Created on:2021-08-03 15:06

Fault analysis and improvement of mechanical hydraulic system of governor in Hydropower Station

水电站调速器机械液压系统故障分析改造
Fault analysis and improvement of mechanical hydraulic system of governor in Hydropower Station

(1) PA、PB压力开关误报、误动原因分析及改造
(1) Cause analysis and improvement of PA and Pb pressure switch misoperation

    ①PA、PB压力开关误报、误动的成因 PA、PB压力开关误报、误动的问题,经过多次现场观察,发现空载阀由带载转为空载时,有较大的动作声响和振动,同时压力表指针摆动。误报时间与感压阀动作时间的吻合证明了空载随动系统在设计或调试上的不足:空载阀开启过快,使得压油泵由带载瞬间转换为空载,由于压差也瞬时阻断油流,导致液压管路产生很大的压力脉动,脉动的峰值则可能达到PB压力开关动作值,使其误动;另外空载阀开启过快,使得空载阀的阀芯与阀套产生撞击,而PA、PB压力开关装在油箱本体上,过大的撞击振动也会使压力开关内的微动触点抖动,造成保护动作事故停机。
① The causes of PA and Pb pressure switch misinformation and misoperation the problem of PA and Pb pressure switch misinformation and misoperation was found after many field observations that when the no-load valve changed from loaded to unloaded, there was a large movement sound and vibration, and the pressure gauge pointer was swinging. The coincidence between the false alarm time and the action time of the pressure sensing valve proves the shortcomings of the no-load servo system in design or debugging: the no-load valve opens too fast, which makes the pressure pump switch from loaded to no-load instantly, and the pressure difference also blocks the oil flow instantaneously, which leads to great pressure pulsation in the hydraulic pipeline, and the peak value of the pulsation may reach the action value of Pb pressure switch, which makes it misoperate; In addition, if the no-load valve is opened too fast, the valve core of the no-load valve will collide with the valve sleeve. If the PA and Pb pressure switches are installed on the oil tank body, the excessive impact vibration will also make the micro contact in the pressure switch vibrate, resulting in the protection action accident shutdown.

②改造措施调整空载阀开启速度。如果空载阀阀芯以合适的速度开启,则可实现压油泵由带载到空载的软过渡,大幅减轻油压的波动和油箱的振动,从而有效解决PA、PB压力开关的误动问题。控制空载阀的开启速度,电站采取的措施如下。
② Reform measures to adjust the opening speed of no-load valve. If the valve core of no-load valve is opened at a proper speed, the soft transition of pressure pump from loaded to no-load can be realized, and the fluctuation of oil pressure and the vibration of oil tank can be greatly reduced, so as to effectively solve the misoperation problem of PA and Pb pressure switches. To control the opening speed of the no-load valve, the measures taken by the power station are as follows.

调速器油压装置保护动作停机统计
Statistics of protection action and shutdown of governor oil pressure device

序号
Serial number

内 容
Content

1
one

5#机在空转态,上位机报‘5#机事故低油压’,机组停机。现场检查未见异常,原因为PA误动(连续发生3次)
When the 5-Machine is in idle state, the upper computer reports "5-Machine accident low oil pressure", and the unit stops. No abnormality was found in the field inspection, and the reason was PA malfunction (3 times in a row)

2
two

上位机报‘3#机压力油罐油位极低’,事故停机流程启动,甩负荷20MW。经检查分析,原因为机组振动引起开关误动所致
The upper computer reported that "the oil level of the pressure oil tank of 3 unit is very low", the emergency shutdown process started, and the load rejection was 20 MW. After inspection and analysis, the reason is that the unit vibration causes the switch misoperation

3
three

上位机报‘3#机压油装置油压过高,灭磁开关跳闸’,事故停机流程启动。三分钟后停机。现场检查油压正常(6.4MPa),其他设备运行也正常。元婴为PB误动
The upper computer reported that "the oil pressure of the oil pressure device of 3 unit is too high, the de excitation switch trips", and the emergency shutdown process starts. Shut down in three minutes. The oil pressure was normal (6.4Mpa) and other equipment was running normally. Yuanying is Pb maloperation

