CN100399663C - Negative sequence direction inter-turn protection with fault component start-up and steady state component preservation - Google Patents

Abstract

The present invention relates to a relay protection method in the electric power system field, which discloses a method for discriminating turn-to-turn short circuits of a generator by identifying the neutral point electric current and the end voltage of the generator. The method comprises the following steps: a protection device of the generator samples the waveforms of an electric current and a voltage of a mutual inductor to obtain the instantaneous values of the electric current and the voltage; a complex form of each electric quantity is calculated by the Fu's algorithm; the negative sequence components of the neutral point electric current and the end voltage are filtered by a filtration algorithm; the variation (a fault component) is figured out by the mnemonic negative sequence electric current and the negative sequence voltage; a negative sequence direction element of the fault component is used as a turn-to-turn protection starting element; after the negative sequence direction element of the fault component is started 20 ms, the negative sequence direction element of the fault component is converted to a steady state component negative sequence direction element. If steady state component conditions are satisfied, the protection is output via a certain delay. The method has accurate recognition to turn-to-turn faults, enhances sensibility and ensures safe and reliable running of the protection.

Description

The negative sequence direction inter-turn protection method that the fault component start-up and steady state component amount keeps

Technical field

The present invention relates to field of power, relate more specifically to the method for relaying protection.

Background technology

The large synchronous generator group is the basic equipment of electrical energy production, occupies important status in electric power system.The generator single-machine capacity continues to increase in recent years, and their costs are very expensive, and structure is more complicated, is damaged in case hinder for some reason, and the maintenance difficulty is big, the time is long, and the direct and consequential damage that national economy is caused is very huge.So just selectivity, rapidity, reliability, the sensitivity of generator protection device are had higher requirement.

No matter be large turbo-type generator or large-sized water turbine generator, its stator winding is all bigger with the ratio that layer line rod about the groove belongs to homophase.Because leaking of stator internal water cooling coil; stator winding end laying dust, long-pending oil are many; add year in year out vibrations of generating set, generate heat and be subjected to the effect of powerful electromagnetic force; in stator slot or the end may cause shorted-turn fault; the operation statistics also shows the example that truly has turn-to-turn short circuit; also once took place to cause the serious accident that generator seriously burns out, so should install the protection of high-rating generator stator winding inter-turn short circuit because of being unkitted the sub-winding inter-turn protection of setting.

Can draw the generator of 4～6 terminals for neutral point, can install unit piece horizontal poor, split mutually horizontal difference or not exclusively main protections such as vertical difference protect stator winding inter-turn short circuit failure.But in the reality, there are a lot of generator neutral points to have only 3 exits both at home and abroad.This moment, interturn protection comparatively commonly used was to adopt the longitudinal zero-sequence over-voltage principle.There not being special-purpose longitudinal zero-sequence over-voltage instrument transformer can not install the occasion of longitudinal zero-sequence over-voltage protection, generally can only install the interturn protection of fault component negative sequence direction or not install interturn protection.

On-the-spot ruuning situation shows, fault component negative-sequence directional protection in the transient process of external area error, outer near terminal fault particularly in the district, the route protection tripping operation coincides with the phenomenon that malfunction is arranged in the process of permanent fault, jumping repeatedly.The present invention is directed to the problem that present fault component negative-sequence directional protection exists, propose the negative sequence direction interturn protection that a kind of fault component starts, steady-state quantity keeps.

Summary of the invention

For neutral point only to draw 3 terminals and not have the generator of special-purpose turn-to-turn voltage transformer; for protecting the stator winding turn-to-turn fault reliably; the invention provides a kind of passing through and differentiate generator neutral point electric current and set end voltage, differentiate the method for generator shorted-turn fault.This method comprises the steps: that protection equipment for generator is sampled to the current-voltage waveform of instrument transformer and obtains the current/voltage instantaneous value; Obtain the plural form of each electric parameters by fourier algorithm; Leach the negative sequence component of electric current and voltage by strain sequence arithmetic; Negative-sequence current and negative sequence voltage by memory are calculated its variable quantity (being fault component); Drop into the fault component negative-sequence direction component as the interturn protection starting component; Switch to the negative-sequence direction component of steady-state quantity behind the startup 20ms, export through certain time-delay if the steady-state quantity condition satisfies protection.This method is more accurate to the identification of turn-to-turn fault, can guarantee the safe and reliable operation protected to have solved the technical barrier of fault component negative-sequence directional protection incorrect operation for a long time preferably when improving sensitivity.

