阅读说明：本技术 汽轮发电机组暂态扭矩越限快速保护方法及装置 (Transient torque out-of-limit rapid protection method and device for steam turbine generator unit ) 是由 张琦雪 马志恒 王凯 肖鹏 赵锦忠 王新宝 王光 陈俊 于 2019-03-27 设计创作，主要内容包括：本发明公开了一种汽轮发电机组暂态扭矩越限快速保护方法及装置,保护装置通过短延时滤波及移动数据窗峰值检测法测量大轴的转速差波动幅值Δω<Sub>amp</Sub>,同时保护装置检测机端电流工频变化量幅值ΔI<Sub>amp</Sub>、暂态电磁有功功率波动分量的幅值ΔP<Sub>amp</Sub>；当ΔI<Sub>amp</Sub>或ΔP<Sub>amp</Sub>越限时保护启动并保持T1时间；保护启动后,进行转速差波动幅值Δω<Sub>amp</Sub>的定时限和反时限保护判别；转速测量通道自检异常,或者检测到发电机没有并网时,保护闭锁；当定时限或反时限保护动作,且没有保护闭锁时,保护动作出口解列发电机。本发明兼顾了快速性和可靠性,易于实现。(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 unit amp And meanwhile, the protection device detects the machine end current power frequency variation amplitude Delta I amp Amplitude delta P of transient electromagnetic active power fluctuation component amp (ii) a When Δ I amp Or Δ P amp The 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 out amp Judging 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.)

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 unit_amp；

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 generator_amp；

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 unit_amp；

And (4): judging the starting condition: when the Δ I_ampExceeding a predetermined current threshold Δ I_thOr said Δ P_ampExceeds a preset active power threshold value delta P_thWhen 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 out_ampWhen 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 out_ampWhen 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) is_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): subtracting the rated speed signal omega from the actually measured speed signal omega_nTo obtain the original rotation speed difference signal delta omega ═ omega-omega_n；

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 window_maxAnd minimum value Δ ω_min：

Where T is the current time, T is the set data window duration, a functionIs referred to as the difference in rotational speed Δ ωMaximum value in the time range from (T-T) to T, functionMeans 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 difference_amp＝(Δω_max-Δω_min)/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 generator_a、i_b、i_c；

Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formula_a、Δi_b、Δi_c：

Δi_j(t)＝i_j(t)-i_j(t-T_1st) j is a, b, c formula 4

Where T is the current time, T_1stThe 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 method_a、Δi_b、Δi_cRespectively, of Δ I_a,amp、ΔI_b,amp、ΔI_c,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta I_ampI.e. by

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) is_ampBy 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 generator_a、i_b、i_cInstantaneous value u of three-phase voltage at measuring machine end_a、u_b、u_c；

Step (3.2): calculating the transient electromagnetic active power p ═ u_ai_a+u_bi_b+u_ci_c；

Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection method_maxAnd a minimum value p_min：

Where T is the current time, T is the set data window duration, a functionRefers to the maximum 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 power_amp＝(p_max-p_min)/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 difference_ampAnd 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,T_th,max) And (Δ ω)_th,max,T_th,min) Two coefficients are further calculated:

step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omega_ampGreater than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually increased, with a maximum limit of Acc_th,max，Acc_th,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t₀Is Δ ω_ampGreater than Δ ω_th,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 omega_ampLess than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t₁Is Δ ω_ampLess than Δ ω_th,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 T_th,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 times_m,minWherein f is_m,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 unit_amp；

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 unit_amp；

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 unit_amp；

A start condition determination unit: for judging when the Δ I is_ampExceeding a predetermined current threshold Δ I_thOr said Δ P_ampExceeds a preset active power threshold value delta P_thWhen 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 1_ampWhen 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 1_ampWhen 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 omega_nTo obtain the original rotation speed difference signal delta omega ═ omega-omega_n；

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 method_maxAnd minimum value Δ ω_min：

Where T is the current time, T is the set data window duration, a functionIs the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function

a rotation speed difference fluctuation amplitude value operator unit for calculating the rotation speed difference fluctuation amplitude value delta omega_amp＝(Δω_max-Δω_min)/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 formula_a、Δi_b、Δi_c：

Δi_j(t)＝i_j(t)-i_j(t-T_1st) j is a, b, c formula 4

Where T is the current time, T_1stThe 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 calculation_a、Δi_b、Δi_cRespectively, of Δ I_a,amp、ΔI_b,amp、ΔI_c,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta I_ampI.e. by

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 ═ u_ai_a+u_bi_b+u_ci_c；

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 p_maxAnd a minimum value p_min：

Where T is the current time, T is the set data window duration, a functionRefers to the maximum value of p in the time range from time (T-T) to time TRefers 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 power_amp＝(p_max-p_min)/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 unit_thThe 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 unit_thThe 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 difference_ampAnd 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,T_th,max) And (Δ ω)_th,max,T_th,min) Two coefficients are further calculated:and h ═ T_th,min-K·Δω_th,max(ii) a Wherein Δ ω_th,minIs the minimum threshold of out-of-limit, T_th,maxIs the maximum delay constant, Δ ω_th,maxIs the maximum threshold, T, of out-of-limit_th,minIs the minimum delay timing value;

when the amplitude of fluctuation of the rotational speed difference is delta omega_ampGreater than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually increased, with a maximum limit of Acc_th,max，Acc_th,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t₀Is Δ ω_ampGreater than Δ ω_th,minThe function min { } represents taking the minimum value of the calculation result in the brackets { };

when the fluctuation amplitude Delta of the rotation speed differenceω_ampLess than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t₁Is Δ ω_ampLess than Δ ω_th,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 T_th,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 T_m,minWherein f is_m,minIs the minimum torsional natural mode frequency.

