WO2016169301A1 - Protecting method and protecting device for shaft system torsional vibration of steam turbine generator unit - Google Patents

Abstract

A protecting method and protecting device for shaft system torsional vibration of a steam turbine generator unit. By acquiring a shaft system torsional vibration signal and applying a fatigue inverse time limit criterion (protection criterion I), a static instability criterion (protection criterion II) and a quick action criterion (protection criterion III) to determine the conditions of torsional vibration threatening the safety of a unit, protection trip and warning are performed, thereby avoiding greater damage of the torsional vibration to a shaft system of the generator unit. The protecting device for torsional vibration comprises a speed sensor, a pulsed quantity input module (PI), a main control module (CM), a digital quantity input module (DI), an analog quantity input module (AI), a digital quantity output module (DO) and a power supply module (POW). The speed sensor is connected to the pulsed quantity input module of the protecting device by means of a cable; and the protecting device externally communicates with a human-machine interface (HMI) of a main station via Ethernet.

Description

Turbogenerator shafting torsional vibration protection method and protection device Technical field

The invention belongs to the field of protection of subsynchronous oscillation of a steam turbine generator set and a nuclear power unit in a power system and a large power plant, and particularly relates to a shaft torsional vibration of a sub-Synchronous Oscillation (SSO) of a generator set. Protection method and protection device.

Background technique

In the prior art, the series capacitor compensation of the transmission line, the direct current transmission, the improper installation of the power system stabilizer, the excitation function of the generator excitation system, the thyristor control system, and the feedback function of the electro-hydraulic regulation system are all likely to be induced. Lead to secondary SSO phenomenon. The turbine and generator rotors have large inertia and are very sensitive to the low-order torsional modes of the shaft system itself, and are subjected to low-week and high-stress stress states. When electromechanical disturbance occurs, the balance between the turbine drive torque and the generator's electromagnetic brake torque is lost, and the torsional shear stress acting on the shaft system will also change, increasing the fatigue damage of the shaft material and reducing the service life. When the torsional stress is large enough, the unit shaft system will be damaged or broken, which will seriously affect the safe and reliable operation of the unit.

Turbogenerator shafting torsional vibration protection device realizes the protection of the unit shaft torsional vibration under SSO condition. In the existing shafting torsional vibration technology scheme, the patent "US 4,862,749 Shaft tortional vibration monitor for a multi-mass rotary system" and the patent "US 3,934,459 Torque monitoring system for rotating shaft" describe the unit shaft torsional vibration Monitoring programme, but did not cover protection options and criteria. And the patent "US 4,862,749 Shaft tortional vibration monitor for a multi-mass rotary system", the algorithm for estimating the torsional vibration response of the dangerous section position of the shafting is different from the present invention; the patent "US 3,934,459 Torque monitoring system for rotating shaft" The processing of the signal collected by the sensor: the normalized amplifier, the band pass filter bank, the buffer amplifier and the like are built by the analog device, and the device of the invention is a digital implementation mode, and the implementation and setting are more convenient.

Summary of the invention

In order to solve the above problems in the prior art, there are no clear protection criteria and a shafting torsional vibration monitoring scheme. The invention discloses a shafting torsional vibration protection device and a protection method for a sub-synchronous oscillation of a generator set. By measuring the angular velocity change of the machine end, the filter group is filtered and separated, and then the modal sampling value, amplitude and electric quantity are judged respectively, and the shafting fatigue condition and the subsynchronous modal change trend of the current running unit are obtained. The protection of the generator set is achieved by disconnecting the generator from the grid or destroying the conditions of the subsynchronous oscillation.

The present application specifically adopts the following technical solutions:

A method for protecting a shaft set torsional vibration of a generator set, characterized in that the method comprises the following steps:

(1) Collecting the angular velocity change of the shaft end of the generator set;

(2) Demodulating the instantaneous value of the angular velocity of each mode at the machine end by modal filtering of the PI module;

(3) obtaining the oscillation component of each torsional mode and the amplitude of each synchronous mode signal;

(4) Open the rapid criterion during the set time. When the torsional vibration of the generator set shaft meets the rapid criterion within the set time, an acceleration trip command is issued to protect the action exit; if within the set time When the generator shaft shaft twist does not satisfy the rapid criterion, Then close the quick criterion and proceed to step (5);

(5) According to the instantaneous value and amplitude of each synchronous modal signal obtained in step (3), real-time detection of whether the generator shaft torsional vibration meets the fatigue inverse time criterion, and the static instability criterion, when any When the criterion is given, the trip is protected and an alarm signal is issued.

