CN109888732A - A kind of generator stator ground load inverse time-lag protection method based on earth-fault current - Google Patents
A kind of generator stator ground load inverse time-lag protection method based on earth-fault current Download PDFInfo
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- CN109888732A CN109888732A CN201810019927.8A CN201810019927A CN109888732A CN 109888732 A CN109888732 A CN 109888732A CN 201810019927 A CN201810019927 A CN 201810019927A CN 109888732 A CN109888732 A CN 109888732A
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Abstract
The invention discloses a kind of generator stator ground load inverse time-lag protection method based on earth-fault current, comprising the following steps: inject low frequency signal from generator terminal voltage mutual inductor, measure return signal, calculate generator direct-to-ground capacitance value；Generator unit stator generator terminal zero-sequence fundamental voltage is measured, calculates the fault current size of grounding point in real time；Using inverse time-lag protection algorithm, determine that the tripping of stator ground fault protection is delayed by earth-fault current size.Solve the problems, such as that the unnecessary machine of cutting of stator ground fault protection causes generator ability and benefit to be unable to give full play.
Description
Technical field
The present invention relates to field of relay protection in power, more particularly, to a kind of hair based on earth-fault current
Motor stator is grounded load inverse time-lag protection method.
Background technique
The single-phase earthing of stator winding is generator one of the most common type failure, accounts for 60% or more generator failure.With
Generator single-machine capacity constantly increases, and earth-fault current also increases with it, and seriously jeopardizes the safety of stator core.Large size power generation
Machine involves great expense, overhauls difficulty, so stator ground fault protection trips in time, prevents when earth-fault current is greater than safety value
Fault current burns iron core, has a very important significance.Meanwhile large sized unit is the main power source support of electric system,
It, which trips, forms greater impact to power network safety operation, therefore on the basis of ensureing engine health, Ying Jinliang is avoided
Unnecessary tripping gives full play to the technology and economic benefit of large sized unit.
Reasonable stator ground fault protection scheme should carry out adaptive according to fault severity level namely earth-fault current size
Judgement should be protected.The safety that could both ensure generator in this way in turn avoids the impact that large-scale generator trips to power grid security.
Currently, generator stator ground protection mainly has zero-sequence fundamental voltage type, third harmonic voltage type and 3 kinds of injecting external voltage, but
It is not to carry out protection judgement according to earth current size, cannot be adaptively acted according to fault severity level.For example, outer power-up
According to stator winding, resistance sizes carry out protection judgement to the protection of source formula over the ground, when nearby ground fault occurs for neutral point, even if
Transition resistance very little earth-fault current will not be very big, may be in generator allowed band, but injecting external voltage protection can
Can because detect it is smaller to ground resistance due to trip, cause unnecessary shutdown.
Summary of the invention
Present invention aim to address drawbacks described above, propose that a kind of generator stator ground based on earth-fault current is anti-
Time limit guard method.
To realize the above goal of the invention, the technical solution adopted is that:
A kind of generator stator ground load inverse time-lag protection method based on earth-fault current, comprising the following steps:
S1: low frequency signal is injected from generator terminal voltage mutual inductor open-delta winding, measurement return signal calculates
Generator direct-to-ground capacitance value C；
S2: generator zero-sequence fundamental voltage is measured by machine potential transformerAccording to zero-sequence fundamental voltage, generator
Direct-to-ground capacitance value, neutral earthing devices parameter calculate grounding point fault current size If；
S3: judge IfWhether protection starts definite value, if protection starting, enters step S4；Otherwise return step S1；
S4: judge IfWhether be greater than generator allow by earth-fault current, if then entering step S5；Otherwise it protects
Protection unit issues alarm signal, return step S1；
S5: the inverse-time curve of earth-fault current is born according to generator, according to IfIt determines protection act delay t, prolongs
When meet after trip protection.
