CN219417640U - Insulation monitoring device with capacitance detection function - Google Patents
Insulation monitoring device with capacitance detection function Download PDFInfo
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- CN219417640U CN219417640U CN202320115102.2U CN202320115102U CN219417640U CN 219417640 U CN219417640 U CN 219417640U CN 202320115102 U CN202320115102 U CN 202320115102U CN 219417640 U CN219417640 U CN 219417640U
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Abstract
The application discloses insulating monitoring device that has electric capacity detection function concurrently. The insulation monitoring device includes: the bridge circuit module and the bridge circuit module are respectively connected with positive and negative voltages of a bus of the direct current system; the alternating current transformers are respectively and fixedly arranged on each branch bus of the direct current power supply system; the ultra-low frequency alternating current transformer passes through the positive and negative voltage lead-in wires of the bus of the direct current system; the signal acquisition module is respectively and electrically connected with the data output ends of the alternating current transformers at the multipath data input ends; the data input end of the ultralow frequency signal acquisition module is electrically connected with the data output end of the ultralow frequency alternating current transformer; and the main MCU circuit module is in bidirectional communication connection with the signal acquisition module and the ultralow frequency signal acquisition module. According to the method and the device, insulation monitoring can be carried out, meanwhile, the change of the ground capacitance of the direct current power supply system is monitored, and relay protection misoperation or refusal operation caused by the ground capacitance of the system when the insulation of the system is reduced is prevented.
Description
Technical Field
The application relates to the technical field of direct current power supply systems, in particular to an insulation monitoring device with a capacitance detection function.
Background
The direct current system provides a reliable direct current power supply for control, signal, protection, automatic device, accident lighting and the like in a transformer substation, and also provides a reliable operation power supply for operation. The reliability of the direct current system plays a vital role in the safe operation of the transformer substation and is the guarantee of the safe operation of the transformer substation.
The capacitance to ground of the direct current system is actually a new problem in the process of integrating all loads in the system, and cannot be controlled in advance. With the continuous improvement of the voltage level of the power grid, the continuous increase of the capacity of the power station and the expansion of the area of the power station, the distributed capacitance of the lead to the ground and the anti-interference capacitance of the high-frequency switch to the ground are also continuously increased. The system ground capacitance is also increased gradually, and the system ground capacitance comprises a cable ground distributed capacitance, a device circuit ground capacitance and a communication power circuit ground capacitance; the capacitor can improve the common mode interference of the direct current bus, and the safe operation of the direct current system is not affected in an ideal state, so that the capacitor is often ignored by people.
An error area exists in the existing national standard and the existing electric power industry standard, and single-point grounding cannot cause misoperation of protection equipment. However, in practice, in a large-scale transformer station, when the capacitance to ground of the dc system increases to a certain value and the voltage to ground of the dc negative bus is higher than the relay operating voltage, a malfunction of the relay may be caused by grounding one point of the dc system.
Fig. 1 is a schematic diagram of a relay malfunction caused by a point ground under the condition that a large capacitance exists in a dc system: r1 and R2 are sampling resistors in the insulation monitor, and R+ and R-equivalent buses are positive and negative total ground resistors, and C+ and C-equivalent buses are positive and negative total system capacitances to ground. When the point A of the system is grounded, C+ charges the relay and C-discharges the relay, at the moment, current flows through the relay, and when the voltage on the capacitor is larger than the action voltage of the relay, the relay can malfunction.
For the above reasons, the dc system monitoring device analyzes the dc system insulation degradation, and monitors the system insulation degradation in consideration of various insulation degradation conditions, but does not consider detecting the capacitance of the dc system to ground capacitance or a special device for detecting the capacitance.
Disclosure of Invention
Therefore, the application provides an insulation monitoring device with a capacitance detection function, so as to solve the problem that the existing insulation monitoring equipment of the direct current system in the prior art does not consider detecting the capacitance to ground of the direct current system.
