Neutral point shift
In electrical engineering, a neutral point shift (also known as neutral point voltage ) is a cause of an (abnormally high) voltage potential that occurs in the event of a fault in a three-phase alternating current network .
description
The neutral conductor , which does not carry any electrical current in a three-phase AC or three-phase network with uniform or symmetrical loading of the three conductor phases, becomes a current-carrying conductor when the three conductor phases are loaded differently. In the case of a symmetrical load, as is common, for example, with a single three-phase machine or an electric water heater , a neutral conductor can therefore be dispensed with. However, asymmetrical loading is more the rule in larger three-phase AC networks, as these rarely have an even load on all of their outer conductors .
Failure
If the neutral conductor is missing in an asymmetrically loaded three-phase AC network (e.g. due to a line break), the neutral point shift occurs. As a result, the currents that otherwise flow back through it are distributed to the other two outer conductors. The consequence of this is that the line voltages may differ greatly from their usual values. In the three-phase alternating current network , voltages of up to 400 volts can thus be present on circuits that are intended for single-phase alternating current , with the result that the equipment connected to it is destroyed. The graphic on the right shows the effect of the neutral point shift, for example equipment that is connected to the outer conductor U3 is exposed to a much higher voltage than normal.
Individual evidence
- ↑ Steffen, Bausch: Electrical engineering: Fundamentals . 6th edition. Teubner, Wiesbaden 2017, ISBN 978-3-8351-0014-5 , p. 266 .