CN202424148U - Normal conductor direct current coil-based saturated core fault current limiter - Google Patents

Abstract

The utility model relates to a normal conductor direct current coil-based saturated core fault current limiter. The fault current limiter is formed by coupling a control coil, a working coil and a core through a magnetic field, wherein the control coil is formed by winding a normal conductor, is connected with an external direct current excitation power supply, and has a quick magnetization loop matched with reclosing action and a quick demagnetization loop matched with the current limiter during switching from a power grid steady state to a power grid transient state. The fault current limiter is based on a magnetoresistance effect principle, and power grid running conditions in the steady state, transient state, reclosing state and the like of a power system and requirements for the fault current limiter are fully taken into account.

Description

Based on the core sataration type fault current limiter of often leading dc coil

Technical field

The utility model relates to a kind of Power System Shortcuts current limiting device, a kind of specifically core sataration type fault current limiter based on dc coil that strengthens power system safety and stability property, can suppress short circuit current to reasonable level.

Background technology

Along with ultra extra-high voltage grid form; The operation of regional power grid looped network; The construction of intelligent grid, have little power supply of distributed nature continuous access electrical network (distribution decline helping of power supply increase the effect make fault current further increase); The big load area property of city and industrial area is concentrated, and electric power system is faced with a new difficult problem, and promptly the short circuit current of each electric pressure constantly increases, and has surpassed the rupturing capacity of circuit breaker.The increase of short circuit current level, this requires the voltage endurance capability of power transmission and transforming equipment further to improve.Measures such as the upgrading of electrical network planning again with it, transformer station and circuit, electrical network fanout operation are compared, and fault current limiter is that a kind of investment is little, one of obvious results method of fault current limiting.

Fault current limiter can be divided into according to its principle of compositionality: solid-state current limiter, PTC (Positive Temperature Coefficient; Positive temperature coefficient) resistance flow restricter, superconductive current limiter and various mixing type current-limiting device, research both at home and abroad at present is more to be solid-state current limiter such as ABB etc., impedance type superconductive current limiter such as Siemens etc. and magnetic saturation type superconductive current limiter such as Zenergy and cloud electricity Ying Na etc.Wherein solid-state current limiter is that power electronic equipment is used in electric power system in large quantities; Adopt power electronic device such as GTO, SCR, IGBT when electric network fault; Fast reaction; Turn-off low resistance circuit, open high resistance circuit and realize current limliting mainly containing GTO switching mode flow restricter, SCR resonant mode flow restricter, SCR variableimpedance formula flow restricter, transformer coupled formula flow restricter etc.PTC resistance flow restricter utilizes the positive nonlinear temperature resistance characteristic of ptc material to carry out current limliting; When system's failed because, short circuit current causes ptc material heating expansion, and increasing sharply of resistance temperature makes the resistance value of PTC flow restricter sharply increase, thereby plays the effect of fault current limiting.

Superconductive failure current limiter, the quench characteristic current limliting according to whether utilizing superconductor can be divided into quench type and non-quench type; Design feature according to flow restricter can be divided into resistor-type, bridge circuit type, magnetic screen type, transformer type, saturable core type etc.Wherein, Active saturable core type superconductive failure current limiter is coupled to form by superconducting coil, iron core, normal loop and excitation system, control system etc.; Integrate detection, triggering and current limliting; Utilize the zero resistance characteristic or the complete diamagnetism of superconductor, form the purpose that special topological structure reaches the restriction system short circuit current by superconducting coil and other devices.The active control system that is embodied in is monitored the operation of power networks situation in real time, makes corresponding judgment and control strategy according to ruuning situation; The saturable core type mainly is to utilize iron core B curve, when the degree of depth is saturated, is characterized by low resistance state, in unsaturation when zone, is characterized by high-impedance state, thus this kind flow restricter has had stable state low-resistance, current limliting high resistant, from four big characteristics such as dynamic response, fast quick-recoveries.According to design demand; Superconductive current limiter can be restricted to the level that electrical network can bear with short circuit current, effectively solves the harm of short circuit current to system and electric equipment, reduces economic loss; Reducing the power grid construction cost, is a kind of effective measures that promote electric power development, improve the power grid security reliability.

