阅读说明：本技术 一种交流电缆改直流运行的长期电压试验系统 (Long-term voltage test system for changing alternating current cable into direct current operation ) 是由 彭维龙 乐彦杰 高震 郑新龙 徐蓓蓓 李世强 何旭涛 卢志飞 于 2019-10-11 设计创作，主要内容包括：本发明公开一种交流电缆改直流运行的长期电压试验系统,涉及电力输送领域。直流源不能承受电缆试验高压,为了接近交流直接改为直流运行工况,如何实现对试验电缆同时施加直流电压和直流电流,以消除涡流对电缆绝缘层最大温差的影响,就成为现阶段需重点突破的技术难题。本系统包括试验回路和模拟回路串联电缆系统、直流高压发生器、大电流直流发生器、输入端接交流电源的隔离变压器、控制器,模拟回路电缆导体与外护套、大电流直流发生器、模拟回路的无线测温模块与直流高压发生器通过绝缘支撑台实现同电位,模拟回路设电流电压测量传感装置和无线电缆测温传感器,电流和电压信号通过控制器传递给上位机,由上位机进行实时监测和控制。能有效实现对交流电缆改直流运行进行长期电压试验。(The invention discloses a long-term voltage test system for changing an alternating current cable into a direct current operation, and relates to the field of power transmission. The direct current source can not bear the high voltage of the cable test, and how to realize applying direct current voltage and direct current to the test cable simultaneously in order to approach the direct current operating condition of direct current change of alternating current directly, so as to eliminate the influence of eddy current on the maximum temperature difference of the cable insulating layer, becomes the technical problem needing key breakthrough at the present stage. The system comprises a test loop and a simulation loop series cable system, a direct current high-voltage generator, a large-current direct current generator, an isolation transformer with an input end connected with an alternating current power supply, and a controller, wherein a cable conductor and an outer sheath of the simulation loop, the large-current direct current generator, a wireless temperature measurement module of the simulation loop and the direct current high-voltage generator realize the same potential through an insulating support table, a current and voltage measurement sensing device and a wireless cable temperature measurement sensor are arranged in the simulation loop, current and voltage signals are transmitted to an upper computer through the controller, and the upper computer monitors and controls the current and the voltage signals in real time. The long-term voltage test can be effectively realized by changing the alternating current cable into the direct current operation.)

1. A long-term voltage test system for changing alternating current cable into direct current operation is characterized in that: the device comprises a cable system, a direct-current high-voltage generator (3), a large-current direct-current generator (1), an isolation transformer (2), a controller and an insulation support table (6), wherein the cable system comprises a test loop (4) and a simulation loop (5) serving as a cable test article, and the test loop (4) and the simulation loop (5) are connected in series; the input end of the isolation transformer (2) is connected with a 380V alternating current power supply (7), the output end of the isolation transformer is connected with the input end of the high-current direct current generator (1), and meanwhile, the neutral point of the isolation transformer is connected with the insulating support table (6); the output end of the high-current direct current generator (1) is connected with the terminal of the analog loop (5), and the other end of the high-current direct current generator is connected with the terminal of the test loop (4); one end of the direct-current high-voltage generator (3) is connected with the test loop (4) and the insulating support table (6), and the other end is grounded; a plurality of temperature measuring points are arranged on the analog loop (5) to arrange a wireless cable temperature measuring sensor, a current and voltage measuring and sensing device is further arranged on the analog loop (5), the wireless cable temperature measuring sensor and the current and voltage measuring and sensing device are connected to a controller, and the controller is connected to an upper computer to realize monitoring and control.

2. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 1, characterized in that: the grounding point of the large-current direct current generator (1) is connected with an insulating support table (6), and the analog loop (5) and the wireless cable temperature measuring sensor are placed on the insulating support table (6).

3. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 2, characterized in that: the test loop (4) winds a circle in a test field, and the test loop (4) is not connected with the insulating support table (6).

4. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 2, characterized in that: the distance between the temperature measuring points of every two adjacent wireless cable temperature measuring sensors is 0.5-2m, and the temperature measuring points are arranged along the analog loop (5) in equal length.

5. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 2, characterized in that: the isolation transformer (2) comprises a primary winding and a secondary winding, the input voltage of the primary winding is AC380V, and the output AC380V of the secondary winding is connected with the input end of the high-current direct-current generator (1).

6. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 5, wherein: heavy current direct current generator (1) adopt three-phase bridge rectifier circuit and LC filter circuit, three-phase 380V alternating current through empty opening, contactor to silicon controlled rectifier, input to three-phase bridge rectifier circuit after the silicon controlled rectifier pressure regulating, the pulsating direct current of rectification output, the LC filter circuit who comprises inductance-capacitance again obtains the more stable DC power supply of less ripple at the output of power after filtering, and with insulating brace table (6) homopotential.

7. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 2, characterized in that: the controller and the upper computer system are both provided with wireless transmission modules.

8. The long-term voltage test system for changing alternating current cable into direct current operation according to claim 7, characterized in that: the upper computer is provided with a monitoring module for monitoring the current, the voltage and the temperature rise of the cable test article and automatically generating a report, and a control module for remote control and local remote control protection.

9. The long-term voltage test system for changing AC cable into DC operation according to claim 2, wherein the temperature measurement range of the wireless cable temperature measurement sensor is 0 ~ 110 ℃, and the electric signal current converted from the temperature signal is 4 ~ 20 mA.

10. The long-term voltage testing system for alternating current-to-direct current operation of the alternating current cable according to claim 8, wherein: the testing system is provided with a wireless environment temperature measuring sensor for monitoring the environment temperature, the environment temperature measuring sensor is connected to an upper computer through a controller, and the upper computer can control and adjust the current of the conductor through the change of the environment temperature.

Technical Field

The invention relates to the field of power transmission, in particular to a long-term voltage test system for changing an alternating current cable into a direct current cable.

Background

With the difficulty in selecting urban power transmission corridors and the increasing requirement on power supply reliability, the XLPE cable is more and more widely applied to urban distribution networks due to excellent electrical properties, mechanical properties and physical and chemical properties of the XLPE cable. Compared with alternating current transmission, direct current transmission has high transmission efficiency and low line loss; the current is adjusted and the power transmission direction is changed conveniently; the number of lines for the circuit is small, the investment cost is low, and the long-distance power transmission is more economical than alternating current; the length of the direct current cable is not limited by capacitance current, and the direct current cable is favorable for sea-crossing clouds, sea-island power transmission and the like; the frequency-adjustable short-circuit protection device can be used as a connecting line of two power grids, can be applied even when the frequencies of the two power grids are different, and can reduce short-circuit current between a main line and the power grids. From the current industry experience, the possibility and feasibility that the alternating current cable with the voltage level of 110kV or below is directly changed into the direct current operation are provided, the direct change of the alternating current into the direct current operation of the cable with the voltage level of 220kV or above has a larger risk due to the space charge effect under a strong field and the temperature influence of thick insulation, and the direct current cable with the voltage level of ultrahigh voltage is not recommended to be carried out, and special direct current insulation and shielding materials are used. Therefore, the ac cable can be used for dc transmission by designing appropriate operation parameters and operation methods.

The existing traditional direct current cable long-term voltage test adopts a 2-loop cable circuit, alternating current is respectively applied to the 2-loop cable circuit through a plurality of groups of core-penetrating transformers for temperature rise, and a simulation loop and a plurality of groups of core-penetrating transformers do not bear test voltage; in the existing traditional direct current cable long-term voltage test, because a test loop and a simulation loop have different currents, the current values of the test loop and the simulation loop are close, the simulation loop is used as temperature measurement reference, temperature signals are collected by a thermocouple, and data are transmitted by using optical fibers in a wired mode.

When the voltage level of the cable is low, the alternating current generates induction current in the insulating sheath of the cable, and eddy current is formed. Eddy currents, like ordinary currents, produce thermal effects. For a direct current cable, in a long-term voltage test, the maximum temperature difference between the conductor temperature and the insulation layer of the cable needs to be measured. Therefore, the maximum temperature difference of the cable insulation layer with low voltage level can be influenced by adopting the traditional heating modeThereby affecting the cable temperature rise. In this case, it is necessary to establish a new way of applying load to the cable conductor to eliminate the effect of eddy currents on the maximum temperature difference of the cable insulation.