4
four

5#机开机过程中,上位机报‘锁锭未拔出,流程退出’,原因:调速油箱双筒过滤器单向阀回堵,造成控制管路无压,锁锭不能拔出
5. During the start-up of the machine, the upper computer reported that "the lock ingot has not been pulled out, and the process has exited". The reason is that the one-way valve of the double drum filter in the speed regulating oil tank is blocked back, resulting in no pressure in the control pipeline, and the lock ingot cannot be pulled out

5
five

上位机报“5#机事故低油压”,现场检查:5#机保护盘上“水机事故”灯亮,5#机出口开关、灭磁开关跳闸,调速器压油罐压力为5.5MPa,油位过低。5#机甩负荷120MW,5#机快速门在全关位置。检修人员检查发现调速器1#泵连接螺栓松动,感压阀动作不灵活、有卡阻现象
The upper computer reported "low oil pressure in case of 5 ᦇ machine accident". The on-site inspection showed that the "water machine accident" light on the protection panel of 5 ᦇ machine was on, the outlet switch and de excitation switch of 5 ᦇ machine tripped, the pressure of governor oil tank was 5.5mpa, and the oil level was too low. The load rejection of 5 unit is 120mW, and the fast door of 5 unit is in the fully closed position. The maintenance personnel found that the connecting bolts of governor 1 and pump were loose, the pressure sensing valve was not flexible and jammed

6
six

  中控室上位机报“2#机压力油罐油位低”,2#机调速器压力装置备用泵1#泵自动启动。23min后上位机报“2#机组压力油罐油位过低,水机事故停机”,启动事故停机流程,2#机甩负荷120MW。现场检查:2#机调速器压力油罐油位过低,油压为5.7MPa,调速器1#、2#压油泵运行正常。经检修人员检查分析,原因为2#相调速器系统感压阀发生卡阻
The upper computer in the central control room reported that "the oil level of the pressure oil tank of unit 2 is low", and the standby pump 1 of the governor pressure device of unit 2 started automatically. After 23 minutes, the upper computer reported "the oil level of the pressure oil tank of the 2 unit is too low, and the water turbine is shut down by accident", and started the accident shutdown process, and the load rejection of the 2 unit is 120 MW. On site inspection: the oil level of governor pressure oil tank of unit 2 is too low, the oil pressure is 5.7mpa, and the operation of governor 1 and 2 pressure oil pumps is normal. According to the inspection and analysis by the maintenance personnel, the reason is that the pressure sensing valve of the 2-phase governor system is jammed

7
seven

5#机组开机并网,3小时15分钟后上位机报:‘5#机调速器回油箱油位过低’、‘5#机水机事故停机操作’,停机流程启动,甩负荷110MW。原因:5#机组接力器进油管口法兰内部的O形橡胶密封圈在机组运行中突然破裂,向外喷油所致

 

    a. 在感压阀和空载阀间加减(现场试验调整)节流片61B,减小空载阀控制油路的回油速度。
a. The throttle plate 61b is added and subtracted between the pressure sensing valve and the no-load valve to reduce the oil return speed of the no-load valve control oil circuit.

    b. 加大节流片63B的直径(设计值庐27,实际不详,加大值现场试验确定),使能以较快的速度排走空载阀40A阀芯刚开启时残留在空载阀下腔的压力油,减小作用在40A阀芯下部的压力。
b. By increasing the diameter of the throttle plate 63b (design value: lu27, unknown, increase value determined by field test), the pressure oil remaining in the lower chamber of the no-load valve 40A when the spool of the no-load valve is just opened can be drained at a faster speed, and the pressure acting on the lower part of the 40A spool can be reduced.

    c.采取防止压力开关动作触点抖动的措施。为防止回油箱振动使PA、PB压力开关触点抖动引起误动作,同时考虑液压系统发生事故时能可靠动作,将PA保护延时1s,将PB保护延时1.2s。
c. Take measures to prevent the action contact shaking of pressure switch. In order to prevent the PA and Pb pressure switch contact shaking caused by the vibration of the oil return tank, and considering the reliable action of the hydraulic system in case of an accident, the PA protection is delayed for 1 s and the Pb protection is delayed for 1.2 s.