The alarm signal includes a trend status signal and a fatigue status signal.

The invention still further preferably includes the following technical solutions:

In the step (1), the torsional vibration signals collected by the speed sensor are respectively set at the two ends of the genset shaft system, that is, the rotating sprocket on the high pressure cylinder side and the rotating sprocket on the excitation side, when a torsional vibration mode is used. When the vibration mode is easier to detect on the high pressure cylinder side, the sensor on the high pressure cylinder side is selected. When the vibration mode of a torsional vibration mode is easier to detect on the excitation side, the sensor on the excitation side is selected; when a torsional vibration is applied When the mode shape of the modal is close to the detection accuracy of the two positions, the sensor on the high pressure cylinder side is selected by default.

In step (4), the fast action criterion is implemented as follows:

4.1 Calculate the fatigue value of the generator shafting in a single calculation cycle according to the instantaneous value of the subsynchronous modal signal, and determine whether the fatigue value reaches the set rapid setting value;

4.2 When the cumulative mechanical fatigue of the shaft section dangerous section reaches the set cumulative fatigue setting during the opening period of the rapid criterion;

4.3 Judging whether the generator set has a phase failure or a three-phase short circuit fault according to the electrical quantity of the machine;

4.4 When the judgment conditions of 4.1, 4.2, and 4.3 are all satisfied, that is, when the fatigue value reaches the set rapid set value, and the accumulated mechanical fatigue reaches the set cumulative fatigue set value, and the generator set has phase-to-phase fault or three-phase Short-circuit fault, it is considered that the generator shaft torsional vibration meets the fast action criterion.

In step (5), the method for determining the fatigue inverse time criterion is:

5.1.1 analysis of the shafting structure to determine the location of the weak link;

5.1.2 Calculate the fatigue strength of the weak link by combining the material parameters and the influence coefficient;

5.1.3 According to the fatigue strength, the stress-life curve of the dangerous section position is obtained, that is, the SN curve; the weak link refers to all the journal positions and the coupling position in the shaft structure, and the dangerous section position is the weak link to be examined in the protection criterion. position.

5.1.4 According to the instantaneous value of each modal angular velocity change, the stress spectrum of the dangerous section position is obtained, and according to the fatigue damage accumulation theory, the cumulative value of the fatigue damage at the dangerous section position is obtained;

5.1.5 Whether the cumulative value of fatigue damage obtained under a single disturbance is greater than the set value, as the fatigue inverse time criterion;

The implementation method of the static instability criterion is:

5.2.1 Calculate the time series of each torsional mode amplitude in real time, and use the observation window of different lengths to calculate the relative change trend of the mode amplitude itself;

5.2.2 Determine whether there is divergence in the torsional mode according to the modal change trend over a period of time;

5.2.3 Perform real-time calculation according to the sampling values of each modal signal, and accumulate the fatigue damage caused by the torsional vibration signal to the shafting;

5.2.4 Determine whether the fatigue damage value of the dangerous section position is greater than the set value of the divergence fatigue;

5.2.5 If both 5.2.2 and 5.2.4 are satisfied at the same time, it is considered that the static instability criterion is satisfied.

The present application also discloses a genset shaft torsional vibration protection device using the aforementioned shafting torsional vibration protection method, including a speed sensor, a pulse quantity input module, a main control module, a digital input module, an analog input module, and a digital output. The module and the power module are characterized by:

There are two speed sensors, which are respectively installed at the rotating gear plate on the high pressure cylinder side and the rotating speed tooth plate on the excitation side of the two ends of the generator shaft system to collect the angular velocity change of the power generation group; the pulse input module receives The angular velocity variation collected by the speed sensor is processed by the digital filter bank to generate an instantaneous value and an effective value signal of the angular velocity variation of each mode, and input into the main control module;

The main control module judges the torsional vibration of the generator shaft based on the fatigue inverse time criterion, the static instability criterion, and the fast action criterion. When the fatigue inverse time criterion, the static instability criterion, and the fast action criterion are satisfied When the main control module issues a trip command through the digital output module;

The digital input module mainly collects the position signal of the field circuit breaker and the remote blocking signal, which is used as the application condition of the torsional vibration protection device of the generator set shaft shaft. The torque of the generator set shaft is torsion only when the circuit breaker is closed and there is no remote blocking signal. The protection device can be put into operation.

