Alstom MBCH13 - Ratio and Phase Matching Interposing Transformers; Details of Matching Transformers; Notes on Combinations of Windings

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4.3 Ratio and phase matching interposing transformers
Matching transformers are available for use in cases where the current transformers
on one side of the protected transformer do not match, in current ratio or phase
angle, with the current transformers on the other side of the protected transformer.
The following versions of matching transformer are available:
Description Reference No
Single phase transformer 1/1A GJ0104 010
Single phase transformer 5/5A GJ0104 020
Single phase transformer 5/1 GJ0104 030
Three phase transformer 1/1A GJ0104 050
Three phase transformer 5/5A GJ0104 060
Three phase transformer 5/1A GJ0104 070
4.3.1 Details of matching transformers
The winding details of the three current ratings of the matching transformers are given
in the table below and in Figure 10.
Number of turns
Transformer rating
Primary
tap terminals 1/1A 5/1A 5/5A
1 – 2 5 1 1
2 – 3 5 1 1
3 – 4 5 1 1
4 – 5 5 1 1
5 – 6 125 25 25
X 7 25 5 5
7 – 8 25 5 5
8 – 9 25 5 5
S1 – S2 125 125 25
S3 – S4 90 90 18
Table 1.
Notes on combinations of windings.
For star-output windings:
It is permissible to use either S1-S2 or S1-S4 (with S2-S3 linked). Where S1-S2 alone
is used, the secondary winding S3-S4 is available for formation of an isolated delta
connection to prevent zero sequence currents due to external earth faults being seen
by the relay. This is for applications where phase correction is not required, but
where a zero sequence trap is needed.
For delta output windings:
S1-S4 (with S1-S3 linked) must be used to obtain optimum protection performance.