CN2655487Y - Fault current-limiter used on magnetic flux compensation - Google Patents

Abstract

The utility model discloses an accident amperite based on a flux compensation, mainly comprising a coupling transformer, a crystal switch pipe, a direct current-limiting reactor, a current detecting unit and the like, wherein each phase of the coupling transformer comprise three winding groups, namely one original line winding group and two independent side line winding group, one side line winding group is connected with a current-limiting circuit comprising the crystal switch pipe and the direct current-limiting reactor, the other side line winding group can be connected with a controllable permanent current source, the circuit detecting unit is connected between an alternating power source and the coupling transformer, and the accident ampeite can be equipped with a side rout inductance. When the system operates normally, the affect on the load is quite small.

Description

A kind of fault current limiter based on flux compensation

Technical field:

The utility model is a kind of grid short circuit failure of the current flow restricter that is used to limit, particularly a kind of fault current limiter with coupling transformer.

Background technology:

In fault current limiter, the technical scheme that with the patent No. is ZL02112334.9 is the typical case.When line voltage is higher, it no matter is single-phase or three-phase system, all every coupling transformer that is made of double winding is connected between AC power and the load, when system does not have the short trouble operation, by making the secondary short circuit in winding of each phase of coupling transformer, thereby every phase short-circuit impedance of coupling transformer is connected between the corresponding power supply and load.Because the perceptual short-circuit impedance value of coupling transformer is bigger, when therefore not having the short trouble operation in system, certainly will produce bigger voltage drop at the two ends of coupling transformer, corresponding load both end voltage also descends significantly, therefore the normal operation to load has produced bigger influence, this with to the basic demand of fault current limiter, the requirement of when promptly system normally moves load not being had an influence deviates from mutually.

Summary of the invention:

The technical solution of the utility model is the above-mentioned defective at prior art, and a kind of fault current limiter based on flux compensation is provided, and solves the problem that influences to the electrical network load.

The technical solution of the utility model: fault current limiter of the present utility model, each is made up of its coupling transformer three windings, i.e. former limit winding and two secondary winding independently.One of them secondary winding is connected with the current-limiting circuit of being made up of thyristor, direct current current-limiting reactor, and another secondary winding then is connected with a controlled constant-current source.Current detecting unit is connected between AC power and the coupling transformer.

The coupling transformer of fault current limiter of the present utility model can be made up of three and a single-phase coupling transformer; Can be three-phase also, and load be earth-free; Also can be three-phase, and load ground connection.

Above-mentioned fault current limiter can have by-pass inductor, and it is in parallel with the former limit winding of coupling transformer to exchange by-pass inductor.

Advantage of the present utility model: because the utility model has adopted novel structure, when in electrical network, moving, the fault current limiter control system can be according to the testing result of current detecting unit, make the magnetic potential of the secondary winding generation that is connected with controlled constant-current source by the mode of forced excitation, former limit winding excitation magnetic potential when being zero with controlled constant-current source output current is cancelled each other, and is zero thereby make the main flux of coupling transformer.Thereby realize that coupling transformer resistance value connect with load descends significantly, the both end voltage of while coupling transformer is decline significantly also, to the load both end voltage and the influence when normally moving very little, almost do not have.Therefore in electrical network, adopt fault current limiter of the present utility model, can avoid influence the load pressure drop.

Description of drawings

Fig. 1 coupling transformer is three winding constructions, based on the single-phase fault flow restricter that has by-pass inductor of flux compensation

Fig. 2 by three coupling transformers be three winding constructions, the three-phase fault flow restricter that constitutes based on the single-phase fault flow restricter that has by-pass inductor of flux compensation

Fig. 3 coupling transformer is three winding constructions, have an earth-free fault current limiter of by-pass inductor three-phase based on flux compensation

Fig. 4 coupling transformer is three winding constructions, based on the three-phase earth fault flow restricter that has by-pass inductor of flux compensation

Equivalent circuit diagram when the single-phase double winding coupling transformer of Fig. 5 normally moves in system

When Fig. 6 main flux is zero, has the single-phase coupling transformer equivalent circuit diagram of three winding constructions

Among the figure: T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18------thyristor

V _S, V _a, V _b, V _C,

------AC power

R------load X ₁--the former limit of----coupling transformer leakage field induction reactance

R ₁------conductor resistance X ₁X ₃-----coupling transformer secondary leakage field induction reactance

R ₂' R ₃'--reduction of----conductor resistance is to the respective value on former limit

-------power network line electric current

The reduction of-----coupling transformer secondary current is to the respective value on former limit

The current-limiting circuit 4-----power network line current detecting unit 5-----that the controlled constant-current source 3-----of 1-----coupling transformer 2-----is made up of thyristor and direct current reactor exchanges by-pass inductor

Embodiment:

Fault current limiter based on flux compensation, no matter be single-phase fault flow restricter (Fig. 1), by three single-phase three-phase fault flow restricters of forming (Fig. 2), perhaps the three-phase of You Huaing earth-free (Fig. 3), earth fault flow restricter (Fig. 4) all have identical circuit structure.Be coupling transformer (1) by a former limit winding and two independently the secondary winding form, a secondary winding of coupling transformer (1) is connected with controlled constant-current source (2), another secondary winding then is connected with the current-limiting circuit of being made up of thyristor and direct current reactor (3), and power network line current detecting unit (4) is connected between AC power and the coupling transformer (1).This fault current limiter can have interchange by-pass inductor (5) in addition, and it is then in parallel with the former limit winding of coupling transformer (1) to exchange by-pass inductor (5).

