grounding fault are further monitored to determine the second insulation resistance value of the through bolt and judge whether the through bolt has a two-point grounding. When the through bolt has a two-point grounding fault, the positions of the two grounding points of the through bolt are determined, which is convenient for the maintenance personnel to quickly and accurately find the fault position, shorten the troubleshooting time, improve the maintenance efficiency, and reduce the losses caused by equipment shutdown. And when there is a single-point grounding of the through bolt, a first-level alarm can be sent to the staff to ensure that the operation and maintenance personnel are notified of the fault in a short time; when there is a two-point grounding of the through bolt, a second-level alarm can be sent, and the circuit can be cut off within a preset time to avoid the expansion of the accident. By monitoring the insulation resistance value, the insulation state of the through bolts in the generator stator can be grasped in real time, and potential fault risks can be discovered in time, thereby improving the safety and reliability of the generator operation. By determining the grounding point of the through bolt, it helps to take targeted measures to repair the fault point in time, prevent the further expansion of the fault or the occurrence of secondary faults, and ensure the safe and stable operation of the generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic flow chart of the method for monitoring the insulation resistance of the through bolts in the embodiment of the present invention;

[0048] Figure 2 It is a schematic structural diagram of the circuit for monitoring the insulation resistance of the through bolts in the embodiment of the present invention;

[0049] Figure 3 It is the first equivalent circuit of the circuit for monitoring the insulation resistance of the through bolts in the embodiment of the present invention;

[0050] Figure 4 It is the equivalent circuit of the first equivalent circuit in the first switch state in the embodiment of the present invention;

[0051] Figure 5 It is the equivalent circuit of the first equivalent circuit in the second switch state in the embodiment of the present invention;

[0052] Figure 6 A second equivalent circuit of the through-screw insulation resistance monitoring circuit when the second grounding point is between the first grounding point and the positive electrode of the equivalent excitation power supply in an embodiment of the present invention;

[0053] Figure 7 for Figure 6 The equivalent circuit of the circuit in the first switching state;

[0054] Figure 8 for Figure 6 The equivalent circuit of the circuit in the second switching state;

[0055] Figure 9 The second equivalent circuit of the through screw insulation resistance monitoring circuit in the first switching state when the second grounding point is between the first grounding point and the negative pole of the equivalent excitation power supply in the embodiment of the present invention;

[0056] Figure 10 This is the second equivalent circuit of the through screw insulation resistance monitoring circuit in the second switching state when the second grounding point is between the first grounding point and the negative pole of the equivalent excitation power supply in the embodiment of the present invention. DETAILED DESCRIPTION

[0057] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0058] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0059] The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0060] In the related art, it is difficult to monitor the insulation performance of the stator through bolts, and thus it is difficult to accurately know the degree of decline in the insulation ability of the stator through bolts, making it difficult to predict and prevent possible faults, and it is also difficult to locate the grounding point, which will increase the difficulty of fault repair.

[0061] In view of the problems existing in the above related art, the present embodiment provides a method for monitoring the insulation resistance of a through bolt.

[0062] As Figure 1 shown, a method for monitoring the insulation resistance of a through bolt, based on an insulation resistance monitoring circuit, the insulation resistance monitoring circuit includes each through bolt of a generator, an isolation resistor, and a ping-pong switching circuit. Each of the through bolts is alternately connected in series with the isolation resistor to form a series circuit, and the series circuit is connected to the ping-pong switching circuit. The method for monitoring the insulation resistance of the through bolt includes:

[0063] Applying a DC excitation voltage to the series circuit, equivalent the insulation resistance monitoring circuit to a first equivalent circuit assuming a single-point grounding fault occurs in the through bolt, determine the first circuit parameters of the first equivalent circuit when the corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, determine the first insulation resistance value according to the DC excitation voltage and the first circuit parameters, and determine whether there is a single-point grounding fault in the through bolt according to the first insulation resistance value;

[0064] When there is a single-point grounding fault in the through bolt, determine the first grounding point in the through bolt;

[0065] In the case where there is a single-point grounding fault in the through bolt, equivalent the insulation resistance monitoring circuit to a second equivalent circuit assuming a two-point grounding fault occurs in the through bolt, determine the second circuit parameters of the second equivalent circuit when the corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, determine the second insulation resistance value according to the DC excitation voltage and the second circuit parameters, and determine whether there is a two-point grounding fault in the through bolt according to the second insulation resistance value;

[0066] When there is a two-point grounding fault in the through bolt, determine the two grounding points in the through bolt, where one of the grounding points is the first grounding point when there is a single-point grounding fault in the through bolt, and the other grounding point is the second grounding point when there is a two-point grounding fault in the through bolt.

[0067] Specifically, as Figure 2As shown, all the through bolts in the stator are connected in series by isolation resistors. An external DC excitation voltage is applied to the series circuit formed by alternately connecting the through bolts and isolation resistors. By switching the switches of the ping-pong switching circuit, the connection mode of the circuit is changed to monitor the ground fault of the through bolts. The DC excitation voltage is used to drive the current flow in the circuit, thereby generating measurable current and voltage signals for subsequent analysis of circuit parameters and detection of faults. The insulation resistance monitoring circuit includes each through bolt of the generator, isolation resistors, and a ping-pong switching circuit. The insulation resistance monitoring circuit assuming a single-point ground fault of the through bolt is equivalent to a first equivalent circuit. By controlling the switch states of the ping-pong switching circuit, the first circuit parameters of the first equivalent circuit in different switch states are determined. Based on the first circuit parameters and the DC excitation voltage, the first insulation resistance value is determined, and then it is judged whether the through bolt has a single-point ground fault according to the first insulation resistance value. When it is monitored that the through bolt does not have a single-point ground fault, the monitoring of the ground fault of the through bolt continues; when it is monitored that the through bolt has a single-point ground fault, the first ground point of the single-point ground fault of the through bolt is further confirmed, so as to facilitate the maintenance personnel to quickly and accurately find the fault location, shorten the troubleshooting time, and avoid unnecessary component replacement or large-scale disassembly inspection; it also helps to take targeted measures in a timely manner to repair the fault point, prevent the fault from further expanding or causing secondary faults, and ensure the safe and stable operation of the equipment. When it is monitored that there is a single-point ground fault of the through bolt, it is further monitored whether the through bolt has a two-point ground fault. By equivalent the insulation resistance monitoring circuit assuming a two-point ground fault of the through bolt to a second equivalent circuit, controlling the switch states of the ping-pong switching circuit, determining the second circuit parameters of the second equivalent circuit in different switch states, determining the second insulation resistance value according to the second circuit parameters and the DC excitation voltage, and then judging whether the through bolt has a two-point ground fault according to the second insulation resistance value. Since a single-point ground fault of the through bolt occurs first before a two-point ground fault of the through bolt, when the through bolt has a two-point ground fault, one of the two ground points in the through bolt is the ground point when the through bolt has a single-point ground fault. When further confirming the two-point ground fault of the through bolt, the position of the other ground point is determined.

