Voltage phase difference online monitoring and loop closing method and system based on magnetic control cabinet

Abstract

The invention discloses a voltage phase difference on-line monitoring and loop closing method and system based on a magnetic control cabinet, and belongs to the technical field of power grid on-line monitoring, and the method comprises the steps: arranging an electronic voltage sensor in the magnetic control cabinet, and collecting a voltage signal of a contact side and a voltage signal of an incoming line side; connecting the voltage signal of the contact side and the voltage signal of the wire inlet side output by the electronic voltage sensor to a distributed DTU; the distributed DTU calculates the voltage phase difference between the two sides of the loop closing point based on the voltage signal of the connection side and the voltage signal of the wire inlet side; and remotely transmitting the voltage phase difference of the two sides of the loop closing point to a master station system through a distributed DTU, thereby realizing real-time monitoring of the voltage phase difference of the 10kV power distribution network.

Description

Technical Field

[0001] The invention belongs to the technical field of online monitoring of power grids, and in particular relates to an online monitoring and loop closing method and system for voltage phase difference based on a magnetic control cabinet. Background Art

[0002] 10kV distribution network refers to the medium voltage distribution network in the power system that transmits electric energy from the substation to the end user. It consists of substations, distribution transformers, distribution lines, switchgear, etc. Its main characteristics are relatively short transmission distance and large load.

[0003] As an important part of the power system, the 10kV distribution network undertakes the key task of converting high-voltage electricity into low-voltage electricity and transmitting it to end users. With the continuous growth of electricity demand, the complexity and scale of the 10kV distribution network are also expanding. However, there are some technical difficulties in the operation of the traditional 10kV distribution network, the most prominent of which is that the existing 10kV distribution network does not have real-time phase monitoring function, and the voltage phase difference on both sides of the 10kV system closing point is difficult to obtain. Phase difference is an important electrical parameter in the power system. Especially when performing closing operation, if the voltage phase difference on both sides of the closing point cannot be accurately obtained, when the voltage phase difference is large, closing the loop may cause huge circulating current, resulting in equipment damage or even over-tripping, causing large-scale power outages.

[0004] The defects and shortcomings of the existing technology are: First, the focus of voltage phasors is different. Based on the phasor characteristics of voltage, under the premise that the voltage amplitude is not much different, the voltage phasor difference on both sides of the closing point depends more on the voltage phase difference, which is inconsistent with the current ring network cabinet that only collects the bus voltage amplitude. Second, the number of voltage quantity requirements is different. A conventional ring network cabinet can only extract a single bus voltage, while the voltage phase difference on both sides of the closing point requires the voltage phase data of the line (this end) and the line to be closed (the opposite end), which results in a data bottleneck. Third, the real-time requirements for data are different. The voltage phase difference can be monitored on-site using a phase volt-ampere meter through the terminal block and the core phase hole, but the result is still discrete data, and the closing switching strategy requires real-time and continuous voltage phase difference monitoring data, and the requirements do not match.

[0005] Therefore, for the analysis of closing-loop switching strategies, an online monitoring method for the voltage phase difference on both sides of the closing point, preferably an automatic voltage phase difference collection method using existing equipment without modification or with only a small amount of modification, needs to be studied urgently. Summary of the invention

[0006] The present invention provides a voltage phase difference online monitoring and loop closing method and system based on a magnetic control cabinet, which can realize the real-time monitoring function of the voltage phase difference of a 10kV distribution network.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for online monitoring of voltage phase difference based on a magnetic control cabinet, comprising the following steps: An electronic voltage sensor is installed in the magnetic control cabinet to collect the voltage signal on the connection side and the voltage signal on the incoming line side; Connecting the voltage signal on the connection side and the voltage signal on the incoming line side output by the electronic voltage sensor to the same distributed DTU; The distributed DTU calculates the voltage phase difference between the two sides of the closing point based on the voltage signal on the contact side and the voltage signal on the incoming line side; The voltage phase difference on both sides of the closing point is remotely transmitted to the main station system.

