Quick Logic Applications; Auto-Changeover Scheme Example; Figure 4.2-1 Example Use Of Quick Logic - Siemens 7SR21 Manual

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 B.I. 1
Trip output to CB1 = B.O. 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 (BO3) 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 B.I. 1
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 .
©2010 Siemens Protection Devices Limited
Start On-Load
Change-over
BO3
BI 1
VT1
CB1
OPEN
V 1
LOADS

Figure 4.2-1 Example Use of Quick Logic

7SR21 & 7SR22 Argus Applications Guide
Start On-Load
Change-over
VT2
Vx
CB3
LOADS
INCOMER 2
CB2
Busbar 2
Chapter 7 Page 32 of 39