[0068] In this embodiment, all the through bolts in the stator are connected in series through isolation resistors. By switching the switches of the ping-pong circuit, the connection mode of the circuit is changed. Under different switch states, the circuit parameters in the circuit will change. By measuring the circuit parameters, real-time monitoring and protection of the through bolts can be achieved, the resistance value of the insulation resistance of the through bolts can be further confirmed, so as to accurately know the degree of decline in the insulation ability of the stator through bolts, and potential faults can be predicted and prevented. And when there is a single-point grounding fault, the grounding point of the through bolt with the grounding fault can be determined. By accurately locating the fault point, maintenance resources can be reasonably arranged, unnecessary component replacement or large-scale disassembly and inspection can be avoided, and the maintenance cost can be reduced. When it is monitored that there is a single-point grounding fault in the through bolt, the circuit parameters in the second equivalent circuit assuming that the through bolt has a two-point grounding fault are further monitored, the second insulation resistance value of the through bolt is determined, and it is judged whether the through bolt has a two-point grounding. When the through bolt has a two-point grounding fault, the positions of the two grounding points of the through bolt are determined, which is convenient for maintenance personnel to quickly and accurately find the fault position, shorten the troubleshooting time, improve the maintenance efficiency, and reduce the losses caused by equipment shutdown. And when there is a single-point grounding of the through bolt, a first-level alarm can be sent to the staff to ensure that the operation and maintenance personnel are notified of the fault in a short time; when there is a two-point grounding of the through bolt, a second-level alarm can be sent, and the circuit can be cut off within a preset time to avoid the expansion of the accident. By monitoring the insulation resistance value, the insulation state of the through bolts in the generator stator can be grasped in real time, potential fault risks can be discovered in time, thereby improving the safety and reliability of the generator operation. By determining the grounding point of the through bolt, it helps to take targeted measures in time to repair the fault point, prevent the further expansion of the fault or the occurrence of secondary faults, and ensure the safe and stable operation of the generator.

[0069] Optionally, the first equivalent circuit includes an equivalent excitation power supply U corresponding to the DC excitation voltage e , the first series equivalent circuit corresponding to the series circuit, the first insulation resistance R g1 , and the corresponding equivalent circuit of the ping-pong switching circuit. The first series equivalent circuit is connected in parallel with the equivalent excitation power supply. The first series equivalent circuit includes a first isolation resistor R x1 and a second isolation resistor R x2 connected in series. The first isolation resistor R x1 is the equivalent resistance of all the isolation resistors between the first assumed grounding point in the through bolt when a single-point grounding fault is assumed and the positive pole of the equivalent excitation power supply. The second isolation resistor is the equivalent resistance of all the isolation resistors between the first assumed grounding point and the negative pole of the equivalent excitation power supply. The first insulation resistance is the insulation resistance of the first assumed grounding point;

[0070] The corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit includes a first sampling resistor R 21 and the first switching resistor R 11 , and the first switching resistor R 11 The first switching switch S1 is connected in parallel, and the second sampling resistor R is connected in series. 22 and the second switching resistor R 12 , and the second switching resistor R 12 The second switching switch S2 is connected in parallel, and the first switching resistor R 11 Keep away from the first sampling resistor R 21 One end and the second switching resistor R 12 Keep away from the second sampling resistor R 22 One end of each of the first sampling resistors R 21 away from the first switching resistor R 11 One end of the second sampling resistor R 22 Away from the second switching resistor R 12 One end of the first insulation resistor R is connected to form a second connection point. g1 The first isolation resistor R x1 and the second isolation resistor R x2 The first connection point P between g1 connect.

[0071] Specifically, the first equivalent circuit is as follows Figure 3 As shown, the first isolation resistor R x1 One end of the equivalent excitation power supply U e The other end is connected to the positive pole of the second isolation resistor R x2 Connect the second isolation resistor R x2 Keep away from the first isolation resistor R x1 Connect one end to the equivalent excitation power supply U e negative connection.

[0072] In this way, by controlling the closing and opening of the first switch S1 and the second switch S2 of the corresponding equivalent circuit in the first equivalent circuit of the ping-pong switching circuit, the circuit connection mode is changed, thereby changing the circuit's operating state. Circuit parameters are determined when the first switch S1 is open and the second switch S2 is closed, and when the first switch S1 is closed and the second switch S2 is open. By measuring circuit parameters in different switching states and accurately determining the insulation resistance value and the grounding point location of the ground fault based on these circuit parameters, it is possible to effectively identify whether a ground fault exists in the through-screw and improve the accuracy of locating the fault point.

[0073] Optionally, when determining that the corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, the first circuit parameter of the first equivalent circuit, and determining the first insulation resistance value according to the DC excitation voltage and the first circuit parameter include:

[0074] Determine the first parameter of the first equivalent circuit in the first switch state and the second parameter of the first equivalent circuit in the second switch state;

[0075] Based on Kirchhoff's law, construct a first set of equations according to the first loop, the second loop, and the third loop;

[0076] Substitute the DC excitation voltage and the first parameter into the first set of equations to obtain a first parameter set of equations;

[0077] Substitute the DC excitation voltage and the second parameter into the first set of equations to obtain a second parameter set of equations;

[0078] Confirm the first insulation resistance value according to the first parameter set of equations and the second parameter set of equations;

[0079] Wherein, in the first equivalent circuit, the first sampling resistor, the first switching resistor, the first isolation resistor, and the first insulation resistor form the first loop, the second sampling resistor, the second switching resistor, the second isolation resistor, and the first insulation resistor form the second loop, the first switch state includes the first switching switch being off and the second switching switch being on, the second switch state includes the first switching switch being on and the second switching switch being off, and the first circuit parameter includes the first parameter and the second parameter.

