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TGH1266E - 05/04
General
Basic Standards
Terms and
Definitions
If a power supply is constructed as an IT system, the relevant standards require that the first
insulation fault to occur must be eliminated as quickly as possible.
IEC 364-4-41, Point 413.1.5.4 (Note)
It is recommended that the first fault should be eliminated with the shortest practical delay.
DIN VDE 0100 Part 410:1983-11, Point 6.1.5.7
It is recommended that the first insulation fault should be eliminated as quickly as possible.
Rapid insulation fault location is made possible thanks to insulation fault location devices such as
the EDS3065, EDS470 or RCMS470. In this way, the risk of the power supply being switched off
because of a possible second fault is considerably reduced.
At the present time, work is in progress on IEC1557-9. This document deals with devices for
insulation fault location in operational IT AC systems, IT AC systems with electrically connected
DC circuits and IT DC systems. This international draft standard lays down some special
requirements for insulation fault location devices in IT systems of up to AC 1000 V and DC 1500
V.
BENDER’s insulation fault location devices are based on this draft of IEC1557-9. As far as possible,
this operating manual attempts to use the terminology of the draft Standard, including the term
‘insulation fault location device’. This indicates not only that insulation faults with 0 Ω (faults to
earth) are found, but also insulation faults which involve resistance.
In addition, IEC 1010-1 is applicable. The title of this international Standard is ”Safety
requirements for electrical equipment for measurement, control, and laboratory use”.
I
∆
= fault current. The current which comes to flow through an insulation
fault.
I
∆n
= nominal fault current. The fault current at which the evaluator unit
responds under specified conditions.
I
∆s
= measured value of the discriminating fault current of the evaluator
unit.
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