Influence of V/Hz Limiter on Generator in Isolated Operation

2011 ◽  
Vol 383-390 ◽  
pp. 5066-5070
Author(s):  
Rui Lan Liu ◽  
Wei Liu ◽  
Peng Liu ◽  
Qian Dou
Keyword(s):  
Low Voltage ◽  
Power Grid ◽  
Low Frequency ◽  
Local Load ◽  
Power Station ◽  
Excitation System ◽  
Hydro Power ◽  
Time Operation ◽  
Long Time ◽  
Operation Status

The action of V/Hz limiter of generator excitation system and its influence on generator in isolated operation are analyzed with the generator in Youjiang hydro power station as an example which is in isolated operation with local load after the trip of main transformer of 500kV Baise substation in Guangxi power grid. It is pointed out that the action of V/Hz limiter is the reason that causes the long time operation of generator under low voltage and low frequency status. Suggestions on the functions of V/Hz limiter and how to avoid such low voltage and low frequency operation status are proposed.

Renovating the View of Cost Sharing for the Underground Low Voltage Cable Projects in Hanoi

2019 ◽  
Vol 35 (5E) ◽  
Author(s):  
Pham Thi Thu Ha ◽  
Phan Dieu Huong
Keyword(s):  
Willingness To Pay ◽  
Cost Sharing ◽  
Low Voltage ◽  
Power Grid ◽  
Field Studies ◽  
Power Industry ◽  
Well Field ◽  
The Subject ◽  
Sharing Responsibility ◽  
The Cost

Underground power grid projects in Hanoi is so urgent that it requires immediate implementation. To synchronously and quickly implement the underground power grid projects, people in charge should not follow the outdated perspectives of just including the power industry, but also need to call for the support and cost sharing responsibility from consumers. This paper aims at approaching the subject both from the producers and consumers’ perspectives to together sharing the cost of putting the power grid underground not only in Hanoi but other metropolitans in Vietnam as well. Field studies (including 104 families) at Hoan Kiem District, Hanoi and CBA method were applied to investigate the willingness to pay (WTP) level of consumers to share the cost with the power industry for the underground power grid projects in Hanoi. The overview of the results shows that cost for the underground power grid in Hoan Kiem District ranging from 30,000 VND/household/month to 46,000VND/household/month. On the other hand, the willingness to pay of a typical household of four people within Hoan Kiem District ranges from 17,000VND/month to 24,000VND/month, with the most favorable method of annual payment within a detailed timeline.

scholarly journals Electromagnetic power of lightning superbolts from Earth to space

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
J.-F. Ripoll ◽  
T. Farges ◽  
D. M. Malaspina ◽  
G. S. Cunningham ◽  
E. H. Lay ◽  
...  
Keyword(s):  
Low Frequency ◽  
Optical Emission ◽  
High Energy ◽  
Very Low Frequency ◽  
Electromagnetic Power ◽  
Power Spectral ◽  
High Energy Tail ◽  
Van Allen Probes ◽  
Long Time ◽  
Low Frequency Waves

AbstractLightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. From burst-triggered measurements, we compute electric and magnetic power spectral density for very low frequency waves driven by superbolts, both on Earth and transmitted into space, demonstrating that superbolts transmit 10-1000 times more powerful very low frequency waves into space than typical strokes and revealing that their extreme nature is observed in space. We find several properties of superbolts that notably differ from most lightning flashes; a more symmetric first ground-wave peak due to a longer rise time, larger peak current, weaker decay of electromagnetic power density in space with distance, and a power mostly confined in the very low frequency range. Their signal is absent in space during day times and is received with a long-time delay on the Van Allen Probes. These results have implications for our understanding of lightning and superbolts, for ionosphere-magnetosphere wave transmission, wave propagation in space, and remote sensing of extreme events.

Fault Detection for Low-Voltage Residential Distribution Systems With Low-Frequency Measured Data

2020 ◽  
Vol 14 (4) ◽  
pp. 5265-5273
Author(s):  
Mehdi Shafiei ◽  
Faranak Golestaneh ◽  
Gerard Ledwich ◽  
Ghavameddin Nourbakhsh ◽  
Hoay Beng Gooi ◽  
...  
Keyword(s):  
Fault Detection ◽  
Distribution Systems ◽  
Low Voltage ◽  
Low Frequency ◽  
Measured Data ◽  
Residential Distribution

Low voltage and low frequency current mirror using a two-MOS subthreshold OP-Amp

1996 ◽  
Vol 32 (7) ◽  
pp. 605 ◽  
Author(s):  
K. Tanno ◽  
O. Ishizuka ◽  
Z. Tang
Keyword(s):  
Low Voltage ◽  
Low Frequency ◽  
Current Mirror ◽  
Op Amp ◽  
Frequency Current

A New Prediction Model on the Luminance of OLEDs Subjected to Different Reverse Biases for Alleviating Degradation in AMOLED Displays

2014 ◽  
Author(s):  
Paul C.-P. Chao ◽  
Yen-Ping Hsu ◽  
Yung-Hua Kao ◽  
Kuei-Yu Lee
Keyword(s):  
Reverse Bias ◽  
High Efficiency ◽  
Life Time ◽  
Density Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Wide Viewing Angle ◽  
Time Operation ◽  
Long Time ◽  
History Of

Organic light-emitting diodes (OLEDs) have drawn much attention in areas of displays and varied illumination devices due to multiple advantages, such as high brightness, high efficiency, wide viewing angle, and simple structure. However, the long-time degradation of OLED emission is a serious drawback. This degradation was investigated by past works, which pointed out that the degradation was induced by high-density currents through OLED component under the long-time operation [1][2]. Proposed by a past work [3], different reverse biases was imposed on OLED components in display frames to alleviate the long-time degradation on OLEDs. Most recently, along with the reverse bias, new pixel circuits [4][5] for AMOLED displays are designed to alleviate OLED degradation, thus successfully extending OLED life time. However, since emission luminances in different frame times during AMOLED displaying differs significantly for displaying varied images, the OLED degradation evolves in a highly unpredictable fashion. In this study, based on valid theories, the voltage across the OLED is first used as indicator for OLED degradation. Then the relation between the level of OLED degradation, in terms of OLED’s cross voltage, and the history of imposing reverse biases are precisely modeled. With the model, the degradation of the OLED under reverse bias to extend lifetime can be successfully predicted. Based on this model, engineers can then optimize the applied reverse bias on OLEDs to maximize the OLED lifetime for varied display requirement.

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