The step S1 the following steps are included:
S1.1: the low-frequency current signal for being ω from generator terminal voltage mutual inductor open-delta winding injected frequency
S1.2: measurement voltage transformer open-delta side low-frequency voltageWith secondary star-like side low-frequency voltage
S1.3: according to the current signal of injection and the voltage signal measured, generator can be calculated over the ground using following formula
Capacitance current value C, different grounding modes select corresponding calculation formula:
Isolated neutral or through high resistance ground,
Neutral by arc extinction coil grounding,
In above formula, Im expression takes imaginary part operation, k1For voltage transformer primary side and open-delta side no-load voltage ratio, k2
For voltage transformer primary side and secondary star side no-load voltage ratio, LnFor arc suppression coil inductance value.
The step S2 the following steps are included:
S2.1: generator terminal power frequency phase voltage is measured using voltage transformer star side, zero-sequence fundamental voltage is calculated
Or it is directly measured by voltage transformer open-delta winding
S2.2: according toThe generator direct-to-ground capacitance value C and neutral earthing devices parameter measured in step S1, benefit
With following formula calculating ground fault size of current, different grounding modes choose corresponding formula
Isolated neutral,
Neutral by arc extinction coil grounding,
Neutral point through high resistance ground,
Compared with prior art, the beneficial effects of the present invention are:
The present invention using injection low frequency signal method real-time measurement generator direct-to-ground capacitance size, generator unit stator around
The factors such as group deformation, external equipment variation cause direct-to-ground capacitance value still can accurately obtain capacitance when changing, and disappear in this method
Influence in addition to voltage transformer internal impedance to measurement result further improves the measurement accuracy of direct-to-ground capacitance, for accurate meter
Earth-fault current size is calculated to lay a good foundation.The meter of corresponding earth-fault current is provided for different grounding modes
Formula is calculated, protection is acted according to the anti-time limit characteristic that generator bears earth-fault current, has on the one hand ensured the peace of generator
Entirely；On the other hand, generator has been given full play to the ability to bear of earth-fault current, avoids unnecessary tripping grinder pair
The impact of power network safety operation.
Detailed description of the invention
Fig. 1 is flow chart of the invention；
Fig. 2 is wiring diagram of the invention；
Fig. 3 is generator direct-to-ground capacitance measurement method schematic diagram in the present invention；
Fig. 4 is earth-fault current calculation method schematic diagram in the present invention；
Fig. 5 is that the present invention is based on the performance charts of the generator stator ground inverse time-lag protection of earth-fault current.
Specific embodiment
The attached figures are only used for illustrative purposes and cannot be understood as limitating the patent；
Below in conjunction with drawings and examples, the present invention is further elaborated.
Embodiment 1
A kind of generator stator ground load inverse time-lag protection method based on earth-fault current, referring to FIG. 1, including following
Step:
S1: low frequency signal is injected from generator terminal voltage mutual inductor open-delta winding, measurement return signal calculates
Generator direct-to-ground capacitance value C；
S2: generator zero-sequence fundamental voltage is measured by machine potential transformerAccording to zero-sequence fundamental voltage, generator
Direct-to-ground capacitance value, neutral earthing devices parameter calculate grounding point fault current size If；
S3: judge IfWhether protection starts definite value, if protection starting, enters step S4；Otherwise return step S1；
S4: judge IfWhether be greater than generator allow by earth-fault current, if then entering step S5；Otherwise it protects
Protection unit issues alarm signal, return step S1；
S5: the inverse-time curve of earth-fault current is born according to generator, according to IfIt determines protection act delay t, prolongs
When meet after trip protection.
The step S1 the following steps are included:
S1.1: the low-frequency current signal for being ω from generator terminal voltage mutual inductor open-delta winding injected frequency
S1.2: measurement voltage transformer open-delta side low-frequency voltageWith secondary star-like side low-frequency voltage
S1.3: according to the current signal of injection and the voltage signal measured, generator can be calculated over the ground using following formula
Capacitance current value C, different grounding modes select corresponding calculation formula:
Isolated neutral or through high resistance ground,
Neutral by arc extinction coil grounding,
In above formula, Im expression takes imaginary part operation, k1For voltage transformer primary side and open-delta side no-load voltage ratio, k2
For voltage transformer primary side and secondary star side no-load voltage ratio, LnFor arc suppression coil inductance value.
