Three-phase electric energy metering head
Technical field
The present invention relates to the measuring apparatus field, especially relate to a kind of three-phase electric energy metering head that is used to measure electric energy.
Background technology
Compare with traditional stem-winder, adopt the three-phase multifunctional table of electronics measuring principle, have advantages such as high precision, measuring multiple parameters, harmonic power electric energy metrical.From overall assessment, the three-phase multifunctional table still is a steady state power load measuring products, because its application enlarges, electric system constantly proposes new technical requirement to ammeter.Existing three-phase multifunctional table performance and quality can not adapt to the demand of electric system fully.
Present three-phase electric energy metering head generally all is through after the transformer, just measures at low pressure end.And in fact in the process of transformation and electric power transfer, having very big energy loss, this part energy often can't be measured, and causes the metering of electric system inaccurate.In order to improve measuring accuracy, people have carried out long-term exploration, have proposed diversified embodiment.For example, Chinese patent literature discloses a kind of three-phase electric energy meter (application number: CN02263996.9), by three shunts respectively as three single-phase current sampled parts, also comprise three single-phase voltage sampled parts, three single-phase electric energy computation chips, six optocouplers simultaneously, gather the resitstance voltage divider and the amplifier of each phase voltage phase place and amplitude, and EPLD, CPU, storer, display, communication interface, button are formed.The current phase signal output interface of the shunt of each phase links to each other with CPU by the photoelectricity isolated part.The voltage signal output interface of the current signal output interface of the shunt of each phase and the voltage sampling parts of each phase links to each other with electric energy computation chip.The electric power signal output interface of electric energy computation chip links to each other with CPU by photoelectricity isolated part (optocoupler), the voltage phase signal of resitstance voltage divider and amplifier, the output interface of amplitude signal link to each other CPU connected storage, display, communication interface, button with EPLD, CPU.
Such scheme adopts three fully independently data acquisition modules, though improved the precision of metering to a certain extent, its metering remains at low pressure end to be carried out, and does not fundamentally eliminate the error in dipping that produces in the transformation process; And whole apparatus structure is comparatively complicated, and cost of manufacture is higher.
Summary of the invention
The objective of the invention is at the problems referred to above, provide a kind of reasonable in design, simple in structure, can measure electric weight, effectively reduce the three-phase electric energy metering head of error in metering process at high-pressure side; It is comparatively complicated to have solved the existing in prior technology structure, measures the technical matters that the electric energy loss in transformation and the transmission course can't be measured etc. at low pressure end.
Another object of the present invention is at the problems referred to above, provides a kind of signal processing reasonable, effectively improves measuring accuracy, and the lower three-phase electric energy metering head of cost of manufacture; It is lower to have solved the existing in prior technology measuring accuracy, the technical matters that cost is high.
For achieving the above object, the present invention has adopted following technical proposal: this three-phase electric energy metering head, be connected between three phase line and the electric energy counting assembly, comprise three symmetrical signal processing channels, it is the A phase, the B phase, C phase signals treatment channel, it is characterized in that, each signal processing channel has a signal gathering unit, each signal gathering unit comprises voltage sample unit and the current sampling unit that directly links to each other with the three phase line primary power source, and being connected between the two combination transformer, described combination transformer is made up of the voltage transformer (VT) summation current transformer; The voltage sample unit of described signal gathering unit links through amplifier, AD conversion unit and Hi-pass filter and digital multiplier successively, and the current sampling unit of signal gathering unit links through amplifier, AD conversion unit, Hi-pass filter and digital integration unit and digital multiplier successively; The digital multiplier of above-mentioned three signal processing channels links by low-pass filter and a sum unit respectively, and described sum unit links through numerical frequency converter and photoelectricity isolated location; The signal gathering unit of three signal processing channels links by an integrated circuit board and photoelectricity isolated location; Circuit board is arranged in the circuit board apertures of pedestal, is provided with three pour mass on pedestal; Three pour mass respectively be cast in pedestal in three combination transformers corresponding.
In above-mentioned three-phase electric energy metering head, described sum unit is switched between algebraically summation and absolute value summing mode by summation form switch unit.
The present invention creatively is connected signal gathering unit the end (primary power source) that transmission line of electricity does not pass through transformer, can measure the electric energy of conveying more exactly, is convenient to the management of electric system.The high voltage of input and big electric current are become low-voltage and little current signal, the voltage and current signal was multiplied each other according to the time, obtain the information that power changed along with the time, the frequency that output is directly proportional with power.This frequency can be directly and electric energy counting motor coupling.
In above-mentioned three-phase electric energy metering head, once being cast in the pedestal of described voltage transformer (VT) with the secondary current coil of secondary voltage coil and current transformer, the voltage transformer (VT) high-voltage connection links to each other with current transformer primary current coil in being arranged on pour mass, and the extension line of primary current coil extends to outside the pour mass.
For the ease of wiring, in above-mentioned three-phase electric energy metering head, also be provided with fairlead on the described pedestal.
In above-mentioned three-phase electric energy metering head, described pour mass and pedestal are made as one, and are provided with some umbrella skirt bodies on pour mass and pedestal.
Compared with prior art, the advantage of three-phase electric energy metering head is:
1. signal gathering unit directly is connected on the primary power source, avoids occurring because transformer work causes the part electric energy loss to measure.
2. mutual inductor and electric energy meter metering circuit lump together, verification the gauging table whole electric energy metrical gauge outfit that has been verification, the error of mutual inductor is irrelevant to the error of whole table, thereby has improved the precision of system.
3. simple in structure, reasonable circuit layout, the volume of whole device is little, and cost of manufacture is cheap.
Description of drawings
Fig. 1 is the circuit structure block diagram of three-phase electric energy metering head provided by the invention.
