1、Weight
  Good quality electronic wire, generally within the specified weight range. Such as the commonly used cross-sectional area of 1.5 plastic-insulated single-stranded copper core wire, the weight of 1.8-1.9kg per 100m.

2.5 plastic insulated single-strand copper core wire, the weight of 2.8-3.0kg per 100m; 4.0 plastic insulated single-strand copper core wire, the weight of 4.1-4.2kg per 100m, etc. Poor quality wire

Weight is not enough, either the length is not enough, or wire copper core impurities too much.
2, copper quality
  Qualified copper-core power cord copper core should be purple-red, shiny, soft to the touch. And shoddy copper core wire copper core is purple-black, yellowish or white, impurities, mechanical strength

Poor, poor toughness, a little force will break, and the wire is often broken line phenomenon. Check, you just need to strip the wire 2cm, then use a piece of white paper in the copper core

Slightly rubbed, if there is black material on the white paper, the copper core is more impurities. In addition, shoddy wire insulation layer seems to be very thick, in fact, most of them are made of recycled plastic, over time, the insulation layer will be aging and leakage.
3, manufacturers
  Counterfeit and shoddy high-voltage wire is often "three no products", but also has an ambiguous origin and other identification, such as made in China, a Chinese province or a city, which actually amounts to unmarked origin.