CN105679507A - Instantaneous adjustable electric reactance current limiting reactor - Google Patents

Abstract

The invention discloses a current-limiting reactor with instantaneous adjustable reactance, which comprises a static iron core, a moving iron core and a winding coil. The winding coil is arranged on the static iron core, and the static iron core is provided with an air gap. The moving iron core can be inserted into said air gap in the event of a short circuit in the corresponding power system. When the power system is running, the moving iron core in the present invention is separated from the position of the air gap of the static iron core and maintains this state. When the power system fails, the current rises rapidly, the system protection device detects the current signal and sends the signal to the drive mechanism, the drive mechanism drives the moving iron core to move towards the air gap of the static iron core, and the moving iron core gradually enters the air gap middle. With the gradual reduction of the air gap, the reactance value of the reactor increases rapidly, so as to achieve the purpose of current limitation, and the response is rapid.

Description

A Current Limiting Reactor with Instantaneous Adjustable Reactance

technical field

The invention relates to the technical field of reactors, in particular to a current-limiting reactor with instantaneously adjustable reactance.

Background technique

With the rapid development of the power system, the capacity of single unit, power plant capacity, substation capacity, load and load density in cities and industrial centers increase, and the interconnection between power systems leads to the continuous increase of the short-circuit current in the power system. At present, excessive short-circuit current or even exceeding the standard has become an important factor restricting the development of power grids. Replacing switches is one of the means to solve the problem of excessive short-circuit current, but substations with excessive short-circuit current are generally hub substations, and there are many switches that need to be replaced, and most of the primary equipment and grounding grids also need to be replaced. Although the replacement of switches has no effect on the operation characteristics of the power grid, this method requires a large investment and a long construction period, which makes the grid hub substation in an abnormal operation mode for a long time. Now, the method commonly used at home and abroad is to limit the growth of short-circuit current. Limiting short-circuit current can start from the grid structure, operation mode and current limiting equipment. Current-limiting equipment (short-circuit limiter, current-limiting reactor, etc.) is a hot spot in power system research at home and abroad, and can be roughly divided into four categories according to its technology: (1) Traditional type, which uses series reactors to limit short-circuit current. This method is a mature technology and has a large number of applications in power systems, but its operation loss is large, and it may reduce the stability of power grid operation. (2) Power electronic type, which uses power electronic switches to quickly cut off or transfer short-circuit current, and its current limiting element is still a reactor. The main problem of this method is that the parameter requirements of power electronic devices are high, and the operation loss is large. (3) Special material type, such as superconducting materials and materials with positive temperature coefficient (PTC), are used as the impedance to limit the short-circuit current. When the power grid is running normally, the current limiting impedance is almost zero. Once a short-circuit fault occurs, the short-circuit current exceeds the critical current and presents a significant current-limiting impedance. This kind of short-circuit current limiter is mostly in the experimental stage due to the limitation of the development of new materials, and the cost is high. (4) Comprehensive type, which integrates several types of current limiting technologies and applies them together. For medium and high voltage power transmission and distribution systems, the traditional series reactor technology is the most likely short-circuit current limiting measure at this stage.

The essence of the current-limiting reactor is to reduce the tightness of the power grid by increasing the system impedance, thereby reducing the short-circuit current of some branches of the substation bus. Series reactors have been widely used in medium and low voltage systems. With the improvement of switch manufacturing level, the use of series reactors in medium and high voltage systems has gradually decreased. However, the series reactor can effectively reduce the short-circuit current level of the system and reduce the short-circuit current tolerance level of the equipment. It has very significant economic benefits and is still widely used in many occasions. The typical configuration methods of series reactors mainly include: bus connection method, line terminal connection method, series connection in transformer branch circuit and installation at transformer neutral point. Series reactors are divided into conventional series reactors and adjustable series reactors according to their control types. Conventional series reactors are non-adjustable reactors, which have the advantages of simple operation, safety and reliability, but will greatly increase reactive power loss and active power loss, and sometimes reduce the stability of the power system, and need to be adjusted on existing lines. The distance protection scheme is modified. The adjustable series reactor has little impact on the power grid when the system is running normally, and can limit the short-circuit current relatively quickly when the system is short-circuited. Adjustable series reactors can be divided into two types according to the technical route: turn-adjustable controllable reactors and DC-assisted magnetic permeability-adjustable controllable reactors. The two kinds of adjustable series reactors solve the disadvantages of large operating loss and fixed inductance value of conventional series reactors to varying degrees, and have little impact on the stability of the power system. However, it takes several seconds for the inductance adjustment of the turn-adjusting controllable reactor to reach the predetermined value, and the adjustment time of the DC-assisted magnetic permeability controllable reactor is shorter, but it also reaches about 100ms or even longer. At this time, the power system where the short-circuit accident occurs, especially the DC system, may cause serious accidents.

Contents of the invention

The purpose of the present invention is to provide a current-limiting reactor with instantaneous adjustable reactance that can respond quickly when a short circuit occurs in a power system.

