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4.2 Quick Logic Applications
4.2.1 Auto-Changeover Scheme Example
INCOMER 1
CB1
Busbar 1
The MV installation illustrated above is fed from two incomers. To limit the substation fault level the busbar is run
with CB3 open. When a fault occurs on one of the incomers it is isolated by the circuit protection. To re-supply the
disconnected loads from the remaining incomer CB3 is closed.
If the line fault occurs on incomer 1 it must be confirmed that CB 1 has opened before CB3 can be closed. The
relay on incomer 1 confirms that a trip has been issued to CB1 (e.g. Binary Output 2), that CB 1 has opened (e.g.
Binary Input 1) and that no current flows in the circuit (e.g. 37-1 = Virtual 1):
Incomer 1 Relay is Configured:
CB1 Open auxiliary switch wired to BI 1
Trip output to CB1 = BO 2
OUTPUT CONFIG>OUTPUT MATRIX: 37-1 = V1
OUTPUT CONFIG>OUTPUT MATRIX: E1 = BO3
CONTROL & LOGIC>QUICK LOGIC: E1 = O2.I1.V1
The output from Incomer 1 (Binary Output 3) relay is input to the relay on CB 3 (Binary Input 1). A panel switch
may be used to enable the On-Load Change-over scheme (Binary Input 2). Before Closing CB3 a check may be
made that there is no voltage on busbar 1 (27/59-1 = Virtual 1). CB 3 is closed from Binary Output 3.
CB3 Relay is Configured:
Panel switch (ON-Load Change-over Enabled) wired to BI2
OUTPUT CONFIG>OUTPUT MATRIX: 27/59-1 = V1
OUTPUT CONFIG>OUTPUT MATRIX: E1 = BO3
CONTROL & LOGIC>QUICK LOGIC: E1 = I1.I2.V1
If required a time delay can be added to the output using the CONTROL & LOGIC > QUICK LOGIC: E1
Pickup Delay setting.
© 2018 Siemens Protection Devices Limited
Panel Enable
Start On-Load
Change-over
BO3
BI 1
VT1
CB1
V 1
OPEN
LOADS
Figure 4-3
Example Use of Quick Logic
7SR10, 7SR11, 7SR12 Applications Guide
Switch
BI 2
Start On-Load
Change-over
VT2
Vx
CB3
LOADS
INCOMER 2
CB2
Busbar 2
Chapter 7 Page 32 of 41
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