In order to achieve the above object, the present application provides the following technical solutions:
an insulation monitoring device with capacitance detection function, comprising:
the bridge-changing circuit module is connected with positive and negative voltages of a direct current system bus;
the bridge circuit module is connected with positive and negative voltages of the bus of the direct current system;
the alternating current transformers are respectively and fixedly arranged on each branch bus of the direct current power supply system;
the ultra-low frequency alternating current transformer passes through a positive voltage lead-in wire of a bus of the direct current system;
the signal acquisition module is respectively and electrically connected with the data output ends of the alternating current transformers at the multipath data input ends; the signal acquisition module is used for calculating the capacitance to ground and the resistance to ground of each branch bus of the direct current system according to the current signals acquired by the plurality of alternating current transformers;
the data input end of the ultralow frequency signal acquisition module is electrically connected with the data output end of the ultralow frequency alternating current transformer; the ultralow frequency signal acquisition module is used for calculating the total capacitance to ground and the total resistance to ground of the direct current system according to the current signals acquired by the ultralow frequency alternating current transformer;
the main MCU circuit module is in bidirectional communication connection with the signal acquisition module and the ultralow frequency signal acquisition module; the first control signal output end of the main MCU circuit module is electrically connected with the control signal input end of the bridge circuit module, and the second control signal output end of the main MCU circuit module is electrically connected with the control signal input end of the bridge circuit module.
Optionally, the bridge circuit module is specifically an unbalanced bridge circuit, and the unbalanced bridge circuit includes:
the first unbalanced bridge comprises a resistor R1, a resistor R2 and a switch K1, wherein one end of the resistor R1 is connected with a positive voltage lead-in wire of a direct current system bus, the other end of the resistor R1 is grounded through the resistor R2, and the other end of the resistor R1 is grounded through the switch K1;
the second unbalanced bridge comprises a resistor R3, a resistor R4 and a switch K2, wherein one end of the resistor R3 is connected with a negative voltage lead-in wire of a direct current system bus, the other end of the resistor R3 is grounded through the resistor R4, and the other end of the resistor R3 is grounded through the switch K2.
Further alternatively, the resistor R1 is the same as the resistor R3, and the resistor R2 is the same as the resistor R4.
Optionally, the signal acquisition module includes:
the signal selection channel is provided with multiple paths of data input ends electrically connected with the data output ends of the alternating current transformers;
the data input end of the first MCU is electrically connected with the data output end of the signal selection channel; the first MCU is in bidirectional communication connection with the main MCU circuit module.
Optionally, the ultralow frequency signal acquisition module comprises a low-pass filter circuit, an amplifying circuit, an analog-to-digital conversion chip and a second MCU;
the data input end of the low-pass filter circuit is electrically connected with the data output end of the ultralow frequency alternating current transformer, and the data output end of the low-pass filter circuit is electrically connected with the data input end of the second MCU sequentially through the amplifying circuit and the analog-to-digital conversion chip; the second MCU is in bidirectional communication connection with the main MCU circuit module.
Further alternatively, the amplifying circuit comprises a program-controlled pre-amplifying circuit, a secondary amplifying circuit and a tertiary amplifying circuit which are sequentially connected, and a control signal input end of the program-controlled pre-amplifying circuit is electrically connected with a control signal output end of the second MCU.
Optionally, the main MCU circuit module is connected with the signal acquisition module and the ultralow frequency signal acquisition module through serial ports in a two-way communication manner.
Compared with the prior art, the application has the following beneficial effects:
the embodiment of the application provides a new hardware architecture of a direct current system insulation detection device, which is based on the existing insulation monitoring device, and an ultralow frequency alternating current transformer and an ultralow frequency signal acquisition module are added; based on the hardware architecture provided by the application, after a low-frequency alternating current signal is sent to a bus through a bridge-changing circuit module, fault current signals on all branches can be sensed by utilizing alternating current transformers arranged on all branches, so that a branch capacitor and a branch grounding resistor can be obtained by a signal acquisition module in combination with a measurement method known by a person in the art; similarly, after the bridge circuit module is switched and cut at a constant frequency to enable the positive and negative voltages to the ground of the bus to swing at the constant frequency, an ultralow frequency alternating current transformer passing through the positive and negative voltage lead-in wires of the bus can be used for sensing current signals of the same frequency as the switching of the bridge on the bus, so that the ultralow frequency signal acquisition module can obtain a system capacitor and a system grounding resistance by combining a measuring method known by a person in the art; the insulation monitoring device provided by the application has the functions of capacitance detection and insulation detection, the function of detecting the system capacitance is increased on the basis of the existing DC system insulation monitoring device, the change of the ground capacitance of the DC power supply system can be monitored while insulation monitoring is carried out, and the system ground capacitance is prevented from causing relay protection malfunction or refusal when the system insulation is lowered.
