Distributed I/O system
290
System Manual, 12/2016, A5E03576849-AG
Calculating the leakage resistance
C
Introduction
If you wish to protect the ET 200SP using a ground-fault detector or a residual current circuit
breaker, then you need the leakage resistance to select the correct safety components.
Ohmic resistance
When determining the leakage resistance of the ET 200SP, you must take into account the
ohmic resistance from the RC combination of the module in question:
Table C- 1 Ohmic resistance
Module
Ohmic resistance from RC network
CPU/interface module
10 M
Ω (±5
%)
BaseUnit BU15...D
10
MΩ (±5
%)
BaseUnit BU30-MSx
10
MΩ (±5
%)
Formula
You can calculate the leakage resistance of the ET 200SP using the following formula if you
protect all of the modules listed above with one ground-fault detector:
R
ET200SP
= R
module
/ N
R
ET200SP
= Leakage resistance of the ET 200SP
R
module
= Leakage resistance of a module
N
= Number of BaseUnits BU15...D and interface module in the ET 200SP
R
CPU/IM
= R
BU15...D
= R
Module
= 9.5
MΩ
R
CPU/IM
= Leakage resistance of CP/interface module
R
BU15...D
= Leakage resistance of the BaseUnit BU15...D
If you protect the modules listed above within an ET 200SP with several ground-fault
detectors, you must determine the leakage resistance for each individual ground-fault
detector.
Summary of Contents for Simantic ET200SP
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