WO2006085771A1

WO2006085771A1 - Method and device for measuring voltage characteristics by a pc sound card

Info

Publication number: WO2006085771A1
Application number: PCT/NO2006/000034
Authority: WO
Inventors: John Olav GIÄVER TANDE; Kjell LJÖKELSÖY
Original assignee: Sintef Energiforskning As
Priority date: 2005-02-08
Filing date: 2006-01-26
Publication date: 2006-08-17
Also published as: NO20050671D0; NO322427B1

Abstract

Method for measuring, analysing and registration of parameters at an electrical energy network. A voltage or current from the actual power network is scaled with a known factor and supplied to an audio input of a computer with an audio card. The supplied signal is processed in the computer for storing and displaying on the computer's monitor. A straight forward effective device for performing the method includes a computer (11) with a microphone/audio input (12) whereas the microphone input is supplied with at least one analogue signal from an adapter (14) which is arranged to type network voltage, possibly current, where there exist means for scaling the typed signal to a level adapted the microphone input. The computer is arranged with software to tap end process the measured signals.

Description

METHOD AND DEVICE FOR MEASURING VOLTAGE CHARACTERISTICS

BY A PC SOUND CARD

The invention relates to a method as described in the preamble of claim 1, for measuring voltage quality. The invention also relates to a device to carry out the method.

Background

There is known different equipment for measuring voltage quality in a single-phase network. This equipment can have imbedded measurement and calculation routines, but requires a PC for the display of results. The known equipment can only register (calculate) a limited number of voltage quality parameters and has limited capacity for storing data.

There are also known more advanced and expensive measuring instruments which can measure voltage quality, current and effect in a three-phase network. These have satisfactory capacity, but at a cost that in many cases is too high. Available equipment generally has too high a cost for general usage.

Object

It is in different connections the need for measuring, analyzing and storing measure and analyse results for voltage quality in single-phase and three-phase network, possibly current, voltage and effect measurement in a single-phase network, where cost of existing equipment is not satisfactory. The main object of the invention is thus to provide a device which makes it possible to lower the costs related to measuring voltage quality. This especially relates to not only equipment costs, but also to costs related to storing of measured data. It is desirable to provide a device that can be manufactured with so low cost that it can be made available for a substantially larger user group than the "professional" measuring equipment of today.

It is a special object of the invention to provide a device for measuring voltage quality which is so straight forward to manufacture and use, that it can be utilized in a greater range than is the case for known equipment for voltage measuring. The device according to the invention can be used by professionals as well as persons without any special skills in the area, e.g. caretakers in schools and by private persons.

It is further an object to provide a device for measuring voltage quality, that in a straight forward way can be utilized to transfer the measured results, e.g. from home appliances of a network company. The invention

The invention is described in claim 1 and 2. By this method and device it is possible to provide a system for measuring voltage quality, where the equipment needed by a single user, can be made at relatively low cost. Since computers with audio input are readily accessible and already exist in work, education and private situations, a measuring method like this will provide considerable advantages.

At the same time the device will make it possible to perform a universal measurement with greater possibilities for analyzing and for storing the measured and analyzed results. Further, the device, used together with a battery-powered computer, will be capable of performing measurements on a network in unusual operating condition, e.g. during a power cut.

The invention also makes it possible to perform three-phase voltage measurements or single-phase current and voltage measurements at the same time.

For transforming measured value of network voltage to an audio input of a computer, several techniques can be used, even though for reasons of safety it is desirable to use electric isolation, i.e. use of a transformer. The same applies for measuring current.

The audio input is used as input for accommodating the measured signal, after which the audio card transforms the analogue signal to digital values.

The invention is different from known measuring equipment in that it uses the microphone input on a common computer for signal input, and the power of calculation and storing possibilities in the computer, whereas traditional instruments have embedded processor and storage.

From US 6 415 239 (Udovichenko 2002) it is known to provide a measuring adapter for transforming of a physical quantity, such as temperature, to a modulated voltage signal, so as to be able to utilize the audio input of a computer, especially a PC, as equipment for performing analyzing, displaying and storing of the measurement by means of the computer. The equipment known from the patent publication of Udovichenko is, however, not suitable for measuring voltage quality in a single-phase or three-phase network.

Further it is known from US patent application 2004/0220487 (Vyshedskly, 2004) to provide a measuring adapter for supply of several physiological data from measuring sensors to an audio input of a computer. This measuring adapter includes circuits which generate modulated signals in different frequency ranges, to provide several measurements values at the same time, but independent from each other. This equipment is suitable for either measuring voltage quality in a single-phase or three-phase network. Further details of the invention will be apparent from the following description of an example.

Example The invention is more specifically described below with reference to the drawings, in which

Figure 1 illustrates a measuring assembly with a PC and a device according to the invention,

Figure 2 shows a circuit diagram of an embodiment of the invention, with an adapter for use to measure voltage in a single-phase network,

Figure 3 shows a circuit diagram of a second embodiment of an adapter for measuring voltage in a single-phase network,

Figure 4 shows a circuit diagram of a third embodiment of an adapter for continuous calibration of the measurement, Figure 5 shows a circuit diagram of a fourth embodiment of an adapter for measuring voltage in a three-phase network,

Figure 6 shows a circuit diagram of a fifth embodiment of an adapter for measuring current and voltage in a single-phase network, and

Figure 7 shows examples of the processing of measured signals.

