Patent ID: 11892488
Assignee: HITACHI ENERGY LTD
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 1:
2. The method according to claim 1, wherein the number of transformer bushings is three in a three-phase set up, wherein:
estimating the absolute value for the capacitances of each of the bushings comprises estimating an absolute value for the capacitances of each of the bushings of the three phases, the absolute values for the capacitances being denoted C1, C2, and C3,
estimating the absolute value for the loss factor or the power factor of each of the bushings comprises estimating an absolute value for the loss factor or the power factor of each of the bushings of the three phases, the absolute values for the loss factors or the power factors being denoted F1, F2, and F3, and
calculating Δ-values for all C values and Δ-values for all F values comprises calculating three Δ-values for C1, C2, and C3 and three Δ-values for F1, F2, and F3, according to:

ΔC1=C1−C2,

ΔC2=C2-C3,

ΔC3=C3-C4,

ΔC4=C4−C1 

ΔF1=F1−F2,

ΔF2=F2−F3,

ΔF3=F3−F4,

ΔF4=F4−F1.