KR20090058633A - Method for secure double holding of control rod drive mechanism and apparatus thereof - Google Patents

Abstract

A method for secure double holding of a control rod drive mechanism and an apparatus thereof are provided to prevent damage due to friction force between instruments in moving a control rod driving unit. A double hold unit(19) comprises a signal processing unit(17), an A/D converter(18) and a central processing unit(20). The signal processing unit adjusts a low pass filtering scale of an inputted coil current before or after the expected time that the mover is separated from the stator. The A/D converter converts analog signals passing through the signal processing unit into a digital signal, and the central processing unit performs a wavelet transform of the digital signal from the A/D converter, and the central processing unit obtains the wavelet transform coefficient. The central processing unit determines whether the mover is separated from the stator or not based on wavelet transform coefficient. The central processing unit generates a double holding control signal according to the result.

Description

Method for secure double holding of control rod drive mechanism and apparatus

The present invention relates to a reactor control rod drive device, and more particularly, to a method and apparatus for stably performing a maintenance operation when an abnormality occurs in a reactor control rod drive device or a control rod control system.

Patents related to the recognition of the mechanism operation occurrence of the reactor control rod driving apparatus include a patent number 10-0484018-0000 and a patent number 10-0655119-0000. These inventions focus on changing the coil current waveform by the mechanisms of the control rod drive device in the form of electromagnetic jacks acting on the electromagnetic force of the coil excitation. The inductance is calculated and the distance between the mover of the control rod drive and the stator is used to determine the mechanism operation of the control rod drive. The latter detects the local distortion of the coil current waveform by the wavelet transform technique to determine the mechanism operation. .

The present invention has been invented to solve the above problems, and in the control rod drive device, the method of safe dual holding of the reactor control rod drive device to prevent the damage caused by friction between the mechanisms during the double holding operation to achieve a safe double holding and The object is to provide a device.

In order to achieve the above object, the stable dual maintenance method of the reactor control rod drive device according to the present invention (i) is to determine the current of the coil sensed by the reactor control rod drive input before and after the expected time of separation of the lifting armature from the lifting pole Obtaining a plurality of coil current data based on the; (ii) wavelet transforming the plurality of coil current data to obtain a wavelet transform coefficient; (iii) comparing the wavelet transform coefficients with a threshold; (iv) determining whether the raising armature is separated from the raising stimulus according to a comparison result of the wavelet transform coefficients and the threshold; And (v) performing a dual holding operation according to the determination result of step (iv).

Preferably, the start time of the dual holding operation is determined according to whether the raising armature is separated from the raising stimulus. More preferably, if the wavelet transform coefficient is greater than the threshold, the raising armature is determined to be separated from the raising stimulus and step (v) is performed, and if the wavelet transform coefficient is less than the threshold, the raising armature After determining that it is not separated from the raising stimulus and indicating that an abnormality has occurred on the raising side, step (v) is performed.

According to another aspect of the present invention, a stable dual holding device of a reactor control rod driving apparatus includes a signal processor configured to perform a low frequency filtering scale adjustment process of a coil sensed by a reactor control rod driving apparatus input before and after an expected time point of separation of a raising armature from a raising stimulus. ; An analog-digital converter for converting the analog signals passed through the signal processing unit into digital signals; And wavelet transforming the digital signal from the analog-to-digital converter to obtain wavelet transform coefficients, and determining whether the raising armature has been separated according to the wavelet transform coefficients, and generating a dual holding operation control signal according to the determination result. And a central processing unit.

The present invention has proposed a method for more safely performing the double holding operation that is performed when an abnormality occurs in the reactor control rod drive system or the control rod control system. If the driving shaft or the tongs of the control rod drive mechanisms are moved while the double holding operation is carried out, there is a risk of breakage due to mechanical friction between the drive shaft and the tongs or, in the worst case, the drop of the control rods. Therefore, in order to minimize the friction between the forceps and the drive shaft during the double holding operation, it is safer that the double holding operation is performed after the lifting armature that determines the movement of the drive shaft and the moving forceps has completely completed the movement. To confirm that the raising armature is completely separated from the raising stimulus, the raising coil current waveform change is analyzed because the coil current change is a function of the distance between the armature and the stimulus. Wavelet transform with excellent removal capability was used. In this way, a safer dual hold operation can be implemented by analyzing the change of the coil up current waveform using wavelet transform and setting the start point of the double hold operation immediately after the lifting armature confirms the completion of separation from the raise stimulus.

