CN110542829A - direct-current grounding judgment device and method for power distribution network below 35kV - Google Patents
direct-current grounding judgment device and method for power distribution network below 35kV Download PDFInfo
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- CN110542829A CN110542829A CN201910754600.XA CN201910754600A CN110542829A CN 110542829 A CN110542829 A CN 110542829A CN 201910754600 A CN201910754600 A CN 201910754600A CN 110542829 A CN110542829 A CN 110542829A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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Abstract
the invention discloses a direct current grounding judgment device and a direct current grounding judgment method for a power distribution network below 35kV, wherein the direct current grounding judgment device comprises an insulation monitoring device, a DC/DC power supply module and a power supply switching controller, the insulation monitoring device is connected with a direct current bus in parallel, a plurality of branches are connected on the direct current bus in parallel, a branch switch and a wiring terminal are connected on each branch in series, the wiring terminal is electrically connected with the direct current bus through the branch switch, the input end of the DC/DC power supply module is electrically connected with the direct current bus, the output end of the DC/DC power supply module is electrically connected with the input end of the power supply switching controller, and the output end of the power supply switching controller is electrically connected with the wiring terminal. The invention also provides a direct current grounding judgment method based on the direct current grounding judgment device, the device of the invention has low cost and high detection speed, and after the new power supply is connected with the original system circuit in parallel, the branch of the original system is disconnected, so that the back-end equipment of the branch cannot be powered off, and the reliability of power supply is ensured.
Description
Technical Field
the invention belongs to the technical field of power systems, and particularly relates to a direct-current grounding judgment device and a direct-current grounding judgment method for a power distribution network below 35 kV.
background
The direct-current power supply system of the transformer substation is a floating operation system, namely an ungrounded system, a 10KV power distribution network supplies power to all branches on a feeder screen through a group of direct-current buses, 110KV and above supplies power to all branches on the feeder screen through two groups of branch buses, the two groups of direct-current buses are connected in parallel through a loop or the tail ends, a large number of field direct-current power supply devices are provided, power supply cables are long, and faults such as direct-current grounding and the like frequently occur when a power supply loop is complex. When a power system has a one-point grounding fault (direct grounding or reduction of insulation resistance to ground), a dangerous result is generally not generated immediately, but if two points are grounded simultaneously, false operation of a signal device, a control loop and a relay protection device can be caused, so that a circuit breaker trips or a direct current power supply is directly short-circuited, and a serious power system accident is caused. Therefore, the power system is not allowed to operate for a long time under the condition of one-point direct current grounding, the power system needs to be continuously monitored on line, and when one-point direct current grounding fault occurs, the power system needs to be immediately isolated, so that the power system fault caused by the direct current grounding fault is avoided.
the existing direct current ground fault detection method comprises the following steps: and detecting electronic equipment such as a balanced bridge method, an unbalanced bridge method, a signal tracing method, a leakage current method and the like. However, both the balanced bridge method and the unbalanced bridge method can only detect the insulation condition of the whole power system, and when a branch with a dc ground fault is located, the connection between each branch and the dc bus needs to be sequentially disconnected, so that the branch with the dc bus disconnected runs in an unprotected state, and no operation can be performed therebetween. In addition, the influence of the field environment is large, and particularly, the branch where the direct-current ground fault is located can be judged by a signal tracing method and a leakage current method when a loop or a parasitic loop exists in a feeder line branch, but the branch is easily influenced by branch capacitance, sensor precision, a ring network and ripple interference, and misjudgment is easily caused.
Disclosure of Invention
the invention overcomes the defects of the prior art, and solves the technical problems that: the direct current grounding judgment device and the direct current grounding judgment method have the advantages that the branch operation is not influenced, the cost is low, the single-phase grounding point is quickly positioned, and the direct current grounding judgment device and the direct current grounding judgment method are used for a power distribution network below 35 kV.