The analog input module collects the stator current and the stator voltage of the generator end, and is applied to the electrical quantity judgment required by the fast action criterion, and combined with the angular velocity variation collected by the speed sensor, together as the recording amount, assisting offline analysis.

The pulse quantity input module collects the angular velocity change signal of the machine end, the digital input module collects the circuit breaker position signal and the remote blocking signal, the analog input module collects the electric quantity signal of the generator end, and the collected signals are sent to the main control module as protection. The function realization and the conditions for the realization of the criterion are issued by the digital output module via the main control module criterion.

The turbo generator set shaft torsional vibration protection device is characterized in that the digital output module (DO) is used for outputting a trip signal and an alarm signal determined by a main control module (CM). The alarm signal includes a trend status signal, a fatigue status signal. The description of the signal is as follows:

1) Trend state signal status: When any signal in the trend state signal of all secondary synchronization modes is divergent, status is set to 1, and other conditions are set to 0;

2) Fatigue state signal-stage1: Calculated according to the sampled value of each modal signal. When there is no fatigue accumulation in the dangerous section position of the shafting, there is no risk of fatigue damage, but when the modal signal is greater than the normal operation setting value, stage1 is set to 1. Otherwise set to 0;

3) Fatigue state signal two stage2: Calculated according to the sampling value of each modal signal, when the fatigue accumulation of the dangerous section position of the shafting is obtained under a single disturbance, stage2 is set to 1, otherwise it is set to 0;

4) Fatigue state signal three stage3: Calculate according to the sampled value of each modal signal. When the single-disturbance is obtained, the fatigue accumulation of the dangerous section position of the shafting is obtained, and the fatigue cumulative value is greater than the set value of the fatigue damage risk of the unit. Otherwise set to 0.

The present invention obtains alarm and protection action signals by calculating the mechanical fatigue of the shafting of the generator set, analyzing the trend of the torsional vibration of the shafting, and judging the electric quantity. With the application of large-capacity steam turbine generator sets and long-distance large-capacity series compensation and direct current transmission technology, the occurrence of subsynchronous oscillation (SSO) in the unit and the power grid is becoming more and more serious. The signal trend of subsynchronous oscillation is the fundamental to solve the SSO problem; the subsynchronous torsional vibration protection device of the generator set is the key to protect the safe operation of power equipment such as generator sets. The device realizes the protection of the subsynchronous torsional vibration of the generator set, and has great significance for solving the problem of subsynchronous oscillation of the power plant and the power grid.

DRAWINGS

Figure 1 is a flow chart showing the method of shafting torsional vibration protection of a steam turbine generator set.

Figure 2 illustrates a flow chart of the judgment of the fast action criterion (protection criterion 3).

Fig. 3 is a flow chart showing the judgment of the fatigue inverse time criterion (protection criterion 1).

Figure 4 is a schematic diagram showing the wiring of the turbo-generator shafting torsional vibration protection device.

Figure 5 is a block diagram showing the structure of the turbo-generator shaft torsional vibration protection device.

Figure 6 is a diagram showing the mode shape of the torsional mode of the turbo-generator shafting.

Figure 7 is a diagram showing the mode shape of the torsional mode 2 of the turbine generator set shafting.

Figure 8 is a diagram showing the mode shape of the torsional mode 3 of the turbine generator set shafting.

Fig. 9 is a diagram showing the recording curve of the device when the No. 1 steam turbine generator set is protected according to the static instability criterion in the event of a fault.

Figure 10 is a diagram showing the recording curve of the device when the No. 2 steam turbine generator set is protected according to the fatigue inverse time limit criterion in the event of a fault.

detailed description

The invention will now be described in further detail with reference to the accompanying drawings and embodiments.

