CN111756017A - Transient torque out-of-limit rapid protection method and device for steam turbine generator unit - Google Patents

Transient torque out-of-limit rapid protection method and device for steam turbine generator unit Download PDF

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CN111756017A
CN111756017A CN201910235729.XA CN201910235729A CN111756017A CN 111756017 A CN111756017 A CN 111756017A CN 201910235729 A CN201910235729 A CN 201910235729A CN 111756017 A CN111756017 A CN 111756017A
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value
limit
time
protection
steam turbine
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CN111756017B (en
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张琦雪
马志恒
王凯
肖鹏
赵锦忠
王新宝
王光
陈俊
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NR Electric Co Ltd
NR Engineering Co Ltd
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NR Engineering Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks

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Abstract

The invention discloses a transient torque out-of-limit rapid protection method and a transient torque out-of-limit rapid protection device for a steam turbine generator unitampAnd meanwhile, the protection device detects the machine end current power frequency variation amplitude Delta IampAmplitude delta P of transient electromagnetic active power fluctuation componentamp(ii) a When Δ IampOr Δ PampThe off-limit protection is started and kept for T1 time; after the protection is started, the rotation speed difference fluctuation amplitude delta omega is carried outampJudging the fixed time limit and the inverse time limit protection; the rotation speed measurement channel is self-checked to be abnormal, or when the generator is not connected to the grid, the locking is protected; when the timed or anti-timed protection action is performed and there is no protection lockout, the protection action exit disconnects the generator. The invention has the advantages of rapidity and reliability and easy realization.

Description

Transient torque out-of-limit rapid protection method and device for steam turbine generator unit
Technical Field
The invention belongs to the technical field of relay protection of power systems, and particularly relates to a transient torque protection method and device for subsynchronous torsional vibration of a steam turbine generator unit.
Background
The turbo generator set has a long shaft system, and generally comprises a steam turbine high-pressure cylinder rotor, an intermediate-pressure cylinder rotor, a low-pressure cylinder rotor and a generator rotor. When the unit operates stably, the whole rotor large shaft is similar to a rigid body and rotates at a high speed. When the power grid has subsynchronous oscillation, under the interaction of the power grid, the rotors of the shaft system of the steam turbine generator unit may have torsional oscillation phenomenon of mutual torsional oscillation. The subsynchronous oscillation and torsional oscillation are harmful greatly, which not only affects the safety and stability of the power grid, but also can cause the fatigue damage of the shafting of the turbo generator set, reduce the service life of the set, and even lead to the crack of the large shaft in serious cases, thereby causing huge loss.
Theoretical research and engineering practice show that when the steam turbine generator unit adopts a point-to-grid long-distance power transmission mode and capacitor series compensation equipment is arranged on a power transmission line, subsynchronous oscillation of a power grid and torsional vibration of a shafting of the steam turbine generator unit are easily caused. When the natural oscillation frequency of the power grid system containing the capacitor series compensation is close to and complementary with the natural oscillation frequency of the torsional oscillation of the shaft system of the steam turbine generator unit, and disturbance occurs on the power grid side, a very large impact torque can be generated on the rotor shaft system, and the torque even exceeds the torque generated by the three-phase short circuit fault of the power grid system under the condition of no capacitor series compensation. This phenomenon is called "transient torque amplification". The method can cause damage to a shaft system of the steam turbine generator unit in a short time, so that rapid and reliable transient torque protection is needed.
Aiming at a turbo-generator unit with subsynchronous oscillation and torsional vibration risks, in order to ensure the safe operation of the unit, special torsional vibration protection (TSR protection) is installed at present, the basic method is to measure the rotating speed of a large shaft of the generator unit, obtain the component of each torsional vibration modal frequency from the rotating speed through modal decomposition of a plurality of cascade filters, identify the torque between rotor mass blocks by adopting a simplified equivalent rotor multi-mass-block equivalent model, calculate the fatigue value generated by the torque by combining a stress-life curve (S-N curve), and protect and disconnect the generator when the fatigue value exceeds a preset fixed value.
The existing torsional vibration protection (TSR protection) can effectively deal with the influence of torsional vibration on the large shaft of the unit under the general condition, and the generator is disconnected in time, so that the generator is separated from a power grid, and the fatigue damage of the large shaft of the unit caused by long-time torsional vibration is avoided. However, this method also has certain disadvantages: the protection cannot act quickly for very impulsive torsional oscillations, i.e. transient torque amplification. As known from the introduction of chapter 11 of analysis and control of subsynchronous resonance of power system (xie xiao reign, science publishers, 2015), TSR protection requires complex filtering including low-pass filtering (formula 11.3), high-pass filtering (formula 11.4), band-stop filtering (formula 11.5), and mode filtering (formula 11.9) in identifying torque, where the mode filtering is a series of band-pass band-stop filters cascaded in relation to torsional mode frequency, and after the series of processing, the identified torque is obtained and has a significant delay compared with the actual torque; for example, as can be seen in fig. 11.16, the identified torque will match the actual torque after a fault-impact disturbance for about 0.5 seconds. In addition, since the fatigue calculation is performed after the torque is obtained, a small amount of delay is required, and thus the TSR protection does not satisfy the requirement for the fast operation of the transient torque protection.
In the prior art, there is a method for protecting the operation after directly detecting that the deviation of the torsional vibration rotating speed exceeds a preset value. Although this method is fast, it relies only on the tacho signal measurement and risks protection malfunctions.
In addition, patent CN201410484589.7 "method and system for monitoring large disturbance transient impact torsional vibration of shafting of turbo generator set" discloses a method, which measures three-phase current and voltage of the generator, calculates corresponding electromagnetic torque on line in real time, protects and alarms when the electromagnetic torque value exceeds an alarm threshold, and sends a trip protection signal when the electromagnetic torque value exceeds a trip protection threshold. The method can effectively realize the torque out-of-limit protection of the turbo generator unit under the condition of transient impact including large disturbance such as two-phase short circuit, three-phase short circuit, asynchronous closing and the like, but the method also has some defects: (1) modeling simulation is needed, and the relation between the electromagnetic torque and the fatigue life loss of the shafting under the condition of large disturbance of the power system is established, so that the method is complex; (2) a 5-order model of the synchronous generator is used for calculating the electromagnetic torque, the calculation accuracy depends on model parameters, and the parameters are often nonlinear under the actual large disturbance condition; (3) although the electromagnetic transient of the rotor excitation winding and the rotor damping winding is considered, the electromagnetic transient of the stator is ignored, and the electromagnetic moment calculation has certain errors; (4) the method completely depends on the electric quantity of the generator, does not consider the electromagnetic moment calculation error caused by the abnormity of the voltage and current measuring loop, and has low reliability.
Disclosure of Invention
The purpose of the invention is: the method and the device for reliable and quick transient torque protection solve the problem that the existing TSR protection action speed is not enough, and simultaneously solve the problem that torque protection is unreliable depending on single measurement signals such as a rotating speed signal or electric quantity of a generator and the like, thereby realizing the quick transient torque protection of the steam turbine generator unit under the conditions of subsynchronous oscillation and transient torque amplification of torsional oscillation.