Therefore, how to apply the direct voltage and the direct current to the test cable simultaneously to eliminate the influence of the eddy current on the maximum temperature difference of the cable insulation layer becomes a technical problem needing to be broken through at the present stage.

Disclosure of Invention

The technical problem to be solved and the technical task provided by the invention are to perfect and improve the prior technical scheme, and provide a long-term voltage test system for changing an alternating current cable into a direct current to run so as to achieve the purpose of carrying out a long-term voltage test on the alternating current cable for direct current transmission. Therefore, the invention adopts the following technical scheme.

A long-term voltage test system for changing an alternating current cable into a direct current operation comprises a cable system, a direct current high-voltage generator, a large-current direct current generator, an isolation transformer, a controller and an insulation support table, wherein the cable system comprises a test loop and a simulation loop used as a cable test article, and the test loop is connected with the simulation loop in series; the input end of the isolation transformer is connected with an alternating current power supply, the output end of the isolation transformer is connected with the input end of the high-current direct current generator, and the neutral point of the isolation transformer is connected with the insulation support platform; the output end of the large-current direct current generator is connected with the analog loop terminal, and the other end of the large-current direct current generator is connected with the test loop terminal; one end of the direct current high voltage generator is connected with the test loop and the insulating support platform, and the other end of the direct current high voltage generator is grounded; a plurality of temperature measuring points are arranged on the analog loop, a wireless cable temperature measuring sensor is arranged on the analog loop, a current and voltage measuring and sensing device is further arranged on the analog loop, the wireless cable temperature measuring sensor and the current and voltage measuring and sensing device are connected to a controller, and the controller is connected to an upper computer to realize monitoring and control. The test circuit and the simulation circuit are connected in series by a 1-loop cable line, a high-current direct-current generator simultaneously applies direct current to the test circuit and the simulation circuit to achieve temperature rise, the test circuit and the simulation circuit are the same current, a direct-current high-voltage generator simultaneously applies voltage to the test circuit, the temperature of a cable conductor is converted into an electric signal by a wireless cable temperature measuring sensor, the electric signal is transmitted to an upper computer by a controller, a current and voltage measuring and sensing device transmits current and voltage signals to the upper computer by the controller, and the upper computer carries out real-time monitoring and control, so that the direct-current operation of the alternating-current cable can be changed into the direct-current operation for long-term voltage test, the technical problem that the direct-current voltage and the direct current are simultaneously applied to the test cable in the long-term voltage test of the direct-current transmission of the alternating, for the transformation of an existing power distribution network, a test basis is provided in the aspect of reliability of direct current running instead of an original alternating current line, and technical guarantee is provided for safe running of a cable.

As a preferable technical means: the grounding point of the large-current direct-current generator is connected with the insulating support platform, and the analog circuit and the wireless cable temperature measuring sensor are placed on the insulating support platform. The cable conductor and the outer sheath of the analog loop, the large-current direct-current generator, the wireless temperature measurement module of the analog loop and the direct-current high-voltage generator have the same potential and can bear the test direct-current high voltage.

As a preferable technical means: the test loop is wound by one circle in a test field, and the test loop is not connected with the insulating support platform. The simulation loop with enough length is ensured, so that the test is closer to the real situation of the actual AC line.

As a preferable technical means: the distance between the temperature measuring points of every two adjacent wireless cable temperature measuring sensors is 0.5-2m, and the temperature measuring points are arranged along the analog loop at equal length. The distance is suitable, the distribution is uniform, and the temperature monitoring reliability is good.

As a preferable technical means: the isolation transformer comprises a primary winding and a secondary winding, the input voltage of the primary winding is AC380V, and the output AC380V of the secondary winding is connected with the input end of the high-current direct-current generator. Adopt 380V alternating current to accord with present alternating current low voltage distribution network, compare in connecting medium-high voltage distribution network, the technical degree of difficulty is lower, and it is more convenient to connect the operation, and the security is better.

