Calculator #010Transformer sizingIEC 60076

Transformer Sizing & Selection

Preliminary two-winding transformer selection from demand, spare capacity and loading target. IEC 60076-5 Table 1 impedance bands are checked explicitly; parallel units, N+1 availability, impedance tolerance, tap range, loss capitalisation and inrush notes are included as transparent engineering inputs.
Developed by the ieccalc.com engineering team
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Input
Result
Winding configuration and short-circuit impedance
IEC 60076-5 Table 1 and the single-uk model apply to two separate windings only.
Winding-pair data referred to side A, IEC 60909-0:2016, 6.3.2. Each pair carries its own rating, short-circuit voltage and load loss.
PairS_r, kVAu_kr, %P_k, kW
A-B
A-C
B-C
IEC 60909-0:2016, 6.2, Formula (4). Leave 0 to get the transformer-limited current only.
Clause 6.2: use 0,1 where no accurate value is known; the resistance must be included for i_p.
Permitted above 35 kV fed by overhead lines, clause 6.2.
Computed from R/X by IEC TR 60909-1:2002, Formula (68). Fill in only to override.
Governs whether a neutral exists on the faulted side.
Manufacturer figure; 0,95 to 1,0 is usual for a Dyn unit.
Only for an OLTC auto-transformer whose u_k+ and u_k- both sit well above u_kr, 6.3.3 NOTE.
Transformer single-line and branch impedances
Short-circuit current phasors
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