In order to solve the technical problems, the invention adopts the technical scheme that: a direct current grounding judgment device for a power distribution network below 35kV comprises an insulation monitoring device, a DC/DC power supply module and a power supply switching controller, wherein the insulation monitoring device is connected with a direct current bus in parallel, a plurality of branches are connected to the direct current bus in parallel, a branch switch and a wiring terminal are connected to each branch in series, the wiring terminal is electrically connected with the direct current bus through the branch switch, the input end of the DC/DC power supply module is electrically connected with the direct current bus, the output end of the DC/DC power supply module is electrically connected with the input end of the power supply switching controller, and the output end of the power supply switching controller is electrically connected with the wiring terminal on each branch respectively.
Preferably, the direct-current grounding judgment device for the power distribution network below 35kV comprises a plurality of insulation monitoring devices and a DC/DC power module, wherein an input end of the DC/DC power module is electrically connected with a direct-current bus, an output end of each DC/DC power module is electrically connected with a load through a branch switch and a connecting terminal on the direct-current bus in sequence, and the insulation monitoring devices are connected with output ends of the DC/DC power modules in parallel.
Preferably, the DC/DC power supply module comprises an inductor L1, a transformer T1, a triode Q1, one end of the inductor L2 is connected to the positive output terminal of the dc bus, one end of the transformer T1 reset winding, and one end of the transformer T1 home winding, the other end of the transformer T1 reset winding is connected to the negative electrode of the diode D3, the positive electrode of the diode D3 and the emitter of the transistor Q1 are connected to the negative output terminal of the dc bus, the collector of the transistor Q1 is connected to the other end of the transformer T1 home winding, one end of the secondary winding of the transformer T1 is connected to the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the negative electrode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is connected to one end of the capacitor C1 and one end of the resistor R1, and the other end of the resistor R1 is connected to the other end of the capacitor C1, the positive electrode of the diode D2, and the secondary.
preferably, the power switching controller comprises at least two-way relay.
Preferably, the insulation monitoring device comprises an insulation monitor.
Preferably, the insulation monitor comprises a detection circuit, a processor and an alarm indicating circuit, wherein the input end of the detection circuit is connected with the direct current bus, and the output end of the detection circuit is connected with the alarm indicating circuit through the processor.
correspondingly, the direct current grounding judgment method for the power distribution network with the voltage of below 35kV comprises the following steps:
s101, respectively connecting a DC/DC power supply module and an insulation monitoring device in parallel with a direct current bus;
And S102, connecting the output end of the power supply switching controller with the wiring terminals of different branches to be tested in parallel.
S103, the power supply switching controller switches the branch to be tested to a DC/DC power supply module for supplying power;
s104, disconnecting a branch switch on the branch to be tested;
s105, detecting the voltage to ground of the system by the insulation monitoring device;
s106, judging whether the voltage to the ground of the system is in a balanced state, if so, executing a step S107, otherwise, returning to the step S103;
And S107, determining that the branch to be tested is grounded, and ending the test.
Preferably, the determining whether the voltage to ground of the system is in a balanced state specifically includes: the positive voltage to ground and the negative voltage to ground are detected by an insulation monitoring device, and the voltage values of the positive voltage to ground and the voltage values of the negative voltage to ground are equal to each other, namely the voltage is in a balanced state, otherwise, the voltage is unbalanced.
Preferably, when the grounding judgment is performed on the branches to be tested, the judgment range is narrowed by adopting a dichotomy.
Preferably, the narrowing the determination range by the bisection method specifically includes:
S101, dividing a branch to be tested into a front half branch and a rear half branch;
S102, connecting the front half branch in parallel with the output end of the power supply switching controller;
S103, disconnecting a branch switch which is connected with the direct-current bus in parallel on the front half branch;
S104, detecting the voltage to ground of the system by the insulation monitoring device;
S105, judging whether the voltage to earth of the system is in a balanced state, if so, executing a step S106, otherwise, executing a step S107;
s106, setting the former half branch as a branch to be tested, and continuing to execute the step S101 until a grounding branch is determined;
And S107, setting the second half branch as a branch to be tested, and continuing to execute the step S101 until the grounding branch is determined.
