The disclosure relates to a method and related device for approximately determining voltages at a high-voltage side of a transformer on the basis of measured voltages at a low-voltage side of the transformer. The method includes measuring delta voltages and phase voltages and phase angles at the low-voltage side of the transformer, transforming the phase voltages and phase angles into positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the high-voltage side from the positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining estimated values of a zero phase sequence system voltage and of a phase angle of a zero phase sequence system at the high-voltage side from the measured delta voltages and phase voltages and phase angles at the low-voltage side, and transforming the positive, negative and zero phase sequence system voltages and the phase angles into phase voltages and/or delta voltages at the high-voltage side of the transformer.

The present invention relates to a method for power balancing a power grid (10) having multiple phases (12:1,2 3) and a common ground (0). The power grid (10) is connected to at least one load (13, 17) causing a non-uniform power consumption between the multiple phases (12: 1, 2, 3) of the power grid (10). The method comprises: monitoring power provided to the power grid (10) in controller (18), storing available energy in the power grid (10) in an energy storage (16) using multiple inverters (I1, 12, 13), each inverter (I1, 12, 13) is connected between the energy storage (16) and each phase (12: 1, 2, 3) of the power grid (10), and redistributing power between phases (12: 1, 2, 3) based on power available in the energy storage (16) by controlling power flow through the inverters (I1, 12, 13) by the controller (18) based on the non-uniform power consumption.

This voltage imbalance assessment method is for a power conversion device comprising a forward converter for rectifying the voltage of a three-phase AC power supply, a smoothing capacitor for smoothing the rectified voltage, a detection unit for detecting the smoothed voltage, and a control unit. The control unit: uses the detected voltage to generate data indicating frequency components; compares, in the data indicating frequency components, the magnitude of the component that is four times the power supply frequency with the magnitude of the component that is six times the power supply frequency; and assesses the voltage imbalance of the three-phase AC power supply on the basis of the comparison.

A fault detection system has line current monitors. Each line current monitor couples to a line-phase of an electric power transmission system. Each line current monitor has a phase detector, a loop filter and a controlled oscillator, coupled as a phase locked loop. The phase detector has a rotating frame transform. The phase detector couples to a line-phase and provides in-phase and quadrature signals in a rotating frame, based on in-phase and quadrature signals proportional to current in the line-phase. One or more fault detection modules are coupled to the line current monitors through inter-phase communication of the in-phase and quadrature signals in a time frame rotating at the line frequency. The communication may have electrical isolation.

The present disclosure pertains to detection of abnormal, risky, or abberant conditions in a power distribution network and to corresponding trip signals being used to trip open devices such as reclosers upstream of where the abnormal condition is detected. Detection of a missing broadband over power-line signal or of an open circuit between phases of a power distribution circuit may prevent severed conductors from causing a ground fault, therefore avoiding the possibility of fire and dangerous conditions.

The disclosure relates to a method and related device for approximately determining voltages at a high-voltage side of a transformer on the basis of measured voltages at a low-voltage side of the transformer. The method includes measuring delta voltages and phase voltages and phase angles at the low-voltage side of the transformer, transforming the phase voltages and phase angles into positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the high-voltage side from the positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining estimated values of a zero phase sequence system voltage and of a phase angle of a zero phase sequence system at the high-voltage side from the measured delta voltages and phase voltages and phase angles at the low-voltage side, and transforming the positive, negative and zero phase sequence system voltages and the phase angles into phase voltages and/or delta voltages at the high-voltage side of the transformer.

The disclosure relates to a method and related device for approximately determining voltages at a high-voltage side of a transformer on the basis of measured voltages at a low-voltage side of the transformer. The method includes measuring delta voltages and phase voltages and phase angles at the low-voltage side of the transformer, transforming the phase voltages and phase angles into positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the high-voltage side from the positive and negative phase sequence system voltages and phase angles of the positive and negative phase sequence systems, respectively, at the low-voltage side, determining estimated values of a zero phase sequence system voltage and of a phase angle of a zero phase sequence system at the high-voltage side from the measured delta voltages and phase voltages and phase angles at the low-voltage side, and transforming the positive, negative and zero phase sequence system voltages and the phase angles into phase voltages and/or delta voltages at the high-voltage side of the transformer.

A method of detecting phase loss of a three-phase AC power source includes steps of: acquiring any two line voltages of the AC power source with a first cycle period, acquiring a first digital signal and a second digital signal, performing an exclusive OR operation between the first digital signal and the second digital signal to generate a level signal, accumulating a high-level time count value, or accumulating a low-level time count value, resetting the low-level time count value when the high-level time count value is accumulated, or resetting the high-level time count value when the low-level time count value is accumulated, and determining that the AC power source occurs a phase-loss abnormality when the high-level time count value is greater than or equal to ⅓ of the first cycle period or the low-level time count value is greater than or equal to ⅙ of the first cycle period.

Various embodiments relate to detecting loss of electrical energy. A method of detecting loss of electrical energy may include determining, for a number of time samples, a neutral current and an imputed neutral current of an electrical energy metering system. Further, the method may include determining, for each of the number of time samples, a squared difference between the neutral current and the imputed neutral current. The method may further include detecting, based on the squared difference, loss of electrical energy from the electrical energy metering system.

In order to ensure safe operation of a multi-phase system, even a system including a plurality of phases, a number of phase groups is provided, which comprises some of the phases, wherein phase currents of the number of phase groups are merged in a group node to form a group sum current and a group sum current measurement value of the group sum current is captured. The current measurement values belonging to the number of phase groups are summed up to form a group sum and the group sum is compared with the group sum current measurement value to validate the phase currents of the phases in order to ensure safe operation.