CN105071347B - Prevent transfer overvoltage from causing the blocking method of generator stator ground false protection - Google Patents
Prevent transfer overvoltage from causing the blocking method of generator stator ground false protection Download PDFInfo
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- CN105071347B CN105071347B CN201510421004.1A CN201510421004A CN105071347B CN 105071347 B CN105071347 B CN 105071347B CN 201510421004 A CN201510421004 A CN 201510421004A CN 105071347 B CN105071347 B CN 105071347B
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Abstract
The invention discloses a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection; for through grounding through arc unit; two criterions of involution are delayed to carry out transfer overvoltage identification and locking after being disappeared by the difference and system side residual voltage 3U0 of residual voltage frequency and system work frequency; within setting delay after system earth failure removal and during residual voltage frequency significant difference 50Hz; locking stator ground fault protection, otherwise open stator ground fault protection.This method only relies on raising protection definite value relative to current generator protection device prevents the method for malfunction from comparing; this method is after system failure excision; stator ground fault protection malfunction can be effectively prevented in transfer overvoltage freedom of entry oscillatory process; protection definite value with the amplitude of transfer overvoltage and time without being coordinated; it ensure that the rapidity and sensitivity of stator ground fault protection action; reduce unit to shut down caused by false protection, can effectively prevent the loss to the economic benefit and social benefit of power plant.
Description
Technical field
The present invention relates to a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection.
Background technology
The quick acting of stator ground fault protection reduces generator damaged condition, risen to containment generator electric fault development
Important effect.With stator ground fault protection adaptive setting specification and relay protective scheme it is perfect, drawn by main transformer transfer overvoltage
The zero-sequence fundamental voltage stator ground fault protection malfunction rate risen has decreased, but in malfunction, passed through as caused by transfer overvoltage
The false protection of grounding through arc unit accounts for significant proportion.At present, in the G-T protective device of each main flow manufacturer production, though
Transfer overvoltage latching logic is employed in right stator ground fault protection, but according to field statistics, does not effectively eliminate transmission
Influence of the voltage to stator ground fault protection, false protection rate is higher, or even has the danger for causing more units while tripping operation, seriously
Threaten the safe operation of power network.
Therefore, how simply, effectively eliminate influence of the transfer overvoltage to stator ground fault protection be puzzlement technical staff
A great problem.
When generator boosting becomes high-pressure side generation ground short circuit, residual voltage is by by between transformer high and low pressure winding
The electric capacity that is coupled is delivered to generator side, and transfer overvoltage computation model is as shown in Figure 1.
Wherein, E0 is residual voltage caused by high voltage side of transformer earth fault；C1Based on uprise between low pressure winding etc.
Imitate coupled capacitor, the factors such as capacitance and transformer capacity, high side voltage grade and transformer neutral point are grounded are relevant；C2For
Generator system one phase equivalent electric capacity over the ground, include the direct-to-ground capacitance of the electrical equipment such as generator, Transformer Winding；L1With R points
Not Wei generator neutral point arc suppression coil equivalent inductance and resistance, voltage U0 is measured at voltmeter V and transmits zero for generator end
Sequence voltage.
At present, in transformer unit stator ground fault protection, transferring over-voltage latching logic passes through detecting system side 3U0 amplitude
Size judges whether to be likely to occur transfer overvoltage, and logic chart is shown in Fig. 2, and as preventing transfer overvoltage from causing stator ground fault protection
Unique criterion of malfunction.Think that generator there may be transfer overvoltage, then protects locking stator grounding when there is earth fault
Protective function；After the system failure disappears, it is believed that transfer overvoltage disappears, then opens stator ground fault protection immediately.Therefore, to prevent from passing
Influence of the voltage to stator ground fault protection is passed, when protecting fixed value adjusting to calculate, it has to raise or extend protection by 3U0 definite values
Action delay, so it is with sacrificing protection operating sensitivity, i.e. protection domain, and protection to escape the influence of transferring over-voltage
Rapidity is acted as cost.
Acted and counted according to scene protection, for the generating set of grounding through arc, at present stator ground fault protection use
Transfer overvoltage latching logic can not effectively eliminate the influence of transfer overvoltage, can still cause stator ground fault protection malfunction to be jumped
Lock.
The content of the invention
The present invention is in order to solve the above problems, it is proposed that one kind prevents transfer overvoltage from causing grounding through arc generator to be determined
The blocking method of sub- ground protection malfunction, this method, which has, accurately identifies transfer overvoltage ability, can effectively prevent transfer overvoltage
Caused stator ground fault protection malfunction.