In order to achieve the purpose, the invention adopts the technical scheme that:
a transient torque out-of-limit rapid protection method for a steam turbine generator unit comprises the following steps:
step (1): measuring the rotation speed signal of the large shaft of the steam turbine generator unit, and calculating the rotation speed difference fluctuation amplitude delta omega of the large shaft of the steam turbine generator unitamp；
Step (2): measuring instantaneous value of three-phase current at turbine end of steam turbine generator, and calculating power frequency variation amplitude delta I of current at turbine end of steam turbine generatoramp；
And (3): measuring instantaneous values of three-phase current and three-phase voltage at turbine end of steam turbine generatorCalculating the amplitude delta P of the fluctuation component in the transient electromagnetic active power of the steam turbine generator unitamp；
And (4): judging the starting condition: when the Δ IampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
and (5): judging a locking condition: when the self-checking result of the rotating speed measuring channel is abnormal, setting a locking Flag2 as 1; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
and (6): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
and (7): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and (8): the protection operation exit determination disconnects the generator from the protection operation exit when the limit time protection operation Flag3 is 1 and the lock Flag2 is 0, or when the inverse limit time protection operation Flag4 is 1 and the lock Flag2 is 0.
The steps (1), (2) and (3) are not sequenced; the steps (6) and (7) are not separated in sequence.
Further, the rotation speed difference fluctuation amplitude Δ ω in the above step (1)ampThe following steps are taken for calculation:
step (1.1): measuring a large shaft rotating speed signal omega of the steam turbine generator unit;
step (1.2): fruit of Chinese wolfberrySubtracting the rated speed signal omega from the measured speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
Step (1.3): filtering the original rotation speed difference signal delta omega' according to the following formula, eliminating a high-frequency noise signal, reserving a subsynchronous oscillation component, and obtaining a filtered rotation speed difference signal delta omega:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
step (1.4): calculating the maximum value delta omega of delta omega by adopting a peak value detection method of a moving data windowmaxAnd minimum value Δ ωmin：
Figure BDA0002008122020000041
Figure BDA0002008122020000042
Wherein T is the current moment, T is the set data window duration, T is related to the torsional vibration natural modal frequency of the turbo generator set, and the value of T is 1/f which is 1.05-1.2 timesm,minWherein f ism,minThe minimum torsional natural mode frequency; function(s)
Figure BDA0002008122020000043
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure BDA0002008122020000044
Means the minimum value of the rotational speed difference Δ ω in the time range from the time (T-T) to the time T;
step (1.5): calculating the fluctuation amplitude delta omega of the rotation speed differenceamp＝(Δωmax-Δωmin)/2。
Further, the machine end current power frequency variation amplitude Δ I in the step (2)ampThe following steps are taken for calculation:
step (2.1): measuring turbogeneratorInstantaneous value i of three-phase current at generator enda、ib、ic；
Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
step (2.3): calculating the power frequency variation instantaneous value delta i by adopting a full-cycle Fourier calculation methoda、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure BDA0002008122020000051
Further, the amplitude Δ P of the wave component in the transient electromagnetic active power in the step (3) isampThe following steps are taken for calculation:
step (3.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、icInstantaneous value u of three-phase voltage at measuring machine enda、ub、uc；
Step (3.2): calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure BDA0002008122020000052
Figure BDA0002008122020000053
Wherein T is the current moment, T is the set data window duration, T is related to the torsional vibration natural modal frequency of the turbo generator set, and the value of T is 1/f which is 1.05-1.2 timesm,minWherein f ism,minThe minimum torsional natural mode frequency; function(s)
Figure BDA0002008122020000054
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure BDA0002008122020000055
Refers to the minimum value of p in the time range from time (T-T) to time T;
step (3.4): calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
Further, in the step (4), the current threshold Δ I is presetthThe value range of (1) is 0.1-1.0 times of rated current of the generator, and an active threshold value delta P is presetthThe value range of (A) is 0.1-1.0 times of the rated power of the generator, and the value range of T1 is 0.5-10.0 s.
Further, the specific determination method of the timing deadline protection in the step (6) is as follows: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
Further, the inverse time limit protection in the step (7) is specifically determined by:
step (7.1): two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure BDA0002008122020000061
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000062
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxThe value range is 105% -120% for the inverse time limit accumulation upper limit value; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
step (7.3): when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000063
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
step (7.4): after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
The invention also provides a transient torque out-of-limit rapid protection device for the steam turbine generator unit, which comprises
The measuring unit is used for measuring a large shaft rotating speed signal of the steam turbine generator unit and measuring a three-phase current instantaneous value and a three-phase voltage instantaneous value at the end of the steam turbine generator;
a rotation speed difference fluctuation amplitude calculation unit for calculating the rotation speed signal of the turbonator according to the turbonator of the measurement unitRotation speed difference fluctuation amplitude delta omega of group large shaftamp；
A machine end current power frequency variation amplitude calculation unit for calculating machine end current power frequency variation amplitude delta I of the turbo generator unit according to the instantaneous value of the three-phase current at the machine end of the turbo generator of the measurement unitamp；
The transient electromagnetic active power fluctuation component calculation unit is used for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active power of the steam turbine generator unit according to the turbine generator end three-phase current instantaneous value and the three-phase voltage instantaneous value of the measurement unitamp；
A start condition determination unit: for judging when the Δ I isampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
a locking condition determination unit: the locking Flag2 is set to 1 when the self-checking result of the rotating speed measuring channel is abnormal; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
a speed difference fluctuation amplitude timing protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
a speed difference fluctuation amplitude inverse time limit protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and a protection operation exit determination unit for disconnecting the generator from the protection operation exit when the limit time protection operation Flag3 is 1 and the lock Flag2 is 0, or when the inverse time protection operation Flag4 is 1 and the lock Flag2 is 0.