Figure 1 shows in detail the structure of the control rod drive device (6). Among the mechanisms of the control rod drive device 6, the main parts for which motion detection is required in the present invention are the lifting poles 10 and 33 and the lifting armatures 11 and 35. When the stop forceps coils 9 and 30 are excited, the stop forceps armature 42 is attached to the stop forceps 39, and the stop forceps 13 and 43 bite the grooves of the drive shafts 14 and 32, and the mobile forceps coil When (8, 28) is excited, the mobile tongs armature 38 is attached to the lifting armatures 11 and 35, and the mobile tongs 12 and 37 bite the grooves of the drive shafts 14 and 32. When the lifting coils 7 and 26 are excited, the lifting armatures 11 and 35 are attached to the lifting poles 10 and 33 and the moving tong armature 38 connected to the lifting armatures 11 and 35 moves to the moving tongs 12,. Go up with 37). Thus, the control rod movement is performed by moving the drive shafts 14 and 32 holding the control rod up and down through the operations of the main mechanisms of the control rod driving apparatus 6.

FIG. 2 shows that the armature 50 becomes an electromagnet when the coil 48 is excited by the current 45 flowing from the armature 50 of the armature and the raising pole 44 of the stator by the direct current voltage 46. 44 shows the principle that the distance 47 is changed and the coil inductance 49 changes in inverse proportion to the detachment.

FIG. 3 shows the command values of the current that must flow through each coil of the control rod drive device 6 in the double holding. The main mechanisms of the three-coil type control rod drive system are stationary tongs, moving tongs and lifting armatures (movers) and lifting poles (stators). In any situation where the control rod is stationary, moving, or under any circumstances, one of the forceps of the control rod drive device is configured to hold the control rod drive shaft to prevent the control rod from falling. In order to determine the cause of the fault and to repair the fault because the abnormality occurs in the control rod drive system or control rod control system, in order to increase the reliability of the control rod fall prevention in such a situation, the maximum current flows simultaneously to all the coils of the control rod drive system. It is a double holding operation to have both tongs grab the drive shaft. 4 shows the current command value of each coil of the control rod drive device in the double holding operation. As shown in FIG. 4, the maximum current flows to both the stationary tong coils and the tong coils for a predetermined time, after which the current level is lowered to an intermediate level for the coil protection, and the raising coil lowers the current to the lowest zero level. .

If dual retaining is carried out while the control rod drive mechanisms are moving, that is, while the lifting mover of the control rod drive is not completely separated relative to the lifting stator, the tongs may not accurately grasp the groove of the control rod drive shaft, There is a risk of mechanical friction damage, and in the worst case there is a possibility of dropping the control rod. When a double hold is performed, the lifting coil current level 51 is reduced to zero amps 54 so that the lifting armatures 11 and 35 are separated from the lifting poles 10 and 33 and the stationary tong coil level 58 and the moving tongs. The coil level 55 is raised to a maximum allowable 8 amps 56, 59 so that the stop tongs 13, 43 and the moving tongs 12, 37 simultaneously grip the drive shafts 14, 32. Subsequently, if a large current continues to flow to the stationary tong coils 9 and 30 and the moving tong coils 8 and 28, the coils may be damaged. Lower to fair (57, 60) to hold until double hold is released.

4 shows examples of situations in which breakage may occur due to mechanical friction between the forceps and the drive shaft when the double holding operation is performed during the control rod insertion or withdrawal. Only the stop clamps 13 and 43 hold the drive shafts 14 and 32 and the moving tongs 12 and 37 move in the situation 62 in which the lifting armatures 11 and 35 are separated from the lifting poles 10 and 33. If the drive shafts 14 and 32 are gripped in the middle, there is a risk of breakage due to mechanical friction therebetween. The stop clamps 13 and 43 move in the situation 64 where only the moving tongs 12 and 37 hold the drive shafts 14 and 32 and the lifting armatures 11 and 35 are separated from the lifting poles 10 and 33. If the drive shafts 14 and 32 are being held (65), there is a risk of breakage due to mechanical friction between them. In the preceding examples, all cases of mechanical failure are associated with the movement of the lifting armatures 11, 35, which are the movers relative to the stator of the raising poles 10, 33, and the lifting armatures 11, 35 are raised poles 10. It can be seen that it is safe for the dual hold operation to be carried out after it has been completely disconnected from the control.

