Schweitzer Engineering SEL-351P - Overvoltage Element Operation Example; Voltage Elements Used in POTT Logic; Synchronism Check Elements

Date Code 990430 Overcurrent, Voltage, Synchronism Check, and Frequency Elements 3-35
SEL-351P Manual Técnico
Overvoltage Element Operation Example
Refer to
Figure SECTION 3: .21 (bottom of the figure).
Pickup setting 59P1P is compared to the magnitudes of the individual phase voltages V
A
, V
B
, and
V
C
. The logic outputs in Figure SECTION 3: .21 are the following Relay Word bits:
59A1 = 1 (logical 1), if V
A
> pickup setting 59P1P
= 0 (logical 0), if V
A
≤ pickup setting 59P1P
59B1 = 1 (logical 1), if V
B
> pickup setting 59P1P
= 0 (logical 0), if V
B
≤ pickup setting 59P1P
59C1 = 1 (logical 1), if V
C
> pickup setting 59P1P
= 0 (logical 0), if V
C
≤ pickup setting 59P1P
3P59 = 1 (logical 1), if all three Relay Word bits 59A1, 59B1, and 59C1 are asserted
(59A1 = 1, 59B1 = 1, and 59C1 = 1)
= 0 (logical 0), if at least one of the Relay Word bits 59A1, 59B1, or 59C1 is
deasserted (e.g., 59A1 = 0)
Voltage Elements Used in POTT Logic
Refer to
Figure SECTION 3: .21 and Figure SECTION 3: .22. Note that voltage elements
27A1, 27B1, 27C1, and 59N1 are also used in the weak-infeed portion of the POTT logic, if the
weak-infeed logic is enabled (see Figure 5.6).
If the weak-infeed portion of the POTT logic is enabled (setting EWFC = Y) and these voltage
elements are used in the logic, they can still be used in other applications (if the settings are
applicable). If the weak-infeed portion of the POTT logic is not enabled, these voltage elements
can be used in any desired application.
S YNCHRONISM C HECK E LEMENTS
Enable the two single-phase synchronism check elements by making the enable setting:
E25 = Y
Synchronism check voltage input VS is connected to one side of the circuit breaker, on any
desired phase. The other synchronizing phase (VA, VB, VC or voltage inputs) on the other side
of the circuit breaker is setting-selected.
The two synchronism check elements use the same voltage window (to assure healthy voltage)
and slip frequency settings (see
Figure SECTION 3: .24). They have separate angle settings (see
Figure SECTION 3: .23).
If the voltages are static (voltages not
slipping with respect to one another), the two synchronism
check elements operate as shown in the top of
Figure SECTION 3: .23. The angle settings are
checked for synchronism check closing.