Introduction
14
Operating instructions RHF
ELTROPLAN
-
REVCON
Elektrotechnische Anlagen GmbH
3 Introduction into the subject harmonics
3.1 The effect of harmonics in a power distribution system
In figure 2 a transformer is connected on the primary side to a common point of cou-
pling PCC1 on the medium voltage supply. The transformer has an impedance Z
T
und
supplies a number of loads.
At a common coupling point PCCP2 all loads are connected. Each load is connected
through wires that have the corresponding impedances Z
1
, Z
2
und Z
3
:
Figure 2: The effects of harmonics
Harmonic currents drawn by non-linear loads cause distortion of the voltage because
of the voltage drop on the impedances of the distribution system. Higher impedances
result in higher levels of voltage distortion.
Current distortion relates to the device performance and it relates to the individual
load. Voltage distortion relates to system performance .It is not possible to determine
the voltage distortion in the PCC knowing only the load’s harmonic performance .