Calculating The Leakage Resistance - Siemens SIMATIC ET 200SP System Manual

Calculating the leakage resistance

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
CPU/interface module
BaseUnit BU15...D
BaseUnit BU30-MSx
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
ET200SP
R
module
N
R
CPU/IM
R
CPU/IM
R
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.
295
Ohmic resistance
Module
= R / N
module
= Leakage resistance of the ET 200SP
= Leakage resistance of a module
= Number of BaseUnits BU15...D and interface module in the ET 200SP
= R = R
BU15...D Module
= Leakage resistance of CP/interface module
= Leakage resistance of the BaseUnit BU15...D
Ohmic resistance from RC network
= 9.5 MΩ
System Manual, 09/2019, A5E03576849-AJ
C
10 MΩ (±5 %)
10 MΩ (±5 %)
10 MΩ (±5 %)
Distributed I/O system