The cable joint is the weak link where faults frequently occur in the operation of high voltage(HV)cable lines. The cable current-carrying capacity can be restricted for the existence of the cable joint. As a constraint on current-carrying capacity of DC cable is different from that of AC cable

it is inappropriate to apply the calculation method of current-carrying capacity of AC cable. Nevertheless

there is currently no calculation method for the DC cable joint. On the basis of theoretical research on simulation calculation of temperature field

a method for determining the current-carrying capacity of HVDC cable joint is proposed with the maximum allowable operating temperature of conductor and the maximum allowable temperature difference in the insulating layer as two constraints. Through case analysis

the proposed calculation method of current-carrying capacity is compared with the method of IEC 60287 standard

and the influence of environment temperature on the current-carrying capacity of cable joint is also studied. The results show that the cable joint is one of the constraints of current-carrying capacity calculation in the cable system. Besides

the relation curve between current-carrying capacity and environment temperature is intersected at one point under two constraints. The maximum allowable temperature difference in the insulating layer is the decisive constraint on the cable current-carrying capacity when the environment temperature is less than the corresponding temperature value at the intersected point; otherwise the maximum allowable operating temperature of the conductor is the decisive constraint on the cable current-carrying capacity. This work is supported by Guangdong Provincial Natural Science Foundation of China(No. 2014A030310371)and China Southern Power Grid Company Limited(No. K-KY2014-31).