Manual 37351A
MFR 11 Packages - Protection Relay
© Woodward
Page 31/59
Control Functions
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Synchronization (
Packages SC
&
SC+N
)
NOTE
The
Package SC
is not available for 690 V units; refer to Synchronizing Voltage (Packages
on page 14.
Output of the Signal "Systems are Synchronous"
After the control unit monitors voltages and frequencies are within permissible limits, it will issue a circuit
breaker closure command to connect two systems. The closure command has a predefined minimum on time that
is output to a relay. Relay 3 is dedicated to this function. Relay 2 can also be assigned with this function for re-
dundancy purposes starting with SW version 3.1450.
The maximum permissible limits are:
•
Generator System (GN): 75% to 112.5% of the rated voltage
•
Mains System (MN): 87% to 112.5% of the rated voltage
Function
"Synchronization of systems"
The control unit calculates internally the electrical angle of advance to issue the circuit breaker closure command.
The corresponding lead-time remains constant due to the inherent delay of the breaker regardless of the fre-
quency differential of the two systems. If the voltage and frequency differential of the two systems are within
permissible limits, the breaker closure command may be issued under the following conditions:
•
The respective monitored voltages of the two systems must be greater than 75 % and less than 112.5 % if the
configured rated voltage.
•
The monitored voltage differential of the two systems must fall below the configured maximum permissible
voltage differential.
•
The monitored frequency differential of the two systems must fall below the configured maximum permissi-
ble frequency differential
•
The electrical angle between two coincident phases must be smaller than the respective permissible error an-
gle (slip-dependent, max. 8 °elec.).
Synchronous Networks
A network is considered as synchronous if the frequency difference between the systems is less than 0.02134 Hz.
The unit also issues a breaker closure order for synchronous networks, as long as the electrical angle between the
two systems does not exceed the maximum permissible phase angle and the monitored voltage differential is less
than the configured maximum permissible voltage differential.
