Speed ​​measurement device and method for hydro-generator set with dual-machine redundancy and power-off self-holding

Abstract

The dual-redundant, power-failure-safe speed measurement device for a hydro-turbine generator consists of two PLCs, one A and one B, connected to touch screens. Spur gear probes 1 and 2 detect the gear signal as it rotates with the turbine. The signals from these probes are fed simultaneously into the inputs of PLCs A and B. The dual PLCs are designed to perform simultaneous calculations, each equipped with its own touch screen for monitoring and parameter setting. When the speed measurement is functioning normally, PLC A controls the speed measurement. If PLC A crashes or if two or three input signals fail, control switches seamlessly to PLC B. Each speed output uses dual channels to drive a dual-coil relay, ensuring that even if the speed measurement fails, the currently activated speed relay maintains its output. This dual-redundant, power-failure-safe speed measurement device significantly enhances operational reliability, ensuring safe and stable operation of the hydro-turbine unit.

Description

Technical Field

[0001] The present invention relates to the technical field of auxiliary equipment of hydroelectric generators, and in particular to a rotational speed measuring device and method for a hydroelectric generator set with dual redundancy and power-off self-holding. Background Art

[0002] The speed measuring device plays an important role in the start-stop control and overspeed protection of hydro-generator sets. The stable and reliable operation of the speed measuring device is a key factor in ensuring the safety of the unit.

[0003] The speed measurement device uses two frequency measurement methods, the unit gear disc and PT residual pressure, for redundant input. After logical operation, it outputs more than ten required switching speed signals and provides two or more 4-20mA analog outputs.

[0004] The current speed measurement device generally uses 2-way gear disc and 1-way PT residual pressure signal input, and outputs switching speed signal and analog speed signal after a single set of PLC logic operation.

[0005] The current hydroelectric generator speed measuring device has the following defects:

[0006] (1) The principle of the current speed measurement device is as follows Figure 1 As shown, a single PLC is used for logic operations. When the PLC crashes or fails, it will cause abnormal output switching and analog signals, thus affecting the normal operation of the unit.

[0007] (2) The current 16-channel switching speed signal output of the speed measuring device all adopts PLC single-channel output. For example, in normal operation of the unit, the speed relay ≥90% needs to be energized and maintained. When the PLC fault stops the switching output or the speed measuring device loses power, the speed relay ≥90% will lose power, thereby affecting the normal operation of the unit; Figure 2 shown. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a speed measurement device and method for a hydro-generator set with dual-unit redundancy and power-off self-holding. This solves the problem that current speed measurement devices are controlled by only a single PLC, and if this single PLC fails, the entire device will not function. It also addresses the problem that the current speed measurement device's switch output speed signal malfunctions in the event of a PLC failure or power loss.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding includes a set of PLCs A and B and a set of touch screens A and B connected thereto, and also includes a gear disc probe 1 and a gear disc probe 2. The gear disc probe 1 and the gear disc probe 2 are used to detect the gear disc signal rotating with the turbine. The detection signals of the gear disc probe 1 and the gear disc probe 2 are simultaneously input into the input ends of the set of PLCs A and the set of PLCs B. The residual pressure PT signal is connected to the input ends of the shaping module 1 and the shaping module 2, and the 24V power supply is connected to the power supply ends of the shaping module 1 and the shaping module 2 through a shaping control circuit. When the shaping module 1 is working normally, the shaping module 1 inputs the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time. When the shaping module 1 fails, the shaping module 2 switches to inputting the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time.

[0011] The above-mentioned PLCs A and B receive the detection signals of gear disc probe 1 and gear disc probe 2 and the residual pressure PT signal and output the switching speed signal and the analog speed signal. PLC A serves as the main priority controller. After it is determined through the connection circuit between PLCs A and B that PLC A fails or the gear disc detection and PT signal of PLC A fail, PLC B becomes the main controller.

[0012] The connection circuit between the above-mentioned PLC set A and PLC set B is:

[0013] The three switching outputs Y0-Y2 of PLC A are connected to the three switching inputs X4-X6 of PLC B. The three switching outputs of PLC A send the set signals, and the three switching inputs of PLC B receive the set signals and judge the status of PLC A and the signal. If PLC A fails, the switching output Y3 of PLC B will turn to a high level.

