A device for detecting ring network resistance

Abstract

The present invention aims to provide a device for detecting the resistance value of a ring network. The present invention comprises a central processing unit, a heteropolar ring network test resistor and a control unit, a homopolar ring network test resistor and a control unit, and two groups of busbars. The central processing unit is electrically connected to two groups of busbar voltage measurement units, two groups of busbar-to-ground voltage measurement units, two groups of balancing bridge resistances and control units, and two groups of detection bridge resistances and control units. All of the above units are symmetrically connected to the two ends of the homopolar ring network test resistor and the control unit and are connected to the two groups of busbars. The present invention is applied to the technical field of monitoring a DC power supply system.

Description

Technical Field

[0001] The present invention is applied to the technical field of direct current power supply system monitoring, and particularly relates to a device for detecting the resistance value of a ring network. Background Art

[0002] The station DC power supply system is mainly responsible for providing reliable power supply for the relay protection equipment, various monitoring devices (signals), communication equipment, and circuit breaker (switch) opening and closing control in the station. It is also related to whether the secondary protection and control signals can be opened normally. According to the power industry standard DL / T 5044-2014, important 110kV and 220kV substations should be equipped with 2 sets of batteries and interconnecting electrical appliances between the two bus sections. During normal operation, the two bus sections operate independently. Therefore, there should be no ring network operation in the two sections of the DC bus in normal operation. However, when the DC system is maintained or modified, the two bus sections are electrically connected due to construction, resulting in a ring network operation. At present, the main methods for detecting DC ring networks are: injection method, negative bus grounding method, and bus voltage adjustment method.

[0003] The injection method is an early method that injects a low-frequency signal into a section of the busbar and monitors the branch of another section of the busbar to see if there is a signal to determine whether there is a ring network. The low-frequency signal of the injection method is affected by the distributed capacitance of the power supply network between the system busbar and the load, and is easily attenuated and misjudged.

[0004] The negative bus grounding method is to ground the negative pole of one section of the bus (to ensure system safety). At this time, the voltage of this section of the bus to the ground changes. By observing whether the voltage of the other section of the bus to the ground changes accordingly, it is judged whether there is a ring network in the DC system. The negative bus grounding method affects the insulation balance of the system, triggers system alarms, and interferes with the judgment of operation and maintenance; due to artificial grounding points, the system may be grounded at multiple points, resulting in the risk of protection refusal or malfunction.

[0005] The bus voltage adjustment method adjusts the voltage of one section of the bus to change its voltage to ground, and then determines whether there is a ring network in the DC system by observing whether the voltage of the other section of the bus to ground changes accordingly. The bus voltage adjustment method may affect the load or equipment of the bus because the bus voltage change may affect the load or equipment of the bus. Moreover, this method is only intuitive for the same-pole ring network, and may not be obvious for the different-pole ring network.

[0006] The above method can only simply detect whether the bus has a ring network state, but cannot accurately detect the ring network resistance. Therefore, it is necessary to provide a device that can periodically or manually determine the type of bus ring network fault and accurately detect the ring network resistance without affecting the system insulation safety. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a device that can periodically or manually determine the type of bus ring network fault and accurately detect the ring network resistance without affecting the system insulation safety.

