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336
FUNCTION CHARACTERISTICS
• all the conditions listed above should be maintained at least fon an adjustable value (
t
SYNC
).
In the absence of one or more conditions listed above the closing command is not issued.
Control functions
The following parameters are cyclically monitored:
• Instability in the measurement of frequency; if the measures are unstable a message is output and
if the difference between consecutive measurements of frequency is higher than the adjustable
value (
Rof>
SYNC
parameter) the parallel execution is stopped. With
Rof>
SYNC
= 0 setting the stability
control is disabled.
• State of the VTs monitoring function; in case of faults detection on the VTs secondary connections,
(VTs fuses trip p, MCB trip), 74VT element trip if enabled, the parallel execution is stopped.
Operating logic
The synchronization sequence of can be started by impulsive command generated by:
• digital input programmed as
Start synchro check,
• local control via the front keypad by activating the
button (closure),
• command from the communication interface.
At synchronization start, control checks are performed (see previous paragraph). If any condition is
incorrect a
Fault Sync
message is displayed and the closing sequence is interrupted.
If, however, the tests are positive the sequence is started (
SYNC - n IN PROGRESS
n, with n = 0,
1, 2, according to the selected operating mode.
Depending on the selected operating mode, only the concerning condition are verified.
In the presence of both input voltages (mode 0), the device checks if the two grids are synchronous
or asynchronous by means of the difference of the measured frequency and the
Df-
SYNC
threshold: if
the difference is below the threshold the grids are considered synchronous.
Suitable messages indicate the different operating states:
•
SYNC - DeltaV ok, SYNC - Deltaf ok, SYNC - Delta-phi ok
,...
•
SYNC - DeltaV NOT OK, SYNC - Deltaf ,NOT OK, SYNC - Delta-phi NOT OK
,...
If the conditions are met, the sync function outputs an enable signal for closing.
The length of the enable signal is adjustable by selecting the
Operation MODE
parameter as
PUL-
SE
and setting the length (Minimum pulse width) to the desired value for the output relay; parame-
ters are available in the
Set \ Board 1 outputs
menu.
The maximum time allowed to attempt synchronization (
timeout
-SYNC
) can be set inside the
Set \
Profile A (or B) \ Synchro check - 25 \ Common configurations
menu; if the conditions are not met
within it the sequence is stopped.
Advance closing command
In the case of
asynchronous
grids the output relay must be be closed (synchronism ok) in advance
so that the CB closure takes place in conditions of perfect synchronism.
According to the closing time of the circuit breaker and to the measures of the slip frequency and
the phase shift of the measured voltages V1 and V2 the device determines the instant of the next
synchronization. The closing command is issued at a time that precedes that of synchronization of a
value equal to the time calculated in advance according to the frequency difference (Af).
The electrical angle in advance required to compensate for the CB closing delay is defined by the
relation:
A
= 360 ∙ (
t
CB-CLOSE
+
t
MEAS
) ∙ ∆f
where:
- 0.12
- 0.10
- 0.08
- 0.06
- 0.04
- 0.02
- 0.124
- 0.122
0.120
- 0.118
- 0.116
0.120 s
Close command
advance closing angle : 8.6 °
f
1
= 50 Hz
f
2
= 50.2 Hz
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021