CN202189112U - Fault location system based on submarine cables and overhead lines - Google Patents

Abstract

A fault location system based on submarine cables and overhead lines. The system comprises an on-site monitoring device and a diagnosis system, wherein the on-site monitoring device is arranged at a first-stage tower at the junction of a submarine cable and an overhead line and comprises a power supply unit, a Rogowski coil current sensor unit, a data acquisition and processing unit and a communication unit. The communication units are connected with the power supply unit, the output end of the current sensor is connected to the input end of the data acquisition and processing unit, and the output end of the data acquisition and processing unit is connected to the input end of the communication unit; the field monitoring device establishes communication connection with the data center through a wireless communication technology; the diagnosis system comprises a data center and a management system, and the management system reads data from the data center to realize accurate positioning of a fault section.

Description

Fault location system based on submarine cables and overhead lines

technical field

The utility model relates to the field of fault location of electric power systems, in particular to the field of location of complex transmission line fault intervals.

Background technique

Transmission line fault tripping is one of the most frequent accidents in high-voltage power grids. In addition to impacting the system, each tripping accident will cause damage to insulators, wires and other facilities, leaving hidden dangers to system operation. Due to the inaccurate fault location, it takes a long time to find and repair the fault, which affects the timely restoration of power supply. These problems are more prominent problems in the production practice of high-voltage power grids. Especially for the transmission system combining overhead lines and submarine cables, the accuracy of fault zone location not only affects the efficiency of line operation and maintenance, but also serves as a parameter for the action of power system relay protection devices. Therefore, higher requirements are put forward for the location of transmission line fault intervals.

At present, there are mainly two types of methods for fault location of transmission lines in domestic power systems: one is line parameter location; the other is traveling wave location. The location of line parameters can be realized directly by using substation fault recording equipment, with a small investment, but the positioning principle is complex, and positioning is closely related to factors such as line parameter distribution, system operation mode, load size, and grounding conditions, and the positioning accuracy is generally not high, so it is difficult to apply In long-distance transmission lines; traveling wave positioning uses the traveling wave signal sent by the fault point to locate. Practical applications still face the influence of some practical factors beyond the theory, such as the error caused by the velocity change of traveling waves propagating in different media on the positioning accuracy, the influence of the attenuation and distortion of traveling wave waveform on positioning, etc.

Contents of the invention

The technical problem to be solved by the utility model is: in order to overcome the limitations of the line parameter positioning and traveling wave positioning methods, and realize the precise positioning of the complex transmission line fault interval combining overhead lines and submarine cables, the utility model provides a method based on submarine cables and Fault location system for overhead lines.

The technical scheme adopted by the utility model is: the fault location system based on submarine cables and overhead lines includes an on-site monitoring device and a diagnosis system. The on-site monitoring device is installed at the first-stage tower at the junction of the submarine cable and the overhead line, including a power supply unit, a Rogowski coil current sensor unit, a data acquisition and processing unit, and a communication unit. The communication unit is connected to the power supply unit, the output terminal of the current sensor is connected to the input terminal of the data acquisition and processing unit, and the output terminal of the data acquisition and processing unit is connected to the input terminal of the communication unit; the on-site monitoring device communicates with the data center through wireless communication technology Establish a communication connection; the diagnosis system includes a data center and a management system, and the management system reads data from the data center to accurately locate the fault area.

Compared with the prior art, the utility model has the beneficial effects of directly monitoring the fault current signal of the transmission line body, accurately identifying faults, only two monitoring terminals, and low cost. It can realize the statistics of lightning strike accident rules of transmission lines in sections, provide a basis for lightning protection, and realize the automation, intelligence and informatization of transmission line accident monitoring and statistics.

Description of drawings

Figure 1 shows the overall structure of the system.

Fig. 2 Schematic diagram of the Rogowski coil measuring current device.

Fig. 3 Schematic diagram of Rogowski coil structure.

Figure 4 is a structural diagram of the wireless communication unit.

Figure 5 is a block diagram of the power conversion circuit.

Figure 6 The structure diagram of the power supply unit.

