There's a difference between a solar flare, and a coronal mass ejection and the effects they produce on or above the Earth. The A, B, C, M, X classes of flares refer to the peak energy measured at a specific X-Ray wavelength. This is omnidirectional high energy electromagnetic radiation that travels at the speed of light. Such radiation does not pose a threat to electrical infrastructure or devices on the ground.

What do pose a threat are the CMEs often associated with solar flares. These are massive clouds of charged particles that generally spread out from site of a flare (a sunspot group) and expand out into the solar system at 1000 km/s or more. When these particles slam into and get trapped by Earth's geomagnetic field, huge electric currents can be produced which in turn can induce currents in transmission lines and other conductive paths on the surface. This can damage the electrical grid.

However, the location of the sunspot on the Sun largely determines the direction in which the CME expands out from the Sun. In reviewing the literature on the Halloween 2003 X28 (X45?) flare, I note that it occurred on November 4, when sunspot group 486 was nearing on the SW limb of the Sun. Any CME associated with that flare was aimed nearly 90° away from the Earth and would have delivered a glancing blow to the Earth, or none at all.