Further, the rotating speed difference fluctuation amplitude calculation unit comprises the following sub-units:
an original rotation speed difference signal calculating subunit for subtracting the rated rotation speed signal omega according to the actually measured rotation speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
The filtering subunit is configured to filter the original rotation speed difference signal Δ ω' according to the following formula, eliminate a high-frequency noise signal, retain a subsynchronous oscillation component, and obtain a filtered rotation speed difference signal Δ ω:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
a maximum and minimum rotation speed difference calculating subunit, configured to calculate a maximum value Δ ω of Δ ω by using a moving data window peak detection methodmaxAnd minimum value Δ ωmin：
Figure BDA0002008122020000081
Figure BDA0002008122020000082
Where T is the current time, T is the set data window duration, a function
Figure BDA0002008122020000083
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure BDA0002008122020000084
Means the minimum value of the rotational speed difference Δ ω in the time range from the time (T-T) to the time T;
a rotation speed difference fluctuation amplitude value operator unit for calculating the rotation speed difference fluctuation amplitude value delta omegaamp＝(Δωmax-Δωmin)/2。
Further, the machine end current power frequency variation amplitude calculation unit comprises the following subunits:
a power frequency variation instantaneous value calculating subunit, which is used for calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
an operator unit for calculating the instantaneous value delta i of power frequency variation by full cycle Fourier calculationa、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure BDA0002008122020000085
Further, the transient electromagnetic active power fluctuation component calculation unit includes the following sub-units:
a transient electromagnetic active power calculating subunit for calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
A maximum and minimum transient electromagnetic active power calculating subunit for calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure BDA0002008122020000091
Figure BDA0002008122020000092
Where T is the current time and T isSet duration of data window, function
Figure BDA0002008122020000093
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure BDA0002008122020000094
Refers to the minimum value of p in the time range from time (T-T) to time T;
an active power fluctuation component amplitude calculation unit for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
Further, the preset current threshold Δ I in the starting condition determination unitthThe value range of (a) is 0.1-1.0 times of the rated current of the generator.
Further, the preset active threshold Δ P in the starting condition determination unitthThe value range of (a) is 0.1-1.0 times of the rated power of the generator.
Further, the time of holding T1 in the activation condition determination unit may be set to a value of T1 ranging from 0.5s to 10.0 s.
Further, the timing time-limit protection in the rotational speed difference fluctuation amplitude timing time-limit protection unit specifically includes: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
Further, the inverse time limit protection in the rotating speed difference fluctuation amplitude inverse time limit protection unit is specifically as follows:
two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure BDA0002008122020000095
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000096
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000101
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
Further, the data window duration T set in the mobile data window peak value detection method is related to the natural modal frequency of the torsional vibration of the turbo generator set, and the value of T is 1/f of 1.05-1.2 timesm,minWherein f ism,minIs the minimum torsional natural mode frequency.
The invention has the beneficial effects that: (1) by the locking protection actions such as self-checking abnormity of the rotating speed measuring channel and the like, the reliability of protection is improved by a method of combining the fault characteristics of a rotating speed signal of a unit with the fault characteristics of electric quantity at the generator end, and the unreliable problem of protection of single signals such as the rotating speed signal or the electric quantity signal of the generator is solved; (2) by reducing the filtering link and adopting the technical means such as a mobile data window peak value detection method and the like, the protection rapidity is improved, and the problem that the protection cannot be rapidly operated under the transient torque amplification condition of the TSR is solved.
Drawings
FIG. 1 is a schematic view of a rotor structure of an example machine set, wherein HIP is a high and medium pressure cylinder rotor, LP is a low pressure cylinder rotor, and GEN is a generator rotor;
FIG. 2 is a schematic diagram of a simple model of a multi-mass block of an example unit, where HIP is a high and medium pressure cylinder rotor, LP is a low pressure cylinder rotor, GEN is a generator rotor, and J1、J2、J3Moment of inertia, D, of HIP, LP, GEN, respectively1、D2、D3Self-damping of torsional mechanical movements, K, of HIP, LP, GEN, respectively12Is the torsional stiffness between HIP and LP, K23Is the torsional stiffness between LP and GEN;
FIG. 3 is a schematic diagram of a torsional Mode of an example unit, wherein Mode1 represents Mode1 and Mode2 represents Mode 2;
FIG. 4 is a graph of stress-fatigue life for journal locations corresponding to bearing #4 for an exemplary assembly using a semi-logarithmic coordinate system with the abscissa of the graph representing the number of allowable torsional cycles and the ordinate representing torsional torque;
FIG. 5 is a schematic diagram of the protective wiring of the present invention, in which CT represents a current transformer and PT represents a voltage transformer;
FIG. 6 is a schematic flow chart of the method steps of the present invention;
FIG. 7 is a schematic view of an inverse time-limited characteristic curve of the method of the present invention, with the abscissa being the amplitude of the fluctuation of the differential rotational speed and the ordinate being time;
fig. 8 is a schematic view of the apparatus of the present invention.
Detailed Description
For the purpose of illustrating the method of the invention in detail, reference is made to the accompanying drawings which illustrate a specific embodiment of the invention.
Example 1:
fig. 5 and fig. 6 are schematic diagrams illustrating a connection diagram and a flow chart of method steps of a transient torque out-of-limit rapid protection method for a steam turbine generator unit according to the present invention, wherein an embodiment of the method of the present invention includes the following steps:
step (1): measuring the rotation speed signal of the large shaft of the steam turbine generator unit, and calculating the rotation speed difference fluctuation amplitude delta omega of the large shaft of the steam turbine generator unitamp。
Step (1.1): measuring a large shaft rotating speed signal omega of the steam turbine generator unit;
step (1.2): subtracting the rated speed signal omega from the actually measured speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
Step (1.3): filtering the original rotation speed difference signal delta omega' according to the following formula, eliminating a high-frequency noise signal, reserving a subsynchronous oscillation component, and obtaining a filtered rotation speed difference signal delta omega:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
step (1.4): calculating the maximum value delta omega of delta omega by adopting a peak value detection method of a moving data windowmaxAnd minimum value Δ ωmin：
Figure BDA0002008122020000121
Figure BDA0002008122020000122
Wherein T is the current moment, T is the set data window duration and is related to the torsional vibration natural modal frequency of the turbo generator set, and the value of T is 1/f which is 1.05-1.2 timesm,minWherein f ism,minIs the minimum torsional natural mode frequency. Function(s)
Figure BDA0002008122020000123
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure BDA0002008122020000124
Means the minimum value of the rotational speed difference Δ ω in the time range from the time (T-T) to the time T;
step (1.5): calculating the fluctuation amplitude delta omega of the rotation speed differenceamp＝(Δωmax-Δωmin)/2。
Step (2): measuring instantaneous value of three-phase current at turbine end of steam turbine generator, and calculating power frequency variation amplitude delta I of current at turbine end of steam turbine generatoramp。
Step (2.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、ic；
Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
step (2.3): calculating the power frequency variation instantaneous value delta i by adopting a full-cycle Fourier calculation methoda、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure BDA0002008122020000125
And (3): measuring three-phase current instantaneous value and three-phase voltage instantaneous value at turbine end of steam turbine generator, and calculating amplitude delta P of fluctuation component in transient electromagnetic active power of steam turbine generator unitamp。
Step (3.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、icInstantaneous value u of three-phase voltage at measuring machine enda、ub、uc；
Step (3).2): calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure BDA0002008122020000131
Figure BDA0002008122020000132
Wherein T is the current moment, T is the set data window duration and is related to the torsional vibration natural modal frequency of the turbo generator set, and the value of T is 1/f which is 1.05-1.2 timesm,minWherein f ism,minIs the minimum torsional natural mode frequency. Function(s)
Figure BDA0002008122020000133
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure BDA0002008122020000134
Refers to the minimum value of p in the time range from time (T-T) to time T;
step (3.4): calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
And (4): judging the starting condition: when the Δ IampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the enable Flag1 is set to 0. Wherein the preset current threshold value delta IthThe value range of (a) is 0.1-1.0 times of the rated current of the generator. Presetting active power threshold value delta PthThe value range of (a) is 0.1-1.0 times of the rated power of the generator. The value range of the time for keeping T1 is 0.5 s-10.0 s.
