Siemens 7sg15 microtapp - Voltage Measurement; Current Measurement; Status; Outputs

7SG15 MicroTAPP Description of Operation
©2013 Siemens Protection Devices Limited Chapter 1 Page 5 of 38
3.1.1 Voltage Measurement
The VT input to the relay is measured against the target settings applied via the menu system. The voltage is only
used for measurement if the voltage quality is confirmed as satisfactory by the voltage monitor.
The relay will respond to a voltage which is outside the set-point deadband and initiate a timing interval prior to
operation of the transformer tap changing mechanism.
3.1.2 Current Measurement
The transformer load current is measured from the output of a current transformer (CT) connected either at the
transformer secondary terminals or at the transformer secondary side circuit breaker (CB). The settings menu
enables the phase connection and polarity of the CT which is to be used for measurement in a particular
installation to be entered into the relay.
The measurement of transformer current is used by the relay to: -
1 Calculate the group connected load and provide network Load Drop Compensation (LDC).
2 Calculate circulating reactive current and change the effective voltage measurement in proportion to the
magnitude of the current and so encourage a tap change operation that will reduce the circulating current.
3 Provide on-line readings and historic data.
MicroTAPP relays use the MicroTAPP Peer to Peer Communication system (MPPC) for the transfer of load
information to other relays allowing each relay to determine the summed site load and power factor.
3.1.3 Status
Plant signals connected to the relay status inputs are allocated to relay functions from the setting configuration
menu and indicated by the input matrix in Figure 1.
3.2 Outputs
Dependent on the actions required, the output matrix, Figure 1, is allocated for function from the relay menu
system. Internal relays can be operated to control the tap changer action, initiate alarms and drive indications.
V & I
measurement
Input
Matrix
Status
inputs
MicroTAPP
communications
Voltage control
algorithms
Voltage
monitor
Tap change
monitor
Tap position
inputs
Output
relays
Output
matrix
IEC870
communications
V measurement
Figure 1