CN210957797U

CN210957797U - 110kV alternating-current high-voltage power transmission system based on magnetic saturation type superconducting current limiter

Info

Publication number: CN210957797U
Application number: CN201921905268.4U
Authority: CN
Inventors: 杨颖�; 杨正
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2019-11-06
Filing date: 2019-11-06
Publication date: 2020-07-07
Anticipated expiration: 2029-11-06

Abstract

The utility model discloses a 110kV exchanges high voltage transmission system based on magnetic saturation type superconductive current limiter, its constitution includes: the power generation device comprises a generator (1), a step-up transformer (2), a step-down transformer (3), a magnetic saturation type superconducting current limiter (4) and a load (5), wherein the magnetic saturation type superconducting current limiter (4) is installed between the step-down transformer (3) and the load (5), and the amplitude of short circuit impact current in 110kV power supply is restrained through parameter setting of the magnetic saturation type superconducting current limiter (4). Composition of the magnetic saturation type superconducting current limiter (4): the device comprises a current limiting module, a direct current bias module, a measurement and control module and a refrigerating system; the current limiting module comprises: iron core loop, AC coil, superconducting DC coil and Dewar. The technical effects of the utility model: the magnetic saturation type high-temperature superconducting current limiter utilizes the high-temperature superconducting coil to carry out direct current bias, can effectively limit short-circuit current in an alternating current high-voltage power transmission system, and has better practicability.

Description

110kV alternating-current high-voltage power transmission system based on magnetic saturation type superconducting current limiter

Technical Field

The utility model relates to an exchange high voltage transmission technical field, concretely relates to contain superconductive current limiter 110kV of magnetic saturation and exchange high voltage transmission system.

Background

Short-circuit faults in ac high-voltage transmission systems are very harmful to the normal operation of the high-voltage electrical equipment itself and the system. The concrete points are as follows: 1) dynamic and thermal stabilization effects of the short circuit current may damage the electrical equipment. On the one hand, when short-circuit currents flow through electrical devices, the intense thermal effects can cause damage to the conductors or their insulation. On the other hand, when short-circuit current flows through the conductor, the conductor is impacted by large electrodynamic force to cause deformation and even damage of the conductor; 2) when a short-circuit fault occurs, the voltage in a power grid can be reduced, particularly the voltage close to a short-circuit fault point is obviously reduced, the power supply of a user is seriously influenced, the electrical equipment cannot work normally, and even the equipment is damaged and the product quality is unqualified; 3) the occurrence of short circuit in the system is equivalent to the change of the power grid structure, which inevitably causes the change of the power distribution in the system, and the output power of the generator correspondingly changes. The active power output by the generator will drop whenever a short circuit occurs at any point, but the input power to the generator is determined by the prime mover or the water intake and cannot be changed immediately. Imbalance of input power and output power of the generators inevitably causes rotation speed change, so that the generators running in parallel are likely to lose synchronization, the stability of a system is damaged, and even large-area power failure is caused; 4) the unbalanced current generated by the asymmetric short-circuit fault can cause serious unbalanced magnetic flux to be generated, and further large induced potential is formed in a communication line adjacent to the power transmission line, so that electromagnetic interference to a communication system is caused, and the personal safety of communication equipment and operation and maintenance personnel can be seriously endangered.

The superconducting fault current limiter utilizes the transition characteristic of superconducting materials between a superconducting state and a normal state and auxiliary components to generate proper impedance in a circuit to realize fault current limiting. The current limiter has an automatic reset function and can operate at a high potential.

SUMMERY OF THE UTILITY MODEL

The utility model discloses be applied to 110kV AC high voltage transmission system with magnetic saturation type superconductive current limiter, concrete technical scheme is as follows:

a110 kV alternating-current high-voltage power transmission system based on a magnetic saturation type superconducting current limiter comprises the following components: the generator 1, the step-up transformer 2, the step-down transformer 3, the magnetic saturation type superconducting current limiter 4 and the load 5 are arranged between the step-down transformer 3 and the load 5, and the amplitude of short circuit impact current in 110kV power supply is restrained through parameter setting of the magnetic saturation type superconducting current limiter 4.

