1. In any medium or low voltage three - phase system there are three single voltages measured between each phase and a common point called the "neutral point"
2. In actual fact, the neutral is the common point of three star - connected windings
3. The neutral may or may not be accessible or distributed. Except in specific cases (e.g networks in North America and Australia), the neutral is not distributed at medium voltage. However, the neutral is very often distributed at low voltage
e.g: exempli gratia = for example
 |
| Nối đất trực tiếp :x |
4. In a medium or low voltage installation, the neutral may or may not be earthed. This is why we talk about the earthed system
5. The neutral may be directly connected to earth or connected through a resistor or a reactor. In the first case, we say that the neutral is directly earthed and in the second case we say that it is impedance - earthed
5. The neutral may be directly connected to earth or connected through a resistor or a reactor. In the first case, we say that the neutral is directly earthed and in the second case we say that it is impedance - earthed