[0080] Specifically, in the first switch state, S1 is off and S2 is on. The first equivalent circuit in the first switch state is as Figure 4 shown, U e represents the equivalent excitation power supply in the first switch state, I1 represents the current flowing through the first sampling resistor R 21 and the first switching resistor R 11 in the first switch state; I2 represents the current flowing through the second sampling resistor R 22 in the first switch state; I g1 represents the current flowing through the first insulation resistor R g1 in the first switch state. In the second switch state, S1 is on and S2 is off. The first equivalent circuit in the second switch state is as Figure 5 shown, I1 ′ represents the current flowing through the first sampling resistor R 21 in the second switch state; I2 ′ represents the current flowing through the second switching resistor R12 and the second sampling resistor R 22 Current; I′ g1 Indicates that the current flowing through the first insulation resistor R in the second switching state g1 The current of the first sampling resistor R can be obtained through a digital converter or a voltmeter. 21 The voltage across the first switching resistor R 11 The voltage across the two ends can be obtained by Ohm's law, which flows through the first sampling resistor R 21 and the first switching resistor R 11 The current I1 is obtained in the same way. The current I2 and I1 are obtained in the same way. ′ , I2 ′ The value of the first isolation resistor R x1 is the equivalent resistance of the isolation resistance between the first assumed grounding point in the through screw and the positive electrode of the equivalent excitation power supply when a ground fault occurs, and the second isolation resistance R x2 is the equivalent resistance of the isolation resistor between the first assumed ground point and the negative electrode of the equivalent excitation power supply. The resistance values of the first isolation resistor and the second isolation resistor are unknown. Kirchhoff's law can be used to derive equations between the various loops in the first equivalent circuit in the first switching state, yielding equations for the first isolation resistor, the second isolation resistor, and the first insulation resistance in the first switching state. Furthermore, equations between the various loops in the first equivalent circuit in the second switching state yield another equation for the first isolation resistor, the second isolation resistor, and the first insulation resistance in the first switching state. These two equations can be combined to yield the resistance value of the first insulation resistor.

[0081] Specifically, if Figure 4 As shown, based on Kirchhoff's law, the first parametric equation group can be obtained as follows:

[0082]

[0083] Among them, U e Represents the equivalent excitation power supply in the first switching state, and I1 represents the current flowing through the first sampling resistor R in the first switching state. 21 and the first switching resistor R 11 I2 represents the current flowing through the second sampling resistor R in the first switching state. 22 Current; I g1 Indicates that the current flowing through the first insulation resistor R in the first switching state g1 Current; R x1 Represents the first isolation resistor, R x2 Represents the second isolation resistor, R g1 Indicates the first insulation resistance, R 11 Represents the first switching resistor, R 21 Represents the first sampling resistor, R22 Represents the second sampling resistor.

[0084] like Figure 5 As shown, based on Kirchhoff's law, the second parametric equation group can be obtained as follows:

[0085]

[0086] Among them, U′ e represents the equivalent excitation power supply in the second switching state, and I′1 represents the current flowing through the first sampling resistor R in the second switching state. 21 I′2 represents the current flowing through the second sampling resistor R in the second switching state. 22 and the second switching resistor R 12 Current; I′ g1 Indicates the current flowing through the first insulation resistor in the second switching state; R x1 Represents the first isolation resistor, R x2 Represents the second isolation resistor, R g1 Indicates the first insulation resistance, R 21 Represents the second switching resistor, R 21 Represents the first sampling resistor, R 22 The first parameter equation group (1) and the second parameter equation group (2) are solved to obtain the first insulation resistance value.

[0087] By controlling the switch state and measuring the current and voltage in different states, the through-screw can be monitored and protected in real time. Ping-pong circuit switching allows for multiple sets of current and voltage data to be acquired under different connection configurations. By combining the equivalent circuit with simultaneous equations using Kirchhoff's laws, the first insulation resistance value is derived. By monitoring the insulation resistance, the insulation status of the through-screw in the generator stator can be monitored in real time, enabling timely identification of potential fault risks and improving the safety and reliability of generator operation.

[0088] Optionally, when a grounding fault occurs at one point in the through-screw, determining the first grounding point in the through-screw includes:

[0089] Determine a first isolation resistor value and a second isolation resistor value according to the first insulation resistor value;

[0090] The position of the first assumed grounding point relative to the DC excitation voltage is determined based on a relationship between the first isolation resistor resistance and / or the second isolation resistor resistance and the total isolation resistor resistance, wherein the sum of the first isolation resistor resistance and the second isolation resistor resistance is equal to the total isolation resistor resistance.

[0091] Specifically, by solving the simultaneous first parameter equation set (1) and second parameter equation set (2), the value of the first insulation resistance is obtained, and the values of the first isolation resistance and the second isolation resistance are determined. When it is determined that the through-bolt has a single-point grounding fault based on the value of the first insulation resistance, the location of the single-point grounding fault of the through-bolt is determined. The sum of the value of the first isolation resistance and the value of the second isolation resistance is equal to the total value of the isolation resistance. By determining the ratio of the value of the first isolation resistance to the total value of the isolation resistance, or by determining the ratio of the value of the second isolation resistance to the total value of the isolation resistance, or by determining the ratio of the value of the first isolation resistance to the total value of the isolation resistance, or by determining the ratio of the value of the second isolation resistance to the total value of the isolation resistance, the location of the first grounding point is determined. When the ratio of the value of the first isolation resistance to the total value of the isolation resistance is equal to 0.6, it indicates that the first grounding point is at the 60% position relative to the positive pole of the DC excitation voltage in the loop composed of all through-bolts. For example, if there are 10 through-bolts in a generator and the through-bolts are connected in series with isolation resistors at intervals, when the ratio of the value of the first isolation resistance to the total value of the isolation resistance is equal to 0.6, it indicates that the first monitoring point is located at the position of the sixth through-bolt in the direction of the positive pole of the DC excitation voltage. When the ratio of the value of the second isolation resistance to the total value of the isolation resistance is equal to 0.4, it indicates that the first monitoring point occurs at the 40% position of the negative pole of the applied DC excitation voltage. When the first insulation resistance is less than the preset threshold, it indicates that a grounding fault occurs at the first monitoring point, that is, it indicates that the through-bolt at the 60% position of the positive pole of the applied DC excitation voltage in the generator has a grounding fault.

[0092] In this optional embodiment, the position of the first monitoring point is determined by calculating the ratio of the isolation resistances on both sides of the first monitoring point to the total value of the isolation resistance. When the value of the first insulation resistance of the through-bolt is less than the first preset insulation resistance, it is determined that there is a single-point grounding of the through-bolt, and then the relative position of the through-bolt with the grounding fault relative to the applied DC voltage is determined. Precise fault location helps to accurately identify the specific location where the fault occurs, enables rapid response to maintenance, and can significantly reduce the time required for fault troubleshooting and repair.

[0093] Optionally, the determination of whether there is a single-point grounding fault of the through-bolt according to the value of the first insulation resistance includes:

[0094] When the value of the first insulation resistance is less than the first preset insulation resistance value, it is determined that there is the single-point grounding fault of the through-bolt;

[0095] When the value of the first insulation resistance is greater than or equal to the first preset insulation resistance value, it is determined that there is no single-point grounding fault of the through-bolt.