To achieve these goals, the present invention adopts the following technical scheme that：
A kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection, comprises the following steps：
(1) judge whether system connects by the size of the transmission residual voltage amplitude of detecting system side generator end
Earth fault；
(2) judge whether the residual voltage that generator occurs causes because of transfer overvoltage, if it is, locking stator grounding
Protection；
(3) it will judge whether transfer overvoltage enters by the frequency detecting to residual voltage after system side failure is cut off
Free oscillation process, the frequency detected deviate considerably from power frequency, then can determine whether to generate transfer overvoltage vibration, while locking is protected
Shield；Otherwise it is assumed that transfer overvoltage oscillatory extinction disappears, while open and protection；
(4) after transfer overvoltage dyingout, after unit is in normal operating condition, open stator ground fault protection；
The step (3) is after system earth failure removal, system side residual voltage source event resolves, because lc circuit is free
The characteristics of vibration, generator transfer overvoltage does not disappear with the excision of system earth failure, but freedom of entry oscillation
State simultaneously progressively decays；
In the step (3), judge whether the criterion of freedom of entry oscillatory process includes transfer overvoltage：Criterion one：System
After failure removal, the difference of residual voltage mixing frequencies and system work frequency is obvious；Criterion two：System side 3U0 loss of voltage
Afterwards, the oscillatory process of transfer overvoltage will with a time parameter dyingout, therefore system side 3U0 disappear delay involution conduct
Second criterion, transfer overvoltage identification is carried out using two criterions, continue locking stator grounding if setting up in two criterions
Protection, otherwise will open stator ground fault protection.
In the step (1), when earth fault occurs for system, the amplitude in system side residual voltage source is equal to system earth
Residual voltage during failure, now, the transfer overvoltage of generator generator terminal is unit inherent feature frequency and ground connection residual voltage frequency
The mixed waveform that rate is formed, transfer overvoltage frequency are calculated with formula (1)：
In formula：F is transfer overvoltage frequency；f1For the inherent feature frequency of lc circuit；f2For system side residual voltage 3U0 frequencies
Rate.
In the step (3), after system earth failure removal, system side residual voltage 3U0 is zero, calculates equivalent circuit and is
Arc suppression coil and the circuit connected and formed with boosting change equivalent binding capacitance again after generator over the ground equivalent capacity parallel connection, now
Circuit feature frequency be f1, by after unit breaker tripping, generator is no longer connected stator ground fault protection with system, and boosting becomes
Equivalent binding capacitance branch is in open-circuit condition and not worked, and at this moment unit parameter equivalent circuit is changed into arc suppression coil with generating electricity
Machine equivalent capacity parallel circuit over the ground, transfer overvoltage frequency now depends on arc suppression coil and generator, and equivalent capacity is simultaneously over the ground
Join the characteristic frequency in loop.
In the step (3), after system earth failure removal, system residual voltage 3U0 disappears, generator 3U0 voltages
Amplitude is still present, and is more than or equal to definite value according to generator side 3U0, stator ground fault protection works, and system side 3U0 is more than or equal to
Definite value, the inoperative protection blocking criterion of stator ground fault protection, test stator ground fault protection are in open state, work as generating
When machine 3U0 amplitude and duration are more than protection definite value, stator ground fault protection malfunction chaser.
In the step (3), the computational methods of residual voltage mixing frequencies are：
The inherent feature frequency of equivalent circuit is calculated as follows, and ignores the resistance parameter in circuit：
Wherein, Z is the equiva lent impedance of circuit；ω is angular frequency, makes molecule, denominator zero, and circuit feature frequency is：
Wherein, C1Become equivalent binding capacitance value, C for boosting2For generator equivalent capacitance value over the ground, L1For arc suppression coil electricity
Inductance value.
Beneficial effects of the present invention are：
(1) this method is directed to current existing logic and does not account for the influence of transfer overvoltage oscillatory process and cause protection to miss
The problem of dynamic, by based on transfer overvoltage characteristic frequency and free oscillation process analysis procedure analysis, being cut using transfer overvoltage in the system failure
The frequency change of free oscillation after removing and time-delay characteristics are identified, it is ensured that stator ground fault protection is in transfer overvoltage duration of existence
Latch-up protection is persistently kept, to prevent false protection；After transfer overvoltage disappearance, during unit normal operation, stator ground fault protection
Still according to the definite value running open of routine；
(2) this method can effectively identify that the transfer overvoltage through grounding through arc unit is protected to generator stator ground
The influence of shield, only relying on raising protection definite value relative to current generator protection device prevents the method for malfunction from comparing, and this method exists
After system failure excision, stator ground fault protection malfunction can be effectively prevented in transfer overvoltage freedom of entry oscillatory process, protects definite value
Without being coordinated with the amplitude of transfer overvoltage and time, it is ensured that the rapidity and sensitivity of stator ground fault protection action, subtract
Few unit is shut down caused by false protection, can effectively prevent the loss to the economic benefit and social benefit of power plant.
