Chopping of Transformer Magnetizing Currents Part I: Single Phase Transformers

Tuohy, E. J.; Panek, J.

doi:10.1109/tpas.1978.354477

“…This is given in the manufacturer's test report as 9.6, equivalent to an angle of 84.05°. Then, 0.654 cos 84.05° 0.0677  (22) and .…”

Section: 5ωmentioning

confidence: 98%

Snubber Design for Transformer Protection

Sutherland

¹

,

Valdes²,

Fox

³

2016

IEEE Trans. on Ind. Applicat.

5

0

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Historically, failures of distribution transformers due to transient overvoltage phenomena has led to the development of Resistor-Capacitor snubber circuits for the protection of the transformer and winding insulation. These transients are most often observed when dry-type transformers are close coupled to vacuum switching devices. Typically, snubber circuit design has been specific for the particular application, and complex engineering studies were required. However, the design of a snubber circuit itself may be performed without these detailed studies. If snubber studies are required, the procedures for system modeling and simulation are explained in a step by step manner.

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“…At high frequencies, for fast flux variations, the saturation and hysteresis of the transformer core can be neglected. The second case requires only the saturation and hysteresis [23], [24]. In order to calculate the electromagnetic transients accurately, one should consider the residual flux, because of its influence on the generation of overvoltage.…”

Section: Transformer Modelingmentioning

confidence: 99%

Improved calculations for no-load transformer switching surges

Popov

¹

,

Sluis

²

2001

IEEE Trans. Power Delivery

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Abstract-This paper deals with a modeling of components and calculation of transient overvoltages that build up on the transformer primary terminals after the transformer has been switched off by a vacuum circuit breaker (VCB). The transformer is connected to the circuit breaker by a cable. The transient overvoltages are calculated for different cable lengths, and the cumulative probability of different arc angles is investigated.In this study two cases are considered: transient overvoltages due to steady-state magnetizing current switching, and transient overvoltages due to inrush current switching. It is shown that the case of inrush current switching is worse, as virtual current chopping is possible. The cable is modeled by pi sections, whereas the transformer model is based on a terminal impedance. The VCB re-ignitions are modeled by means of withstand voltage characteristics and high-frequency quenching capability. Due to shortage of field tests, this work uses only literature references to compare the results with actual measurements.

show abstract

“…At high frequencies, for fast flux variations, the saturation and hysteresis of the transformer core can be neglected. The second case requires only the saturation and hysteresis [23], [24]. In order to calculate the electromagnetic transients accurately, one should consider the residual flux, because of its influence on the generation of overvoltage.…”

Section: Transformer Modelingmentioning

confidence: 99%

Improved Calculations for No Load Transformer Switching Surges

Popov

¹

,

Sluis

²

2001

IEEE Power Eng. Rev.

View full text Add to dashboard Cite

Abstract-This paper deals with a modeling of components and calculation of transient overvoltages that build up on the transformer primary terminals after the transformer has been switched off by a vacuum circuit breaker (VCB). The transformer is connected to the circuit breaker by a cable. The transient overvoltages are calculated for different cable lengths, and the cumulative probability of different arc angles is investigated.In this study two cases are considered: transient overvoltages due to steady-state magnetizing current switching, and transient overvoltages due to inrush current switching. It is shown that the case of inrush current switching is worse, as virtual current chopping is possible. The cable is modeled by pi sections, whereas the transformer model is based on a terminal impedance. The VCB re-ignitions are modeled by means of withstand voltage characteristics and high-frequency quenching capability. Due to shortage of field tests, this work uses only literature references to compare the results with actual measurements.

show abstract

Chopping of Transformer Magnetizing Currents Part I: Single Phase Transformers

Cited by 15 publications

References 8 publications

Snubber Design for Transformer Protection

Snubber Design for Transformer Protection

Improved calculations for no-load transformer switching surges

Improved Calculations for No Load Transformer Switching Surges

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