[0008] Furthermore, the arrangement of the electronic voltage sensor in the magnetic control cabinet includes: installing the high-voltage capacitor of the electronic voltage sensor in phases on the insulating plug cover of the cable terminal accessory, and inputting it into the data acquisition box through a two-core aviation plug and a shielded cable, outputting three-phase voltage signals respectively after voltage division by a low-voltage capacitor, and connecting it to the distributed DTU through a five-core aviation plug and a shielded cable.

[0009] Furthermore, the distributed DTU supports collecting and sending AC voltage signals, and has the function of calculating the voltage phase difference locally, and can transmit the calculation results remotely to the main station system.

[0010] Furthermore, the distributed DTU transmits the voltage phase difference between the two sides of the closing point to the master station system via the 104 protocol.

[0011] Furthermore, it also includes a simulated transmission test on the distributed DTU to verify the simultaneity of its voltage phase difference calculation and discrete digital signal acquisition.

[0012] In a second aspect, the present invention provides a voltage phase difference online monitoring system based on a magnetic control cabinet, comprising: Electronic voltage sensor, installed in each cable compartment of the magnetic control cabinet, is used to collect the voltage signal on the contact side and the voltage signal on the incoming line side; The distributed DTU is installed in the normally open interval of the magnetic control cabinet, receives the voltage signal of the connection side and the voltage signal of the incoming line side collected by the EVT, and calculates the voltage phase difference on both sides of the closing point based on the voltage signal of the connection side and the voltage signal of the incoming line side, and transmits the voltage phase difference on both sides of the closing point to the master station system.

[0013] Furthermore, it also includes a master station system for receiving and displaying voltage phase difference data transmitted remotely by the distributed DTU.

[0014] Furthermore, the master station system assists in determining the closed-loop current value.

[0015] Furthermore, it also includes a data acquisition box supporting the EVT. The low-voltage capacitor in the data acquisition box outputs three-phase voltage signals respectively after voltage division, and is connected to the distributed DTU through an aviation plug and a control cable.

[0016] In a third aspect, the present invention provides a distribution network closing method, comprising the following steps: Step 1: Perform power flow calculation on the closed loop operation, and determine the time period of the closed loop operation based on the power grid power flow calculation result; Step 2: Use the voltage phase difference online monitoring method described in claim 1 to monitor the voltage phase difference on both sides of the closing point. When the phase difference satisfies that the difference between the voltage vectors on both sides of the closing point is less than 10% of the rated voltage of the distribution network, perform the closing operation.

[0017] Compared with the prior art, the present invention has at least the following beneficial technical effects: The proposed method and system for online monitoring of two-terminal voltage phase difference based on magnetic control cabinets pioneered the use of magnetic control ring network cabinets (hereinafter referred to as magnetic control cabinets) in combination with electronic voltage sensors and distributed DTUs to achieve the real-time monitoring function of the voltage phase difference of the 10kV distribution network. The distributed DTUs synchronously collect the voltage signals on the contact side and incoming line side output by the electronic voltage sensors of the current interval and the adjacent normally closed intervals, and the distributed DTUs calculate the voltage phase difference on both sides of the closing point on the spot based on the voltage signals on the contact side and incoming line side. The data is uploaded to the master station through the distributed DTU, and the master station obtains real-time and accurate voltage phase angle data of the closing point, providing data support for the closing operation.

[0018] The closing method proposed in the present invention provides continuous observable and measurable data of the phase difference and amplitude difference of the voltages on both sides of the closing point, so that dispatching personnel can judge online whether the conditions for closing and switching are met, breaking through the difficult problems of blind closing and switching, or the difficulty in extending the closing time period based on operating experience, and has the advantages of strong real-time performance and high accuracy.

[0019] The advantages of the present invention include: 1) Strong feasibility. Relying on the electronic voltage sensor of the magnetic control cabinet and the distributed DTU, the voltage phase difference and amplitude difference of the 10kV line closing point are sent by means of power distribution automation, which requires less modification of the equipment itself and can provide online, continuous and reliable data indicators for real-time closing and switching strategies.