Fig. 2 is the cut-open view of three-phase electric energy metering head provided by the invention.
Fig. 3 is the partial sectional view of overlooking of three-phase electric energy metering head provided by the invention.
Fig. 4 is the upward view of three-phase electric energy metering head provided by the invention.
Fig. 5 is the side sectional view of three-phase electric energy metering head provided by the invention.
Among the figure, signal gathering unit 1, voltage sample unit 11, current sampling unit 12, combination transformer 13, amplifier 2, summation form switch unit 20, circuit board 21, pour mass 22, pedestal 23, circuit board apertures 24, primary current coil 26, once with secondary voltage coil 27, voltage transformer (VT) high-voltage connection 28, extension line 29, AD conversion unit 3, secondary current coil 30, umbrella skirt body 32, Hi-pass filter 4, digital integration unit 5, digital multiplier 6, low-pass filter 7, sum unit 8, numerical frequency converter 9, photoelectricity isolated location 10.
Embodiment
As shown in Figure 1, this three-phase electric energy metering head is connected between three phase line and the electric energy counting assembly, comprises three symmetrical signal processing channels, i.e. A phase, B phase, C phase signals treatment channel; Three electronic current mutual inductors and three three pairs of combination transformers 13 that electronic type voltage transformer is formed, and a sum unit 8 etc.Each signal processing channel has a signal gathering unit 1, and signal gathering unit 1 comprises voltage sample unit 11 and the current sampling unit 12 that directly links to each other with the three phase line primary power source, and is connected in combination transformer 13 between the two.
The voltage sample unit 11 of signal gathering unit 1 links with digital multiplier 6 through amplifier 2, AD conversion unit 3 and Hi-pass filter 4 successively.The current sampling unit 12 of signal gathering unit 1 links with digital multiplier 6 through amplifier 2, AD conversion unit 3, Hi-pass filter 4 and digital integration unit 5 successively.The digital multiplier 6 of above-mentioned three signal processing channels links by low-pass filter 7 and a sum unit 8 respectively, and described sum unit 8 links through numerical frequency converter 9 and photoelectricity isolated location 10.The signal gathering unit 1 of above-mentioned three signal processing channels links by an integrated circuit board 21 and photoelectricity isolated location 10.Sum unit 8 is switched between algebraically summation and absolute value summing mode by summation form switch unit 20.Consider the Electro Magnetic Compatibility of total system, delivery outlet has adopted photoelectricity isolated location 10.
The three-phase active energy here can algebraic addition, also can the absolute value addition.The selection of phase add mode is finished by the pin that summation form switch unit 20 is set, and the high level of this pin and low level correspond respectively to algebraic addition pattern and absolute value addition pattern (be known technology, this paper does not give unnecessary details).When selecting the pattern of absolute value addition, in calculating total active energy, the active energy of every phase all just is considered to.This pattern is particularly useful under the three-phase and four-line connected mode, because in the case, the symbol of active power is always constant.As ammeter connection error, as a direction wrong of going up current transformer mutually, it is normal 1/3rd that then total meritorious energy will become, because two-phase has wherein been cancelled each other.Certainly, in this case, anti-phase detection output can be indicated the mistake of wiring.
During work, three input channels of three-phase electric energy metering head directly connect primary power source, after the current and voltage signals of three-phase passes through sampling amplification and analog to digital conversion, in order to remove the direct current offset of sampled signal, circuit is through Hi-pass filter 4, because current signal is the differential relationship by air core coil character, circuit must add integration, obtains the instantaneous power signal of each phase by digital multiplier 6.Allow the instantaneous power signal by the low-pass filter 6 that cutoff frequency is very low, average signal is taken out.Then every phase power is done algebraic addition or absolute value addition, thus obtain three phase power and.
As shown in Figure 1, remove signal gathering unit 1 and photoelectricity isolated location 10, all the other all are integrated on the circuit board 21.
As Fig. 2 and Fig. 3 and shown in Figure 4, above-mentioned circuit board 21 is arranged in the circuit board apertures 24 of a pedestal 23 with three pour mass 22.Three pour mass 22 respectively be cast in pedestal 23 in three combination transformers 13 corresponding; Once being cast in the pedestal 23 of voltage transformer (VT) with the secondary current coil 30 of secondary voltage coil 27 and current transformer.Voltage transformer (VT) high-voltage connection 28 links to each other with current transformer primary current coil 26 in being arranged on pour mass 22.The extension line 29 of primary current coil 26 extends to outside the pour mass 22.Pour mass 22 is made as one with pedestal 23, and is provided with a plurality of umbrella skirt bodies 32 on pour mass 22 and pedestal 23.Insulating material such as pedestal 23 here and pour mass 22 employing epoxy resin are made.
Specific embodiment described herein only is that the present invention's spirit is illustrated.The technician of the technical field of the invention can make various modifications or replenishes or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.
Although this paper has used signal gathering unit 1 morely, voltage sample unit 11, current sampling unit 12, combination transformer 13, amplifier 2, summation form switch unit 20, circuit board 21, pour mass 22, pedestal 23, circuit board apertures 24, primary current coil 26, once with secondary voltage coil 27, voltage transformer (VT) high-voltage connection 28, extension line 29, AD conversion unit 3, secondary current coil 30, umbrella skirt body 32, Hi-pass filter 4, digital integration unit 5, digital multiplier 6, low-pass filter 7, sum unit 8, numerical frequency converter 9, photoelectricity isolated location 10 terms such as grade, but do not get rid of the possibility of using other term.Using these terms only is in order to describe and explain essence of the present invention more easily; They are construed to any additional restriction all is contrary with spirit of the present invention.