Fig. 5 is the equivalent circuit diagram of single-phase double winding coupling transformer when its secondary short circuit in winding, this moment circuit equiva lent impedance to be primary impedance convert the connecting of impedance on former limit with secondary, this equivalence impedance is bigger, when system normally moves, because flowing through the electric current of this impedance is load current, therefore cause the former limit of coupling transformer to produce bigger voltage drop, voltage to the load two ends also produces bigger influence accordingly, thereby will produce big influence to the normal operation of load.

Fig. 6 is after adopting the utility model, when coupling transformer does not have the short trouble operation in system etc., imitate circuit diagram, because main flux is zero, this moment, the equiva lent impedance of coupling transformer only was primary impedance, and this impedance will be much smaller than the short-circuit impedance of double winding coupling transformer.Be similarly load current owing to flow through the electric current of this impedance, the voltage drop when the former limit of coupling transformer is normally moved in system reduces significantly, will be very little to the influence on system operation of load.

For three winding coupled transformers (1), output current when Control current source (2) is zero, then the secondary winding that is connected with controlled constant-current source (2) is in open-circuit condition, three winding coupled transformer (1) equivalences this moment are a two winding transformer, equivalent circuit diagram is identical with Fig. 5, and corresponding magnetic potential equation is:

${{\stackrel{\&CenterDot;}{I}}_{m}N}_1={\stackrel{\&CenterDot;}{I}}_1{N}_1+\stackrel{\&CenterDot;}{{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="Y0326328000071.png"\; state="\{\{state\}\}">I</figure-callout>}}_2^{\&prime;}}{N}_1$

N ₁--the number of turn of the exciting curent of----coupling transformer (1), former limit winding.Wherein

Be used to produce interior main flux unshakable in one's determination, its effective value is smaller.

By following formula as can be known, the electric current that flows through the secondary winding that is connected with the current-limiting circuit of being made up of thyristor and direct current reactor (3) produces magnetic potential, the vector of the magnetic potential that produces on the former limit of coupling transformer (1) with the power network line electric current and, be the magnetic potential that exciting curent produces, this excitation magnetic potential is non-vanishing.

When system does not have the short trouble operation, according to power network line current detecting unit (4) testing result, control the output of controlled constant-current source (2), make its output current be connected coupling transformer (1) magnetic potential that secondary produced with it, when being zero with the output current of controlled constant-current source (2), the excitation magnetic potential of coupling transformer (1) offsets, and then Ci Shi magnetic potential equation is:

${\stackrel{\&CenterDot;}{I}}_m{N}_1={\stackrel{\&CenterDot;}{I}}_1{N}_1+\stackrel{\&CenterDot;}{{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="Y0326328000071.png"\; state="\{\{state\}\}">I</figure-callout>}}_2^{\&prime;}}{N}_1+\stackrel{\&CenterDot;}{{\mathrm{<figure-callout\; id="3"\; label="I"\; filenames="Y0326328000092.png"\; state="\{\{state\}\}">I</figure-callout>}}_3^{\&prime;}}{N}_1=0$

This moment, the main flux of three winding coupled transformers was zero, and equivalent electric circuit as shown in Figure 6.

Therefore when electrical network normally moves, adopt fault current limiter of the present utility model, very little for the influence of load, almost do not have.

Claims (5)

1, a kind of fault current limiter based on flux compensation mainly partly is made up of coupling transformer, thyristor, direct current current-limiting reactor, current detecting unit etc.; It is characterized in that: each of coupling transformer all is made up of three windings mutually, promptly by a former limit winding and two independently the secondary winding form; One of them secondary winding is connected with the current-limiting circuit of being made up of thyristor, direct current current-limiting reactor, and another secondary winding then is connected with a controlled constant-current source; Current detecting unit is connected between AC power and the coupling transformer.

2, a kind of fault current limiter based on flux compensation according to claim 1 is characterized in that: be made up of one or three coupling transformers, its coupling transformer is single-phase.

3, a kind of fault current limiter based on flux compensation according to claim 1, it is characterized in that: its coupling transformer is a three-phase, and load is earth-free.

4, a kind of fault current limiter based on flux compensation according to claim 1, it is characterized in that: its coupling transformer is a three-phase, and load ground connection.

5, according to claim 1,2,3 or 4 described a kind of fault current limiters based on flux compensation, it is characterized in that: this fault current limiter can have the bypass AC inductance, and exchanges each the former limit winding parallel connection mutually of by-pass inductor and coupling transformer.

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