In order to achieve the above object, the technical scheme of the current-limiting reactor in the present invention is as follows: the current-limiting reactor with instantaneous adjustable reactance includes a static iron core, a moving iron core and a winding coil, and the winding coil is arranged on the static iron core. An air gap is provided on the static iron core, and the moving iron core can be inserted into the air gap when a short circuit occurs in the corresponding power system.

The air gap is in the shape of a closed mouth whose opening gradually becomes smaller along the insertion direction of the moving iron core.

The air gap includes a trapezoidal slot, and the notch of the trapezoidal slot gradually becomes smaller along the insertion direction of the moving iron core.

The air gap further includes a rectangular groove, and the groove sidewall of the rectangular groove is transitionally connected with the corresponding groove sidewall of the trapezoidal groove.

The trapezoidal slot is located on a side close to the moving iron core, and the rectangular slot is located on a side away from the moving iron core.

The current-limiting reactor with instantaneously adjustable reactance also includes an electromagnetic repulsion mechanism for driving the moving iron core to insert into the air gap when a short circuit occurs in the power system.

The moving iron core includes an insertion section for being inserted into the air gap driven by a corresponding driving mechanism and a connecting section for connecting with the driving mechanism, and the insertion section is along the moving iron core. The direction of insertion gradually shrinks.

The insertion section of the moving iron core is wedge-shaped, and the inclination angle of the wedge surface of the moving iron core is adapted to the opening angle of the air gap.

The static iron core has a rectangular shape, and the insertion direction of the moving iron core into the air gap is along a direction perpendicular to the side wall of the static iron core.

Beneficial effects of the present invention: when the power system is running, the moving iron core in the present invention moves away from the static iron core under the drive of the corresponding drive mechanism, leaving the position of the air gap of the static iron core and maintaining this state. At this time, the current-limiting reactor of the present invention is equivalent to a common current-limiting reactor. When the DC system fails, the current rises rapidly, the system protection device detects the current signal and sends the signal to the corresponding drive mechanism, the drive mechanism starts to move and drives the moving iron core to move towards the air gap of the static iron core, and the moving iron The core gradually enters the air gap. With the gradual reduction of the air gap, the reactance value of the reactor increases rapidly, and the response time is greatly shortened to 3-5ms, thereby achieving a better current limiting effect. The current-limiting reactor of the invention adopts the combination of dynamic and static iron cores, which not only meets the requirements of the power system to limit the fault current, but also better ensures the stability of the power system.

Description of drawings

Fig. 1 is the structural representation of the current-limiting reactor of instantaneous adjustable reactance of the present invention;

Fig. 2 is a schematic structural view of the static iron core in Fig. 1 .

detailed description

Embodiments of the current-limiting reactor with instantaneous adjustable reactance of the present invention: as shown in FIG. 1-2 , the current-limiting reactor includes a frame 5 , a static iron core 1 , a moving iron core 3 and a winding coil 2 . The winding coil 2 is arranged on the static iron core 1 , and the static iron core 1 is arranged on the frame 5 . The static iron core 1 is rectangular, and the static iron core 1 is surrounded by a long section 11 and a short section 12 , and the winding coil 2 is arranged on the left long section 11 . An air gap 13 passing through front and rear is opened on the short section 12 at the rear side. The air gap 13 is in the shape of a closed mouth whose opening gradually becomes smaller along the insertion direction of the moving iron core 3 . The air gap includes a trapezoidal groove 14 and a rectangular groove 15. The notch of the trapezoidal groove 14 gradually becomes smaller along the insertion direction of the moving iron core 3, that is, the width of the notch gradually becomes smaller. The cross section of the trapezoidal groove 14 is isosceles trapezoidal. The groove sidewalls of the rectangular groove 15 are transitionally connected with the corresponding groove sidewalls of the trapezoidal groove 14 . The trapezoidal slot 14 is located on the side close to the moving iron core, that is, on the rear side, and the rectangular slot 15 is located on the side away from the moving iron core. The occupied length of the rectangular groove 15 in the front-to-rear direction is smaller than the occupied length of the trapezoidal groove in the front-to-rear direction.

The moving iron core 3 includes an insertion section for being inserted into the air gap along the front and back direction under the drive of the corresponding driving mechanism and a connecting section for connecting with the driving mechanism. The insertion section shrinks gradually along the insertion direction of the moving iron core. The insertion direction of the moving iron core into the air gap is along the direction perpendicular to the side wall of the static iron core. In this embodiment, the insertion direction of the moving iron core 3 is perpendicular to the side wall of the short section 12 where the air gap is located. The insertion section of the moving iron core 3 is wedge-shaped, and the inclination angle of the wedge surface of the moving iron core 3 is adapted to the opening angle of the air gap. The groove walls on both sides are adapted, and the corresponding inclination angles are consistent. The current-limiting reactor also includes an electromagnetic repulsion mechanism 4 for driving the moving iron core to insert into the air gap when a short circuit occurs in the power system. The electromagnetic repulsion mechanism 4 includes two repulsion coils arranged in parallel and a repulsion disk located between the two repulsion coils. The connecting section of the moving iron core 3 is connected to the repulsion disk. When one of the repulsion coils is energized, the repulsion plate will push the moving iron core to move quickly from the repulsion coil to the direction of the other repulsion coil, otherwise, the other repulsion coil is energized, and the moving iron core will move in the opposite direction. The principle of the electromagnetic repulsion mechanism is the prior art.