[0096] Specifically, by measuring the value of the first insulation resistance, it is determined whether there is a single-point grounding of the through-bolt. When it is monitored that the value of the first insulation resistance is less than the first preset insulation resistance value, it indicates that there is a single-point grounding fault of the through-bolt. In the case of a single-point grounding fault of the through-bolt, it is further monitored whether there is a two-point grounding of the through-bolt. When the value of the first insulation resistance is greater than or equal to the first preset insulation resistance value, it is determined that there is no single-point grounding fault of the through-bolt. In the case of no single-point grounding fault of the through-bolt, the insulation resistance value in the through-bolt is continuously monitored. The first preset insulation resistance value can be set according to the actual application scenario and safety standards. The first preset insulation resistance value is usually determined comprehensively according to factors such as the rated voltage of the generator, the insulation requirements of the stator through-bolt, and the actual operating environment. This preset value can be adjusted according to different generator models and operating conditions. For example, for a generator operating in a high-humidity environment, the preset insulation resistance value can be appropriately reduced to adapt to the impact of environmental changes on the insulation performance.

[0097] In this alternative embodiment, by monitoring the insulation resistance value, it is determined whether there is a single-point grounding fault of the through-bolt according to the first preset insulation resistance value. When the value of the first insulation resistance is less than the first preset insulation resistance value, it is determined that there is a single-point grounding fault of the through-bolt; when the value of the first insulation resistance is greater than or equal to the first preset insulation resistance value, it is determined that there is no single-point grounding fault of the through-bolt. And an alarm or early warning mechanism can be set. When it is monitored that there is a single-point grounding fault of the through-bolt, the technical personnel are notified that there is a grounding fault in the generator and immediate inspection and repair are required. When the insulation resistance value is close to the preset value, a warning signal is sent to remind the maintenance personnel to pay attention. Thus, real-time and accurate monitoring and early warning of the grounding fault of the stator through-bolt of the generator can be realized, effectively improving the safety and reliability of the generator operation, reducing the losses and risks brought by the fault, and ensuring the stable operation of the generator.

[0098] Optionally, the second equivalent circuit includes an equivalent excitation power supply U corresponding to the DC excitation voltage e , the second series equivalent circuit corresponding to the series circuit, the first insulation resistance, the second insulation resistance, and the corresponding equivalent circuit of the ping-pong switching circuit. The second series equivalent circuit is connected in parallel with the equivalent excitation power supply. The second series equivalent circuit includes a third isolation resistance R x3 , a fourth isolation resistance R x4 and a fifth isolation resistance R x5 that are connected in series with each other. The third isolation resistance R x5 is the equivalent resistance of all the isolation resistances between the first grounding point and one end of the equivalent excitation power supply. The fifth isolation resistance R x5is the equivalent resistance of all isolation resistors between the second assumed grounding point in the through screw and the other end of the equivalent excitation power supply when a two-point grounding fault occurs. The fourth isolation resistor R x4 is the equivalent resistance of all isolation resistances between the first grounding point and the second assumed grounding point, the first insulation resistance is the insulation resistance of the first grounding point, and the second insulation resistance is the insulation resistance of the second assumed grounding point;

[0099] The corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit includes a first sampling resistor R 21 and the first switching resistor R 11 , and the first switching resistor R 11 The first switching switch S1 is connected in parallel, and the second sampling resistor R is connected in series. 22 and the second switching resistor R 12 , and the second switching resistor R 12 The second switching switch S2 is connected in parallel, and the first switching resistor R 11 Keep away from the first sampling resistor R 21 One end and the second switching resistor R 12 Keep away from the second sampling resistor R 22 One end of each of the first sampling resistor R 21 away from the first switching resistor R 11 One end of the second sampling resistor R 22 Away from the second switching resistor R 12 One end of the first isolation resistor is connected to form a third connection point, a fourth connection point between the third isolation resistor and the fourth isolation resistor is connected to the third connection point through the first insulation resistor, and a fifth connection point between the fourth isolation resistor and the fifth isolation resistor is connected to the third connection point through the second insulation resistor.

[0100] Specifically, the second equivalent circuit is as follows Figure 6 As shown, the third isolation resistor R x3 is the equivalent resistance of all isolation resistors between the first grounding point and the negative electrode of the equivalent excitation power supply, the fifth isolation resistor R x5 is the equivalent resistance of all isolation resistors between the second assumed grounding point in the through screw and the positive electrode of the equivalent excitation power supply when a two-point grounding fault occurs, and the fourth isolation resistor R x4 is the equivalent resistance of all isolation resistors between the first ground point and the second hypothetical ground point.

[0101] By controlling the closing and opening of S1 and S2 in the second equivalent circuit, the connection mode of the circuit is changed, thereby changing the current and voltage parameters in the circuit. By measuring these parameters, the value of the second insulation resistance can be determined.

[0102] Optionally, when determining the second circuit parameters of the second equivalent circuit in different states of the corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit, determining the value of the second insulation resistance according to the DC excitation voltage and the second circuit parameters includes:

[0103] When the second assumed grounding point is between the first grounding point and the positive pole of the equivalent excitation power supply, determine the third parameter of the second equivalent circuit in the first switch state and the fourth parameter of the second equivalent circuit in the second switch state;

[0104] Based on Kirchhoff's law, construct a second set of equations according to the fourth loop, the fifth loop and the sixth loop;

[0105] Substitute the DC excitation voltage and the third parameter into the second set of equations to obtain a third parameter set of equations;

[0106] Substitute the DC excitation voltage and the fourth parameter into the second set of equations to obtain a fourth parameter set of equations;

[0107] Confirm the value of the second insulation resistance according to the third parameter set of equations and the fourth parameter set of equations;

[0108] Wherein, the fifth isolation resistance, the first sampling resistance, the first switching resistance and the second insulation resistance form a fourth loop; the third isolation resistance, the second sampling resistance, the second switching resistance and the first insulation resistance form a fifth loop, the first insulation resistance, the second insulation resistance and the fourth isolation resistance form a sixth loop, the second circuit parameters include the third parameter and the fourth parameter, the first switch state includes the first switching switch being disconnected and the second switching switch being closed, and the second switch state includes the first switching switch being closed and the second switching switch being disconnected.