4 shows examples of situations in which mechanical damage may occur during the double holding operation in the process of withdrawing or inserting the control rod. All the situations here are related to the movement of the mover with respect to the raising stator. Therefore, in the double holding operation, the lifting coil current becomes zero, so that the lifting mover is separated from the lifting stator. Therefore, it can be seen that it is safe to perform the double holding operation after the mover is completely separated from the stator.

In order to know whether the lift mover is completely separated from the lift stator, the lift coil current waveform is analyzed. The principle is as follows. In the case of the lifting armature, which is the mover, and the lifting stimulus, which is the stator, these mechanisms are operated by electromagnetic forces by the excitation of the lifting coil. That is, the raising armature becomes an electromagnet and is detached by the raising stimulus. As the armature detaches from the raising stimulus, distortion occurs in the raising coil current waveform. The principle can be seen in FIG.

5 shows the configuration of the safe dual holding device 19 of the control rod drive device 6 according to the present invention and its peripheral devices. A power converter 3 for converting and supplying DC power from the AC input power source 1 to the raising coil 7, the moving tong coil 8, and the stationary tong coil 9, which are coils of the control rod driving device 6; There is a double holding device 19 that controls the operation of the control rod drive device 6 and determines whether various failures occur, and the double holding device 19 detects the operation of the same mechanism as the lifter of the control rod drive device 6. And generate and hold a dual hold operation setpoint.

The safe dual holding device 19 of the control rod drive device 6 according to the present invention is a signal processor 17. An analog-to-digital converter 18, a central processing unit 20, and a memory 23.

The signal processing unit 17 performs low frequency filtering scale adjustment processing on the currents of the coils sensed by the reactor control rod drive device 6 input before and after the expected separation time of the raising armature from the raising stimulus.

The analog-digital converter 18 converts the analog signals passed through the signal processor 17 into digital signals.

The central processing unit 20 wavelet transforms the digital signals from the analog-to-digital converter 18 to obtain wavelet transform coefficients, and determines whether or not the armature is separated according to the wavelet transform coefficients. Accordingly generates a dual hold operation control signal.

The CPU 20 compares the wavelet transform coefficients to a threshold value, and if the wavelet transform coefficients is greater than the threshold value, determines that the raising armature is separated from the raising stimulus, and the wavelet transform coefficients are the threshold values. If less, it is determined that the raising armature has not been separated from the raising stimulus.

In FIG. 3, when the current i flows through the coil, the armature (mover) becomes an electromagnet, and a magnetic force (puller) located above and a pulling force act on each other to reduce the distance z . The electrical equation in this case is as follows.

Equation 1 shows Kirchhoff's voltage equation, and Equation 2 shows that the inductance of the coil is inversely proportional to the distance between the mover and the stator. Where v is the applied voltage, i is the current flowing through the coil, R is the resistance of the coil, and k is a constant related to the number and shape of the windings of the coil. Therefore, the coil inductance L increases as the lifting mover is attached to the lifting stator, thereby reducing the magnitude of the current waveform. On the contrary, the coil inductance L decreases as the lifting mover is separated from the lifting stator. By this principle, it can be seen that the change of the current waveform is closely related to the operation of the instrument. According to the present invention, a method of determining whether the lifting mover is completely separated from the lifting stator and determining a safe double holding time by detecting a portion of the waveform in which the magnitude of the current waveform increases momentarily when the lifting mover is separated from the lifting stator. Devised.

  The wavelet transform used to detect the current waveform distortion that occurs when the lifting mover of the control rod drive device is separated from the lifting stator will be described. The wavelet means a curved signal having an integrated value of 0. Among the various wavelets, the present invention uses Morlet wavelet ψ (t) for wavelet transform. Morlet wavelet equation is shown in the following equation (3).

The wavelet group expression derived from the wavelet of Equation 3 is shown in Equation 4 below.

Where a is a scale factor for adjusting the height and width of the wavelet waveform and b is a position factor for horizontally moving the wavelet waveform. The equation for continuous wavelet transform on the arbitrary signal s (t) using Equations 3 and 4 is shown in Equation 5 below.

  In the actual system, since the coil voltage is sampled at 0.56 msec, Equation 5 is modified in discrete form, which is the same as the cross correlation between the coil voltage signal and the wavelet group equation. Equation 6 shows a continuous wavelet transform (CWT) equation through cross correlation of two signals.

