Ship DC busbar insulation monitoring and fault positioning system and method

Abstract

The invention discloses a ship DC busbar insulation monitoring and fault positioning system and method. The system comprises a DC busbar, a bridge arm network, a plurality of DC power utilization branches, a signal source and a sampling resistor. The bridge arm network adopts a three-layer structure design and comprises a KE detection bridge arm, a main bridge arm and a positioning bridge arm, and each bridge arm is composed of a positive resistor and a negative resistor. The system injects an alternating current signal to a direct current busbar through a signal source, system self-inspection and voltage measurement are achieved through a KE detection bridge arm, insulation state real-time monitoring is conducted through a main bridge arm, and when an insulation fault is detected, a low-resistance path is provided through a positioning bridge arm, and accurate positioning of a fault branch is achieved in combination with a leakage current detector of each branch. According to the invention, insulation monitoring and fault positioning can be completed under the condition that an electricity utilization branch is not disconnected, and the reliability and maintenance efficiency of a ship power system are remarkably improved.

Description

Technical Field

[0001] This invention relates to an insulation monitoring and fault location system, and more particularly to a system and method for monitoring and locating insulation of a ship's DC busbar. Background Technology

[0002] In a ship's DC power system, the insulation condition of the DC busbar directly affects the safety, reliability, and stable operation of the entire system. Due to the humid environment and strong salt spray corrosion on ships, the insulation of electrical equipment and lines is prone to deterioration, leading to a decrease in insulation resistance and even single-pole grounding faults. If the fault is not detected and located in time, it may develop into a double-pole grounding short circuit, causing widespread power outages, equipment damage, and even fires, seriously threatening the safety of ship operations.

[0003] Currently, commonly used DC system insulation monitoring methods mostly employ balanced or unbalanced bridge methods. These methods, based on the bridge principle, monitor the overall insulation resistance decrease of the system to ground, but have significant limitations: 1. They can only provide an overall insulation status alarm and cannot accurately locate the faulty branch when a single-point grounding fault occurs in the system; 2. When the system alarms, maintenance personnel need to manually disconnect each branch for troubleshooting, which is cumbersome, time-consuming, and may affect the normal power supply of non-faulty branches during the troubleshooting process, reducing the continuity of system power supply; 3. Some solutions require an external dedicated positioning module to work with the insulation detection module, resulting in a complex system structure, large footprint, and inconvenience of use. Summary of the Invention

[0004] Objectives of the invention: The first objective of this invention is to provide a shipboard DC bus insulation monitoring and fault location system capable of real-time monitoring of DC bus insulation status and rapid and accurate location of faulty branches when insulation faults occur; the second objective of this invention is to provide an insulation monitoring and fault location method based on the system.

[0005] Technical solution: The ship DC busbar insulation monitoring and fault location system of the present invention includes a DC busbar, a bridge arm network, multiple DC power branches, a signal source and a sampling resistor;

[0006] The bridge arm network includes a KE detection bridge arm for system self-testing and measuring DC bus voltage, a main bridge arm for real-time insulation status monitoring, and a positioning bridge arm for precise fault location. Each KE detection bridge arm, main bridge arm, and positioning bridge arm includes a positive resistor and a negative resistor, which are connected in series. The positive resistor is connected to the positive terminal of the DC bus via a corresponding positive switch, and the negative resistor is connected to the negative terminal of the DC bus via a corresponding negative switch.

[0007] The positive terminal of the signal source is connected to the signal injection point PE, and the negative terminal is grounded through the sampling resistor;

[0008] The positive and negative resistors of the KE detection bridge arm are connected to a KE detection point, and the signal injection point PE is connected to the KE detection point through a detection switch; the positive and negative resistors of the main bridge arm and the positioning bridge arm are grounded.

[0009] Each of the DC power supply branches is equipped with a leakage current detector.

[0010] Preferably, the leakage current detector is a fluxgate leakage current transformer.

[0011] Preferably, the signal source output is a low-frequency AC signal.

[0012] Preferably, the signal source is an AC signal source with adjustable frequency and voltage amplitude, which can adjust the output parameters according to the voltage and insulation level of the DC bus.