The magnetic saturation type superconducting current limiter 4 comprises the following components: the device comprises a current limiting module, a direct current bias module, a measurement and control module and a refrigerating system.

The current limiting module comprises: iron core loop, AC coil, superconducting DC coil and Dewar.

The iron core is provided with the permanent magnet in the iron core loop to form the permanent magnet offset type magnetic saturation current limiter.

The technical effects of the utility model: when the circuit normally operates, the transmission current of the circuit is below critical current and presents zero impedance or extremely small impedance, and the rated current passes through the circuit almost without loss; when in fault, the superconductor rapidly quenches to present nonlinear high resistance due to the fact that the short-circuit current is larger than the critical current, and reacts within milliseconds, so that the short-circuit current can be limited to be about 2 times of the rated current of the circuit; the magnetic saturation type high-temperature superconducting current limiter utilizes the high-temperature superconducting coil to carry out direct current bias, can effectively limit short-circuit current in an alternating current high-voltage power transmission system, and has better practicability; the permanent magnet offset type magnetic saturation current limiter does not need an additional direct current winding and a power supply, and the operation reliability is improved.

Drawings

Fig. 1 is a composition diagram of a 110kV alternating-current high-voltage power transmission system based on a magnetic saturation type superconducting current limiter.

Fig. 2 is a structural view of a magnetic saturation type superconducting current limiter.

Fig. 3 is a schematic diagram of a permanent magnet biased magnetically saturated current limiter.

In the figure: 1 is a generator, 2 is a step-up transformer, 3 is a step-down transformer, 4 is a magnetic saturation type superconducting current limiter, and 5 is a load.

Detailed Description

The following description will further describe embodiments of the present invention with reference to the accompanying drawings.

1. Integral implementation scheme of 110kV alternating-current high-voltage transmission system based on magnetic saturation type superconducting current limiter

A110 kV alternating-current high-voltage power transmission system based on a magnetic saturation type superconducting current limiter comprises the following components: the generator 1, the step-up transformer 2, the step-down transformer 3, the magnetic saturation type superconducting current limiter 4 and the load 5 are arranged between the step-down transformer 3 and the load 5, and the amplitude of short circuit impact current in 110kV power supply is restrained through parameter setting of the magnetic saturation type superconducting current limiter 4. As shown in fig. 1.

The magnetic saturation type superconducting current limiter 4 comprises the following components: the device comprises a current limiting module, a direct current bias module, a measurement and control module and a refrigerating system. As shown in fig. 2.

The current limiting module comprises: iron core loop, AC coil, superconducting DC coil and Dewar. As shown in fig. 2.

The iron core is provided with the permanent magnet in the iron core loop to form the permanent magnet offset type magnetic saturation current limiter. As shown in fig. 3.

2. Step-up transformer

A transformer is a common electrical device that can be used to transform an alternating voltage of one value to another alternating voltage of the same frequency. A step-up transformer is a transformer used to transform an alternating voltage of a low value into another alternating voltage of a higher value of the same frequency.

An ac step-up transformer is a device for converting ac voltage, current and impedance, and when an ac current flows through a primary winding, an ac magnetic flux is generated in an iron core (or a magnetic core) to induce a voltage (or a current) in a secondary winding. The transformer consists of an iron core (or a magnetic core) and a coil, wherein the coil is provided with two or more than two windings, the winding connected with a power supply is called a primary coil, and the other windings are called secondary coils. The alternating-current step-up transformer has the characteristics of small volume, light weight, compact structure, complete functions, strong universality, convenient use and the like, is particularly suitable for the frequency convergence or alternating-current high-voltage insulation strength test of various high-voltage electrical equipment, electrical elements and insulating materials in power systems, industrial and mining enterprises, scientific research departments and the like, and is essential important equipment in high-voltage tests.

