Measurement of insulation resistance of marine generator sets and distribution boards
Before any electrical equipment is powered on, insulation resistance measurement must be carried out, which is the fundamental guarantee of personal safety and equipment safety, and is also a necessary inspection item in the inspection process.
Overview
Insulation resistance is divided into cold insulation resistance and hot insulation resistance.
Cold insulation resistance refers to the insulation resistance of the equipment before the test, when the equipment is in its natural state, and the inspection is based on the installation status of the equipment. Thermal insulation resistance refers to the insulation resistance of equipment that has been running for a certain period of time and has reached a temperature rise. At this time, the equipment is still in working condition, and it is used to test the insulation performance changes of equipment insulation materials under dynamic and thermal conditions.
Before conducting cold insulation resistance measurements, all external circuit switches on the distribution board should be disconnected, and all semiconductor components on the generator set and distribution board must be disconnected to avoid damage to semiconductor components due to excessive current. The content of insulation resistance measurement for generator sets and distribution boards includes: insulation resistance of distribution board busbars to ground; The insulation resistance of the generator armature winding to ground; The insulation resistance of the generator excitation winding to ground and the insulation resistance of the generator space heater to ground; The insulation resistance of a speed regulating motor to ground.
Before testing the diesel generator set and distribution board, measure the cold insulation resistance. Measurement can be carried out using a megohmmeter, with one end of the megohmmeter grounded and the other end connected to the area to be measured. Surveyors and shipowners are required to be present during the measurement.
The thermal insulation resistance of diesel generator sets and distribution boards should be measured immediately after equipment testing, using the same method as checking the cold insulation resistance. Regardless of the state, for distribution boards with a length less than or equal to 6m, their minimum insulation resistance value should be greater than or equal to 1M Ω
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