According to AS1243 - 1982, Page 22, Voltage Transformers (VT's) can be categorised into 2 categories:- Category A - VT's intended to supply phase-phase burdens only, in which case error limits are applicable to the phase-phase voltages. Category B - VT's intended to supply phase-neutral burdens only, in which case error limits are applicable to the phase-neutral voltages. Then in the following notes is states:- 2. The errors for Category A performance can be derived from the errors obtained for Category B performance and in any case cannot exceed 2/sqrt(3) times the errors for Category B performance. 3. The derivation of errors for Category B performance from the errors obtained for Category A performance is not valid.
Does anyone know where the 2/sqrt(3) comes from or where I could find the derivation for converting the error between Categories?
Cheers!