high voltage，medium voltage，low voltage classification
The high/medium/low voltage classification usually definition in the electric system, In the different voltage ,should fix the insulator .
The insulator is a special insulation controls .
And the voltage grade can be divied into High voltage ,medium voltage , low voltage , also have the ultrahigh voltage and extra-high voltage ,etc.
The high ,demium , and low voltage detail definition as below :
1，High voltage : the nominal voltage between 1kv and 300kv AC voltage
2, medium voltage : The IEEE called the voltage between 2.4KV and 69KV as medium voltage .
3, Low voltage : the nominal voltage 1KV or under 1KV’s ac voltage
Also have the Extra-high voltage and Ultrahigh voltage:
4， Extra-high voltage : the nominal voltage between 330kv and 10000 kv AC voltage
5， Ultrahigh voltage : the nominal voltage above 1000 kv AC voltage
For the high voltage , medium voltage and low voltage ,often use insulators which main have porcelain insulators and composite insulators .
In the early years , the insulators usually use in the telegraph pole , then development in the high voltage towers , play an important role in the overhead transmission lines.