And (5): judging a locking condition: when the self-checking result of the rotating speed measuring channel is abnormal, setting a locking Flag2 as 1; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0.
And (6): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0. The specific judging method of the timing time limit protection comprises the following steps: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
And (7): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0.
The specific discrimination method of inverse time limit protection is as follows:
step (7.1): two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure BDA0002008122020000141
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000142
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxThe value range is 105% -120% for the inverse time limit accumulation upper limit value; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
step (7.3): when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000143
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
step (7.4): after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
And (8): a protection operation exit judgment step of, when the definite time protection operation Flag3 is 1 and the locking Flag2 is 0, or when the inverse time protection operation Flag4 is 1 and the locking Flag2 is 0, disconnecting the generator from the protection operation exit;
the steps (1), (2) and (3) are not sequenced; the steps (6) and (7) are not separated in sequence.
Example 2:
fig. 1 is a schematic structural diagram of a rotor of a certain steam turbine generator unit with a rated power of 350 MW. The main parameters of the generator set are as follows: rated capacity 412MVA, rated power factor 0.85, rated voltage 20kV, rated phase voltage Un, ph 20kV/1.732 11.547kV, rated current 11.887 kA. The rotor of the unit consists of a high-intermediate pressure cylinder rotor (HIP) of a steam turbine, a low-pressure cylinder rotor (LP) and a generator rotor (GEN), wherein the rotors are connected through a coupler, a #1 coupler is arranged between the HIP and the LP, a #2 coupler is arranged between the LP and the GEN, two sides of each rotor are respectively provided with a bearing support, and bearings from the steam turbine side to the generator side are sequentially from the #1 bearing to the #6 bearing.
When analyzing the problem of subsynchronous oscillation and torsional oscillation of the steam turbine generator unit, the rotor of the unit can be simplified into a multi-mass spring body, as shown in fig. 2. The rotational inertia of the three rotors of HIP, LP and GEN is J1、J2、J3Mechanical self-damping is D1、D2、D3Torsional stiffness between HIP and LP is K12Torsional stiffness between LP and GEN is K23And mechanical mutual damping exists between the rotors. To simplify the analysis, mechanical self-damping and mechanical mutual damping were omitted. The parameters of the rotational inertia and the torsional rigidity of the unit are as follows:
Figure BDA0002008122020000151
through calculation, the rotor system has two subsynchronous torsional vibration modes, and the natural modal frequencies of the torsional vibration are respectively fm1＝23.25Hz，fm2The corresponding torsional mode is shown in fig. 3 at 30.53Hz, and the normalized mode coefficient is:
serial number Modality HIP LP GEN
1 Mode1 -0.891 -0.231 1.000
2 Mode2 1.000 -0.276 0.246
When the rotor of the unit is in torsional vibration, the positions of the #1 coupler and the #2 coupler and the positions of the shaft necks corresponding to the #2 to the #5 bearings bear large torque of cyclic torsion, the torque can generate fatigue on the sections, and the continuous large torsional vibration can cause fatigue damage to the sections. For simplicity of illustration, as shown in fig. 4, only the stress-fatigue life curve of the journal location corresponding to the bearing #4 is shown, and the graph uses a semilogarithmic coordinate system, wherein the abscissa is the allowable number of torsional cycles and the ordinate is the torsional torque.
The method of the invention is as shown in figure 5, the protection device is accessed into a turbonator large shaft rotating speed signal, a generator terminal current transformer signal and a generator terminal voltage transformer signal, and the method is realized by adopting the steps as shown in figure 6, and the specific implementation steps are as follows:
step (1): measuring rotation speed difference fluctuation amplitude delta omega of large shaft of steam turbine generator unitamp；
Step (2): measuring power frequency variation amplitude delta I of current at turbine end of steam turbine generator unitamp；
And (3): measuring amplitude delta P of fluctuation component in transient electromagnetic active power of steam turbine generator unitamp；
And (4): judging the starting condition: when the Δ IampOver a constant value Δ IthOr said Δ PampOver a constant value Δ PthAt the time, the start flag Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
and (5): judging a locking condition: when the self-checking result of the rotating speed measuring channel is abnormal, setting a locking Flag2 as 1; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
and (6): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
and (7): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and (8): the protection operation exit determination disconnects the generator from the protection operation exit when the limit time protection operation Flag3 is 1 and the lock Flag2 is 0, or when the inverse limit time protection operation Flag4 is 1 and the lock Flag2 is 0.
In the above scheme, the rotation speed difference fluctuation amplitude Δ ω in the step (1) aboveampThe following steps are taken for calculation:
step (1.1): measuring a large shaft rotating speed signal omega of the steam turbine generator unit;
step (1.2): subtracting the rated speed signal omega from the actually measured speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan(ii) a For this example, the rated speed of the unit is 3000rpm, so ωn＝100πrad/s；
Step (1.3): filtering the original rotation speed difference signal delta omega' according to the following formula, eliminating a high-frequency noise signal, reserving a subsynchronous oscillation component, and obtaining a filtered rotation speed difference signal delta omega:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is a low-pass filter HLP(s) and band-stop filter HBS(s) a cascade; the specific design of the filter is as follows:
low pass filter HLP(s) and band stop filter HBS(s) are both second order filters; low pass filter HLP(s) for eliminating high-frequency noise, HLPGain of 1, frequency of 0.8 times of cut-off frequency, i.e. 0.8 × 50 Hz-40 Hz, damping coefficient of 0.707, band-stop filter HBS(s) for eliminating power frequency noise, HBS(s) the gain is 1, the central frequency is the power frequency, namely 50Hz, and the damping coefficient is 0.04; because the order of the filter is not high, only two stages are cascaded, so that the delay generated by the filter is very short;
step (1.4): calculating the maximum value delta omega of delta omega by adopting a peak value detection method of a moving data windowmaxAnd minimum value Δ ωmin：
Figure BDA0002008122020000171
Figure BDA0002008122020000172
Wherein T is the current time, T is the set data window duration, T is related to the natural torsional vibration modal frequency of the steam turbine generator unit, and the minimum natural torsional vibration modal frequency f is takenm,minThe value of T is 1/f which is 1.05-1.2 timesm,min(ii) a Function(s)
Figure BDA0002008122020000181
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure BDA0002008122020000182
The minimum value of the speed difference Δ ω in the time range from time (T-T) to time T, for the present example, the data window duration T is 1.1 × 1/23.25Hz is 0.047 s;
finally, step (1.5): calculating the difference of rotational speedsAmplitude of fluctuation Δ ωamp＝(Δωmax-Δωmin)/2。
The method for calculating the fluctuation amplitude of the rotating speed difference has the advantages that the peak value detection method of the mobile data window is generally shorter in time delay than the conventional full-cycle Fourier calculation method, and the influence of rigid motion fluctuation of the whole rotor under the working conditions of low-frequency oscillation, step loss, load shedding and the like of the turbonator can be effectively avoided by calculating in the mobile data window within a set short time, so that multi-stage filtering and complex modular filtering of rotating speed signals are not needed, the calculation link is simplified, and the time delay is greatly reduced. The invention aims at the severe condition of transient torque amplification in the process of subsynchronous oscillation and torsional oscillation of the turbo generator set, does not need to calculate tiny torsional oscillation modal components very accurately, only needs to reflect larger torque which is twisted and swung back and forth, reflects larger torsional oscillation through the fluctuation amplitude of the rotation speed difference, and can properly ignore accurate measurement so as to replace protection rapidity.