The step S2 the following steps are included:
S2.1: generator terminal power frequency phase voltage is measured using voltage transformer star side, zero-sequence fundamental voltage is calculated
Or it is directly measured by voltage transformer open-delta winding
S2.2: according toThe generator direct-to-ground capacitance value C and neutral earthing devices parameter measured in step S1, benefit
With following formula calculating ground fault size of current, different grounding modes choose corresponding formula
Isolated neutral,
Neutral by arc extinction coil grounding,
Neutral point through high resistance ground,
Referring to fig. 2, Fig. 2 is to implement wiring diagram of the invention.Generator terminal voltage mutual inductor is by primary side winding 3 and secondary side
Winding 1,2 forms.Vice-side winding 1 is the open-delta mode of connection, i.e. three-phase windings initial and end connects, two terminals of opening
Two supply-injected current signals of low frequency are connected to send out on terminal；In a supply-injected both ends divider resistance in parallel, voltage letter
Number access protective device；Winding 1 and it is supply-injected between install a current transformer, current signal access protective device；Secondary side
Winding 2 is star-like connection winding, and wherein the two ends of a phase winding are respectively connected to two voltage signal inputs of protective device
Son；Primary side winding 3 is star-like connection winding.In actual work, supply-injected to inject low-frequency current signal from vice-side winding 1, it protects
Protection unit measures the voltage signal of the voltage and current signals of vice-side winding 1, vice-side winding 2.
Generator direct-to-ground capacitance measurement method principle is as shown in Figure 3.Z1、Z2、Z3The respectively leakage impedance of winding 1,2,3,
For the value for converting primary side.k1For voltage transformer primary side and open-delta side no-load voltage ratio, k2It is primary for voltage transformer
Side and secondary star side no-load voltage ratio.Protective device extracts the low-frequency voltage of secondary winding 1 by filtering algorithm and Fourier algorithmAnd low-frequency currentAnd a phase winding low-frequency voltage in secondary winding 2According to Fig. 3 and Circuit theory, can derive
The calculation formula of generator direct-to-ground capacitance value under three kinds of neutral grounding modes.
Isolated neutral,
For transformer, each side winding leakage impedance conversion to approximately equal, i.e. Z behind the same side1=Z3, in conjunction with above-mentioned two formula,
It can be derived by
Neutral by arc extinction coil grounding,
LnFor arc suppression coil inductance value.In view of Z1=Z3, in conjunction with above-mentioned two formula, can be derived by
Neutral point through high resistance ground,
RnFor neutral resistance value.In view of Z1=Z3, in conjunction with above-mentioned two formula, can be derived by
Generator stator ground failure zero sequence equivalent circuit is as shown in Figure 4.According to Circuit theory, three kinds of neutral points can be derived
The calculating formula of earth-fault current under earthing mode.
Isolated neutral,
Neutral by arc extinction coil grounding,
Neutral point through high resistance ground,
The acting characteristic of generator stator ground inverse time-lag protection based on earth-fault current is as shown in Figure 5.Curve 1 is
Inverse time lag tripping section characteristic, curve 2 are specified time alarm section characteristic.If·stTo protect initiation value, If·downEvent is grounded for generator
Hinder electric current permissible value, If·upFor the corresponding earth-fault current value of inverse time lag upper limit time, tdn is specified time alarm section delay,
Tup is section upper limit delay of tripping the inverse time lag, need to be with the quick protection cooperation of generator.