The utility model discloses the step up transformer who selects does: 10.5kV/110kV, 120 MVA.

3. Step-down transformer

The step-down transformer is a transformer which converts the higher voltage of the input end into the ideal voltage with relatively lower output, thereby achieving the purpose of step-down. The step-down transformer is an important device in a power transmission and transformation system, and the normal operation of the step-down transformer not only relates to the safety of the step-down transformer and the reliable power supply of users, but also directly influences the stability of a power system.

The protection configuration of the step-down transformer should meet the requirement that the transformer cannot be burnt in any condition, so that the accident is enlarged and the stability of the power system is influenced. The working principle, the relay protection principle, the operation condition, the operation and requirement, and the abnormal operation and processing method are described in detail.

The utility model discloses the step-down transformer of selecting does: 110kV/6.3kV, 15 MVA.

4. Magnetic saturation type high-temperature superconducting current limiter for protecting 110kV alternating-current high-voltage power transmission system

In the process of researching the operation and the fault of the power system and discussing the countermeasure for the abnormal reaction, the relay with contacts is mainly used for protecting the power system, the step-down transformer, the generator, the transmission line and other elements so as to avoid the damage, namely relay protection, and the relay protection method mainly aims to send an early warning signal to an operator in time when the power system has the fault or send an ICJ jumping command to a controlled breaker so as to control the ICJ jumping device closest to the element with the fault and disconnect the fault element from the power system in time, so that the damage of the power element is reduced to a greater extent, the risk of safe power supply of the power system is reduced, and therefore, the principle of the relay protection device is very important to understand.

When a step-down transformer and the like in a power system are abnormal, except for strengthening a monitoring pipe, relay protection personnel are also contacted to process that the protection possibly causing misoperation is returned to an outlet pressing plate, and the following abnormal conditions are common during the withdrawal:

(1) when signals of 'bus differential alternating current short line' and 'bus differential direct current voltage vanish' are sent, attention is paid to the conditions that when bus differential unbalanced current is not zero and bus-coupled switches without special bypass buses operate in series instead of lines;

(2) when the direct current disappears and the periodic channel test parameters do not meet the requirements, when the device fails or a channel abnormal signal is sent out and cannot be restored, the relay protection personnel need to take a response measure for quitting in time; when the transformer is used for oil filling, oil filtering or silica gel replacement, a respiratory system needs to be opened to discharge an oil plug, a gas discharge valve and the like, strict monitoring is needed to prevent relay protection from being in problem, and corresponding protection measures are provided for the problems.

1) Influence of magnetic saturation type high-temperature superconducting current limiter on current protection

When the fault occurs, the current limiting impedance presented by the magnetic saturation type high-temperature superconducting current limiter greatly reduces the short-circuit current of the system, and the protection of the current I, II section can be 'refused' because the short-circuit current is too small and is lower than the originally set action current, so that the protection is failed. Therefore, before the magnetic saturation type high-temperature superconducting current limiter is put into use, the current protection needs to be set again: the starting current of the current I, II protection segment is adjusted according to the following formula; the current III section is still set in the original way (i.e. the starting current should be larger than the maximum load current that may occur on the line).

In the formula (I), the compound is shown in the specification,

the short-circuit current is the short-circuit current when three-phase fault occurs after the magnetic saturation type high-temperature superconducting current limiter is connected; z_SISFCLThe impedance of the magnetic saturation type high-temperature superconducting current limiter is represented in a 'limited flow state'.

