Electrical Power System Essentials

1.3 GENERAL CHARACTERISTICS OF POWER SYSTEMS

Most of the power systems are 50 Hz or 60 Hz three-phase AC systems. The voltage levels used are quite diverse. In the following sections we explain why these choices have been made.

1.3.1 AC versus DC Systems

The choice for AC systems over DC systems can be brought back to the ‘battle’ between Nicolas Tesla (1856–1943) and Thomas Alva Edison (1847–1931). Edison managed to let a light bulb burn for 20 hours in the year 1879. He used a 100 V DC voltage and this was one of the main drawbacks of the system. At that time a DC voltage could not be transformed to another voltage level and the transportation of electricity at the low voltage level of 100 V over relatively short distances already requires very thick copper conductors to keep the voltage drop within limits; this makes the system rather expensive. Nevertheless, it took quite some time before AC became the standard. The reason for this was that Edison, besides being a brilliant inventor, was also a talented and cunning businessman as will become clear from the following anecdote. Edison tried to conquer the market and made many efforts to have the DC adopted as the universal standard. But behind the scenes he also tried hard to have AC adopted for a special application: the electric chair. After having accomplished this, Edison intimidated the general public into choosing DC by claiming that AC was highly dangerous; the electric chair being the proof of this! Eventually AC became ...