Where n is the number of data, i is the current flowing through the coil, R is the resistance of the coil, k is the number of input current data, a is the scale factor for adjusting the height and width of the wavelet waveform, ψ _{a, 0} Is a Morlet wavelet. In Equation 6, it can be seen that the wavelet group equation having the positional factor of 0 is used in the cross correlation in Equation 4. Since the cross-correlation indicates the magnitude of the correlation between the two signals, when the vibration frequency of the portion where the input current signal is distorted and the vibration frequency of the wavelet group equation are similar, the result of Equation 6 becomes relatively large. The radian frequency of the wavelet group equation is determined by the scale factor, which is that the radian frequency of ψ ((tb) / a) of Equation 4 is 2π / a and thus the scale factor a is set to the frequency of ψ ((tb) / a). It is understood from inverse proportion. In the cross-correlation of Equation 6, if the inverse of the scale factor a of the wavelet group equation is set to be similar to the vibration frequency of the portion where the input current signal i is distorted by the mechanical motion, the cross-correlation through the wavelet group equation having a different scale factor It will have a larger value than the result. Through this, it is possible to determine whether distortion occurs due to the mechanism operation in the current waveform.

6 shows a typical raised coil current waveform 66. When the maximum allowable current flows in the lifting coil, the lifting armatures 11 and 35 become electromagnets, and a pulling force is generated between the lifting poles 10 and 33. This reduces the distance between the raising armatures 11 and 35 and the raising magnetic poles 10 and 33 and increases the coil inductance in inverse proportion to the distance. As the coil current decreases due to the increased coil inductance, distortion occurs, and when the raising armatures 11 and 35 adhere to the raising poles 10 and 33, the coil inductance no longer increases and the current also increases to a constant time constant. It can be seen that the current is greatly distorted 67 at the moment when the raising armatures 11 and 35 move and are attached to the raising magnetic poles 10 and 33. When the lifting armatures 11 and 35 attached to the lifting poles 10 and 33 are separated by reducing the lifting coil current to zero, and the distance between them is suddenly increased, the coil inductance is also suddenly reduced. This results in a distortion 68 which temporarily rises in the coil current the moment the lifting armatures 11 and 35 are separated. The present invention detects the occurrence of the current rise distortion 68 occurring at the moment when the lifting armatures 11 and 35, which are the movers, are separated from the lifting poles 10 and 33, thereby determining whether the lifting mover is completely separated from the lifting stator, and safely We want to find a point in time where maintenance can be done. The raising coil current waveform 66 mixes the pulsating component included in the DC voltage supplied from the power converter 3 constituted by the three-phase half-wave converter and various noises. And wavelet transform, which is superior in noise removal and local distortion analysis of waveforms, for the current distortion when the lifter is separated than when it is attached to the lifter, is completely separated from the lifter's lifter. I want to check.

7 actually shows a flowchart of an algorithm for determining the starting point of a safe double holding operation by detecting the operation of the raising armatures 11, 35 of the control rod drive 6. The process is characterized in that the movement maintaining device 19 is based on the current of the coil sensed by the control rod drive device 6 using the signal processor 17 and the analog / digital converter 18, and the coil current sampled by 0.56 msec. 90 pieces of data are stored in the memory 23 to obtain coil current data for 0.05 seconds before and after the expected separation of the lifting magnetic poles 10 and 33 of the lifting armatures 11 and 35 (step S710).

Thereafter, the CPU 20 wavelet transforms the coil current data near the 90-point armature separation expected time point to obtain a wavelet transform coefficient C (n) represented by Equation 6 (S720).

Subsequently, the central processing unit 20 determines whether the wavelet transform coefficient is vibrated and its magnitude is larger than the threshold (step S730).

When the wavelet transform coefficient is larger than the threshold, the wavelet transform coefficient vibrates to determine that the raising armatures 11 and 35 have been successfully separated from the raising magnetic poles 10 and 33, and the coil current data stored in the memory 23 is decoded. Delete (step S740).

On the contrary, when the wavelet transform coefficient is less than the threshold value, the wavelet transform coefficient does not vibrate so that the raising armatures 11 and 35 are not separated from the raising magnetic poles 10 and 33 and the coil stored in the memory 23 is determined. The current data is deleted (step S750).

Then, since the raising armatures 11 and 35 have not been successfully separated, it is notified that an abnormality has occurred on the raising coil side (step S760), and it is determined that the double holding operation may be started, and the starting point of the double holding operation is determined. A double hold command is issued (step S770).