As a further optimization, an air gap is provided on the long section on the left side of the static iron core, that is, at the position of the winding coil, so that the range of reactance change is larger when a short circuit occurs in the power system.

When the power system is in operation, the moving iron core 3 of the present invention moves backward under the drive of the electromagnetic repulsion mechanism 4 to break away from the air gap position of the static iron core 1 and maintain it. At this time, the present invention is equivalent to a common current-limiting reactor. When the DC system fails, the current rises rapidly, and the system protection device detects the current signal and sends the signal to the electromagnetic repulsion mechanism. The electromagnetic repulsion mechanism 4 starts to move and drives the moving iron core 3 to move forward. The insertion of the moving iron core 3 segment gradually enters the air gap. With the gradual reduction of the air gap, the reactance value of the reactor increases rapidly, and the response time is greatly shortened to 3-5ms, thereby achieving a better current limiting effect. The current-limiting reactor of the invention adopts the combination of dynamic and static iron cores, which not only meets the requirements of the power system to limit the fault current, but also better ensures the stability of the power system. The current-limiting reactor has simple structure, low operating loss, and adjustable inductive reactance transiently.

In this embodiment, the opening shape of the air gap adopts a structure combining trapezoidal grooves and rectangular grooves, mainly considering the convenience of processing. In other embodiments, the air gap can also be set in the structural form of only one trapezoidal slot, or only in the structural form of a rectangular slot, or in the structural form of an arc slot. Of course, the shape of the moving iron core should also be adaptively changed. , adapted to the shape of the air gap, for example, when the air gap is a rectangular slot, the insertion section of the moving iron core can be a quadrangular prism or a cylinder. In other embodiments, the moving iron core can also be inserted into the air gap along the up and down direction, and the air gap is in the shape of a closed mouth whose opening gradually becomes smaller from top to bottom.

In other embodiments, in addition to the above-mentioned electromagnetic repulsion mechanism, other types of drive mechanisms can also be used, which need to meet the requirements of fast response. For driving, an electric push rod can also be used. The electromagnetic repulsion mechanism can be a part of the current-limiting reactor, and it is assembled together when the product is manufactured. The electromagnetic repulsion mechanism may not be a part of the current-limiting reactor, and it is used in conjunction with the moving iron core when in use.

In other embodiments, the static iron core can also be a circular iron core.

Claims (9)

1. the current-limiting reactor of instantaneous regulative reactance, it is characterized in that: include static iron core, dynamic iron core and winding coil, winding coil is arranged on static iron core, and described static iron core is provided with air gap, and described dynamic iron core is inserted in described air gap when corresponding power system is short-circuited.

2. the current-limiting reactor of instantaneous regulative reactance according to claim 1, it is characterised in that: the closing in shape that described air gap is opening to be tapered into along the direction of insertion of described dynamic iron core.

3. the current-limiting reactor of instantaneous regulative reactance according to claim 2, it is characterised in that: described air gap includes dovetail groove, and the notch of described dovetail groove tapers into along the direction of insertion of described dynamic iron core.

4. the current-limiting reactor of instantaneous regulative reactance according to claim 3, it is characterised in that: described air gap also includes rectangular channel, and the groove side wall transition that the groove sidewall of described rectangular channel is corresponding with dovetail groove connects.

5. the current-limiting reactor of instantaneous regulative reactance according to claim 4, it is characterised in that: described dovetail groove is located close to the side of described dynamic iron core, and described rectangular channel is located remotely from the side of described dynamic iron core.

6. the current-limiting reactor of instantaneous regulative reactance according to claim 1, it is characterised in that: the current-limiting reactor of described instantaneous regulative reactance also includes for driving described dynamic iron core to be inserted into the electromagnetic repulsion force mechanism in described air gap when described power system is short-circuited.

7. the current-limiting reactor of the instantaneous regulative reactance according to any one of claim 2 to 5, it is characterized in that: described dynamic iron core includes the inserting paragraph for being inserted in described air gap under the driving of corresponding driving mechanism and the linkage section for being connected with described driving mechanism, and described inserting paragraph gradually tapers up along the direction of insertion of described dynamic iron core.

8. the current-limiting reactor of instantaneous regulative reactance according to claim 7, it is characterised in that: the inserting paragraph of described dynamic iron core is wedge shaped, and the angle of inclination of the wedge surface of described dynamic iron core is adaptive with the opening angle of air gap.

9. the current-limiting reactor of the instantaneous regulative reactance according to any one of claim 1 to 5, it is characterised in that: the rectangular shape of described static iron core, the direction of insertion being inserted in described air gap of described dynamic iron core is along the sidewall direction being perpendicular to described static iron core.