[0008] The technical solution adopted by the present invention is: the present invention includes a central processing unit, a heteropolar ring network test resistor and control unit, a homopolar ring network test resistor and control unit and two groups of busbars, the heteropolar ring network test resistor and control unit include a first resistor R+- and a second resistor R-+, the homopolar ring network test resistor and control unit include a third resistor R++ and a fourth resistor R--, the two groups of busbars include 1M+, 1M-, 2M+ and 2M-, the first resistor R+- is connected between the 1M+ and the 2M-, the second resistor R-+ is connected between the 1M- and the 2M+, the third resistor R++ is connected between the 1M+ and the 2M+, the fourth resistor R- is connected between the 1M- and the 2M-, and the central processing unit is electrically connected with Two groups of bus voltage measurement units, two groups of bus-to-ground voltage measurement units, two groups of balancing bridge resistance and control units, and two groups of detection bridge resistance and control units. All of the above units are symmetrically connected to the two ends of the same-pole ring network test resistance and control unit and are connected to the two groups of busbars. The two groups of balancing bridge resistance and control units include a fifth resistor RP1+, a sixth resistor RP1-, a seventh resistor RP2+, and an eighth resistor RP2-. The two groups of detection bridge resistance and control units include a ninth resistor RJ1+, a tenth resistor RJ1-, an eleventh resistor RJ2+, a twelfth resistor RJ2-, a first switch Kj1-, and a second switch Kj2-. The tenth resistor RJ1- is connected in series with the first switch Kj1-, and the twelfth resistor RJ2- is connected in series with the second switch Kj2-.

[0009] It can be seen from the above scheme that the two groups of bus voltage measurement units are used to collect the voltages of the two groups of busbars, and the two groups of busbar-to-ground voltage measurement units are used to collect the positive-to-ground voltage and negative-to-ground voltage of the two groups of busbars, and the central processing unit performs calculations and processing based on the above voltages; the central processing unit issues control instructions to the two groups of balancing bridge resistors and control units according to data processing requirements, so that the busbar switches the balancing bridge resistor to the ground; the central processing unit issues control instructions to the two groups of detection bridge resistors and control units according to data processing requirements, so that the busbar switches the detection bridge resistor to the ground; the central processing unit issues control instructions to the heteropolar ring network test resistors and control units according to data processing requirements, so that the heteropolar ring network test resistors are switched between the two groups of busbars; the central processing unit issues control instructions to the homopolar ring network test resistors and control units according to data processing requirements, so that the homopolar ring network test resistors are switched between the two groups of busbars.

[0010] The voltage division values obtained by the two groups of bus voltage measurement units are Um1 and Um2 respectively, and the voltage division values obtained by the two groups of bus-to-ground voltage measurement units are U1+, U1-, U2+ and U2- respectively. The rated voltage of the DC system is Un. When the system is operating normally, the two groups of balance bridge resistors and control units are controlled by the central processing unit to turn on Kp1+, Kp1-, Kpe1, Kp2+, Kp2-, and Kpe2 respectively;

[0011] I. When the voltage difference between the two groups of bus-to-ground voltage measurement units is greater than 10%Un, that is, the difference between U1+ and U1-, and the difference between U2+ and U2-:

[0012] 1. If U1+ < U1- and U2+ > U2-, at this time, the tenth resistor RJ1- is controlled by the central processing unit to turn on the first switch Kj1-. If the change in the voltage difference between U2+ and U2-对地 voltage is greater than a fixed value, it can be determined that the positive pole of one group of buses and the negative pole of another group of buses are in a different-pole loop network. The calculation formula for the loop resistance is:

[0013]

[0014] 2. If U1+ > U1- and U2+ < U2-, at this time, the twelfth resistor RJ2- is controlled by the central processing unit to turn on the second switch Kj2-. If the change in the voltage difference between U1+ and U1-对地 voltage is greater than a fixed value, it can be determined that the negative pole of one group of buses and the positive pole of another group of buses are in a different-pole loop network. The calculation formula for the loop resistance is:

[0015]

[0016] II. When the system is operating normally, if the timing detection period arrives or a manual trigger instruction is given, at this time, the tenth resistor RJ1- is controlled by the central processing unit to turn on the first switch Kj1-, and the twelfth resistor RJ2- is controlled by the central processing unit to turn on the second switch Kj2-. At this time:

[0017] 1. The tenth resistor RJ1- is controlled by the central processing unit to turn on the first switch Kj1-. If U1+ > U1- and U2+ > U2-, and the change in the voltage difference between U2+ and U2- is greater than a fixed value is the judgment condition A, the tenth resistor RJ1- is controlled by the central processing unit to turn off the first switch Kj1-;