8 shows the raising coil current and wavelet transform coefficients between 0.05 seconds before and after the lifting armatures 11, 35 are separated from the raising poles 10, 33. The dashed line 76 of the raising coil current waveform is when the raising armatures 11 and 35 are successfully separated and the solid line 77 of the raising coil current waveform is the raising magnetic pole 10 and 33 by the raising armature 11 and 35. It can't be separated from. As a result of the wavelet transform, the dotted line 79 in the case where the raising armatures 11 and 35 are normally separated vibrates greatly and exceeds the threshold, and the solid line 80 in the case where abnormal separation does not occur is caused by vibration. You can see little. In addition, it can be seen that the point 78 at which the magnitude of the wavelet transform coefficient is largest is the point at which the armatures 11 and 35 are separated from the pole magnetic poles 10 and 33.

The stable dual maintenance method and apparatus of the reactor control rod driving apparatus according to the present invention can be applied to the field where the reactor is used.

1 is a view showing the structure of a control rod drive device.

2 is a diagram illustrating a relationship between a change in distance between an armature and a magnetic pole and a change in coil inductance.

3 is a diagram illustrating each coil current command value of the control rod drive device for the dual holding operation.

4 is a diagram illustrating situations in which mechanical breakage between instruments is possible during a double holding operation.

5 is a device and a peripheral device for implementing a safe operation of the dual maintenance of the control rod drive device according to the present invention.

6 is a diagram illustrating a general raising coil current waveform.

7 is a flowchart illustrating a method of determining a start time of a dual holding operation by checking whether the lifting armature of the control rod driving apparatus is operated.

8 is a diagram illustrating a result of confirming that the raising armature is normally separated from the raising stimulus.

<Description of the symbols for the main parts of the drawings>

6: control rod driving device

10, 33: lifting stimulus

11, 35: rounding armature

17: signal processing unit

18: analog / digital converter

19: dual retainer

20: central processing unit

23: memory

Claims (7)

(i) obtaining a plurality of coil current data on the basis of the coil current sensed by the reactor control rod drive input before and after the expected separation of the raising armature from the raising stimulus; (ii) wavelet transforming the plurality of coil current data to obtain a wavelet transform coefficient; (iii) comparing the wavelet transform coefficients with a threshold; (iv) determining whether the raising armature is separated from the raising stimulus according to a comparison result of the wavelet transform coefficients and the threshold; And and (v) performing a dual holding operation according to the determination result of step (iv). The method of claim 1, wherein the wavelet transform coefficient is

Where C (n) is the wavelet transform coefficient, n is the number of data, i is the current flowing in the coil, R is the resistance of the coil, k is the number of input current data, and a is the wavelet waveform Scaling factor to control the height and width of, and ψ _{a, 0} is Morret wavelet, stable dual maintenance method of the reactor control rod drive device. The method of claim 1, wherein the starting point of the double holding operation is determined according to whether the raising armature is separated from the raising magnetic pole. 2. The method of claim 1, wherein if the wavelet transform coefficient is greater than the threshold, the rounding armature is determined to be separated from the raise stimulus and step (v) is performed, and if the wavelet transform coefficient is less than the threshold, the rounding And the step (v) is performed after determining that the armature is not separated from the lifting stimulus and indicating that an abnormality has occurred on the lifting side. A signal processor for adjusting the low frequency filtering scale of the coil current sensed by the reactor control rod driving device input before and after the expected separation of the raising armature from the raising stimulus; An analog-digital converter for converting the analog signals passed through the signal processing unit into digital signals; A center for wavelet transforming the digital signal from the analog-to-digital converter to obtain wavelet transform coefficients, determining whether or not the armature is separated according to the wavelet transform coefficients, and generating a dual hold operation control signal according to the determination result Stable dual holding device of the reactor control rod drive device including a processing device. The method of claim 1, wherein the wavelet transform coefficient is

Where C (n) is the wavelet transform coefficient, n is the number of data, i is the current flowing in the coil, R is the resistance of the coil, k is the number of input current data, and a is the wavelet waveform Scaling factor to control the height and width of, and ψ _{a, 0} is Morret wavelet, stable dual maintenance method of the reactor control rod drive device. The wavelet transform coefficient of claim 5, wherein the central processing unit compares the wavelet transform coefficients with a threshold, and when the wavelet transform coefficient is larger than the threshold, determines that the raising armature is separated from the raising stimulus. Is less than the threshold value, the dual arm holding device of the reactor control rod drive device which determines that the raising armature is not separated from the raising stimulus.

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