Operational Settings; System Power Factor Settings - Siemens 7sg15 microtapp Operation Manual

7SG15 MicroTAPP Commissioning

7.3 Operational Settings

Switch all tap change controls to auto and allow relays to achieve balance.
Make fine adjustments to Basic, Bandwidth and LDC settings. Correct adjustment of the deadband setting should
be greater than the tapping interval of the transformer tap changer, i.e. for a tapping interval of 1.25% the band
setting will be an absolute minimum of ±0.625% (plus a small margin for safety). Using this setting a tap change
operation will always return the voltage to the centre of the target band. If after a period of operation an excessive
number of tap change operations are made, the band setting can be widened.
Monitor voltage levels, transformer loads and operation counter over a period (at least 2 weeks) to confirm correct
system operation under various load conditions.

7.4 System Power Factor Settings

Whether the relay is selected to operate in TAPP or circulating current Voltage Control Method, the target power
factor must be set accurately. This is because the relay reverts to TAPP from circulating current if a fault on the
MPPC KANBUS is selected. Also the Line Drop Compensation is also normalised to the target power factor. If the
System Power Factor is not set closely to the true load power factor then a system voltage error will exist.
Therefore ideally the power factors of all relays should be checked when the voltage control scheme is fully
operational and the power system normalised. The power factors used to derive the relay setting should be
recorded when the group MVA loading is near to maximum. It is therefore necessary to record the displayed
Power Factor and Group Load over a period of time to arrive at the best setting to apply to the relays. An average
of all of the power factors from the transformers or substations running in parallel should be used as the System
Power Factor Setting applied to all of the relays.
An example of this is covered in 4.1 of the Applications Guide.
©2012 Siemens Protection Devices Limited Chapter 7 Page 10 of 10