Schweitzer Engineering Laboratories SEL-351 - Setting SYNCP; Accuracy

3-40 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Setting SYNCP
SEL-351 Relays with wye-connected voltages:
The angle setting choices (0, 30, …, 300, or 330 degrees) for setting SYNCP are referenced to V
A
,
and they indicate how many degrees V
S
constantly lags V
A
. In any synchronism check application,
voltage input VA-N always has to be connected to determine system frequency on one side of the
circuit breaker (to determine the slip between V
S
and V
A
). V
A
always has to meet the "healthy
voltage" criteria (settings 25VHI and 25VLO - see Figure 3.26). Thus, for situations where V
S
cannot be in phase with V
A
, V
B
, or V
C
, it is most straightforward to have the angle setting choices
(0, 30, …, 300, or 330 degrees) referenced to V
A
.
Note on setting SYNCP = 0:
Settings SYNCP = 0 and SYNCP = VA are effectively the same (voltage V
S
is directly
synchronism checked with voltage V
A
; V
S
does not lag V
A
). The relay will display the setting
entered (SYNCP = VA or SYNCP = 0).
SEL-351 Relays with delta-connected voltages:
The angle setting choices (0, 30, …, 300, or 330 degrees) for setting SYNCP are referenced to
V
AB
, and they indicate how many degrees VS constantly lags V
AB
. In any synchronism check
application, voltage input VA-VB always has to be connected to determine system frequency on
one side of the circuit breaker (to determine the slip between V
S
and V
AB
). V
AB
always has to meet
the "healthy voltage" criteria (settings 25VHI and 25VLO - see Figure 3.26). Thus, for situations
where V
S
cannot be in phase with V
AB
, V
BC
, or V
CA
, it is most straightforward to have the angle
setting choices (0, 30, …, 300, or 330 degrees) referenced to V
AB
.
Note on setting SYNCP = 0:
Settings SYNCP = 0 and SYNCP = VAB are effectively the same (voltage V
S
is directly
synchronism checked with voltage V
AB
; V
S
does not lag V
AB
). The relay will display the
setting entered (SYNCP = VAB or SYNCP = 0).
See the Application Guide entitled Compensate for Constant Phase Angle Difference in
Synchronism Check with the SEL-351 Relay Family for more information on setting SYNCP
with an angle setting.
Accuracy
Voltage Pickup: ±1 V and ±5% of setting {150 V voltage inputs}
±2 V and ±5% of setting {300 V voltage inputs}
Voltage Transient Overreach: ±5% of setting
Slip Pickup: 0.003 Hz
Angle Pickup: ±4°
Courtesy of NationalSwitchgear.com