Setting Notes - Siemens siprotec SJ62 User Manual

Time Delays / Logic
Figure 2-56 Logic diagram of the frequency protection
2.9.2

Setting Notes

General
Minimum Voltage
Pickup Values
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
Each frequency element has an associated settable time delay. When the time delay
elapses, a trip signal is generated. When a frequency element drops out, the tripping
command is immediately terminated, but not before the minimum command duration
has elapsed.
Each of the four frequency elements can be blocked individually by binary inputs.
The following figure shows the logic diagram for the frequency protection function.
Frequency protection is only in effect and accessible if address 154 81 O/U is set to
Enabled during configuration of protective functions. If the fuction is not required
Disabled is set. The function can be turned ON or OFF under address 5401 FCT 81
O/U.
Address 5402 Vmin is used to set the minimum voltage. Frequency protection is
blocked as soon as the minimum voltage is undershot.
On all three-phase connections and single-phase connections of a phase-to-phase
voltage, the threshold must be set as a phase-to-phase value. With a single-phase
phase-to-ground connection the threshold is set as a phase-to-ground voltage.
The nominal system frequency is programmed in Power System Data 1, and the
pickup settings for each of the frequency elements 81-1 PICKUP to 81-4 PICKUP
determines whether the function will be used for overfrequency or underfrequency
protection. Set the pickup threshold lower than nominal frequency if the element is to
2.9 Frequency Protection 81 O/U
172