Brief description of the drawings
Fig. 1 is the approximate simplified electrical circuit diagram of the calculating transfer overvoltage of the present invention；
Fig. 2 is that the current of the present invention uses stator ground fault protection logical schematic；
Fig. 3 is stator ground fault protection latching logic schematic diagram of the present invention；
Fig. 4 is 300MW units fault oscillograph of the present invention；
Fig. 5 is the transfer overvoltage simulation waveform of the present invention.
Embodiment：
The invention will be further described with embodiment below in conjunction with the accompanying drawings.
A kind of method for preventing transfer overvoltage from causing generator stator ground false protection locking, detailed process are：(1) when
When earth fault occurs for system side, judge whether generator transmits by detecting system side residual voltage 3U0 size
Voltage, the latch-up protection if there is 3U0, when system side residual voltage 3U0 disappears then open and protection immediately；(2) in system earth
After failure removal, system side 3U0 disappears immediately, at this moment judges to transmit by the frequency detecting to generator generator terminal residual voltage
Whether voltage enters oscillatory process, and the frequency such as detected deviates considerably from 50Hz, then can determine whether to generate transfer overvoltage vibration, together
When latch-up protection；Otherwise it is assumed that transfer overvoltage oscillatory extinction disappears, while open and protection；Because when oscillatory process is with system one time
Between constant and decay, therefore increase the delay involution criterion after system failure excision, to increase the security of criterion, when system therefore
After barrier excision after certain time-delay then unconditional open and protection.(3) unit enters normal operation after transfer overvoltage influences to eliminate
During state, stator ground fault protection opens all the time, and now stator ground fault protection definite value with transfer overvoltage without coordinating.
In equivalent circuit shown in Fig. 1, if ignoring the resistance in circuit, generator system can be equivalent to arc suppression coil L1With
Generator equivalent capacity C over the ground2Become equivalent binding capacitance C with boosting again after parallel connection1The circuit connected and formed, such as Fig. 1 circuits a-
Shown in the left-hand component of b ports.When earth fault occurs for system, as terminated in circuit a-b into alternating-current voltage source E0, voltage source
Residual voltage of amplitude when being equal to system earth failure, its frequency is 50H.Now, the transfer overvoltage of generator generator terminal is machine
Group inherent feature frequency (Fig. 1 a-b ends left-hand component circuit) and ground connection residual voltage frequency (Fig. 1 a-b ends right part parallel circuit) shape
Into mixed waveform, transfer overvoltage frequency can use formula (1) calculate.
In formula：F is transfer overvoltage frequency；F1 is Fig. 1 a, the inherent feature frequency of b ends left part parallel circuit；F2 is system side
Residual voltage E0 frequencies.
After system failure excision, E0 shown in Fig. 1 is zero, and calculating equivalent circuit is arc suppression coil L1It is equivalent over the ground with generator
Electric capacity C2Become equivalent binding capacitance C with boosting again after parallel connection1The circuit connected and formed, such as Fig. 1 circuit a-b ports left-hand component
Shown, circuit feature frequency now is f1.
By after unit breaker tripping, generator is no longer connected stator ground fault protection with system, and boosting becomes equivalent coupled electricity
Hold C1Branch is in open-circuit condition and not worked, and at this moment unit parameter equivalent circuit is changed into arc suppression coil L1With generator over the ground
Equivalent capacity C2Parallel circuit, on the left of Fig. 1 c-b ports shown in circuit.Transfer overvoltage frequency now depends primarily on L1With C2
The characteristic frequency of shunt circuit.
As shown in Figure 1, after system earth failure removal, E0 voltage source event resolves, because of the spy of lc circuit free oscillation
Point, generator transfer overvoltage disappears with the excision of system earth failure, but freedom of entry oscillatory regime and progressively
Decay.Current stator ground fault protection latching logic, because not accounting for transfer overvoltage free oscillation, the characteristic for the decay that is delayed, institute
Can not effectively prevent the malfunction of stator ground fault protection.After system earth failure removal, system residual voltage 3U0 disappears,
Generator residual voltage 3U0 voltage magnitudes are still present, and according to current protection blocking criterion, test stator ground fault protection has been located
In open state, when 3U0 amplitude and duration are more than protection definite value, stator ground fault protection malfunction chaser.