[0020] 2) High safety. Automated monitoring and collection methods replace manual on-site measurement, saving manpower input costs and avoiding personal and equipment safety issues caused by on-site measurement.

[0021] 3) Weak dependence on timing. Compared with the main network PMU method, the present invention collects the voltage phase of two sets of EVTs on the incoming line side and the contact side on-site through one set of distributed DTU, ensuring the unified time of the voltage phase data collected by the two sets of EVTs. There is no need for the main network PMU to synchronize with the satellite or the station-side time synchronization device, the method is simple and saves investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the connection diagram between the EVT body and the data acquisition box; Figure 2 This is a three-dimensional picture of the EVT high-pressure plug body; Figure 3 Schematic diagram of the data acquisition box for EVT; Figure 4 This is a schematic diagram of a five-core shielded cable; Figure 5 A schematic diagram of a phase difference monitoring system provided by the present invention; Figure 6 This is a schematic diagram of the distributed DTU backplane wiring; Figure 7 This is the real-time voltage phase monitoring function test diagram; Figure 8 It is a magnetic control cabinet with real-time voltage phase monitoring function; Fig. 9 A flow chart of a method for online monitoring of voltage phase difference based on a magnetic control cabinet provided by the present invention; Fig.10 A flow chart of a 10kV distribution network closing method provided by the present invention; Fig.11 This is the monitoring result of the phase difference of phase A of a certain transformer on a certain line; Fig.12 This is the monitoring result of the phase difference of the voltage phase C of a certain box-type transformer on a certain line; Fig.13 Monitoring results of Ua voltage phase difference at closing points of 4 ring main units on different lines; Fig.14 It is the voltage telemetry value of distributed DTU; Fig.15 is the voltage phase angle telemetry value of the distributed DTU; Fig.16 It is the voltage angle difference telemetry value of the distributed DTU.

[0023] In the attached figure: 1. Electronic voltage sensor; 2. Data acquisition box; 3. Shielded cable; 4. Cable room; 5. Mechanism room; 6. Secondary instrument room; 7. Communication box. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. used herein indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0028] According to the actual situation of the hybrid line and the status of the equipment on both sides of the closing point, this solution uses a magnetic control cabinet and is equipped with an electronic voltage sensor 1 (EVT for short) and distributed DTU (Distributed Terminal Unit) technology to achieve the real-time monitoring function of the phase difference of the 10kV closing point. The distributed DTU of the normally open interval selected by the magnetic control cabinet is updated with a new program, and the voltage signal output by the EVT of this interval is connected to the DTU through the terminal block as the contact side voltage signal, and the voltage signal output by the EVT of the adjacent normally closed interval (contact side) is connected to the DTU as the incoming line side voltage signal, so as to realize the monitoring function of the voltage phase difference on both sides of the closing point.

[0029] Example 1 Reference Figure 8This embodiment provides a voltage phase difference online monitoring system based on a magnetic control cabinet, including a magnetic control cabinet, the magnetic control cabinet including a plurality of compartments, the plurality of compartments including at least an incoming line side compartment and a communication side compartment; each compartment is, from bottom to top, a cable room 4, a mechanism room 5, a secondary instrument room 6 and a communication box 7.

[0030] The cable room 4 is used for cable connection, EVT installation and data acquisition box 2 installation. The mechanism room 5 is used to place the operating mechanism and interlocking device. The secondary instrument room 6 is used for switch position indication, switch closing and opening operation, remote local position control, protection push and distributed DTU three-remote control and terminal block transfer. The distributed DTU is located in the secondary instrument room 6, and the communication box 7 is used to collect and transmit the distributed DTU information to the master station system. The distributed DTU supports the collection and transmission of AC voltage signals, and has the function of calculating the voltage phase difference locally, and can transmit the calculation results to the master station system.

[0031] The magnetic control cabinet provided in this embodiment has six compartments.

[0032] Reference Figure 5 Three EVTs are installed in the incoming line side compartment, which are used to collect the three-phase voltage on the incoming line side, and the output ends of the three EVTs are connected to the input end of a data acquisition box 2; three EVTs are installed in the communication side compartment, which are used to collect the three-phase voltage on the communication side, and the output ends of the three EVTs are connected to the input end of another data acquisition box 2; the output ends of the two data acquisition boxes 2 are connected to the input end of the distributed DTU through a shielded cable 3, and the distributed DTU interacts with the master station through a communication box 7.