As a preferable technical means: the high-current direct-current generator adopts a three-phase bridge rectifier circuit and an LC filter circuit, three-phase 380V alternating current is input to the three-phase bridge rectifier circuit through an air switch, a contactor and a silicon controlled rectifier after being regulated by the silicon controlled rectifier, the alternating current is rectified and output into pulsating direct current, and the direct-current power supply with relatively stable small ripples is obtained at the output end of the power supply after the LC filter circuit consisting of an inductance capacitor is filtered, and is at the same potential as an insulating support table. The conversion from alternating current to direct current can be conveniently realized, and the output power supply is stable and reliable.

As a preferable technical means: the controller and the upper computer system are both provided with wireless transmission modules. The wireless transmission of signals can be conveniently realized.

As a preferable technical means: the upper computer is provided with a monitoring module for monitoring the current, the voltage and the temperature rise of the cable test article and automatically generating a report, and a control module for remote control and local remote control protection. The comprehensive monitoring and safety control of the test system can be realized.

The wireless cable temperature sensor has the advantages that the temperature measuring range is 0 ~ 110 ℃, the electric signal current converted by the temperature signal is 4 ~ 20mA, the temperature rising range of the conductor can be effectively covered, the signal current range of 4 ~ 20mA is sufficient, and the wireless cable temperature sensor is clear and stable.

As a preferable technical means: the testing system is provided with a wireless environment temperature measuring sensor for monitoring the environment temperature, the environment temperature measuring sensor is connected to an upper computer through a controller, and the upper computer can control and adjust the current of the conductor through the change of the environment temperature. The environment temperature monitoring and the current control adjustment of the conductor loop are effectively realized.

Has the advantages that: the direct current running of the alternating current cable can be effectively changed into the direct current running for carrying out a long-term voltage test, the technical problem that the direct current voltage and the direct current are simultaneously applied to the test cable in the long-term voltage test for changing the alternating current cable into the direct current running so as to eliminate the influence of eddy current on the maximum temperature difference of a cable insulating layer is solved, for the transformation of an existing power distribution network, a test basis is provided in the aspect of the reliability of directly changing an original alternating current circuit into the direct current running, and the technical guarantee is provided for the safe running of the cable.

Drawings

Fig. 1 is a schematic diagram of the principle of the present invention.

In the figure: 1-a high current dc generator; 2-an isolation transformer; 3-a direct current high voltage generator; 4-a test loop; 5-an analog loop; 6-insulating support table; 7-alternating current power supply.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the drawings in the specification.

As shown in fig. 1, a long-term voltage test system for changing an ac cable into a dc operation includes a cable system, 1 set of dc high voltage generator 3, 1 set of large current dc generator 1, 1 isolation transformer 2, a controller and an insulation support table 6, where the cable system includes a test loop 4 and a simulation loop 5 as a cable test product, and the test loop 4 and the simulation loop 5 are connected in series; the input end of the isolation transformer 2 is connected with an alternating current power supply 7, the output end of the isolation transformer is connected with the input end of the high-current direct current generator 1, and meanwhile, the neutral point of the isolation transformer is connected with the insulation support table 6; the output end of the large-current direct current generator 1 is connected with the terminal of the analog loop 5, and the other end is connected with the terminal of the test loop 4; one end of the direct-current high-voltage generator 3 is connected with the test loop 4 and the insulating support table 6, and the other end of the direct-current high-voltage generator is grounded; a plurality of temperature measuring points are arranged on the analog loop 5, a wireless cable temperature measuring sensor is arranged on the analog loop 5, a current and voltage measuring sensing device is further arranged on the analog loop 5, the wireless cable temperature measuring sensor and the current and voltage measuring sensing device are connected to a controller, and the controller is connected to an upper computer to realize monitoring and control.

In order to bear the high voltage of the test direct current, the grounding point of the large-current direct current generator 1 is connected with an insulating support table 6, and the analog loop 5 and the wireless cable temperature measuring sensor are placed on the insulating support table 6. The cable conductor and the outer sheath of the analog loop 5, the large-current direct-current generator 1, the wireless temperature measurement module of the analog loop 5 and the direct-current high-voltage generator 3 have the same potential and can bear the test direct-current high voltage.

