CN101872675A - Method for inhibiting ferroresonance - Google Patents

Abstract

The invention discloses a method for inhibiting ferroresonance. The method comprises the following steps of: (1) inferring the occurrence range and special working condition of the ferroresonance of a voltage transformer by an EMTP analytical method; (2) determining the excitation characteristic and coil internal resistance parameter of a saturable reactor; and (3) connecting the two connecting terminals of the saturable reactor which meets parameter condition with a secondary winding of the voltage transformer. The method can avoid VT heating damage and equipment damage accident due to the ferroresonance in a GIS power station effectively, eliminates the potential safety hazard of the possible ferroresonance in a power network system, and plays an important role in guaranteeing the safe operation of the power network; and therefore important social and economic benefits are generated.

Description

A kind of method that suppresses ferro resonance

Technical field

The present invention relates to a kind of GIS transformer station field, relate in particular to a kind of method that can suppress the ferro resonance that electromagnetic potential transformer causes.

Background technology

At present, be accompanied by carrying out in a large number of electric network reconstruction in all parts of the country and extension project, be low to moderate 10kV, bigger variation has all taken place high distribution structure to 500kV, this makes whole electrical network become more flexibly and is strong.But because electric network composition is complicated, infrequent ferro resonance phenomenon but happens occasionally now in the former electrical network.Particularly in present 550kV GIS (metal enclosed switchgear), between the circuit breaker fracture, generally dispose the shunt capacitor that improves the fracture voltage distribution character, when bus power failure operating breaker disconnected, the electromagnetic potential transformer on the bus might produce lasting low-frequency voltage (being the ferro resonance phenomenon) at this moment.By the direct-to-ground capacitance of the electric capacity between the circuit breaker fracture, GIS bus and the series LC loop that nonlinear inductance constituted of voltage transformer is the principal element that produces ferro resonance.

Single bus scheme figure with transformer station is an example, and as shown in Figure 1, when circuit breaker GCB2, GCB3 separating brake, when circuit breaker GCB1 disconnected at last, ferro resonance may take place voltage transformer VT.The GCB fracture disposes shunt capacitor, its secondary equivalent circuit such as Fig. 2.When ferro resonance takes place, the overvoltage amplitude of voltage transformer VT is generally not high, but exciting current is often very big, may reach the hundreds of of normal current even thousands of times, overlong time can be burnt coil, even causes the damage of voltage transformer VT and bring out even more serious power system accident.

Summary of the invention

The purpose of this invention is to provide a kind of method that suppresses ferro resonance, can avoid the power system accident that causes owing to ferro resonance effectively.

The present invention adopts following technical proposals: a kind of method that suppresses ferro resonance may further comprise the steps: (1), scope and the operating mode of utilizing EMTP analytic method deduction voltage transformer ferro resonance to take place; (2), determine the excitation property and the coil internal resistance parameter of saturable reactor; (3), two binding posts that will satisfy the saturable reactor of parameter condition are connected with the terminal of voltage transformer secondary winding.

Definite process of the parameter of saturable reactor is in the described step (2): according to the excitation property of voltage transformer, the fracture electric capacity of circuit breaker and the numerical value of bus direct-to-ground capacitance, the method validation that adopts EMTP to resolve makes the excitation property of saturable reactor and coil internal resistance saturated before satisfying when low-frequency voltage prior to voltage transformer, and consumes the energy of low-frequency voltage by the coil internal resistance.

The present invention is in the GIS power station, the voltage transformer VT heating that can avoid effectively causing owing to ferro resonance damages fault and device damage accident, can eliminate the potential safety hazard that ferro resonance may take place in the electric power networks system, important guaranteeing role is played in the safe operation of electrical network, thereby produce important society and economic benefit.

Description of drawings

Fig. 1 is the single bus scheme figure of transformer station;

Fig. 2 is the equivalent circuit figure of ferro resonance;

Fig. 3 is discharge (oscillation form) oscillogram of electrostatic capacitance;

Fig. 4 is the excitation property schematic diagram of voltage transformer;

Electric current when Fig. 5 is GIS bus direct-to-ground capacitance C2 discharge on the inductance L;

Fig. 6 is the waveform schematic diagram of voltage transformer secondary voltage 1/3 Subharmonic Resonance when ferro resonance takes place;

Fig. 7 is the waveform schematic diagram of voltage transformer secondary voltage 1/5 Subharmonic Resonance when ferro resonance takes place;

Fig. 8 is a ferro resonance occurrence scope schematic diagram;

The special operation condition schematic diagram of ferro resonance for taking place in Fig. 9;

Figure 10 is the winding diagram of voltage transformer and saturable reactor;

Figure 11 is the excitation property schematic diagram of voltage transformer and saturable reactor;

Figure 12 power station main electrical scheme schematic diagram;

Figure 13 does not install the EMTP analytic modell analytical model of saturable reactor additional;

Figure 14 installs the EMTP analytic modell analytical model behind the saturable reactor additional.