[0018] 2. The twelfth resistor RJ2- is controlled by the central processing unit to turn on the second switch Kj2-. If U2+ > U2- and U1+ > U1-, and the change in the voltage difference between U1+ and U1- is greater than a fixed value is the judgment condition B, the twelfth resistor RJ2- is controlled by the central processing unit to turn off the second switch Kj2-;

[0019] If both conditions A and B are met, it can be judged as a homopolar ring network;

[0020] According to the current equality principle:

[0021]

[0022] The calculation formula of the ring network resistance can be derived:

[0023]

[0024] Wherein: is the voltage difference to ground when Kj- is closed, is the differential current flowing through PE when Kj- is closed, and the device for detecting the ring network resistance can determine the type of bus ring network fault periodically or manually and instantly without affecting the insulation safety of the system, and accurately detect the ring network resistance.

[0025] A preferred solution is that the device for detecting the ring network resistance value further includes a data display unit, the data display unit is electrically connected to the central processing unit, and the data display unit displays measurement data and test results.

[0026] It can be seen from the above scheme that the central processing unit issues a data display instruction to the data display unit according to the processing result, and the data display unit displays the measurement data and test results through the liquid crystal screen.

[0027] A preferred solution is that the device for detecting the ring network resistance value also includes a data communication unit, the data communication unit is electrically connected to the central processing unit, and the data communication unit sends out measurement data and test results according to instructions of the central processing unit.

[0028] It can be seen from the above scheme that the central processing unit sends measurement data and test results to the data communication unit according to requirements, and the data communication unit sends the measurement data and test results to other devices through communication.

[0029] A preferred solution is that the two groups of bus voltage measurement units include a first group of bus voltage measurement units and a second group of bus voltage measurement units, the first group of bus voltage measurement units are connected to the 1M+ and the 1M-, and the second group of bus voltage measurement units are connected to the 2M+ and the 2M-.

[0030] It can be seen from the above scheme that the two groups of bus voltage measurement units are connected between the two groups of busbars by multiple resistors in series voltage division, and the voltage division value of the terminal resistor is sent to the central processing unit for collection through the signal conditioning unit, and the signal conditioning unit includes a first operation follower circuit, a first secondary voltage division circuit, a first linear optocoupler isolation circuit, a first operation amplifier circuit and a first filter circuit. The two groups of busbars include a first group of busbars and a second group of busbars, the first group of busbars are the 1M+ and the 1M-, the second group of busbars are the 2M+ and the 2M-, the first group of busbar voltage measurement units are connected to the 1M+ and the 1M-, and measure the voltage of the first group of busbars; the second group of busbar voltage measurement units are connected to the 2M+ and the 2M-, and measure the voltage of the second group of busbars.

[0031] A preferred solution is that the center points of the series resistors of the two groups of the busbar-to-ground voltage measurement units are connected to PE, and the PE is an insulated protective ground. The two groups of the busbar-to-ground voltage measurement units include a first group of busbar positive and negative pole-to-ground voltage measurement units and a second group of busbar positive and negative pole-to-ground voltage measurement units. The first group of busbar positive and negative pole-to-ground voltage measurement units are connected to the 1M+, the 1M- and the PE, and the second group of busbar positive and negative pole-to-ground voltage measurement units are connected to the 2M+, the 2M- and the PE.

[0032] It can be seen from the above scheme that the two groups of busbar-to-ground voltage measurement units are connected between the two groups of busbar positive and negative poles through multiple resistor series voltage division methods, the center point of the series resistor is connected to the PE, and the voltage division value of the terminal resistor is sent to the central processing unit for collection through the signal conditioning unit, and the signal conditioning unit includes a second operational follower circuit, a second secondary voltage division circuit, a second linear optocoupler isolation circuit, a second operational amplifier circuit and a second filter circuit. The first group of busbar positive and negative pole-to-ground voltage measurement units are connected to the 1M+, the 1M- and the PE to measure the positive pole-to-ground voltage and the busbar negative pole-to-ground voltage of the first group of buses; the second group of busbar positive and negative pole-to-ground voltage measurement units are connected to the 2M+, the 2M- and the PE to measure the positive pole-to-ground voltage and the busbar negative pole-to-ground voltage of the second group of buses.