[0109] Specifically, in the first switch state, S1 is disconnected and S2 is closed. The second equivalent circuit in the first switch state is as Figure 7 shown, U e represents the equivalent excitation power supply in the first switch state, I3 represents the current flowing through the first sampling resistance R 21 and the first switching resistance R 11 in the first switch state; I4 represents the current flowing through the second sampling resistance R 22 in the first switch state; I g3Indicates the current flowing through the first insulation resistor R in the first switch state g1 ; I g4 Indicates the current flowing through the second insulation resistor R in the first switch state g2 . In the second switch state, S1 is closed and S 21 is open. The second equivalent circuit in the second switch state is as shown in Figure 8 . I′3 indicates the current flowing through the first sampling resistor R 21 in the second switch state; I′4 indicates the current flowing through the second sampling resistor R 22 and the second switching resistor R 12 in the second switch state; I′ g3 indicates the current flowing through the first insulation resistor R g1 in the second switch state; I′ g4 indicates the current flowing through the second insulation resistor R g2 in the second switch state. The voltage across the first sampling resistor or the first switching resistor can be obtained through a digital converter or a voltmeter, and the current I3 flowing through the first sampling resistor R 21 and the first switching resistor R 11 can be obtained through Ohm's law. The values of the currents I4, I′3, and I′4 are obtained in the same way. The resistances of the second insulation resistor, the third isolation resistor, the fourth isolation resistor, and the fifth isolation resistor are unknown. When the second assumed grounding point is between the first grounding point and the positive pole of the DC excitation power supply (i.e., the equivalent excitation power supply), the resistance value of the third isolation resistor is equal to the resistance value of the second isolation resistor; when the second assumed grounding point is between the first grounding point and the negative pole of the DC excitation voltage, the resistance value of the fifth isolation resistor is equal to the resistance value of the first isolation resistor. According to Kirchhoff's law, the equations between the loops in the second equivalent circuit in the first switch state can be obtained

[0110] As shown in Figure 6 , based on Kirchhoff's law, when the second assumed grounding point is between the first grounding point and the positive pole of the DC power supply and in the first switch state, the third parameter equation set can be obtained as follows

[0111]

[0112] Among them, U e represents the equivalent excitation power supply in the first switch state, I3 represents the current flowing through the first sampling resistor R 21 and the first switching resistor R 11 in the first switch state; I4 represents the current flowing through the second sampling resistor R 22 in the first switch state; I g3 represents the current flowing through the first insulation resistor R g1 in the first switch state, I g4Indicates the current flowing through the second insulation resistance R in the first switch state g2 ; I x3 Indicates the current flowing through the third isolation resistance R in the first switch state x3 ; I x4 Indicates the current flowing through the fourth isolation resistance R in the first switch state x4 ; I x5 Indicates the current flowing through the fifth isolation resistance R in the first switch state x5 ; R x2 Indicates the second isolation resistance; R x3 Indicates the third isolation resistance, R x4 Indicates the fourth isolation resistance, R x5 Indicates the fifth isolation resistance; R g1 Indicates the first insulation resistance, R g2 Indicates the second insulation resistance, R 11 Indicates the first switching resistance, R 21 Indicates the first sampling resistance, R 22 Indicates the second sampling resistance.

[0113] As Figure 7 shown, based on Kirchhoff's law, when the second assumed grounding point is between the first grounding point and the positive pole of the DC power supply and in the second switch state, the fourth parameter equation set can be obtained as follows:

[0114]

[0115] Wherein, U′ e Indicates the equivalent excitation power supply in the second switch state, I′3 indicates the current flowing through the first sampling resistance R in the second switch state 21 ; I′4 indicates the current flowing through the second sampling resistance R 22 and the second switching resistance R 12 ; I′ g3 Indicates the current flowing through the first insulation resistance R in the second switch state g1 ; I′ g4 Indicates the current flowing through the second insulation resistance R in the second switch state g2 ; I′ x3 Indicates the current flowing through the third isolation resistance R in the second switch state x3 ; I′ x4 Indicates the current flowing through the fourth isolation resistance R in the second switch state x4 ; I′ x5 Indicates the current flowing through the fifth isolation resistance in the second switch state; R x2 Indicates the second isolation resistance; R x3 Indicates the third isolation resistance, R x4 Indicates the fourth isolation resistance, R x5Represents the fifth isolation resistor; R g1 Represents the first insulation resistor, R g2 Represents the second insulation resistor, R 21 Represents the second switching resistor, R 21 Represents the first sampling resistor, R 22 Represents the second sampling resistor.

[0116] By simultaneously solving the third parameter equations (3) and the fourth parameter equations (4), the resistance value of the second insulation resistor is obtained.

[0117] Optionally, when determining that the corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, the second circuit parameters of the second equivalent circuit, and determining the resistance value of the second insulation resistor according to the DC excitation voltage and the second circuit parameters further include:

[0118] When the second assumed grounding point is between the first grounding point and the negative pole of the equivalent excitation power supply, determine the fifth parameter of the second equivalent circuit in the first switch state and the sixth parameter of the second equivalent circuit in the second switch state;

[0119] Based on Kirchhoff's law, construct the third set of equations according to the seventh loop, the eighth loop and the ninth loop;

[0120] Substitute the DC excitation voltage and the fifth parameter into the third set of equations to obtain the fifth parameter equations;

[0121] Substitute the DC excitation voltage and the sixth parameter into the third set of equations to obtain the sixth parameter equations;

[0122] Confirm the resistance value of the second insulation resistor according to the fifth parameter equations and the sixth parameter equations, where the third isolation resistor, the first sampling resistor, the first switching resistor and the first insulation resistor form the seventh loop; the fifth isolation resistor, the second sampling resistor, the second switching resistor and the second insulation resistor form the eighth loop, the first insulation resistor, the second insulation resistor and the fourth isolation resistor form the ninth loop, the second circuit parameters further include the fifth parameter and the sixth parameter, the first switch state includes the first switching switch being off and the second switching switch being on, and the second switch state includes the first switching switch being on and the second switching switch being off.

[0123] Specifically, as Figure 9 shown, based on Kirchhoff's law, when the second assumed point is between the first grounding point and the negative pole of the DC power supply and in the first switch state, the fifth parameter equations can be obtained as:

[0124]

[0125] Among them, U e represents the equivalent excitation power supply, and I3 represents the current flowing through the first sampling resistor R 21 and the first switching resistor R 11 ; I4 represents the current flowing through the second sampling resistor R 22 ; I g3 represents the current flowing through the first insulation resistor R g1 ; I g4 represents the current flowing through the second insulation resistor R g2 ; I x3 represents the current flowing through the third isolation resistor R x3 ; I x4 represents the current flowing through the fourth isolation resistor R x4 ; I x5 represents the current flowing through the fifth isolation resistor R x5 ; R x2 represents the second isolation resistor; R x3 represents the third isolation resistor, R x4 represents the fourth isolation resistor, R x5 represents the fifth isolation resistor; R g1 represents the first insulation resistor, R g2 represents the second insulation resistor, R 11 represents the first switching resistor, R 21 represents the first sampling resistor, R 22 represents the second sampling resistor.

