DD152425A1 - DEVICE FOR MEASURING ELECTRICITY AND VOLTAGE OVEN HEATING IN ELECTRIC POWER SUPPLY NETWORKS - Google Patents

Abstract

The aim of the invention is to provide a Oberschwingungsmessgeraet to come to secure statements about the occurrence of higher harmonic in electrical energy supply networks for the purpose of researching such phenomena and their elimination. The device works after the pass u. Parallel analyzer principle (Figure 1). It has a certain number of inputs through which either voltage and / or current directly from the mains and / or smaller voltages for the electronic harmonic analysis are processed. By means of active filters of high quality, the individual harmonics are filtered out and provided as AC voltage and / or DC voltage signals for the measurement and the registration. Each of the developed filters is tunable and by means of the measuring part of the device exactly to the desired frequency adjustable. The device has a high dynamic range and is due to its circuit highly flexible and universally applicable.

Description

Device for measuring current and voltage harmonics in electric power supply networks

The invention relates to a device for measuring current and voltage harmonics in networks of the public electric power supply and in networks of industry, It serves to capture all the harmonic components of distorted current and voltage waveforms as they occur in electrical energy systems increasingly. With the aid of this invention it is possible to obtain with high accuracy reliable statements about the intensity of such network perturbations caused by certain customers in network hubs of interest.

Characteristic of the known technical solutions

It is known that one can perform the harmonic analysis of a non-sinusoidal periodic electrical quantity in the frequency and time domain. Purely the different fields of application in vibration measurement technology, there are corresponding devices, as described in the DE-Offenlegungsschriften 2143202, 2219085 and 2738707. The arrangement according to DE-OS 2143202 is suitable for measuring and monitoring current harmonics of specific atomic numbers »It is not possible to measure voltage harmonics and / or in several conductors simultaneously.

In the GDR, there is the Oberschvingungsmeßgerät built by Hertel and Koetnitz, which has been specially developed for studies in electrical energy supply systems. »

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However, the device has the disadvantages that it can not be used at arbitrary voltage levels, does not work independently of the mains supply, is not suitable for long-term measurement, generates large measurement errors and can not measure several harmonics at the same time the acoustic measuring technique and the vibration measuring technique, which are modifiable for the measurement in electric power supply systems, but in addition to specially created additional devices still v / eeere disadvantages have that make them suitable only for special measurement tasks,

Although the analyzer SM 32 ζ * B ₄₁ has a high-quality filter, it can only perform a continuous analysis of the frequency spectrum after adaptation and / or measure only one harmonic current in a conductor.

The EP-spectrometer FSP-80 may, however, immediately display the frequency-amplitude diagram of a non-sinusoidal size _s should here all vorhandenen'Filter be tuned to the frequencies, such as may occur at the harmonic analysis of the Hetzfrequenz after appropriate adjustment. The measuring dynamics of this device are very low «

The aim of the invention is to provide a highly flexible measuring device that allows reliable statements about the occurrence of higher harmonics in representative Hetzknotenpunkten. With this harmonic measuring device, it is possible to simultaneously measure several voltage and current harmonics at arbitrary voltage levels. This device is suitable for long-term measurement and can be operated both via the supply network as well as off-grid with batteries.

It is also possible, with this device, which has a high dynamic and the measurement error is very small, to measure in several conductors simultaneously »This device is therefore a harmonic measuring device, the much improved Eigen-

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business with existing equipment.

Explanation of the essence of the invention

The invention has for its object to provide a measuring device for determining occurring current and voltage harmonics of the fundamental frequency in networks of public energy supply 'and networks of industry.

The object is achieved in that a device in which the Parallelanalysator- and Durehlaufanalysatorprinzip are coupled together, is constructed. The adaptation to the electrical power supply network for the current measurement is carried out via a device-internal standard converter, which is looped into the burden circuit of the corresponding current transformer at the respective network node. The adaptation to the electrical power supply network for the voltage measurement via a device-internal voltage converter, 'whose transmission error for the proposed measurement tasks is negligible. Thus, the measurement can be made directly in the low voltage level. In the middle and high voltage levels, the measurement is performed behind the voltage transformers of the network.

Pur special measurement tasks that arise when using other methods for recording the current and / or voltage curve than that with the help of transducers, such. For example, when measuring via shunts, the device has additional inputs that allow smaller voltages to be analyzed.

From the input part 2 signal levels are provided to the device, of which one signal level ten times, greater than the ground level, The larger level is to increase the distance of the signal voltage to noise, so that the measurement is very. small harmonic amplitudes becomes possible «

The two signal voltages are fed to filters that sift out the individual harmonics. The quality of the filters does not require a 50 Hz lock · Each filter is tunable and can be set to any harmonic

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become.

Each filter rectifies the emitted Cb oscillation, thus providing, in addition to the alternating voltage signal of the respective harmonics, a DC voltage signal equivalent to the RMS value of the rectified AC voltage, for example using oscillographs with the aid of DC and / or V Measured and registered with the help of writers.