[0033] A preferred solution is that the two groups of balanced bridge resistors and control units include a first group of balanced bridge resistors and control units and a second group of balanced bridge resistors and control units, the first group of balanced bridge resistors and control units are connected to the 1M+, the 1M- and the PE, and the second group of balanced bridge resistors and control units are connected to the 2M+, the 2M- and the PE.

[0034] It can be seen from the above scheme that there are two groups of balancing bridge resistors and a control unit. This unit includes two groups of balancing bridge resistors with equal resistance values. Each group uses at least one resistor to be connected between the positive pole of the bus and the control switch, and between the negative pole of the bus and the control switch. The other ends of the two control switches are connected in parallel to the grounding switch, and the other end of the grounding switch is connected to PE (insulated protection ground). The first group of balancing bridge resistors and a control unit are connected to the first section of the DC system bus 1M+, 1M- and PE (insulated protection ground), and the central processing unit controls whether the first section of the DC bus is put into the balancing bridge and the bridge resistor is grounded; the second group of balancing bridge resistors and a control unit are connected to the second section of the DC system bus 2M+, 2M- and PE (insulated protection ground), and the central processing unit controls whether the second section of the DC bus is put into the balancing bridge and the bridge resistor is grounded.

[0035] A preferred solution is that the two groups of detection bridge resistors and control units include a first group of detection bridge resistors and control units and a second group of detection bridge resistors and control units, the first group of detection bridge resistors and control units are connected to the 1M+, the 1M- and the PE, and the second group of detection bridge resistors and control units are connected to the 2M+, the 2M- and the PE.

[0036] It can be seen from the above scheme that the two groups of detection bridge resistors and control units include two groups of detection bridge resistors with equal resistance values, and each group uses at least one resistor to be connected between the positive pole of the bus and the control switch, and between the negative pole of the bus and the control switch, respectively. The other ends of the two control switches are connected in parallel to the grounding switch, and the other end of the grounding switch is connected to the PE (insulated protection ground). The first group of detection bridge resistors and control units are connected to the 1M+, the 1M- and the PE, and the central processing unit is used to control whether the first group of busbars are put into the detection bridge and the bridge resistor is grounded; the second group of detection bridge resistors and control units are connected to the 2M+, the 2M- and the PE, and the central processing unit is used to control whether the first group of busbars are put into the detection bridge and the bridge resistor is grounded.

[0037] A preferred solution is that the heteropolar ring network test resistor and control unit includes a third switch K+- and a fourth switch K-+, the first resistor R+- is connected between the 1M+ and the third switch K+-, the other end of the third switch K+- is connected to the 2M-, the second resistor R-+ is connected between the 1M- and the fourth switch K-+, and the other end of the fourth switch K-+ is connected to the 2M+.

[0038] It can be seen from the above scheme that the heteropolar ring network test resistor and control unit include two groups of test resistors with adjustable resistance, the first resistor R+- is connected between the 1M+ and the third switch K+-, the other end of the third switch K+- is connected to the 2M-, the second resistor R-+ is connected between the 1M- and the fourth switch K-+, the other end of the fourth switch K-+ is connected to the 2M+, and the first resistor R+- is controlled by the central processing unit to be put into operation to simulate the heteropolar ring network fault scene of the first group of the bus positive pole and the second group of the bus negative pole; the test resistor R-+ and the control unit are connected to the DC system bus 1M-, 2M+, and the second resistor R-+ is controlled by the central processing unit to be put into operation to simulate the heteropolar ring network fault scene of the first group of the bus negative pole and the second group of the bus positive pole.

