The reverse power protection of diesel generator is used to protect the steam turbine. When the main steam valve is closed by mistake or the turbine boiler protection action closes the main steam valve and the outlet switch of the generator does not trip, the generator becomes the motor running state. At this time, the generator absorbs active and reactive power from the system. This working condition has no impact on the generator. However, due to the loss of blast, the tail blade of the gas turbine may overheat and damage the tail blade, resulting in steam turbine accident. Therefore, large units are not allowed to operate for a long time under this condition, only for a few minutes.

我国自行设计的发电机，以往不装设逆功率保护，但采取以下措施：

In the past, generators designed by our country were not equipped with reverse power protection, but the following measures were taken:

(1)采用联锁方法。当主汽门关闭后，用主汽门辅助接点，经延时切除发电机。上述方法虽然可行，但有不足之处，因为都不能正确地反映主汽门关闭情况。为了及时发现逆功率的异常工况，欧洲一些国家在发电机上配置有逆功率保护。逆功率保护其核心元件是逆功率继电器。逆功率继电器和功率方向继电器相似，只是在功率方向相反时动作，及时发出信号或延时动作切机。

(1) Adopt interlocking method. When the main throttle valve is closed, use the auxiliary contact of the main throttle valve to cut off the generator after delay. Although the above methods are feasible, they have shortcomings, because they can not correctly reflect the closing condition of main steam valve. In order to find the abnormal working condition of reverse power in time, some European countries have configured reverse power protection on generators. The core component of reverse power protection is reverse power relay. The reverse power relay is similar to the power direction relay, but acts when the power direction is opposite, sends a signal in time or delays the action to cut off the machine.

(2)主汽门关闭后，在控制室内发信号，如主汽门误关闭，检查之后可迅速恢复供汽，使机组正常运行，如几分钟恢复不了，可由值班员断开发电机出口开关。

(2) After the main throttle valve is closed, send a signal in the control room. If the main throttle valve is closed by mistake, the steam supply can be quickly restored after inspection to make the unit operate normally. If it cannot be restored in a few minutes, the operator on duty can turn off the outlet switch of the development motor.

1．供油时间过早

1. The oil supply time is too early

当柴油发电机活塞向上运动还没达到规定的喷油位置，喷油器就开始喷油，使燃油燃烧提前，气缸内的高压燃气冲击活塞，发出有节奏的“嗒、嗒”的清脆敲缸声，减小油门，敲缸声很明显。

When the piston of the diesel generator moves upward and hasn't reached the specified injection position, the fuel injector starts to inject fuel to advance the fuel combustion. The high-pressure gas in the cylinder strikes the piston and makes a rhythmic "Da, Da" crisp cylinder knocking sound. Reduce the throttle and the cylinder knocking sound is obvious.

排除方法是：调整供油提前角，即增加喷油泵与齿轮箱之间的垫片使供油时间延迟至符合规定的喷油时间。垫片每增加0.1毫米，供油提前角可延迟1.3-1.7。

The troubleshooting method is: adjust the fuel supply advance angle, that is, increase the gasket between the fuel injection pump and the gearbox to delay the fuel supply time to the specified fuel injection time. The oil supply advance angle can be delayed by 1.3-1.7 for every 0.1mm increase in the gasket.

2．燃油燃烧不良

2. Poor fuel combustion

喷油压力过低、喷油器滴油、喷油雾化不良以及供油时间过晚等都会造成燃油燃烧不良而引起敲缸。这类故障引起的敲缸声低沉、沙哑并伴有发动机过热、冒黑烟或排气管放炮、喷火等现象。应拆下喷油器进行检查和调整、调整供油时间，必要时更换零件，使之符合规定。

Low fuel injection pressure, fuel injector dripping, poor fuel injection atomization and too late fuel supply time will cause poor fuel combustion and cylinder knocking. The cylinder knocking caused by this kind of fault is low and hoarse, accompanied by engine overheating, black smoke or exhaust pipe blasting, fire spraying and other phenomena. The fuel injector shall be removed for inspection and adjustment, the fuel supply time shall be adjusted, and the parts shall be replaced if necessary to make it meet the regulations.

3．出油阀门磨损

3. The oil outlet valve is worn

出油阀磨损后，一方面使减压环带与阀座内孔配合间隙变大，密封性变差、减压效果变坏；另?方面高压油管内剩余压力过高，供油增加，引起燃油爆燃而敲缸．油门减小时敲缸声尤为明显。

After the oil outlet valve is worn, on the one hand, the fit gap between the pressure reducing ring belt and the inner hole of the valve seat becomes larger, the tightness becomes worse and the pressure reducing effect becomes worse; Another? On the one hand, the residual pressure in the high-pressure oil pipe is too high and the oil supply increases, resulting in fuel deflagration and cylinder knocking. The cylinder knocking sound is particularly obvious when the throttle is reduced.

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