Planning the electrical installation 39
Selecting the control cables
All control cables must be shielded.
Use a double-shielded twisted pair cable for analog signals. Employ one individually
shielded pair for each signal. Do not use common return for different analog signals.
A double-shielded cable (figure a below) is the best alternative for low-voltage digital
signals but single-shielded (b) twisted pair cable is also usable.
Signals in separate cables
Run analog and digital signals in separate, shielded cables.
Never mix 24 V DC and 115/230 V AC signals in the same cable.
Signals allowed to be run in the same cable
Relay-controlled signals, providing their voltage does not exceed 48 V, can be run in the
same cables as digital input signals. It is recommended that the relay-controlled signals be
run as twisted pairs.
Relay cable type
The cable type with braided metallic screen (eg, ÖLFLEX by LAPPKABEL, Germany) has
been tested and approved by ABB.