[0033] Example 2 Reference Fig. 9 This embodiment provides a method for online monitoring of voltage phase difference based on a magnetic control cabinet, comprising the following steps: S1. Perform a simulated transmission test on the distributed DTU to verify the simultaneity of its voltage phase difference calculation and discrete digital signal acquisition; if the verification is passed, execute S2; if the verification fails, find out the problem and solve it until the verification is passed; S2, installing an electronic voltage sensor and a data acquisition box 2 in the magnetic control cabinet to collect the voltage signal of the contact side and the voltage signal of the incoming line side; The installation of the electronic voltage sensor and the data acquisition box 2 includes: installing the high-voltage capacitors in phases on the insulating plugging cover of the cable terminal accessories, and inputting them into the data acquisition box 2 through a two-core aviation plug and a shielded cable 3, outputting three-phase voltage signals respectively after voltage division by a low-voltage capacitor, and connecting them to the distributed DTU through a five-core aviation plug and a shielded cable 3.

[0034] S3, the voltage signal of the connection side and the voltage signal of the incoming line side output by the electronic voltage sensor are transmitted to the distributed DTU through the data acquisition box 2 and the shielded cable 3; S4, distributed DTU calculates the voltage phase difference on both sides of the closing point based on the voltage signal on the contact side and the voltage signal on the incoming line side; S5. The voltage phase difference on both sides of the above-mentioned closing point is transmitted to the main station system via the communication box 7 through the 104 protocol.

[0035] Example 3 Reference Fig.10 This embodiment provides a 10kV distribution network closing method, comprising the following steps: Step 1: Perform dispatcher power flow calculation for the closed-loop operation and keep records; through dispatcher power flow calculation, when the power grid power exceeds the thermal stability limit during the closed-loop operation, the operation should be performed during the load valley period (0:00~6:00).

[0036] Step 2: monitor the voltage phase difference on both sides of the closing point according to the method of Example 2. When the phase difference satisfies that the difference between the voltage vectors on both sides of the closing point is less than 10% of the rated voltage of the distribution network, perform the closing operation.

[0037] This solution performs functional tests on the contact-side EVT and distributed DTU to verify the feasibility of the solution: 1. Electronic voltage sensor (EVT) test The EVT is arranged in each cable compartment of the magnetic control cabinet. The high-voltage capacitors of the EVT are installed in phases (A, B, and C) in the insulating plug cover of the cable terminal accessories. The structure is supported by the cable terminal screw. Figure 1 and Figure 2 .

[0038] The input end of the supporting data acquisition box and the output end of the high-voltage capacitor (A, B, C phases) in the insulating plug cover of this compartment are connected through an aviation plug and a shielded cable. After the low-voltage capacitor in the data acquisition box divides the voltage, the A, B, C three-phase secondary voltage signals are output. They are led to the secondary instrument room terminal block through the aviation plug and the five-core shielded cable and then connected to the distributed DTU voltage acquisition. Figure 3 and Figure 4 .

[0039] The introduction of EVT on the contact side makes it possible to collect and calculate voltage phase signals at different intervals.

[0040] This plan relies on the test platform to develop a single EVT test plan for the magnetic control cabinet. The test environment was organized to complete the construction, test the EVT accuracy and anti-zero drift performance in the magnetic control cabinet, and introduce a standard transformer as a control group. The whole process tracked the EVT and standard mutual voltage (full voltage, undervoltage, overvoltage) measurement to carry out group and phase tests. The test results showed that the EVT secondary voltage accuracy did not exceed 4' (ie 0.067°), verifying that the EVT measurement performance meets the voltage phase difference acquisition function requirements on both sides of the loop point. Combined with the factory inspection, the two magnetic control cabinets were technically modified to complete the dynamic transmission and verification of the voltage monitoring function with the master station.