Detailed ways

In Figure 1, the fault location system based on submarine cables and overhead lines includes on-site monitoring devices and diagnostic systems. The on-site monitoring device is installed at the first-stage tower at the junction of the submarine cable and the overhead line, including a power supply unit, a Rogowski coil current sensor unit, a data acquisition and processing unit, and a communication unit. The sensor coil detection unit is used for power frequency load current, power frequency fault current, traveling wave current signal detection, etc. The data collection and analysis unit collects, analyzes and diagnoses various signals detected by the sensor. The communication unit uploads the collected signal processing results, accepts the downlink parameters and control commands, directly uploads the information for the area covered by GPRS, and transmits the information to the adjacent signal area through the wireless data transmission module for the uncovered area and then uploads it through GPRS. The power system is the power guarantee system of the field terminal. The diagnosis system includes a data center and a management system. The management system reads data from the data center to accurately locate fault areas. Each component unit of this system is introduced in detail below.

In Fig. 3, it is a structural diagram of a Rogowski coil current sensor. The Rogowski coil is used as a sensor for current measurement to measure power frequency fault current and traveling wave current. The Rokosoff coil is a measuring device that determines the magnitude and direction of the current based on the magnetomotive force generated by the measured current. The principle of the current sensor unit is shown in Figure 2, which uses a Rogowski coil. Compared with the traditional electromagnetic transformer, the Rogowski current sensor has no iron core saturation problem, has transmission frequency bandwidth, and is resistant to Excellent interference performance, small size, light weight and other advantages. The current sensor unit has a frequency response characteristic of up to tens of megabytes, which converts the lightning current and power frequency fault current propagated on the transmission line conductor into signals that can be collected by the data acquisition and processing unit. The Rogowski coil winds the wire evenly on a non-ferromagnetic ring frame, and the primary busbar is placed in the center of the coil, so the potential between the winding coil and the busbar is isolated. Suppose the magnetic induction density is Φ(t), the bus current is I(t), the coil turns N, the coil cross-sectional area S, the coil radius r, and the time is t, then the induced electromotive force e(t) on the coil is:

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; d\&phi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&mu;NS</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;r</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; iGO</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

Where μ is air (or vacuum) magnetic permeability.

The data acquisition and processing unit is composed of a microprocessor module, a large-capacity storage unit, and a high-speed acquisition module. This functional unit requires the system to accurately collect power frequency load, fault current and traveling wave current signals, and then wirelessly transmit them to the monitoring center through the GPRS network. The microprocessor module uses the msp430 microprocessor with extremely low power consumption and rich functions. The power consumption in the sleep state is only 10mW, and its working voltage is only 3.3V. The power consumption is very low. A complex and fast operation, but also has a wealth of peripheral circuit expansion capabilities to meet the needs of system expansion. The high-speed acquisition unit is implemented by a programmable logic device FPGA+high-speed AD, which collects a large amount of traveling wave data and stores them in an external memory, and sends them to the data center. The microprocessor unit communicates with the wireless mobile phone module through the asynchronous serial port, and all data transmission and reception can be realized only by the microprocessor operating the wireless mobile phone module through the AT instruction set. The sending and receiving of data is only carried out between serial ports. In consideration of reducing the power consumption of the system, except for the real-time work of sensors and data acquisition and analysis, the wireless communication unit is in a dormant state. When a power frequency fault current signal or traveling wave current is detected, the high-speed acquisition unit continues to collect a Time, store the data in the large-capacity SRAM, and then start the wireless communication unit to upload the data to the monitoring center.

In FIG. 4, it is a design diagram of a wireless communication unit. Since the on-site monitoring device is far away from the urban area, it would be too costly to build our own private network. Based on this point, we use the mobile GSM/GPRS/CDMA public network to transmit data remotely. It has a wide coverage and a signal coverage rate of up to 98%, for very remote places (where there is no mobile network coverage), the wireless data transmission module can be used to transfer to places with signals and then communicate, thus ensuring the reliability of wireless communication, and it is convenient, economical, and maintenance-free. This communication method has been widely used, and it has been applied in our on-line monitoring project of insulation pollution of transmission lines that has been put into operation, and it is running well. The on-site monitoring device can promptly notify the remote monitoring system when there is a fault current or lightning current on the line, upload various necessary data information to the monitoring system to provide analysis data, and also accept various download commands and parameter settings from the monitoring system wait. This ensures the two-way data communication function between the on-site monitoring device and the remote monitoring system application software. As the wireless GPRS communication module, we choose the MC35 mobile phone module of Siemens in Germany, which has 232 interfaces. Both data collection and sending control are carried out by the microprocessor through the 232 interface using the AT command set. GSM/GPRS MODEM (TC-35 module) supports standard AT command set.

