JPS5915609A - Steam turbine controller - Google Patents

Abstract

PURPOSE:To clear up the cause of a pressure drop, by providing a device, which holds a control valve to no load opening even after the recovery of pressure and manually opens the valve, to a pressure drop preventing device detecting the pressure drop of inlet steam of a steam turbine and throttling the control valve. CONSTITUTION:Deviation between signals from a speed detector 13 and a speed setter 15 and a signal of a load limiter 19 of a turbine 4 are input to a low value preferential circuit 18, and a control valve 3 is opened and closed by a low value signal of said circuit 18. A main steam pressure detector 27 is provided to a steam pipe, and deviation from a set pressure 28 is input to the low value preferential circuit 18. An automatic follow up circuit 34A following to an output of a limit circuit 31 is provided. Even if steam pressure is decreased, an integrator 40 follows to the output of the circuit 31, however, if the pressure is restored and the output of the circuit 31 is increased, a comparator 41 opens a contact 35, and integrating action is stopped, while an output of low value preferantial circuits 32, 18 becomes an output of the integrator 40, then the control valve is held to be throttled, and the valve is reopened by a manual switch 38.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a system for controlling steam control when the inlet steam pressure falls below a predetermined value in order to prevent cold air or water from flowing into the steam turbine' due to a q50 steam pressure drop. This invention relates to a steam turbine control device equipped with an inlet steam pressure drop prevention control device N'fx that throttles a valve.

[Technical background of the invention]

A boiler failure in a thermal power plant or a flasher well failure in a geothermal power plant can cause a sudden drop in the steam pressure at the inlet of the steam turbine, and if this pressure drop occurs, there is a risk that cold air or water may flow into the steam turbine. There is.

Is this cold air or water flowing in? In order to prevent this, it has already been proposed to provide the above-mentioned inlet steam pressure drop prevention control device (hereinafter referred to as IPRJ).

The inlet steam pressure of this IPRH1 steam turbine is generally detected in the piping section in front of the main steam stop valve I7, and when the detected pressure drops below a predetermined value, a signal is issued to throttle the steam regulator valve. However, if the pressure does not recover, the steam control valve is throttled down to the no-load opening by reducing the pressure further to a predetermined point i, which is 1 g below that level.A specific example of this is shown in FIG.

In Fig. 1, first of all, the main system will be explained.The main steam from the boiler 1 is passed through the main steam stop valve 2 and the steam control valve 3'ft.
- is supplied to the direct pressure turbine 4. The steam control valve 3 supplies the high-pressure turbine 4 with an amount of steam commensurate with the turbine photoelectric machine load. The steam that has done work in the high-pressure turbine 4 is heated in a reheater 5, and is connected to a reheat steam stop valve 6 and an intercept valve 7'.
fr, flows into the intermediate pressure turbine 8 via. The steam worked here further flows into the low pressure turbine 9 via the crossover pipe 8Al. The steam worked by the low pressure turbine 9 flows into the condenser 10 and is condensed. The illustrated steam turbine is box-shaped, and includes a high-pressure turbine 4, an intermediate-pressure turbine 8, and a low-pressure turbine 9 on one shaft, and a generator 11 is driven by the shaft output.

For the above main system, the control section including IPRi is configured as follows. 1st speed: W The control section first includes a speed detection gear 12 directly connected to the shaft of the steam turbine and a 1st speed detection gear 12 facing the outer peripheral surface thereof. Speed detection pickup 13 arranged at
A frequency signal proportional to the turbine rotational speed is obtained as an actual speed signal of the steam turbine. This frequency signal is converted by a frequency/positive pressure converter 4 into an analog voltage signal proportional to the frequency. Speed/load setting device 15
The speed/load setting signal from the frequency/voltage converter 514 and the turbine actual speed signal from the frequency/voltage converter 514 are led to an adder 16, and a signal corresponding to the deviation of both speeds is outputted as a speed/load deviation signal. is led to the speed regulation rate circuit 17i- and the intersegment valve regulation rate circuit.

