1) underground network
2) underground system
a network consisting essentially of underground cables
GRM: n. (1,2)
References:
ANT overhead network
ANT overhead system
GEN electrical power system
GEN electrical power network
GEN electrical network
GEN grid
GEN network
SEE cable line
SEE buried cable
SEE subterranean cable
SEE underground line
SEE underground cable

ENERGY TERM COURTESY OF ENERGY.EU