In Figure 1 there is shown a standard computer (PC) 11 with an input 12 designed for an analogue signal from a microphone. Such inputs are connected to an audio card 13, i.e. an AD-transformer, which is arranged for collecting analogue signals in a range of typically up to 100 mV peak-to-peak with an arbitrary frequency in the audible range. Connected to the input 12 is a transformer or an adapter 14 with plug 15 for connecting to a network connection 16. The adapter 14 in Figure 1 is shown as an encapsulated unit, where the components are arranged in a box, embedded or encapsulated in another way. The adapter 14 can also be embedded with the plug 15 or integrated in the main part of the plug, so that it appears as a unitary part of the plug. In addition to the device 14, the invention requires access to software which can be programmed into the computer 11, to process the measured signal, perform analysis, display and storage. This program can be obtained from an appropriate carrier or be downloaded from an external computer over the Internet. The object of the program will be more closely specifically below. In Figure 2 there is shown an embodiment of an adapter for use in performing the invention. From the plug 15, the sampled voltage is supplied to the primary winding of a voltage transformer 17. At the secondary side is arranged a voltage divider with two resistors Rl and R2, which are adapted to the sensitivity of the input 12 (Figure 1). For connection to a computer, the output cable is provided with a suitable plug 18. The housing of the adapter is indicated by a line 19.

This solution provides electric isolation between the high voltage and low voltage circuit part, and thus increases the safety.

In Figure 3 there is shown an adapter based on voltage dividers, one for each measuring cable. For each measuring cable there is a voltage divider Rl and R2, respectively R3, R4, where the tapped voltage is connected to each of the stereo inputs. The network voltage is in this case calculated as the difference between these two signals.

In Figure 4 there is shown a third embodiment for an adapter for use in performing the invention, which is based on the embodiment of Figure 2, with a voltage transformer 20 and a voltage divider Rl, R2, but extended with a reference signal for calibration of the measurement. The reference signal is established by the circuit around the voltage reference diode Dl. A diode D2 and a resistor R3 ensure that the voltage reference diode Dl leads current in a positive half cycle. In the negative half cycle, the resistors R4 and R5 provides zero voltage over the voltage reference diode Dl . The result is a voltage with a flat top and bottom, with well-defined and fixed amplitude. The level of the output reference voltage is controlled by the voltage divider, which is formed by the two resistors R4, R5. The reference voltage can be read out continuously on each own channel, or the reference voltage can be read out at the same time on both channels by activation of the switch 21.

In Figure 5 there is shown an adapter for measuring voltage in a three-phase network. The design corresponds to two transformers as shown in Figure 2, V-connected between the phases in a three-phase network connection 22, and with the secondary side connected to each own channel with a common signal earth on a microphone plug 18.

In Figure 6 there is shown an adapter for measuring voltage and current which is supplied to an electric outlet 23 from a plug 24. The voltage divider 25 corresponds to the embodiment in Figure 2, while the current measurement is tapped over a current transformer 26 in one of the leads and with an output part on the current transformer which taps the measuring signal over a shunt resistor Rsh.

In Figure 7 there is shown an example of an interface of a PC for use in the invention. There is shown a measurement of the voltage curve shape A, content of harmonic voltage components B, time tracks of the effective value of the voltage C, and time tracks of the voltage frequency D.

The invention provides a special advantage when using a computer having its own battery power supply. The device can then be arranged for registering voltage parameters during a power supply failure.

In the case where the computer is connected to communication equipment for the transfer of messages over a communication network, it can, according to the invention, be arranged to transfer a deviation message, when deviation is proved from stated norms for predetermined voltage parameters. This can be used in different ways to transfer an alert or deviation message from an unmanned measuring point.

Claims

1. Method for measuring, analysing and registration of parameters at an electrical energy network, characterized in that a voltage or current from this particular power network is scaled with a known factor and supplied to the audio input of a computer with an audio card, and that the supplied signal is processed in the computer for storing and displaying on the computer's monitor.

2. Method according to claim 1, characterized in that a reference signal with amplitude of the same order of size as the measured signal is provided, either continuous on a vacant channel, alternatively on the same channel as the measured signal is supplied, as a part of a calibration procedure, where by inherent limitations in absolute precision in the computer's audio input can be circumvented.

3. Device for performing the method according to claim 1 or 2, for measuring, analysing and registration of parameters of an electrical energy network, characterized in that it includes a computer (11) with a microphone/audio input (12) and where the microphone input is provided with at least one analogue signal from an adapter which is arranged to tap network voltage, possibly current, where there exist means for scaling the tapped signal to a level adapted the microphone input, and that the computer is arranged with software to tap and process the measured signals.

4. Device according to claim 3, characterized in that the adapter includes a voltage transformer (17), which on its secondary side possibly has a voltage divider (Rl, R2).

5. Device according to claim 3, characterized in that the adapter includes a voltage divider (Rl, R2; R3, R4) for each of the phase leads in a single-phase network, and where two down-scaled signals each supplied to a channel in a stereo microphone input, and the software of the computer is arranged to calculate the line voltage as a difference of the two signals.

6. Device according to claim 3, characterized in that the adapter includes two section circuits for scaling down the line voltages in a three-phase network, each of which is supplied to a channel in a stereo microphone input, and the software of the computer is arranged to calculate the third line voltage.

7. Device according to claim 3, characterized in that the adapter (Figure 6) has a section circuit for scaling down the voltage and a section circuit with a current transformer (26) and a shunt resistor (Rsh), for measuring, at the same time, current and voltage on a generating or consumer object.

8. Device according to any one of claims 3 - 7, characterized in that the adapter includes a transmitter (Figure 4) to provide a calibrated reference voltage, either continuously or activated by a user.

9. Device according to any one of claims 3 - 8, characterized in that it is arranged to operate during failure in the power supply, by the computer having its own battery power supply.

10. Device according to any one of claims 3 - 9, characterized in that the computer is arranged to transfer a deviation message when a deviation is proved from stated norms for predetermined voltage parameters, which computer is connected to communication equipment for transferring messages over a communication network.