Description of drawings

Fig. 1 has shown the installation site of current transformer and voltage transformer and the definition of polarity;

The negative sequence direction interturn protection logic diagram that Fig. 2 keeps for the fault component start-up and steady state component amount.

Specific embodiments

The installation site of current transformer (being called for short TA, as follows) and voltage transformer (being called for short TV, as follows) and the definition of polarity please refer to Fig. 1, and GS is a generator among the figure, and MT is a main transformer, and TV1 is machine end general T V, and TA1 is machine end TA, and TA2 is neutral point TA.The logic diagram of the negative sequence direction interturn protection principle that fault component start-up and steady state component amount of the present invention keeps please refer to Fig. 2.

At first obtain the plural form of each electric parameters, can leach the negative sequence component I of neutral point current and set end voltage then by the strain sequence arithmetic shown in the following formula by fourier algorithm ₂And U ₂:

I _2·Re＝I _a·Re-0.5(I _b·Re+I _c·Re)+0.866(I _b·Im-I _c·Im)

(1)

I2 _Im＝I _a.Im-0.5(I _b.Im+I _c.Im)-0.866(I _b.Re-I _c.Re)

In the formula: I _2Re, I _2ImBe respectively the real part and the imaginary part of negative-sequence current, I _ARe, I _AIm, I _BRe, I _BIm, I _CRe, I _CImBe respectively A, B, the real part of C phase current and imaginary part.Negative sequence voltage can obtain by similar method.

Negative-sequence current and negative sequence voltage by memory can be calculated its variable quantity, i.e. fault component Δ I ₂With Δ U ₂

According to the protection logic diagram that Fig. 2 shows, the fault component Δ I of negative-sequence current is adopted in protection ₂Fault component Δ U with negative sequence voltage ₂The fault component Δ P of the negative sequence power that calculates ₂As starting component, fault component starting component operating criterion is:

(ΔI ₂＞I _2QT)∩(ΔU ₂＞U _2QT)∩(ΔP ₂＞P _ΔT) (2)

In the formula: I _2QT, U _2QT, P _{Δ T}Be respectively the threshold value of negative-sequence current, negative sequence voltage, negative sequence power fault component.

The fault component of negative sequence power can be calculated as follows:

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C20051000213500072.png"\; state="\{\{state\}\}">P</figure-callout>}}_2=3\mathrm{Re}(\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{U}}_2\&CenterDot;\mathrm{\&Delta;}\widehat{\stackrel{\&CenterDot;}{I}}{e}^{-\mathrm{j\&phi;}})---\left(3\right)$

In the formula: φ is the maximum sensitive angle of fault component negative sequence direction relay, is generally 75 °～85 °.

The fault component negative-sequence direction component starts back 20ms and withdraws from the fault component negative-sequence direction component, and the negative-sequence direction component that drops into steady-state quantity simultaneously is as the time-delay discriminating element, and steady-state quantity negative-sequence direction component operating criterion is:

(I ₂＞I _2Q)∩(U ₂＞U _2Q)∩(P ₂＞0) (4)

In the formula: I _2Q, U _2QBe respectively negative-sequence current, negative sequence voltage threshold value, the device internal fixation; P ₂Be negative-sequence direction component.

The maximum sensitive angle of steady-state quantity negative sequence direction relay is generally 75 °～85 °.The voltage of negative sequence direction relay is taken from machine end TV, and electric current is taken from neutral point TA.

Protection logic diagram according to Fig. 2 shows does not all take place under the unusual situation at TA and TV, if having negative-sequence current and negative sequence voltage, and the negative sequence direction of steady-state quantity satisfies, and protection is through 200ms time-delay outlet.

