JPH034722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rapid startup characteristic mitigation device for a turbine that prevents sudden transient changes from occurring during startup, especially in turbines that require rapid startup.

[Technical background of the invention and its problems]

For example, in a reactor isolation cooling system that removes heat from the reactor when the reactor is isolated due to an abnormality in the reactor system in a boiling water nuclear power plant and the turbine system is no longer able to remove heat. The system uses steam generated from a nuclear reactor to rotate a small turbine-driven pump that supplies water from a condensate storage tank to the reactor to remove heat. Turbines used in such reactor isolation cooling systems are required to start up quickly (within 30 seconds) due to their functionality.

Generally, a turbine is started or stopped by opening and closing a turbine inlet valve. If the steam or gas supplied to the turbine is at extremely high pressure, the rotational speed of the turbine will rise rapidly in a short period of time.
A regulating valve is provided between the turbine inlet valve and the turbine to adjust the flow rate of steam or gas.

If the change in turbine start-up is too rapid, the regulating function of the regulator valve cannot keep up and the turbine may overspeed, resulting in a turbine trip signal. Even before a turbine trip signal is generated, the load applied to the turbine, control valve, etc. is extremely large.

In particular, when the turbine is required to have a short time from generation of the turbine start signal to reaching the rated operation of the turbine, the change at the time of starting the turbine tends to be abrupt, so conventional methods have been insufficient.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances.In particular, in turbines that require rapid startup, the rapid startup characteristics of the turbine are relaxed within a range that does not impair its functionality, thereby preventing sudden transient changes during startup. It is an object of the present invention to provide a rapid startup characteristic mitigation device for a turbine that eliminates the possibility of generating a turbine trip signal.

[Summary of the invention]

The device for alleviating the quick start characteristics of a turbine according to the present invention is intended to alleviate the quick start characteristics of a turbine that is particularly required to start quickly within a range that does not impair its functionality.
In a conventional turbine steam or gas supply system that supplies steam or gas to a turbine via a turbine inlet valve and a control valve, a new pipe diameter is A relatively small bypass line is provided, a bypass valve and a flow restriction orifice are attached to the bypass line, and a timer is inserted into the turbine start signal transmission circuit to the turbine inlet valve, and the turbine start signal is transmitted to this timer. Therefore, the control valve is transmitted to the turbine inlet valve after a set time delay, and when the turbine inlet valve opens and steam flows into the turbine, the control valve changes from a fully open state to a fully closed state, and then begins to open again to close the turbine. The amount of steam flowing into the turbine is controlled so that the turbine speed is at the rated speed.

Therefore, in the device for alleviating the rapid startup characteristic of a turbine according to the present invention, the bypass valve is first opened by the turbine startup signal, and steam or gas is supplied to the turbine via the bypass line including the flow rate limiting orifice. The turbine inlet valve opens for the first time after a certain time delay, and the regulating valve is then automatically controlled to ensure that the turbine reaches its rated speed within a specified time.

[Embodiments of the invention]

An embodiment of the turbine rapid startup characteristic mitigation device according to the present invention will be described with reference to FIG.

Figure 1 shows a steam-driven turbine 1 used in the reactor isolation cooling system of a boiling water nuclear power plant.
This is a circuit diagram when the quick start characteristic mitigation device according to the present invention is adopted, and steam led from the main steam pipe (not shown in the drawing) is supplied to the turbine 1 via the turbine steam pipe line 2 with a nominal diameter of 100A, The turbine steam line 2 is provided with a turbine inlet valve 3, which is an electric globe valve, and is normally closed to shut off steam. Further, a trip throttle valve 4 which is an electric gate valve and a control valve 5 which is a hydraulically driven gate valve are provided between the turbine inlet valve 3 of the turbine steam pipe line 2 and the turbine 1. The control valve 5 is normally in a fully open state.

The above is the configuration of the conventional turbine steam supply system, but as a turbine rapid start characteristic mitigation device according to the present invention, the turbine inlet valve 3
A bypass pipe 6 with a nominal diameter of 25A is connected in parallel to the turbine inlet valve 3, and a flow-limiting orifice 7 with an orifice diameter of 10 mm is connected to the bypass pipe 6, and an electric globe valve is connected to the upstream side of the bypass pipe 6. A bypass valve 8 is provided, and the bypass valve 8 is normally closed to cut off steam. Further, a turbine inlet valve 3 to which a turbine start signal etc. is guided.
A timer 10 is included in the turbine start signal transmission circuit 9 to
Insert the turbine start signal into this timer 10.
is guided to the turbine inlet valve 3 after a certain period of delay, and the turbine inlet valve is opened.