There is following problem respectively in several kinds of current flow restricters: solid-state current limiter depends on the development level of power electronic device; PTC type flow restricter is limited by ptc material can not repeatedly be used etc.; The impedance type superconductive failure current limiter can not cooperate various operation conditionss such as reclosing of electric power system etc. effectively; Core sataration type superconductive failure current limiter; Build superconducting tape and not only cost an arm and a leg, install that to take up an area of the space big with the superconduction environment, and the solder technology requirement height of superconduction and the joint of often leading; Influenced applying of fault current limiter (FCL, Fault Current Limiter).

The utility model content

To superconductive failure current limiter in the prior art can not cooperate effectively electric power system various operation conditionss, install to take up an area of weak points such as the space is big, the technical problem that the utility model will solve provide a kind of do not need to be run in the harsh low temperature environment and low cost of manufacture, install floor space little based on the core sataration type fault current limiter of often leading dc coil.

For solving the problems of the technologies described above, the technical scheme that the utility model adopts is:

The utility model is a kind of to be coupled to form through magnetic field by control coil, actuating coil and iron core based on the core sataration type fault current limiter of often leading dc coil, and wherein control coil adopts lead coiling often to form.

The external dc excitation power of said control coil has magnetize fast loop and the quick de-excitation loop that cooperates flow restricter to switch from the electrical network stable state to electrical network transient state that cooperate the reclosing action; Iron core has the structure of the saturated direct current flux of the guiding degree of depth, promptly adopts the intersection lamination, adopts the arc interface in the junction of magnetic post and yoke; The winding mode of said control coil forms coil for the series connection of line cake, and parallel connection forms the control winding again.

The utlity model has following beneficial effect and advantage:

1. the utility model is based on the magneto resistance effect principle, considered the operation of power networks situation of states such as power system mesomeric state, transient state and reclosing fully and to the requirement of fault current limiter.

2. no longer receive the restriction of superconducting tape based on the fault current limiter of normal loop, also do not need to be run in the harsh superconduction low temperature environment, and manufacturing cost is low relatively, the installation floor space is relatively little.

Description of drawings

Fig. 1 is the single-phase design loose coupling of a utility model structure principle chart;

Two reactor primary side series connection of Fig. 2 the utility model, secondary side anti is to the parallel-connection structure schematic diagram;

B/H curve when Fig. 3 the utility model is in saturated mode;

B/H curve when Fig. 4 the utility model is in the current limliting attitude.

Embodiment

Below in conjunction with Figure of description the utility model is done further to set forth.

Like Fig. 1, shown in 2; The utility model is a kind of to be coupled to form through magnetic field by control coil (being dc coil), actuating coil (being AC coil) and iron core based on the core sataration type fault current limiter of often leading dc coil, and wherein control coil adopts lead coiling often to form.The external dc excitation power of control coil.

The utility model is the characteristic according to FCL, and (magnetic field is in degree of depth saturation region, and resistance is minimum to use the magnetic saturation principle; At non-saturated region, resistance is very big), a kind of fault current limiter of designing is made up of actuating coil, control coil and iron core etc., and the three is coupled through magnetic field.From the electric power system angle, its running status is divided into three kinds of stable state, fault case and reclosings etc.During stable state, the direct current in the control coil is enough big, makes iron core be in saturation condition, and the impedance of actuating coil is characterized by low resistance state; During the fault transition state, the control coil direct current breaks off, and iron core is in the unsaturation attitude, and actuating coil is characterized by high-impedance state; During the operation of reclosing state, control coil magnetizes to iron core fast, guarantees before the reclosing action, guarantees that actuating coil is in super-saturated magnetic field.From faulty line device angle, be divided into two kinds of over-saturation state and unsaturated state etc.Analyze principle (according to the mark of Fig. 1) respectively from circuit and magnetic path connection below based on the fault current limiter of often leading dc coil (NFCL-Normal Fault Current Limiter).The magnetic circuit equation is:

$\left.\begin{array}{c}{H}_1{L}_1+H_{\mathrm{dc}}L=N_{\mathrm{dc}}{I}_{\mathrm{dc}}+N_{\mathrm{ac}}{I}_{\mathrm{ac}}\\ H_2{L}_2+H_{\mathrm{dc}}L=N_{\mathrm{dc}}{I}_{\mathrm{dc}}-N_{\mathrm{ac}}{I}_{\mathrm{ac}}\end{array}\right\}$

Wherein, H ₁, H ₂Be respectively the magnetic field intensity of actuating coil among Fig. 1, L ₁, L ₂Be respectively the length of the actuating coil among Fig. 1, N _AcBe the number of turn of actuating coil, I _AcElectric current for actuating coil; H _DcBe the magnetic field intensity of direct-flow magnet exciting coil, I _DcBe the electric current in the direct-flow magnet exciting coil, N _DcThe number of turn for direct-flow magnet exciting coil.

