718results about "Polyphase network asymmetry measurements" patented technology

A system and method for determining the relative phase of each of a plurality of load meters connected to a three-phase power distribution system. The system includes a gateway that communicates information to and from each of the individual load meters. The gateway generates a timing pulse that is received by each of the load meters. Based upon the delay from the receipt of the timing pulse to the next zero crossing of the single phase power supply received by the meter, the utility can determine the phase of the individual meter. The system can include a feeder meter connected to each phase of the electrical supply system to determine the energy consumption for each of the meters connected to a specific phase. The utility can compare the energy consumption information from the feeder meter to all of the load meters connected to the same phase to determine whether any energy theft is occurring.

This invention deals with an advanced Real-time Grid Monitoring System (RTGMS) suitable for both single-phase and three-phase electric power systems. This invention provides an essential signal processing block to be used as a part of complex systems either focused on supervising and diagnosing power systems or devoted to control power processors interacting with the grid. This invention is based on a new algorithm very suitable for real-time characterization of the grid variables under distorted and unbalanced grid conditions. The main characteristic of this invention is the usage of a frequency-locked loop, based on detecting the grid frequency, for synchronizing to the grid variables. It results in a very robust system response in relation to existing technique based on the phase-angle detection since grid frequency is much more stable variable than the grid voltage/current phase-angle, mainly during grid faults. Moreover, the algorithm supporting this invention is very efficient and can be implemented in regular industrial microprocessors. These features make the RTGMS object of this invention ideal to be applied in the control of distributed generation systems (DGS), flexible AC transmission systems (FACTS), power quality conditioners (PQC) and uninterruptible power supplies (UPS). In all these systems, the fast and precise real time detection of the voltage and/or current sequence components under grid fault conditions is a crucial matter.

The invention discloses an abnormal electricity utilization judgment method based on abnormal analysis of electric quantity, voltage and current. The abnormal analysis of the electric quantity comprises a fluctuation electric quantity analysis process and a zero electric quantity analysis process, wherein the abnormal analysis of voltage comprises voltage phase-failure abnormal analysis, voltage off-normal abnormal analysis and voltage unbalanced abnormal analysis; the abnormal analysis of current comprises a current loss abnormal analysis and current unbalanced abnormal analysis. By analyzing and comparing abnormal data of electric quantity, voltage and current of the users, real abnormal users or electricity stealing users can be determined. The abnormal electricity utilization judgment method based on the abnormal analysis of the electric quantity, the voltage and the current, disclosed by the invention, has the advantages that electricity information of power users can be timely grasped, the electricity stealing behavior is prevented and monitored, and the reliability of power supply is improved.

The invention discloses a phase loss detection method for a three-phase motor and a detection circuit. The phase loss detection method for the three-phase motor comprises the steps of inputting a test current which is less than a starting current of the three-phase motor to the three-phase motor before the start of the three-phase motor; detecting a current value of a winding of the three-phase motor; determining whether the detected current value is less than or equal to a preset current value; and determining phase loss of the three-phase motor when the detected current value is less than or equal to the preset current value. Power supply for the three-phase motor is stopped when phase loss of the three-phase motor is determined. The phase loss detection method for the three-phase motor and the detection circuit are used for solving the problem that a phase loss detection method for the three-phase motor cannot effectively protect the three-phase motor in the prior art, thereby improving the effect of timely protection of the three-phase motor.

Provided is an apparatus and method for determining a faulted phase resulting from a fault in a three-phase ungrounded power system. The method includes comparing a phase angle of an operating phasor to a phase angle of a fixed reference phasor. The operating phasor is derived from a digitized signal sample of a plurality of measured signals of the power system. The method also includes comparing a phase angle difference between the operating phasor and the fixed reference phasor to at least one threshold to determine the faulted phase. The fixed reference phasor may be a phase-to-phase voltage or a positive sequence voltage of the plurality of measured signals of the power system. The operating phasor may be a zero sequence current, a zero sequence voltage or a combination of a zero sequence current and a zero sequence voltage of the plurality of measured signals of the power system.

Power consumption at a site is monitored. An electrical load is connected to a power source by an electrical conductor. A fuel-less energy producing device is electrically connected to a junction along the electrical conductor. A current sensor is electromagnetically coupled to the electrical conductor at a sensing position between the power source and the junction to create a current sensor signal. Sensed current and voltage signals are produced from the current sensor signal. A sensed phase relationship between the sensed signals is determined and compared to a baseline phase relationship to determine the direction of current flow through the conductor. A power source signal, based on the current flowing through the conductor at the sensing position, is created. With some examples a Rogowski type differential current sensor is used. In some examples a single current sensor is used.