[0041] (II) Distributed DTU simulation transmission test According to the "Distribution Automation Remote Terminal" (DL / T 721-2013) and "Telecontrol Equipment and Systems" (DL / T634.5104), distributed DTU supports the collection and transmission of AC voltage and supports 104 protocol remote transmission.

[0042] Reference Figure 5 and Figure 6 , the introduction of distributed DTU is to collect EVT secondary voltage in real time for voltage phase signal and send it to the master station to meet the conditions for distribution automation. This scheme is aimed at distributed DTU. First, from the perspective of voltage phase difference calculation and discrete digital signal acquisition simultaneity, it proposes a scheme to introduce two EVT acquisitions (one set of EVT refers to high-voltage plug + data acquisition box) voltage signals into the same distributed DTU to avoid the problem of incorrect data synchronization caused by the communication delay of different DTUs. Second, the distributed DTU of the magnetic control cabinet contact switch is selected to access the two EVT voltage signals, aiming to ensure that there is no false tripping during the operation interval, while minimizing the workload of the transformation. Third, a "relay protection tester-terminal block-distributed DTU-master station voltage phase difference (telemetry)" test environment is built to complete the distributed DTU simulation transmission.

[0043] Reference Figure 7 The phase volt-ampere meter and the distributed DTU core unit are connected to the output end of the 6U6I relay protection tester. The 6U6I relay protection tester is used to simulate various voltage, current, phase, frequency, harmonic and other parameters in the power system to test the sampling accuracy of the analog quantity of the distribution terminal DTU; it can simulate different types of faults such as short circuit and single-phase ground barrier to verify the reliability and correctness of the protection and automation functions of the distribution terminal. In this design, it is used to output a known voltage signal to the distributed DTU core unit to verify the voltage difference and phase difference on both sides of the closing point.

[0044] Phase volt-ampere meter is used to measure the phase difference between the analog output channels of the relay protection tester and serves as a standard meter for phase monitoring.

[0045] The distributed DTU core unit is used to collect the voltage amplitude and phase of the incoming line side in real time, and calculate the absolute value of the voltage difference and the absolute value of the angle difference between the same-phase voltages on both sides, and transmit the collected and calculated data to the main station, compare the calculated results with the measurement results of the phase volt-ampere meter, and calculate the angle difference accuracy; when the pressure difference and angle difference are met, the closing point switch is allowed to close.

[0046] If the voltage amplitude and phase received by the master station are the same as the voltage amplitude and phase output by the phase volt-ampere meter, and the absolute value of the voltage difference and the absolute value of the angle difference between the same-phase voltages on both sides received by the master station match the voltage amplitude and phase output by the phase volt-ampere meter, it proves that the distributed DTU can accurately collect and calculate the phase difference of the two introduced voltages on-site.

[0047] It has been confirmed through transmission that the distributed DTU can calculate the phase difference of the two introduced voltages on-site and transmit the phase difference to the master station.

[0048] (III) Transmission test of the whole group Reference Figure 7 and Figure 8 The above has completed the separate test of EVT voltage phase acquisition and distributed DTU voltage phase remote transmission. On this basis, this solution is based on actual equipment to complete the factory inspection of the voltage phase difference of the entire transmission.

[0049] Before transmission, the NARI distribution network OPEN 5200 system master station diagram maintenance was completed according to the new equipment startup data, and the on-site equipment address was adapted. During transmission, the master station system collected the voltage phase difference information sent by the magnetic control cabinet and displayed it in the system graphics and telemetry value real-time monitoring table. After dynamic transmission by the master and plant automation personnel, it was proved that the magnetic control cabinet can accurately and timely send the voltage telemetry value signal to the master station.

[0050] According to the above test data, after preliminary verification, the voltage phase difference monitoring solution based on the magnetic control cabinet is basically feasible. The solution has the following characteristics: (1) Data accuracy. The magnetic control cabinet is equipped with various EVT tests to ensure the accuracy of voltage phase data collection and anti-zero drift performance, and can reliably determine the voltage phase difference information on both sides of the closing point.