correspondingly, the direct current grounding judgment method for the power distribution network with the voltage of below 35kV is characterized by comprising the following steps: the method comprises the following steps:
S101, connecting a plurality of DC/DC power supply modules with a direct current bus in parallel respectively;
S102, connecting a plurality of insulation monitoring devices in parallel with the output end of the DC/DC power supply module respectively;
s103, closing a branch switch on a to-be-tested branch connected with the direct current bus in parallel;
s104, detecting the voltage to ground of the system by the insulation monitoring device;
s105, judging whether the voltage to ground of each branch is in a balanced state;
and S106, determining a grounding branch and finishing the test.
compared with the prior art, the invention has the following beneficial effects:
The direct current grounding judgment device and the judgment method for the power distribution network below 35kV have the advantages that the device cost is low, the detection speed of the judgment method is high, and after the new power supply is connected with the original system circuit in parallel, the branch of the original system is disconnected, so that the rear end equipment of the branch cannot be powered off, and the power supply reliability is ensured; after the branch is detected to be in the isolated state with the original system after the direct current grounding of the branch is detected, the operation of the grounding branch is isolated, the operation risk of other equipment is reduced, direct current grounding judgment can be intuitively and accurately carried out on the premise of ensuring the safety, the misjudgment probability is reduced, and the method is suitable for popularization and application.
drawings
Fig. 1 is a schematic structural diagram of a dc grounding determination apparatus for a distribution network with a voltage of 35kV or less according to an embodiment of the present invention;
Fig. 2 is a schematic structural diagram of a dc grounding judgment device for a distribution network with a voltage of below 35kV according to another embodiment of the present invention;
FIG. 3 is a circuit block diagram of a DC/DC power module according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of a dc grounding determination method for a distribution network with a voltage of below 35kV according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart of the dichotomy test in the embodiment of the invention;
Fig. 6 is a schematic flowchart of a dc grounding determination method for a distribution network with a voltage of less than 35kV according to another embodiment of the present invention;
in the figure: the device comprises an insulation monitoring device 1, a DC/DC power supply module 2, a power supply switching controller 3, a branch switch 4 and a wiring terminal 5.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments, but not all embodiments, of the present invention; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
as shown in fig. 1, a DC grounding judgment device for a power distribution network below 35kV includes an insulation monitoring device 1, a DC/DC power module 2, and a power switching controller 3, where the insulation monitoring device 1 is connected in parallel with a DC bus, the DC bus is connected in parallel with a plurality of branches, each branch is connected in series with a branch switch 4 and a connection terminal 5, the connection terminal 5 is electrically connected to the DC bus through the branch switch 4, an input end of the DC/DC power module 2 is electrically connected to the DC bus, an output end of the DC/DC power module 2 is electrically connected to an input end of the power switching controller 3, and an output end of the power switching controller 3 is electrically connected to the connection terminal 5 on each branch.
specifically, a plurality of branches are connected with a direct current bus through a direct current feeder screen, the input end of the DC/DC power module 2 is connected with the direct current bus in parallel, and the direct current bus is connected with the DC/DC power module through a power supply 1: the power supply switching controller 3 can realize the communication of the input ends with different output ends through control, so that a plurality of branches are supplied with power by the new power supply converted by the DC/DC power supply module 2 through the power supply switching controller 3.