Drawings
For a more visual illustration of the prior art and the present application, several exemplary drawings are presented below. It should be understood that the specific shape and configuration shown in the drawings should not be considered in general as limiting upon the practice of the present application; for example, based on the technical concepts and exemplary drawings disclosed herein, those skilled in the art have the ability to easily make conventional adjustments or further optimizations for the add/subtract/assign division, specific shapes, positional relationships, connection modes, dimensional scaling relationships, etc. of certain units (components).
FIG. 1 is a schematic diagram of a point ground induced relay malfunction;
fig. 2 is a schematic block diagram of an insulation monitoring device with a capacitance detection function according to an embodiment of the present application;
fig. 3 is a schematic diagram of detection principles of a branch capacitor and a branch ground resistor in an embodiment of the present application;
FIG. 4 is a schematic diagram of a fault current structure in an embodiment of the present application;
FIG. 5 is a schematic diagram of the detection principle of the system capacitance and the system ground resistance in the embodiment of the present application;
FIG. 6 is a schematic diagram of a bridge circuit module according to an embodiment of the present disclosure;
fig. 7 is a schematic diagram of a composition structure of an ultralow frequency signal acquisition module in an embodiment of the present application;
fig. 8 is a schematic diagram of a composition structure of a signal acquisition module in an embodiment of the present application.
Reference numerals illustrate:
1. a bridge switching circuit module; 2. a bridge circuit module; 3. an alternating current transformer; 4. an ultra-low frequency alternating current transformer; 5. a signal acquisition module; 6. the ultra-low frequency signal acquisition module; 61. a low pass filter circuit; 62. an analog-to-digital conversion chip; 63. a second MCU; 64. a program-controlled pre-amplification circuit; 65. a second-stage amplifying circuit; 66. a three-stage amplifying circuit; 7. and the main MCU circuit module.
Detailed Description
The present application is further described in detail below with reference to the attached drawings.
In the description of the present application: unless otherwise indicated, the meaning of "a plurality" is two or more. The terms "first," "second," "third," and the like in this application are intended to distinguish between the referenced objects without a special meaning in terms of technical connotation (e.g., should not be construed as emphasis on degree or order of importance, etc.). The expressions "comprising", "including", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).
The terms such as "upper", "lower", "left", "right", "middle", and the like, as referred to in this application, are generally used for convenience in visual understanding with reference to the drawings, and are not intended to be an absolute limitation of the positional relationship in actual products. Such changes in relative positional relationship are considered to be within the scope of the present description without departing from the technical concepts disclosed herein.
The capacitance detection of the direct current system is divided into two parts: firstly, the detection of the total capacitance of the system to the ground (the system capacitance for short) and secondly, the detection of the capacitance of the branch (the branch bus) to the ground comprise the distributed capacitance to the ground and the capacitance of equipment carried by the branch (the branch capacitance for short). Similarly, dc system insulation monitoring is also divided into two parts: firstly, the detection of the grounding resistance of the bus of the direct current system (short for system grounding resistance) and secondly, the detection of the grounding resistance of a branch (branch bus) (short for branch resistance).
