Siemens siprotec SJ62 User Manual page 150

Logic
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The disk emulation evokes a dropout process (timer counter is decremented) which
begins after de-energization. This process corresponds to the reset rotation of a Fer-
raris-disk (explaining its denomination "disk emulation"). In case several faults occur
successively the "history" is taken into consideration due to the inertia of the Ferraris-
disk and the timing response is correspondingly adapted. This ensures a proper sim-
ulation of the temperature rise of the protected object even for extremely fluctuating
unbalanced load values. Reset begins as soon as 90 % of the setting value is under-
shot, in correspondence with the dropout curve of the selected characteristic. In the
range between the dropout value (95 % of the pickup value) and 90 % of the setting
value, the incrementing and the decrementing processes are in idle state.
Disk emulation offers advantages when the behaviour of the negative sequence pro-
tection must be coordinated with other relays in the system based on electromagnetic
measuring principles.
The following figure shows the logic diagram for the negative sequence protection
function. The protection may be blocked via a binary input. This resets pickup and time
stages and clears measured values.
When the negative sequence protection operating range is left (i.e. all phase currents
below 0.1 x I or at least one phase current is greater than 4 x I
Nom
issued by the negative sequence protection function are reset.
2.7 Negative Sequence Protection 46
), all pickups
Nom
148