Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1999-10-07
2001-05-22
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S060000, C702S062000, C324S076110, C324S126000, C700S286000
Reexamination Certificate
active
06236949
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to systems and components for the protection, control, and/or energy management of electricity distribution systems for electric utility, industrial, manufacturing, commercial, and/or institutional use.
Monitoring of electric parameters, such as current, voltage, energy, power, etc., particularly the measuring and calculating of electric parameters, provides valuable information for power utilities and their customers. Monitoring of electric power is important to ensure that the electric power is effectively and efficiently generated, distributed and utilized. Knowledge about power parameters such as volts, amps, watts, phase relationship between waveforms, KWH, KVAR, KVARH, KVA, KVAH, power factor, frequency, etc. is of foremost concern for utilities and industrial power users. In addition, monitoring of electricity can be used for control and protection purposes.
Typically, electricity from a utility is fed from a primary substation over a distribution cable to several local substations. At the substations, the supply is transformed by distribution transformers from a relatively high voltage on the distributor cable to a lower voltage at which it is supplied to the end consumer. From the substations, the power is provided to industrial users over a distributed power network that supplies power to various loads. Such loads may include, for example, various power machines.
In such arrangements, utilities need to measure power coming out of or into the generating station or going into a power station. It is important to minimize the phase relationship between the current and voltage waveforms of the power being transmitted to minimize losses. It is also important to minimize the amount of harmonics that are present in the voltage and current waveforms. Also, the ability to detect the presence and magnitude of faults in the power system is important. Thus, accurate measurement of these waveforms is important.
In industrial applications, it is important to continuously monitor the voltage, current, phase, harmonics, faults and three phase balance of the power into the machine. These parameters may vary with the machine load. With knowledge of these parameters, the industrial user can better adjust and manage the loads to control machines, determine alarm conditions and/or more efficiently use the power.
Monitoring of electric parameters involves several components. For example, voltage transformers and current transformers are coupled to various electric transmission lines to measure the voltage and current in the line. Some conventional current and voltage transformers are relatively accurate and therefore suitable for power monitoring and measurement. However, such transformers may lack dynamic range, thereby rendering them less suitable for protection purposes that require a broad dynamic range. Other known conventional current and voltage transformers have a wide dynamic range making them suitable for protection purposes. However, these types of voltage and current transformers lack the accuracy needed for power monitoring and measurement. Thus, some facilities have installed both kinds of voltage and current transformers—one kind for accuracy for power measurement and monitoring and another kind for protection purposes. Accordingly, it would be advantageous if a current and/or voltage measuring device were available that could provide both high accuracy and wide dynamic range.
Another consideration related to present voltage and current transformers relates to worker safety. Conventional current transformers are high energy devices. If a worker accidentally open circuits the output of a present current transformer when the primary is energized, a very high voltage can develop. This high voltage represents a potentially hazardous condition that can cause grave or fatal injuries to a worker who might accidentally come into contact with the open circuit. Utilities and electric contractors have developed elaborate and expensive safety procedures to prevent this problem. However, despite these procedures, serious accidents still occasionally occur. Thus, it would be advantageous if a current and/or voltage monitoring device were available that could reduce the risk of this potential safety problem.
Accordingly, it is an objective of the present invention to provide a component and/or system that have improved capability to measure electric parameters. It is a further objective to provide an improved sensor component and system that have greater safety by reducing risk of accidental exposure to high voltage.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objectives, there is provided an improved voltage and/or sensor apparatus for monitoring voltage and/or current in an electric circuit in a system that distributes electricity. A sensor apparatus is associated with each phase conductor in the circuit. The sensor apparatus senses the electricity in the phase conductor and provides a digital output that is representative of the sensed electricity in the phase conductor.
According to a further aspect, there is provided a sensor apparatus that monitors voltage and/or current in a phase conductor of an electric circuit and that provides a digital output that includes data representing the phasor of the electricity in the sensed phase conductor.
According to another aspect, there is provided a monitoring system for monitoring voltages and currents in a distribution system wherein electricity is distributed in a plurality of circuits. The monitoring system includes a plurality of sensor apparatuses that monitor electricity in the electric circuits and that provide digital data outputs representative thereof. The plurality of sensor apparatuses are coupled to a digital data network that provides for the exchange of sensed data among nodes on the digital data network. On a node of the network, data from some of the plurality of sensor apparatuses are summed or otherwise processed to obtain data representative of a plurality of the electric circuits or a plurality of phases of one circuit.
REFERENCES:
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patent: 4709339 (1987-11-01), Fernandes
“Phasors Revisited”, Elmore, Presented to Western Protective Relay Conference, Oct. 23-25, 1990, Spokane, Washington.
“Power System Applications for Phasor Measurement Units”, Burnett, et al.,IEEE Computer Applications in Power, Jan., Jan., 1994.
Macrodyne Inc. Model 1690 Phasor Measurement Unit, Product Description, Jan. 24, 1995.
“Metering for Transmission Access”, Logini Digital KWH Inc., Pittsburgh, PA, 1996.
Adaptive Out-Of-Step Relaying Using Phasor Measurement Techniques, Centeno, et al.,IEEE Computer Applications In Power, Oct. 1993.
Brinks Hofer Gilson & Lione
Hoff Marc S.
Power Measurement Ltd.
Vo Hien
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