The invention relates to a high-voltage capacitor imbalance protecting method for a high-voltage DC transmission system, comprising the following steps of: (1) analyzing imbalance current of a high-voltage capacitor in breakdown of a capacitor element during failure development in a high-voltage DC transmission system; (2) judging a symmetrical or dissymmetrical failure of the high-voltage capacitor in the high-voltage DC transmission system; and (3) proposing a corresponding setting principle and an action strategy aiming at the symmetrical or dissymmetrical failure. The high-voltage capacitor imbalance protecting method for a high-voltage DC transmission system has simple structure, convenience and practicability.

A polyphase power distribution and monitoring apparatus having sets of outputs for each phase of power and monitors for each phase of power disposed in the housing. Each monitor provides a visible display of current for an associated phase of power and an audible alarm for each phase of power if the current exceeds a predetermined value or falls below a predetermined value. In three-phase wye power systems, the apparatus preferaby includes a neutral line monitor, including a neutral line current display and audio alarm, for the neutral line of the wye power circuit. The apparatus preferably is lightweight, elongated, portable, and mountable to the side of an electronic equipment rack. It may also include additional power monitoring systems such as network power monitoring tools for remotely monitoring the apparatus.

The present invention provides a power quality monitoring and recording device of power system. An IEC61850 model is unitedly established at the server end according to an IEC61850 standard requirement. A fault recording logic module and a power quality logic module which have a same hardware platform are provided. The system configuration is realized according to IEC61850-6 and a configuration tool which is used independently is formed. The fault recording and power quality are respectively executed with model building to different logic devices according to IEC61850 standard. Not only is the data recording of power system under fault realized, but also the power quality monitoring to the important transformer substation and power consumer of power system is realized. Powerful support is provided for increasing the supplement of high-quality power to the consumer by the power system. The power quality monitoring and recording device of power system according to the invention can be widely used for various occasions of power quality. The software only requires simple configuration according to requirement in project application. The complicated operation is not required. The project application is extraordinary convenient and flexible.

A multiphase current sensing method wherein the sum of the phase currents is zero including: sensing a.c. and/or d.c. currents in first and second phases; sensing a.c. current in a predetermined a.c. frequency range in a third phase; and combining the current sensed in the first and third phases and the second and third phases and determining a gain correction factor to be applied to the currents sensed in the first and second phases.

A current detector unit has a current detecting portion detecting a current flowing between a three-phase inverter and a direct-current power supply as a detection current; a three-phase current detecting portion for detecting a three-phase current of the inverter based on the detection current; and a judging portion judging, based on the detection current, whether or not a target time point belongs to a period during which the three-phase current can be detected. If the judging portion judges that the target time point belongs to the period, the three-phase current detecting portion detects the three-phase current.

Smart metering device for connecting an end user mains network to a multiple phase power distribution network and monitoring consumption on the end user mains network, comprising: inputs for connecting the smart metering device to multiple phases of the multiple phase power distribution network; single phase low voltage outputs for connecting the end user mains network to the smart metering device; a power circuit between the inputs and the low voltage outputs; a modem for receiving control messages sent from a communication server associated with the power distribution network; a controller communicatively connected to the modem for controlling switching operations in the smart metering device in response to the control messages; and a phase selector communicatively coupled with the controller and comprising input switches for switching the low voltage outputs between different sets of the inputs, each set corresponding to one of the multiple phases of the multiple phase power distribution network.

The invention provides a method and a system for detecting phase failure of a motor. The method comprises the following steps of collecting current value of each phase of the motor, and determining the maximum current value and minimum current value of the current value of each phase; judging whether the maximum current value is greater than the maximum threshold value of the preset current or not and the ratio of the maximum current value and minimum current value is greater than the specific threshold value of the preset current or not; when the maximum current value is greater than the maximum threshold value of the preset current, and the ratio of maximum current value and minimum current value is greater than the specific threshold value of the preset current, outputting a phase failure fault signal. The maximum threshold value of the preset current is greater than the maximum current value of the phase-failure phase of the motor, and is smaller than the minimum current value of each phase in the normal idle running process of the motor; the specific threshold value of the preset current is smaller than 1. The method has the advantage that the phase failure of the motor is detected when the motor works at small current.

An open-phase detecting method wherein a simple hardware structure is used to achieve a reduced cost: the IRQ member is reduced to reduce the load on a CPU; the open phase detection is performed in two items, that is, a phase difference and a voltage sign to reduce the possibility of occurrence of erroneous detections; and any phase that is open can be also determined. In the method for detecting any open-phase of the power supply of a three-phase converter, a neutral point N1 is connected to a negative pole side bus N of the DC side output of the rectifying means; an end of the first resistor of each phase, which connects the first resistor to the second resistor of each phase, is connected to an AD converter via a high input impedance means of the respective phase to detect the voltage of the respective phase; the voltage of the respective phase is outputted to a CPU that serves as an open-phase detecting means; and an open phase is detected when the sings of two of the three line voltages determined based on the voltages of the respective phases are different from each other and a phase difference thereof exhibits a half-wave rectification waveform of 180°.

