With all of the electronics in a home, one fails to realize that the ground is also a REFERENCE for your water pipes, your CATV and your COMPUTERS.
If, for instance, a fault to ground exists on one circuit, it will not raise the potential of others.
That's a simple explanation although a computer center was taken down because lightning can change the Earth's potential so the reference on each side of a building can be different. When you have devices that use as little as 5V to communicate, you have problems.
The fix, replace connections from one side of the computer center to another with fiber.
In ground Swimming pools require lots of attention because of ground potentials.