From management example

The invention will be explained in more detail in the following embodiment *

Pig. 1: block diagram

- Harmonic measuring device -

Pig * 2: Circuit of the device-internal voltage transformer

Pig «, 3: Representation of the signal conditioning according to the device's own current transformer

Pig «, 1 shows the block diagram of the harmonic measuring device in an embodiment in which the versatility of the device is best expressed«

At the 3 U - ^, 3 Ip and U ₇ -p terminals the mains input voltages, input currents and the additional voltages can be connected. The network-side input variables are converted to electronically processable signals by means of corresponding transducers (Pig * 2) and with the aid of the linear amplifiers Z in the input ICL-g. The signals of these 12 inputs pass via signal channels, 12 each for the basic voltage levels U and

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.12 for 10 U to the pi fi ers F ₄ Each of the 12 illustrated filters P 1 to P 12 can be switched separately to any input channel «,

Each filter is tunable. This makes it possible to measure .12 / n harmonics from the signals of η inputs, eg to examine the signal from one input to 12 different harmonics or the voltages of three inputs to 4 harmonics and so on. In order to allow both easy tuning of the filters and measurement of relatively high frequencies, each filter has different grades. ·.

The harmonics which are filtered out by the filters are at one time in the form of a direct current measurement signal U as well as a dc voltage measurement signal at the output terminals of the corresponding filter. In addition, the measurement signals are divided into 12 channels for the alternating voltage measurement signals U and 12 for the dc voltage measuring signals.

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signals U passed to provide them at the output part of the external measurement and registration.

The measuring part MT with built-in measuring unit, which can be connected to all channels, serves to match the filters more precisely to the corresponding harmonics and to check the input voltage levels of the individual inputs.

In order to achieve a high dynamic range, the filter circuits have a correspondingly high gain. In the case of the high gain, the measuring signal, that is to say the output voltage at the filters, must not exceed a certain level in order to always be able to guarantee a small measuring error. For this reason, there is a circuit in each filter, which signals via an indicator light AL, whether in the corresponding filter, the required output level is exceeded or not.

It provides the necessary voltages for the filters F, the amplifiers V, the auxiliary inputs Z and for the indicator lamps AL. As far as the capacity of the secondary part permits, this can be done in Fig. 1 shown device can be expanded by as many filters. It is also possible, instead of the inputs Ur ₇ -T, further inputs U -.- ^ and / or Io or

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conversely, instead of U ™ and / or lo, to connect further U ₇ -r, inputs to the device, the input assignment is changeable in all conceivable variations

FIG. 2 shows the voltage converter, which down-converts the input voltages U, to the device-internal signal level U, which also simultaneously generates the level 10 U. The Spedition v / and ler was built for this special purpose »

Its linear transmission behavior was achieved for the proposed measuring tasks _f that appropriate nuclear material and a specific core shape were selected with the aid of theoretical investigations.

The industrially manufactured current transformer shown in Pig _o 3 has linear transmission behavior for the resulting measurement tasks when it is loaded with henn burden Ζ, τ. The voltage signal across the nominal burden Z, j is raised in the amplifier V to the two signal levels U and 10 U. The amplifier V used here has linear transmission characteristics β

Claims (8)

- ί - Inventions claims 1 »Device for measuring current and voltage harmonics in electric power supply networks with tunable active filters, which have such a high quality that no 50 Hz lock is required, the quality of a fourth, which allows a comfortable tuning of the filter on a value is switchable, with which one can also squeeze out even harmonics relatively high frequency, which have a very high Meßdy-namics, characterized in that both the continuous as well as the Parallelanalysatorprinzip are coupled together to measure different harmonics of any atomic number in parallel can be that it is possible in all voltage levels currents and / or voltages in a conductor and in several. to examine simultaneously on its harmonic content, by i, and to register the exit of the measurement range is displayed with a guaranteed accuracy an electronic harmonic analysis is performed · 2 _# Device according to item 1, characterized in that a specially developed voltage transformer with linear transmission properties, which reduces the mains voltage to the required device input level, and thus implements a galvanic isolation between the network and the device, is used. 3 · Device according to point 1, characterized in that the voltage drop arising across the rated burden of an existing normal current transformer represents a signal equivalent to the current profile in the network, which is raised to the required device input level by a special amplifier which is absolutely linear in terms of the transmission behavior. 4. Device according to item 1, characterized in that an additional input is provided, can be brought to the required device input level with the extra-low voltages. C i) V "AP, CH" O '. - O 5 "device according to items 1 to 4, characterized in that the three different types of input are multiple, and that they are interchangeable with each other depending on Meßauf« 6 * device according to items 1 to 5 _5, characterized in that in the input part of each of the three types of input supplies in addition to the required input voltage level of the device still ten times the value of this level, 7 * Device according to item 1 to 6, characterized in that the measured variables are both as AC voltage and DC voltage signal for measurement and registration available » 8 ', device according to item 1 to 7 _S characterized in that all ia existing PiIter measure in parallel. S * Device according to points 1 to 8, characterized in that any one of the m PiIter can be connected to the existing η inputs, that therefore used at η inputs $ e m / n different harmonics can be measured and registered * ... Λ /. OvHV