Electrical Connection; Preparing The Connection - Vega VEGASCAN 693 Operating Instructions Manual

Electrical connection

Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Select connection cable
Cable screening and ground-
ing
Select connection
cable for Ex applica-
tions
12
5 Electrical connection

5.1 Preparing the connection

Always observe the following safety instructions:
Connect only in the complete absence of line voltage
l
If overvoltage surges are expected, overvoltage arresters
l
should be installed
Tip:
We recommend VEGA overvoltage arresters B61-300 (power
supply VEGASCAN 693) and B62-36G (sensor supply).
In hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the
sensors and power supply units.
The power supply can be 20 ... 253 V AC, 50/60 Hz.
Power supply of VEGASCAN 693 is connected with standard
cable acc. to the national installation standards.
Standard two-wire cable with screening can be used for
connecting the sensors. The screening is absolutely neces-
sary to ensure interference-free operation with HART sensors.
Connect the cable screen on both ends to ground potential. In
the sensor, the screen must be connected directly to the
internal ground terminal. The ground terminal outside on the
sensor housing must be connected to the potential equal-
isation (low impedance).
If potential equalisation currents are expected, the screen
connection on the VEGASCAN 693 must be made via a
ceramic capacitor (e.g. 1 nF, 1500 V). The low frequency
potential equalisation currents are thus suppressed, but the
protective effect against high frequency interference signals
remains.
Take note of the corresponding installation regulations for Ex
applications. In particular, make sure that no potential equal-
isation currents flow over the cable screen. In case of
grounding on both sides this can be achieved by the use of a
capacitor or a separate potential equalisation.
VEGASCAN 693 - 15-channel HART signal conditioning instrument