[0014] The above-mentioned shaping control circuit structure is:

[0015] The 24V power supply is connected to the shaping module 1 through the normally closed switch of the power supply control relay K22, and the 24V power supply is connected to the shaping module 2 through the normally open switch of the power supply control relay K22;

[0016] The residual pressure PT signal is connected to the input end of the shaping module 1 through the normally closed switch of the PT signal input switching relay K23, and the residual pressure PT signal is connected to the input end of the shaping module 2 through the normally open switch of the PT signal input switching relay K23;

[0017] The output end of the shaping module 1 is connected to the input end of PLC A and PLC B through the normally closed switch of the pulse output switching relay K24, and the output end of the shaping module 2 is connected to the input end of PLC A and PLC B through the normally open switch of the pulse output switching relay K24.

[0018] The switch output Y1 of the above-mentioned B set PLC is electrically connected to the coil of the shaping module switching relay K25, and the other end of the coil of the shaping module switching relay K25 is connected to the positive pole of the 24V power supply;

[0019] The two ends of the coils of the power supply control relay K22, the PT signal input switching relay K23 and the pulse output switching relay K24 are connected in parallel, and the two ends of the parallel connection are respectively connected to the positive pole of the 24V power supply and the normally open switch of the shaping module switching relay K25. The upper end of the normally open switch of the shaping module switching relay K25 is connected to the negative pole of the 24V power supply.

[0020] The 16-channel switch signals of the above-mentioned PLC sets A and B are connected in parallel in pairs, and then connected to the corresponding speed relays to control the opening and closing of the speed relays. The current speed range value is determined by the state of the auxiliary switch of the speed relay.

[0021] The power supply of the above-mentioned PLC set A and PLC set B, touch screen set A and touch screen set B, and toothed disc probe 1 and toothed disc probe 2 is a combination of 220V AC and 24V switching power supply and a dual input of DC24V power supply.

[0022] PLC A and touch screen A are powered by a DC24V power supply and controlled by the normally closed switch of the power control relay K28 of system A. One end of the coil of the power control relay K28 is electrically connected to the switch output Y0 of PLC B, and the other end of the coil of the power control relay K28 is connected to the positive pole of the 24V power supply;

[0023] The PLC set B, the touch screen set B, the toothed disc probe 1 and the toothed disc probe 2 are powered by a combination of 220V AC and 24V switching power supply.

[0024] The combined output end of the above-mentioned 220V AC and 24V switching power supply is provided with a power supply monitoring 1 relay K26, and the output end of the DC24V power supply is provided with a power supply monitoring 2 relay K27. The normally open switches of the power supply monitoring 1 relay K26 and the power supply monitoring 2 relay K27 are connected in series, and the two ends of the series are connected to the monitoring system.

[0025] The aforementioned PLCs A and B each have four analog outputs. The four analog outputs of PLC A are connected to the normally closed switches of the first to fourth analog switching relays K29-K32, and the four analog outputs of PLC B are connected to the normally open switches of the first to fourth analog switching relays K29-K32.

[0026] The switching output Y2 of PLC B is connected to one end of the coil of the 4-channel analog switching relay K33, and the other end of the coil of the 4-channel analog switching relay K33 is connected to the positive pole of the 24V power supply;

[0027] The two ends of the coils of the first to fourth analog switching relays K29-K32 are connected in parallel, one end of the parallel ends is connected to the positive pole of the 24V power supply, and the other end is connected to the normally open switch of the 4-way analog switching relay K33. The upper end of the normally open switch of the 4-way analog switching relay K33 is connected to the negative pole of the 24V power supply.

[0028] Using the speed measurement method of the dual-machine redundant and power-off self-holding speed measurement device of the hydro-generator set, the switch output Y0 of PLC A sends a 5Hz signal to the switch input X4 of PLC B, the switch output Y1 of PLC A sends a low-level signal to the switch input X5 of PLC B, and the switch output Y2 of PLC A sends a low-level signal indicating that both the two-way gear plate and the residual pressure PT signals are faulty to the switch input X6 of PLC B;

[0029] When the switch input X4 of PLC B does not receive a 5Hz signal or X5 does not receive a low-level signal, it is determined that PLC A is dead. When PLC A is working normally, but the switch input X6 of PLC B receives a low-level signal, it is determined that both the 2-way gear plate and the residual pressure PT signal of PLC A are faulty.

[0030] When PLC B determines that PLC A has crashed or the gear plate and PT signal of PLC A are both faulty, PLC B takes over as the main function and synchronously generates a speed switch signal.