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.

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 unit_amp；

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 generator_amp；

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 unit_amp；

And (4): judging the starting condition: when the Δ I_ampExceeding a predetermined current threshold Δ I_thOr said Δ P_ampExceeds a preset active power threshold value delta P_thWhen 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 out_ampWhen 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 out_ampWhen 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 omega_nTo obtain the original rotation speed difference signal delta omega ═ omega-omega_n；

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 window_maxAnd minimum value Δ ω_min：

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 times_m,minWherein f is_m,minThe minimum torsional natural mode frequency; function(s)

Is the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function

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 difference_amp＝(Δω_max-Δω_min)/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 end_a、i_b、i_c；

Step (2.2): calculating the power frequency variation instantaneous value delta i of the three-phase current according to the following formula_a、Δi_b、Δi_c：

Δi_j(t)＝i_j(t)-i_j(t-T_1st) j is a, b, c formula 4

Where T is the current time, T_1stThe 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 method_a、Δi_b、Δi_cRespectively, of Δ I_a,amp、ΔI_b,amp、ΔI_c,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta I_ampI.e. by

Further, the amplitude Δ P of the wave component in the transient electromagnetic active power in the step (3) is_ampThe following steps are taken for calculation:

step (3.1): measuring instantaneous value i of three-phase current at turbine end of steam turbine generator_a、i_b、i_cInstantaneous value u of three-phase voltage at measuring machine end_a、u_b、u_c；

Step (3.2): calculating the transient electromagnetic active power p ═ u_ai_a+u_bi_b+u_ci_c；

Step (3.3): calculating the maximum value p of p by adopting a moving data window peak value detection method_maxAnd a minimum value p_min：

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 times_m,minWherein f is_m,minThe minimum torsional natural mode frequency; function(s)

Refers to the maximum value of p in the time range from time (T-T) to time TRefers 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 power_amp＝(p_max-p_min)/2。

Further, in the step (4), the current threshold Δ I is preset_thThe value range of (1) is 0.1-1.0 times of rated current of the generator, and an active threshold value delta P is preset_thThe 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 difference_ampAnd 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,T_th,max) And (Δ ω)_th,max,T_th,min) Two coefficients are further calculated:and h ═ T_th,min-K·Δω_th,max(ii) a Wherein Δ ω_th,minIs the minimum threshold of out-of-limit, T_th,maxIs the maximum delay constant, Δ ω_th,maxIs the maximum threshold, T, of out-of-limit_th,minIs the minimum delay timing value;

step (7.2): when the amplitude of fluctuation of the rotational speed difference is delta omega_ampGreater than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually increased, with a maximum limit of Acc_th,max，Acc_th,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 ω_ampGreater than Δ ω_th,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 omega_ampLess than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t₁Is Δ ω_ampLess than Δ ω_th,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 T_th,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 shaft_amp；

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 unit_amp；

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 unit_amp；

A start condition determination unit: for judging when the Δ I is_ampExceeding a predetermined current threshold Δ I_thOr said Δ P_ampExceeds a preset active power threshold value delta P_thWhen 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 1_ampWhen 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 1_ampWhen 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 omega_nTo obtain the original rotation speed difference signal delta omega ═ omega-omega_n；

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 method_maxAnd minimum value Δ ω_min：

Where T is the current time, T is the set data window duration, a functionIs the maximum value of the difference in rotational speed Δ ω in the time range from time (T-T) to time T, function

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 omega_amp＝(Δω_max-Δω_min)/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 formula_a、Δi_b、Δi_c：

Δi_j(t)＝i_j(t)-i_j(t-T_1st) j is a, b, c formula 4

Where T is the current time, T_1stThe 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 calculation_a、Δi_b、Δi_cRespectively, of Δ I_a,amp、ΔI_b,amp、ΔI_c,ampTaking the maximum value of the three values as the machine end current power frequency variation amplitude Delta I_ampI.e. by

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 ═ u_ai_a+u_bi_b+u_ci_c；

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 method_maxAnd a minimum value p_min：

Where T is the current time and T isSet duration of data window, function

Refers to the maximum value of p in the time range from time (T-T) to time TRefers 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 power_amp＝(p_max-p_min)/2。

Further, the preset current threshold Δ I in the starting condition determination unit_thThe 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 unit_thThe 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 difference_ampAnd 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,T_th,max) And (Δ ω)_th,max,T_th,min) Two coefficients are further calculated:

and h ═ T_th,min-K·Δω_th,max(ii) a Wherein Δ ω_th,minIs the minimum threshold of out-of-limit, T_th,maxIs the maximum delay constant, Δ ω_th,maxIs the maximum threshold, T, of out-of-limit_th,minIs the minimum delay timing value;

when the amplitude of fluctuation of the rotational speed difference is delta omega_ampGreater than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually increased, with a maximum limit of Acc_th,max，Acc_th,maxAccumulating an upper limit value for the inverse time limit; in equation 7, t is the current time, t₀Is Δ ω_ampGreater than Δ ω_th,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 omega_ampLess than Δ ω_th,minThen, the inverse time limit accumulated value Acc is calculated as follows:

the result is gradually reduced, and the minimum is limited to 0%; where t is the current time, t₁Is Δ ω_ampLess than Δ ω_th,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 T_th,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 times_m,minWherein f is_m,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.