단일동조 저차 고조파 필터뱅크 과도회복전압

Abstract

Industrial power systems include lots of non-linear loads which draw in non-sinusoidal currents. These non-sinusoidal currents are harmonic sources in the power systems, leading to power quality issues. A typical way to solve the power quality issues is to install single-tuned harmonic filter banks in parallel that provide low impedance paths for harmonic currents at their tuning orders, allowing for harmonic mitigation. Depending on harmonic orders, single-tuned harmonic filter banks have different switching characteristics: high amplitude and frequency back-to-back inrush currents of high-order harmonic filter banks; and high transient recovery voltage of low-order harmonic filter banks. This paper focuses on the latter to offer beneficial insights on power system design for safe and reliable harmonic filter bank switching. Theoretical analysis with electromagnetic transient studies describes how the high transient recovery voltage occurs in the low-order harmonic filter banks during the open operation of a circuit breaker. A field measurement on a second-order harmonic filter bank with 30 MVar and 33 kV proves that an excessive transient recovery voltage of approximately 92 kV can appear across the circuit breaker terminals. Lastly, this paper discusses the gap between this excessive voltage generated in a field and the test voltage specified in the IEC standard.