[0039] A preferred solution is that the homopolar ring network test resistor and control unit also includes a fifth switch K++ and a sixth switch K--, the third resistor R++ is connected between the 1M+ and the fifth switch K++, the other end of the fifth switch K++ is connected to the 2M+, the fourth resistor R-- is connected between the 1M- and the sixth switch K--, and the other end of the sixth switch K-- is connected to the 2M-.

[0040] It can be seen from the above scheme that the same-pole ring network test resistor and control unit include two groups of test resistors with adjustable resistance values, the third resistor R++ is connected between the 1M+ and the fifth switch K++, the other end of the fifth switch K++ is connected to the 2M+, the fourth resistor R-- is connected between the 1M- and the sixth switch K--, the other end of the sixth switch K-- is connected to the 2M-. The third resistor R++ is controlled by the central processing unit to simulate the first group of bus and the second group of bus positive pole same-pole ring network fault scene; the fourth resistor R-- is controlled by the central processing unit to simulate the first group of bus negative pole and the second group of bus negative pole same-pole ring network fault scene; the third resistor R++ and the fourth resistor R-- are controlled by the central processing unit to simulate the first group of bus positive pole and negative pole and the second group of bus positive pole and negative pole same-pole ring network fault scene. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is an overall block diagram of the present invention;

[0042] Figure 2 It is a circuit schematic diagram of the present invention;

[0043] Figure 3 is a circuit schematic diagram of the bus voltage measurement unit;

[0044] Figure 4 is a circuit schematic diagram of the busbar-to-ground voltage measurement unit;

[0045] Figure 5 is a circuit schematic diagram of the balanced bridge resistance and control unit;

[0046] Figure 6 is a circuit schematic diagram of the detection bridge resistance and control unit;

[0047] Figure 7 It is a circuit schematic diagram of the heteropolar ring network test resistor and control unit;

[0048] Figure 8 It is a circuit schematic diagram of the homopolar ring network test resistor and control unit. DETAILED DESCRIPTION

[0049] like Figures 1 to 8 As shown, in this embodiment, the present invention includes a central processing unit 1, a heteropolar ring network test resistor and control unit 12, a homopolar ring network test resistor and control unit 13 and two groups of busbars, the heteropolar ring network test resistor and control unit 12 includes a first resistor R+- and a second resistor R-+, the homopolar ring network test resistor and control unit 13 includes a third resistor R++ and a fourth resistor R--, the two groups of busbars include 1M+, 1M-, 2M+ and 2M-, the first resistor R+- is connected between the 1M+ and the 2M-, the second resistor R-+ is connected between the 1M- and the 2M+, the third resistor R++ is connected between the 1M+ and the 2M+, the fourth resistor R- is connected between the 1M- and the 2M-, the central processing unit 1 is connected between the Two groups of bus voltage measurement units, two groups of bus-to-ground voltage measurement units, two groups of balancing bridge resistances and control units, and two groups of detection bridge resistances and control units are connected. All of the above units are symmetrically connected to the two ends of the same-pole ring network test resistance and control unit 13 and are connected to the two groups of busbars. The two groups of balancing bridge resistances and control units include a fifth resistor RP1+, a sixth resistor RP1-, a seventh resistor RP2+, and an eighth resistor RP2-. The two groups of detection bridge resistances and control units include a ninth resistor RJ1+, a tenth resistor RJ1-, an eleventh resistor RJ2+, a twelfth resistor RJ2-, a first switch Kj1-, and a second switch Kj2-. The tenth resistor RJ1- is connected in series with the first switch Kj1-, and the twelfth resistor RJ2- is connected in series with the second switch Kj2-.

[0050] In this embodiment, the device for detecting the ring network resistance value further includes a data display unit 2, the data display unit 2 is electrically connected to the central processing unit 1, and the data display unit 2 displays measurement data and test results.

[0051] In this embodiment, the device for detecting the ring network resistance also includes a data communication unit 3, which is electrically connected to the central processing unit 1, and sends measurement data and test results according to the instructions of the central processing unit 1.