[0013] Preferably, the resistance values ​​of the positive and negative terminals of the positioning bridge arm are smaller than those of the positive and negative terminals of the main bridge arm, and significantly smaller than the equivalent insulation resistance value of the DC power supply branch. The difference between the resistance values ​​of the positive and negative terminals of the positioning bridge arm and the equivalent insulation resistance value of the DC power supply branch is at least two orders of magnitude.

[0014] Preferably, the resistance values ​​of the resistor components in the KE detection arm, main arm, and positioning arm are designed according to the voltage level of the DC busbar to limit the current in the monitoring circuit and positioning circuit.

[0015] Preferably, the positive switch, negative switch, and detection switch are high-voltage switches.

[0016] The method for monitoring and locating the insulation of a ship's DC busbar as described in this invention, using the system described in this invention, includes the following steps:

[0017] (1) System initialization: Close the detection switch to connect the KE detection bridge arm and perform connection status detection between the PE point and the KE detection point;

[0018] (2) Insulation monitoring: After the test is completed, disconnect the test switch, measure the bus voltage, disconnect the KE test bridge arm, connect the main bridge arm, inject an AC test signal into the DC bus, and monitor the response signal of the sampling resistor. Insulation monitoring is performed through the monitoring circuit formed by the main bridge arm, the signal source, and the sampling resistor.

[0019] (3) Fault branch location: When an insulation fault is detected, under the premise of maintaining power supply to all power branches, the leakage current characteristics of the fault branch are changed by controlling the positioning bridge arm to engage a low-resistance path, and the fault branch is located by comparing the leakage current of each branch.

[0020] Furthermore, step (2) includes:

[0021] (21) Measure the busbar voltage, disconnect the KE detection arm, and connect the main arm;

[0022] (22) Inject an AC voltage signal with adjustable frequency and amplitude into the DC bus through a signal source;

[0023] (23) Acquire the voltage response signal across the sampling resistor;

[0024] (24) The insulation status of the system is determined by analyzing the voltage waveform characteristics of the response signal and the injected signal.

[0025] Furthermore, step (3) includes:

[0026] (31) Selectively engage the positive or negative path of the positioning bridge arm according to the polarity of the insulation fault;

[0027] (32) After the positioning bridge arm is put into operation, the leakage current of all power-consuming branches is collected synchronously through the fluxgate leakage current transformer;

[0028] (33) A branch whose leakage current change exceeds a threshold and is significantly greater than that of other branches is identified as a faulty branch. The threshold is dynamically adjusted based on the DC grid voltage and a preset insulation fault value. For example, the threshold is set to 50 times the base leakage current. When the change of a branch reaches 50 times and is more than 20 times the average value of other branches, it is identified as a faulty branch.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) It can accurately locate the specific branch of the insulation fault; (2) It can realize online monitoring of the insulation status of the DC busbar and fault location without cutting off the power supply. Attached Figure Description

[0030] Figure 1 This is the equivalent circuit diagram of the present invention;

[0031] Figure 2 This is a schematic diagram of the key waveforms for insulation monitoring in this invention;

[0032] Figure 3 This is the positioning equivalent circuit diagram of the present invention;

[0033] Figure 4 This is a simulation waveform of the fluxgate leakage current of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0035] As shown in the attached figure, the present invention relates to a system and method for monitoring and locating the insulation of a ship's DC busbar. The system mainly includes the DC busbar under test, a KE detection bridge arm, a signal source, a sampling resistor, a main bridge arm, a positioning bridge arm, and a DC power supply branch.

[0036] I. System Composition and Connections

[0037] 1. System Components

[0038] DC busbar under test: includes the positive and negative terminals of the DC busbar and the equivalent insulation resistance (R). p and R N ) and equivalent insulation capacitance (C p and C N );

[0039] KE detection bridge arm: includes the positive resistor R of the KE detection bridge arm KEP and negative resistance R KEN ;

[0040] Signal source: Provides an AC voltage signal with adjustable frequency and amplitude. ac ;

[0041] Sampling resistor: R S ;

[0042] Main bridge arm: Positive resistor R of the main bridge arm MP and negative resistance R MN ;

[0043] Positioning bridge arm: Positive resistor R of the positioning bridge arm DP and negative resistance R DN ;

[0044] High-voltage switches include KE detection bridge arm positive switch S1, KE detection bridge arm negative switch S2, detection switch S3, main bridge arm positive switch S4, main bridge arm negative switch S5, positioning bridge arm positive switch S6, and positioning bridge arm negative switch S7.

