Siemens 7SC80 Manual page 226

Functions
2.12 Monitoring Functions
= | i + i + i + i
Ι
F A B C
Σ I THRESHOLD (address 8106) and Σ I FACTOR (address 8107) are setting parameters. The component Σ
I FACTOR · Σ | Ι | takes into account the allowable current proportional ratio errors of the input transducers
which are particularly prevalent during large fault currents
[stromsummenueberwachung-020313-kn, 1, en_US]
Figure 2-62
An error in the current sum results in the message
function. Furthermore, a fault log is initiated for a period of 100 ms.
The monitoring can be switched off.
The monitoring is available subject to the following conditions:
•
The ground current of the current transformer starpoint is connected to the 4th current input (Ι
green circuit). This is communicated to the device in the Power System Data 1 via address 280 YES.
•
The settings CT PRIMARY (address 204) and Ignd-CT PRIM (address 217) must be the same.
•
The settings CT SECONDARY (address 205) and Ignd-CT SEC (address 218) must be the same.
The following logic diagram illustrates the operational mode of the current sum monitoring.
[7sc80-stromsummenueberw-20110520, 1, en_US]
Figure 2-63
226
| > Σ I THRESHOLD + Σ I FACTOR · Σ | Ι |
E
Current sum monitoring
Logic diagram for the fast current sum monitoring
(Figure 2-62). The dropout ratio is about 95 %.
Failure Σ I (No.162) and blocking of the protection
E50417-G1140-C486-A8, Edition 07.2017
) (Holm-
4
SIPROTEC Compact, 7SC80, Manual