The invention provides a method for protecting a shaft set torsional vibration of a generator set, the method comprising the following steps, as shown in FIG. 1:

The angular velocity change of the generator shaft shaft is collected; the non-contact sensor is used to sense the pulse signal generated by the gear rotating with the shaft. A pulse signal is generated as each tooth passes the sensor. When the rotor is rotated at a constant speed, the position of the pulse train reflects the position of each tooth on the circumference of the gear. The sensor outputs a uniform pulse wave. When the rotor is vibrating, the position of each pulse changes, the vibration causes the pulse signal to phase shift, and the output is a dense and phase pulse wave. Extracting this phase shift, you get a set of samples of vibration,

When the rotor undergoes a simple harmonic torsion vibration at a single frequency, the angular displacement of a section is:

υ(t)=A sin(ω _t t+θ)

Where ω _t is the vibration angular frequency, and A and θ are the amplitude and initial phase at the cross section.

If the rotor is operated at a steady speed, when it is subjected to a periodic excitation torque, the torsional vibration of the rotor contains harmonic components of different frequencies and amplitudes.

The angular velocity of the rotational motion of the shaft is the superposition of the average angular velocity of the shaft and the angular velocity of the torsional vibration:

Then the angular velocity of the machine

Where ω _k , A _k , θ _k represent the corresponding parameters of the Kth vibration component, respectively. The end angular velocity change amount Δω includes vibration components of a plurality of frequencies. Through the modulo filtering of the PI module, the instantaneous value of the angular velocity change of each mode end is demodulated;

For multi-modal SSO, a modal filter bank is used to separate each torsional mode information from the Δω signal, where the modal filter The group includes a low-pass filter, a high-pass filter, and a band-pass filter to separate the respective torsional modes information, and then implement independent mode control.

The modal states demodulated by the angular velocity variation of the machine end are expressed as

Δω _k =A _k sin(ω _k t+θ _k )(k=1,2,...n)

Obtaining an oscillating component of each torsional mode and an amplitude of each synchronous modal signal;

The pulse quantity input module (PI) samples each modal component demodulated by the angular velocity variation of the machine end, obtains the sampling value of each synchronous modal signal, and calculates the amplitude thereof, which is represented by DWi, which is called the ith. The amplitude of the angular velocity variation component of the machine end, where i = 1, 2, 3, ..., n.

Determine whether the fast criterion is met, as shown in Figure 2;

When any of the torsional modes exceeds the torsional protection start setting, the fast action criterion is opened. During the fast action criterion:

4.1 Calculate the fatigue value of the generator shafting in a single calculation cycle according to the instantaneous value of the subsynchronous modal signal, and determine whether the fatigue value reaches the set rapid setting value;

4.2 Judging that the cumulative mechanical fatigue of the shaft section dangerous section reaches the set cumulative fatigue setting value during the opening period of the rapid criterion;

4.3 Judging whether the generator set has a phase failure or a three-phase short circuit fault according to the electrical quantity of the machine;

When the judgment conditions of 4.1, 4.2, and 4.3 are all satisfied, that is, when the fatigue value reaches the set rapid set value, and the accumulated mechanical fatigue reaches the set cumulative fatigue set value, and the generator set has an interphase fault or a three-phase short circuit. Fault, think that the generator shaft torsional vibration meets the fast action criterion.

Determine whether the inverse time limit criterion is met, as shown in Figure 3;

5.1 Finite element analysis of the shafting structure to determine the location of the weak link;

5.2 Combine the material parameters and the influence coefficient, and combine the nominal stress method with the local strain method to calculate the fatigue strength of the weak link;

5.3 According to the fatigue strength of the weak link, the stress-life curve, ie the S-N curve, is obtained from the dangerous section position. The weak link refers to all the journal positions and the position of the coupling in the shaft structure, and the position of the dangerous section is the position of the weak link to be examined in the protection criterion. For example, the weak link between the high and medium pressure cylinder (HIP) and the low pressure cylinder 1 (LP1) is the #2 journal position and the #3 journal position. The fatigue strength can be calculated by the SN curve ratio of the #2 journal position. # The SN curve of the journal position is lower, then the position of the dangerous section of the 2# journal position is selected as the protection criterion.