The speed regulation rate circuit 17 generates an opening degree signal for obtaining the opening degree of the steam control valve 3 that matches the speed regulation rate based on the input deviation signal, and inputs it to the low position priority circuit 18. This low value priority circuit 18KI-t also receives a load limit signal from the load limiter 19 and a limit signal from IPR: Phantom A, and outputs the lowest value signal among the three human power signals. This output signal is power amplified by the power amplifier 2o and input to the electro-hydraulic converter 21. ") f.

The electrical signal input to the oil converter 21 is converted into a mechanical signal, and the pilot valve of the steam control valve oil cylinder 22 is operated 17 to adjust the opening degree of the steam control valve 3 to match the desired opening signal. Control.

The regulation rate circuit 23 produces an intercept valve opening signal based on the deviation output from the adder 6. This opening degree signal is power amplified by the power amplifier 24 and converted into a mechanical signal by the battery converter 5. [[The pilot valve for the ink segment valve oil level is operated by the mechanical opening signal from the electro-hydraulic converter δ, and the intercept valve 7 is controlled to an opening that matches the required opening signal. This is the speed Hi control section.

Next, the IPR-:3OA portion will be explained. First, the main steam pressure Poi is detected by the pressure detector 27 on the inlet side of the main steam stop valve 2. This actual pressure signal is IPR:
30A is led to the adder 29 together with the set pressure signal from the pressure setter section. This set pressure is generally the main steam pressure PO
IL- is reduced to 80% of the rated value PR (P@)4.
The steam adjustment 5P3 is set to correspond to the no-load opening CvN. The adder 29 operates only when the deviation between the actual pressure and the set pressure is positive, that is, in the case of the above set value, only when the main steam pressure Po is 80% (Pi) or more of the rated value PFI. The deviation signal is output. This deviation signal is input between the pressure regulation rate circuits. Based on the input deviation signal, the pressure adjustment rate circuit 30 starts throttling the steam control valve 3 from the fully open CVO when the main steam pressure PO drops to 90% (PA) of the rated value P8, and then controls the steam control valve 3 at a pressure of 80% (Pa). A steam control valve opening signal is generated such that the steam control valve 3 reaches the no-load opening CvN and maintains the same no-load opening CVN even if the pressure decreases below that level (see FIG. 2). This opening change signal &1 limit circuit to prevent the steam control valve 3 from being opened below the no-load opening CVN: (1 to xm and I P R3
It is input to the exclusion circuit 33 as the output R number of 0A. The exclusion circuit 33 is a circuit portion provided because it is necessary to exclude all of the above-mentioned functions of the IPR 30A when starting the turbine by lowering the main steam pressure. This exclusion circuit is 33wo1! The J1 steam control valve opening signal is input to the low value priority circuit 18.

In Figure 1, the IPR3OA's . Main steam pressure Po is t1
It starts to decrease at point t2, and at point t2, the value P equivalent to 90% of the rated value
When it decreases to A, the output i of the IPR30A starts to decrease from the fully open CVo of the steam control valve 3. t
When the output A becomes smaller than the limit signal B from the 1.7 degree control section (that is, the speed If adjustment rate circuit 17) or the load limiter 19 at time 3, the low value priority circuit 18 acts to reduce the output A.
becomes the opening degree signal of the steam regulating valve 3, and the opening I of the steam regulating valve 3
U''CV starts to decrease from this point t3. This throttling operation causes the main steam pressure PO to drop to an exact extent, and when the main steam pressure PO starts to rise E7 due to failure recovery on the boiler side, the output of IPR: 3OA A also increases 1. At the beginning, the steam control valve opening CV also increases (suddenly, the steam control valve 3 also opens 1&
) Doing〈. At time t4, the output A becomes larger than the limit signal B from the middle of the vehicle speed limit or the load limiter 19, and the opening signal of the steam control valve 3 shifts to the output B, and the steam control valve 3 at this point The movement is accurate. When the main steam pressure PO reaches 90% (PA) at time t6, IPR: 30A
The output A becomes a fully open CVo signal, and the main steam pressure Po reaches the rated Ili at time t6, and this state continues for one period thereafter.