When the system is used, on the premise that the insulation monitoring device 1 and the DC/DC power supply module 2 are respectively connected with the direct current bus in parallel and the power supply switching controller 3 is connected with the wiring terminals 5 on the plurality of branches, the power supply switching controller 3 switches the power supply of the branch to be tested to a new power supply converted by the DC/DC power supply module 2 for supplying power, the branch switch 4 of the first branch to be tested is disconnected, the voltage to ground of the system is detected through the insulation monitoring device 1, if the voltage to ground of the system is in a balanced state, namely, whether the positive and negative voltage values of the system to ground are close to or equal to each other is detected, and if the positive and negative voltage values of the system to ground are close to or equal to each other; if the positive and negative voltage values of the system to the ground voltage are not close or equal, the first branch is not grounded, so that the judgment of the second branch is continued, when the judgment of the second branch is performed, the branch switch 4 on the first branch is closed, the new power supply provided by the DC/DC power supply module 2 is disconnected through the power supply switching controller 3, so that the first branch is powered by the DC bus, the power supply switching controller 3 switches the power supply of the second branch to the new power supply converted by the DC/DC power supply module 2 for power supply, the branch switch 4 of the second branch to be tested is disconnected, the ground voltage of the system is detected through the insulation monitoring device 1, if the ground voltage of the system is in a balanced state, if the positive and negative voltage values of the system to the ground voltage are close or equal, the second branch is grounded, otherwise, so that the judgment of the third branch is continued according to the method, until a ground branch is detected.
as shown in fig. 2, a direct current grounding judgment device for a power distribution network below 35kV includes a plurality of insulation monitoring devices 1 and DC/DC power modules 2, an input end of each DC/DC power module 2 is electrically connected to a DC bus, an output end of each DC/DC power module 2 is electrically connected to a load sequentially through a branch switch 4 and a connection terminal 5 on the DC bus, and the insulation monitoring devices 1 are connected in parallel to output ends of the DC/DC power modules 2.
When the device is used, the plurality of DC/DC power supply modules 2 are respectively connected with the DC bus in parallel, the plurality of insulation monitoring devices 1 are respectively connected with the output end of the DC/DC power supply modules 2 in parallel, the branch switch 4 on the branch to be tested which is connected with the DC bus in parallel is closed, and the insulation monitoring devices 1 start to detect the voltage to ground of the system; when the insulation monitoring device 1 detects that the positive and negative voltage values of the system to the ground voltage are close to or equal to each other, the branch circuit is confirmed to be grounded, and the test is finished; the DC/DC power supply module 2 is arranged on each branch, so that the problems of tripping of a circuit breaker, direct short circuit of a direct current power supply and the like caused by two-point grounding of different branches of a power system can be effectively avoided, the damage of the direct current system caused by two-point grounding of different branches can be avoided, each branch is connected on a direct current bus in parallel through the DC/DC conversion module 2, each branch mutually independently forms a group of new power supply and independently operates with each branch, when two different branches are simultaneously grounded at one point, the problems of tripping of the circuit breaker, direct short circuit of the direct current power supply and the like caused by the system which causes the misoperation of the signal device, the control circuit and the relay protection device caused by the two branches which are independent from the direct current bus can be avoided, and the detection can be simultaneously carried out on each branch, the detection efficiency is improved, and the practicability is strong.
further, as shown in fig. 3, the DC/DC power module 2 includes an inductor L1, a transformer T1, and a transistor Q1, one end of the inductor L2 is respectively connected to the positive output terminal of the DC bus, one end of the reset winding of the transformer T1, and one end of the home position winding of the transformer T1, the other end of the reset winding of the transformer T1 is connected to the negative electrode of the diode D3, the positive electrode of the diode D3 and the emitter of the transistor Q1 are respectively connected to the negative output terminal of the DC bus, the collector of the transistor Q1 is connected to the other end of the home position winding of the transformer T1, one end of the secondary winding of the transformer T1 is connected to the positive electrode of the diode D1, the negative electrode of the diode D1 is respectively connected to the negative electrode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is respectively connected to one end of the capacitor C1 and one end of the resistor R1, and the other end of the resistor, The other end of the secondary winding of the transformer T1 is connected; specifically, the triode Q1 is a switching tube and works in a PWM manner, the diode D1 is a rectifier diode, the diode D2 is a freewheeling diode, the inductor L1 is an output filter capacitor, when the branch to be tested is switched to the new power supply provided by the DC/DC power module 2 through the power switching controller 3 to supply power, the triode Q1 is turned on, the iron core flux increment of the transformer T1 and the current of the inductor L1 are increased, the input end of the branch switch 4 is connected in parallel to the two ends of the resistor R1, and at this time, the new power supply provided by the DC/DC power module 2 supplies power.
preferably, the power switching controller comprises at least two-way relay.
