CN101872675B - 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 working condition of the ferroresonance of a voltage transformer by an EMTP analytical method: the smaller the capacitor of a GIS bus over the ground, the bigger the probability of the ferroresonance, wherein the working condition is intra-string T zone of 3/2 wiring or 4/3 wiring, at this time a circuit breaker is in a separating brake state, the capacitor of the bus over the ground is small, and an intra-string voltage mutual inductor will have the ferroresonance; (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 with 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 broke off, 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 example, and is as shown in Figure 1, and when circuit breaker GCB2, GCB3 separating brake, when circuit breaker GCB1 broke off 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, possibly reach hundreds of even thousands of times of normal current; 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), utilize the EMTP analytic method to infer scope and operating mode that the voltage transformer ferro resonance takes place: GIS bus direct-to-ground capacitance is more little, and the probability that ferro resonance takes place is big more; Wherein operating mode is the interior T district of string of 3/2 wiring or 4/3 wiring, and this moment, line-breaker was in gate-dividing state, and the bus direct-to-ground capacitance is very little, and ferro resonance can take place voltage transformer in the string; (2), confirm the excitation property and the coil internal resistance parameter of saturable reactor; Two binding posts that (3), will satisfy the saturable reactor of parameter condition are connected with the secondary winding of voltage transformer; The Determination of Parameters process of saturable reactor is in the wherein said 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 excitation property that the method validation that adopts EMTP to resolve makes the saturable reactor and coil internal resistance are satisfied when low-frequency voltage prior to saturated before the voltage transformer, and the energy through coil internal resistance consumption low-frequency voltage.

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 possibly 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 sketch map 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 sketch map of voltage transformer secondary voltage 1/3 Subharmonic Resonance when ferro resonance takes place;

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

Fig. 8 is a ferro resonance occurrence scope sketch map;

The special operation condition sketch map 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 sketch map of voltage transformer and saturable reactor;

Figure 12 power station main electrical scheme sketch map;

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 through the process that ferro resonance is produced; In conjunction with GIS power plant project actual parameter; Utilize EMTP (electromagnetic transient state procedure is to be used for the simulation software that electromagnetic transient in power system is analyzed) analytic method to infer scope and the special operation condition that voltage transformer VT ferro resonance takes place and confirm the parameter of 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 broken off 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 is as shown in Figure 3.Discharge voltage Uc that C2 is last 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 is as shown in Figure 4, and 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 that L is last, the duty cycle of voltage transformer VT is: O → A → B → A → O → C → D → C → O;

(3) after circuit breaker GCB breaks off; Can bear the induced voltage that produces by power supply E on the inductance L; Numerical value is EC1/ (C1+C2), and the 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 for example Fig. 6 and shown in Figure 7 of waveform that EMTP secondary voltage that ferro resonance resolves takes place to VT.

Through the top said 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, combines GIS power plant project actual parameter, utilize the EMTP analytic method to infer scope and special operation condition that the VT ferro resonance takes place;

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, and C2 is more little, and 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 sketch map;

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, confirm the parameter of saturable reactor;

The magnetic saturation voltage of saturable reactor is lower than voltage transformer VT; Parameter in conjunction with the numerical value appropriate design saturable reactor of capacitor C 1, C2: excitation property and coil internal resistance, parameter confirms that benchmark is: guarantee that the saturable reactor works and a rapid saturation condition is provided under high flux density, when the ferro resonance operating mode takes place; The saturable reactor is before saturated prior to VT when low-frequency voltage; And pass through the energy that its coil internal resistance consumes low-frequency voltage, thus suppress the generation of ferro resonance phenomenon, shown in figure 11; Curve 3 is the excitation property sketch map of voltage transformer VT, and curve 4 is the excitation property sketch map of saturable reactor.The parameter designing of saturable reactor will combine excitation property, the C1 of voltage transformer VT, the numerical value of C2 etc., and the method that adopts EMTP to resolve usually on the engineering verifies, 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 respectively with the secondary terminal box of voltage transformer VT in the terminal of secondary winding be connected; This kind mode is comparatively succinct, and other external equipment is not exerted an influence, and exchanges but need to carry out the GIS relevant parameter with VT manufacturer in advance.

In addition, also can be employed in the voltage transformer VT outside (as in convergence control cabinet or independent control cabinet is set) install the method for saturable reactor additional.The interior voltage transformer VT secondary circuit wiring of convergence control cabinet is shown in figure 10, and 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 (possibly 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 through the EMTP analytic method resonance can take place at the individual phase angle of cut-offfing at circuit breaker GCB, analytic modell analytical model is shown in figure 13, and 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.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) through the EMTP analytic method.

Claims (1)

1. method that suppresses ferro resonance is characterized in that: may further comprise the steps: (1), utilize the EMTP analytic method to infer scope and operating mode that the voltage transformer ferro resonance takes place: GIS bus direct-to-ground capacitance is more little, and the probability that ferro resonance takes place is big more; Wherein operating mode is the interior T district of string of 3/2 wiring or 4/3 wiring, and this moment, line-breaker was in gate-dividing state, and the bus direct-to-ground capacitance is very little, and ferro resonance can take place voltage transformer in the string; (2), confirm the excitation property and the coil internal resistance parameter of saturable reactor; Two binding posts that (3), will satisfy the saturable reactor of parameter condition are connected with the secondary winding of voltage transformer; The Determination of Parameters process of saturable reactor is in the wherein said step (2): according to the numerical value of excitation property, breaker port electric capacity and the bus direct-to-ground capacitance of voltage transformer; Adopt excitation property that the checking of EMTP analytic method makes the saturable reactor and coil internal resistance to satisfy when low-frequency voltage prior to saturated before the voltage transformer, and the energy through coil internal resistance consumption low-frequency voltage.

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