(2)感压阀卡阻的处理
(2) Treatment of pressure sensing valve jamming

    调速器事故引起的停机,除上述因压力开关误动所致外,感压阀卡阻导致的事故停机也发生多次,原因是调速器的油质较脏,油内的杂质颗粒常常堵住感压阀操作油路上的截流片62B,使得空载阀始终运行在空载侧,而无法向液压系统适时打压,导致压力油罐油位、油压持续下降,最终发生低油压和压油罐油位过低而事故停机。
In addition to the above-mentioned misoperation of pressure switch, the emergency shutdown caused by pressure sensing valve jamming also occurred many times. The reason is that the oil quality of the governor is dirty, and the impurity particles in the oil often block the interceptor 62b on the operating oil circuit of the pressure sensing valve, so that the no-load valve always runs on the no-load side, and it is unable to pressurize the hydraulic system in time, resulting in the oil level of the pressure oil tank The oil pressure continued to drop, resulting in low oil pressure and low oil level of oil tank, resulting in accident shutdown.

    由于设计上未考虑在调速器液压系统内的部分控制油路上安装过滤器,电站只能根据调速器的运行状况及油质化验结果,缩短滤油(换油)维护周期,尽量减小油内杂质对液压系统安全运行的影响。
Because the filter is not considered to be installed in the hydraulic system of the governor in the design, the power station can only shorten the oil filter (oil change) maintenance cycle and minimize the impact of impurities in the oil on the safe operation of the hydraulic system according to the operation status of the governor and the oil quality test results.

    另外考虑到油管路死角的杂质很难清除以及从感压阀自身机械故障发生卡阻的实际问题,电站采取了临时的手动恢复措施,即在空载阀的控制油路上并联一支管,安装常闭阀42(见图F),在感压阀发生卡阻时可手动维持液压系统的油压、油位。操作方法为:
In addition, considering that it is difficult to remove the impurities in the dead angle of the oil pipeline and the actual problem of blockage caused by the mechanical failure of the pressure sensing valve itself, the power station adopts temporary manual recovery measures, that is, a branch pipe is paralleled on the control oil circuit of the no-load valve, and a normally closed valve 42 (see Fig. f) is installed, which can manually maintain the oil pressure and oil level of the hydraulic system when the pressure sensing valve is blocked. The operation method is as follows:

①若感压阀卡在空载侧(故障发生率高),打开阀门43,使液压泵负载运行,当压力达到额定压力时,关闭阀门43,打开阀门42,液压泵将空载运行,然后关闭阀门42;②若感压阀卡在负载侧,关闭阀门45,打开阀门42,液压泵将空载运行,关闭阀门44,打开阀门43,保持约10s,然后关闭阀门43,打开阀门44,关闭阀门42,打开阀门45。这样通过反复改变感压阀控制油路的油压,使其恢复正常。
① If the pressure sensing valve is stuck in the no-load side (high failure rate), open valve 43 to make the hydraulic pump run with load. When the pressure reaches the rated pressure, close valve 43 and open valve 42 to make the hydraulic pump run without load, and then close valve 42; ② If the pressure sensing valve is stuck on the load side, close valve 45, open valve 42, the hydraulic pump will run without load, close valve 44, open valve 43, hold for about 10s, then close valve 43, open valve 44, close valve 42, open valve 45. In this way, by repeatedly changing the pressure sensing valve to control the oil pressure of the oil circuit, it can return to normal.

    调速器油压装置设计时须考虑在控制管路设置过滤器;油压装置在充油前须保证液压管路彻底清扫干净,验收上要严把质量关;油压装置设计上应考虑在液压系统故障时的手动恢复措施,以提高其可靠性;对于液压系统的保护,设计上要考虑压力波动、机构振动以及保护可靠性等因素,采取防抖措施避免误动作。
When designing the governor oil pressure device, the filter should be set in the control pipeline; The hydraulic pipeline of the oil pressure device must be thoroughly cleaned before oil filling, and the quality must be strictly controlled in the acceptance; In order to improve the reliability of the hydraulic system, the manual recovery measures should be considered in the design of the hydraulic system; For the protection of hydraulic system, the factors such as pressure fluctuation, mechanism vibration and protection reliability should be considered in the design, and anti shake measures should be taken to avoid misoperation.
When designing the governor oil pressure device, the filter should be set in the control pipeline; The hydraulic pipeline of the oil pressure device must be thoroughly cleaned before oil filling, and the quality must be strictly controlled in the acceptance; In order to improve the reliability of the hydraulic system, the manual recovery measures should be considered in the design of the hydraulic system; For the protection of hydraulic system, the factors such as pressure fluctuation, mechanism vibration and protection reliability should be considered in the design, and anti shake measures should be taken to avoid misoperation.

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