Preferably, the insulation monitoring device comprises an insulation monitor; the insulation monitor comprises a detection circuit, a processor and an alarm indicating circuit, wherein the input end of the detection circuit is connected with a direct current bus, and the output end of the detection circuit is connected with the alarm indicating circuit through the processor; when the insulation monitor detects that the positive and negative voltage values of the system to the ground voltage are close to or equal to each other, an alarm is sent out to prompt a worker that the secondary branch is a single-phase grounding branch, and fault treatment is carried out in time; specifically, when the branch circuit to be tested is switched to a new power supply provided by the DC/DC power supply module 2 for power supply, the insulation monitor starts to detect, the detection circuit detects positive and negative voltage values of the system to the ground voltage and sends the positive and negative voltage values to the processor, the processor compares whether the absolute values of the detected positive and negative voltage values are equal, if the absolute values of the detected positive and negative voltage values are equal, an alarm signal is sent to the alarm indicating circuit to prompt a worker to process the voltage values in time, and if the absolute values of the detected positive and negative voltage values are not equal, the alarm signal is not sent.
In the embodiment, a multimeter can be used for replacing the insulation monitoring device to test the positive and negative voltage values of the system to the ground voltage.
As shown in fig. 4, a method for determining dc grounding of a distribution network with a voltage of 35kV or less includes:
S101, respectively connecting a DC/DC power supply module and an insulation monitoring device in parallel with a direct current bus;
and S102, connecting the output end of the power supply switching controller with the wiring terminals of different branches to be tested in parallel.
s103, the power supply switching controller switches the branch to be tested to a DC/DC power supply module for supplying power;
S104, disconnecting a branch switch on the branch to be tested;
S105, detecting the voltage to ground of the system by the insulation monitoring device;
S106, judging whether the voltage to the ground of the system is in a balanced state, if so, executing a step S107, otherwise, returning to the step S103;
And S107, determining that the branch to be tested is grounded, and ending the test.
Preferably, the determining whether the voltage to ground of the system is in a balanced state specifically includes: the positive voltage to ground and the negative voltage to ground are detected by an insulation monitoring device, and the voltage values of the positive voltage to ground and the voltage values of the negative voltage to ground are equal to each other, namely the voltage is in a balanced state, otherwise, the voltage is unbalanced.
further, as shown in fig. 5, when the grounding judgment is performed on the multiple branches to be tested, a bisection method is adopted to reduce the judgment range; the adoption of the dichotomy to narrow the judgment range specifically comprises the following steps:
S101, dividing a branch to be tested into a front half branch and a rear half branch;
S102, connecting the front half branch in parallel with the output end of the power supply switching controller;
S103, disconnecting a branch switch which is connected with the direct-current bus in parallel on the front half branch;
S104, detecting the voltage to ground of the system by the insulation monitoring device;
s105, judging whether the voltage to earth of the system is in a balanced state, if so, executing a step S106, otherwise, executing a step S107;
s106, setting the former half branch as a branch to be tested, and continuing to execute the step S101 until a grounding branch is determined;
and S107, setting the second half branch as a branch to be tested, and continuing to execute the step S101 until the grounding branch is determined.
specifically, in the embodiment, when the grounding judgment is performed on the multiple branches to be detected, the judgment range is narrowed by adopting a bisection method; for example, when 50 branches to be tested need to be tested whether to be in a balanced state, 1 to 25 branches are tested first, if a system in the 25 branches has a balanced state with respect to the ground voltage, the 25 branches are set as branches to be tested and divided into 1 to 12 branches and 13 to 25 branches, the system in the 1 to 12 branches has a balanced state with respect to the ground voltage, and so on until a ground branch is detected.