[0052] In this embodiment, the two groups of bus voltage measurement units include a first group of bus voltage measurement units 4 and a second group of bus voltage measurement units 5, the first group of bus voltage measurement units 4 are connected to the 1M+ and the 1M-, and the second group of bus voltage measurement units 5 are connected to the 2M+ and the 2M-.

[0053] In this embodiment, the center points of the series resistors of the two groups of busbar-to-ground voltage measurement units are connected to PE, and the PE is an insulated protective ground. The two groups of busbar-to-ground voltage measurement units include a first group of busbar positive and negative pole-to-ground voltage measurement units 6 and a second group of busbar positive and negative pole-to-ground voltage measurement units 7. The first group of busbar positive and negative pole-to-ground voltage measurement units 6 are connected to the 1M+, the 1M- and the PE, and the second group of busbar positive and negative pole-to-ground voltage measurement units 7 are connected to the 2M+, the 2M- and the PE.

[0054] In this embodiment, the two groups of balanced bridge resistors and control units include a first group of balanced bridge resistors and control units 8 and a second group of balanced bridge resistors and control units 9. The first group of balanced bridge resistors and control units 8 are connected to the 1M+, the 1M- and the PE, and the second group of balanced bridge resistors and control units 9 are connected to the 2M+, the 2M- and the PE.

[0055] In this embodiment, the two groups of detection bridge resistors and control units include a first group of detection bridge resistors and control units 10 and a second group of detection bridge resistors and control units 11. The first group of detection bridge resistors and control units 10 are connected to the 1M+, the 1M- and the PE, and the second group of detection bridge resistors and control units 11 are connected to the 2M+, the 2M- and the PE.

[0056] In this embodiment, the heteropolar ring network test resistor and control unit 12 includes a third switch K+- and a fourth switch K-+, the first resistor R+- is connected between the 1M+ and the third switch K+-, the other end of the third switch K+- is connected to the 2M-, the second resistor R-+ is connected between the 1M- and the fourth switch K-+, and the other end of the fourth switch K-+ is connected to the 2M+.

[0057] In this embodiment, the homopolar ring network test resistor and control unit 13 also includes a fifth switch K++ and a sixth switch K--, the third resistor R++ is connected between the 1M+ and the fifth switch K++, the other end of the fifth switch K++ is connected to the 2M+, the fourth resistor R-- is connected between the 1M- and the sixth switch K--, and the other end of the sixth switch K-- is connected to the 2M-.

[0058] Working principle of the present invention:

[0059] The heteropolar ring network test resistor and control unit include a first resistor R+- and a second resistor R-+, the homopolar ring network test resistor and control unit include a third resistor R++ and a fourth resistor R--, the two groups of busbars include 1M+, 1M-, 2M+ and 2M-, the first resistor R+- is connected between the 1M+ and the 2M-, the second resistor R-+ is connected between the 1M- and the 2M+, the third resistor R++ is connected between the 1M+ and the 2M+, the fourth resistor R- is connected between the 1M- and the 2M-, the central processing unit is electrically connected with two groups of busbar voltage measurement units, two groups of busbar-to-ground voltage measurement units, and two groups of balancing bridges. Resistance and control unit and two groups of detection bridge resistance and control unit, all of the above units are symmetrically connected to the two ends of the same-polarity ring network test resistance and control unit and are connected to the two groups of busbars, the two groups of the balanced bridge resistance and control unit include a fifth resistor RP1+, a sixth resistor RP1-, a seventh resistor RP2+ and an eighth resistor RP2-, the two groups of the detection bridge resistance and control unit include a ninth resistor RJ1+, a tenth resistor RJ1-, an eleventh resistor RJ2+, a twelfth resistor RJ2-, a first switch Kj1- and a second switch Kj2-, the tenth resistor RJ1- is connected in series with the first switch Kj1-, and the twelfth resistor RJ2- is connected in series with the second switch Kj2-.