[Problems with background technology]

The conventional IPR 30A shown in FIG. 1 narrows down the steam control valve 3 according to the inlet steam pressure of the steam control valve 3 with a linear characteristic, and when the inlet steam pressure recovers, naturally the group control valve 3
will open. However, the decrease in the steam pressure at the inlet of the steam control valve 3 1-. 1 This is often caused by a failure in the boiler, flasher tank, or other equipment parts, and in such cases, the steam control valve 3 is opened as soon as the pressure is restored in 11 without clarifying the cause of the failure, and the load on the steam turbine is reduced to J'+.
Since the child has been given an additional ¥, there is a risk that the child will have the same trouble again.

[Purpose of the invention]

An object of the present invention is to provide a steam turbine control system that eliminates the above-mentioned drawbacks and prevents the above-mentioned troubles that may occur when the pressure is restored after the steam control valve is throttled by the action of IPR when the inlet steam pressure decreases. Providing equipment
be.

[Summary of the invention]

In order to achieve this objective, the present invention maintains the structure for throttling the steam control valve by no-load opening by IPH when the inlet steam pressure of the steam turbine decreases, and then the inlet steam pressure is reduced to 1 M Even if the IPH function is disabled, the steam control valve is held at the open position for one moment (7. When the cause of the inlet steam pressure drop is investigated and it is determined that there is no problem, the steam control valve can be manually turned off. 1- to open and return to the original normal operating state.

[Embodiments of the invention]

Figure 4 Glue, Nibi I''1'mo Figure 5 is Kazumi Honcho Akira u15
Here, the same components as in Figure 1 are designated by the same reference numerals. Figure 4 is a block diagram representing the overall configuration of the device; (in the figure)
A more detailed circuit configuration of the 3' section is shown below.The features of this device include: an IJ circuit that forms the output stage of the IPR30A; a low-value priority circuit between 31 and the exclusion circuit 33;
Insert 32 pieces and add a limit circuit to this low value priority circuit 32:
The output signal of the automatic tracking circuit 34A, which will be described later, is input to Vl of the output signal of 31, and the low value of the inner input signal, that is, the low level one, is sent to the 1 thread outer circuit and 33. A set pressure signal given in the form of a pressure release from a pressure setting device 28 consisting of a constant voltage source 28a and its constant voltage source 28a and a potentiometer 28b that divides the pressure, and a pressure detector 27 4M of the deviation from the detection signal from the heater 29'f is input to the pressure adjustment rate circuit 30.The heater 29' and the pressure adjustment rate circuit 30i
l-j The operational amplifier 30a is integrally formed with the operational amplifier 30a as the center, and the amplifier resistor 9a is provided on the input side of the operational amplifier 30a.

29b, operational resistor provided in the feedback circuit; 30b, and inverter provided on the output side; 30c to tj2
It's on. Operational amplifier; phantom a and operational resistance 29a
+ : '-95 + 30 b K Therefore, based on the deviation of both manual forces, [7] Calculate the pressure adjustment rate (1'). Limit circuit 31 i1 Steam control valve fully open (Fig. 2 CVo) k Yobi load open It is used to set the level of IK (Flood 2 Figure CVII).The output signal of limit times @:31 is input to the low 11α priority circuit 32K, but this low l1
Another input to the circuit 32? An automatic i blind follower circuit 34A is provided for r4+.

This automatic tracking circuit 34 A f is an operational amplifier 34 without switching.
d and arithmetic resistor for inputting input, 34a, 3-1b
, the calculated resistor 34c provided in the feedback circuit, and the calculated resistor 34b (inverter provided in the α column; 34
34 is configured by e, where IPR3OA
The difference between the output signal of the limit circuit 31, that is, the output signal of the limit circuit 31, and the output of the equal bet 40, which will be described later, is expressed as V1. The signal g representing the calculation result is led to one input end of the adder 37 through break contacts 35 and 36 connected in parallel with each other, and the other input y is connected to a manual setting device;
The pressure setting signal from 39 is sent to manual switch 38 (N!l
e.g. via a push button switch). The manual setting device 39 basically has the same configuration as the pressure setting device Z8, and is connected to the constant voltage source 39a and the potentiometer 39b for dividing the constant pressure. Add
The multiplier 37 and the integrator 40 are centered around an operational amplifier 40a, and include an operational resistor 7a for inputting the tr++ calculation input phase.
The output signal C of the integrator 40, which is configured by adding 37 b k and an integrating capacitor 40b, is added to t3 as described above.
The output of the automatic follow-up circuit 34A is used as the second input of the low value 1 priority circuit 32, and is further used as the first input of the comparator 4. Comparison? Limit circuit 3 as the second input of 12 device 41
1 output signal is used. Compare the output of comparator 411-t and 46 divider 40 with the output of limit circuit: (1,
When the latter is also small in the former, contact 35 is connected to L7, the main steam pressure rises, and when the output of limit circuit 31 starts to increase, the latter becomes louder than the former. Contact: Open 35.