In FIG. 5, it is a block diagram of a power conversion circuit, and in FIG. 6, it is a schematic diagram of a power supply structure. The power supply system can meet the continuous and uninterrupted power supply in the field environment, avoids the cumbersome long-term maintenance, and has high reliability. Specific working method: within the normal range of current variation, the special iron core directly induces AC voltage from the primary side, and outputs 6-75V DC voltage after passing through the front-end impact protection circuit and rectification and filtering circuit to provide enough energy for the back-end system . When the primary side current is small and the induced power cannot meet the needs of the back-end acquisition system, use the power management module to adjust the power supply of lithium batteries and super capacitors; when the primary side current is large, the induced power greatly exceeds the back-end acquisition system When needed, voltage sampling and protection circuits can be used to ensure the safe operation of the back-end acquisition system. At the same time, the power management module can be used to charge and store capacitors and batteries for use when the induction power is insufficient. When a short-circuit fault occurs on the primary side, the transient current will generate an inrush current in the induction coil, but after multiple protections by the front-end impact protection circuit and subsequent circuits, the voltage value input to the DC/DC module can be clamped to The allowable voltage is within 75V, which protects the safety of the back-end electronic circuit.

The upper computer management system is located at the workstation of the on-duty personnel. It can access the data recorded by the on-site monitoring device in the data center and locate the fault area accurately. The specific method is as follows: read the time when the on-site monitoring and recording device records the current traveling wave and distance, calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

${\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula: l ₁ and l ₂ are the distances from the fault point to the two ends respectively; t1 and t2 are the time for the traveling wave to reach the two ends of the line respectively, and L is the total length of the submarine cable line. If the calculated distance l ₁ and l ₂ of _the fault point are greater than the total length L of the submarine cable, it means that the fault occurred on the _overhead line; , and can perform precise positioning based on the calculated distance. This fault location method based on submarine cables and overhead lines uses the first traveling wave head, so there is no problem of distinguishing the reflected wave at the fault point from the reflected wave at the opposite busbar. It is simple and reliable in principle, and its ranging accuracy is basically not affected by the line. Fault location, fault type, line length, grounding resistance and other factors.

Claims (5)

1. A fault location system based on submarine cables and overhead lines, characterized in that: the system includes on-site monitoring devices and diagnostic systems. 2. The fault location system based on submarine cables and overhead lines as claimed in claim 1, wherein the on-site monitoring device is installed at the first-stage tower at the junction of submarine cables and overhead lines, including a power supply unit and a Rogowski coil current sensor unit , a data collection and processing unit and a communication unit, the communication unit is connected to the power supply unit, the output terminal of the current sensor is connected to the input terminal of the data collection and processing unit, and the output terminal of the data collection and processing unit is connected to the input terminal of the communication unit, The on-site monitoring device establishes a communication connection with the data center through wireless communication technology. 3. The fault location system based on submarine cables and overhead lines as claimed in claim 1, wherein the diagnosis system includes a data center and a management system, and the management system reads data from the data center to realize accurate positioning of fault areas. 4. The fault location system based on submarine cables and overhead lines as claimed in claim 2, characterized in that: the Rogowski coil is used as a sensor for current measurement to measure power frequency fault current and traveling wave current, and it is to wind the wire evenly in a On the non-ferromagnetic ring frame, the primary bus bar is placed in the center of the coil, so the potential between the winding coil and the bus bar is isolated. 5. based on submarine cable and overhead wire fault location system as claimed in claim 2, it is characterized in that: data acquisition and processing unit are made up of microprocessor module, storage unit, several parts of high-speed acquisition module, and this functional unit requires system to be able to The power frequency load, fault current and traveling wave current signals are accurately collected, and then wirelessly transmitted to the monitoring center through the GPRS network. the

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