2) Influence of magnetic saturation type high-temperature superconducting current limiter on distance protection

Distance protection is a protection device that reflects the distance between a fault point and a protection installation point and determines whether to operate and the operation time according to the distance, and is generally used as main protection or backup protection of a high-voltage transmission line. For example, an 3/2 wiring mode is generally adopted for outgoing lines of a 500kV substation, and after the magnetic saturation type high-temperature superconducting current limiter is connected to an extra-high voltage transmission line, the electric quantities such as voltage and current of the transmission line are significantly changed, so that the electric distance of a fault point is correspondingly changed, and therefore, the connection of the magnetic saturation type high-temperature superconducting current limiter has an important influence on the distance protection of the transmission line. The electrical quantities for typical distance protection are taken from the line side voltage and current.

3) Influence of magnetic saturation type high-temperature superconducting current limiter magnetic loss on zero sequence current protection

Under the condition that a system normally operates, if a magnetic saturation type high-temperature superconducting current limiter of a certain phase in a circuit suddenly loses magnetism, the magnetic saturation type high-temperature superconducting current limiter of the lost magnetism one phase is converted from a steady state to a current limiting state to operate, the impedance of the magnetic saturation type high-temperature superconducting current limiter is remarkably increased, and therefore three-phase impedance is obviously asymmetric.

For the above situation, the magnetic saturation type high-temperature superconducting current limiter should be provided with the loss-of-magnetization protection: when the power system normally operates, once the monitoring device finds that the direct-current excitation system works abnormally and the magnetic saturation type high-temperature superconducting current limiter is in the current limiting state, the magnetic loss phase magnetic saturation type high-temperature superconducting current limiter is isolated immediately through switching operation, zero-sequence unbalanced current is prevented from being generated, and therefore misoperation of zero-sequence current protection is avoided.

4) Influence of magnetic saturation type high-temperature superconducting current limiter on longitudinal differential protection

The longitudinal differential protection on the high-voltage transmission line is to longitudinally connect the protection devices at two ends of the transmission line by using a certain communication channel, transmit the electric quantity (current, power direction and the like) of each end to the opposite end, and compare the electric quantities at the two ends to judge whether a fault occurs in the range of the line or out of the range of the line, thereby determining whether to cut off the protected line. Thus, the pilot differential protection is theoretically absolutely selective. The impedance of the magnetic saturation type high-temperature superconducting current limiter in the limited flow state is not large relative to the total impedance of the power transmission line, and is only equivalent to the fact that the electrical distance of the power transmission line is increased by dozens of kilometers, so that the addition of the magnetic saturation type high-temperature superconducting current limiter does not obviously affect longitudinal differential protection.

5. Magnetic saturation type superconducting current limiter

(1) Dewar flask

The main structure and the function of each part of a Dewar bottle (Dewar) are as follows:

an outer cylinder body: besides protecting the inner barrel, the vacuum interlayer is formed with the inner barrel to prevent the heat from invading outside the bottle and reduce the natural vaporization of the low-temperature liquid in the bottle; an inner cylinder body: storing the low-temperature liquid; a vaporizer: the liquid gas in the bottle is converted into a gaseous state through the heat exchange with the inner wall of the outer barrel; liquid valve: controlling the Dewar flask to fill liquid or discharge liquid from the flask; a safety valve: when the pressure of the container is higher than the maximum working pressure, the pressure is automatically released, and the jump pressure is slightly higher than the maximum working pressure; a discharge valve: when the Dewar bottle is filled with liquid, the valve is used to discharge gas in the gas phase space in the bottle, and reduce the pressure in the bottle, so as to fill liquid quickly and smoothly. The valve can be used for manually discharging gas in the bottle to reduce the pressure in the bottle when the pressure in the bottle exceeds the highest working pressure in storage or other situations of the Dewar bottle; a pressure gauge: indicating the pressure of the inner cylinder of the bottle; a pressure increasing valve: after the valve is opened, the liquid in the cylinder exchanges heat with the outer cylinder wall through the pressurizing coil pipe, is vaporized into gas, enters the gas phase space at the upper part of the inner cylinder wall, and establishes certain driving pressure (internal pressure) for driving the low-temperature liquid in the cylinder to flow; using a valve: the valve is used for opening a pipeline passage of a Dewar flask liquid vaporization loop and a gas inlet end for a user, and can also be used for controlling the flow rate of gas; a liquid level meter: the height of the liquid level in the container is visually indicated, and the installation position is convenient for operators to observe and overhaul.

