Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Phase comparison
Patent
1997-07-02
2000-10-10
Ballato, Josie
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Phase comparison
324 7677, 361 85, G01R 2500
Patent
active
061305316
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention generally relates to electric power systems and their automation, particularly to the phase angle measurement method and system in electric power systems.
BACKGROUND OF THE INVENTION
One of the most important indexes of power systems is safe, steady operation. Therefore, a lot of expensive computers and communication equipment have been invested to set up scheduling and controlling systems having functions such as remote signaling, remote telemetering, remote controlling, remote tuning and safety monitoring of electric power systems. However, since an electric power system covers vast in territory, phase angle measurements can not be attained in real-time and directly. Phase angles are computed from power flow analysis or state estimations which are based on telemetering or voltages, active powers and reactive powers. This measurement method is not only inaccurate but also time consuming, and impossible to be used in safety and steady analysis or emergency control in electric power systems. Monitoring of power system stability has to be based on the change of active and reactive power in networks and steady state of power system be judged indirectly.
With development of science and technology, especially of computers, communication and satellite technology, it turns vast into near in territory to make phase angle measurements possible. There are, more, microwave and optical fiber communication with high speed and great capacity, and the global position system (GPS) having accurate location with .+-.15 m and accurate time within .+-.1 .mu.s. These advanced communication means and technology provide pledge for this invention.
SUMMARY OF THE INVENTION
The main aim of the invention is to accurately measure phase angles of voltages, currents and electric potentials of generators in real-time with adding a few of equipment in current electric power communication systems. The measurement according the invention can reach 0.1.degree. in accuracy and several times per cycle of power frequency.
Therefore, an object of the invention is to provide a precious phase angle measurement method and system by using GPS to sign time mark on signals to be broadcasted so as to prevent the signal from communication delay.
A further object of the invention is to provide a real-time precious phase angle measurement system by using GPS, computer and automation technology.
A further object of the invention is to provide a real-time phase angle precious measurement method and system by using modern automation technology to set up predicting model in order to avoid of time consumation of communication systems.
Another object of the invention is to provide a real-time precious phase angle measurement method and system by compensating phase delay in communication systems.
The invention provides a phase angle measurement method and system in electric power systems. The method comprises steps of signal phase and the time, determining the reference signal phase (.phi..sub.0) at a series of given time, or determining the time (t.sub.0) at a series of given phase; signal to each substation by communication; and the time, determining the phase of the tested signal (.phi..sub.m) at the same given time as to the reference signal, or determining the time (t.sub.m) at the same given phase of the tested signal as to the reference signal and storing the measurement values .phi..sub.m or t.sub.m ; t.sub.0 received and t.sub.m stored, calculating the phase difference (called phase angle) between the tested signal and the reference signal.
Measuring step includes steps of filtering, shaping of sinusoidal signals and establishing standard time-base. In step of providing standard time-base, a standard second signal is provided by Global Position Systems (GPS), and frequency multiplication signal is produced so as to make resolving power of standard time-base signal into 1 .mu.s. In addition, the measuring step further includes steps of locking phase and frequency multiplication, and in the calculation step the
REFERENCES:
patent: 3027513 (1962-03-01), Mulavey
patent: 3597735 (1971-08-01), Nakayama
patent: 3986079 (1976-10-01), Hinman
patent: 4878208 (1989-10-01), Seki
Ballato Josie
Solis Jose M.
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