Now the calculation of the maximum differential current in TTurnpoint 2
urnpoint 2 includes the previously
calculated correction factors for the HV and LV side CTs.
Also is needed the corrected transformation ratio effect (
TR
corr
) due to the tap changer position on the
maximum voltage position (usually this generates the highest differential current).
To get the HV volts minimum value the user needs to apply the calculation on a situation when the tap
changer on the secondary side is at maximum output voltage and the output is nominal. In this
example we had a maximum of +12.5% increasing effect from the tap changer, resulting in the
following calculation:
Next we calculate the the currents that flow in the HV and LV sides, when the loading of the
transformer is e.g. 1.5 times its rated power.
Therefore, the LV side currents are as follows:
The currents of the HV side are as follows:
These currents present the worst-case scenario that the tap changer effect can cause to the
differential relay's measured currents.
Next, we need to calculate the differential current. In theory there are two ways to use biasing
calculation to do this, but in practice only one: the results of add and subtract modes are the same
because they just compensate the connected CTs differently (starpoint towards or away from the
transformer). Thus, the differential current is always calculated as follows:
Genera
Generattor Commander
or Commander
Instruction manual
Version: 2.07
266
© Arcteq Relays Ltd
IM00001
Содержание Generator Commander
Страница 1: ...Generator Commander Instruction manual...
Страница 2: ......