qtla9111, look at ANY grid. Look up at the distribution poles. Not the transmission towers, the poles. See the 4 wires?
A SINGLE Y wound 3 phase transformer feeds an electrical grid that extends many square blocks. This means 3 phases plus a neutral. Dozens and dozens of residential "mufas", service drops.
Now tiptoe north of the border and attempt to find a similar grid system. You will not find one. What you will find are tens of thousands of individual transformers. One or two services drops at most for residences.
NOB businesses will have a 3-phase DELTA wound transformer.
Now travel to the nearest CFE distribution station, the one where high tension lines are dropped to 12.5KV neighborhood 3-wire networks. Do you see any phasing capacitors alongside the large ground based transformers? The ones that keep X1, X2 and X3 synched with H1, H2 and H3 ?
USA or Canadian power would never in a million years connect a three phase 100 or 200 horsepower ammonia ice plant compressor motor to the same X1, X2, and X3 transformer SOURCE junction as neighborhood Y transformer H1, H2, and H3 connections. Yet it is common in Mexico. CFE is upgrading yes, but the old totally vulnerable grid connection protocols exist in 90% of neighborhoods.
I like what CFE is doing. I just toured a state of the art 11.04 megawatt turbine plant that for crying out loud replaced a generation plant consisting of 4 generators powered by General Motors railroad locomotive engine generators. Ultra modern computer grid monitoring.
But and this is a big but, 90% of Mexico is still connected the old fashioned way. The line harmonic distortion on the old grid plus the noise from transients can make an oscilloscope operator queasy.
But even that does not matter when you have an RV park full of units with roof air units switching on and off. The inductive reactance from a few dozen roof airs (never mind phasing balance and transients) is enough to make a person wish they never heard of integrated circuits and "chips".
The best system smoothly corrects for high or low voltage WITHOUT NEED TO "SWITCH" or "STEP" INTERIOR CIRCUITRY. The second in line device is an isolation transformer. A ferroresonant line regulator and isolation transformer (it has to be grounded!) is the "best" way to handle these problems but by far it isn't the most practical or feasible way.
Most "surge protectors" cure about 2% of line problems (other than simple voltage) that adversely affect lifespan of solid state components.
