Measurement of deep well pump motor insulation resistance

Measurement of deep well pump motor insulation resistance:
     According to the working voltage of the deep well pump motor, use the appropriate level of megger (500V), megger L terminal connected to the motor cable, E terminal ground wire. In the cold state of the insulation resistance of not less than 500MΩ, close to the operating temperature (hot state) should not be less than 1MΩ.
That if there is no ground wire how to do it? The easiest way to put a line to the wells, as "measuring ground wire.
    Access to the deep well pump power lines are generally three-phase, although the pump body marked above the ground end, when in practice, very few people care about this point, and did not connect the required grounding terminal.
Deep well pump before use, in order to ensure personal safety, electric pump must be reliable grounding!