5.4 According to the measured angular velocity of the machine end, the stress spectrum of the dangerous section position is obtained. According to the fatigue damage accumulation theory, the cumulative value of the fatigue damage at the dangerous section position is obtained.

5.5 Whether the cumulative value of fatigue damage obtained under a single disturbance is greater than the set value is used as the fatigue inverse time criterion. When the accumulated fatigue damage value obtained under a single disturbance is greater than the fatigue inverse time criterion fatigue damage set value, the protection device operates.

Determine whether the static instability criterion is met, as shown in Figure 4;

6.1 Real-time calculation of the time series of each torsional mode amplitude, using different length observation windows to calculate the relative change trend of the mode amplitude itself;

6.2 Judging whether there is divergence in the torsional mode according to the modal change trend over a period of time;

6.3 Calculate the real-time calculation according to the sampling values of each modal signal, and accumulate the fatigue damage caused by the torsional vibration signal to the shafting;

6.4 Determine whether the fatigue damage value of the dangerous section position is greater than the divergent fatigue set value;

6.5 If 6.2 and 6.4 are satisfied at the same time, it is considered that the static instability criterion is satisfied.

The block diagram of the device structure of the present invention is shown in FIG. 5. The device includes a speed sensor, a pulse amount input module, a main control module, a digital input module, an analog input module, a digital output module, and a power module.

The speed sensor is installed at the rotating gear plate on the high-pressure cylinder side of the genset shaft system and the rotating gear plate on the excitation side to collect the angular velocity change of the power generation group; the pulse input module receives the angular velocity collected by the speed sensor The amount of change, through the processing of the digital filter bank, generates the instantaneous value and the effective value signal of the angular velocity variation of each mode; the digital input module mainly collects the position signal of the circuit breaker and the remote blocking signal, which is used as the shafting system of the generator set. The application condition of the torsional vibration protection device can only be put into operation when the circuit breaker is closed and there is no remote blocking signal; the analog input module collects the stator current and the stator voltage of the generator end, and is applied to The electrical quantity judgment required for the fast action criterion is combined with the angular velocity variation collected by the speed sensor, and used together as the recording amount to assist in off-line analysis. The pulse quantity input module collects the angular velocity change signal of the machine end, the digital input module collects the circuit breaker position signal and the remote blocking signal, the analog input module collects the electric quantity signal of the generator end, and the collected signals are sent to the main control module as protection. Functional realization and criteria for achieving the criteria. The main control module judges the torsional vibration of the generator shaft based on the fatigue inverse time criterion, the static instability criterion, and the fast action criterion. When the fatigue inverse time criterion, the static instability criterion, and the fast action criterion are satisfied The master module issues a trip command via the digital output module.

The working process of the device is as follows: the rotational speed sensor collects the angular velocity change of the machine end, and the instantaneous value of the angular velocity change of each mode end is demodulated by the modal filter of the PI module, and the oscillation component of each torsional vibration mode is obtained, and each time is obtained. The amplitude of the synchronous modal signal. According to the amplitude of each synchronous modal signal, the occurrence of torsional vibration is judged; the shafting fatigue is calculated according to the sampling value of each synchronous modal signal, and the calculated fatigue value is obtained to obtain the tripping action signal, which is the fatigue inverse time criterion. (Protection criterion 1). The amplitudes of the modal speed signals are analyzed and processed separately. The relative change trend of the modal amplitude is calculated by using the observation window of different lengths. The torsional vibration mode divergence is determined and the trip command is issued to disconnect the generator set from the grid. Instability criterion (protection criterion 2). After the torsional vibration occurs, the fast criterion is opened, and the fast criterion is the open duration T; the phase T is used to judge the phase or three-phase fault of the terminal or the line; the calculation of the duration T is the fatigue accumulation of the shaft system and the shaft fatigue in a single calculation period The value reaches a rapid setting; the judgment of the action signal is a fast action criterion (protection criterion 3).

