JPS5821720B2 - Reactor feed water pump overload protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overload protection device for a reactor feed water pump in a nuclear couplant.

Generally, a nuclear coupler plant is equipped with a reactor feed water control device to control the reactor water level within a predetermined range, and the feed water control device controls the turbine speed and the motor-driven water pump system. The water level is controlled by controlling the opening degree of the water supply regulating valve.

By the way, if the reactor pressure suddenly decreases or an excessive demand for water supply flow occurs, the feedwater pump may run out and become overloaded, causing cavitation to occur due to a drop in the effective suction head, etc. Pump may be damaged.

Therefore, in the past, especially in electric motor-driven feedwater pumps, when the reactor pressure suddenly decreased or an excessive water supply flow rate was required as mentioned above, a water supply regulating valve installed on the downstream side of the water supply pump was used. A protection method is adopted that reduces the water supply flow rate by throttling the water.

That is, FIG. 1 is a schematic system diagram of a conventional overload protection device for a feed water pump. Cooling water is supplied to the reactor 1 by a feed water pump 2 via a feed water regulating valve 3 provided on the downstream side thereof. The steam generated in the reactor 1 is transferred to the conduit 4
It is supplied to a heat exchanger (not shown) or the like via a heat exchanger (not shown).

A main steam flow rate detector 5 and a feed water flow rate detector 6 are provided downstream of the conduit 4 and the feed water regulating valve 3, respectively, and a detection signal from the rain detector is applied to the reactor feed water control circuit 7. has been done.

A water level signal from a reactor water level detector 8 is also added to the reactor feed water control circuit 7, and each signal basically operates a main water level controller 9, and a manual/automatic switch 10. , control signal switch 11, and regulating valve electropneumatic converter 1
2 to control the water supply regulating valve 3.

Therefore, when the water supply pump 2 runs out and the water supply flow rate increases rapidly, the pump overload detector 13 is activated by the water supply flow rate signal detected by the water supply flow rate detector 6, the control signal switch 11 is switched, and the flow rate controller 14 is activated. A signal is transmitted to the regulating valve electro-pneumatic converter 12, and the water supply regulating valve 3 is controlled so that the water supply flow rate becomes a constant flow rate determined by the flow rate setting device 15.

However, since the above-mentioned protection device controls the water supply flow rate to be constant as described above, there is a possibility that the water supply will flow regardless of the pressure conditions on the discharge side of the water supply pump, and it is not effective in protecting the pump. The necessary suction pressure or discharge pressure may not be secured, and since the normal control circuit is returned only after the water level in the reactor has recovered, water supply may continue unnecessarily during that time, resulting in supercharging water, etc. There were some inconveniences.

In view of these points, the present invention has been developed to reduce the suction pressure or discharge pressure necessary to protect the pump when the load resistance of the feedwater pump decreases due to a sudden pressure drop due to trouble in a nuclear reactor, or when an overload is requested of the feedwater pump. In addition to ensuring water supply to the reactor, it also protects the water pump by preventing pump vibration and cavitation caused by pump overload.

The purpose is to provide an overload protection device for water pumps.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4.

In FIG. 2, a turbine-driven water pump is used as the water supply pump, and the water supplied by the water supply pump 2 driven by the turbine 16 is supplied to the nuclear reactor 1 through the water supply regulating valve 3, and then The generated steam is transferred to conduit 4
The steam is then sent to a heat exchanger (not shown) for appropriately generating steam for driving the main turbine.

On the other hand, the feed water turbine governor 1T that controls the turbine 16 receives detection signals from the main steam flow rate detector 5, the feed water flow rate detector 6, the reactor water level detector 8, etc., and generates control signals. Signals from the reactor feedwater control circuit 7 are applied to control the turbine 16 by the feedwater turbine governor 17.

Further, a pump overload detection pressure switch 18 is provided on the downstream side of the water supply pump 2. When an overload of the water supply pump 2 occurs, it is detected by the pressure switch 18, and a signal from the pressure switch 18 is used to pump the water supply pump 2. The overload protection controller 19 is activated and an output signal is generated from the water pump overload protection controller 19.

A signal from a pressure detector 20 that monitors the discharge pressure of the water supply pump and a setting signal from an overload protection setting device 21 are input to the water supply pump overload protection controller 19, and this deviation signal indicates a low value. The signal is applied to the priority device 22.

The low value priority device 22 receives an output signal from the reactor feed water control circuit 7 and a regulating valve position setting device 23 for controlling the feed water regulating valve 3 so that the regulating valve 3 does not become wide open during normal operation. A setting signal is also added, and the minimum signal of each signal is applied to the regulating valve controller 24, and the opening degree of the water supply regulating valve 3 is controlled via the regulating valve electro-pneumatic converter 12. There is.

However, if an overload occurs on the water supply pump under some circumstances, a flow rate greater than the flow rate determined by the water head/flow rate customization of the water supply pump and the normal system head will flow, and the discharge pressure of the water supply pump will inevitably drop suddenly.

