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7SG15 MicroTAPP Application Guide
MicroTAPP
Figure 1
4.3 Parallel
Transformers
When transformers are operated in parallel at a site use of the MPPC link between each voltage control relay
enables accurate LDC at all times. Figure 2 shows the general MPPC arrangement for a multiple transformer site.
If a MicroTAPP is de-energised, communication between other relays connected to the twisted pair cable is not
affected.
MPPC
communications
MicroTAPP
MicroTAPP
MicroTAPP
MicroTAPP
Figure 2
In more complex sites transformers may operate in groups with the busbar split, making two effective load
groupings. Regardless of the transformer grouping the MPPC should always be connected to each relay. Where
operational requirements necessitate changes to the busbar configuration and LDC is used, consideration must
be given to the MicroTAPP relay settings.
Take an example of four transformers normally operating in two groups, i.e. two on each bus-bar as shown in
Figure 2. The site can be operated as a single busbar with four transformers in parallel or as a two busbar site
with each busbar supplied from two transformers.
©2011 Siemens Protection Devices Limited
Chapter 5 Page 6 of 21