Circuit equation is:

Wherein, u ₁, u ₂Be respectively the voltage at actuating coil two ends among Fig. 1, u _DcBe the voltage of DC power supply, r ₁, r ₂Be respectively the impedance of actuating coil among Fig. 1, N _AcBe the number of turn of actuating coil, i _AcBe the electric current of actuating coil,

Be respectively the magnetic flux of actuating coil among Fig. 1; r _DcBe the impedance of control coil, i _DcBe the electric current in the direct-flow magnet exciting coil, N _DcBe the number of turn of direct-flow magnet exciting coil, Magnetic flux for control coil.

NFCL is similar to transformer device structure, but in order to be fit to the quick switching in degree of depth saturation magnetic field and unsaturated magnetic field, its core structure, winding connection mode etc. are special.The particularity of iron core not only is embodied in the selection, and embodies structurally.Its selection is: if low power flow restricter or to the specific (special) requirements again of the volume of flow restricter is selected iron-nickel alloy for use; High-power, use cold-reduced silicon sheet; Because flow restricter when power system mesomeric state moves, is operated in the over-saturation magnetic field, iron core can not use stacked simply, and is to use the intersection lamination, magnetic post, yoke Optimization Design, and more helping saturation flux passes through; In the junction of magnetic post and yoke, adopt the arc interface, further avoid magnetic hysteresis loss; Need add simultaneously and have the quick-response excitation loop and dc excitation power such as the loop of magnetizing fast.General transformer is operated in unsaturated state, and the magnetic saturation type fault current limiter must operate at saturation condition and presents low configuration when being operated in stable state; When transient state, be operated in unsaturated state, must present high-impedance state.Can get from the magnetic circuit equation, because the magnetic flux that two parts AC coil forms, at the iron core place of dc coil, equal and opposite in direction, in the opposite direction, no matter be stable state, fault case or reclosing operate condition therefore, the electromagnetic effect of dc coil is zero.

During stable state, saturation must keep 2 π; Two ends at actuating coil are respectively:

B _dc-B _ac＝KB _s

K is a safety factor in the formula, must be more than or equal to 1; B _DcBe the electromagnetic intensity in the dc coil; B _AcBe the electromagnetic intensity in the AC coil; B _sSaturation value for the electromagnetic intensity in the AC coil.

During transient state, the DC excitation loop is broken off.This moment should for

B _ac＝K′B _s

K ' should be less than 1 in the formula.

When stable state, be in the over-saturation zone, the magnetic flux density rate of change of actuating coil is approximately equal to zero.Circuit equation can be written as:

$\left.\begin{array}{c}{u}_1=r_1{i}_{\mathrm{ac}}\\ u_2=r_2{i}_{\mathrm{ac}}\\ u_{\mathrm{dc}}=r_{\mathrm{dc}}{i}_{\mathrm{dc}}\end{array}\right\}$

During electric network fault: transform from being saturated to undersaturated state, the electric current in the actuating coil increases suddenly, and the synchronous direct current in the control coil withdraws from, and circuit equation is reduced to:

Require actuating coil to be in saturation condition during the reclosing state, its circuit equation is identical during with stable state.

On core sataration type fault current limiter, control coil is under the effect of DC power supply, and forming saturation magnetic field is one of key technology.Therefore control coil can be not only fast but also magnetic field and the iron core that can form big magnetic induction intensity fast the transmission of direct magnetic flux become emphasis and the difficult point of paying close attention on the core sataration type fault current limiter structure.

The design of transformer coil structure mainly is for the transmission of energy and conversion, and the control coil of NFCL is mainly in order to form bigger magnetic field intensity.Therefore, the control coil of NFCL uses line cake series connection back parallel way earlier.Its rationale is:

$\left.\begin{array}{c}\mathrm{NI}=\mathrm{HL}=\frac{B}{\mathrm{\μ}}L\\ \mathrm{\φ}=\mathrm{BS}\end{array}\right\}$

Wherein, N is the number of turn of control coil; I is a Control current; H is a magnetic field intensity; B is a magnetic flux density; μ is a magnetic permeability; φ magnetic flux; S is a sectional area; L is the length of coil.Let actuating coil be operated in the degree of depth saturation magnetic field in order to form, the mode of implementation that control coil is best for going here and there and optimizing.