[0031] The present invention provides a speed measurement device and method for a hydro-turbine generator set with dual redundancy and power-off self-holding. Dual PLC systems are designed for simultaneous calculations, and both PLCs are independently equipped with touch screens for monitoring and parameter setting. When the speed measurement is normal, it is controlled by PLC A. When PLC A crashes or two or three input signals fail, it switches to PLC B without disruption. Furthermore, each speed switch output uses a dual channel to drive a dual-coil relay, ensuring that even if the speed measurement fails as a whole, the currently activated speed relay can still maintain output. This dual-redundancy speed measurement device with power-off self-holding greatly enhances operational reliability, ensuring the safe and stable operation of the hydro-turbine set. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below with reference to the accompanying drawings and examples:

[0033] Figure 1 This is the schematic diagram of the speed measurement device for the current single CPU or PLC;

[0034] Figure 2 It is the single-channel output switching signal mode of the current speed measuring device;

[0035] Figure 3 This is a schematic diagram of the speed measurement device panel with dual PLC redundancy;

[0036] Figure 4 This is a schematic diagram of the switching logic of the dual-machine PLC;

[0037] Figure 5 Principle of speed measurement device for dual-machine redundant control Figure 1 ;

[0038] Figure 6 Principle of speed measurement device for dual-machine redundant control Figure 2 ;

[0039] Figure 7 Principle of speed measurement device for dual-machine redundant control Figure 3 ;

[0040] Figure 8 Principle of speed measurement device for dual-machine redundant control Figure 4 ;

[0041] Figure 9 Principle of speed measurement device for dual-machine redundant control Figure 5 ;

[0042] Figure 10 Principle of speed measurement device for dual-machine redundant control Figure 6 ;

[0043] Figure 11 It is a dual-channel output switching signal mode of the speed measurement device with power-off retention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0045] A speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding includes a set of PLCs A and B and a set of touch screens A and B connected thereto, and also includes a gear disc probe 1 and a gear disc probe 2. The gear disc probe 1 and the gear disc probe 2 are used to detect the gear disc signal rotating with the turbine. The detection signals of the gear disc probe 1 and the gear disc probe 2 are simultaneously input into the input ends of the set of PLCs A and the set of PLCs B. The residual pressure PT signal is connected to the input ends of the shaping module 1 and the shaping module 2, and the 24V power supply is connected to the power supply ends of the shaping module 1 and the shaping module 2 through a shaping control circuit. When the shaping module 1 is working normally, the shaping module 1 inputs the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time. When the shaping module 1 fails, the shaping module 2 switches to inputting the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time.

[0046] The above-mentioned PLCs A and B receive the detection signals of gear disc probe 1 and gear disc probe 2 and the residual pressure PT signal and output the switching speed signal and the analog speed signal. PLC A serves as the main priority controller. After it is determined through the connection circuit between PLCs A and B that PLC A fails or the gear disc detection and PT signal of PLC A fail, PLC B becomes the main controller.

[0047] The connection circuit between the above-mentioned PLC set A and PLC set B is:

[0048] The three switching outputs Y0-Y2 of PLC A are connected to the three switching inputs X4-X6 of PLC B. The three switching outputs of PLC A send the set signals, and the three switching inputs of PLC B receive the set signals and judge the status of PLC A and the signal. If PLC A fails, the switching output Y3 of PLC B will turn to a high level.

[0049] The above-mentioned shaping control circuit structure is:

[0050] The 24V power supply is connected to the shaping module 1 through the normally closed switch of the power supply control relay K22, and the 24V power supply is connected to the shaping module 2 through the normally open switch of the power supply control relay K22;

[0051] The residual pressure PT signal is connected to the input end of the shaping module 1 through the normally closed switch of the PT signal input switching relay K23, and the residual pressure PT signal is connected to the input end of the shaping module 2 through the normally open switch of the PT signal input switching relay K23;

[0052] The output end of the shaping module 1 is connected to the input end of PLC A and PLC B through the normally closed switch of the pulse output switching relay K24, and the output end of the shaping module 2 is connected to the input end of PLC A and PLC B through the normally open switch of the pulse output switching relay K24.

[0053] The switch output Y1 of the above-mentioned B set PLC is electrically connected to the coil of the shaping module switching relay K25, and the other end of the coil of the shaping module switching relay K25 is connected to the positive pole of the 24V power supply;

[0054] The two ends of the coils of the power supply control relay K22, the PT signal input switching relay K23 and the pulse output switching relay K24 are connected in parallel, and the two ends of the parallel connection are respectively connected to the positive pole of the 24V power supply and the normally open switch of the shaping module switching relay K25. The upper end of the normally open switch of the shaping module switching relay K25 is connected to the negative pole of the 24V power supply.