In this embodiment of the present application, as shown in fig. 2, an insulation monitoring device with a capacitance detection function is provided, which includes:
the bridge-changing circuit module 1 is connected with positive and negative voltages of a bus of the direct current system and is used for generating a low-frequency alternating current detection signal on the bus of the direct current power supply system;
the bridge circuit module 2 is connected with positive and negative voltages of the bus of the direct current system and is used for changing the insulation state of the bus of the direct current system so that the positive and negative voltages to the ground of the bus swing at a constant frequency;
a plurality of alternating Current Transformers (CT) 3 which are respectively and fixedly arranged on each branch bus of the direct current power supply system and are used for sensing fault current on each branch bus;
an ultralow frequency alternating current transformer (ultralow frequency CT for short) 4 which passes through the positive and negative voltage lead-in wires of the busbar of the direct current system and is used for inducing current signals on the busbar;
the signal acquisition module 5 is respectively and electrically connected with the data output ends of the alternating current transformers 3 at the multipath data input ends; the signal acquisition module 5 is used for calculating the capacitance to ground and the resistance to ground of each branch bus of the direct current system according to the current signals acquired by the plurality of alternating current transformers 3;
the data input end of the ultralow frequency signal acquisition module 6 is electrically connected with the data output end of the ultralow frequency alternating current transformer 4; the ultralow frequency signal acquisition module 6 is used for calculating the total capacitance to ground and the total resistance to ground of the direct current system according to the current signals acquired by the ultralow frequency alternating current transformer 4;
the main MCU circuit module 7 is in bidirectional communication connection with the signal acquisition module 5 and the ultralow frequency signal acquisition module 6; the first control signal output end of the main MCU circuit module 7 is electrically connected with the control signal input end of the bridge circuit module 1, and the second control signal output end of the main MCU circuit module 7 is electrically connected with the control signal input end of the bridge circuit module 2.
The existing insulation monitoring device comprises a monitoring device host, a plurality of alternating current transformers 3 and a signal acquisition module 5, wherein the monitoring device host comprises a variable bridge circuit module 1, a bridge circuit module 2 and a main MCU circuit module 7. In this application, the bridge circuit module 1, the bridge circuit module 2, the ultralow frequency ac current transformer 4, the ultralow frequency signal acquisition module 6 and the main MCU circuit module 7 form a monitoring device host. In other words, the ultra-low frequency alternating current transformer 4 and the ultra-low frequency signal acquisition module 6 are added on the basis of the hardware architecture of the monitoring device host on the basis of the existing insulation monitoring device.
Based on the hardware architecture provided by the application, the method can be used for detecting the ground capacitance of the branch and the ground resistance of the branch in combination with the existing measurement method, and can be used for detecting the system capacitance and the bus ground resistance of the direct current system. As an alternative configuration, specifically:
1. detection of branch capacitance and branch ground resistance
The existing direct current system insulation detection equipment generally adopts the following two methods when detecting the branch resistance: direct current leakage current detection method and low frequency alternating current signal detection method.
The detection of the branch capacitance and the branch grounding resistance is realized by adopting a low-frequency alternating current signal detection method: an ac current transformer 3 (CT) is mounted on each branch bus, the bridge switching circuit module 1 of the host machine can send low-frequency ac signals to the bus, the CT senses fault current signals (fault current flows through the branch with insulation drop and distributed capacitance to ground and CT on the branch), as shown in fig. 3, the signal source generates current I on the nth branch n 。
As shown in FIG. 4, the fault current signal induced by CT in the nth branch and having the same frequency as the signal source is the vector sum I of the currents of the resistor and the capacitor, and the voltage signal generates an in-phase current I on the grounding resistor R Generating a current I with a phase advance of 90 degrees on a capacitor C The real and imaginary parts of I can represent the ground resistance current and the capacitance current. As the common knowledge of the person skilled in the art, the signal acquisition module 5 takes the phase of the voltage signal 0 provided by the bridge-changing circuit module 1 as the starting time of the FFT window, and can calculate the phase of the voltage signalMeasuring fault current phase theta of a branch circuit; by I R Calculation of I by the equation =icosθ R And then the grounding resistance of the branch circuit can be calculated through ohm law according to the voltage of the low-frequency alternating current signal sent by the bridge-changing circuit module 1.
The detection principle and circuit described above may also be used to detect the branch capacitance as is known to those skilled in the art:
I C ＝Isinθ＝U/X C (1)
X C ＝1/(ωC)＝1/(2πfC)(2)
C＝Isinθ/(2Uπf)(3)
substituting the formula (2) into the formula (1) to obtain the formula (3) after deduction, and the signal acquisition module 5 can calculate the branch capacitance through the formula (3) so as to realize the purpose of detecting the branch capacitance. Wherein X is C As capacitive reactance, U is the voltage of the low-frequency alternating current signal sent by the variable bridge circuit module 1 at two ends of the capacitor, and is a known item; f is the frequency of the low frequency ac signal and is a known term.
