How far you can run underground electric depends on the wire gauge (generally AWG) and the circuit voltage. Too much voltage drop in an electrical circuit can negatively affect performance, so the smaller the voltage drop, the better. Ideally, it shouldn't exceed 3%. The smaller the wire and the longer the run, the more significant the voltage drop. 

For example, with a 120-volt circuit, you can run 60 feet of 12 AWG cable without losing more than 3% voltage. With a 240-volt circuit, you can run 120 feet of 12 AWG wire while maintaining a voltage drop of 3% or less.

By nature, two-prong outlets aren't grounded—but the box they run to might be, which makes them safer. The safest way to test if an outlet is grounded is to purchase a circuit tester, which cost about $20 at home improvement stores. 

If you discover your outlet (or outlets) aren't grounded, know that this greatly increases your risk of personal injury and electrical fires. You may want to consider installing new three-prong ground fault circuit interrupter (GFCI) outlets. On average, the cost to install GFCI outlets is about $210 per outlet.

If wiring in a relatively modern home is damaged due to sudden events like a fire, a tree falling into the house, or a flood, then homeowners insurance is very likely to cover the cost of replacing the wire.

However, if it’s determined that wiring failed or started the fire because of age, neglect, or not meeting current electrical standards, then insurance won’t be covering any replacement. Also, insurance policies may charge more for particularly old kinds of wiring like aluminum wiring or deny applications altogether. 

Unless you’re a licensed electrician with extensive experience in upgrading electric panels, you must hire a professional for any electrical work. A licensed electrician will make sure your breaker is upgraded safely and in compliance with local codes. Your pro will also take care of any permits and inspections that are needed.