511results about "Effective value measurements" patented technology

The invention discloses a method for vibration online monitoring and fault diagnosis of a power transformer. The surface vibration of an oil tank of a transformer, the voltage, the current and the oil temperature of the transformer, and the switching values reflecting the on-states of a vibration source fan and the oil tank of the transformer are taken as basic monitoring parameters to be monitored; after signal conditioning is performed on the monitoring parameters, continuous synchronous waveform data sampling, processing and saving are performed; then the processed waveform data are continuously displayed in real time; signal decomposition, multi-parameter correlation analysis and characteristic vector magnitude extraction are performed on the waveform data; and then various characteristic vector thresholds of a specific transformer are compared to analyze and diagnose the operating state and the fault of the transformer. With the method, the operating state of the power transformer can be monitored in real time, and early warning as well as the analysis and the diagnosis of the fault condition of the transformer are provided, thus guaranteeing the secure and stable operation of the transformer.

An RMS-to-DC converter implements the difference-of-squares function by utilizing two identical squaring cells operating in opposition to generate two signals. An error amplifier nulls the difference between the signals. When used in a measurement mode, one of the squaring cells receives the signal to be measured, and the output of the error amplifier, which provides a measure of the RMS value of the input signal, is connected to the input of the second squaring cell, thereby closing the feedback loop around the second squaring cell. When used in a control mode, a set-point signal is applied to the second squaring cell, and the output of the error amplifier is used to control a variable-gain device such as a power amplifier which provides the input to the first squaring cell, thereby closing the feedback loop around the first squaring cell. Accurate square law approximation at microwave frequencies can be achieved by implementing the squaring cells as series-connected three-transistor multi-tanh transconductance cells. By using carefully balanced squaring cells and a well-balanced error amplifier, approximation errors are cancelled and accurate RMS measurement is realized at high frequencies. A feedforward bootstrapping feature uses an op amp to balance the voltages at the common nodes of the transconductance squaring cells and also provides a balanced differential input drive to one of the squaring cells. A base current compensation circuit for providing accurate base compensation current to both of the squaring cells prevents errors due to DC offset voltages.

The invention discloses a digital protecting tester which comprises a PWF main control board, a FT3 board, an input measuring board, an output measuring board, an Ethernet interface and an optical fiber interface. An automatic closed loop test system comprises a computer, a network connecting device and the digital protecting tester, and the digital protecting tester is connected with a protecting device by the optical fiber interface and is used for sending a sampling value and issuing/subscribing GOOSE information. An automatic closed loop test method comprises the following steps of: establishing a test task according to a test plan by a tester, automatically configuring GOOSE parameters and automatically reading/writing the set value of a relay protecting device; simulating a fault according to the test task and the protecting set value and automatically analyzing GOOSE data to obtain a test result; automatically reading the sampling value of the relay protecting device; automatically reading the switching-off/switching-on report of the protecting device; and automatically generating a complete test report by software after completing test. By the invention, the automatic test can be completed, the test efficiency is improved, and the workload of the tester is lightened.

The present invention relates to voltage measurement apparatus. The voltage measurement apparatus comprises a potential attenuator configured to be electrically connected between first and second conductors, which are electrically coupled to a source. The potential attenuator comprises a first impedance and a reference impedance arrangement in series with each other. The reference impedance arrangement has an electrical characteristic which is changed in a known fashion. The voltage measurement apparatus further comprises a processing arrangement configured: to acquire at least one signal from the reference impedance arrangement, the at least one signal reflecting change of the electrical characteristic in the known fashion; and to determine a voltage between the first and second conductors in dependence on the fashion in which the electrical characteristic is changed being known and the at least one signal.

The invention discloses a structure of a film thermoelectric converter based on a bi-material microcantilevel and a fabricating method thereof. The film thermoelectric converter mainly comprises a heating resistor 1, the bi-material microcantilevel 2 and a sealing ring 3. The principle of the bi-material microcantilevel measuring the temperature of the heating resistor 1 is similar to the principle of the traditional bi-metal temperature sensor, and heat of the heating resistor 1 after the temperature rises leads the temperature of the bi-material microcantilevel 2 to rise through ways of convection, radiation, or heat exchange and the like. Because heat expansion coefficients of two materials made into the bi-material microcantilevel 2 are different, the deflexion at the free end or the strain at the root part of the bi-material microcantilevel 2 is changed, and the temperature information of the heating resistor 1 can be obtained after the shape change of the bi-material microcantilevel 2 is detected by a detection element 9. The film thermoelectric converter based on the bi-material microcantilevel 2 has high sensitivity of measuring the heating resistor 1 by using the bi-material microcantilevel 2, little heat of transmitting to an underlayer through a bi-material microcantilevel temperature sensitive element, and small error of converting alternative current and direct current; meanwhile, the heating resistor can be flexibly designed.

