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I understand very well. I have worked for electric utility companies in Ohio, Philadelphia and Houston. That includes working in engineering planing department and modeling transmission lines for short circuit analysis.

True isolation of grids requires both grids to have spinning reserves and standby reserves for generating capacity. Although many large substation already have multiple transmission lines feeding them, the majority of the substation in the United States do not.

The majority of the transmission line corridors do not contain multiple circuits. Although many do exist, there are more miles of single circuit corridors than multiple. The single line corridors would require build-out to do as you suggest.

I do not know what experience you have in protective device coordination and transmission line distance relaying, but what you suggest is a staggering expense with little improvement. Breaking the US into smaller isolated grids without adding redundancy will increase the number of power outages. Unscheduled line failures from tree limbs, vandals and fatigue do happen. When you reduce the ability to reroute power through a large connected grid, you increase the number and duration of outages the customer will see.

I am not surprise that towers get replaced. Steel, even galvanized steel with a sacrificial anode system will see some corrosion. As Houston was the third city in the world to install an electric distribution system, some of it is old.

Some SCADA systems have their communication fail quickly, some are using systems over 40 years old.

Ok, I agree, true isolation would require spinning reserves etc.

Ok, I agree, single line corridors would require additional lines. The utilities I have worked with have required two line and two paths.

What I don't understand is why you think fault isolation and redundant grids would not improve reliability. I also do not see where I would be reducing the ability to reroute power. Please explain.

I also do not understand why you think such a configuration would not add redundancy. Perhaps this is a difference in design but all of the substations that I have worked were either already redundantly connected or such redundancy was being reworked/restored (single leg till tower was replaced, RTU upgrades, normal O&M stuff, etc.)

I do not know what experience you have in protective device coordination ...

I THINK this is where FirstEnergy has failed ... AEP (American Electric Power) initiated a MAJOR upgrade of their 'protection systems' starting in about 1998 using "Cooper Power Systems' new Edison® Pro relays" as detailed here The Line, December 1997, AEP?s Development of a Substation Integration and Automation System.

MAJOR inprovements in sensing line conditions and power flow along with positive/assured breaker control probably saved them (they didn't collapse on August 14th).

The Edison® Pro series of relays also has bult-in logging of events including waveform capture (oscillographic recording) - I'll be interested to see what this shows leading up to the Aug 14 collapse.