In the above scheme, the machine end current power frequency variation amplitude Δ I in the step (2) aboveampThe following steps are taken for calculation:
step (2.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、ic；
Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase; for this example, T1st＝20ms；
Step (2.3): calculating the power frequency variation instantaneous value delta i by adopting a full-cycle Fourier calculation methoda、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure BDA0002008122020000183
In the above scheme, the amplitude Δ P of the fluctuation component in the transient electromagnetic active power in step (3) isampThe following steps are taken for calculation:
step (3.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、icInstantaneous value u of three-phase voltage at measuring machine enda、ub、uc；
Step (3.2): calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure BDA0002008122020000191
Figure BDA0002008122020000192
Wherein T is the current time, T is the set data window duration, T is related to the natural torsional vibration modal frequency of the steam turbine generator unit, and the minimum natural torsional vibration modal frequency f is takenm,minThe value of T is 1/f which is 1.05-1.2 timesm,min(ii) a Function(s)
Figure BDA0002008122020000193
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure BDA0002008122020000194
P is the minimum value in the time range from time (T-T) to time T, for the present example, the data window duration T is 1.1 × 1/23.25Hz is 0.047 s;
step (3.4): calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
Similar to the aforementioned calculation of the fluctuation amplitude of the rotating speed difference, when the amplitude of the fluctuation component in the transient electromagnetic active power is calculated, a similar moving data window peak detection method is adopted, and the time delay is generally shorter than that of the conventional full cycle Fourier calculation method. It is known that the steady-state electromagnetic active power directly reflects the electromagnetic torque of the generator, and the steady-state electromagnetic active power is divided by the rotating speed to obtain the steady-state electromagnetic torque. Although the transient electromagnetic active power does not directly reflect the electromagnetic torque of the generator, the fluctuation of the transient electromagnetic active power directly reflects the torque impact of the power grid system on the steam turbine generator unit, which is a necessary condition for causing transient torque amplification.
In the above embodiment, in the step (4), the value Δ I is fixedthThe value range of (1) is 0.1-1.0 times of the rated current of the generator, and the constant value delta PthThe value range of (A) is 0.1-1.0 times of the rated power of the generator, and the value range of T1 is 0.5-10.0 s. For this example, T1 ═ 1.0 s.
In the foregoing solution, the specific determination method of the timing deadline protection in the step (6) is as follows: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
For the present embodiment, taking a timer protection as an example, the method for setting the fixed value is as follows:
(a) the number of torsional cycles of low cycle fatigue ranges from 1 to 103Next, the number of cycles was found to be 10 in the stress-fatigue life curve of FIG. 43The unit value of the secondary allowable torque amplitude is 4.12p.u., and the base value of the unit value is the rated torque corresponding to the rated active power of the generator;
(b) assuming that the unit generates steady-state torsional vibration with modal 1 or modal 2 frequency, calculating the corresponding quantitative relation between the fluctuation amplitude of the rotation speed difference and the torque amplitude according to the parameters of the equivalent model of the multi-mass block spring body of the unit; comparing the steady-state torsional vibration of the mode1 with the steady-state torsional vibration of the mode2, wherein the torsional vibration torque of the mode1 is more serious under the same rotating speed difference fluctuation amplitude at the journal of the #4 bearing position, so that the rotating speed difference fluctuation amplitude of the mode1 corresponding to the torque amplitude of 4.12p.u. is 4.463rad/s by calculating according to the torsional vibration condition of the mode 1;
(c) calculating modal 1 frequency cycle 103The next time is 1/23.25Hz × 1000 43.011s, and the fatigue limit is 1%, i.e. 10 torsion is allowed at 4.12p.u. torque amplitude3× 1 ═ 10 times, corresponding to a time of 1/23.25Hz × 10 ═ 0.43 s;
(d) considering that the protection device possibly has errors in calculation, considering that a transient process is different from a steady-state process to a certain extent, for safety, a certain safety margin is required to be given when the out-of-limit threshold fixed value is calculated, and if the safety margin is set to be 1.5, the rotating speed difference fluctuation amplitude out-of-limit threshold is (4.463rad/s)/1.5 to 2.975 rad/s; the delay constant is taken to be 0.4 s.
The above is only an example of setting the fixed value of the timing time limit protection, and obviously, the multi-stage fixed value of the timing time limit protection can be set according to the requirement, and the higher the out-of-limit threshold is, the shorter the delay fixed value is.
In the above scheme, the inverse time limit protection in the step (7) specifically determines that:
step (7.1): two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure BDA0002008122020000201
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000202
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxThe value range of (A) is 105-120%; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
step (7.3): when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000211
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
step (7.4): after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
For the present example, the method of setting the fixed value in step (7.1) is:
(a) similar to the above-mentioned fixed time limit protection fixed value setting method, the range of the number of torsional cycles of low cycle fatigue is 1 to 103Next, the number of cycles of 10 was found in the stress-fatigue life curve of FIG. 42Second, 103The unit values of the secondary allowable torque amplitude are 6.30p.u. and 4.12p.u. respectively, and the base value of the unit value is the rated torque corresponding to the rated active power of the generator;
(b) similarly, assuming that the unit generates steady-state torsional vibration with modal 1 or modal 2 frequency, and according to the parameters of the equivalent model of the multi-mass block spring body of the unit, calculating the corresponding quantitative relation between the fluctuation amplitude of the rotation speed difference and the torque amplitude; comparing the steady-state torsional vibration of the mode1 with the steady-state torsional vibration of the mode2, at the journal of the #4 bearing position, under the same rotating speed difference fluctuation amplitude, the torsional vibration moment of the mode1 is more serious, so that the rotating speed difference fluctuation amplitudes of the mode1 corresponding to the torque amplitudes of 6.30p.u. and 4.12p.u. are 6.824rad/s and 4.463rad/s respectively by calculating according to the torsional vibration condition of the mode 1;
(c) calculating modal 1 frequency cycle 103The next time is 1/23.25Hz × 1000 43.011s, and the fatigue limit is 2%, allowing 10 torsions at 4.12p.u. torque amplitude3× 2% ═ 20 times, corresponding to a time of 1/23.25Hz × 20 ═ 0.86s, and allow torsion 10 at 6.30p.u. torque amplitude2× 2% ═ 2 times, which corresponds to a time of 1/23.25Hz × 2 ═ 0.086 s;
(d) considering that the calculation of the protection device may have errors, considering that a certain difference exists between the transient process and the steady-state process, for safety, a certain safety margin should be given when calculating the out-of-limit threshold fixed value, and setting the safety margin as 1.5, the minimum out-of-limit threshold delta omega is obtainedth,minIs (4.463rad/s)/1.5 to 2.975rad/s, and the maximum out-of-limit threshold delta omega isth,maxIs (6.824rad/s)/1.5 ═ 4.549 rad/s; minimum delay timing Tth,minTaking an approximate value of 0.086s and a maximum delay fixed value Tth,maxTake 0.86 s.