The invention discloses a method for detecting a default phase of a frequency converter. The method comprises the steps of: sampling an electric signal of one of the three phases of the frequency converter; dividing multiple acquired sampling values into three groups according to the sampling sequence, wherein each group at least comprises three sampling values; operating an absolute value of the mean value of the sampling values in each group; and if the absolute value of the second group is judged to be greater than or less than the absolute values of the other two groups and less than a threshold, determining that the phase is a default phase. By obtaining the absolute values of the mean values of the sampling values sampled for three times, the method for detecting the default phase of the frequency converter, disclosed by the invention, has the advantages of well suppressing the conditions of big actual waveform harmonics and a plenty of burrs, improving accuracy of default phase judgment and being good in practical applicability.

The invention relates to a three-phase power input open-phase detection circuit, which comprises a first current limiting resistor, a second current limiting resistor a third current limiting resistor, a pull-up resistor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a first filter capacitor, a first voltage stabilizing diode, a fourth current limiting resistor, an optical coupler, a triode, a fifth current limiting resistor and a second filter capacitor, wherein the first filter capacitor and the first voltage stabilizing diode are connected to the cathode of the first diode and the anode of the second diode; one end of the fourth current limiting resistor is connected to the cathode of the first diode; the output end collector of the optical coupler is connected to the pull-up resistor, and the output end emitter of the optical coupler is connected to signal ground; the collector of the triode is connected with the input end cathode of the optical coupler, the base of the triode is connected to the fifth current limiting resistor, and the emitter of the triode is connected with the anode of the second diode; one end of the fifth current limiting resistor is connected to the cathode of the fifth diode; and the second filter capacitor is connected to the cathode of the fifth diode and the anode of the second diode. The circuit overcomes the defects of high cost, complex software processing and low reliability in the conventional circuit.

The disclosure relates to a method of detecting the phase-loss state of the three-phase power supply. When the phase-loss condition occurs in the input three-phase power supply of the power converter, it is determined whether the three-phase power source is in the phase-loss state through the characteristic of the frequency and amplitude variations of the ripple voltage of the DC bus, and through the sampling and the continuous detecting of the ripple voltage variations by making use of the sensor of the power converter in cooperation with the software calculation, it is determined whether the three-phase power source is in a phase-loss state. When the detected ripple voltage of the DC bus fulfills the phase-loss conditions, it is determined that the three-phase power source is in a phase-loss state.

The invention is suitable for the field of a three-phase motor and provides an open-phase detection method and detection apparatus for a three-phase permanent magnet synchronous motor. The method comprises the following steps: controlling a straight shaft of a motor rotor to be positioned to the shaft center of a motor A phase winding; detecting currents of B and phase windings; judging whether the B and C phase windings are in an open-phase state based on the currents of the B and phase windings; if the B phase winding or the C phase winding is in the open-phase state, outputting a failure warning signal; if the B and C phase windings are not in the open-phase state, controlling the motor to rotate to the place where a rotor position angle is 30 DEG and recording the rotation angle of a motor; judging whether the motor A phase winding is in the open-phase state based on the rotation angle of the motor; and if the motor A phase winding is in the open-phase state, outputting the failure warning signal. According to the method, the open-phase detection of the star-shape-connected three-phase windings in the permanent magnet synchronous motor is achieved by controlling the straight shaft of the motor rotor to be positioned to the shaft center of the motor A phase winding so as to carry out open-phase judgment on the B and C phase windings, and then by rotating the motor to the place where the rotor position angle is 30 DEG so as to carry out open-phase judgment on the A phase winding.

The invention discloses a detection method and device for high-voltage power quality. A capacitive voltage divider is adopted for measuring a voltage signal, and a low-voltage current transformer with low energy consumption is adopted for measuring a current signal; the measured voltage signal and the measured current signal are simultaneously sent to a data acquisition and processing circuit suspended on a high-voltage side; and corresponding power quality information is calculated and analyzed, is sent to a comprehensive processing unit of a low-voltage part by an optical fiber, and is stored and displayed. The detection device can accurately measure a voltage harmonic signal, provides powerful data for monitoring harmonics, can accurately measure the current signal under the condition of small secondary load and owns wider linear working range. The data acquisition and processing circuit is suspended on the high-voltage side, which can avoid insulation between first load and secondary load, reduces the volume and the weight of the device and saves a great quantity of raw materials. The detection device can be directly installed on various routes when the existing route does not reserve the installation position, thus bringing convenience for improving systems.