[0126] As Figure 9 shown, based on Kirchhoff's law, when the second assumed ground point is located between the first ground point and the negative pole of the DC power supply, the sixth parameter equation set can be obtained as follows:

[0127]

[0128] Among them, U′ e represents the equivalent excitation power supply, and I′3 represents the current flowing through the first sampling resistor R 21 and the first switching resistor R 11 ; I′4 represents the current flowing through the second sampling resistor R 22 ; I′ g3 represents the current flowing through the first insulation resistor R g1 ; I′ g4 represents the current flowing through the second insulation resistor R g2 ; I′ x3 represents the current flowing through the third isolation resistor R x3 ; I′ x4 represents the current flowing through the fourth isolation resistor R x4 ; I′x5 Represents the current flowing through the fifth isolation resistor; R x2 Represents the second isolation resistor; R x3 Represents the third isolation resistor, R x4 Represents the fourth isolation resistor, R x5 Represents the fifth isolation resistor; R g1 Indicates the first insulation resistance, R g2 Represents the second insulation resistance, R 21 Represents the second switching resistor, R 21 Represents the first sampling resistor, R 22 Represents the second sampling resistor.

[0129] The second insulation resistance value is obtained by solving the fifth parameter equation group (5) and the sixth parameter equation group (6) simultaneously.

[0130] It can be assumed that when the second hypothetical grounding point is located between the first grounding point and the positive pole of the DC power supply, the resistance of the third isolation resistor in the equivalent circuit is equal to the resistance of the second isolation resistor. Substitute the resistance of the second isolation resistor into the equation group (3) and the equation group (4) to obtain the resistance of the second insulation resistor, and further obtain the resistance of the fifth isolation resistor. The second insulation resistor value is determined based on the fact that the sum of the resistance of the third isolation resistor and the resistance of the fifth isolation resistor is less than the total resistance of the isolation resistor. When the value of the fifth isolation resistor satisfies the condition that the sum of the resistance of the third isolation resistor and the resistance of the fifth isolation resistor is less than the total resistance of the isolation resistor, it indicates that the second hypothetical grounding point is located between the first grounding point and the positive pole of the equivalent excitation power supply, and the second insulation resistor value that meets the condition is the desired value. When the obtained resistance value of the fifth isolation resistor does not satisfy the condition that the sum of the resistance value of the third isolation resistor and the resistance value of the fifth isolation resistor is less than the total resistance value of the isolation resistor, it means that the second hypothetical grounding point is located between the first grounding point and the negative pole of the equivalent excitation power supply. At this time, the resistance value of the fifth isolation resistor in the equivalent circuit is equal to the resistance value of the first isolation resistor. Substitute the resistance value of the first isolation resistor into the equation group (5) and the equation group (6) to obtain the resistance value of the second isolation resistor, and further obtain the resistance value of the third isolation resistor. The second isolation resistor value is determined based on the fact that the sum of the resistance value of the first isolation resistor and the third isolation resistor is less than the total resistance value of the isolation resistor. The second insulation resistor that satisfies the condition that the sum of the resistance value of the third isolation resistor and the fifth isolation resistor is less than the total resistance value of the isolation resistor is the desired second insulation resistor.

[0131] Optionally, when there is a two-point grounding fault in the through screw, determining the two grounding points in the through screw includes:

[0132] Determine the third isolation resistor value, the fourth isolation resistor value, and the fifth isolation resistor value according to the second insulation resistance value;

[0133] Determine the position of the second assumed ground point relative to the DC excitation voltage according to the relationship between the sum of the resistance values of the third isolation resistor and the fourth isolation resistor and the total resistance value of the isolation resistor, and / or according to the relationship between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor, wherein the sum of the resistance values of the third isolation resistor, the fourth isolation resistor and the fifth isolation resistor is equal to the total resistance value of the isolation resistor.

[0134] Specifically, the sum of the resistance values of the third isolation resistor, the fourth isolation resistor and the fifth isolation resistor is equal to the total resistance value of the isolation resistor. Determine the position of the second ground point through the ratio between the sum of the resistance values of the third isolation resistor and the fourth isolation resistor and the total resistance value of the isolation resistor; or determine the position of the second ground point according to the ratio between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor; or determine the position of the second ground point through the ratio between the sum of the resistance values of the third isolation resistor and the fourth isolation resistor and the total resistance value of the isolation resistor, and the ratio between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor. For example, when it is determined that the second ground point is located between the first ground point and the positive pole of the DC excitation voltage, when the ratio between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor is equal to 0.3, it indicates that the second ground point occurs at the position of 30% of the positive pole of the applied DC excitation voltage. For example, a generator has a total of 10 through bolts, and the through bolts are connected in series with isolation resistors at intervals. When the ratio between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor is equal to 0.3, it indicates that the second monitoring point is located at the position of the third through bolt in the direction of the positive pole of the DC excitation voltage.

[0135] In this optional embodiment, determine the position of the second ground point by calculating the ratio of the isolation resistors on both sides of the second ground point to the total resistance value of the isolation resistor. When the resistance value of the second insulation resistor is less than the second preset insulation resistance value, it is possible to accurately determine that a two-point grounding fault has occurred on the through bolt, and further determine the relative positions of the two ground points and the DC excitation voltage when the two-point grounding occurs on the through bolt. Precise grounding positioning can reduce the time required to find the fault, thereby shortening the downtime, quickly restoring the operation of the generator, and reducing production losses. By promptly detecting and locating the grounding fault and locating the specific fault point, unnecessary comprehensive disassembly and inspection can be avoided, reducing the maintenance workload and cost. It can also prevent the further deterioration of the fault, avoid possible electrical fires or equipment damage, and thus improve the safety of the entire generator.

[0136] Optionally, the determination of whether there is a two-point grounding fault on the through bolt according to the resistance value of the second insulation resistor includes:

[0137] When the resistance value of the second insulation resistor is less than the second preset insulation resistance value, it is determined that there is the two-point grounding fault on the through bolt;

[0138] When the value of the second insulation resistance is greater than or equal to the second preset insulation resistance value, it is determined that there is no two-point grounding fault of the through-bolt, and there is a one-point grounding fault of the through-bolt.