The data storage and processing resources required for an electric meter are reduced by basing the selection and application of phase error correction on a root mean square load current flowing through the meter.

A cabinet formed of a plurality of panels, includes a tamper detection system that includes an electrical circuit for detecting forming of a hole in a protected region of at least one panels. The electrical circuit includes at least one conductive trace on one of the panels. The conductive trace spans a protected region, wherein the minimum distance from any point in the protected region to the at least one conductive trace does not exceed some defined maximum. An electrical current source provides a current through the conductive trace. A sensor is in electrical communication with the electrical current source to sense a change in current provided to the trace and generate a tamper signal in response thereto.

An opto-electric device for measuring the root mean square value of an alternating current voltage comprises: a) an electric field-to-light-to-voltage converter having 1) a light source; 2) an electro-optic material: (a) receiving light from the light source; (b) modulating said light; and (c) providing a modulated light output; 3) an electric field applied to the electro-optic crystal to modulate the light from the light source to produce the modulated light output; b) an optical receiver for receiving and converting the modulated output light from the electro-optic material to a first voltage that is proportional to a square of the electric field applied to the electro-optic material; c) an averager circuit receiving the first voltage and providing a second voltage that is proportional to the average of said square of said electric field over a period of time; and d) an inverse ratiometric circuit receiving the second voltage from the averager circuit and returning a third voltage that is an inverse voltage of the second voltage to the electric field-to-light-to-voltage converter to produce an output voltage that is the root mean square voltage of the applied electric field. The device uses a Mach_Zehnder interferometer operating a a square law device and features a housing for maintaining the interferometer at constant temperature using a temperature control unit. A nulling circuit is provided to maintain the interferometer at it null operating point as are calibration circuits to correct for voltage amplitude and frequency changes.

A method and system for measuring electric current in a plurality (n) of conductors. According to the invention, the method comprises the following steps: an electric current transducer is place substantially opposite to each conductor (I, i=1, . . . , n); a decorrelation matrix ([G]), which is a function of the position of the transducers in relation to the conductors, is constructed; the current (I_mesi) in each conductor (i) is measured with the aid of electric current transducers and real currents (I_reeli) are deduced with the aid of the decorrelation matrix ([G]) and the measured currents (I_mesi).

A method identifies electric load types of a plurality of different electric loads. The method includes providing a support vector machine load feature database of a plurality of different electric load types; sensing a voltage signal and a current signal for each of the different electric loads; determining a load feature vector including at least six steady-state features with a processor from the sensed voltage signal and the sensed current signal; and identifying one of the different electric load types by relating the load feature vector including the at least six steady-state features to the support vector machine load feature database.

The invention provides a device capable of measuring physical quantity of alternating current at a long distance. The device comprises an analogue sampling passageway, a sampling switch, a register, a bus and a timing controller, wherein the analogue sampling passageway is used for inputting the alternating current to carry out analogue sampling so as to output an analogue sampling value, the sampling switch is used for resampling so as to obtain a remote-measurement data frequency required at a receiving side, the register is used for storing a resampling value from the sampling switch, the bus is used for outputting the resampling value in the register to the receiving side, and the timing controller is used for controlling resampling frequencies of the analogue sampling passageway and the sampling switch; and the device is characterized by further comprising a digital low-pass filter which is used for filtering a high-frequency component in the sampling value, wherein an input of the digital low-pass filter is connected with the analogue sampling value output by the analogue sampling passageway, an output of the digital low-pass filter is connected with the sampling switch, and cut-off frequency of the digital low-pass filter must be 0.5 folds smaller than the resampling frequency of the sampling switch. The invention also provides a corresponding method. When the device is adopted, the remote measurement accuracy of power physical quantity is increased, a waveform value is output through resampling, and an effective value, a steady-state value as well as a fundamental harmonic effective value and steady-state value are also output, so that many requirements of the receiving side for remote measurement data can be met.

A system for fault prediction in electrical systems. It includes a network of recording nodes that transmit data to multi-channel recorder. The nodes monitor power quality based on a number of system parameters. These data are assembled into data blocks and are analyzed to determine load factors for the system over time. Data blocks are collected over 22 cycle periods and are evaluated against a derived standard deviation factor for the given system. The standard deviation is used to determine alert and alarm levels. The constant monitoring allows the system to alert workers of a potential upcoming fault in one or more system components. In this way repairs can be made before the component fails and the system experiences a fault condition.