The above is only an example of setting the fixed value of the inverse time-limit protection, and obviously, the fixed value may be adjusted as required, and it should be noted that, considering the reliability of the protection, the minimum delay fixed value of the inverse time-limit is not suitable to be less than twice of the period duration corresponding to the natural modal frequency.
In addition, the characteristic curve of the inverse time limit protection shown in fig. 7 is a three-fold line, which is easy to implement, and actually, the characteristic curve of the inverse time limit protection is not limited to the characteristic of a fold line, and other curve forms can be adopted.
Example 3:
fig. 8 shows an embodiment of the transient torque out-of-limit fast protection device for a steam turbine generator unit according to the present invention. The turbo generator set transient torque out-of-limit quick protection device of this embodiment includes:
the measuring unit is used for measuring a large shaft rotating speed signal of the steam turbine generator unit and measuring a three-phase current instantaneous value and a three-phase voltage instantaneous value at the end of the steam turbine generator;
a rotation speed difference fluctuation amplitude calculation unit for calculating the fluctuation amplitude of the rotation speed difference according to the turbo generator set of the measurement unitCalculating the rotation speed difference fluctuation amplitude delta omega of the large shaft of the steam turbine generator unit according to the rotation speed signal of the large shaftamp；
A machine end current power frequency variation amplitude calculation unit for calculating machine end current power frequency variation amplitude delta I of the turbo generator unit according to the instantaneous value of the three-phase current at the machine end of the turbo generator of the measurement unitamp；
The transient electromagnetic active power fluctuation component calculation unit is used for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active power of the steam turbine generator unit according to the turbine generator end three-phase current instantaneous value and the three-phase voltage instantaneous value of the measurement unitamp；
A start condition determination unit: for judging when the Δ I isampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
a locking condition determination unit: the locking Flag2 is set to 1 when the self-checking result of the rotating speed measuring channel is abnormal; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
a speed difference fluctuation amplitude timing protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
a speed difference fluctuation amplitude inverse time limit protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and a protection operation exit determination unit for disconnecting the generator from the protection operation exit when the limit time protection operation Flag3 is 1 and the lock Flag2 is 0, or when the inverse time protection operation Flag4 is 1 and the lock Flag2 is 0.
In the device, the rotating speed difference fluctuation amplitude calculation unit comprises the following subunits:
an original rotation speed difference signal calculating subunit for subtracting the rated rotation speed signal omega according to the actually measured rotation speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
The filtering subunit is configured to filter the original rotation speed difference signal Δ ω' according to the following formula, eliminate a high-frequency noise signal, retain a subsynchronous oscillation component, and obtain a filtered rotation speed difference signal Δ ω:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
a maximum and minimum rotation speed difference calculating subunit, configured to calculate a maximum value Δ ω of Δ ω by using a moving data window peak detection methodmaxAnd minimum value Δ ωmin：
Figure BDA0002008122020000231
Figure BDA0002008122020000232
Where T is the current time, T is the set data window duration, a function
Figure BDA0002008122020000233
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure BDA0002008122020000234
Means the minimum value of the rotational speed difference Δ ω in the time range from the time (T-T) to the time T;
a rotation speed difference fluctuation amplitude value calculation operator unit for calculating the rotation speed difference fluctuation amplitudeValue Δ ωamp＝(Δωmax-Δωmin)/2。
In the device, the machine end current power frequency variation amplitude calculation unit comprises the following subunits:
a power frequency variation instantaneous value calculating subunit, which is used for calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
an operator unit for calculating the instantaneous value delta i of power frequency variation by full cycle Fourier calculationa、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure BDA0002008122020000241
In the device, the transient electromagnetic active power fluctuation component calculation unit comprises the following subunits:
a transient electromagnetic active power calculating subunit for calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
A maximum and minimum transient electromagnetic active power calculating subunit for calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure BDA0002008122020000242
Figure BDA0002008122020000243
Where T is the current time, T is the set data window duration, a function
Figure BDA0002008122020000244
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure BDA0002008122020000245
Refers to the minimum value of p in the time range from time (T-T) to time T;
an active power fluctuation component amplitude calculation unit for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
In the present device, the preset current threshold Δ I in the starting condition discriminating unitthThe value range of (a) is 0.1-1.0 times of the rated current of the generator. The preset active threshold value delta P in the starting condition judging unitthThe value range of (a) is 0.1-1.0 times of the rated power of the generator. The value range of T1 is 0.5 s-10.0 s when the time of T1 is kept in the starting condition judging unit.
In the device, the timing time-limit protection in the timing time-limit protection unit for the fluctuation amplitude of the rotating speed difference specifically comprises the following steps: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
In the device, the inverse time limit protection in the rotating speed difference fluctuation amplitude inverse time limit protection unit is specifically as follows:
two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure BDA0002008122020000251
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum time delayConstant value, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000252
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure BDA0002008122020000253
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
In the device, the data window duration T set in the mobile data window peak value detection method is related to the torsional natural modal frequency of the turbo generator set, and the value of T is 1/f of 1.05-1.2 timesm,minWherein f ism,minIs the minimum torsional natural mode frequency.
The above examples are only for illustrating the technical idea of the present invention, and the scope of the present invention should not be limited thereby. Any equivalent replacement or modification on the basis of the technical scheme is not beyond the protection scope of the invention according to the technical idea provided by the invention.

Claims (20)

1. A transient torque out-of-limit rapid protection method for a steam turbine generator unit is characterized by comprising the following steps:
step (1): measuring the rotation speed signal of the large shaft of the steam turbine generator unit, and calculating the rotation speed difference fluctuation amplitude delta omega of the large shaft of the steam turbine generator unitamp；
Step (2): measuring instantaneous value of three-phase current at turbine end of steam turbine generator, and calculating power frequency variation amplitude delta I of current at turbine end of steam turbine generatoramp；
And (3): measuring three-phase current instantaneous value and three-phase voltage instantaneous value at turbine end of steam turbine generator, and calculating amplitude delta P of fluctuation component in transient electromagnetic active power of steam turbine generator unitamp；
And (4): judging the starting condition: when the Δ IampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
and (5): judging a locking condition: when the self-checking result of the rotating speed measuring channel is abnormal, setting a locking Flag2 as 1; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
and (6): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
and (7): when the start Flag1 is 1, the speed difference fluctuation amplitude Δ ω is carried outampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and (8): a protection operation exit judgment step of, when the definite time protection operation Flag3 is 1 and the locking Flag2 is 0, or when the inverse time protection operation Flag4 is 1 and the locking Flag2 is 0, disconnecting the generator from the protection operation exit;
the steps (1), (2) and (3) are not sequenced; the steps (6) and (7) are not separated in sequence.
