7SG15 MicroTAPP Application Guide
9.3 Inputs
The standard status inputs to the relay are rated for AC or DC voltages and have a range of 18V to 110V. When
used at higher voltages up to 250V AC or DC, a series dropper resistor must be used as shown in the application
diagrams at the end of this section. Alternately the relay can be specified with alternate voltage ratings, see
performance specification section and order catalogue.
The inputs can be mapped to the required status configuration using the appropriate relay menu. A typical control
scheme is shown at the end of this section.
9.4 Outputs
The standard outputs are relay contacts rated for 250V, AC or DC voltages, and have a current rating of 10A.
The outputs can be mapped to the required function using the relay system configuration menu, a typical control
schemes are shown at the end of this section.
9.5 Tap
Position
Connections are made to the MicroTAPP relay depending on the type of tap position sender unit provided with the
tap changer as shown in Figures 12 and 13. Connections for all TPI sender unit types are provided.
The MicroTAPP monitors the integrity of the tap position. If a resistor type sender unit is used for the signalling of
tap position an extra resistor having a value equal to 1 tap interval resistor must be inserted at the bottom of the
resistor chain as shown in Figure 12. Where resistors are used for determination of tap position sender unit, a
worn or poorly maintained moving contact may become open circuit and the indicator will read tap position ‘0’,
indicating a faulty sender unit.
The total resistance of the resistor chain should be greater than 250
Ω
and less than 100k
Ω
. If the total resistance
is less than 250
Ω
, the short-fall can be made good by increasing the size of the Additional resistor. The value of
this resistor should then be entered in terms of tap steps in the setting "Additional resistor equiv. to". However,
this setting added to the number of tap positions must be less than 40. Resistors should be rated to 1W and to 1%
accuracy.
Tap 1
Top Tap
Moving contact
Resistor type Tap Position Sender Unit
MicroTAPP
B23
B25
B27
Additional
Resistor
Figure 12
Where tap position is signalled from a switch, Figure 13 shows the connections, which are used for True binary,
BCD and Gray code configurations. As with the Resistor type, a reading of tap position ‘0’ will indicate a faulty
sender unit.
©2011 Siemens Protection Devices Limited
Chapter 5 Page 16 of 21