(2) Permanent magnet offset

A permanent magnet offset type magnetic saturation current limiter is characterized in that a permanent magnet is added in an iron core loop of the magnetic saturation current limiter to replace an active direct current offset winding. The magnetomotive force is limited by magnetic materials, and the regulation and control performance is poor; in addition, the resultant magnetic flux may cause demagnetization of the permanent magnet, and particularly, the permanent magnet may be seriously demagnetized when a large current is short-circuited. Fig. 3 is a schematic diagram of a permanent magnet biased magnetic saturation type current limiter.

Compared with a superconducting magnetic saturation current limiter, the permanent magnet offset type magnetic saturation current limiter does not need an additional direct current winding and a power supply, and the operation reliability is improved. The topological structure and the manufacturing process of the transformer are similar to those of an oil immersed transformer, and the mature design and processing process can be used for reference. The permanent magnet offset type magnetic saturation current limiter has the obvious advantages of high operation reliability, automatic switching without additional control, low price, good economic performance and the like, and can overcome the defects of the prior current limiting technology.

Permanent magnet biased magnetic saturation current limiters also face some problems to be solved urgently. The alternating current coil is sleeved on the permanent magnet, the permanent magnet can be demagnetized under the action of the resultant magnetic flux, and particularly, when the short-circuit large current is generated, the demagnetization of the permanent magnet is more serious. To solve this problem, a magnetic structure in the shape of a "Chinese character ri" is presented. The current limiter adopts a permanent magnet parallel bias mode. The current limiter adopts an iron core, a permanent magnet and two alternating current windings, the alternating current windings wound on the iron core branches at two sides generate opposite magnetic fields, and the current limiter can alternatively exit from saturation in positive and negative half waves during short-circuit fault so as to realize current limiting. The design scheme can save iron core materials and reduce manufacturing cost. The great britain AREVA T & D center also provides a square permanent magnet type magnetic saturation current limiter, which is more economical in design than a square, and the permanent magnet is divided into an upper part and a lower part which are connected with an iron core in series, so that the magnetic leakage is reduced, and the structural design is simpler.

Compared with the traditional direct current offset type magnetic saturation current limiter, the permanent magnet offset type magnetic saturation current limiter has the advantages of simple structure, economy, reliability, easiness in realizing high voltage and large capacity and the like, and has application prospect in a high-voltage power system. However, the permanent magnet offset type magnetic saturation current limiter also has obvious defects, such as demagnetization of the permanent magnet, poor offset controllability and the like.

Claims

1. A110 kV alternating-current high-voltage power transmission system based on a magnetic saturation type superconducting current limiter comprises the following components: generator (1), step-up transformer (2), step-down transformer (3), magnetic saturation type superconductive current limiter (4), load (5), its characterized in that: the magnetic saturation type superconducting current limiter (4) is arranged between the step-down transformer (3) and the load (5), and the amplitude of short circuit impact current in 110kV power supply is restrained through parameter setting of the magnetic saturation type superconducting current limiter (4).

2. A 110kV alternating current high voltage power transmission system according to claim 1, characterized in that: the magnetic saturation type superconducting current limiter (4) comprises the following components: the device comprises a current limiting module, a direct current bias module, a measurement and control module and a refrigerating system.

3. A 110kV alternating current high voltage power transmission system according to claim 2, characterized in that: the current limiting module comprises: iron core loop, AC coil, superconducting DC coil and Dewar.

4. A 110kV alternating current high voltage power transmission system according to claim 3, characterized in that: and a permanent magnet is added into the iron core loop to form a permanent magnet offset type magnetic saturation current limiter.