2. The transient torque out-of-limit fast protection method for steam turbine generator unit as claimed in claim 1, wherein the fluctuation amplitude Δ ω of the rotational speed difference in the step (1) isampThe following steps are taken for calculation:
step (1.1): measuring a large shaft rotating speed signal omega of the steam turbine generator unit;
step (1.2): subtracting the rated speed signal omega from the actually measured speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
Step (1.3): filtering the original rotation speed difference signal delta omega' according to the following formula, eliminating a high-frequency noise signal, reserving a subsynchronous oscillation component, and obtaining a filtered rotation speed difference signal delta omega:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
step (1.4): calculating the maximum value delta omega of delta omega by adopting a peak value detection method of a moving data windowmaxAnd minimum value Δ ωmin：
Figure FDA0002008122010000021
Figure FDA0002008122010000022
Where T is the current time, T is the set data window duration, a function
Figure FDA0002008122010000023
Is referred to as the difference in rotational speed Δ ωMaximum value in the time range from (T-T) to T, function
Figure FDA0002008122010000024
Means the minimum value of the rotational speed difference Δ ω in the time range from the time (T-T) to the time T;
step (1.5): calculating the fluctuation amplitude delta omega of the rotation speed differenceamp＝(Δωmax-Δωmin)/2。
3. The transient torque out-of-limit rapid protection method for steam turbine generator unit as claimed in claim 1, wherein the terminal current power frequency variation amplitude Δ I in step (2)ampThe following steps are taken for calculation:
step (2.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、ic；
Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
step (2.3): calculating the power frequency variation instantaneous value delta i by adopting a full-cycle Fourier calculation methoda、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure FDA0002008122010000031
4. The transient torque out-of-limit fast protection method for turbo generator set according to claim 1, wherein the amplitude Δ P of the fluctuating component in the transient electromagnetic active power in step (3) isampBy takingThe calculation is carried out by the following steps:
step (3.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generatora、ib、icInstantaneous value u of three-phase voltage at measuring machine enda、ub、uc；
Step (3.2): calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection methodmaxAnd a minimum value pmin：
Figure FDA0002008122010000032
Figure FDA0002008122010000033
Where T is the current time, T is the set data window duration, a function
Figure FDA0002008122010000034
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure FDA0002008122010000035
Refers to the minimum value of p in the time range from time (T-T) to time T;
step (3.4): calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
5. The transient torque out-of-limit fast protection method for steam turbine generator unit as claimed in claim 1, wherein the preset current threshold Δ I in step (4)thThe value range of (a) is 0.1-1.0 times of the rated current of the generator.
6. The turbo-generator set transient torque overrun of claim 1The speed protection method is characterized in that the preset active power threshold value delta P in the step (4)thThe value range of (a) is 0.1-1.0 times of the rated power of the generator.
7. The transient torque out-of-limit rapid protection method for the steam turbine generator unit as claimed in claim 1, wherein the value range of T1 is 0.5 s-10.0 s when the time T1 is maintained in step (4).
8. The transient torque out-of-limit fast protection method for the steam turbine generator unit as claimed in claim 1, wherein the specific determination method for the timing time limit protection in step (6) is as follows: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
9. The transient torque out-of-limit fast protection method for the steam turbine generator unit as claimed in claim 1, wherein the inverse time limit protection in step (7) is specifically determined by:
step (7.1): two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure FDA0002008122010000041
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure FDA0002008122010000042
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
step (7.3): when the amplitude of fluctuation of the rotational speed difference is delta omegaampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure FDA0002008122010000043
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
step (7.4): after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
10. The transient torque out-of-limit fast protection method for the turbo generator set according to claim 2 or 4, wherein the data window duration T set in the moving data window peak detection method is related to the natural modal frequency of the turbo generator set torsional vibration, and the value of T is 1/f of 1.05-1.2 timesm,minWherein f ism,minIs the minimum torsional natural mode frequency.
11. A transient torque out-of-limit rapid protection device for a turbo generator set is characterized by comprising
The measuring unit is used for measuring a large shaft rotating speed signal of the steam turbine generator unit and measuring a three-phase current instantaneous value and a three-phase voltage instantaneous value at the end of the steam turbine generator;
a rotation speed difference fluctuation amplitude calculation unit used for calculating the fluctuation amplitude of the rotation speed difference according to the rotation speed signal of the main shaft of the steam turbine generator unit of the measurement unit,calculating the fluctuation amplitude delta omega of the rotation speed difference of the large shaft of the steam turbine generator unitamp；
A machine end current power frequency variation amplitude calculation unit for calculating machine end current power frequency variation amplitude delta I of the turbo generator unit according to the instantaneous value of the three-phase current at the machine end of the turbo generator of the measurement unitamp；
The transient electromagnetic active power fluctuation component calculation unit is used for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active power of the steam turbine generator unit according to the turbine generator end three-phase current instantaneous value and the three-phase voltage instantaneous value of the measurement unitamp；
A start condition determination unit: for judging when the Δ I isampExceeding a predetermined current threshold Δ IthOr said Δ PampExceeds a preset active power threshold value delta PthWhen the time is up, the Flag1 is set to 1 and kept for T1 time; otherwise, the start Flag1 is set to 0;
a locking condition determination unit: the locking Flag2 is set to 1 when the self-checking result of the rotating speed measuring channel is abnormal; when the generator is detected not to be connected to the grid, the locking Flag2 is set to 1; when the abnormal condition of the terminal voltage measuring circuit or the terminal current measuring circuit is detected, the locking Flag2 is set to 1; when the self-checking result of the rotating speed measuring channel is normal, the generator is connected to the grid, the terminal voltage measuring circuit is normal, and the terminal current measuring circuit is normal, the locking Flag2 is set to 0;
a speed difference fluctuation amplitude timing protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the fixed time limit protection meets the condition, setting a fixed time limit protection action Flag3 as 1; otherwise Flag3 is set to 0;
a speed difference fluctuation amplitude inverse time limit protection unit for carrying out the speed difference fluctuation amplitude delta omega when the start Flag1 is 1ampWhen the inverse time limit protection meets the condition, the inverse time limit protection action Flag4 is set to 1; otherwise Flag4 is set to 0;
and a protection operation exit determination unit for disconnecting the generator from the protection operation exit when the limit time protection operation Flag3 is 1 and the lock Flag2 is 0, or when the inverse time protection operation Flag4 is 1 and the lock Flag2 is 0.
