A traction substation is a specialized electrical conversion station for railways. Its function is to step down the voltage and convert the type of electric current, transforming alternating current (AC) into direct current (DC) to suit the trains motors. The substation use power from the PLN (e.g. 20 kV) and converts it to a specific voltage (such as 1500 V DC). This electricity then fed into the catenary system (railways electricity power lines) to power the trains.