[0045] DC power branch: contains n DC power load units, each load unit includes a load resistor R. Li Equivalent insulation resistance (R) LiP and R LiN ) and equivalent insulation capacitance (C LiP and C LiN ) and fluxgate leakage current transformer CT Li Where i is a positive integer.

[0046] 2. Electrical connection relationship

[0047] The DC bus positive terminal is connected to the first interface of S1, the first interface of S4, the first interface of S6, and the DC load R.Li One end is connected; the negative terminal of the DC busbar is connected to the first interface of S2, the first interface of S5, the first interface of S7, and the DC load R. Li The other end is connected.

[0048] The second interface of S1 is connected to the positive resistor R of the KE detection bridge arm. KEP Connected, R KEP The other end connects to the first interface of S3, and the negative resistor R of the KE detection bridge arm. KEN Connected to detection point KE; R KEN The other end is connected to the second interface of S2.

[0049] The second interface of S4 is connected to the positive resistor R of the main bridge arm. MP Connection, R MP The other end is connected to the negative resistor R of the main bridge arm. MN Sampling resistor R S Positioning bridge arm positive resistor R DP Positioning bridge arm negative resistor R DN Connected to GND; R MN The other end connects to the second interface of S5, R DN The other end is connected to the second interface of the S7.

[0050] Injected signal u ac The positive terminal of S3 is connected to the second interface of S3 at the signal injection point PE, and the injected signal u ac The negative terminal and the sampling resistor R S The other end is connected.

[0051] II. System Workflow

[0052] 1. System self-test

[0053] When the system starts up, S3 is closed to put the KE detection bridge arm into operation. This stage mainly verifies the connection status from the PE point to the KE point: through the resistor voltage divider network of the KE detection bridge arm, the voltage signal is sampled at the KE point, and a low-frequency AC signal is injected. The waveform of the sampled voltage signal at the KE point is judged to determine whether the bridge arm network connection is normal.

[0054] After the above tests are completed and the results are normal, the system enters the insulation monitoring stage.

[0055] 2. Insulation monitoring stage

[0056] (1) Disconnect the S3 isolation KE detection bridge arm, turn off the injection signal, sample the voltage signal at the KE point through the resistor voltage divider network of the KE detection bridge arm, obtain the actual working voltage value of the DC bus, and provide reference parameters for subsequent monitoring.

[0057] (2) Close S4 and S5 to put the main bridge arm into operation and establish the main circuit for insulation monitoring.

[0058] (3) The signal source generates an adjustable AC signal u ac Through sampling resistor R S Injected into the DC busbar. The signal flows through the busbar's insulation parameter to ground (R). p R N C p and C N This generates a response current, creating a voltage drop U across the sampling resistor. RS .

[0059] (4) By analyzing U RS The voltage waveform characteristics are used to determine the system insulation status; when an insulation anomaly is detected, the fault location process is triggered. The analysis and judgment are based on the following:

[0060] Appendix Figure 2 The key insulation monitoring waveforms for four systems are displayed. Among them, Figure 2 (a) When the equivalent insulation resistance of all loads on the DC busbar and DC power supply branches is normal and the equivalent capacitance is small, a signal u is injected. ac and sampling resistor u RS The voltage waveform, due to normal insulation and a small equivalent capacitance, is determined by the injected signal u. ac The current generated in the circuit is very small, thus the sampling resistor u RS The voltage value is also very small; Figure 2 (b) When the equivalent insulation resistance of all loads on the DC busbar and DC power branches is normal and the equivalent capacitance is large, a signal u is injected. ac and sampling resistor u RS The voltage waveform, due to the presence of a large equivalent insulation capacitance, is affected by the injected signal u. ac At the moment of change, a large current will be generated in the circuit. As the equivalent insulation capacitance completes its charging and discharging, the current gradually decreases until a steady state is reached, and finally the sampling resistor u... RS The voltage is also very small; Figure 2 (c) When the equivalent insulation resistance of the negative terminal of a load in a DC busbar or DC power supply branch is normal, the equivalent insulation resistance of the positive terminal is abnormal, and the equivalent capacitance is small, a signal u is injected. ac and sampling resistor u RS The voltage waveform, due to the abnormal equivalent insulation resistance of the positive terminal, and due to the presence of the DC bus voltage, the sampling resistor u RS It is a waveform with DC component superimposed on AC component, and the voltage value is relatively large; Figure 2 (d) When the equivalent insulation resistance of the negative terminal of a load in a DC busbar or DC power supply branch is normal, but the equivalent insulation resistance of the positive terminal is abnormal and the equivalent capacitance is large, a signal u is injected. ac and sampling resistor uRS The voltage waveform, due to the presence of the equivalent insulation capacitance, is affected by the injected signal u. ac At the moment of change, a large current will be generated at the sampling resistor u. RS Small spikes will appear on the waveform, which is also a waveform of DC component superimposed on AC component.

