Siemens 7sg15 microtapp Operation Manual page 81

9.6 Transfer Tap Positions
As described in the first section of this manual some tap changers have special positions which operate to re-
arrange the winding configuration but do not alter the voltage. When at these positions a single tap change control
will result in more than one tap change operation which must be recognised for correct operation of the runaway
prevention system. These positions may be indicated as the same position and labelled with suffix letters, i.e. 8A,
8B, 8C.
A system that allows for customisation of the tap position as indicated on the tap change mechanism is integrated
into the TPI set-up menu, accessed by use of a 'tap customisation sub-menu from the '/settings/tap-changer'
menu. If a tap position is maintained as the same position through the 'transfer' cycle, the positions can be re-
numbered as the same position. For example, 7, 8, 8, 8, 9. To indicate that these tap positions are special, they
must also be marked as 'T' to indicate a transfer position, in this case 7, 8T, 8, 8T, 9. It is important that the tap
positions above the transfer point are also re-numbered.
The commissioning section of this manual gives details of the tap changer set-up procedure and correct
determination of the number of 'physical' tap positions.
9.7 MicroTAPP Peer to Peer Communications (MPPC)
At a site, load and status information is passed between MicroTAPP relays by the MPPC system which is a
screened twisted pair cable. The cable used should be a 22-swg shielded twisted pair cable with drain wire. The
maximum cable length is of the order of several hundred meters
B3 B1
B7
MicroTAPP 1
MPPC line terminator
link
Each end of the MPPC cable must be connected to a line terminating resistor which is included within the
MicroTAPP at terminal B7, the connections to which are made by linking from B3 to B7 on the first and last relay
of the cable route as shown by Figure 14. The MPPC cable screen must be connected to earth at a SINGLE point
only, again shown in Figure 14.
©2011 Siemens Protection Devices Limited
B0
B1
Tap
B2
position
B3
Switch
B4
B5
COM
+12V supplied
by MicroTAPP
Figure 13
B5
B7
Intermediate
MPPC screen earthing
at a single point
MPPC Inter-MicroTAPP connections
Figure 14
7SG15 MicroTAPP Application Guide
MicroTAPP
B9
B11
B13
B15
B17
B19
B21
B3 B1 B5
MicroTAPP
MPPC Screend twisted
pair cable
B5 B1 B3
B7
MicroTAPP N
MPPC line terminator
link
Chapter 5 Page 17 of 21