86
DMC3S - Manual - 08 - 2021
—
Synchrocheck relay (Synchro check) - 25
Preface
The synchro check function checks that the connection between two grids (synchronous or asyn-
chronous) can be made without risking the stability of the power system.
A typical application is the synchronisation of two bars by means of a coupler.
Measurement inputs
The grid voltages measured at the inputs are used:
• V
1
: the reference measurement: the parameter
Voltage measurement for synchro check
in the menu
Set \ Base
selects the parameter (phase voltage
U
L1
,
U
L2
U
L3
)
[1]
.
• V
2
voltage measurement (phase-ground) to be synchronised. The input otherwise used to measure
the residual voltage is used (clamps MV5-MV6); the selection uses the parameter
Measurement
UE or V2
in the menu
Set \ Base
.
[1]
Output relays
The synchro check function can activate one or more output relays according to the usual matrix
assignment criterion.
You must select Pulse mode (menu
Set \ Relay
) and program the duration according to the specifi-
cations of the breaker.
The devices uses the measured difference in frequency between the two grids to determine whether
the grids are
synchronous
or
asynchronous
.
Synchronous grids
For
synchronous
grids
the final relay is commanded (synchronisation ok) when the following con-
ditions obtain:
• the trip signal (keypad, logical input or communication) is active,
• the block input signal (keypad, logical input or communication) is inactive,
• the breaker is open,
• the control of inputs
V
1
and
V
2
(function 74VT) is ok,
• the two measured frequencies are in the permitted operating range (
f
n
±
f
RANGE
) for an adjustable
time of no less than
t
STAB
,
• the difference, which defines the synchronous grid condition, between the two measured frequen-
cies is less than an adjustable threshold (
d
f
-GRID
) for an adjustable time of no less than
t
STAB
,
• the value of the two voltages is between a minimum threshold (
V
min-SYNC
) and a maximum thresh-
old (
V
max-SYNC
), both adjustable, for an adjustable time of no less than
t
STAB
,
• the difference between the voltages
V
1
and
V
2
(with
V
1
>
V
2
) is less than an adjustable threshold
(
dV
12
-SYNC
), or the difference between
V
2
and
V
1
(with
V
1
<
V
2
) is less than an adjustable thresh-
old (
dV
21
-SYNC
), for an adjustable time no less than
t
STAB
,
• the phase shift between
V
1
and
V
2
(with
V
2
delayed relative to
V
1
) is less than an adjustable thresh-
old (
dp
12
-SYNC
), or that between
V
1
and
V
2
(with
V
1
delayed relative to
V
2
) is less than an adjusta-
ble threshold (
dp
21
-SYNC
), for an adjustable time no less than
t
STAB
,
• the above conditions persist for a time no less than the adjustable parameter (
t
SYNC
).
If any of the above conditions does not obtain, the close command is not issued.
Note 1 This parameter can only be modified at Level 1
BUSBAR 1
BUSBAR 2
25
Close command
DMC3
V
2
V
1
Synchronisation of two bars
Regulation ranges for the synchronisation check function (25)
dv12-SYNC
dv21-SYNC
dp12-SYNC
(V2 delayed relative to V1)
dp21-SYNC
(V2 in advance of V1)
{ {
V2
V1
V
Asynchronous grids
Synchronous grids
f
df-GRID
dv21-SYNC
(V2>V1)
df21-SYNC
(f1<f2)
dv12-SYNC
(V1>V2)
df12-SYNC
(f1>f2)
