Transformer Model for TRV at Transformer Limited Fault Current Interruption

Transformer Model for TRV at Transformer Limited Fault Current Interruption

Masayuki Hikita (Kyushu Institute of Technology, Japan), Hiroaki Toda (Kyushu Institute of Technology, Japan), Myo Min Thein (Kyushu Institute of Technology, Japan), Hisatoshi Ikeda (The University of Tokyo, Japan), Eiichi Haginomori (Independent Scholar, Japan) and Tadashi Koshiduka (Toshiba Corporation, Japan)
DOI: 10.4018/978-1-4666-1921-0.ch007
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Abstract

This chapter deals with the transient recovery voltage (TRV) of the transformer limited fault (TLF) current interrupting condition using capacitor current injection. The current generated by a discharging capacitor is injected to the transformer, and it is interrupted at its zero point by a diode. A transformer model for the TLF condition is constructed from leakage impedance and a stray capacitance with an ideal transformer in an EMTP computation. By using the frequency response analysis (FRA) measurement, the transformer constants are evaluated in high-frequency regions. The FRA measurement graphs show that the inductance value of the test transformer gradually decreases as the frequency increases. Based on this fact, a frequency-dependent transformer model is constructed. The frequency response of the model gives good agreement with the measured values. The experimental TRV and simulation results using the frequency-dependent transformer model are described.
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Transient Recovery Voltage

When a circuit breaker interrupts a current, a voltage across the circuit breaker contacts is generated to oppose the non-linear change of the interrupted current, due to a circuit transient phenomenon. This voltage is called the transient recovery voltage (TRV), which is the voltage difference between the source side and the load side of the circuit breaker.

Figure 1 shows three typical transient voltages that are generated when interrupting simple resistive, capacitive, and inductive circuits. In the case of resistive circuit interruption (Figure 1(a)), the TRV (VS-VL) is a simple sinusoidal system voltage with a maximum value of 1.0 p.u. In capacitive circuit interruption (Figure 1(b)), the TRV (VS-VL) will appear as a (1 - cos) wave with a maximum value of 2.0 p.u. following current interruption. In inductive circuit interruption (Figure 1(c)), the TRV (VS-VL) will appear as a sinusoidal system voltage following a high-frequency oscillatory voltage wave caused by the inductive circuit and the stray capacitance.

Figure 1.

Transient recovery voltage of simple circuit models

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