BECKWITH ELECTRIC M-3425A, Instruction Book

Page: 184 / 482

4–53
System Setup and Setpoints – 4
25 Sync Check

NOTE
: The 25 function cannot be enabled under
any one of the following conditions:
• 67N (Residual Directional Overcurrent)
is enabled and the polarizing quantity
has been set to V
X
.
• 59D is enabled and the line side voltage
is set to V
X
.
• 59X is connected for turn-to-turn fault
protection or bus ground protection.
The Synchronism (Sync) Check function (25) is
used to ensure that the voltage magnitude, phase
angle and frequency of the generator (V1) and the
utility system (V
X
) are within acceptable limits before
the generator is synchronized with the system.
Generator voltage (V1) can be selected as A, B,
or C (line-to-ground and line-ground to line-line) or
AB, BC, or CA (line-to-line).
The sync check function includes phase angle, delta
frequency, and delta voltage checks.
Phase Angle Check
The phase angle is considered acceptable when
the selected sync phase voltage (V1) and system
voltage (V
X
) are within the Upper Volt Limit and
Lower Volt Limit window and the measured phase
angle is within the phase angle window.
Phase Angle Window is defined as twice the Phase
Angle Limit setting. For example, if the Phase Angle
Limit is set at 10 degrees, a phase angle window
of 20 degrees exists between –10 degrees and
+10 degrees. The logic diagram of the phase angle
check is shown in Figure 4-33.
Delta Voltage and Delta Frequency Check
Delta Voltage and Delta Frequency elements may
be individually enabled or disabled, as desired.
The Delta Voltage check will compare the absolute
difference between the selected sync phase voltage
(V1) and the measured system voltage (V
X
) with
the Delta Voltage Limit setting. Likewise, the Delta
Frequency measures the frequency difference
between V1 and V
X
voltage signals. The Phase
Angle Check, Delta Voltage and Delta Frequency
Check all combine through an appropriate timer with
the output directed to the programmed 25S output
contact. A logic diagram representing this logic is
presented in Figure 4-33.
Dead Line/Dead Bus Check
The Dead Volt Limit defines the Hot/Dead voltage
level used in Deadline/Dead Bus closing schemes.
When the measured V
X
voltage is equal to or below
the Dead Volt Limit, V
X
is considered dead. When
the measured V
X
is above the Dead Volt Limit, V
X
is considered hot. The opposite side of the breaker
uses the positive sequence voltage measurement
(V1) for 3-phase consideration in determining hot/
dead detection. Different combinations of hot line/
dead bus closings may be selected, depending on
how the buses are referenced. A logic diagram of
the Deadline/Dead Bus scheme is presented in
Figure 4-33.
The Dead V1, Dead V
X
, and Dead V1 & V
X
enable
are software switches used to enable the dead
line/dead bus logic. Further conditioning can be
performed on the dead detection logic by selecting
one or more input contacts (Dead Input Enable)
to control the enabled dead detection element.
For example, if INPUT2 (I2) is selected under the
Dead Input Enable screen, and both the Dead V1
and Dead V
X
elements are enabled, the dead check
timer will start when INPUT2 is activated, and either
V1 dead/V
X
hot or V1 hot/V
X
dead. This allows for
external control of the desired dead closing scheme.
Dead Input Enable selections are common to all
dead detection elements. If no inputs are selected
under the Dead Input Enable screen, and any dead
element is enabled, the dead check timer will start
immediately when the dead condition exists.
The 25S and 25D can be programmed to be sent
to two different contacts, if desired.

NOTE
: The 25 function does not produce a
target or LED and is accompanied by the
HMI message “F25 Function Operated”.