WO1998014843A1

WO1998014843A1 - Monitoring device for a controlling mechanism in the admission of a propulsion medium of a turbine, specially a gas turbine

Info

Publication number: WO1998014843A1
Application number: PCT/DE1997/002222
Authority: WO
Inventors: Gerhard RÜHL
Original assignee: Siemens Aktiengesellschaft
Priority date: 1996-09-30
Filing date: 1997-09-26
Publication date: 1998-04-09
Also published as: DE29617014U1

Abstract

The invention concers a monitoring device (7) comprising a signal converter (2) having at least a derivative response characteristic (DT1), to which the actual position value (1) of the control element (33, 35) is passed. At least the signal (6) at the output of the first signal converter (2) and the control signal (13) determined for the control element (39; 33, 35) are passed on to a logical evaluation circuit, which produces at least a malfunction warning signal (18) when the signal (6) at the output of the first signal converter (2) indicates no value even though a control signal (13) exists.

Description

description

Monitoring device for an actuating device in the feed of the drive medium of a turbine, in particular a gas turbine

Turbines have actuating devices with which the supply of the drive medium to the turbine is regulated. The actuators generally contain an actuating element for the drive medium, in particular an actuating valve, and an associated position control loop for the actuating element. Faults, particularly in the position control loop for the control element, must be recognized quickly and reliably. This is particularly true for gas turbines. Since these are often operated in one working point in which the maximum load capacity of the

Turbine materials and the compressor's limit performance, the so-called surge limit, has almost been reached, the turbine must be able to be regulated precisely at any time by means of the corresponding control element. Malfunctions in the control element or the associated position control loop must be recognized immediately and possibly by a manual intervention in the scheme can be compensated. Otherwise permanent damage to the turbine can occur.

Turbine drive medium actuator malfunctions can have various causes. On the one hand, e.g. due to a failure of the positioner, the control signal provided for the control element is missing at the output of the positioner. On the other hand, the one supplied to the positioner

Actual position value e.g. due to a defect in the position sensor on the control element. Finally, there may also be faults inside the actuator itself, e.g. mechanical jams.

The invention has for its object to provide an electrical monitoring circuit, with which the occurrence of Malfunctions of the actuator can be recognized quickly and safely.

The object is achieved with a monitoring device according to claim 1. Further advantageous embodiments of the invention are specified in the subclaims.

The invention is explained in more detail on the basis of exemplary embodiments shown in the figures briefly listed below. It shows

1 shows a basic illustration of the control device for a turbine with positioner and control element, and a basic circuit diagram of the monitoring device according to the invention,

2: the block diagram of a first embodiment of a logic evaluation circuit in the monitoring device according to the invention,

3 shows a further, advantageous two-channel version of the monitoring device according to the invention.

In the overview circuit diagram in FIG. 1, a basic illustration of a gas turbine is shown by way of example under reference numeral 24. This has a combustion chamber 27 which is supplied with a drive medium via a feed 32, i.e. a combustion gas. The combustion chamber 27 is additionally supplied with combustion air from the left-hand side via a feed 25 and a compressor 26. On the right

The actual turbine part 28 adjoins the combustion chamber 27, which quasi ends with the gas outlet 29. Compressor 26 and turbine part 28 are generally connected to a generator 31 via a turbine shaft 30. An adjusting device 39 for the drive medium of the turbine is arranged in the feed 32. This contains an actuator 33 for the drive medium, in particular a hydraulic valve, and a hydraulic or electric actuator 35 for the actuator 33.

A position control circuit generates an actuating signal 13, which acts on the actuator 35 of the actuating device 39. The position control circuit contains a position controller 34, to which the deviation of an actual position value 1 and a position setpoint 36 tapped at the valve 33 for the gas supply 32 of the gas turbine 24 is supplied. A control signal 13 for the control valve 33 is finally formed at the output of the positioner 34.

The monitoring device 37 according to the invention for the adjusting device consisting of the position control circuit and the adjusting element 39 has a signal converter 2 which has at least a differentiating transmission behavior, i.e. at least a so-called DTI behavior. The position transducer 1 is supplied to the signal converter 2 at the output of the actuating element 35 as an input variable. The monitoring device 37 according to the invention also contains a logic evaluation circuit 38. These are at least the signal 6 at the output of the signal converter 2 and that for the

Control element 35 in the control device 39 certain control signal 13 supplied. According to the invention, the logic evaluation circuit 38 generates a fault signal 18 at the output by comparing the two input signals 1 and 13 at least when, despite the presence of an actuating signal 13, the signal 6 at the output of the signal converter 2 has no appreciable amount. In this way, a divergence between control signal 13 and actual position value 2 can be detected quickly and reliably. If, for example, the monitoring device 37 detects the occurrence of a control signal 13 without a corresponding change in the actual position value 1, detected by an output signal 6 on the signal converter 2, a fault signal 18 is emitted.