2. Detection of system capacitance and system ground resistance
The insulation monitoring host of the direct current system generally calculates the positive and negative resistance values of the bus through the switching of the bridge circuit module 2, as a common technical means in the field, the bridge circuit module 2 is switched and cut at a constant frequency, so that the positive and negative voltages of the bus swing at a constant frequency, similar to the detection principle of the ground capacitance of a branch, as shown in fig. 5, an ultralow frequency CT4 is additionally arranged in the host, the ultralow frequency CT4 passes through the positive and negative voltage lead-in wires of the bus, and can sense the current signals with the same frequency as the switching of the bridge on the bus, and the current signals comprise the current I of the total ground resistance of the system RZ And system capacitance current I CZ . The current signal induced by the ultralow frequency CT4 passes through the ultralow frequency signal acquisition module 6, and I can be obtained according to the formulas involved in the detection of the branch capacitance and the branch grounding resistance RZ 、I CZ According to I RZ 、I CZ The bus bar system ground resistance and capacitance can be calculated. In fig. 5, R is equivalent system ground resistance, C is equivalent system capacitance to ground.
The calculation method and formula related to the application belong to common knowledge or common technical means of the person skilled in the art, and reference can be made to [0073] in the "high-resistance ground fault positioning device and method for DC system" disclosed in China patent document CN114879077A and "on-line measurement method for system capacitance of DC system" disclosed in journal of modern electronic technology "(2015, 3, 1, etc.), so that the application does not relate to improvement on the method.
Specifically, the bridge circuit module 2 may be an unbalanced bridge circuit, as shown in fig. 6, including:
the first unbalanced bridge comprises a resistor R1, a resistor R2 and a switch K1, wherein one end of the resistor R1 is connected with a positive voltage lead-in wire of a direct current system bus, the other end of the resistor R1 is grounded through the resistor R2, and the other end of the resistor R1 is grounded through the switch K1;
the second unbalanced bridge comprises a resistor R3, a resistor R4 and a switch K2, wherein one end of the resistor R3 is connected with a negative voltage lead-in wire of a direct current system bus, the other end of the resistor R3 is grounded through the resistor R4, and the other end of the resistor R3 is grounded through the switch K2.
The resistor R1 is the same as the resistor R3, and the resistor R2 is the same as the resistor R4.
As a common general knowledge and a conventional technical means for a person skilled in the art, the positive and negative ground resistance values of the dc system bus can be calculated by switching the two unbalanced bridges. R1, R2, R3, R4, K1 and K2 form two groups of unbalanced bridges, and all the earth resistances at the positive end and the negative end of the R+ and R-equivalent bus are connected in parallel. Through controlling the states of K1 and K2, two groups of unbalanced bridges are alternately connected into a bus, so that positive and negative voltages to the ground of the bus swing to obtain two groups of voltages to the ground, and positive and negative resistances to the ground can be calculated, and specifically:
k1 is closed and K2 is opened to form an unbalanced bridge 1 which is connected with a bus to measure positive and negative voltages U1+ and U1-; k1 is opened and K2 is closed, an unbalanced bridge 2 is formed and connected with a bus, and the positive and negative voltages U2+ and U2-to-ground are measured, and R+ and R-can be calculated by two equations.
Specifically, as shown in fig. 7, the ultra-low frequency signal acquisition module 6 includes a low-pass filter circuit 61, an amplifying circuit, an analog-to-digital (a/D) conversion chip 62, and a second MCU63; the data input end of the low-pass filter circuit 61 is electrically connected with the data output end of the ultralow frequency alternating current transformer 4, and the data output end of the low-pass filter circuit 61 is electrically connected with the data input end of the second MCU63 sequentially through the amplifying circuit and the analog-digital conversion chip 62; the second MCU63 is connected in bidirectional communication with the main MCU circuit module 7.
The amplifying circuit may specifically be a three-stage amplifying circuit, that is, the amplifying circuit may include a programmable pre-amplifying circuit 64, a two-stage amplifying circuit 65, and a three-stage amplifying circuit 66, which are sequentially connected. In addition, the control signal input end of the programmable preamplifier circuit 64 is electrically connected to the control signal output end of the second MCU63, so that the second MCU63 can adjust the gain of the programmable preamplifier circuit 64.
