JPS62147003A - Load anticipator device - Google Patents

Abstract

PURPOSE:To hold down the increase ratio of the number of revolutions, by inputting a dummy signal to an electronic hydraulic governor for a certain time when a load interrupting signal is detected, and closing an adjusting valve rapidly. CONSTITUTION:The signal of a timer 11 which responses to a detected signal from a load interrupting signal detection circuit 10 is inputted to the shutdown circuit 7 of an electronic hydraulic governor 12 which controls a steam adjusting valve 2. The timer 11 generates the signal for a prescribed time after the load interruption is detected, and actuates the shutdown circuit 7 so as to minimize the output thereof. Thus, the output of the shutdown circuit 7 is inputted to a servomotor and electro-hydraulic converter 3 via a low signal selector 5 so as to fully close the adjusting valve 2. Therefore, the increase of the number of revolutions can be held down faster than the response speed of a controller 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a load anticipator device applied to a steam turbine using an electro-hydraulic governor system.

BACKGROUND OF THE INVENTION In a steam turbine employing an electro-hydraulic governor system, when a load shedding phenomenon occurs during operation of the steam turbine, the rotation speed of the turbine increases due to the excess steam. The speed at which the rotational speed increases is determined by the moment of inertia of the steam turbine and the driven machine. Steam turbines have become faster and have larger capacities, and the moment of inertia has become smaller compared to the output (as a result, the response characteristics of the electro-hydraulic governor's rotation speed detection show that the rate of increase in rotation speed during load shedding is high ( This may cause an overspeed trip.

The determination of whether the moment of inertia of the steam turbine and driven equipment is large or small is determined by the starting time TA, that is, when steam equivalent to the full load is instantaneously injected into the turbine, the rotation speed of the turbine changes from Orpm to rated rotation. It is a value that represents the time it takes to reach a number, and usually TA≧
It is determined that the moment of inertia is large when the time is about 6 seconds, and the moment of inertia is small when TA<6 seconds.

Problems to be Solved by the Invention When the moment of inertia is small, the rate of increase in turbine speed during load shedding is high (and there is a possibility of overbead tripping), but with conventional electro-hydraulic governors, only the response speed is Therefore, the rotation speed increase rate at the time of load shedding is within the range that does not cause an overspeed trip (usually 109 of the rated rotation speed).
% or less).

Therefore, an object of the present invention is to suppress the rotational speed increase rate by adding an external sequence to the electrohydraulic governor, regardless of the response characteristics of the electrohydraulic governor.

Means for Solving the Problems According to the present invention, a load shedding signal detection circuit and a timer are provided, and when a load shedding signal is detected, a simulated signal is input to the electro-hydraulic governor to quickly close the steam control valve. This prevents the inflow of excess steam and suppresses the rate of increase in rotation, and after a certain period of time after responding to the load cutoff signal, the input of the simulated signal is canceled and the control state is returned to the electrohydraulic governor. A load anticipator device is provided.

Example A preferred embodiment of the invention will be described with reference to FIG.

The steam turbine 1 is controlled by signals from a controller 6 in an electronic governor 4 via a steam control valve 2, a servo motor, and an electro-hydraulic converter 3.

The output of the shutdown circuit 7 in the electronic governor 4 is higher than the output of the controller 6 in the control state of normal operation and is therefore shut off by the low signal selector 5.

The controller 6 detects the rotational speed of the steam turbine 1 and controls the steam control valve 2 so that the rotational speed is constant. In the conventional electro-hydraulic gas pump, when a load shedding occurs, it is necessary to detect the fact that the rotation speed has increased and then suppress (control it), but in the present invention, the load shedding signal detection circuit 10 and the timer 11 are used. At the time of load shedding, the load shedding signal detection circuit 10 detects the load shedding signal, and the shutdown signal generation circuit 9 detects the shutdown circuit 7 of the electronic governor 4.
is operated so that its output is minimized.

As a result, the output of the shutdown circuit 7 has a lower value than the output of the controller 6, and therefore is given priority over the signal of the controller 6 by the low signal selector 5.

The steam control valve 2 is unilaterally fully closed via the servo motor and the electro-hydraulic converter 3. As a result, the increase in rotational speed can be suppressed faster than the response speed of the controller 6.

The output of the load shedding signal detection circuit 10 is also connected to a timer 11 and responds to the detection of a load shedding signal. timer 11
When a predetermined time period set in advance has elapsed since the detection of the load cutoff signal, it outputs a reset signal, and this reset signal is input to the shutdown circuit 7 via the reset circuit 8. Then, the /yat-down circuit 7 releases the low value signal that has been supplied since the detection of the load cutoff signal, and as a result, the steam speed is increased or decreased faster than the controller 6 detects the increase in rotation speed and controls it. With the valve 2 closed, the rate of increase in rotational speed can be suppressed to a lower rate than when only the electrohydraulic governor 12 is used.

Effects of the Invention According to the present invention, as can be seen from the response characteristics shown in FIG. 2 in comparison with the conventional case, in the past, the rate of increase in rotational speed at the time of load interruption could only depend on the response characteristics of the electro-hydraulic governor. This was determined solely by the characteristics of the governor, but the load anticipator device controls the steam control valve faster than the response of the governor characteristics, making it possible to keep the rate of increase in rotational speed low.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a steam turbine electro-hydraulic governor to which a load anticibator device according to the present invention is applied, and FIG. 2 is a diagram illustrating response characteristics at the time of load interruption. l...Steam turbine, 2...Steam control valve, 3...Servo motor and electro-hydraulic converter, 4...Electronic governor, 5...Low signal selector 6** Controller, 7...Shutdown circuit, 8... Reset circuit, 9...Shutdown signal generation circuit, 10...Load cutoff signal detection circuit, 11...
Timer, 12...electrohydraulic governor.

Claims (1)

[Claims] In a steam turbine control system in which a steam control valve is controlled by an electro-hydraulic governor composed of an electronic governor, a servo motor, and an electro-hydraulic converter, a load cutoff signal is detected and the steam control valve is controlled by the electronic governor. A load anticipator device comprising: a load shedding signal detection circuit that generates a signal to close a valve; and a timer that releases the closing signal after a predetermined time in response to detection of the load shedding signal.