The low-voltage DC distribution network is important to ensure the load demand on the load side

but once the fault appears in the low voltage network lines

it will pose great challenge to the entire system

therefore the fast and secure fault detection is important to it.This paper proposes a method for online rapid detection and location.Firstly

the DC distribution network classification is explained

and its characteristics are explained according to the inverter type

voltage level

grounding mode and network topology.Then the protection mechanism of this paper is proposed.After extracting the characteristics of different types of faults

the joint detection methods of zero-order square root

second-order square root and fourth-order square root are proposed.The fault threshold

fault location principle and fault pole detection are analyzed.Finally

the simulation is carried out in the IEEE 13 node system

and the applicability of the proposed method is analyzed under different fault impedances

fault distances and faults.