When the discharge pressure suddenly decreases in this way, this is detected by the pump overload detection pressure switch 18, and the water supply pump overload protection controller 19, which is on standby at the upper limit of the output, is activated, and the water supply pump discharge pressure and the allowable during operation are activated. A deviation signal from the set signal, which is set to a value that is the lowest possible pressure and avoids normal fluctuations, is transmitted to the low value priority device 22.

That is, in this case, since the discharge pressure of the water supply pump becomes equal to or lower than the set value of the overload protection setting device 21, a control signal in the direction of recovering the discharge pressure is transmitted to the low value priority device 22.

When the output signal from the overload protection controller 19, which is compared with the other two signals in the low value priority device 22, becomes smaller than the other signals, it takes priority over the other signals and becomes the output signal of the low value priority device. , is applied to the regulating valve controller 24, and the water supply regulating valve 3 is controlled in the throttle direction via the regulating valve electro-pneumatic converter 12.

This operation continues until the pump discharge pressure signal from the water pump discharge pressure detector 20 becomes equal to the set value.

In this state, when the discharge pressure of the water supply pump is restored and the output signal of the overload protection controller 19 becomes larger than the other two signals, the control of the regulating valve 3 by this signal is controlled by the low value priority device 22.
automatically canceled by the function.

Furthermore, even if the signal from the overload controller 19 gives priority to the control valve control via the low value priority device, if the signal from the reactor feed water control circuit 7 requests an even lower flow rate, This signal gives priority to controlling the water supply regulating valve 3, thereby preventing superfeeding of water to the reactor when unnecessary.

Therefore, when the pump discharge pressure recovers sufficiently, the pump overload detection pressure switch 18 is activated and the water supply pump overload protection controller 19 is automatically released.

Next, FIG. 3 shows a comparison of responses between the conventional method and the device of the present invention.

(a) is a conventional system; in this case, there is almost no protection circuit for the turbine-driven water supply pump system, so a motor-driven water supply pump system is shown.

Therefore, in conventional equipment, when the water supply pump enters a runout state for some reason, the overload protection circuit works to keep the pump discharge flow rate constant, and the water level does not rise unless the circuit is manually released midway through. Then, only when the water level rises to a point where it can be determined that water supply to the reactor is no longer necessary, the protection circuit is automatically released and control returns to the normal water supply control circuit.

Therefore, the water level may overshoot as shown in (a).

On the other hand, (b) shows the response according to the present invention under similar conditions, and when pump overload is detected, the overload protection controller is activated and the discharge pressure of the water pump is restored. .

During this period, if the output signal of the water supply control circuit becomes smaller than the signal of the overload protection controller due to the rise in the water level, the signal of the water supply control circuit takes priority and throttles the water supply regulating valve.

Therefore, further efforts are made to recover the pump discharge pressure,
A nearly ideal response can be obtained without the occurrence of a supercharged state caused by the water supply pump.

In the above embodiment, a turbine-driven water supply pump system has been described, but as shown in FIG. 4, the present invention can also be applied to an electric motor-driven water supply pump system.

However, in this case, since only the control is performed by the water supply regulating valve, the regulating valve position setter 23 in the low value priority device is not necessary.

Furthermore, the protection device of the present invention may be provided in the lines of individual water pumps, or may be provided in the entire water pump system.

Further, in the above embodiments, the overload state is detected using the water supply discharge pressure, but the overload state may be detected using the suction pressure of the pump.

Since the present invention is configured as described above, it is possible to properly protect the water supply pump even in the water supply system of a turbine-driven water supply pump, which is not conventional, and it is also possible to ensure an effective suction head. Moreover, it is possible to perform control within the normal operating water level range of the reactor without causing supercharging of water to the reactor due to pump protection.

Furthermore, when the protection circuit is in operation, priority control is also performed by the normal control circuit, which provides effects such as being able to protect the water supply pump from overloading under conditions close to ideal.

[Brief explanation of drawings]

Fig. 1 is a schematic system diagram of a conventional water pump overload protection device, Fig. 2 is a schematic system diagram of a water pump overload protection device of the present invention, and Fig. 3 a and b are diagrams of the conventional and inventive protection devices. A comparison diagram showing the response, and FIG. 4 is a system diagram showing another embodiment of the present invention. 1...Nuclear reactor, 2...Water pump, 3
... Water supply adjustment valve, 7 ... Reactor feed water control circuit, 1B ... Pump overload detection pressure switch, 19 ... Water pump overload protection control vessel, 2
0...Water pump discharge pressure detector, 21...
. . . Overload protection setting device, 22 . . . Low value priority device, 24 . . . Regulating valve controller.

Claims (1)

[Claims] 1. A water supply pump overload protection controller that is activated by a pump overload detection device and generates a deviation signal between a pressure signal of the discharge pressure or suction pressure of the water supply pump and a setting signal from the overload protection setting device; A signal from the pump overload protection controller and a signal from the reactor feed water control circuit are applied, and a low value priority device generates only the low value signal as an output signal, and is activated by the signal from the low value priority device. An overload protection device for a reactor feed water pump, comprising: a regulating valve controller that controls a regulating valve disposed downstream of the feed water pump.