When generator inside turn-to-turn fault took place, neutral point current equated fully that with machine end electric current the source of trouble is in generator inside, and negative sequence power flows to system by generator, and fault component and steady-state quantity negative-sequence direction component all can move.When generator inside phase fault takes place when; because that get is the TA at neutral point place, approximate anti-phase with machine end electric current, fault component and steady-state quantity negative-sequence direction component all are failure to actuate; should protect phase-to phase fault this moment by protections such as vertical differences, and fault has more selectivity between the interturn protection non-reaction phase.When external area error took place, the source of trouble was in the generator outside, negative sequence power all by system flow to generator, fault component and steady-state quantity negative-sequence direction component all are failure to actuate.When unbalanced fault excises outside the district, Δ I ₂With Δ U ₂Direction is opposite when all taking place with corresponding outer symmetrical fault, thus the fault component negative-sequence direction component can not move yet, and steady-state quantity non-negative sequence current and negative sequence voltage, the steady-state quantity negative-sequence direction component can not move yet, and can finally make protection reliably motionless.When the secondary circuit broken string took place TA, because no negative sequence voltage, fault component and steady-state quantity negative-sequence direction component all were failure to actuate; When the secondary circuit broken string should TV takes place, because non-negative sequence current, fault component and steady-state quantity negative-sequence direction component also all were failure to actuate.But if the secondary circuit broken string all takes place for TA and TV, or external area error takes place during some broken strings again, then may cause the malfunction of this protection, therefore when protecting when declaring to have taken place TA or TV and breaking, with this protection of locking.After playing machine before the generator connecting in parallel with system and adding excitation, if inner turn-to-turn fault takes place, because each phase current is all 0, negative-sequence direction component can not move, therefore, and the turn-to-turn fault when this criterion is not reacted zero load.

In fact; in the external area error transient process of complexity; for example when the outer near terminal fault in district; the route protection tripping operation coincides with permanent fault, when jumping repeatedly; because the transient process of primary system; the transient characterisitics of secondary circuit have nothing in common with each other, and add the error of measurement, adopt simple fault component negative-sequence direction component that the phenomenon of malfunction once took place.But the steady-state quantity negative-sequence direction component can be avoided the transient process of system, extracts the stable state fault signature, in the time of can guaranteeing external area error, and the not malfunction of steady-state quantity negative-sequence direction component.

In sum, the sensitivity that the present invention measures sudden change element combines with the reliability of steady-state quantity element, and is more accurate to the identification of turn-to-turn fault, can guarantee the safe and reliable operation of protecting when improving sensitivity.

Claims (1)

1. one kind is passed through to differentiate generator neutral point electric current and set end voltage, differentiates the method for generator turn-to-turn short circuit, and this method comprises the steps:

Protection equipment for generator obtains the current/voltage instantaneous value to the current-voltage waveform sampling of instrument transformer;

Obtain the plural form of each electric parameters by fourier algorithm;

Leach the negative sequence component of electric current and voltage by strain sequence arithmetic;

Negative-sequence current and negative sequence voltage by memory are calculated its variable quantity, i.e. fault component;

Drop into the fault component negative-sequence direction component as the interturn protection starting component;

Wherein following formula is as the operating criterion of failure judgement component starting component: (Δ I ₂＞I _2QT) ∩ (Δ U ₂＞U _2QT) ∩ (Δ P ₂＞P _{Δ T})

In the formula: Δ I ₂, Δ U ₂, Δ P ₂Be respectively negative-sequence current fault component, negative sequence voltage fault component, negative sequence power fault component, I _2QT, U _2QT, P _{Δ T}Be respectively negative-sequence current, negative sequence voltage, negative sequence power fault component threshold value,

Switch to the negative-sequence direction component of steady-state quantity behind the startup 20ms, if the steady-state quantity condition satisfies protection through the certain time-delay outlet,

Wherein following formula is as the operating criterion of judging the steady-state quantity negative-sequence direction component:

(I ₂＞I _2Q)∩(U ₂＞U _2Q)∩(P ₂＞0)

In the formula: I ₂Be neutral point side negative-sequence current, U ₂Be the distolateral negative sequence voltage of machine; I _2Q, U _2QBe respectively negative-sequence current, voltage threshold value, P ₂Be negative-sequence direction component.

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