For the Street Lamp Junction box of the single element, the insulation resistance can only be measured in the case of power failure. The relevant regulations stipulate that the megohmmeter of 2500V and above is used. At present, 2500V and 5000V megohmmeters are used more, and there are also specialized instruments with higher voltages. For the multi-component Street Lamp Junction box, the insulation resistance can be measured either by power failure or by live measurement. The method is to connect the high-resistance to the charged Street Lamp Junction box, so that the megohmmeter for measuring the insulation resistance is at the ground potential, and the resistance value of the high resistance is subtracted from the measured insulation resistance, that is, the Street Lamp Junction is measured. The insulation resistance value of the box.
It is worth noting that when measuring the insulation resistance of each component of the Street Lamp Junction box, the copper wire should be wound around the layered glue and then connected to the megohmmeter to avoid the difference of the insulation resistance values measured at different positions. Too big, causing misjudgment.