In order to make the test closer to the actual situation of the actual ac line, the test loop 4 is wound around the test site, and the test loop 4 is not connected to the insulating support table 6. The simulation loop 5 with enough length is ensured, so that the test is closer to the real situation of the actual AC line.

In order to realize comprehensive and reliable temperature monitoring, the distance between the temperature measuring points of every two adjacent wireless cable temperature measuring sensors is 0.8m, and the temperature measuring points are arranged along the analog loop 5 in equal length. The distance is suitable, the distribution is uniform, and the temperature monitoring is comprehensive and reliable.

For convenience of connection, the isolation transformer 2 comprises a primary winding and a secondary winding, wherein the input voltage of the primary winding is AC380V, and the output AC380V of the secondary winding is connected with the input end of the high-current direct-current generator 1. Adopt 380V alternating current to accord with present alternating current low voltage distribution network, compare in connecting medium-high voltage distribution network, the technical degree of difficulty is lower, and it is more convenient to connect the operation, and the security is better.

In order to realize stable and reliable alternating current-direct current conversion, the high-current direct current generator 1 adopts a three-phase bridge rectifier circuit and an LC filter circuit, three-phase 380V alternating current passes through an air switch, a contactor and a silicon controlled rectifier, is input into the three-phase bridge rectifier circuit after being subjected to voltage regulation by the silicon controlled rectifier, rectifies and outputs pulsating direct current, and then obtains a relatively stable direct current power supply with smaller ripples at the output end of the power supply after being filtered by the LC filter circuit consisting of an inductance capacitor, and has the same potential as the insulation support table 6. The conversion from alternating current to direct current can be conveniently realized, and the output power supply is stable and reliable.

In order to realize wireless transmission of signals, the controller and the upper computer system are both provided with wireless transmission modules. The wireless transmission of signals can be conveniently realized.

In order to realize comprehensive monitoring and safety control, the upper computer is provided with a monitoring module for monitoring the current, the voltage and the temperature rise of the cable test article and automatically generating a report, and a control module for remote control and local remote control protection. The comprehensive monitoring and safety control of the test system can be realized.

In order to realize the monitoring of the temperature rise of the cable, the temperature measuring range of the wireless cable temperature measuring sensor is 0 ~ 110 ℃, the electric signal current converted by the temperature signal is 4 ~ 20mA, during the test, the test loop 4 and the simulation loop 5 are simultaneously heated by the direct current large current generator, the temperature of the cable conductor reaches 70-75 ℃, the temperature measuring range is 0 ~ 110 ℃, the temperature rising range of the conductor can be effectively covered, and the signal current range of 4 ~ 20mA is clear and stable enough.

In order to realize current control and regulation, the test system is provided with a wireless environment temperature sensor for monitoring the environment temperature, the environment temperature sensor is connected to an upper computer through a controller, and the upper computer can control and regulate the current of the conductor through the change of the environment temperature. The environment temperature monitoring and the current control adjustment of the conductor loop are effectively realized.

The test circuit 4 and the simulation circuit 5 are connected in series by a 1-loop cable line, the test circuit 4 and the simulation circuit 5 are simultaneously applied with direct current to achieve temperature rise through the high-current direct current generator 1, the test circuit 4 and the simulation circuit 5 are the same current, the direct current high-voltage generator 3 simultaneously applies voltage to the test circuit 4, the cable conductor and the outer sheath of the simulation circuit 5 are at the same potential and can bear test voltage, the temperature of the cable conductor is converted into an electric signal through the wireless cable temperature measuring sensor, the electric signal is transmitted to the upper computer through the controller, the current and voltage measuring and sensing device transmits the current and voltage signals to the upper computer through the controller, the upper computer monitors and controls the temperature in real time, and long-term voltage test of the alternating current cable for direct current transmission can be effectively realized.

The long-term voltage test system for changing the alternating current cable into the direct current operation shown in fig. 1 is a specific embodiment of the present invention, has shown the outstanding substantive features and significant progress of the present invention, and can make equivalent modifications in shape, structure and the like according to the practical use requirements and under the teaching of the present invention, all of which are within the protection scope of the present solution.