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Except for wires made from a special "superconducting" material, all normal wires (copper, aluminum, steel, etc.) have some electrical resistance. So a certain amount of power will always have to be used to overcome the resistance of all the wires in a power grid, including wiring in the many Transformers, switches, etc. which are needed to distribute the power efficiently. Any power used to overcome the resistance of the wires is dissipated as heat which raises the temperature of the wires, their surrounding insulation (if any) and - in the case of overhead cables - any surrounding air. In the case of an underground or underwater cable which has a cooling fluid such as mineral oil (which is a good conductor of heat yet is also a good electrical insulator) the heat gets dissipated into the cooling fluid which is pumped continuously to allow the heat to be radiated to the air (or to water in, perhaps, a resevoir) using a radiator assembly positioned away from the cable itself. If the question is not actually asking about power used to overcome the resistance of the wires, then it may be asking something like: "Does the power being generated in power stations ever exceed the total power load being taken by the houses, factories, etc. connected to the grid and by the grid's connecting wires, transformers and switches?" Basically, the answer to that question is No, because, at all times, the net power output being generated at any instant by all the power stations feeding a distribution grid must always be exactly equal to the sum of all the power being demanded by all the loads connected to that grid PLUS the sum of all the power used to overcome the resistance of the grid's wires. However, there are two things other than power which do change continuously over any given period of time: the supply voltage and the supply frequency. That must be so because a power generator set cannot accelerate or decelerate instantly! Such power generator sets are usually massive alternators driven either by steam turbines (fueled by coal-burning boilers or nuclear power), diesel engines or by water wheels (driven by water falling from a high dam), all of which have very heavy rotating masses that require a finite time to speed up or to slow down. During such periods the supply frequency must be allowed to speed up or to slow down within set limits and the delivered voltage also must be allowed to vary, again within set limits. Before computer-based grid power control systems were invented the only way that the power output of power stations could be matched to consumers' total power demand was by human "power grid operators" who had to carefully monitor and anticipate total power demand rising or falling throughout the course of each day. They had to anticipate likely major changes in demand - such as when a football match ends or a commercial advertisement break occurs on television and all viewers switch on their ovens and kettles en masse - so that extra power generation sets could be brought on-line (or taken off) as necessary. Such action is essential to keep the grid's supply frequency and voltage within the limits as specified by the grid's operating standards. Nowadays computer-based grid power control systems do most of that work, but human operators are still needed to "keep a close eye on things" to be sure the grid is operating efficiently. Such good control of a grid cannot be assumed to take place all over the world. In developing countries and those where there is an ongoing conflict situation (= war) it is common for reliable power grid control to be very difficult at best or non-existent at worst. People living in such countries have to suffer erratic losses of electric power with or without warning. Consequently, in such circumstances, vital public facilities such as hospitals have to operate their own private generator sets to cope with periods when the public electricity supply grid is "down". (That applies to hospitals, etc. in developed countries too.)
