Procedure for Verifying Population Exposure Limits to the Magnetic Field from Double-Circuit Overhead Power Lines

The verification of the limits of the population’s exposure to the magnetic field generated by double-circuit power lines from field measurements carried out on site is not trivial. It requires knowledge of the power line current instant values during the measurement period, the determination of the relationship between current and field at the measurement points (made more complex by the double-circuit overhead line configuration) and the use of that relationship to extrapolate the field values. Nevertheless, the verification of exposure limits for double-circuit power lines from on-site measurements is often conducted with rough, or not particularly stringent, procedures. A practical and straightforward procedure of general validity for non-optimized double-circuit lines is proposed here. No specific measurement position or conductors disposition knowledge is required as well as no complex three-dimensional finite element method code is necessary. The procedure, potentially also applicable to high- and extra-high-voltage lines, is validated on a medium-voltage (15 kV) double-circuit overhead power line study case. Exposure limits assessment suggests that if the line is operated at its rated capacity (230/285 A), the 3 μT quality target is missed. Results are provided with a 95% confidence interval ranging from ±100 nT to ±140 nT in all the cases.

Improvement of DC Fault Current Limiting and Interrupting Operation of Hybrid DC Circuit Breaker Using Double Quench

In this paper, direct current (DC) fault current limiting and interrupting operation of hybrid DC circuit breaker (DCCB) using double quench, which consists of DCCB, a series resonance circuit, power electronic switch, surge arrestor, two separated current limiting reactor/resistor, and two superconducting elements, were suggested. The suggested hybrid DCCB can perform the interrupting operation after twice or once DC fault current limiting operation according to DC fault current amplitude. To verify the effective operation of the suggested hybrid DCCB, the modeling for the components of DCCB, the surge arrestor, and the SCE was carried out and its DC operational characteristics were analyzed. Through the analysis of the modeling results for the suggested hybrid DCCB, the advantages of hybrid DCCB were discussed.

Digital Implementation Method for Synchronous PWM Control of GaN Transistor at Zero-Crossing of Totem-Pole PFC in Energy Storage Applications

A digital control scheme for GaN transistor-based totem pole power factor correction (PFC) is proposed in this paper. At the zero crossing, the totem pole PFC has a discontinuous conduction mode (DCM) current section because of its driving method and circuit structure. In the DCM current section, when a typical synchronous switching technique is applied, the inductor current is reduced to less than zero, thereby reducing efficiency. Moreover, because of the nature of the circuit, power may be transferred in reverse. To prevent this, a new synchronous switch technique using the cycle by cycle (CBC) trip function of the digital signal processor (DSP) is proposed. This proposed technique turns off the synchronization switch according to the set DCM level. Consequently, even at a low DCM level, the inductor current is clamped to zero, enabling stable synchronous switching.