Loadability of 400 kV four-bundled overhead transmission lines

The transmission capacity of high voltage overhead power transmission lines (OHLs) can be increased in different ways. One of these is to increase the number of standard ACSR (Aluminium Conductor Steel Reinforced) conductors forming the bundles of OHLs. This paper analyzes the performance of 400 kV, four-conductor bundled (4B) OHLs in terms of loadability, i.e. the maximum power that can be transmitted as a function of the length of the line. First, we calculate the loadability curve of 4B OHLs and then we compare it with that of three-conductor bundled (3B) OHLs, the common solution adopted in Italy and in other countries for the 400 kV voltage level. We calculate the loadability curves up to a length of 500 km, assuming the same standard conductor for both 3B and 4B lines, and keeping into account the conductor thermal limit, maximum voltage drop, maximum power losses, and steady-state stability limit.