| US 7,579,712 B2 | ||
| Power system protection system | ||
| Ken Yanagihashi, Tokyo (Japan); Mamoru Suzuki, Tokyo (Japan); Takafumi Maeda, Tokyo (Japan); Akira Ishibashi, Tokyo (Japan); and Yasuchika Nishitani, Tokyo (Japan) | ||
| Assigned to The Tokyo Electric Power Company, Tokyo (Japan); and Kabushiki Kaisha Toshiba, Tokyo (Japan) | ||
| Appl. No. 10/592,548 PCT Filed Mar. 16, 2004, PCT No. PCT/JP2004/003474 § 371(c)(1), (2), (4) Date Sep. 11, 2006, PCT Pub. No. WO2005/088801, PCT Pub. Date Sep. 22, 2005. |
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| Prior Publication US 2007/0198985 A1, Aug. 23, 2007 | ||
| Int. Cl. H02J 3/14 (2006.01) | ||
| U.S. Cl. 307—38 | 40 Claims |
| 1. A power system protection system for stably operating a power system, comprising:
a main device for acquiring a system electric quantity of one or a plurality of upper substations of said power system; and
a terminal device for acquiring a system electric quantity of one or a plurality of lower substations that receives power
from said upper substation and supplies power to loads, wherein:
said main device includes:
a system voltage gradual drop determination unit that outputs a system voltage gradual drop determination signal when the
voltage drop rate in a long time region exceeds a predetermined value based on a three-phase voltage of the power system and
terminates the outputting of said system voltage gradual drop determination signal when the three-phase voltage of the power
system exceeds a voltage recovery set value;
a system voltage sudden drop determination unit that outputs a system voltage sudden drop determination signal when the voltage
drop rate in a short time region exceeds a predetermined value based on a three-phase voltage of the power system and terminates
the outputting of said system voltage sudden drop determination signal when the three-phase voltage of the power system exceeds
the voltage recovery set value;
an operation-prioritized selection unit that outputs an operation-prioritized selection signal early when the voltage drop
in the three-phase voltage of the power system is large and outputs the operation-prioritized selection signal late when the
voltage drop is small; and
an output permission unit that outputs an output permission signal in the event of the voltage sudden drop resulting from
a reactive power characteristic, and wherein
said terminal device includes:
a load shedding output unit that sequentially sheds loads starting from those of the lower substations suffering more from
the influence of the voltage drop resulting from the reactive power characteristic when receiving the system voltage gradual
drop determination signal and the operation-prioritized selection signal from said main device; and
a load shedding selection output unit that selects loads causing the voltage sudden drop resulting from the reactive power
characteristic and sequentially sheds the selected loads when receiving said system voltage sudden drop determination signal
and said output permission signal from said main device.
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