In typical North American residences, a pole transformer supplies two leg 120 V electrical service to a home. My service is rated at 200 A. If I were to draw excess current from the triplex service cable running from the pole to the meter socket, what device protects the cable from overcurrent?
There isn't one
Just your main breaker. That's it.
The presumption is that the area prior to the main breaker is exceedingly simple, with nothing tapped there, so a problem there would be unlikely.
That's also why this is a bad idea.
Collecting data about electrical accidents is what the NFPA does for a living, so clearly, "unlikely" is proven out by statistical analysis. If incidents were occurring at a rate of concern, they would be acting to deal with it, and their NEC codebook or UL standards would soon be updated to reflect it.
It wouldn't take a whole lot to add a fusible link to the input bussing of a meter, so that's an easy action UL can simply mandate. If it were necessary. The fact that they haven't says a thing or two.
Twenty-five years ago I was panicked by a forecast of an ice storm and decided to cut off a tree branch hanging over my service drop. I was standing on a fiberglass ladder up against the power pole and working a manual pole saw.
I barely nicked the insulation of my service drop--loud bang, big spark, one or two teeth burned off the saw blade, but no interruption in service. The fuse on the transformer did not blow.
The branch was incompletely cut and now hanging on the wire. With a heavy heart I called the power company. One guy appeared later that afternoon in a bucket lift truck. He detached my service at the pole, cut away the branch, examined the service drop after separating the wires, and pronounced it still usable (applied tape IIRC), then reconnected it at the pole. No charge.
I have always wondered if the conductor was damaged.
I have had the luck , a few times, of finding a short which knocked out 1 of the phases to a service. I have learned that there are fuses on the backside of the meter to protect their equipment. However, I am unfamiliar if the new digital meters have this protection in the same way or if it is internal. Their rating on residential units are 10,000 amp short circuit protection which translates into around 1 million watts of flash and heat in that moment of the short. Commercial typically has 50,000 amp short circuit protection. The grid has other points that will open as needed to protect the infrastructure.