YSI DIQ/S 182 XT-4-MOD - Manual (Page 22)

Installation System 182 XT-4
3 - 8 ba76028e01 02/2012
in the grounding of the mounting construction.
This creates a set path for the main surge. As a result it is possible
to avoid the surge being discharged via the IQ S
ENSOR N ET cable
and via the valuable sensors in the measuring medium.
4 The contacts of the MIQ modules must always be protected by the
associated contact covers if they are not in use. The contact cover
provides improved insulation against the electric fields of a
thunderstorm event through the extension of the air and creepage
paths.
5 It is recommended to attach a metallic or nonmetallic sun shield to
each outside location of the MIQ modules. Sun shields protect the
electric field lines in the area of the MIQ module through an
advantageous development of the electrical field lines in the area of
the MIQ module and promote the dissipation of the surge via the
mounting construction.
6 The mains voltage for supplying the measuring system must comply
with overvoltage category II. Generally this is ensured through the
public operator of the power supply networks. In company-owned
networks, e.g. in all power supply systems owned by wastewater
treatment plants, this must be kept separate by a potential
equalization and a surge protection system for the plant.
7 One part of the IQ S ENSOR N ET safety and lightning protection
concept is based on high-grade protective insulation of the network
components and of the entire system. It does not have or require
any protective ground (PG) conductor or earth terminal. Avoid any
direct connection of the IQ S
ENSOR N ET connections or the metallic
sensor enclosures with the local grounding or potential equalization
system and with metallic construction elements (see point 9).
8 Additional external lightning protection measures directly on the
IQ S ENSOR N ET system or its components, e.g. the use of
overvoltage surge arresters, are not necessary for protection
against the indirect effects of lightning and could possibly result in
malfunctions.
9 For the realization of the internal lightning protection of the system
(e.g. wastewater treatment plant control stands) and for the
protection of IQ S
ENSOR N ET external resources, cable entry points
into buildings or distributions coming from the IQ S ENSOR N ET must
be carried out as follows:
– The shield of SNCIQ or SNCIQ-UG cables can be connected to
the local potential equalization with a gas overvoltage surge
arrester. Shielding terminals (e. g. of the Modbus system) have
to be used to contact the shield. The shield of the cable must not
be opened under any circumstances.
– 0/4-20 mA interfaces must be realized with shielded cables. The
cable shield must be connected directly to the potential