Distribution systems around the world have evolved into different forms. The two main designs are North American and European. For both forms, they are similar on the types of following:
Both systems are radial, voltages, and power carrying capacities are similar. The main difference are in layouts, configurations, and applications.
European system have larger transformers and more customer per transformer. Most European transformers are three phase and on the order of 300-1000 kVA. North American has 25 or 50 kVA single phase units.
North America has standardized on a 120/240 V secondary system. European countries have a standard secondary voltage of 220,230, or 240 Volts. With twice the voltage as that in North America, a circuit feeding the same load can reach over four times the distance.
Each type of system has its advantages and disadvantages. Some of the major differences between systems are the following:
COST. The European system is generally more expensive, but for the types of loads and lay outs in Europe, the European system fits quite well. Nonetheless, European primary equipment is generally more expensive especially for areas that can be served by single-phase system.
FLEXIBILITY. North American system has more flexible primary design, and the European system has a more flexible secondary design.
SAFETY. The multi-grounded neutrals of the North American primary system provides many safety benefits. It can more reliably clear faults, and the neutral acts as a physical barrier as will as helping to prevent dangerous touch voltages during faults.
RELIABILITY. Generally, North American designs result in fewer customer interruption. European system have less primary, and almost all of it is on the main feeder backbone. Loss of the main feeder results in an interruption for all customers on the circuit. European system needs more switches and other gear to maintain the same level of reliability.
POWER QUALITY. Generally, European system have fewer voltage sags. Its three wire system helps protect against sags during line to ground fault. It also has less momentary interruptions as a result of less primary exposure .
AESTHETICS. Having less primary, the European system has an aesthetic advantage. The secondary is easier to do underground. For underground systems, fewer transformer locations and longer secondary reach make sitting easier.
THEFT. The flexibility of the European secondary system makes power much easier to steal. Developing countries especially have this problem. Secondaries are often strung along or on top of buildings; this easy access does not require great skills to attach to.
Outside of Europe and America, both systems are used, and usage typically follows colonial patterns with European practices being more widely used. Some regions of the world have mixed distribution systems, using bits of both practices.