Obviously, the above embodiment of the present invention be only to clearly illustrate example of the present invention, and not be pair
The restriction of embodiments of the present invention.For those of ordinary skill in the art, may be used also on the basis of the above description
To make other variations or changes in different ways.There is no necessity and possibility to exhaust all the enbodiments.It is all this
Made any modifications, equivalent replacements, and improvements etc., should be included in the claims in the present invention within the spirit and principle of invention
Protection scope within.
Claims (3)
1. a kind of generator stator ground load inverse time-lag protection method based on earth-fault current, which is characterized in that including following
Step:
S1: low frequency signal is injected from generator terminal voltage mutual inductor open-delta winding, measurement return signal calculates power generation
Machine direct-to-ground capacitance value C；
S2: generator zero-sequence fundamental voltage is measured by machine potential transformerOver the ground according to zero-sequence fundamental voltage, generator
Capacitance, neutral earthing devices parameter calculate grounding point fault current size If；
S3: judge IfWhether protection starts definite value, if protection starting, enters step S4；Otherwise return step S1；
S4: judge IfWhether be greater than generator allow by earth-fault current, if then entering step S5；Otherwise protection dress
Set sending alarm signal, return step S1；
S5: the inverse-time curve of earth-fault current is born according to generator, according to IfDetermine protection act delay t, delay meets
Trip protection afterwards.
2. a kind of generator stator ground load inverse time-lag protection method based on earth-fault current according to claim 1,
It is characterized in that, step S1 the following steps are included:
S1.1: the low-frequency current signal for being ω from generator terminal voltage mutual inductor open-delta winding injected frequency
S1.2: measurement voltage transformer open-delta side low-frequency voltageWith secondary star-like side low-frequency voltage
S1.3: according to the current signal of injection and the voltage signal measured, generator direct-to-ground capacitance can be calculated using following formula
Current value C, different grounding modes select corresponding calculation formula:
Isolated neutral or through high resistance ground,
Neutral by arc extinction coil grounding,
In above formula, Im expression takes imaginary part operation, k1For voltage transformer primary side and open-delta side no-load voltage ratio, k2For electricity
Press mutual inductor primary side and secondary star side no-load voltage ratio, LnFor arc suppression coil inductance value.
3. a kind of generator stator ground load inverse time-lag protection method based on earth-fault current according to claim 1,
It is characterized in that, the step S2 the following steps are included:
S2.1: generator terminal power frequency phase voltage is measured using voltage transformer star side, zero-sequence fundamental voltage is calculatedOr directly
It is measured by voltage transformer open-delta winding
S2.2: according toThe generator direct-to-ground capacitance value C and neutral earthing devices parameter measured in step S1, under utilization
Formula calculating ground fault size of current is stated, different grounding modes choose corresponding formula
Isolated neutral,
Neutral by arc extinction coil grounding,
Neutral point through high resistance ground,
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| CN201810019927.8A CN109888732A (en) | 2018-01-09 | 2018-01-09 | A kind of generator stator ground load inverse time-lag protection method based on earth-fault current |
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| CN201810019927.8A CN109888732A (en) | 2018-01-09 | 2018-01-09 | A kind of generator stator ground load inverse time-lag protection method based on earth-fault current |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112234578A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Stator grounding protection method and system by connecting resistors in series from arc suppression coil |
| CN113203950A (en) * | 2021-04-30 | 2021-08-03 | 华中科技大学 | Method and system for diagnosing ground fault degree of generator stator of marine nuclear power platform |
| CN114844001A (en) * | 2022-05-27 | 2022-08-02 | 清华大学 | Optimal design method and system for combined grounding mode of generator |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112234578A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Stator grounding protection method and system by connecting resistors in series from arc suppression coil |
| CN112234578B (en) * | 2020-10-28 | 2022-06-28 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Stator grounding protection method and system by injecting resistance from series connection of arc suppression coils |
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| CN114844001A (en) * | 2022-05-27 | 2022-08-02 | 清华大学 | Optimal design method and system for combined grounding mode of generator |
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Application publication date: 20190614 |