[0061] Through comparative analysis Figure 2 The four key waveforms shown can quickly and accurately determine different insulation states of the system. The normal insulation state of the system is characterized by… Figure 2 (a) or Figure 2 (b) Waveform characteristics; the system's positive electrode insulation fault state manifests as Figure 2 (c) or Figure 2 (d) Waveform characteristics.

[0062] 3. Fault location stage

[0063] (1) Keep all power supply branches powered and selectively engage the positioning bridge arm according to the fault polarity.

[0064] (2) When the positive terminal fails, close S7 and the positive terminal resistor R of the positioning bridge arm is activated. DP Provides a low-resistance path; in case of a negative terminal fault, S6 is closed, and the negative terminal resistor R of the positioning bridge arm is activated. DN Provide a low-resistance path. Position the bridge arm resistance to be significantly lower than the branch insulation resistance, ensuring that fault characteristics are significantly amplified.

[0065] (3) Through the fluxgate leakage current transformers of each branch, the leakage current changes of all branches before and after the positioning bridge arm is put into operation are collected synchronously. The faulty branch shows a significant increase in leakage current amplitude, while the non-faulty branch shows a small change.

[0066] (4) Accurately identify the faulty branch by comparing the relative changes in leakage current of each branch. After the positioning is completed, the positioning bridge arm switch is automatically disconnected, normal monitoring is restored, and specific faulty branch information is output.

[0067] The following is a specific analysis using the abnormal reduction in insulation value of the positive equivalent resistance of DC power branch 1 as an example.

[0068] The equivalent circuit in the fault location stage is as follows: Figure 3 As shown. Among them, Figure 3 (a) is the equivalent circuit when the positioning bridge arm is disconnected. The insulation monitoring system determines that there is an insulation fault abnormality at the positive terminal of the DC bus system, but it is currently unknown which branch has the insulation fault. Figure 3 (b) is the equivalent circuit when the positioning bridge arm is connected. When the insulation detection system closes S7, due to the negative resistance R of the positioning bridge arm... DNThe value is much smaller than the equivalent insulation resistance of the negative terminal of DC power branch 1. At this time, because S7 is conducting, the resistance is reduced by the negative terminal resistance R of S7 and the positioning bridge arm. DN This creates a current flow path, causing current to flow into the fluxgate leakage current transformer (CT). L1 The difference between the current flowing in and the current flowing out increases, while the difference changes less in other normally insulated DC power branches.

[0069] Figure 4 Given Figure 2 (c) Simulation waveform of leakage current of the fluxgate leakage current transformer during positioning process. Wherein: Figure 4 (a) shows the leakage current waveform of the fluxgate leakage current transformer corresponding to the faulty branch. Before the 10th second, S7 in the positioning bridge arm is not conducting. At this time, the faulty line is only a loop composed of equivalent insulation resistance, with no current path. This results in a small difference in the current flowing through the fluxgate leakage current transformer, making it difficult to detect and susceptible to interference. When the 10th second arrives, the high-voltage switch S7 conducts, and the current flows through the negative resistor R of the positioning bridge arm. DN This forms a current flow path, and the current flowing through the fluxgate leakage current transformer in the fault branch varies greatly. Figure 4 (b) shows the leakage current waveform of the fluxgate leakage current transformer corresponding to the non-faulty branch. The current difference flowing through the fluxgate leakage current transformer in the non-faulty branch is still very small, and the fault current can be clearly detected and is not easily affected by interference.