Embodiment

The present invention carries out theory analysis, emulation parsing and practical proof by the process that ferro resonance is produced, in conjunction with GIS power plant project actual parameter, utilize EMTP (electromagnetic transient state procedure, be to be used for the simulation software that electromagnetic transient in power system is analyzed,) scope of analytic method deduction voltage transformer VT ferro resonance generation and the parameter that special operation condition is also determined the saturable reactor, the saturable reactor is installed at the secondary side of voltage transformer VT, reaches and suppress the purpose that ferro resonance produces.

The phenomenon analysis that ferro resonance takes place: the equivalent circuit that is illustrated in figure 2 as ferro resonance, wherein R is a voltage transformer VT primary winding resistance, and L is the inductance of voltage transformer, and E is a supply voltage, C1 is the fracture electric capacity of circuit breaker, and C2 is a GIS bus direct-to-ground capacitance.

What (1) circuit breaker GCB had just disconnected is instantaneous, and electric charge (maximum is equivalent to the peak value of E) residual on the capacitor C 2 can discharge to inductance L.Capacitor C 2 generally very little (thousands of pF) generally, so its discharge voltage is a kind of low-frequency oscillation decay waveform, in the series loop that R, L, C form, is R when satisfying the certain parameter condition ²During＜4L/C, its discharge voltage as shown in Figure 3.Discharge voltage Uc on the C2 and discharging current i are respectively suc as formula shown in (1) and the formula (2):

$u_c=E\×e^{-\mathrm{\αt}}(\frac{\mathrm{\α}}{\mathrm{\β}}\sin \mathrm{\βt}+\cos \mathrm{\βt})---\left(1\right)$

$i=\frac{E}{\mathrm{\βL}}\×e^{-\mathrm{\αt}}\sin \mathrm{\βt}---\left(2\right)$

Wherein $\mathrm{\α}=\frac{R}{2L},\mathrm{\β}=\sqrt{\frac{1}{\mathrm{LC}}-{\mathrm{\α}}^2}$

(2) exciting characteristic curve of voltage transformer VT as shown in Figure 4, its inductance L shows as non-linear, the coil inductance when inductance L 1, L2 are respectively iron core unsaturated state, saturation condition.The relative unsaturation of the L2 in saturated zone zone L1 alter a great deal (hundred times that general L1 is about L2) in the excitation curve.During capacitor C 2 discharges, electric current variation tendency such as Fig. 5 on the L, the duty cycle of voltage transformer VT is: O → A → B → A → O → C → D → C → O;

(3) after circuit breaker GCB disconnects, can bear the induced voltage that produces by power supply E on the inductance L, numerical value is EC1/ (C1+C2), oscillatory extinction waveform among itself and Fig. 3 will superpose and the oscillating voltage of compensate for attenuation, if this induced voltage is enough big and its phase place when at a time just close with the low-frequency voltage phase place that decays, the amplitude of low-frequency voltage is raise and lasting the existence, and promptly ferro resonance has taken place in voltage transformer VT.This moment, resonance frequency was generally 1/3,1/5,1/7 times of power frequency.Utilize waveform example that EMTP secondary voltage that ferro resonance resolves takes place to VT as shown in Figure 6 and Figure 7.