The inventive method is directed to current existing logic and does not account for the influence of transfer overvoltage oscillatory process and cause to protect
The problem of malfunction, by based on transfer overvoltage characteristic frequency and free oscillation process analysis procedure analysis, using transfer overvoltage in the system failure
The frequency change of free oscillation after excision and time-delay characteristics are identified, it is ensured that stator ground fault protection has the phase in transfer overvoltage
Between persistently keep latch-up protection, to prevent false protection；After transfer overvoltage disappearance, during unit normal operation, stator grounding is protected
Protect the definite value running open still according to routine.On the premise of this method may be implemented in no sacrificing protection sensitivity and rapidity
Eliminate the influence of transfer overvoltage.
Example one：The differentiation of process in detail so that certain is through grounding through arc 300WM unit malfunction events as an example
Journey, Fig. 3 are the logical schematic of inventive method.
When earth fault occurs for system, the residual voltage 3U0 of system side will be greater than definite value, at this moment because of the original of transfer overvoltage
Because residual voltage, i.e. transfer overvoltage will be produced in generator, now by stator ground fault protection locking.
After system earth failure is removed, freedom of entry is vibrated according to the residual voltage of theory analysis generator generator terminal
Process, its frequency are the characteristic frequency of generator system and the mixing of system earth failure residual voltage source frequency (50Hz), are had
There are significantly different and power-frequency voltage 50Hz frequency features, generator residual voltage will be with primary system caused by transfer overvoltage in addition
The size of time constant and decay, therefore oscillatory process is entered according to above transfer overvoltage free oscillation process electric measure feature
Row identification.Criterion one：After system failure excision, residual voltage mixing frequencies are 46.64Hz and system work frequency in this example
50Hz difference is obvious；Criterion two：After system side residual voltage 3U0 disappears, the oscillatory process of transfer overvoltage will be with a time
Parameter and dyingout, therefore system side residual voltage 3U0 disappears delay involution as second criterion, using two criterions come
Transfer overvoltage identification is carried out, continues locking stator ground fault protection if setting up in two criterions, otherwise protects open stator grounding
Shield, prevents from protecting excessive locking and influenceing engine health.
When system side 3U0 is zero in unit running process, transfer overvoltage locking criterion is not worked, and stator ground fault protection is held
Continuous to open, when generator earth fault occurs, protection can act tripping operation according to 3U0 definite values and delay t1, prevent generator
Failure propagation.
Characteristic frequency calculating process：
Fig. 4 is certain stator ground fault protection malfunction recording through grounding through arc unit.
Parameter measurement method calculates and simulating, verifying：
Essential electrical surveys parameter:Generator neutral point arc suppression coil inductance L116.31H；Generator system is single-phase right
Ground electric capacity C20.232uF, boosting become (242/20kV, 360MVA) high-low pressure winding one phase equivalent coupled capacitor C10.008uF is high
Press side isolated neutral.
The inherent feature frequency of equivalent circuit shown in Fig. 1 is calculated as follows, and is calculated to simplify, and ignores the resistance ginseng in circuit
Number：
Wherein, Z is the equiva lent impedance of circuit；ω is angular frequency.Molecule, denominator zero are made, circuit feature frequency is：
Bring parameter into formula (3), counting circuit characteristic frequency is 46.46Hz, calculates frequency and is cut off with Fig. 4 system failures
Transfer overvoltage frequency 46.59 is basically identical afterwards.
Digital Simulation is carried out to system earth failure occurs through grounding through arc unit using PSCAD softwares, Fig. 5 is to be
The simulation waveform of system side residual voltage and generator transferring over-voltage.As shown in figure 5, transfer overvoltage frequency after system failure excision
For 46.49, with failure wave-recording frequency shown in Fig. 4 and to calculate frequency basically identical, hence it is evident that be different from work frequency 50Hz.
Although above-mentioned the embodiment of the present invention is described with reference to accompanying drawing, model not is protected to the present invention
The limitation enclosed, one of ordinary skill in the art should be understood that on the basis of technical scheme those skilled in the art are not
Need to pay various modifications or deformation that creative work can make still within protection scope of the present invention.