[0060] The voltage division values ​​obtained by the two groups of bus voltage measurement units are Um1 and Um2 respectively, and the voltage division values ​​obtained by the two groups of bus-to-ground voltage measurement units are U1+, U1-, U2+ and U2- respectively. The rated voltage of the DC system is Un. When the system is operating normally, the two groups of balancing bridge resistance and control units are controlled by the central processing unit to input Kp1+, Kp1-, Kpe1, Kp2+, Kp2-, Kpe2 respectively;

[0061] 1. When the voltage difference between the two groups of busbar-to-ground voltage measurement units is greater than 10%Un, that is, the difference between U1+ and U1-, and the difference between U2+ and U2-:

[0062] 1. If U1+ < U1- and U2+ > U2-, at this time, the tenth resistor RJ1- is controlled by the central processing unit to be connected to the first switch Kj1-. If the voltage difference between U2+ and U2- changes greater than a fixed value, it can be determined that the positive pole of one group of the busbars and the negative pole of the other group of the busbars are in a different-pole loop network. The calculation formula for the loop resistance is:

[0063]

[0064] 2. If U1+ > U1- and U2+ < U2-, at this time, the twelfth resistor RJ2- is controlled by the central processing unit to be connected to the second switch Kj2-. If the voltage difference between U1+ and U1- changes greater than a fixed value, it can be determined that the negative pole of one group of the busbars and the positive pole of the other group of the busbars are in a different-pole loop network. The calculation formula for the loop resistance is:

[0065]

[0066] II. When the system is operating normally, if the timing detection period arrives or a manual trigger instruction is given, at this time, the tenth resistor RJ1- is controlled by the central processing unit to be connected to the first switch Kj1-, and the twelfth resistor RJ2- is controlled by the central processing unit to be connected to the second switch Kj2-. At this time:

[0067] 1. The tenth resistor RJ1- is controlled by the central processing unit to be connected to the first switch Kj1-. If U1+ > U1- and U2+ > U2-, and the voltage difference change between U2+ and U2- greater than a fixed value is used as the judgment condition A, the tenth resistor RJ1- is controlled by the central processing unit to be disconnected from the first switch Kj1-;

[0068] 2. The twelfth resistor RJ2- is controlled by the central processing unit to be connected to the second switch Kj2-. If U2+ > U2- and U1+ > U1-, and the voltage difference change between U1+ and U1- greater than a fixed value is used as the judgment condition B, the twelfth resistor RJ2- is controlled by the central processing unit to be disconnected from the second switch Kj2-;

[0069] If both the judgment condition A and the condition B are satisfied, it can be judged as a same-pole loop network;

[0070] According to the principle of equal current:

[0071]

[0072] The calculation formula for the loop resistance can be deduced:

[0073]

[0074] Wherein: is the voltage difference to ground when Kj- is closed, is the differential current flowing through PE when Kj- is closed, and the device for detecting the ring network resistance can determine the type of bus ring network fault periodically or manually and instantly without affecting the insulation safety of the system, and accurately detect the ring network resistance.

