11 Resistance symmetry (RSym)
ARGUS Copper Box
57
2. Measureing site, e. g. demarcation point:
The demarcation point is not earthed. The
cable shield is interrupted at the site shown
in the illustration. However, the resistance
symmetry measurement can still work if the
cable shield at the demarcation point is con-
nected to one of the earthing points shown in
the picture. However, the RE measurement
is not Rshield, as the shield can have an
ground potential of varying quality due to the
lead sleeve in the ground (obsolete constuc-
tion method). The ground potential can also come from a network of building accesses
(other earthed demarcation points) in the branch cable: In the main cable area, the ground
potential can come from another cable branch box. In practice, a combination of the two
examples is quite common. All these effects lead to varying RE measurements.
3. TAE (residence)
Resistance symmetry is often faulty in the
last mile, e. g. due to a poor splice (rat-tail
splice, poorly crimped conductor connec-
tions, loose screw connection).
A measurement is possible if the last mile is
a connected to a buried, continuous shield
conductor this case is not illistrated). How-
ever, This is seldom the case. Thus, you
must either lay an auxiliary conductor, e. g.
from the potential equalistion point to the measurement, or use earthed harting pipes in the
residence.
If does not work, trained electricians can, after checking the bulidung mains configuration
(TN-S, TT), use the PE (protective ground) line as an earthing point after verifying that it
voltage-free. In general, attention must be paid to ensuring secure contact, particulary to
osidised or corroded earthing points.
4. If can intact conductor is used as an auxil-
ilary conductor instead of ground, RE=RH,
RH is then entirely on the order of magnitude
of Ra and Rb. A complete twisted pair (Tip-
Ring) can also be used for this.