In a further embodiment of the invention shown in FIG. 2, the logic evaluation circuit 38 has, as further elements, a first and a second minimum value detector 7 and 14. The first minimum value detector 7 is supplied with the signal 6 at the output of the signal converter 2. The minimum value detector 7 outputs at least one active first binary signal 8 at the output when the supplied signal 6 has an amount that is greater than a first minimum value. In practice, a threshold of approximately 5% of the measuring range can advantageously be specified as the first minimum value. The control signal 13 intended for the actuating device 39 or its actuator 35 is fed to the second minimum value detector 14. The minimum value detector 8 outputs at least one active second binary signal 9 at the output if the supplied control signal 13 has an amount that is greater than a second minimum value. In practice, a threshold of approximately 25% of the measuring range can advantageously be specified as the second minimum value. A logic comparison circuit 17 following the two minimum value detectors 7 and 8 generates a fault signal 18 at least when the first binary signal 8 is inactive and the second binary signal 9 is active.

In the example of FIG. 2, the logic comparison circuit 17 contains at least one logic AND gate, to which the first binary signal 8 at the output of the first minimum value detector 7 is supplied in inverted form and the second binary signal 9 at the output of the second minimum value detector 8 in unchanged form become. An actuating signal 13 with a sufficient size lying above a background noise is detected by an active second binary signal. An active fault signal 18 then appears at the output of the logic AND gate 17 of the logic comparison circuit when, in such a case, the detection of the absence of a change in the actual position value 1 causes an inactive state of the first binary signal 8.

Further advantageous additions to the monitoring device according to the invention are explained in more detail below with reference to the circuit shown in FIG. 3.

In an advantageous, further embodiment of the invention, the logic evaluation circuit 38 of the monitoring device has two separate monitoring channels for separate monitoring of the actuating device 39 in the event of a positive actuating movement in the direction of the open or a negative actuating movement in the direction of the closed state. Such an embodiment is already shown in the example in FIG. 3, the signal channel for positive positioning movements being provided with the reference symbol 40 and the signal channel for negative positioning movements being provided with the reference symbol 42. At the output of the logic comparison circuit 17, a first logic signal 41 is then generated from these signal channels when there is a positive actuating movement of the actuating element and a second logic alarm signal 43 when there is a negative actuating movement of the actuating element. The two logic signal signals 41, 43 at the output of the monitoring channels 40, 42 are finally combined via a logic gate, in particular a logic OR gate 21, to form the fault signal 18.

It is advantageous if in this embodiment of the invention both minimum value detectors 7 and 14 each have a two-channel output, each providing a pair of binary signals 81, 82 and 91, 92, respectively. So the binary sig- signals 81 or 91 at the output of the minimum value detector 7 or 14 are active if a positive change 6 of the actual position value is exceeded by exceeding a positive threshold value of e.g.> 5% and a positive change of the control signal 13 for by exceeding a positive threshold value of e.g.> 25% the actuator is detected. On the other hand, the binary signals 82 and 92 at the output of the minimum value detector 7 and 14 are active if a negative change 6 in the actual position value is undershot by falling below a negative threshold value, for example, and a drop below a negative threshold value of, for example,> -25% negative change in the control signal 13 for the actuator is detected.

The two minimum value detectors 7, 14 thus each generate a pair of first and second binary signals 81, 82 and 91, 92, respectively, a signal from each pair, in the example of FIG. 3, the signals 81 and 91, when the actuating element moves 39 in the direction of the open state and the other signals of the pairs, in the example of FIG. 3 the signals 82 and 92 are active when the actuating element 39 moves in the direction of the closed state. The signals 81 and 91, which are active when the actuating element 39 moves in the direction of the open state, are advantageously fed to the first logic comparison means 44, which are in the logic in the first monitoring channel 40

Comparison circuit 17 are arranged. These activate the monitoring device according to the invention in the case of a positive adjusting direction for the generation of a fault signal 18. Furthermore, in the advantageous circuit of FIG. 3, the signals 82 and 92 which are active when the actuating element 39 moves in the direction of the closed state are fed to second logic comparison means 45 which are arranged in the second monitoring channel 42 in the logic comparison circuit. These activate the monitoring device according to the invention in the case of a negative setting direction for the generation of a fault signal 18. According to a further embodiment, which has also already been illustrated in the example in FIG. 3, the monitoring device according to the invention contains means 10 for detecting the reaching of an end position of the actuating element 39 in the open and closed state. In the example in FIG. 3, the actual position value 1 of the actuating element 33 is evaluated by the means 10. The means 10 block the first logical comparison means 44 for generating a fault signal 18 when the end position of the control element 33 is reached in the open state, ie the control element is fully open at the positive stop. For this purpose, the means 10 have a comparator 101 which emits an inactive signal which blocks the first logical comparison means 44 when the actual position value 1 of the adjusting element 33 has exceeded a value of, for example, 98% of the adjusting range. Furthermore, the means 10 block the second logical comparison means 45 for generating a fault signal 18 when the end position of the actuating element 33 is reached in the closed state, ie the actuating element is fully closed at the negative stop. For this purpose, the means 10 have a further comparator 102 which emits an inactive signal which blocks the second logical comparison means 45 when the actual position value 1 of the adjusting element 33 has fallen below a value of, for example, 2% of the adjusting range.