[0139] Specifically, by measuring the value of the second insulation resistance, it is determined whether there is a two-point grounding fault of the through-bolt. When it is monitored that the value of the second insulation resistance is less than the second preset insulation resistance value, it indicates that there is a two-point grounding fault of the through-bolt. When it is monitored that the value of the second insulation resistance is greater than or equal to the second preset insulation resistance value, it is determined that there is no two-point grounding fault of the through-bolt, and there is a one-point grounding fault of the through-bolt. The second preset insulation resistance value can be set according to the actual application scenario and safety standards. The second preset insulation resistance value can be adjusted according to different generator models and operating conditions. For example, for a generator operating in a high-humidity environment, the preset insulation resistance value can be appropriately reduced to adapt to the influence of environmental changes on the insulation performance. A trigger alarm or early warning mechanism can be set. Since the generator first has a one-point grounding fault of the through-bolt and then a two-point grounding fault of the through-bolt, when it is monitored that the value of the first insulation resistance is less than the first preset insulation resistance value and the value of the second insulation resistance is greater than or equal to the preset insulation resistance value, it indicates that there is a one-point grounding fault of the through-bolt. At this time, a first-level alarm can be set to send to the staff, such as notifying the operation and maintenance personnel by email or text message, to ensure that the fault is discovered and processed in a short time; when it is monitored that the value of the second insulation resistance is less than the second preset insulation resistance value, it indicates that there is a two-point grounding fault of the through-bolt. At this time, a second-level alarm can be set, such as automatic shutdown and cutting off the circuit within a preset time to avoid the expansion of the accident. For example, the power supply of the generator can be automatically cut off within 5 seconds after detecting the two-point grounding fault to prevent the further deterioration of the fault.

[0140] In this optional embodiment, by monitoring the value of the second insulation resistance, it is determined whether there is a two-point grounding fault of the through-bolt according to the second preset insulation resistance value. When there is a one-point grounding fault of the through-bolt, a first-level alarm (email / text message) can be sent to the staff to ensure that the operation and maintenance personnel are notified of the fault in a short time; when there is a two-point grounding fault of the through-bolt, a second-level alarm (automatic shutdown) can be issued to cut off the circuit within a preset time to avoid the expansion of the accident. Thus, by real-time monitoring the insulation resistance value of the through-bolt, the decrease in insulation performance can be detected at the initial stage of the fault, realizing early intervention and repair, and avoiding the further deterioration of the fault. Being able to detect and handle the grounding fault in time can prevent the generator from having more serious faults due to insulation problems, thereby improving the safety of the generator operation.

[0141] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A monitoring method for the insulation resistance of a through bolt, characterized in that, Based on an insulation resistance monitoring circuit, the insulation resistance monitoring circuit includes each through-screw of the generator, an isolation resistor, and a ping-pong switching circuit. Each through-screw and the isolation resistor are alternately connected in series to form a series circuit, and the series circuit is connected to the ping-pong switching circuit. The through-screw insulation resistance monitoring method includes: Applying a DC excitation voltage to the series circuit, equating the insulation resistance monitoring circuit to a first equivalent circuit assuming a single-point grounding fault occurs in the through-screw, determining first circuit parameters of the first equivalent circuit when a corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, determining a first insulation resistance value based on the DC excitation voltage and the first circuit parameter, and determining whether a single-point grounding fault occurs in the through-screw based on the first insulation resistance value; When there is a grounding fault at one point of the through screw, determining the first grounding point in the through screw; In the event of a single-point grounding fault on the through screw, the insulation resistance monitoring circuit is equivalent to a second equivalent circuit assuming a two-point grounding fault on the through screw, second circuit parameters of the second equivalent circuit are determined when a corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, a second insulation resistance value is determined based on the DC excitation voltage and the second circuit parameter, and whether there is a two-point grounding fault on the through screw is determined based on the second insulation resistance value; When a two-point grounding fault occurs in the through screw, two grounding points in the through screw are determined, wherein one grounding point is a first grounding point when a single-point grounding fault occurs in the through screw, and the other grounding point is a second grounding point when a two-point grounding fault occurs in the through screw.

2. The method for monitoring the insulation resistance of a through bolt according to claim 1, wherein The first equivalent circuit includes an equivalent excitation power supply corresponding to the DC excitation voltage, a first series equivalent circuit corresponding to the series circuit, a first insulation resistor, and an equivalent circuit corresponding to the ping-pong switching circuit. The first series equivalent circuit is connected in parallel with the equivalent excitation power supply. The first series equivalent circuit includes a first isolation resistor and a second isolation resistor connected in series with each other. The first isolation resistor is the equivalent resistance of all isolation resistors between a first assumed grounding point in the through screw and the positive pole of the equivalent excitation power supply when a single-point grounding fault is assumed. The second isolation resistor is the equivalent resistance of all isolation resistors between the first assumed grounding point and the negative pole of the equivalent excitation power supply. The first insulation resistor is the insulation resistance of the first assumed grounding point. The corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit includes a first sampling resistor and a first switching resistor connected in series, a first switching switch connected in parallel with the first switching resistor, a second sampling resistor and a second switching resistor connected in series, and a second switching switch connected in parallel with the second switching resistor. One end of the first switching resistor far from the first sampling resistor and one end of the second switching resistor far from the second sampling resistor are respectively connected to both ends of the first series equivalent circuit. One end of the first sampling resistor far from the first switching resistor is connected to one end of the second sampling resistor far from the second switching resistor to form a second connection point. The second connection point is connected to the first connection point between the first isolation resistor and the second isolation resistor through the first insulation resistor.

3. The monitoring method for the insulation resistance of the through bolt according to claim 2, characterized in that, When determining the first circuit parameter of the first equivalent circuit when the corresponding equivalent circuit of the ping-pong switching circuit in the first equivalent circuit is in different states, determining the first insulation resistor value according to the DC excitation voltage and the first circuit parameter includes: Determining the first parameter of the first equivalent circuit in the first switch state and the second parameter of the first equivalent circuit in the second switch state; Based on Kirchhoff's law, constructing a first set of equations according to the first loop, the second loop, and the third loop; Substituting the DC excitation voltage and the first parameter into the first set of equations to obtain a first parameter set of equations; Substituting the DC excitation voltage and the second parameter into the first set of equations to obtain a second parameter set of equations; Confirming the first insulation resistor value according to the first parameter set of equations and the second parameter set of equations; Wherein, in the first equivalent circuit, the first sampling resistor, the first switching resistor, the first isolation resistor, and the first insulation resistor form the first loop, the second sampling resistor, the second switching resistor, the second isolation resistor, and the first insulation resistor form the second loop. The first switch state includes the first switching switch being disconnected and the second switching switch being closed, the second switch state includes the first switching switch being closed and the second switching switch being disconnected, and the first circuit parameter includes the first parameter and the second parameter.

4. The method for monitoring the insulation resistance of the through bolt according to claim 2, wherein, When there is a single-point grounding fault of the through-bolt, determining the first grounding point in the through-bolt includes: Determining the first isolation resistor value and the second isolation resistor value according to the first insulation resistor value; Determining the position of the first assumed grounding point relative to the DC excitation voltage according to the relationship between the first isolation resistor value and / or the second isolation resistor value and the total isolation resistor value, wherein the sum of the first isolation resistor value and the second isolation resistor value is equal to the total isolation resistor value.

