Flux measurements with AC and DC components of current present show transformer equivalent circuit models need core joint details

Borrill, Leslie David; Chisepo, Hilary; Gaunt, C.T.

doi:10.1109/powercon.2016.7753920

Cited by 1 publication

(4 citation statements)

References 19 publications

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“…Conventional design calculations defined an 8.3 kVA, 209/390 V transformer. However, it was stacked with non-step lap butt joints due to factory limitations on core cutting for this size of transformer, and therefore, to avoid early core saturation, the nominal rating was reduced to 110/206 V, 4.4 kVA after practical AC tests (Borrill et al, 2016). To investigate the flux distribution in the core of the transformers, several single-turn search coils were wound around the core as illustrated in Figure 4.…”

Section: Laboratory Measurementsmentioning

confidence: 99%

“…The initial set of tests Need for transformer core joint details involved applying AC voltage from linear operation to over-excitation, identifying the voltage at which saturation commenced: 120 V RMS. A DC injection circuit was derived and implemented to investigate the response of a single-phase transformer under simultaneous AC and DC energization without saturating the source (Borrill et al, 2016). A simplified representation of the test circuit is shown in Figure 5.…”

Section: Laboratory Measurementsmentioning

confidence: 99%

“…A DC injection circuit was derived and implemented to investigate the response of a single-phase transformer under simultaneous AC and DC energization without saturating the source (Borrill et al ., 2016). A simplified representation of the test circuit is shown in Figure 5.…”

Section: Laboratory Measurementsmentioning

confidence: 99%

“…Following the preliminary FEM study, practical laboratory measurements using three single-phase four limb (1p4L) transformers in an adjacent study (Borrill et al , 2016) are compared with the results of 2D and 3D FEM simulation.…”

Section: Introductionmentioning

confidence: 99%

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Measurements show need for transformer core joint details in finite element modelling of GIC and DC effects

Chisepo

Borrill

Gaunt

2018

COMPEL

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Purpose This paper aims to improve the finite element modelling of transformers subjected to DC excitation, by including core joint details. Design/methodology/approach Geomagnetically induced currents (GICs) or leakage DC can cause part-cycle, half wave saturation of a power transformer’s core. Practical measurements and finite element matrix (FEM) simulation were carried out using three laboratory-scale, untanked single-phase four limb transformers resembling real power transformers in terms of the core steel and parallel winding assemblies. “Equivalent air gaps” at the joints, based on AC measurements, were applied to the FEM models for simultaneous AC and DC excitation. Findings Measurements confirm that introducing equivalent air gaps at the joints improves the FEM simulation of transformers carrying DC. Research limitations/implications The FEM simulations based on the laboratory transformers are exemplary, showing the difference between modelling core joints as solid or including equivalent air gaps. They show that, for more representative results, laboratory transformers used for research should have mitred core joints (like power transformers). Originality/value This research shows why joint details are important in FEM models for analysing transformer core saturation in the presence of DC/GICs. Extending this, other core structures of power transformers with mitred joints should improve the understanding of the leakage flux during half-wave saturation.

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Section: Laboratory Measurementsmentioning

confidence: 99%

Section: Laboratory Measurementsmentioning

confidence: 99%

Section: Laboratory Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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