[0051] (2) Data synchronization. The solution introduces the voltage phase information on both sides of the loop point into the same distributed DTU. Except for the inherent AD channel conversion delay of the DTU device itself, the simultaneity of the data on both sides of the loop point is guaranteed.

[0052] (3) Data continuity. The distributed DTU transmits voltage phase difference information remotely in real time, which can not only capture the 10kV voltage phase difference information between different partitions in real time, but also provide continuous data samples for the voltage difference on both sides of the closing point.

[0053] In order to solve the problem that there is no means of voltage phase monitoring at the closing point of the 10kV distribution network, this solution has conducted targeted and systematic research and exploration on the closing monitoring method of the 10kV distribution network. At present, through the replacement or upgrading of the original equipment, multiple magnetic control cabinets with voltage phase difference online monitoring functions have been installed and debugged on different lines. This solution is based on the characteristics of the magnetic control cabinet equipped with electronic voltage sensors on the contact side and distributed DTU equipment, and innovatively realizes the first attempt of voltage phase difference monitoring of magnetic control cabinet equipment.

[0054] So far, the specific implementation of this scheme has successfully opened the "first observation window" for continuous monitoring of the voltage phase difference between closing points between different partitions.

[0055] The voltage phase difference monitoring and analysis was carried out by intercepting the data section of a certain day. The results are as follows: Fig.11 and Fig.12 As shown, it can be seen that the system can obtain the real-time voltage phase difference and record it.

[0056] On August 26, 2024, the Ua voltage phase difference of four magnetic control cabinets with different lines that have closed loop monitoring function was analyzed. The results are as follows: Fig.13 shown.

[0057] Voltage telemetry value such as Fig.14 As shown, the power supply side (also called the incoming line side) is the power supply of this cabinet, and the contact side is the power supply of the opposite cabinet. Calculation instructions: In the figure, Ua on the power supply side, Uc on the power supply side, Ua on the contact side, and Uc on the contact side are all real-time values, and the actual sampled values ​​are the same. For example, if Ua on the power supply side is 1V, Uc on the power supply side is 1V, Ua on the contact side is 1.5V, and Uc on the contact side is 1.5V, the actual sampled values ​​are also 1V on the power supply side and 1.5V on the contact side.

[0058] Voltage phase angle telemetry value Fig.15 As shown, the phase angle display range is: 0° to 180° normal display, 180° to 360° is displayed as -180° to 0°. Calculation instructions: UA phase angle on the power supply side, UC phase angle on the power supply side, UA phase angle on the contact side, the UC phase angle on the contact side is based on the UA phase angle on the power supply side, that is, the UA phase angle on the power supply side is always 0°, and the remaining phase angle display degrees are the real-time value minus the real-time value of the UA phase angle on the power supply side. For example, when the real-time value of the UA phase angle input on the power supply side is 10°, and the real-time value of the UC phase angle input on the power supply side is 20°, the UA phase angle on the power supply side is used as the reference value 0°, the UA phase angle display value on the power supply side is 0°, and the UC phase angle display value on the power supply side is 10° (such as Fig.15 ).

[0059] The voltage angle difference telemetry value is as follows Fig.16As shown, calculation instructions: the angle difference and voltage difference are the displayed values ​​of the connection side minus the power supply side. For example, the phase angle of UA on the power supply side is 10°, the phase angle of UA on the connection side is 12°, and the angle difference between the two sides of UA is 2°; the phase angle of UC on the power supply side is 20°, the phase angle of UC on the connection side is 22°, and the angle difference between the two sides of UA is 2°; when the input voltage of UA on the power supply side is 1V and the input voltage of UA on the connection side is 1.5V, the voltage difference between the two sides of UA is displayed as 0.5V; when the input voltage of UC on the power supply side is 1V and the input voltage of UC on the connection side is 1.5V, the voltage difference between the two sides of UC is 0.5V (such as Fig.16 ).

[0060] The term "consisting of" describing a combination shall include the identified elements, ingredients, parts or steps and other elements, ingredients, parts or steps that do not substantially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, parts or steps herein also contemplates embodiments that consist essentially of these elements, ingredients, parts or steps. By using the term "may", it is intended to illustrate that any of the attributes described that "may" be included are optional.