In this embodiment, a dichotomy principle is adopted, the power switching controller 3 switches the power supply of the first half branch of the total test branch to a new power supply converted by the DC/DC power supply module 2 to supply power, switches off the branch switch 4 of the first half branch, detects the voltage to ground of the system through the insulation monitoring device 1, determines whether the voltage to ground of the system is in a balanced state, that is, detects whether the positive and negative voltage values of the voltage to ground of the system are close or equal, and if the positive and negative voltage values of the voltage to ground of the system are close or equal, determines that a branch grounding condition exists in the first half branch of the total test branch; continuously reducing the detection range according to the method until the grounding branch is detected; if the positive and negative voltage values of the system of the first half branch circuit to the ground voltage are not close or not equal, the first half branch circuit is not grounded, so that the judgment of the second half branch circuit of the total test branch circuit is continued until the grounded branch circuit is detected, and the detection method is as described above and is not repeated. After the direct current grounding of the branch is detected, the branch is in an isolated state with the original system, the grounding branch is isolated from running, the running risk of other equipment is reduced, direct current grounding judgment can be intuitively and accurately carried out on the premise of ensuring safety, and the misjudgment probability is reduced.
as shown in fig. 6, a method for determining dc grounding of a distribution network with a voltage of 35kV or less includes:
s101, connecting a plurality of DC/DC power supply modules with a direct current bus in parallel respectively;
s102, connecting a plurality of insulation monitoring devices in parallel with the output end of the DC/DC power supply module respectively;
S103, closing a branch switch on a to-be-tested branch connected with the direct current bus in parallel;
s104, detecting the voltage to ground of the system by the insulation monitoring device;
S105, judging whether the voltage to ground of each branch is in a balanced state;
and S106, determining a grounding branch and finishing the test.
when the device is used, the plurality of DC/DC power supply modules 2 are respectively connected with the DC bus in parallel, the plurality of insulation monitoring devices 1 are respectively connected with the output end of the DC/DC power supply modules 2 in parallel, the branch switch 4 on the branch to be tested which is connected with the DC bus in parallel is closed, and the insulation monitoring devices 1 start to detect the voltage to ground of the system; when the insulation monitoring device 1 detects that the positive and negative voltage values of the system to the ground voltage are close to or equal to each other, the branch circuit is confirmed to be grounded, and the test is finished; this embodiment can avoid the harm that different branch roads point-to-point ground caused to DC system, each branch road passes through DC/DC conversion module 2 and connects in parallel on direct current bus, and every branch road mutually independent forms a set of new power, with each branch road independent operation, when two different branch roads take place a little ground connection simultaneously, because two branch roads are independent relatively to direct current bus and can not arouse the system to cause the malfunction of signal device, control circuit and overload protection device, cause the circuit breaker tripping operation, or directly cause problems such as direct current power short circuit, and can detect simultaneously to individual branch road, and the detection efficiency is improved, and the practicality is extremely strong.
finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. the utility model provides a direct current ground connection judgement device for following distribution network of 35kV which characterized in that: the direct current bus insulation monitoring device comprises an insulation monitoring device, a DC/DC power supply module and a power supply switching controller, wherein the insulation monitoring device is connected with a direct current bus in parallel, a plurality of branches are connected on the direct current bus in parallel, a branch switch and a wiring terminal are connected on each branch in series, the wiring terminal is electrically connected with the direct current bus through the branch switch, the input end of the DC/DC power supply module is electrically connected with the direct current bus, the output end of the DC/DC power supply module is electrically connected with the input end of the power supply switching controller, and the output end of the power supply switching controller is electrically connected with the wiring terminal on each branch.
2. The utility model provides a direct current ground connection judgement device for following distribution network of 35kV which characterized in that: the DC/DC power supply module comprises a plurality of insulation monitoring devices and a DC/DC power supply module, wherein the input end of the DC/DC power supply module is electrically connected with a direct current bus, the output end of each DC/DC power supply module is electrically connected with a load through a branch switch and a wiring terminal on the direct current bus in sequence, and the insulation monitoring devices are connected with the output end of the DC/DC power supply module in parallel.