12. The transient torque out-of-limit fast protection device of the steam turbine generator unit as claimed in claim 11, wherein the rotation speed difference fluctuation amplitude calculation unit comprises the following sub-units:
an original rotation speed difference signal calculating subunit for subtracting the rated rotation speed signal omega according to the actually measured rotation speed signal omeganTo obtain the original rotation speed difference signal delta omega ═ omega-omegan；
The filtering subunit is configured to filter the original rotation speed difference signal Δ ω' according to the following formula, eliminate a high-frequency noise signal, retain a subsynchronous oscillation component, and obtain a filtered rotation speed difference signal Δ ω:
Δ ω ═ h(s) · Δ ω' formula 1
Where H(s) is the cascaded transfer function of the low pass filter and the band stop filter;
a maximum and minimum rotation speed difference calculating subunit, configured to calculate a maximum value Δ ω of Δ ω by using a moving data window peak detection methodmaxAnd minimum value Δ ωmin：
Figure FDA0002008122010000061
Figure FDA0002008122010000062
Where T is the current time, T is the set data window duration, a function
Figure FDA0002008122010000063
Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function
Figure FDA0002008122010000064
Means that the difference in rotational speed Δ ω is between the time (T-T) and TMinimum value in the time range of the moment;
a rotation speed difference fluctuation amplitude value operator unit for calculating the rotation speed difference fluctuation amplitude value delta omegaamp＝(Δωmax-Δωmin)/2。
13. The transient torque out-of-limit rapid protection device of the steam turbine generator unit as claimed in claim 11, wherein the machine end current power frequency variation amplitude calculation unit comprises the following sub-units:
a power frequency variation instantaneous value calculating subunit, which is used for calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formulaa、Δib、Δic：
Δij(t)＝ij(t)-ij(t-T1st) j is a, b, c formula 4
Where T is the current time, T1stThe subscript j is a, b and c respectively represent a phase, b phase and c phase;
an operator unit for calculating the instantaneous value delta i of power frequency variation by full cycle Fourier calculationa、Δib、ΔicRespectively, of Δ Ia,amp、ΔIb,amp、ΔIc,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta IampI.e. by
Figure FDA0002008122010000071
14. The transient torque out-of-limit rapid protection device for a steam turbine generator unit as claimed in claim 11, wherein the transient electromagnetic active power fluctuation component calculation unit comprises the following sub-units:
a transient electromagnetic active power calculating subunit for calculating the transient electromagnetic active power p ═ uaia+ubib+ucic；
A maximum and minimum transient electromagnetic active power calculating subunit for calculating by adopting a moving data window peak value detection methodMaximum value p of pmaxAnd a minimum value pmin：
Figure FDA0002008122010000072
Figure FDA0002008122010000073
Where T is the current time, T is the set data window duration, a function
Figure FDA0002008122010000074
Refers to the maximum value of p in the time range from time (T-T) to time T
Figure FDA0002008122010000075
Refers to the minimum value of p in the time range from time (T-T) to time T;
an active power fluctuation component amplitude calculation unit for calculating the amplitude delta P of the fluctuation component in the transient electromagnetic active poweramp＝(pmax-pmin)/2。
15. The transient torque out-of-limit fast protection device for steam turbine generator unit as claimed in claim 11, wherein said predetermined current threshold Δ I in said start condition determination unitthThe value range of (a) is 0.1-1.0 times of the rated current of the generator.
16. The transient torque out-of-limit fast protection device for steam turbine generator unit as claimed in claim 11, wherein said predetermined active threshold Δ P in said start condition determination unitthThe value range of (a) is 0.1-1.0 times of the rated power of the generator.
17. The transient torque out-of-limit rapid protection device of the steam turbine generator unit as claimed in claim 11, wherein the value of T1 for the time of T1 in the starting condition determining unit is in the range of 0.5s to 10.0 s.
18. The transient torque out-of-limit rapid protection device of the steam turbine generator unit as claimed in claim 11, wherein the timing limit protection in the rotational speed difference fluctuation amplitude timing limit protection unit is specifically: setting one or more out-of-limit thresholds for fixed time limit protection, wherein each out-of-limit threshold corresponds to a delay fixed value, and when the fluctuation amplitude value delta omega of the rotation speed differenceampAnd when the time duration exceeds the delay fixed value corresponding to the out-of-limit threshold, judging that the fixed time limit protection meets the condition.
19. The transient torque out-of-limit fast protection device of the steam turbine generator unit as claimed in claim 11, wherein the inverse time limit protection in the inverse time limit protection unit for the fluctuation amplitude of the rotation speed difference is specifically:
two sets of constant values are set, (delta omega)th,min,Tth,max) And (Δ ω)th,max,Tth,min) Two coefficients are further calculated:
Figure FDA0002008122010000081
and h ═ Tth,min-K·Δωth,max(ii) a Wherein Δ ωth,minIs the minimum threshold of out-of-limit, Tth,maxIs the maximum delay constant, Δ ωth,maxIs the maximum threshold, T, of out-of-limitth,minIs the minimum delay timing value;
when the amplitude of fluctuation of the rotational speed difference is delta omegaampGreater than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure FDA0002008122010000082
the result is gradually increased, with a maximum limit of Accth,max，Accth,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t0Is Δ ωampGreater than Δ ωth,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };
when the fluctuation amplitude Delta of the rotation speed differenceωampLess than Δ ωth,minThen, the inverse time limit accumulated value Acc is calculated as follows:
Figure FDA0002008122010000083
the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t1Is Δ ωampLess than Δ ωth,minThe function max { } represents taking the maximum value of the calculation result in the brackets { };
after obtaining the calculation result, if the inverse time limit accumulated value Acc is greater than 100% and the duration exceeds Tth,minAnd judging that the timing time limit protection meets the conditions.
20. The transient torque out-of-limit fast protection device for the steam turbine generator unit as claimed in claim 12 or 14, wherein the data window duration T set in the moving data window peak detection method is related to the natural modal frequency of the torsional vibration of the steam turbine generator unit, and the value of T is 1/f 1.05-1.2 times of Tm,minWherein f ism,minIs the minimum torsional natural mode frequency.
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* Cited by examiner, † Cited by third party
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CN102185283A (en) * 2011-04-01 2011-09-14 南京南瑞继保电气有限公司 Method for sub-synchronous current calculation and sub-synchronous over-current and divergent protection of generator
CN105576607A (en) * 2016-03-10 2016-05-11 南京南瑞继保电气有限公司 Blocking filter detuning fault accelerated protection method and device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102185283A (en) * 2011-04-01 2011-09-14 南京南瑞继保电气有限公司 Method for sub-synchronous current calculation and sub-synchronous over-current and divergent protection of generator
CN105576607A (en) * 2016-03-10 2016-05-11 南京南瑞继保电气有限公司 Blocking filter detuning fault accelerated protection method and device

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