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The SYNCHK_RY function consists of several over-voltage and under-voltage and
synchronizing relays (OV, UV, and SyncRys) integrated within the synchronization check
feature (SYNCHK). The SYNCHK function issues permissive signals to the DPSY functions;
hence, ensuring that the DPSY functions are only able to close the CB when the required
conditions for closure have been satisfied.
SYNCHK_Ry:
Function ID: 561001
OVr relay (59r) for running line
OVi relay (59i) for incoming line
UVr relay (27r) for running line
UVi relay (27i) for incoming line
SyncRy (ΔV)
SyncRy (Δθ)
SyncRy (Δf)
SyncRy (θ≈0)
SYNCHK; Function
ID: 560001
Verification of voltage
conditions and
synchronization between
networks
Permission signal
issued to DPSY
logics
Figure Outline of SYNCHK function
†Note: The DPSY function is discussed separately. See Chapter
Control and monitoring
application: Double position controller with synchronizing-check
.
‡Note: To simplify the description, only the SYNCHK1 (SYNCHK_Ry1) function is
discussed; however, the same description is applicable to the SYNCHK2
(SYNCHK_Ry2) function. The user should read the expression for SYNCHK1 as
SYNCHK2 unless a special explanation or instruction has been provided (e.g., the
user can reason by analogy that the feature in the OVr2 relay is identical to the
OVr1 relay).
4.6.1 Relays to check line-outage
The voltage condition for either line being out of service or being in service is verified using OV
and UV relays in the SYNCHK_Ry1 function.
Table 4.6-2 Settings in SYNCHK_Ry1
Checking Live-Running Voltage
Checking Dead-Running Voltage
Checking Live-Incoming Voltage
Checking Dead-Incoming Voltage
(i) Overvoltage-relay elements (OVr1, OVi1)
Two overvoltage-relay elements (OVr1 and OVi1) are provided to determine the voltage
presence between running and incoming lines. In Figure 4.6-1 the hatched area depicts the
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