3. the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to claim 1 or 2, wherein: the DC/DC power supply module comprises an inductor L1, a transformer T1 and a triode Q1, one end of the inductor L2 is connected to the positive output terminal of the dc bus, one end of the transformer T1 reset winding, and one end of the transformer T1 home winding, the other end of the transformer T1 reset winding is connected to the negative electrode of the diode D3, the positive electrode of the diode D3 and the emitter of the transistor Q1 are connected to the negative output terminal of the dc bus, the collector of the transistor Q1 is connected to the other end of the transformer T1 home winding, one end of the secondary winding of the transformer T1 is connected to the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the negative electrode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is connected to one end of the capacitor C1 and one end of the resistor R1, and the other end of the resistor R1 is connected to the other end of the capacitor C1, the positive electrode of the diode D2, and the secondary.
4. the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to claim 1, wherein: the power supply switching controller comprises at least two paths of relays.
5. the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to any one of claims 1 or 2, wherein: the insulation monitoring device comprises an insulation monitor.
6. the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to claim 5, wherein: the insulation monitor comprises a detection circuit, a processor and an alarm indicating circuit, wherein the input end of the detection circuit is connected with the direct current bus, and the output end of the detection circuit is connected with the alarm indicating circuit through the processor.
7. A direct current grounding judgment method for a power distribution network with the voltage of below 35kV is characterized by comprising the following steps: the implementation of the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to claim 1 comprises the following steps:
S101, respectively connecting a DC/DC power supply module and an insulation monitoring device in parallel with a direct current bus;
And S102, connecting the output end of the power supply switching controller with the wiring terminals of different branches to be tested in parallel.
s103, the power supply switching controller switches the branch to be tested to a DC/DC power supply module for supplying power;
s104, disconnecting a branch switch on the branch to be tested;
S105, detecting the voltage to ground of the system by the insulation monitoring device;
s106, judging whether the voltage to the ground of the system is in a balanced state, if so, executing a step S107, otherwise, returning to the step S103;
and S107, determining that the branch to be tested is grounded, and ending the test.
8. the direct-current grounding judgment method for the distribution network with the voltage of below 35kV according to claim 7, characterized in that: the judging whether the voltage to ground of the system is in a balanced state specifically comprises the following steps: the positive voltage to ground and the negative voltage to ground are detected by an insulation monitoring device, and the voltage values of the positive voltage to ground and the voltage values of the negative voltage to ground are equal to each other, namely the voltage is in a balanced state, otherwise, the voltage is unbalanced.
9. the direct-current grounding judgment method for the distribution network with the voltage of below 35kV according to claim 7, characterized in that: when a plurality of branches to be tested are subjected to grounding judgment, the judgment range is narrowed by adopting a dichotomy,
The method specifically comprises the following steps:
S101, dividing a branch to be tested into a front half branch and a rear half branch;
s102, connecting the front half branch in parallel with the output end of the power supply switching controller;
S103, disconnecting a branch switch which is connected with the direct-current bus in parallel on the front half branch;
s104, detecting the voltage to ground of the system by the insulation monitoring device;
s105, judging whether the voltage to earth of the system is in a balanced state, if so, executing a step S106, otherwise, executing a step S107;
S106, setting the former half branch as a branch to be tested, and continuing to execute the step S101 until a grounding branch is determined;
and S107, setting the second half branch as a branch to be tested, and continuing to execute the step S101 until the grounding branch is determined.
10. A direct current grounding judgment method for a power distribution network with the voltage of below 35kV is characterized by comprising the following steps: the implementation of the direct-current grounding judgment device for the distribution network with the voltage of below 35kV according to claim 2 comprises the following steps:
s101, connecting a plurality of DC/DC power supply modules with a direct current bus in parallel respectively;
s102, connecting a plurality of insulation monitoring devices in parallel with the output end of the DC/DC power supply module respectively;
S103, closing a branch switch on a to-be-tested branch connected with the direct current bus in parallel;
S104, detecting the voltage to ground of the system by the insulation monitoring device;
s105, judging whether the voltage to ground of each branch is in a balanced state;
and S106, determining a grounding branch and finishing the test.
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