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The Moisture-proof Attentions of Diesel Generator Set

Nov. 02, 2019

In the dense fog weather, the surrounding environment will become humid, so what should be paid attention to when diesel generator sets are moisture-proof?


The unit is parked in the place with high relative humidity for a long time, such as basement, coastal area, the operation time of the unit is relative longer, the insulation performance of the generator is reduced, and the electrical components of the control system are easy to be damaged due to moisture. So measures need to be taken to prevent the unit against moisture.


We can install generator damp proof heater and control panel moisture-proof heater on diesel generator set to resolve moisture problem. Because generator damp proof heater and and control panel moisture-proof heater is optional part, when users purchase, should tell the supplier.


The attention on moisture-proof for diesel generator set:

1.Heating and drying shall be carried out in clean air, and the generator shall be blown clean with compressed air before drying. If the winding is seriously wet, it needs to be dried by hot air method first. After drying, dry with load to avoid insulation breakdown. When drying, we should put more thermometers in the parts of industrial diesel genset, so as to grasp the temperature of each part and reduce local overheating. Heating shall be carried out slowly to avoid insulation damage caused by sudden evaporation of moisture in the coil.

2.If the drying temperature does not reach the required temperature, it can be dried at a slightly lower temperature. But the time should be lengthened properly. Measure temperature and insulation resistance every 30min after drying. when the temperature is stable, measure every 1-2h and make records.

3.In the early drying stage of diesel generator set, due to the heating of winding and the evaporation of water, the insulation resistance will decrease. And then gradually rise, the speed of rise is more and more slow, final stable at a certain value.

When the insulation resistance is kept constant for more than 3 hours at a constant temperature, the drying can be finished. Either way, after drying, when the coil is cooled to 60℃, the insulation resistance of stator winding and hand winding shall be measured with 500V megger and shall not be less than 0.5MΩ.


In order to let the unit work normally, there should not have water, oil, sewage, corrosive gas etc. around the unit to avoid damaging the insulation of generator set. The temperature of cold air shall not be too low to avoid condensation on the winding and other conductive parts.

 electric generator

When making dampproof, pay attention not to affect the normal ventilation and cooling of the generator set. Always clean the dust and dirt in the ventilation duct and keep it unobstructed. For the generator that stops running for a short time for some reason, the collector ring does not need to be protected by holding brake, however, insulating cardboard, paraffin paper or asphalt paper shall be padded between the brush and the collecting ring to avoid spots on the surface of collecting ring caused by electric brush. In terms of the processing of the generator, if the paint is rusted due to falling off, the rust shall be removed in time and the antirust paint shall be applied.


Here are some other ways to dry diesel generator set:

1.Cold operation method.

When the AVR power line is disconnected, the generator set placed in dusty or humid environment for a long time can be idle for about 10 minutes. This may be enough to dry the winding surface and increase the insulation resistance to more than 1 MΩ to generate electricity.

2.Hot air method.

Remove all covers of the generator set in order to remove the moist air. Use a blower to blow in from the air inlet of the generator set. Please note that the heat source and winding should be kept at least 300 mm to avoid overheating and insulation damage, and control Surface temperature of winding. The winding surface temperature shall not exceed 85 ℃ and the inlet temperature shall not exceed 90 ℃. Continue blowing every half hour and record the insulation resistance value. When the value is greater than the specified value, the drying process is completed. Remove the blower, close all covers, and try again.

3.Drying method of short circuit current.

Firstly, carry out the safe operation of the mechanical and electrical equipment of the unit to ensure the safe operation of the generating set. The output end of the generator set is short circuited through the short circuit piece, which shall be able to bear the rated current of the generator set. Disconnect AVR(Automatic voltage regulator) and switch to external 0 ~ 24V DC power supply, adjust DC power supply voltage to make each phase current of stator 50-70% of rated current. Stop every 30 minutes, disconnect the external excitation power supply, check and record the insulation resistance value. If the insulation resistance is greater than the specified value, the external DC power supply can be removed, and AVR can be reconnected and re-debugged. The generator set can operate at rated speed, but the speed shall be kept constant to avoid temperature instability.

4.Drying method with load.

If only the surface is wet, we can dry the unit with load. When drying, The generator set can operate at 50% of rated current load. Then increase the rated current by 65%, 85% and 100%. The load for each phase is 4 to 5 hours. During the drying process, the insulation resistance of each winding shall be tested regularly. After the insulation resistance meets the requirements, the drying can be stopped and the generator set is usually tested.


Hope the article is helpful to you. If you also need to purchase diesel generator set, contact us by email sales@dieselgeneratortech.com. 

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