Advantages: less consumption of non-ferrous metals, low cost.Disadvantages: when the main line fails, the influence range is large and the reliability is low.Scope of application: generally no more than three sets of equipment, the total capacity of which is no more than 10kV, one of which is no more than 5kV. The utility model is suitable for the unimportant small capacity electrical equipment which is far away from the power distribution device and close to each other.