he man leading the investigation into last week's blackout has come to one firm conclusion: either the rules for power transactions on the electrical grid were broken, or they were inadequate, even though they are hundreds of pages of detailed specifications covering seemingly every contingency.

Michehl R. Gent, president and chief executive of the North American Electric Reliability Council, the industry organization that created many of those rules after the 1965 blackout, is not willing to say which possibility he considers most likely at this stage, but his early conclusion has focused attention on the rules governing the power grid, a complex and, in the estimation of some experts, physically inadequate system for moving energy around the country.

Many of those rules - how much power can move in a line, when systems need to be shut down in an emergency - were drawn up long before deregulation opened the sluice gates and enabled the present transfer of billions of watts of energy around the country daily in wholesale transactions across hundreds or thousands of miles. As detailed as those rules are, according to many people in the industry, they are no match for the overwhelming scale and complexity of the grid that lost power over vast stretches of the Northeast and Canada last week.

Ben Carreras, a physicist at Oak Ridge National Laboratory who models the grid on computers, said that using the rules to control the behavior of the grid was sometimes like using a naturalists' handbook to tame a tiger.

And Terry Boston, executive vice president of transmission and power supply for the Tennessee Valley Authority, said, ``We have worked for many years developing the rules of the road.'' ``The problem is,'' he said, ``we're asking the system to go into a mode of operation that is far different than what it was designed to do. It was designed for short distances. Now, in the new open market, we're seeing transactions covering hundreds of miles.''

Adding another complicating factor is the reality that the rules are voluntary, enforced by little more than peer pressure and the potential sting of bad press after particularly bad power failures.

`I don't know of any grid that's got legally binding enforcement,'' said Charles Jenkins, vice president for transmission grid management at Oncor, a part of TXU in Dallas, a private company that moves electricity around the grid.