The opening and closing of the contact point 36 is controlled by a comparator 42. The comparator 42 compares the output of the low value priority circuit 32 with the output of the speed regulation rate circuit 17, and if the former is larger than the latter, it closes the contact 36, and in the opposite case, the contact 36 is fully opened. .

The operation of the device 4 shown in FIGS. 4 and 5 can be summarized as follows by focusing on the operations of the contacts 35 and 36.

Mode 1) When the main steam pressure Po is 90% of the rated value (P piece or more and the output of limit circuit 31 is at the upper limit value, that is, when IPR does not substantially move, both contacts 35° and 6 are closed. and the integrator ↓O is the limit circuit, 3
Follow-up operation is performed so that the output becomes equal to the output of 1.

Mode 2) When the main steam pressure PO drops below 90% (PA) of the rated value, the output of the limit circuit 31 is output from the speed regulation rate circuit 17 of the speed IW control section or the limit signal from within the load limiter. When the equation becomes smaller, the comparator 42 opens the 1y point: U6. 2. Even in this state, as long as the follow-up circuit including the integrator 40 is operating, the output of the integrator 40 will not become smaller than the output of the limit circuit 31, so the contact 35 remains closed. , [4 divider 4 (] is a limit circuit; it follows the output of 31 and is closed.

Mode 3) Main steam pressure Po recovers, limit circuit; 3
When the output of limit circuit 1 changes in the increasing direction, the output of integrator 40 becomes smaller than the output of limit circuit 1, and comparator 41
Ke 1〆point; open 35. As a result, one integrator force of 400 Å is lost, so the integration operation is stopped.

Therefore, the output signal of the low value priority circuits 32 and 18 becomes equal to the output signal of the integrator 40, and the opening degree of the steam control valve 3 is kept in a constant condition.

Mode 4) When the main steam pressure is restored and the steam control valve is opened manually, close the 1,000-hour switch.

While the manual switch 38 is closed, the integrator 40 continues to perform the integrating operation, and the steam control valve 3 gradually opens in accordance with the output of the integrator 40.

Mode 5) The output of the integrator 40 is the limit signal from the speed regulation rate circuit 17 of the speed control section, or the load +111 limiter 1
When it becomes larger than the limit signal from 9, the low value priority circuit 1
8, the opening signal of the steam control valve 3 shifts to the speed + h7 regulation rate circuit 17 or the limit side signal from the negative idj limiter 19, and in this state, the comparator 12 closes the contact 36. , the integrator 40Iri begins to follow the output of the adder 34. The output of the integrator 40 and) Nomit (!i circuit; 3
When the blade of 1 is in the 7 state, the comparator 4I closes the contact 35, and the state is restored to the 1" line during normal diving operation.

Figure 4'3? The operation when the main steam output decreases during the alternation of the equipment shown in FIG. 5 is the same as the operation of the device 4 shown in FIG. Interrelationship of opening degree c'v (as shown in figure dit6, the point where each becomes the minimum value after time t8.t!lt3 is the same as in figure 3 (see mode 2),
However, at the time of tz, the main steam) Mocha PO is reduced once again, and the IPR is adjusted accordingly: (Even if the output A of OB starts to increase, the operation of the integrator 40 has stopped, so the steam The valve opening signal (d becomes the output C of the integrator 4o (see mode 3), and at time t; 90% of the main steam pressure rated value (
P^), and the output 'A becomes the steam control valve Ifll circulation opening degree (CVo). At time L6', the manual switch 8 is closed to cause the integrator 1o to perform an integral operation, and the steam control valve opening signal is fully increased (mode 4). At time t7, when the output C of the integrator 40 reaches the limit signal B from the speed control section or load limiter 19, the opening signal of the steam control valve 3 shifts to the output B. From this point on, the output C of the integrator 40 begins to follow the output of the IPR 30B, and the following operation is completed at the time ts (mode 5).