[0061] Multiple elements, ingredients, parts or steps can be provided by a single integrated element, ingredient, part or step. Alternatively, a single integrated element, ingredient, part or step can be divided into separate multiple elements, ingredients, parts or steps. The disclosure "one" or "an" used to describe an element, ingredient, part or step is not intended to exclude other elements, ingredients, parts or steps.

[0062] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the foregoing claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for online monitoring of voltage phase difference based on a magnetic control cabinet, characterized in that: The following steps are involved: An electronic voltage sensor is installed in the magnetic control cabinet to collect the voltage signal on the connection side and the voltage signal on the incoming line side; Connecting the voltage signal on the connection side and the voltage signal on the incoming line side output by the electronic voltage sensor to the same distributed DTU; The distributed DTU calculates the voltage phase difference between the two sides of the closing point based on the voltage signal on the contact side and the voltage signal on the incoming line side; The voltage phase difference on both sides of the closing point is remotely transmitted to the main station system.

2. The method for online monitoring of voltage phase difference based on a magnetic control cabinet according to claim 1 is characterized in that: The electronic voltage sensor is arranged in the magnetic control cabinet, including: installing the high-voltage capacitor of the electronic voltage sensor in phase on the insulating plug cover of the cable terminal accessory, and inputting it into the data acquisition box through a two-core aviation plug and a shielded cable, outputting three-phase voltage signals respectively after voltage division by a low-voltage capacitor, and connecting with the distributed DTU through a five-core aviation plug and a shielded cable.

3. The method for online monitoring of voltage phase difference based on a magnetic control cabinet according to claim 1 is characterized in that: The distributed DTU supports collecting and sending AC voltage signals, and has the function of calculating voltage phase difference on site, and can transmit the calculation results remotely to the main station system.

4. The method for online monitoring of voltage phase difference based on a magnetic control cabinet according to claim 1 is characterized in that: The distributed DTU transmits the voltage phase difference between the two sides of the closing point to the master station system via the 104 protocol.

5. The method for online monitoring of voltage phase difference based on a magnetic control cabinet according to claim 1 is characterized in that: It also includes simulated transmission testing of distributed DTUs to verify the simultaneity of voltage phase difference calculation and discrete digital signal acquisition.

6. A voltage phase difference online monitoring system based on a magnetic control cabinet, characterized in that: include: Electronic voltage sensor, installed in each cable compartment of the magnetic control cabinet, is used to collect the voltage signal on the contact side and the voltage signal on the incoming line side; The distributed DTU is installed in the normally open interval of the magnetic control cabinet, receives the voltage signal of the connection side and the voltage signal of the incoming line side collected by the EVT, and calculates the voltage phase difference on both sides of the closing point based on the voltage signal of the connection side and the voltage signal of the incoming line side, and transmits the voltage phase difference on both sides of the closing point to the master station system.

7. The voltage phase difference online monitoring system based on the magnetic control cabinet according to claim 6 is characterized in that: It also includes a master station system for receiving and displaying voltage phase difference data transmitted remotely by distributed DTUs.

8. The voltage phase difference online monitoring system based on the magnetic control cabinet according to claim 7 is characterized in that: The master station system assists in determining the closed-loop current value.

9. The voltage phase difference online monitoring system based on a magnetic control cabinet according to claim 6 is characterized in that: It also includes a data acquisition box that matches the EVT. The low-voltage capacitors in the data acquisition box output three-phase voltage signals respectively after voltage division, and are connected to the distributed DTU through an aviation plug and a control cable.

10. A distribution network closing method, comprising the following steps: Step 1: Perform power flow calculation on the loop closing operation, and determine the time period of the loop closing operation based on the power grid power flow calculation result; Step 2: Use the voltage phase difference online monitoring method described in claim 1 to monitor the voltage phase difference on both sides of the closing point. When the phase difference satisfies that the difference between the voltage vectors on both sides of the closing point is less than 10% of the rated voltage of the distribution network, perform the closing operation.

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