Claims (4)
1. a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection, it is characterized in that：Including following
Step：
(1) judge whether system occurs ground connection event by the size of the transmission residual voltage amplitude of detecting system side generator end
Barrier；
(2) judge whether the residual voltage that generator occurs causes because of transfer overvoltage, if it is, locking stator grounding is protected
Shield；
(3) after system side failure is cut off by by the frequency detecting to residual voltage come judge transfer overvoltage whether freedom of entry
Oscillatory process, the frequency detected deviate considerably from power frequency, then can determine whether to generate transfer overvoltage vibration, while latch-up protection；It is no
Then think that transfer overvoltage oscillatory extinction disappears, while open and protection；
(4) after transfer overvoltage dyingout, after unit is in normal operating condition, open stator ground fault protection；
In the step (1), when earth fault occurs for system, the amplitude in system side residual voltage source is equal to system earth failure
When residual voltage, now, the transfer overvoltage of generator generator terminal is unit inherent feature frequency and ground connection residual voltage frequency shape
Into mixed waveform, transfer overvoltage frequency with formula (1) calculate：
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In formula：F is transfer overvoltage frequency；f1For the inherent feature frequency of lc circuit；f2For system side residual voltage 3U0 frequencies；
The step (3) is after system earth failure removal, system side residual voltage source event resolves, because of lc circuit free oscillation
The characteristics of, generator transfer overvoltage does not disappear with the excision of system earth failure, but freedom of entry oscillatory regime is simultaneously
Progressively decay；
In the step (3), judge whether the criterion of freedom of entry oscillatory process includes transfer overvoltage：Criterion one：The system failure
After excision, the difference of residual voltage mixing frequencies and system work frequency is obvious；Criterion two：After system side 3U0 loss of voltage, pass
Pass voltage oscillatory process will with a time parameter dyingout, therefore system side 3U0 disappear delay involution as second
Individual criterion, transfer overvoltage identification is carried out using two criterions, continues locking stator ground fault protection if setting up in two criterions,
Otherwise will open stator ground fault protection.
2. a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection as claimed in claim 1,
It is characterized in that：In the step (3), after system earth failure removal, system side residual voltage 3U0 is zero, calculates equivalent circuit
For arc suppression coil and become equivalent binding capacitance with boosting again after generator over the ground equivalent capacity parallel connection to connect the circuit to be formed, this
When circuit feature frequency be f1, by after unit breaker tripping, generator is no longer connected stator ground fault protection with system, boosting
Become equivalent binding capacitance branch to be in open-circuit condition and do not work, at this moment unit parameter equivalent circuit is changed into arc suppression coil and hair
Equivalent capacity parallel circuit, transfer overvoltage frequency now depend on arc suppression coil and generator equivalent capacity over the ground to motor over the ground
The characteristic frequency of shunt circuit.
3. a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection as claimed in claim 1,
It is characterized in that：In the step (3), after system earth failure removal, system residual voltage 3U0 disappears, generator 3U0 voltages
Amplitude is still present, and is more than or equal to definite value according to generator side 3U0, stator ground fault protection works, and system side 3U0 is more than or equal to
Definite value, the inoperative protection blocking criterion of stator ground fault protection, test stator ground fault protection are in open state, work as generating
When machine 3U0 amplitude and duration are more than protection definite value, stator ground fault protection malfunction chaser.
4. a kind of blocking method for preventing transfer overvoltage from causing generator stator ground false protection as claimed in claim 3,
It is characterized in that：In the step (3), the computational methods of residual voltage mixing frequencies are：
The inherent feature frequency of equivalent circuit is calculated as follows, and ignores the resistance parameter in circuit：
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Wherein, Z is the equiva lent impedance of circuit；ω is angular frequency, makes molecule, denominator zero, and circuit feature frequency is：
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Wherein, C1Become equivalent binding capacitance value, C for boosting2For generator equivalent capacitance value over the ground, L1For arc suppression coil inductance value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510421004.1A CN105071347B (en) | 2015-07-17 | 2015-07-17 | Prevent transfer overvoltage from causing the blocking method of generator stator ground false protection |
Applications Claiming Priority (1)
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| CN108802573A (en) * | 2018-06-28 | 2018-11-13 | 西门子电力自动化有限公司 | Detect the method and apparatus that earth fault disappears in electric system compensation network |
| CN113937737A (en) * | 2020-07-13 | 2022-01-14 | 长沙理工大学 | Ground fault processing method for generator stator and auxiliary power system |
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