METREL EurotestCOMBO MI 3125 User Manual

MI 3125 / BT EurotestCOMBO Appendix D
84
D Appendix D - IT supply systems
In order for operator to be familiar enough with measurements in and their typical
applications in IT supply system it is advisable to read Metrel handbook Measurements
on IT power supply systems.
D.1 Standard references
EN 60364-4-41, EN 60364-6, EN 60364-7-710, BS 7671
D.2 Fundamentals
In IT systems live parts are insulated from earth or connected to earth through
sufficiently high impedance.
133 V
133 V
L1
L2
230 V
133 V
L3
230 V
230 V
Optional
high
impedance
N (Optional) IMD
Figure D.1: General IT supply system with reference designations
 Three phase star connection, optional delta connection.
 Optional neutral line.
 Single-phase connection is also possible.
 Various system voltages possible.
 One faulty connection of any line to PE is treated as first fault and is regular but it has to
be repaired as soon as possible.
Testing of IT supply system is slightly different to standard tests in TN / TT system.
D.3 Measurement guides
The user has to select the IT supply system in the instrument before testing it. The
procedure for selecting the IT supply system is defined in chapter 4.2.9 Supply earthing
system. Once the IT system is selected the instrument can be used immediately. The
instrument keeps selected IT system when it is turned off. Displayed designations
correspond to IT system, see figure D.1.

METREL EurotestCOMBO MI 3125 Specifications

General

Brand	METREL
Model	EurotestCOMBO MI 3125
Category	Measuring Instruments
Language	English