EMC filtre - IT nett
https://www.schaffner.com/fileadmin..._Brochure_Basics_in_EMC_and_power_quality.pdf
3.4 IT network
In an IT system there are two possibilities: either all active parts are
separated from ground, or one point of the system is grounded via a
defined high impedance (RGND).
The setup comes with a number of special issues to be considered
when using filters. For power networks one always considers the
first-fault condition, where one phase is short-circuited to ground.
The advantage of an IT system lies in the fact that in such a fault
condition the risk of high touch currents is negligible. Inside of
the filter, however, the voltage across the capacitors will increase
significantly. If the filter is not specifically designed for IT networks,
there is a good risk of destruction of the capacitors in the case of a
network first fault.
An IT network with a single fault turns into a TN system, but with
increased phase voltages. It continues to function, but for safety
reasons the first fault should be repaired as quickly as possible. In
IT networks, therefore, the insulation of the phases against earth is
constantly monitored. If additional resistors are connected between
line and earth inside connected equipment, the monitoring system
is influenced and might detect non-existing faults. As a result, discharge resistors are not permitted in filters in systems for IT distribution networks.
Schaffner offers a variety of filters especially designed for IT networks, such as FN 258 HVIT and FN 3359 HV. For more details, please
consult the datasheets for the products.
FN 258 HVIT
Filtrene mine,Schaffner FN 2090.
AMS målere og jordfeil rapportering.
https://brage.bibsys.no/xmlui/handle/11250/2392897
file:///C:/Users/Bruker/Downloads/TR+A7539.pdf
Nettfiltre,virker - virker ikke?
Filter/nettimpedans,kilde impedans betyr mest hvor vidt virkningen er
stor,liten/ingen eller til det verre,og selvsagt støybilde (Hz)