The application of the torsional vibration signal acquired by the two speed sensors is related to the torsional vibration mode of the turbo generator shaft system. As shown in Figure 6, Figure 7, and Figure 8. It can be seen from the vibration mode curve that for the modal one and the modal two, the torque amplitudes measured by the sensors installed on the turbine side and the exciter side can be similar, and the torsional vibration signals collected by the two speed sensors can be selected. It is applied to the torsional vibration protection device. For the modal three, the sensor on the turbine side is more likely to measure the torsional vibration signal, while the sensor on the excitation side has a small amplitude and low precision, which cannot be selected for the torsional vibration protection device.

For the specific implementation of implementing the protection criteria in the main control module CM, refer to the following embodiments:

A single-phase fault occurred in one line of a power plant outlet, the power plant side protection device was successfully closed, the substation side protection did not coincide, and the three phases were jumped. The turbo-generator shafting torsional vibration protection device is equipped with fatigue anti-time limit criterion (protection criterion 1), static instability criterion (protection criterion 2), and exits the fast action criterion (protection criterion 3).

XXXX year XX XX day 20:17:02 376 milliseconds #1 unit torsional vibration protection device protection action cut #1 unit.

#1 machine steam turbine generator shaft shaft torsional vibration protection device protection start-up time: protection start (XXXX-XX-XX 20:16:59:204);

#1 machine steam turbine generator shaft shaft torsional vibration protection device status set time: trend status status set (XXXX-XX-XX20:17:02:317);

#1 machine steam turbine generator shaft shaft torsional vibration protection device protection action time: protection exit action (XXXX-XX-XX 20:17:02:317);

The time from protection start to action exit is: 3 seconds and 115 milliseconds.

In the case of failure, the #1 unit modal 2 first converges slowly and then slowly diverge, and the #1 unit static instability criterion (protection criterion 2) acts.

#2机汽轮发电机组轴系Torque vibration protection device protection start-up time: protection start (XXXX-XX-XX 20:16:59:209);

#2机 Steam turbine generator shaft shaft torsional vibration protection device protection event: the accumulated fatigue value is greater than the set value (XXXX-XX-XX 20:17:05:214);

#2机汽轮发电机组Shaft torsional vibration protection device protection action time: protection exit action (XXXX-XX-XX 20:17:05:214);

The time from protection start to action exit is: 5 seconds 995 milliseconds.

In the case of failure, the #2 unit fatigue inverse time criterion (protection criterion 1) action.

The cumulative fatigue values of the #1 and #2 units caused by this failure are listed in the following table:

The total cumulative value of the dangerous section fatigue of #1##2 unit in the whole process is as follows:

For the #1 unit, the time from protection start to action exit was: 3115 milliseconds, during which the fatigue damage at the 2 watt journal position was 0.87%, and the fatigue damage at the 2 watt journal position at the end of the entire fault process was 1.42%. The #1 unit modal two-mode frequency is 26 Hz. For this condition, if the fast action criterion (protection criterion 3) is applied:

1) #1 machine protection start, protection start absolute time: XXXX-XX-XX 20:16:59:204;

2) Open the fast action criterion within a short time T (800ms) after the torsional vibration protection is activated;

3) The single operation cycle of the main control module CM is 50ms;

4) The number of modal two cycles in time T (800ms) is 800/50=16;

5) Calculate the shafting fatigue value in a single calculation cycle (50ms) within the time T (800ms) when the fast action criterion is open;

6) The case where the fatigue value of the 2# journal position exceeds the fixed value (0.01%) in a single calculation cycle (50 ms) within the time T (800 ms);

7) The accumulated value of the shafting fatigue reaches the set value (0.1%) within the time T (800ms) when the fast action criterion is open;

8) Identify the phase three-phase short-circuit fault time by the terminal electrical quantity within the time T (800ms) when the fast action criterion is open. 690ms after the start of #1 unit protection;

#1 unit protection 690ms after start-up, rapid criterion action, at this time #1 unit 2 watt journal position fatigue damage is 0.19%, far less than the static instability criterion (protection criterion 2) fatigue damage 0.87% . After the #1 unit is cut, the mode 2 gradually converges and continues to accumulate fatigue in the shafting system. The fatigue damage at the 2 watt journal position at the end of the entire fault process is 0.79%, which is much smaller than the 2 watt journal position at the end of the entire fault process. Fatigue damage was 1.42%.

