An underground modular transformation centre system that is resistant to disasters and adverse conditions, the transformation system comprising: - a transformation centre comprising: - a cylindrical enclosing body resistant to mechanical stress from the ground and having two ends, - an assembly hatch with an upper watertight access cover for inserting switchgear in the enclosing body and a manhole hatch with an upper watertight access cover for the access by people; - high-voltage protection and operating elements, a power transformer and low-voltage protection and operating elements inside the enclosing body of the transformation centre; - tubes passing from the outside to the inside of the enclosing body for placing electrical conductors, the tubes having elements that provide watertightness to said electrical conductors; characterized in that: the transformation centre further comprises: - a coupling system arranged in each of said ends of said enclosing body and closing covers joined to the coupling system; - tubes for circulating a coolant; the power transformer comprising: - a tank comprising electrical connection outlets arranged in the lower side area of the tank; - an upper closing cover having an inner and an outer coupling system, the inner coupling system being coupled to the tank of the transformer and the outer coupling system being configured to fasten the transformer to the enclosing body of the transformation centre; and in that the transformation center is modular and configured to be longitudinally connected to other transformsation centers through the coupling system arranged in the ends of the enclosing body; and in that the transformation center system further comprises: - a longitudinal heat exchanger arranged outside the transformation centre with a dimension similar to the length to this transformation centre, formed by horizontal tubes and heat dissipative sheets, and in that the tubes for circulating a coolant of the transformation centre are connected to the heat exchanger and to the power transformer for removal of heat generated inside the transformer. - a transformation centre comprising: - a cylindrical enclosing body resistant to mechanical stress from the ground and having two ends, - an assembly hatch with an upper watertight access cover for inserting switchgear in the enclosing body and a manhole hatch with an upper watertight access cover for the access by people; - high-voltage protection and operating elements, a power transformer and low-voltage protection and operating elements inside the enclosing body of the transformation centre; - tubes passing from the outside to the inside of the enclosing body for placing electrical conductors, the tubes having elements that provide watertightness to said electrical conductors; - a cylindrical enclosing body resistant to mechanical stress from the ground and having two ends, - an assembly hatch with an upper watertight access cover for inserting switchgear in the enclosing body and a manhole hatch with an upper watertight access cover for the access by people; - high-voltage protection and operating elements, a power transformer and low-voltage protection and operating elements inside the enclosing body of the transformation centre; - tubes passing from the outside to the inside of the enclosing body for placing electrical conductors, the tubes having elements that provide watertightness to said electrical conductors; - a coupling system arranged in each of said ends of said enclosing body and closing covers joined to the coupling system; - tubes for circulating a coolant; - a tank comprising electrical connection outlets arranged in the lower side area of the tank; - an upper closing cover having an inner and an outer coupling system, the inner coupling system being coupled to the tank of the transformer and the outer coupling system being configured to fasten the transformer to the enclosing body of the transformation centre; and - a longitudinal heat exchanger arranged outside the transformation centre with a dimension similar to the length to this transformation centre, formed by horizontal tubes and heat dissipative sheets, and