[0055] The 16-channel switch signals of the above-mentioned PLC sets A and B are connected in parallel in pairs, and then connected to the corresponding speed relays to control the opening and closing of the speed relays. The current speed range value is determined by the state of the auxiliary switch of the speed relay.

[0056] The power supply of the above-mentioned PLC set A and PLC set B, touch screen set A and touch screen set B, and toothed disc probe 1 and toothed disc probe 2 is a combination of 220V AC and 24V switching power supply and a dual input of DC24V power supply.

[0057] PLC A and touch screen A are powered by a DC24V power supply and controlled by the normally closed switch of the power control relay K28 of system A. One end of the coil of the power control relay K28 is electrically connected to the switch output Y0 of PLC B, and the other end of the coil of the power control relay K28 is connected to the positive pole of the 24V power supply;

[0058] The PLC set B, the touch screen set B, the toothed disc probe 1 and the toothed disc probe 2 are powered by a combination of 220V AC and 24V switching power supply.

[0059] The combined output end of the above-mentioned 220V AC and 24V switching power supply is provided with a power supply monitoring 1 relay K26, and the output end of the DC24V power supply is provided with a power supply monitoring 2 relay K27. The normally open switches of the power supply monitoring 1 relay K26 and the power supply monitoring 2 relay K27 are connected in series, and the two ends of the series are connected to the monitoring system.

[0060] The aforementioned PLCs A and B each have four analog outputs. The four analog outputs of PLC A are connected to the normally closed switches of the first to fourth analog switching relays K29-K32, and the four analog outputs of PLC B are connected to the normally open switches of the first to fourth analog switching relays K29-K32.

[0061] The switching output Y2 of PLC B is connected to one end of the coil of the 4-channel analog switching relay K33, and the other end of the coil of the 4-channel analog switching relay K33 is connected to the positive pole of the 24V power supply;

[0062] The two ends of the coils of the first to fourth analog switching relays K29-K32 are connected in parallel, one end of the parallel ends is connected to the positive pole of the 24V power supply, and the other end is connected to the normally open switch of the 4-way analog switching relay K33. The upper end of the normally open switch of the 4-way analog switching relay K33 is connected to the negative pole of the 24V power supply.

[0063] Using the speed measurement method of the dual-machine redundant and power-off self-holding speed measurement device of the hydro-generator set, the switch output Y0 of PLC A sends a 5Hz signal to the switch input X4 of PLC B, the switch output Y1 of PLC A sends a low-level signal to the switch input X5 of PLC B, and the switch output Y2 of PLC A sends a low-level signal indicating that both the two-way gear plate and the residual pressure PT signals are faulty to the switch input X6 of PLC B;

[0064] When the switch input X4 of PLC B does not receive a 5Hz signal or X5 does not receive a low-level signal, it is determined that PLC A is dead. When PLC A is working normally, but the switch input X6 of PLC B receives a low-level signal, it is determined that both the 2-way gear plate and the residual pressure PT signal of PLC A are faulty.

[0065] When PLC B determines that PLC A has crashed or the gear plate and PT signal of PLC A are both faulty, PLC B takes over as the main function and synchronously generates a speed switch signal.

[0066] Example:

[0067] The present invention designs a high reliability speed measuring device with dual PLC redundancy; the device housing is as follows Figure 3 The electrical schematic diagram of the device is shown in Figures 5 to 10 As shown, AC220V and DC24V redundant power supplies are adopted, among which the AC220V power supply is converted into DC24V by the power supply device and then redundantly supplied with the input DC24V; the device adopts two sets of PLCs, and each set of PLCs is equipped with a touch screen for data display and parameter setting; the 2-way gear plate H1 and H2 signals are simultaneously input to the high-speed pulse input terminals of sets A and B of PLCs. Under normal circumstances, the residual pressure PT signal is simultaneously input to the high-speed pulse input terminals of sets A and B of PLCs through the shaping board 1, and K22\K23\K24 are all de-energized. If the shaping board 1 fails, after K25 is energized by the switching output terminal Y0 of set B of PLC, K22\K23\K24 are all energized and switched to the high-speed pulse input terminals of sets A and B of PLCs through the shaping board 2.