For the #2 unit, the time from protection start to action exit is: 5995 ms, during which the fatigue damage at the 2 watt journal position is 1.05%, and the fatigue damage at the 2 watt journal position at the end of the entire fault process is 2.36%. The #2 unit modal two-mode frequency is 26 Hz. For this condition, if the fast action criterion (protection criterion 3) is applied:

1) #2 machine protection start, protection start absolute time: XXXX-XX-XX 20:16:59:209;

2) Open the fast action criterion within a short time T (800ms) after the torsional vibration protection is activated;

3) The single operation cycle of the main control module CM is 50ms;

4) The number of modal two cycles in time T (800ms) is 800/50=16;

5) Calculate the shafting fatigue value in a single calculation cycle (50ms) within the time T (800ms) when the fast action criterion is open;

6) The case where the fatigue value of the 2# journal position exceeds the fixed value (0.01%) in a single calculation cycle (50 ms) within the time T (800 ms);

7) The accumulated value of the shafting fatigue reaches the set value (0.1%) within the time T (800ms) when the fast action criterion is open;

8) Within the time T (800ms) when the fast action criterion is open, the phase three-phase short-circuit fault time is recognized as the #1 unit protection start time after the start-up of the #1 unit protection; 690ms after the #2 unit protection start, the fast criterion action At this time, the fatigue damage of the 2 watt journal position of the #2 unit is 0.12%, which is much less than the fatigue damage of 1.05% when the action is based on the fatigue inverse time criterion (protection criterion 1). If the #1 unit operates according to the rapid criterion, the #2 unit's mode 2 gradually converges after the #1 unit is cut, although the cumulative fatigue of the shaft system continues, the fatigue damage to the 2 watt journal position at the end of the entire failure process is 1.55%. , far less than 2.36% of the fatigue damage according to the original criterion to the 2 watt journal position at the end of the entire fault process.

It can be seen from the above embodiments that the turbo-generator shaft torsion vibration protection device is put into application fatigue counter-time criterion (protection criterion 1), static instability criterion (protection criterion 2), fast action criterion (protection criterion) 3) It can comprehensively judge the situation that the sub-synchronous oscillation poses a threat to the safety of the unit, and perform the protection trip and alarm function to avoid the torsional vibration causing greater damage to the shaft set of the generator set.

Claims (6)

1. A method for protecting a shaft set torsional vibration of a generator set, characterized in that the method comprises the following steps:

   (1) Collecting the angular velocity change of the shaft end of the generator set;

   (2) Demodulating the instantaneous value of the angular velocity of each mode at the machine end by modal filtering of the PI module;

   (3) obtaining the oscillation component of each torsional mode and the amplitude of each synchronous mode signal;

   (4) Open the rapid criterion during the set time. When the torsional vibration of the generator set shaft meets the rapid criterion within the set time, an acceleration trip command is issued to protect the action exit; if within the set time When the generator shaft shaft twist does not satisfy the rapid criterion, the fast criterion is closed, and the step (5) is entered;

   (5) According to the instantaneous value and amplitude of the subsynchronous modal signal obtained in step (3), real-time detection of whether the generator shaft torsional vibration satisfies the fatigue inverse time criterion and the static instability criterion, when any judgment is satisfied According to the time, the trip is protected and an alarm signal is issued.
2. The shafting torsional vibration protection method according to claim 1, wherein:

   In step (1), a speed sensor is provided at both ends of the genset shaft system, that is, at the speed sprocket on the high pressure cylinder side and at the speed sprocket on the excitation side, and a torsional vibration signal is collected, when a torsional mode is used. When the vibration mode is easier to detect on the high pressure cylinder side, select the sensor on the high pressure cylinder side; when the vibration mode of a torsional vibration mode is easier to detect on the excitation side, select the sensor on the excitation side; when a torsional vibration mode When the vibration mode of the state is similar when the detection accuracy of the two positions is similar, the sensor on the high pressure cylinder side is selected by default.
3. The shafting torsional vibration protection method according to claim 1, wherein:

   In step (4), the fast action criterion is implemented as follows:

   4.1 Calculate the fatigue value of the generator shafting in a single calculation cycle according to the instantaneous value of the subsynchronous modal signal, and determine whether the fatigue value reaches the set rapid setting value;