5. The method for monitoring the insulation resistance of the through bolt according to claim 1, wherein Judging whether there is a single-point grounding fault of the through-bolt according to the first insulation resistor value includes: When the first insulation resistor value is less than the first preset insulation resistor value, it is determined that there is a single-point grounding fault of the through-bolt; When the value of the first insulation resistance is greater than or equal to the first preset insulation resistance value, it is determined that there is no one-point grounding fault of the through bolt.

6. The method for monitoring the insulation resistance of the through bolt according to claim 1, characterized in that The second equivalent circuit includes an equivalent excitation power supply corresponding to the DC excitation voltage, a second series equivalent circuit corresponding to the series circuit, a first insulation resistance, a second insulation resistance, and an equivalent circuit of the ping-pong switching circuit. The second series equivalent circuit is connected in parallel with the equivalent excitation power supply. The second series equivalent circuit includes a third isolation resistance, a fourth isolation resistance, and a fifth isolation resistance connected in series with each other. The third isolation resistance is the equivalent resistance of all isolation resistances between the first grounding point and one end of the equivalent excitation power supply. The fifth isolation resistance is the equivalent resistance of all isolation resistances between the second assumed grounding point in the through bolt when a two-point grounding fault is assumed to occur and the other end of the equivalent excitation power supply. The fourth isolation resistance is the equivalent resistance of all isolation resistances between the first grounding point and the second assumed grounding point. The first insulation resistance is the insulation resistance of the first grounding point. The second insulation resistance is the insulation resistance of the second assumed grounding point. The equivalent circuit of the ping-pong switching circuit in the second equivalent circuit includes a first sampling resistance and a first switching resistance connected in series with each other, and a first switching switch connected in parallel with the first switching resistance, a second sampling resistance and a second switching resistance connected in series with each other, and a second switching switch connected in parallel with the second switching resistance. One end of the first switching resistance far from the first sampling resistance and one end of the second switching resistance far from the second sampling resistance are respectively connected to both ends of the second series equivalent circuit. One end of the first sampling resistance far from the first switching resistance and one end of the second sampling resistance far from the second switching resistance are connected to form a third connection point. The fourth connection point between the third isolation resistance and the fourth isolation resistance is connected to the third connection point through the first insulation resistance. The fifth connection point between the fourth isolation resistance and the fifth isolation resistance is connected to the third connection point through the second insulation resistance.

7. The method for monitoring the insulation resistance of the through bolt according to claim 6, characterized in that When determining the second circuit parameters of the second equivalent circuit when the equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in different states, determining the second insulation resistance value according to the DC excitation voltage and the second circuit parameters includes: When the second assumed grounding point is located between the first grounding point and the positive pole of the equivalent excitation power supply, determine the third parameter of the second equivalent circuit in the first switch state and the fourth parameter of the second equivalent circuit in the second switch state. Based on Kirchhoff's law, construct a second set of equations according to the fourth loop, the fifth loop, and the sixth loop. Substitute the DC excitation voltage and the third parameter into the second set of equations to obtain a third parameter set of equations. Substitute the DC excitation voltage and the fourth parameter into the second set of equations to obtain a fourth parameter set of equations. Confirm the second insulation resistance value according to the third parameter set of equations and the fourth parameter set of equations. The fifth isolation resistor, the first sampling resistor, the first switching resistor, and the second insulation resistor constitute a fourth loop; the third isolation resistor, the second sampling resistor, the second switching resistor, and the first insulation resistor constitute a fifth loop; the first insulation resistor, the second insulation resistor, and the fourth isolation resistor constitute a sixth loop; the second circuit parameter includes the third parameter and the fourth parameter; the first switch state includes the first switch being disconnected and the second switch being closed; and the second switch state includes the first switch being closed and the second switch being disconnected.

8. The method for monitoring the insulation resistance of the through bolt according to claim 6, wherein The determining of a second circuit parameter of the second equivalent circuit when a corresponding equivalent circuit of the ping-pong switching circuit in the second equivalent circuit is in a different state, and determining a second insulation resistance value according to the DC excitation voltage and the second circuit parameter further comprises: When the second assumed grounding point is between the first grounding point and the negative electrode of the equivalent excitation power supply, determining a fifth parameter of the second equivalent circuit in the first switching state and a sixth parameter of the second equivalent circuit in the second switching state; Based on Kirchhoff's law, a third equation group is constructed according to the seventh loop, the eighth loop and the ninth loop; Substituting the DC excitation voltage and the fifth parameter into the third set of equations to obtain a fifth set of parametric equations; Substituting the DC excitation voltage and the sixth parameter into the third set of equations to obtain a sixth set of parametric equations; The second insulation resistance value is determined according to the fifth parametric equation group and the sixth parametric equation group, wherein the third isolation resistor, the first sampling resistor, the first switching resistor, and the first insulation resistor constitute a seventh loop; the fifth isolation resistor, the second sampling resistor, the second switching resistor, and the second insulation resistor constitute an eighth loop; the first insulation resistor, the second insulation resistor, and the fourth isolation resistor constitute a ninth loop; the second circuit parameters also include the fifth parameter and the sixth parameter; the first switch state includes the first switching switch being disconnected and the second switching switch being closed; and the second switch state includes the first switching switch being closed and the second switching switch being disconnected.

9. The method for monitoring the insulation resistance of a through bolt according to claim 6, wherein, When there is a two-point grounding fault in the through screw, determining the two grounding points in the through screw includes: Determine the third isolation resistor value, the fourth isolation resistor value, and the fifth isolation resistor value according to the second insulation resistance value; The position of the second assumed grounding point relative to the DC excitation voltage is determined based on the relationship between the sum of the resistance value of the third isolation resistor and the fourth isolation resistor and the total resistance value of the isolation resistor, and / or based on the relationship between the resistance value of the fifth isolation resistor and the total resistance value of the isolation resistor, wherein the sum of the resistance value of the third isolation resistor, the resistance value of the fourth isolation resistor and the resistance value of the fifth isolation resistor is equal to the total resistance value of the isolation resistor.

10. The method for monitoring the insulation resistance of a through bolt according to claim 1, characterized in that, The determining whether there is a two-point grounding fault of the through screw according to the second insulation resistance value includes: When the value of the second insulation resistance is less than the second preset insulation resistance value, it is determined that there is a two-point grounding fault of the through-bolt; When the value of the second insulation resistance is greater than or equal to the second preset insulation resistance value, it is determined that there is no two-point grounding fault of the through-bolt, and there is a one-point grounding fault of the through-bolt.

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