During the period that the host switches the two groups of unbalanced bridges, the host needs to acquire voltage data after the positive and negative voltages are stabilized, and the frequency of switching the two groups of bridges cannot be as high as the frequency of a bridge-changing signal for detecting the branch resistors (the current bridge-changing signal frequency for detecting the branch resistors is usually below 5 Hz).
Assuming that the time for which the first unbalanced bridge and the second unbalanced bridge are put into the system is 4 seconds, the period of the positive and negative voltage swing to the ground of the bus is 8 seconds, and the swing frequency is f=1/t=1/8=0.125 Hz. CT is much weaker in sensing capability for 0.125Hz signals than for branch-circuit variable-bridge signals. The micro current signal induced by CT needs to be amplified in multiple stages after low-pass filtering to obtain a usable current signal, the current signal is sent to the second MCU63 after A/D conversion, the second MCU63 calculates the current I, then the phase angle theta of the I is calculated according to the synchronous signal sent by the main MCU circuit module 7, and the system capacitance C can be calculated by substituting the phase angle theta into the formula (3).
Further, the signal acquisition module 5 includes:
the signal selection channel 51, the multi-path data input end of which is electrically connected with the data output ends of the plurality of alternating current transformers 3;
the first MCU52, the data input end of which is electrically connected to the data output end of the signal selection channel 51; the first MCU is in two-way communication connection with the main MCU circuit module 7.
After gating one of the ac current transformers 3, the signal selection channel 51, according to the above detection principle, the first MCU52 can calculate the capacitance to ground and the resistance to ground of the current branch according to the current signal collected by the ac current transformer 3
Further, the main MCU circuit module 7 is connected with the signal acquisition module 5 and the ultralow frequency signal acquisition module 6 through serial ports in a two-way communication mode.
The embodiment of the application provides a novel hardware architecture of an insulation detection device of a direct current system, which is based on the existing insulation monitoring device, an ultralow frequency alternating current transformer and an ultralow frequency signal acquisition module are added, and the detection function of a system capacitor is added on the basis of the existing insulation monitoring device of the direct current system. Based on the hardware architecture provided by the application, after a low-frequency alternating current signal is sent to a bus through a bridge-changing circuit module, fault current signals on all branches can be sensed by utilizing alternating current transformers arranged on all branches, so that a branch capacitor and a branch grounding resistor can be obtained by a signal acquisition module in combination with a measurement method known by a person in the art; similarly, after the bridge circuit module is switched and cut at a constant frequency, the positive and negative voltages to the ground of the bus are swung at the constant frequency, the ultra-low frequency alternating current transformer passing through the positive and negative voltage lead-in wires of the bus can be used for sensing the current signals of the same frequency as the switching of the bridge on the bus, so that the ultra-low frequency signal acquisition module can obtain the system capacitance and the system grounding resistance by combining with a measuring method known by a person in the field.
Therefore, the insulation monitoring device provided by the application has the functions of capacitance detection and insulation detection, can monitor the change of the ground capacitance of the direct current power supply system when insulation monitoring is carried out, and prevents the malfunction or refusal of relay protection caused by the ground capacitance of the system when the insulation of the system is reduced. The system capacitance monitoring method and the system capacitance monitoring device can realize real-time monitoring of the system capacitance, prevent system faults caused by the system capacitance, and can also realize detection of the branch capacitance. The method provides a feasible solution for relay protection misoperation or refusal operation caused by insulation drop under the condition that a larger capacitance to ground exists in the direct current system.
Any combination of the technical features of the above embodiments may be performed (as long as there is no contradiction between the combination of the technical features), and for brevity of description, all of the possible combinations of the technical features of the above embodiments are not described; these examples, which are not explicitly written, should also be considered as being within the scope of the present description.
The foregoing has outlined and detailed description of the present application in terms of the general description and embodiments. It should be appreciated that numerous conventional modifications and further innovations may be made to these specific embodiments, based on the technical concepts of the present application; but such conventional modifications and further innovations may be made without departing from the technical spirit of the present application, and such conventional modifications and further innovations are also intended to fall within the scope of the claims of the present application.