〔Effect of the invention〕

As described in detail below, according to the present invention, once the steam regulator valve is throttled due to a decrease in the main steam pressure supplied to the steam turbine, the steam regulator valve remains in the throttled state even if the main steam pressure recovers thereafter. During this time, the cause of the pressure drop can be investigated, and after confirming that there is no turning, the steam control valve can be opened while checking the main steam pressure5. It is possible to prevent cold air and water from flowing into the steam turbine, thereby preventing secondary disasters caused by such cold air and water flowing into the steam turbine.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional steam turbine control device with an inlet steam pressure drop prevention control device, and Fig. 2 shows the inlet steam pressure drop prevention control device in Fig. 1! Figure 3 is a diagram showing the characteristics of the device shown in Figure 1.
1. Fig. 4 is a block diagram showing an embodiment of the present invention, Fig. 5 is a wiring diagram showing a specific configuration example of the main parts of the device shown in Fig. 4, and Fig. 6 shows the operation of the device shown in Fig. 4. FIG. 3 is a diagram for explaining characteristics. 3...Steam control valve, 4...High pressure turbine, :30A
...Inlet steam pressure drop prevention control device, [3...Speed detection pickup, 15...Speed/load setting device, 1
6. ;49. ．． 34°; 37...Additional angle, 17...
・Speed; W adjustment rate circuit, 18. ．． 42...Low value priority circuit, ■9...Load limiter, 27...Pressure detector, public
...Pressure setting device, 30...Pressure adjustment rate circuit; (1.
・Limit circuit 1.33 ・Exclusion circuit: 34A・
...Automatic follow-up circuit, 35, :36...Break contact,
38...Manual switch 5, 39...Manual setting device 540
...integrator, 41. /12... Comparator - Applicant's agent Inomata Kiyoshi 1 Figure 56

Claims (1)

[Claims] 1. A speed control circuit that outputs a steam control valve opening signal so that the steam turbine reaches a predetermined rotational speed, and prevents cold air and water from flowing into the steam turbine due to a drop in inlet steam pressure. and an inlet steam pressure drop prevention control device that outputs a control signal to throttle the steam control valve when the inlet steam pressure decreases below a predetermined value.
f, a first means for preventing the opening operation of the steam control valve by the inlet steam pressure drop prevention control device when the inlet steam pressure decreases and recovers; and second means for opening the steam control valve by manual control. 2. The first means includes an automatic follow-up circuit including an integrator that stores an output control signal of the inlet steam pressure drop prevention control device, and a signal stored in the automatic follow-up circuit and the inlet steam pressure drop prevention device d. and a first low-value priority circuit that passes a low-value signal of the output control signal, and the output signal of the first low-value priority circuit and the steam control valve opening from the speed control circuit. Claim 1, characterized in that the opening degree of the steam control valve is controlled by the output signal of a second low value priority circuit that passes the lowest signal of the signal and the limit signal from the load limiter. The steam turbine control device according to item 1. 3. The first means includes a first break contact provided in series on the input side of the integrator, a second break contact connected in parallel to the first break contact, and a second break contact provided in series on the input side of the integrator; a first comparator that compares the level of the output signal of the pressure drop prevention control device with the level of the signal stored in the automatic follow-up circuit, and opens the first break contact when the former is higher than the latter; a second comparator that compares the output signal level of the first low value priority circuit and the output signal level of the speed control circuit, and opens the second break contact when the former is lower than the latter; 1, such that when both the first play contact and the second break contact open, the integration operation of the integrator is stopped and the automatic follow-up function of the automatic follow-up circuit is stopped; The steam turbine control unit according to claim 2, characterized in that:
t.