Method and system for protection in a mixed line

A method for determining a location of a fault in a mixed line comprising two or more sections, with a first substation at a first end of the mixed line and a second substation at a second end of the mixed line, every two consecutive sections of the mixed line being separated at a respective junction, the method being performed by an Intelligent Electronic Device (IED), the method comprising:

• obtaining one or more current measurements at the first end of the mixed line, from a current signal received from a measurement equipment of the first substation;
• receiving one or more current measurements at the second end of the mixed line, over a communication channel;
• estimating a value of current for each junction of the mixed line using the one or more current measurements at the first end, an equivalent source impedance of the first substation, an equivalent source impedance of the second substation, and impedance of each section of the two or more sections of the mixed line,
• the estimating the value of current for each junction of the mixed line being performed without using any voltage measurement,
• a first section of the two or more sections having a first predetermined impedance characteristic, and
• a second section of the two or more sections having a second predetermined impedance characteristic different from the first impedance characteristic;
• identifying a section of the two or more sections of the mixed line having the fault, based on a comparison between the value of current estimated for each junction and the one or more current measurements at the second end;
• and
• determining the location of the fault in the section of the mixed line identified as having the fault, using the one or more current measurements at the first end, the one or more current measurements at the second end, the equivalent source impedance of the first substation, the equivalent source impedance of the second substation, and the impedance of each section of the two or more sections.