Claims (7)
1. An insulation monitoring device with capacitance detection function, comprising:
the bridge-changing circuit module is connected with positive and negative voltages of a direct current system bus;
the bridge circuit module is connected with positive and negative voltages of the bus of the direct current system;
the alternating current transformers are respectively and fixedly arranged on each branch bus of the direct current power supply system;
the ultra-low frequency alternating current transformer passes through a positive voltage lead-in wire of a bus of the direct current system;
the signal acquisition module is respectively and electrically connected with the data output ends of the alternating current transformers at the multipath data input ends; the signal acquisition module is used for calculating the capacitance to ground and the resistance to ground of each branch bus of the direct current system according to the current signals acquired by the plurality of alternating current transformers;
the data input end of the ultralow frequency signal acquisition module is electrically connected with the data output end of the ultralow frequency alternating current transformer; the ultralow frequency signal acquisition module is used for calculating the total capacitance to ground and the total resistance to ground of the direct current system according to the current signals acquired by the ultralow frequency alternating current transformer;
the main MCU circuit module is in bidirectional communication connection with the signal acquisition module and the ultralow frequency signal acquisition module; the first control signal output end of the main MCU circuit module is electrically connected with the control signal input end of the bridge circuit module, and the second control signal output end of the main MCU circuit module is electrically connected with the control signal input end of the bridge circuit module.
2. The insulation monitoring device with capacitance detection function as claimed in claim 1, wherein the bridge circuit module is specifically an unbalanced bridge circuit, and the unbalanced bridge circuit comprises:
the first unbalanced bridge comprises a resistor R1, a resistor R2 and a switch K1, wherein one end of the resistor R1 is connected with a positive voltage lead-in wire of a direct current system bus, the other end of the resistor R1 is grounded through the resistor R2, and the other end of the resistor R1 is grounded through the switch K1;
the second unbalanced bridge comprises a resistor R3, a resistor R4 and a switch K2, wherein one end of the resistor R3 is connected with a negative voltage lead-in wire of a direct current system bus, the other end of the resistor R3 is grounded through the resistor R4, and the other end of the resistor R3 is grounded through the switch K2.
3. The insulation monitoring device with the capacitance detection function according to claim 2, wherein the resistor R1 is the same as the resistor R3, and the resistor R2 is the same as the resistor R4.
4. The insulation monitoring device with capacitance detection function as set forth in claim 1, wherein the signal acquisition module includes:
the signal selection channel is provided with multiple paths of data input ends electrically connected with the data output ends of the alternating current transformers;
the data input end of the first MCU is electrically connected with the data output end of the signal selection channel; the first MCU is in bidirectional communication connection with the main MCU circuit module.
5. The insulation monitoring device with the capacitance detection function as set forth in claim 1, wherein the ultralow frequency signal acquisition module comprises a low-pass filter circuit, an amplifying circuit, an analog-to-digital conversion chip and a second MCU;
the data input end of the low-pass filter circuit is electrically connected with the data output end of the ultralow frequency alternating current transformer, and the data output end of the low-pass filter circuit is electrically connected with the data input end of the second MCU sequentially through the amplifying circuit and the analog-to-digital conversion chip; the second MCU is in bidirectional communication connection with the main MCU circuit module.
6. The insulation monitoring device with the capacitance detection function according to claim 5, wherein the amplifying circuit comprises a program-controlled pre-amplifying circuit, a secondary amplifying circuit and a tertiary amplifying circuit which are sequentially connected, and a control signal input end of the program-controlled pre-amplifying circuit is electrically connected with a control signal output end of the second MCU.
7. The insulation monitoring device with the capacitance detection function according to claim 1, wherein the main MCU circuit module is connected with the signal acquisition module and the ultra-low frequency signal acquisition module through serial ports in a two-way communication mode.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202320115102.2U CN219417640U (en) | 2023-01-20 | 2023-01-20 | Insulation monitoring device with capacitance detection function |
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| CN202320115102.2U CN219417640U (en) | 2023-01-20 | 2023-01-20 | Insulation monitoring device with capacitance detection function |
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2023
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