Abstract: Elbow-type cable joints age easily after a long period of operation. An air gap can form at the contact interface between the elbow-type cable joint and the bushing. Self-cleaning incipient arc fault happens after condensation penetrating into the narrow air gap. The cumulative damage caused by multiple incipient faults can cause serious accidents such as combustion and explosions. The study of the generation mechanism and development process and the extraction of fault signal characteristics can guide the detection and identification of elbow-type cable joint incipient faults and improve the reliability and operation level of distribution lines. In this paper, the development process of incipient faults, the arc morphology, and the fault current waveform characteristics are investigated based on magnetohydrodynamic simulation models and field experiments. The results show that the elbow-type cable joint incipient fault can be divided into three stages named "water belt is close to the electrode - water belt boils - water belt dries up". The duration of the fault current zero time in the first stage gradually decreases until it disappears, and the waveform transforms into a sinusoidal waveform. The duration of the fault current zero time in the second stage first increases and then decreases. There are several times of "no zero rest - the existence of zero rest - no zero rest" transition in this stage. The duration of the fault current zero time in the third stage gradually increases until the arc is completely extinguished. There is a "no zero rest - the existence of zero rest" transition in this stage. The results of the study provide a basis for further realization of the detection of elbow type cable joint incipient faults.