By the top described phenomenon analysis that ferro resonance is produced, need suppress the generation of ferro resonance with the method for the invention, the method that the present invention suppresses ferro resonance may further comprise the steps:

1,, utilize the EMTP analytic method to infer scope and special operation condition that the VT ferro resonance takes place in conjunction with GIS power plant project actual parameter;

It is closely related to utilize the EMTP analytic method to infer to verify out voltage transformer VT that the parameter of ferro resonance phenomenon and capacitor C 1, C2 takes place.As standardized product, the shunt capacitance C1 that switch manufactory disposes in circuit breaker GCB is generally preset parameter (C1 numerical value relates to GCB and cut-offs the platform number), C2 numerical value is relevant with the GIS bus length, C2 is more little, the inductive voltage value of circuit breaker GCB incision position is big more, it is big more that the ferro resonance probability takes place, and Fig. 8 is a ferro resonance occurrence scope schematic diagram;

The special operation condition of ferro resonance takes place: T district in the string of 3/2 wiring (or 4/3 wiring), referring to Fig. 9.This moment, line-breaker DS was in gate-dividing state, and C2 is very little for the bus direct-to-ground capacitance, and ferro resonance can take place voltage transformer VT in the string.

2, determine the parameter of saturable reactor;

The magnetic saturation voltage of saturable reactor is lower than voltage transformer VT, in conjunction with capacitor C 1, the parameter of the numerical value appropriate design saturable reactor of C2: excitation property and coil internal resistance, parameter determines that benchmark is: assurance saturable reactor is worked under high flux density and a rapid saturation condition is provided, when the ferro resonance operating mode takes place when, the saturable reactor is saturated before prior to VT when low-frequency voltage, and consume the energy of low-frequency voltage by its coil internal resistance, thereby suppress the generation of ferro resonance phenomenon, as shown in figure 11, curve 3 is the excitation property schematic diagram of voltage transformer VT, and curve 4 is the excitation property schematic diagram of saturable reactor.The parameter designing of saturable reactor will adopt the method for EMTP parsing to be verified in conjunction with the excitation property of voltage transformer VT, the numerical value of C1, C2 etc. usually on the engineering, thereby draws the parameter of required saturable reactor.The saturable reactor generally only consumes the burden of several VA, and is very little to the influence of voltage transformer VT error characteristics, and heating hardly, is the device that effectively suppresses ferro resonance.

3, connect needed saturable reactor at voltage transformer VT secondary side;

The saturable reactor can adopt the method for installing with voltage transformer VT one, promptly in the secondary terminal box of voltage transformer VT, install the saturable reactor additional, two binding posts of saturable reactor are connected with the terminal of secondary winding in the secondary terminal box of voltage transformer VT respectively, this kind mode is comparatively succinct, other external equipment is not exerted an influence, exchange but need to carry out the GIS relevant parameter with VT manufacturer in advance.

In addition, also can adopt in the voltage transformer VT outside (as in convergence control cabinet or independent control cabinet is set) install the method for saturable reactor additional.In the convergence control cabinet wiring of voltage transformer VT secondary circuit as shown in figure 10, two binding posts of saturable reactor 11,12,13 are connected with the terminal of threephase potential transformer VT outside secondary winding respectively.

Figure 12 is a string 4/3 main electrical scheme signal in certain power station, and two circuit VT are arranged on T district (may have special operation condition) in the string, and the ferro resonance phenomenon has taken place during the commissioning test for the first time of scene.Verify also that by the EMTP analytic method resonance can take place at the individual phase angle of cut-offfing at circuit breaker GCB, analytic modell analytical model as shown in figure 13, except that C1 and C2, the parameter that relates to also has primary winding impedance Z 1, iron loss T and the nonlinear inductance excitation property etc. of VT.As shown in figure 14, after adding saturable reactor VT3, R3 is the internal resistance of saturable reactor, and Z2 is the secondary coil impedance of voltage transformer VT, analytic modell analytical model is adjusted, ferro resonance inhibition situation is confirmed (resonance phenomena can be suppressed) by the EMTP analytic method.

Claims (2)

1. a method that suppresses ferro resonance is characterized in that: may further comprise the steps: (1), scope and the operating mode of utilizing EMTP analytic method deduction voltage transformer ferro resonance to take place; (2), determine the excitation property and the coil internal resistance parameter of saturable reactor; (3), two binding posts that will satisfy the saturable reactor of parameter condition are connected with the secondary winding of voltage transformer.

2. the method for inhibition ferro resonance according to claim 1, it is characterized in that: definite process of the parameter of saturable reactor is in the described step (2): according to the numerical value of excitation property, breaker port electric capacity and the bus direct-to-ground capacitance of voltage transformer, the method validation that adopts EMTP to resolve makes the excitation property of saturable reactor and coil internal resistance saturated before satisfying when low-frequency voltage prior to voltage transformer, and consumes the energy of low-frequency voltage by the coil internal resistance.

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