Device for measuring the negative sequence voltage in a three phase system outlet


G01R19/28 - adapted for measuring in circuits having distributed constants

 

(57) Abstract:

The invention can be used in Metrology indicators of the quality of electric power in three-phase networks of industrial frequency. The inventive device for measuring the negative sequence voltage in a three phase system grid contains braked motor 1 with multiple measuring coil 2, the switch 3, the synchronizer-limiter 4, the integrator 5, the selective filter 6, an amplifier 7, a detector 8, the indicator 9 voltage corrector 10 technological errors. 1 Il.

The invention relates to Metrology performance power quality (SCE) in a three-phase industrial frequency of 50 Hz. The device measures voltage reverse power General purpose.

It is known device [1] , performed on three transformers with nine secondary windings, six rectifiers, three potentiometers. In transformers device formed six-phase voltage on the secondary (primary and secondary) windings, the coils are bound by strict interdependence. These stresses act on the six gates, the output of which occurs displaced the STS - acceptable accuracy (5-10% ). The disadvantage is the difficulty of manufacturing technology identical transformers. Closest to the invention is a device [2] , containing a synchronous electromachine, in a rotating rotor which (if any unbalance in the grid) there is a counter-rotating magnetic field EMF (twice the power frequency, 100 Hz) and amplitude proportional to the voltage of the reversed sequence. Dignity devices - high precision measurement. The disadvantage is the presence of rotating parts and, consequently, reducing the metric parameters in time.

The purpose of the invention is the measurement and operational control reverse sequence with high accuracy (1-2% ).

Goal is achieved by slow motor with multiple measuring windings of the rotor blocks amplitude-pulse coding and processing of the useful signal transistors and chips.

The device includes (see drawing), inhibited the motor-sensor 1 with the measuring windings 2, switch 3, the synchronizer-limiter 4, the integrator 5, the selective filter 6, an amplifier 7, a detector 8, the indicator 9, the corrector 10 tehnologicheskimi measurement, due to mechanical rotation, electronic switch performs a serial poll EMF windings, concealer (passive RC circuits) is used to align technological variations of the magnitude and phase of the respondents EMF windings, synchronizer stop forms of network voltage control signals switch and blocks of electronic circuits from overvoltages in the measured power. The stated differences from the prototype informs the device the new property.

The operation of the device in the dynamics. Voltage three-phase network is fed to the stator windings of the motor 1 and the synchronizer stop 4. When the asymmetry in the power grid, the intensity distribution of the magnetic field in the rotor windings in a plane perpendicular to the axis of the motor, resembles an ellipse. In sections of the rotor induced EMF is proportional to the magnetic flux, rotating with the frequency of the mains. Synchronizer-limiter 4 generates the synchronous frequency of 50 Hz signals control the operation of the switch 3. Corrector 10 compensates for the variation of EMF windings. Switch 3 generates a sequence of pulses for successive survey windings in accordance with the locations of each of the n) contains the envelope frequency of 100 Hz, proportional to the negative sequence voltage. This voltage is derived by the integrator 5, a filter 6, is amplified to the required level by the amplifier 7, passes the detector 8 and gets on indicator 9, which captures the desired voltage reverse order. The estimated error of the meter 1-2% .

These studies confirm the advantages of the proposed technical solution in comparison with the prototype. (56) USSR Author's certificate N 1272402, CL N 02 F 3/26, 1984.

Zielonko I. C. Indicators of power quality and control in industrial plants. M : Atomizdat, 1986, S. 47.

DEVICE FOR MEASURING the negative SEQUENCE VOLTAGE IN a three PHASE ELECTRICAL SYSTEM containing an electric motor, a filter and a voltage indicator, characterized in that, to improve measurement accuracy, put the switch corrector technological errors, synchronizer stop, integrator, amplifier, detector, and the rotor locked motor equipped with a multi-section measuring winding, the conclusions of which is connected through serially connected corrector technological errors, a switch, an integrator, a filter, such operation is controlled network, to which is also connected to the input of the synchronizer-limiter, the output of which is connected with the control input of the switch.

 

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