The logic comparison circuit 17 advantageously has delay means which only release a fault signal 18 after a predetermined delay time has elapsed, and otherwise suppress a fault signal 18 at the output of the monitoring device 37 if it has become inactive before the delay time has expired. In the example in FIG. 3, the delay means contain adjustable binary time elements 22, 23, one of which is arranged in each of the first logic comparison means 44 of the first signal channel 40 and one in the second logic comparison means 45 of the second signal channel 42. In the example in FIG. 3 the logic comparison means 44 and 45 each contain a logic AND gate 19 and 20 at the inputs, with which the binary signals 81, 91 and 82, 92 are combined by the minimum value detectors 7 and 14, respectively.

Claims

claims

1. Monitoring device (37) for an actuating device (39, -33, 35) in the supply of the drive medium (32) to a turbine (24), in particular in the gas supply to a gas turbine. or the steam supply of a steam turbine, with

a) a signal converter (2) which has an at least differentiating transmission behavior (DTl) and to which the actual position value (1) of the control element (33, 35) is supplied, and

b) a logic evaluation circuit (38), to which at least the signal (6) at the output of the signal converter (2) and the control signal (13) intended for the control element (39; 33, 35) are fed, and which a fault signal (18) generated at least when, despite the presence of an actuating signal (13), the signal (6) at the output of the first signal converter (2) has no amount (Fig.l).

2. Monitoring device according to claim 1, wherein the logic evaluation circuit (38)

a) a first minimum value detector (7), to which the signal (6) is fed at the output of the signal converter (2) and which outputs at least one active first binary signal (8) at the output if the supplied signal (6) has an amount, which is greater than a first minimum value (5%), and

b) a second minimum value detector (14) to which the control signal (13) intended for the control element (39, -33, 35) is fed and which outputs at least one active second binary signal (9) at the output when the control signal supplied (13) has an amount greater than a second minimum value (25%), and c) a logic comparison circuit (17), which generates the malfunction report signal (18) at least when the first binary signal (8) is inactive and the second binary signal (9) is active (FIG. 2).

3. Monitoring device according to claim 1 or 2, wherein

a) the logic evaluation circuit (38) has two separate monitoring channels (40, 42) for separate monitoring of the control element (39, -33, 35) in the direction of the open and the closed state, and

b) binary signal signals (41, 43) at the output of the monitoring channels (40, 42) are combined via a logic gate (21), in particular a logic OR gate, to form the fault signal (18) (Fig. 3).

4. Monitoring device according to claim 2 and 3, wherein in the logic evaluation circuit (38)

a) the first and second minimum value detectors (7, 14) each generate a pair of first and second binary signals (81, 82; 91, 92), a signal from each pair (81; 91) each time the actuating element moves ( 39; 33, 35) in the direction of the open state and the other signals of the pairs (82; 92) are active when the actuating element (39; 33, 35) moves in the direction of the closed state, and

b) the signals (81; 91) which are active when the actuating element (39; 33, 35) moves in the direction of the open state are fed to the first logic comparison means (19, 22) in the logic comparison circuit (17) and these with a positive adjustment direction activate for the generation of a fault signal (18), and c) the signals (82; 92) which are active when the control element (39; 33, 35) moves in the direction of the closed state are fed to second logic comparison means (20, 23) in the logic comparison circuit (17) and this in the case of a negative adjustment direction Unlock for generating a malfunction signal (18).

5) Monitoring device according to claim 4, with means

(10; 101, 102) for detecting the reaching of an end position of the control element (39, -33, 35) in the open and closed state, which

a) block the first logical comparison means (19, 22) for generating a fault signal (18) when the end position of the control element (33, 3) is reached in the open state, and

b) block the second logical comparison means (20, 23) for generating a fault signal (18) when the end position of the control element (33, 3) is reached in the closed state.

6) Monitoring device according to one of the preceding claims, wherein the logic comparison circuit (17) has delay means (22, 23) which only release a fault report signal (18) after a predetermined delay time has elapsed, and otherwise suppress a fault report signal if this has expired the delay time has become inactive.