Ordinarily electronic voltage transformers (EVTs) are calibrated off-line and the calibration procedure requires complex switching operations, which will influence the reliability of the power grid and induce large economic losses. To overcome this problem, this paper investigates a 110 kV on-site calibration system for EVTs, including a standard channel, a calibrated channel and a PC equipped with the LabView environment. The standard channel employs a standard capacitor and an analogue integrating circuit to reconstruct the primary voltage signal. Moreover, an adaptive full-phase discrete Fourier transform (DFT) algorithm is proposed to extract electrical parameters. The algorithm involves the process of extracting the frequency of the grid, adjusting the operation points, and calculating the results using DFT. In addition, an insulated automatic lifting device is designed to realize the live connection of the standard capacitor, which is driven by a wireless remote controller. A performance test of the capacitor verifies the accurateness of the standard capacitor. A system calibration test shows that the system ratio error is less than 0.04% and the phase error is below 2′, which meets the requirement of the 0.2 accuracy class. Finally, the developed calibration system was used in a substation, and the field test data validates the availability of the system.

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The paper presents an absolute measurement method of determining the voltage coefficient(VC) of high voltage capacitive dividers(CVD) by serial summation of voltage transformers. Under a series of double-voltages, by successively comparing a CVD with a full-insulated transformer, a semiinsulated transformer and their series, the VC of the CVD were gotten. The method was verified by using two voltage transformers rated with ( ) ( ) 110 3 kV 100 3 V in series. Index Terms -Current comparator, gas compressed capacitor, voltage coefficient，voltage ratio, voltage transformer.

In this work, a linear birefringence measurement method is proposed for an optical fiber current sensor (OFCS). First, the optical configuration of the measurement system is presented. Then, the elimination method of the effect of the azimuth angles between the sensing fiber and the two polarizers is demonstrated. Moreover, the relationship of the linear birefringence, the Faraday rotation angle and the final output is determined. On these bases, the multi-valued problem on the linear birefringence is simulated and its solution is illustrated when the linear birefringence is unknown. Finally, the experiments are conducted to prove the feasibility of the proposed method. When the numbers of turns of the sensing fiber in the OFCS are about 15, 19, 23, 27, 31, 35, and 39, the measured linear birefringence obtained by the proposed method are about 1.3577, 1.8425, 2.0983, 2.5914, 2.7891, 3.2003 and 3.5198 rad. Two typical methods provide the references for the proposed method. The proposed method is proven to be suitable for the linear birefringence measurement in the full range without the limitation that the linear birefringence must be smaller than π/2.

wavelength of the optical signal, considering that the practical FBG has a finite reflection bandwidth, unlike the ideal one mentioned above. Here, it has been expected that the optimum time delay may be achieved near the wavelength corresponding to the 3-dB bandwidth position in the long-wavelength side of the reflection spectrum with no voltage applied to the electrode, without significant variations in the output microwave-signal power. The measured time delay, as a function of the control voltage, is shown in Figure 3 for an optical-signal wavelength of ϳ1550.24 nm and a microwave-signal frequency of 2 GHz. The achieved time delay is about 100 ps for the control-voltage range from 5 to 11 V, which corresponds to electrical power consumption of about 280 mW. The measured time delay for the voltage rage below 5 V is relatively small and exhibits an irregular relationship with the applied voltage, which is not suitable for practical use. This may be due to the fact that the FBG used is not sufficiently chirped for voltage below 5 V, and thus the reflection positions of the optical signal are not clearly defined. Surely, the achievable time delay can be readily increased by lengthening the tapered FBG. For the achieved time delay of 100 ps, the maximum distance between the reflection positions of the optical signal is about 10 mm. And the variation in the time-delayed microwave signal power is less than 2 dB. Finally, our TTD has been successfully operated for the broad microwave frequency range from 1 to 10 GHz. CONCLUSIONIn summary we have presented a photonic TTD based on sidepolished fiber Bragg grating with resistive heater. It features voltage-controlled continuous operation involving no moving parts and no mechanical perturbation. FDTD ANALYSIS WITH MODIFIED MATRIX PENCIL METHOD FOR THE UC-EBG LOW-PASS FILTERS

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