Transformer Megger Test
The megger has three terminal posts: one for "L", one for "E" and one for "G" (shield). L is connected to the wires, E is connected to the cable, and the "G" is attached to the insulated paper of the cable. The following points should be noted when measuring:
The power must be cut off first.
The megger must be kept flat when used.
Before we use the megger, we need to rotate several times to see whether the pointer is at the largest location. Then we will short-circuit the two terminals of "L" and "E", then slowly turn the hand of mega ohmmeter to see whether the pointer is at zero.
The megger cable must be insulated well, and the two lines shall not be twisted together.
When measuring the megger, the reading should be based on the number after a minute of rotation.
During the measurement, the number of meters should be transferred to 120 revolutions per minute.
The megger has a range of several thousand megaohm, with a minimum scale of about 1 trillion euro, which is not suitable for measuring the resistance below 100 kiloohm.