The invention relates to a method and device for flexibly identifying residual current-type electrical fire on line. The method comprises the following steps: arranging a residual current mutual inductor in a power transmission and supply circuit of a low-voltage power distribution system; obtaining an instantaneous value irz of lumped residual current in the circuit as well as waveform which areacquired by the mutual inductor through a power supply branch residual current and other signal detection unit; and according to the characteristics such as abrupt change, discontinuity and nonlinearity of a spot-heat agglomeration residual current instantaneous value ird, separating and extracting ird from irz by adopting a modern information processing technology, and calculating an effective value Ird of ird so as to identify whether potential electrical fire danger exists according to the size of Ird. The on-line identification device consists of three parts such as a residual current signal processing unit, the power supply branch residual current and other signal detection unit and an output execution unit. By adopting the residual current-type flexible on-line electrical fire identification method and device, the features of the potential electrical fire danger caused by electric arc grounding faults can be accurately extracted, normal residual current and abnormal residual current can be correctly identified, and alarm failure and false alarm can be avoided.

The invention provides a grid voltage stabilization on-line monitoring method based on voltage stability local indexes, comprising the following steps: calculating single power consumption transmission equivalence system parameters of a monitored node according to grid topology structure parameters and relevant node voltage current phasor in adjacent areas of the monitored node; using the single power consumption transmission equivalence system parameters to identify the influence of a system outside the area on the monitored node to obtain a single power consumption transmission equivalence system expanded by the monitored node; calculating voltage stability local indexes of the monitored node according to the expanded single power consumption transmission equivalence system parameters; judging whether the monitored node is a weak node according to the node voltage stability local indexes; and if so, performing voltage stability warning. The identified initial value is the calculatedsingle power consumption transmission equivalence system parameter. The invention can solve the problem of misjudgment of index values generated by incorrect identified parameters when the continuousexcitation condition is not satisfied; the method has fine index value performance, can judge the weak node correctly, and realize on-line monitoring of the grid voltage stability.

The invention discloses a non-invasive method and a system for monitoring an electric load alarm. The method comprises the following steps: obtaining a terminal voltage and a total current at the inlet of an electric load power supply at the current moment; performing electric load characteristic extraction on the terminal voltage and the total current to obtain an electric load characteristic atthe current moment; performing electric load decomposition on the terminal voltage and the total current according to the current electric load characteristic; obtaining a type, a current working state and current electric consumption information of each electrical equipment in the electric load; and generating electric consumption abnormal alarm information of the electrical equipment according to the current electric consumption information and a reference electric consumption information. Once any of the current electric consumption information of the electrical equipment is abnormal, the system can timely discover it and give an alarm. Users can timely view and process the abnormal condition according to the type, the current working state and the abnormal electric consumption information of the electrical equipment with abnormal electric consumption in the abnormal electric consumption alarm information of the electrical equipment.

The invention aims to provide a system for monitoring the state of a harmonic load. The system is realized by a following method as follows: an everyday sample is established according to statistic characteristic quantity of historical data corresponding to the effective value of every-order harmonic current; a population sample in any time period is established according to the everyday sample; a normal cloud model of the effective value of the every-order harmonic current is established and converted to the boundary membership under a standard normal cloud model according to the statistic rule of the population sample, so as to establish a retrieval body of the harmonic current. By the system, the state of the harmonic load can be diagnosed and minored in real time according to the retrieval body of the harmonic current; the system is applicable to the occasion when the running state is abnormally small; and the method has a certain practical value in engineering.

The invention relates to a high frequency sin wave virtual value digital real-time detection technology, in particular to a high precision high frequency sin wave virtual value real-time detection method based on the field programmable gata array (FPGA) high-speed data processing technology. The method includes the steps of taking any one sampling point as a nth point from sampling points m in a cycle of sine wave, calculating sin wave virtual values from n to n+m-1, wherein the sampling amplitude is xi in a cycle, and calculating Sn+1, Sn+2, ..., Sn+m-1; taking a mean S of m virtual value data Si (i=1, 2... m) as a virtual value of the sine wave. The calculation error is little, the computing speed is fast, the scope of application is wide, and the virtual value detection of the sine wave which ranges from tens of KHz frequency to hundreds of KHz can be achieved by changing parameters.

The method includes measuring an operating parameter comprising at least one of a phasor current and phasor voltage of an electrical machine. The method further includes determining a diagnostic parameter indicative of a fault of the electrical machine based on the measured operating parameter. The method also includes estimating end of life of the electrical machine based on the diagnostic parameter using an error minimization method.

The invention relates to a measuring method for an effective value of an electric parameter of an electric motor powered up by a frequency converter and a frequency control system. The method comprises the following steps of: (a) obtaining a period T of the electric parameter, determining the sampling frequency N according to the period T, and establishing an array {p(0)2, p(1)2, p(2)2, to p(N)2, p'} for data storage; (b) sampling the electric parameter N times in one period T, and sequentially storing the square of the sampling value to p(1)2, p(2)2, to p(N)2; and (c) utilizing a formula to compute the effective value P of the electric parameter in the period T. By adopting the method, the effective value of a non-sinusoidal periodic electric signal can be precisely obtained in real time, the computational method is simple, the treatment of an arithmetic unit is convenient and fast, the requirements for hardware are low, and the practical degree is high.