JPS62225704A - Overspeed preventing device for turbine - Google Patents

Abstract

PURPOSE:To attain stable operation of a turbine and prevent it from overspeed by rapidly closing a control valve with drain of oil pressure by means of a solenoid valve when the increasing rate and the absolute value of turbine speed exceed predetermined values upon shutting-off of a generator load. CONSTITUTION:A plant delivers steam generated by a steam source 7 through a main steam stop valve 8 to a steam control valve 9, where said steam is adjusted in its flow and led to a turbine 10 to drive a generator 11. And said plant is provided with a rapid valve closing device to prevent said turbine 10 from overspeed by closing said steam control valve 9 rapidly when the load to said generator 11 suddenly decreases. Said rapid valve closing device consists of a rapid valve closing pilot valve 1, a rapid valve closing relay 3, a rapid valve closing piston 5, a rapid valve closing solenoid valve 6, and a lever-link mechanism which connects the above items together. When the speed accelerating rate and the absolute speed of said turbine 10 increase at the same time, said rapid valve closing solenoid valve 6 is energized to drain the upper chamber of said rapid valve closing piston 5 to make said steam control valve 9 close.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbine control device, and particularly to a turbine overspeed prevention device suitable for use in a control valve quick-closing mechanism of a power generation turbine.

[Conventional technology]

An example of the prior art is shown in FIGS. 2 and 4. FIG. 4 shows the system of the turbine plant. The plant is a steam source7. Steam generated in a steam source 7 consisting of a main steam stop valve 8, a steam control valve 9, a turbine 10, and a generator 11 passes through the main steam stop valve, adjusts the steam flow rate with a steam control valve, and then works in a turbine 10. . The kinetic energy of the turbine is converted into electrical energy by a generator. In order to quickly close the steam control valve and prevent the turbine from overspeeding when the load on the generator suddenly decreases, a quick-closing device as shown in FIG. 2 is provided. Quick closing device is valve quick opening pilot valve 1, dashbot 2
, a quick-open valve relay 3, a needle valve 4, and a lever link mechanism connecting them. The right end of the rotating shaft A of this device is connected to a speed-output control device (not shown), which controls the turbine output by changing the turbine speed. - The left end of the right co-rotating shaft is connected to the steam control valve. During normal operation, the turbine speed changes slowly, so the lever B connected to the rotating shaft A also moves slowly, allowing oil to flow back and forth between the upper and lower parts of the dashpot 2 through the needle valve 4. The piston of valve 1 does not move, however.

When a load cutoff or the like occurs and the turbine speed suddenly increases, the rotating shaft A suddenly rotates clockwise and the left end of the lever B is suddenly pulled down. In this case, since the oil at the bottom of the dashbot 2 is being squeezed by the needle valve 4, the movement of the lever B is temporarily greater than the movement of the internal piston, and as a result, the piston of the quick-open pilot valve moves upward. be lifted up. Then, the oil supplied to the lower part of the quick-open valve relay 3 is drained through the pilot valve, the piston in the quick-open valve relay descends, and the left end of the lever C is blown up. As a result, the ring D rotates the rotating shaft A even more rapidly in the clockwise direction, and quickly closes the steam control valve.

An example of a known technique is JP-A-58-211504.

[Problem that the invention seeks to solve]

According to the conventional technology, when the load is cut off, it is possible to quickly close the steam control valve and suppress the increase in turbine speed. There was a problem in that it reacted to frequency fluctuations as well. During such system fluctuations, most of the generator load remains, and when the quick-closing device operates, the steam control valve closes, and the turbine output drops to zero, the turbine speed suddenly drops. This will eventually lead to the plant being shut down.

An object of the present invention is to provide a turbine overspeed prevention device that can operate stably without stopping the turbine even when the system frequency fluctuates, and that quickly closes a steam control valve when the load is cut off to prevent overspeed of the turbine. It's about doing.

[Means for solving problems]

In order to achieve the above object, it is necessary to detect not only the acceleration rate of the turbine but also the speed reached during acceleration. Generally, frequency fluctuations during system fluctuations have a large acceleration rate but a small swing width. On the other hand, when the load is cut off, the acceleration and the attained speed are detected at the same time since both the acceleration rate and the swing range are large than 0, and the quick closing circuit is activated when the acceleration rate is greater than a specified value and the rotation speed exceeds a certain specified number of revolutions. This can be solved by opening the valve quickly when the problem occurs.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the 0-piece quick-closing device includes a quick-open pilot valve 1, a quick-open valve relay 3, a quick-open valve piston 5,
It consists of a quick-open solenoid valve 6 and a lever ring bridge connecting them. In this device, the turbine speed and acceleration are detected, and when the acceleration rate and speed insulation values become large at the same time, the quick-open solenoid valve is energized, the upper part of the quick-open piston is drained, and the steam control valve is activated. Close suddenly.

Thirdly, in the case of 0 interlocks, the acceleration rate is y%/" seconds or more, and the turbine speed is 2
If the imbalance between the turbine output and the generator output exceeds X%, the steam control valve will close suddenly. There is.

〔Effect of the invention〕

According to the present invention, it is possible to simultaneously satisfy two requirements: prevention of turbine overspeed during load cutoff and prevention of sudden closing operation due to system fluctuation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a conventional example, FIG. 3 is an explanatory diagram of an interlock of the present invention, and FIG. 4 is a system diagram of a turbine plant.

Claims (1)

[Claims] 1. In a plant consisting of a steam source, a steam turbine, a generator, and a steam control valve, when the generator load is cut off, the rate of increase and absolute value of the turbine speed are detected, and the rate of increase and the absolute value A turbine overspeed prevention device that rapidly closes a control valve and prevents overspeed by draining the hydraulic pressure of a conventional mechanical mechanism that only detects the rate of increase using a solenoid valve when is above a specified value. 2. A turbine overspeed prevention device according to claim 1, characterized in that an imbalance between turbine output and generator load is detected as a condition for rapid closing of a control valve.