[0068] Under normal circumstances, after the speed measuring device A and B sets of PLCs collect the signals of the 2-way gear plate H1, H2 and the residual pressure PT, the A set of PLCs takes priority in control and outputs the switching speed signal and the analog speed signal; at the same time, the B set of PLCs performs synchronous operation and determines in real time that the A set of PLCs is dead and not working. Figure 9 Method: 1. PLC A sends 5Hz frequency to PLC B, the output terminal of PLC A is Y0, and the receiver of PLC B is X4; 2. PLC A always sends low-level signal to PLC B, the output terminal of PLC A is Y1, and the receiver of PLC B is X5; when the X4 terminal of PLC B does not receive the 5Hz signal input by PLC A or the X5 does not receive the low-level signal, it is judged that PLC A is dead; when PLC A is working normally, PLC A detects that both the gear disc and PT signal are faulty, and the output terminal Y2 of PLC A outputs a low level to the input terminal X6 of PLC B, and PLC B judges that both the gear disc and PT signal of PLC A are faulty; the dual-machine switching logic is as follows Figure 4 shown.

[0069] When PLC B determines that PLC A has crashed or the gear disc and PT signal of PLC A are both faulty, PLC B takes over as the main function and synchronously outputs the speed switch signal; and the switch output terminal Y2 of PLC B drives relay K33 to be energized, and K33 drives relays K29, K30, K31, and K32 to be energized, switching the analog speed signal from PLC A to PLC B output; after a delay, the switch output terminal Y0 of PLC B drives relay K28 to be energized, and after the normally closed contact of K28 is disconnected, the power supply of PLC A and the touch screen is disconnected, and at the same time, the switch output terminal Y3 of PLC B reports "main PLC failure".

[0070] The current speed measurement device uses a single-channel PLC to generate the switching speed signal. For example, if the speed signal is ≥90%, Figure 2 As shown in the figure, in the PLC program, when the speed signal is ≥90%, Y3 is output, and when it is ≤80%, Y3 is stopped. During normal operation, the speed of the unit is 100%, and the PLC must always output Y3. When the speed measuring device loses power or the PLC fails, the switch speed signal will stop outputting, thus affecting the normal operation of the unit. To address this problem, a dual-channel drive dual-coil relay is used for each switch speed signal, such as Figure 10 As shown; still taking the speed signal ≥ 90% as an example, Figure 8As shown, in the PLC program, when the speed signal is ≥90%, Y14 is turned on to drive the closing coil of the double-coil relay K3, that is, the A1 and A2 terminals. In the PLC program, when the speed signal is ≤80%, Y15 is turned on to drive the opening coil of the double-coil relay K3, that is, the B1 and B2 terminals. The characteristic of the double-coil relay is that as long as the closing coil is briefly energized, it will remain in the closed position, and will remain in the open position only after the opening coil is briefly energized. In normal operation, the speed of the unit is 100%. In the PLC program, when the speed signal is ≥90%, Y14 is turned on to drive the closing coil of the double-coil relay K3. K3 is always in the closed position. When the speed measuring device loses power as a whole or the PLC fails, K3 still remains in the closed position, and the speed signal still maintains normal output, thereby ensuring the normal operation of the unit.

Claims

1. A speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding, characterized by: It includes a set of PLCs A and B and a set of touch screens A and B connected thereto, and also includes a gear disc probe 1 and a gear disc probe 2. The gear disc probe 1 and the gear disc probe 2 are used to detect the gear disc signal that rotates with the turbine. The detection signals of the gear disc probe 1 and the gear disc probe 2 are simultaneously input into the input ends of the set of PLCs A and the set of PLCs B. The residual pressure PT signal is connected to the input ends of the shaping module 1 and the shaping module 2, and the 24V power supply is connected to the power supply end of the shaping module 1 and the shaping module 2 through a shaping control circuit. When the shaping module 1 is working normally, the shaping module 1 inputs the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time. When the shaping module 1 fails, the shaping module 2 switches to inputting the shaped residual pressure PT signal to the input ends of the set of PLCs A and the set of PLCs B at the same time. The PLC set A and PLC set B each have 4 analog outputs. The 4 analog outputs of PLC set A are connected to the normally closed switches of the first to fourth analog switching relays K29-K32, and the 4 analog outputs of PLC set B are connected to the normally open switches of the first to fourth analog switching relays K29-K32. The switching output Y2 of PLC B is connected to one end of the coil of the 4-channel analog switching relay K33, and the other end of the coil of the 4-channel analog switching relay K33 is connected to the positive pole of the 24V power supply; The two ends of the coils of the first to fourth analog switching relays K29-K32 are connected in parallel, one end of the two parallel ends is connected to the positive electrode of the 24V power supply, and the other end is connected to the normally open switch of the 4-way analog switching relay K33. The upper end of the normally open switch of the 4-way analog switching relay K33 is connected to the negative electrode of the 24V power supply; The switching output Y0 of PLC A sends a 5Hz signal to the switching input X4 of PLC B. The switching output Y1 of PLC A sends a low-level signal to the switching input X5 of PLC B. The switching output Y2 of PLC A sends a low-level signal indicating that both the two gear discs and the residual pressure PT signals are faulty to the switching input X6 of PLC B. When the switch input X4 of PLC B does not receive a 5Hz signal or X5 does not receive a low-level signal, it is determined that PLC A is dead. When PLC A is working normally, but the switch input X6 of PLC B receives a low-level signal, it is determined that both the 2-way gear plate and the residual pressure PT signal of PLC A are faulty. When PLC B determines that PLC A has crashed or the gear plate and PT signal of PLC A are both faulty, PLC B takes over as the main function and synchronously generates a speed switch signal.

2. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 1 is characterized in that: The PLCs A and B receive the detection signals of the gear disc probe 1 and the gear disc probe 2 and the residual pressure PT signal and output the switching speed signal and the analog speed signal. The PLC A serves as the main priority controller. After determining through the connection circuit between the PLCs A and B that the PLC A fails or the gear disc detection and PT signal of the PLC A fail, the PLC B becomes the main controller.

3. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 2 is characterized in that: The connection circuit between the A set of PLC and the B set of PLC is: The three switching outputs Y0-Y2 of PLC A are connected to the three switching inputs X4-X6 of PLC B. The three switching outputs of PLC A send the set signals, and the three switching inputs of PLC B receive the set signals and judge the status of PLC A and the signal. If PLC A fails, the switching output Y3 of PLC B will turn to a high level.

4. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 3 is characterized in that: The shaping control circuit structure is: The 24V power supply is connected to the shaping module 1 through the normally closed switch of the power supply control relay K22, and the 24V power supply is connected to the shaping module 2 through the normally open switch of the power supply control relay K22; The residual pressure PT signal is connected to the input end of the shaping module 1 through the normally closed switch of the PT signal input switching relay K23, and the residual pressure PT signal is connected to the input end of the shaping module 2 through the normally open switch of the PT signal input switching relay K23; The output end of the shaping module 1 is connected to the input end of PLC A and PLC B through the normally closed switch of the pulse output switching relay K24, and the output end of the shaping module 2 is connected to the input end of PLC A and PLC B through the normally open switch of the pulse output switching relay K24.

5. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 4, characterized in that: The switch output Y1 of the B set PLC is electrically connected to the coil of the shaping module switching relay K25, and the other end of the coil of the shaping module switching relay K25 is connected to the positive pole of the 24V power supply; The two ends of the coils of the power supply control relay K22, the PT signal input switching relay K23 and the pulse output switching relay K24 are connected in parallel, and the two ends of the parallel connection are respectively connected to the positive pole of the 24V power supply and the normally open switch of the shaping module switching relay K25. The upper end of the normally open switch of the shaping module switching relay K25 is connected to the negative pole of the 24V power supply.

6. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 5, characterized in that: The 16-way switching signals of the A set PLC and the B set PLC are connected in parallel in pairs, and then connected to the corresponding speed relays to control the opening and closing of the speed relays. The current speed range value is determined by the state of the auxiliary switch of the speed relay.

7. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 5, characterized in that: The power supply of the PLC set A and PLC set B, the touch screen set A and touch screen set B, and the toothed disc probe 1 and the toothed disc probe 2 is a combination of 220V AC and 24V switching power supply and a dual input of DC24V power supply. PLC A and touch screen A are powered by a DC24V power supply and controlled by the normally closed switch of the power control relay K28 of system A. One end of the coil of the power control relay K28 is electrically connected to the switch output Y0 of PLC B, and the other end of the coil of the power control relay K28 is connected to the positive pole of the 24V power supply; The PLC set B, the touch screen set B, the toothed disc probe 1 and the toothed disc probe 2 are powered by a combination of 220V AC and 24V switching power supply.

8. The speed measuring device for a hydro-generator set with dual redundancy and power-off self-holding according to claim 7, characterized in that: The combined output end of the 220V AC and 24V switching power supply is provided with a power supply monitoring 1 relay K26, and the output end of the DC24V power supply is provided with a power supply monitoring 2 relay K27. The normally open switches of the power supply monitoring 1 relay K26 and the power supply monitoring 2 relay K27 are connected in series, and the two ends of the series are connected to the monitoring system.

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