ABB REG316 4 Series Operating Instructions Manual page 128

ABB Switzerland Ltd
The function determines the power direction by measuring the
phase-angle of the current in relation to the opposite phase-to-
phase voltage. Which current is compared with which voltage
can be seen from the following table.
Current input Phase-to-neutral voltage
I U , U
R S
I U , U
S T
I U , U
T R
The voltage measurement automatically compensates the group
of connection of the v.t's. For example, the phase-to-phase val-
ues are calculated for Y-connected v.t's (v.t. type UTS), while the
input voltages are used directly for delta-connected v.t's (v.t.
type UTD).
Delay
The delay enables the protection to be graded with other time-
overcurrent relays to achieve discrimination. Its setting is thus
chosen in relation to the timer settings of upstream and down-
stream protective devices. The zone of protection covered by
this overcurrent protection extends to the next overcurrent pro-
tection device.
Should in the event of a fault in the next downstream zone, the
protection for that zone fail, this protection function takes over
after the time set for "Delay" and clears the fault as backup.
3-90
REG 316*4 1MRB520049-Uen / Rev. F
T
R
S
Calculated voltage
U = U - U
ST S T
U = U - U
TR T R
U = U - U
RS R S