Claims

1. A device for detecting the resistance of a ring network, characterized in that: It comprises a central processing unit (1), a heteropolar ring network test resistor and control unit (12), a homopolar ring network test resistor and control unit (13), and two sets of busbars, wherein the two sets of busbars comprise a first busbar positive pole (1M+), a first busbar negative pole (1M-), a second busbar positive pole (2M+), and a second busbar negative pole (2M-). The heteropolar ring network test resistor and control unit (12) comprises a first resistor (R+-), a second resistor (R-+), a third switch (K+-) and a fourth switch (K-+), wherein the first resistor (R+-) is connected between the positive pole (1M+) of the first bus section and the third switch (K+-), the other end of the third switch (K+-) is connected to the negative pole (2M-) of the second bus section, the second resistor (R-+) is connected between the negative pole (1M-) of the first bus section and the fourth switch (K-+), and the other end of the fourth switch (K-+) is connected to the positive pole (2M+) of the second bus section; The homopolar ring network test resistor and control unit (13) comprises a third resistor (R++), a fourth resistor (R--), a fifth switch (K++) and a sixth switch (K--), wherein the third resistor (R++) is connected between the positive pole (1M+) of the first bus section and the fifth switch (K++), the other end of the fifth switch (K++) is connected to the positive pole (2M+) of the second bus section, the fourth resistor (R--) is connected between the negative pole (1M-) of the first bus section and the sixth switch (K--), and the other end of the sixth switch (K--) is connected to the negative pole (2M-) of the second bus section; The central processing unit (1) is electrically connected to two groups of bus voltage measurement units, two groups of bus-to-ground voltage measurement units, two groups of balancing bridge resistance and control units, and two groups of detection bridge resistance and control units. The two groups of bus voltage measurement units, the two groups of bus-to-ground voltage measurement units, the two groups of balancing bridge resistance and control units, and the two groups of detection bridge resistance and control units are all symmetrically connected to the two ends of the same-pole ring network test resistor and control unit (13) and are all connected to the two groups of bus bars. The two groups of the balanced bridge resistance and control unit include a fifth resistor (RP1+), a sixth resistor (RP1-), a seventh resistor (RP2+), an eighth resistor (RP2-), and control switches respectively connected in series with the fifth resistor (RP1+), the sixth resistor (RP1-), the seventh resistor (RP2+), and the eighth resistor (RP2-), and the connection point between the fifth resistor (RP1+) and the sixth resistor (RP1-) and the connection point between the seventh resistor (RP2+) and the eighth resistor (RP2-) are also connected to the insulation protection ground (PE) through the control switch; The two groups of detection bridge resistance and control units include a ninth resistor (RJ1+), a tenth resistor (RJ1-), an eleventh resistor (RJ2+), a twelfth resistor (RJ2-), and control switches respectively connected in series with the ninth resistor (RJ1+), the tenth resistor (RJ1-), the eleventh resistor (RJ2+), and the twelfth resistor (RJ2-); the connection point between the ninth resistor (RJ1+) and the tenth resistor (RJ1-), and the connection point between the eleventh resistor (RJ2+) and the twelfth resistor (RJ2-) are also connected to the insulation protection ground (PE) through the control switch.

2. The device for detecting the resistance of a ring network according to claim 1, characterized in that: The device for detecting the ring network resistance value further comprises a data display unit (2), wherein the data display unit (2) is electrically connected to the central processing unit (1), and the data display unit (2) displays measurement data and test results.

3. The device for detecting the resistance of a ring network according to claim 1, characterized in that: The device for detecting the ring network resistance value further comprises a data communication unit (3), wherein the data communication unit (3) is electrically connected to the central processing unit (1), and the data communication unit (3) sends out measurement data and test results according to instructions of the central processing unit (1).

4. The device for detecting the resistance of a ring network according to claim 1, characterized in that: The two groups of bus voltage measurement units include a first group of bus voltage measurement units (4) and a second group of bus voltage measurement units (5), wherein the first group of bus voltage measurement units (4) is connected to the positive pole (1M+) of the first bus section and the negative pole (1M-) of the first bus section, and the second group of bus voltage measurement units (5) is connected to the positive pole (2M+) of the second bus section and the negative pole (2M-) of the second bus section.

5. The device for detecting the resistance of a ring network according to claim 1, characterized in that: The center points of the series resistors of the two groups of busbar-to-ground voltage measurement units are connected to an insulating protective earth (PE), and the two groups of busbar-to-ground voltage measurement units include a first group of busbar positive and negative pole-to-ground voltage measurement units (6) and a second group of busbar positive and negative pole-to-ground voltage measurement units (7), the first group of busbar positive and negative pole-to-ground voltage measurement units (6) being connected to the first section busbar positive pole (1M+), the first section busbar negative pole (1M-) and the insulating protective earth (PE), and the second group of busbar positive and negative pole-to-ground voltage measurement units (7) being connected to the second section busbar positive pole (2M+), the second section busbar negative pole (2M-) and the insulating protective earth (PE).

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