In the turbine rapid start characteristic mitigation device according to the present invention shown in FIG. 1, in a normal state, the turbine inlet valve 3 and the bypass valve 8 are closed and steam is cut off, so the turbine 1 is stopped. There is. At this point, the trip throttle valve 4 and the control valve 5 are fully open.

When the turbine start signal is issued, first, the bypass valve 8 opens and steam begins to flow to the turbine 1 via the bypass pipe 6, but at this time, the flow rate of steam is throttled by the flow rate limiting orifice 7. Also, since the bypass line 6 is thinner than the turbine steam line 2, the change in steam flow rate becomes more gradual than when the turbine inlet valve 3 is suddenly opened. On the other hand, the turbine start signal is guided to the turbine inlet valve 3 with a delay of a set time (for example, 3 seconds) by the timer 10, and the turbine inlet valve 3 starts to open after the bypass valve 8 by the set time of the timer 10. When this turbine inlet valve 3 is opened and steam begins to flow into the turbine 1, the regulating valve 5 is automatically controlled separately, and its opening is changed from the fully open state at the moment the turbine start signal is issued to the initial abrupt state. In order to avoid the influence of steam inflow, the turbine is fully closed for a short period of time, and then begins to open again after a short period of time, and the opening is controlled so that the turbine speed reaches the rated speed for a specified time (30 seconds).
Within a short time the turbine speed reaches the rated speed. This state is illustrated in graphs as shown in FIGS. 2 and 3. Figures 2 and 3 are shown in Figure 1, respectively.
Changes in the opening degree of the regulator valve 5 (Figure 2) and changes in the turbine speed (Figure 3) at the time of turbine startup, regarding the case where the turbine rapid start characteristic mitigation device according to the present invention is used and the conventional case where it is not used. The change in the opening degree of the regulating valve 5, and therefore the change in the turbine speed, is gradual compared to the conventional one.
What's more, it reached its rated speed within the specified 30 seconds. Therefore, by using the device for alleviating the rapid startup characteristic of a turbine according to the present invention, there is no possibility of generation of a turbine trip signal during a rapid startup.

〔Effect of the invention〕

As described in detail in the previous section regarding the embodiments of the turbine rapid startup characteristic mitigation device according to the present invention,
Bypassing the turbine inlet valve, which starts or stops the turbine by opening and closing the valve, a bypass line including a flow-limiting orifice is provided, and in response to a turbine start signal, the flow-limiting orifice is first passed through the bypass line. Steam is supplied to the turbine while throttling the flow rate to slow down the initial change in steam flow rate, then the turbine inlet valve is opened after a certain period of time, and the regulating valve is automatically controlled from then on to increase the turbine speed within a specified period of time. Since the system allows the turbine to reach its rated speed, the rapid startup characteristics are relaxed, especially for turbines that require rapid startup, and there is a possibility that a sudden transient change will occur during startup and a turbine trip signal will be generated. This has the effect of maintaining the integrity of component equipment such as turbines and regulating valves.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a turbine rapid startup characteristic mitigation device according to an embodiment of the present invention, and FIGS.
The figure shows the change in the opening degree of the control valve at the time of turbine startup (second
Fig. 3) is a graph showing changes in turbine speed (Fig. 3). 1...Turbine, 3...Turbine inlet valve, 5...
...Adjustment valve, 6...Bypass pipe line, 7...Flow rate limiting orifice, 8...Bypass valve, 10...Timer.

Claims (1)

[Claims] 1. A turbine inlet valve disposed in a turbine steam pipe line that guides steam to the turbine; a bypass pipe bypassing the turbine inlet valve and formed with a pipe diameter smaller than that of the turbine steam pipe line;
a bypass valve disposed in the bypass conduit and opened in response to a turbine start signal; a flow rate limiting orifice disposed downstream of the bypass valve to throttle the amount of steam flowing into the bypass conduit; and a flow rate limiting orifice disposed downstream of the bypass valve; a timer for guiding an open signal to the turbine inlet valve after a predetermined time after the opening operation of the turbine; 1. A rapid start-up characteristic relaxation device for a turbine, comprising a control valve that is fully closed and then begins to open again to control the amount of steam flowing into the turbine so that the speed of the turbine becomes the rated speed.