   4.2 When the cumulative mechanical fatigue of the shaft section dangerous section reaches the set cumulative fatigue setting during the opening period of the rapid criterion;

   4.3 Judging whether the generator set has a phase failure or a three-phase short circuit fault according to the electrical quantity of the machine;

   4.4 When the judgment conditions of step 4.1, step 4.2 and step 4.3 are satisfied, that is, when the fatigue value reaches the set rapid setting value, and the accumulated mechanical fatigue reaches the set cumulative fatigue setting value, and the phase difference occurs in the generator set Or three-phase short-circuit fault, it is considered that the generator shaft torsional vibration meets the fast action criterion.
4. The shafting torsional vibration protection method according to claim 1, wherein:

   In step (5), the method for determining the fatigue inverse time criterion is:

   5.1.1 analysis of the shafting structure to determine the location of the weak link;

   5.1.2 Calculate the fatigue strength of the weak link by combining the material parameters and the influence coefficient;

   5.1.3 According to the fatigue strength, the stress-life curve of the dangerous section position is obtained, that is, the SN curve. The weak link refers to all the journal positions and the coupling position in the shaft structure, and the dangerous section position is the weak link to be considered in the protection criterion. position;

   5.1.4 According to the instantaneous value of each modal angular velocity change, the stress spectrum of the dangerous section position is obtained, and according to the fatigue damage accumulation theory, the cumulative value of the fatigue damage at the dangerous section position is obtained;

   5.1.5 Whether the cumulative value of fatigue damage obtained under a single disturbance is greater than the set value, as the fatigue inverse time criterion;

   The implementation method of the static instability criterion is:

   5.2.1 Calculate the time series of each torsional mode amplitude in real time, and use the observation window of different lengths to calculate the relative change trend of the mode amplitude itself;

   5.2.2 Determine whether there is divergence in the torsional mode according to the modal change trend over a period of time;

   5.2.3 Perform real-time calculation according to the sampling values of each modal signal, and accumulate the fatigue damage caused by the torsional vibration signal to the shafting;

   5.2.4 Determine whether the fatigue damage value of the dangerous section position is greater than the set value of the divergence fatigue;

   5.2.5 If step 5.2.2 and step 5.2.4 are satisfied at the same time, it is considered that the static instability criterion is satisfied.
5. The method according to claim 1, wherein the alarm signal comprises a trend state signal and a fatigue state signal.
6. A generator shaft shaft torsional vibration protection device using the shafting torsional vibration protection method according to any one of claims 1-5, comprising a speed sensor, a pulse quantity input module, a main control module, a digital input module, and an analog input module , a digital output module and a power module, characterized by:

   There are two speed sensors, which are respectively installed at the rotating gear plate on the high pressure cylinder side and the rotating speed tooth plate on the excitation side of the two ends of the generator shaft system to collect the angular velocity change of the power generation group; the pulse input module receives The angular velocity variation collected by the speed sensor is processed by the digital filter bank to generate an instantaneous value and an effective value signal of the angular velocity variation of each mode, and input into the main control module;

   The main control module judges the torsional vibration of the generator shaft based on the fatigue inverse time criterion, the static instability criterion, and the fast action criterion. When the fatigue inverse time criterion, the static instability criterion, and the fast action criterion are satisfied When the main control module issues a trip command through the digital output module;

   The digital input module mainly collects the position signal of the field circuit breaker and the remote blocking signal, which is used as the application condition of the torsional vibration protection device of the generator set shaft shaft. The torque of the generator set shaft is torsion only when the circuit breaker is closed and there is no remote blocking signal. The protection device can be put into operation;

   The analog input module collects the stator current and the stator voltage of the generator end, and is applied to the electrical quantity judgment required by the fast action criterion, and combined with the angular velocity variation collected by the speed sensor, together as the recording amount, assisting offline analysis;

   The pulse quantity input module collects the angular velocity change signal of the machine end, the digital input module collects the circuit breaker position signal and the remote blocking signal, the analog input module collects the electric quantity signal of the generator end, and the collected signals are sent to the main control module as protection. The function realization and the conditions for the realization of the criterion are issued by the digital output module via the main control module criterion.

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