Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1991-04-03
1993-03-16
Ng, Jin F.
Communications: electrical
Condition responsive indicating system
Specific condition
340662, 364483, 324127, 324142, G08B 2100
Patent
active
051948508
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for metering electrical energy. It is also concerned with devices for carrying it out.
BACKGROUND OF THE INVENTION
There are already known electromechanical processes for metering electrical energy which are employed in the electricity meters of millions of subscribers to the public electricity service.
However, these electromechanical processes which have shown substantial proof of efficiency and reliability have the disadvantage that they require costly and bulky devices.
Furthermore, there are known processes for measuring electrical power which make use of techniques involving the separate measurement of the current and voltage, for example in a single-phase installation. In some of these known processes, the instantaneous voltage and current, after being measured and put into the appropriate shape, are multiplied by analog means.
The voltage taken directly from the installation or from the secondary winding of an isolating transformer is usually reduced so as to reach a signal level compatible with the input levels of an integrated multiplier circuit. The current can be measured either by means of a shunt, this being the most common technique, or by using a current transformer or employing a Hall-effect sensor.
In the first two cases, namely a shunt or a transformer, the main handicap is the bulk and weight of the installation. The use of a Hall-effect sensor adopting the known flux compensation technique solves any problem of galvanic isolation, especially difficult when a shunt is used, but is truly justified only in uses where an acquisition speed below a microsecond is necessary, because it has the disadvantage of employing devices which are complex and costly and which supply low-level output voltages.
Some of the processes for measuring power and energy employing the abovementioned measuring techniques make use, furthermore, of a digitization of the respective analog voltage and current signals, thus allowing a digital processing of the corresponding information. However, these processes, although of higher performance as regards the processing than the purely analog processes, nevertheless involve devices which are at least as costly and bulky because of the sensors, especially current sensors, used.
OBJECT OF THE INVENTION
The object of the present invention is to overcome these disadvantages by providing a process for metering electrical energy passing at a specific point of a single-phase network, comprising the simultaneous steps of periodic acquisition of respective current and voltage information at the said network point and a step of processing the said information in order to generate an information item on the measurement of electrical energy from the said current and voltage information.
SUMMARY OF THE INVENTION
According to the invention, each step of acquiring the current information comprises the following steps: structure surrounding one of the lines of the network of a current substantially proportional to the sum of a modulating current of a predetermined high frequency and of a so-called compensating current, the said predetermined high frequency, the detection of an overvoltage leading to an acquisition of the said compensating current as an image of the current circulating in the said line, the said compensating current being controlled in such a way that the current introduction step A/ leads systematically to an overvoltage detection.
Thus, with the process according to the invention, the metering of electrical energy, carried out by the use of a high-frequency current modulation, requires only a magnetic circuit of small size in relation to that which would be needed for a current acquisition at the mains frequency.
Furthermore, the use of a compensating technique combined with the abovementioned modulation makes it possible directly to obtain an image of the current circulating in the line.
In an advantageous embodiment of the invention, the step of acquiring the current information comprises, fu
REFERENCES:
patent: 4282576 (1981-08-01), Elms et al.
patent: 4351028 (1982-09-01), Peddie et al.
Berry Jean-Paul
Bourrieres Pierre
Hofsass Jeffery A.
Manufacture d'Appareillage Electrique de Cahors
Ng Jin F.
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