[0070] III. Key Parameters and Characteristics

[0071] 1. Inject signal characteristics

[0072] Injected signal u ac The frequency and voltage amplitude are adjustable, and can be adjusted in real time according to the voltage and insulation level of the DC busbar to ensure optimal detection results.

[0073] 2. System protection mechanism

[0074] The detection uses an adjustable low-frequency AC signal, which does not affect the normal operation of the DC system. During positioning, a current-limiting resistor is used, minimizing the impact on the system.

Claims

1. A ship DC busbar insulation monitoring and fault location system, characterized in that, This includes DC busbars, bridge arm networks, multiple DC power branches, signal sources, and sampling resistors; The bridge arm network includes a KE detection bridge arm for system self-testing and measuring DC bus voltage, a main bridge arm for real-time insulation status monitoring, and a positioning bridge arm for precise fault location. Each KE detection bridge arm, main bridge arm, and positioning bridge arm includes a positive resistor and a negative resistor, which are connected in series. The positive resistor is connected to the positive terminal of the DC bus via a corresponding positive switch, and the negative resistor is connected to the negative terminal of the DC bus via a corresponding negative switch. The positive terminal of the signal source is connected to the signal injection point PE, and the negative terminal is grounded through the sampling resistor; The positive and negative resistors of the KE detection bridge arm are connected to a KE detection point, and the signal injection point PE is connected to the KE detection point through a detection switch; the positive and negative resistors of the main bridge arm and the positioning bridge arm are grounded. Each of the DC power supply branches is equipped with a leakage current detector.

2. The system according to claim 1, characterized in that, The leakage current detector is a fluxgate leakage current transformer.

3. The system according to claim 1, characterized in that, The signal source outputs a low-frequency AC signal.

4. The system according to claim 1, characterized in that, The signal source is an AC signal source with adjustable frequency and voltage amplitude, and its output parameters can be adjusted according to the voltage and insulation level of the DC bus.

5. The system according to claim 1, characterized in that, The resistance values ​​of the positive and negative terminals of the positioning bridge arm are less than those of the positive and negative terminals of the main bridge arm, and significantly less than the equivalent insulation resistance value of the DC power supply branch.

6. The system according to claim 1, characterized in that, The resistance values ​​of the resistor components in the KE detection bridge arm, main bridge arm, and positioning bridge arm are designed according to the voltage level of the DC busbar to limit the current in the monitoring circuit and positioning circuit.

7. The system according to claim 1, characterized in that, The positive switch, negative switch, and detection switch are high-voltage switches.

8. A method for monitoring and locating insulation faults in a ship's DC busbar, employing the system described in claims 1 to 7, characterized in that, Includes the following steps: (1) System initialization: Close the detection switch to connect the KE detection bridge arm and perform connection status detection between the PE point and the KE detection point; (2) Insulation monitoring: After the test is completed, disconnect the test switch, measure the bus voltage, disconnect the KE test bridge arm, connect the main bridge arm, inject an AC test signal into the DC bus, and monitor the response signal of the sampling resistor. Insulation monitoring is performed through the monitoring circuit formed by the main bridge arm, the signal source, and the sampling resistor. (3) Fault branch location: When an insulation fault is detected, under the premise of maintaining power supply to all power branches, the leakage current characteristics of the fault branch are changed by controlling the positioning bridge arm to engage a low-resistance path, and the fault branch is located by comparing the leakage current of each branch.

9. The method according to claim 8, characterized in that, Step (2) includes: (21) Measure the busbar voltage, disconnect the KE detection arm, and connect the main arm; (22) Inject an AC voltage signal with adjustable frequency and amplitude into the DC bus through a signal source; (23) Acquire the voltage response signal across the sampling resistor; (24) The insulation status of the system is determined by analyzing the voltage waveform characteristics of the response signal and the injected signal.

10. The method according to claim 8, characterized in that, Step (3) includes: (31) Selectively engage the positive or negative path of the positioning bridge arm according to the polarity of the insulation fault; (32) After the positioning bridge arm is put into operation, the leakage current of all power-consuming branches is collected synchronously through the fluxgate leakage current transformer; (33) A branch whose leakage current changes more than a threshold and is significantly greater than that of other branches is identified as a faulty branch. The threshold is dynamically adjusted according to the DC grid voltage and the preset insulation fault value.

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