The iron core of NFCL mainly transmits the direct current flux amount and guarantees that the running environment of actuating coil is in the height saturated mode in the electrical network stable state, and the AC magnetism flux that when electrical network transient state, transmits.The transmission of direct magnetic flux is not only played in the design of iron core, and plays and impel the magnetic flux closed loop, lowers the effect of the loss of NFCL.Therefore, the iron core of NFCL has the special construction of guiding direct current flux passage.The particularity of iron core not only is embodied in the selection, and structurally.Use cold-reduced silicon sheet; Because flow restricter when power system mesomeric state moves, is operated in the over-saturation magnetic field, iron core can not use stacked simply, uses the intersection lamination, and magnetic post, yoke Optimization Design more help saturation flux and pass through; In the junction of magnetic post and yoke, adopt the arc interface, further reduce magnetic hysteresis loss; For the little flow restricter of capacity, adopt the structure of volume iron core.

Can know that from above analysis control coil just plays to let and ferromagneticly reaches degree of depth magnetic saturation and withdraw from saturated.Because superconducting coil is under the effect of high-intensity magnetic field; Its critical current is reduced greatly, and thus, formation lets the magnetic field of core sataration need more superconducting tape; And superconducting coil only could be realized its superconducting characteristic in the superconduction environment; The low-temperature superconducting environment not only needs investment, and loss is big, and certain floor space is arranged.Use the material of normal loop, according to above analysis, as long as auxiliary circuit can be realized the requirement of NFCL to magnetizing with the demagnetization rapidity as dc coil.Fault current limiter based on normal loop can be realized " stable state low-resistance, transient state high resistant; Active monitoring, fast quick-recovery " etc. characteristic.And normal loop price is low, no maximum critical electric current restriction.In addition, do not need extra low-temperature superconducting environment based on the fault current limiter of normal loop, floor space is little.

According to the figure that designs a model, the NFCL dc coil is connected DC power supply, forms DC loop; The AC coil series connection inserts in the power network line.NFCL controls the size of magnetic flux through the break-make of DC loop and the size of direct current, thereby makes the ferromagnetic saturated mode that is in.According to the basic principle of magneto resistance effect, when coil was in the degree of depth saturation magnetic field, its resistance characterization was a minimum; When coil was in the unsaturation magnetic field, its resistance characterization was big value.For this state, NFCL is divided into saturated mode and current limliting attitude, corresponds respectively to steady operation, reclosing action and the fault case of electric power system.

When electric power system was in steady operation, like Fig. 1, through enough big electric current, the iron core electromagnetism was biased to degree of depth saturated mode in the dc coil; AC coil is in the high magnetic field intensity, and it is characterized by little impedance, in such cases; NFCL is in saturated mode, and the B/H curve of this moment is as shown in Figure 3, H _AcBe the magnetic field intensity in the AC coil.Series connection inserts the NFCL in the electrical network, because its impedance is little, almost can ignore; When line failure, DC loop breaks off, and iron core withdraws from saturated; AC coil is characterized by big impedance, and in such cases, NFCL is in the current limliting attitude; The B/H curve of this moment is as shown in Figure 4; Series connection inserts the NFCL in the electrical network because its impedance is big, can limiting short-circuit current within the capacity of short circuit of circuit breaker.

Claims (4)

1. one kind based on the core sataration type fault current limiter of often leading dc coil, it is characterized in that: be coupled to form through magnetic field by control coil, actuating coil and iron core, wherein control coil adopts lead coiling often to form.

2. described based on the core sataration type fault current limiter of often leading dc coil by claim 1; It is characterized in that: the external dc excitation power of said control coil has magnetize fast loop and the quick de-excitation loop that cooperates flow restricter to switch from the electrical network stable state to electrical network transient state that cooperate the reclosing action.

3. by the described core sataration type fault current limiter of often leading dc coil of claim 1, it is characterized in that: iron core has the structure of the saturated direct current flux of the guiding degree of depth, promptly adopts the intersection lamination, adopts the arc interface in the junction of magnetic post and yoke.

4. by the described core sataration type fault current limiter of often leading dc coil of claim 1, it is characterized in that: the winding mode of said control coil is: the series connection of line cake forms coil, and parallel connection forms the control winding again.

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