A method for detecting an open-phase condition of a transformer having a grounded-wye high voltage side connection including monitoring current flowing in a neutral connection on the high voltage side of the transformer in real time by voltage relaying and current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude. A current signal may be injected onto the neutral terminal and the zero-sequence mode of the transformer monitored to detect an open-phase condition indicated by an increase in network impedance and decrease or elimination of the injection current.

Embodiments of the disclosure relate to detecting turn-to-turn faults in one or more windings of various objects. In one implementation, a fault detector uses a differential protection algorithm to detect a turn-to-turn fault in a winding of a three-phase shunt reactor. Various voltage and current measurements carried out upon the three-phase shunt reactor are used to calculate a difference value between a voltage-based parameter and a current-based parameter. The voltage-based parameter is indicative of a normalized negative voltage imbalance and the current-based parameter is indicative of a normalized negative current imbalance. A turn-to-turn winding fault is declared when the difference value is not equal to zero.

Methods and apparatus for energizing a wound component are described. In one arrangement, a method of energizing a component with an alternating voltage is provided. The component comprises a coil wound on a magnetic core. The method comprises applying a voltage across the coil that has a first waveform during a first time period and a second waveform during a second time period. The second time period is subsequent to the first time period. The second waveform comprises an oscillating function comprising a sequence of identical waveforms. The first waveform is such that if the coil had zero electrical resistance the variation of flux density in the magnetic core with time would change sign at least once during the first waveform.

A measurement method is for determining core losses, which serve to produce magnetic circuits for electrical machines. In order to allow an accurate measurement that is as quick as possible, it is proposed that a magnetic coupling is produced between a measuring coil connected in a capacitor and a core to be measured, and the measuring coil is then acted upon by an alternating frequency in order to measure the resonant frequency of the resulting resonant circuit and/or the quality of the resulting resonant circuit as a measure of the core loss.

A power inductor includes: a body including a magnetic material; an internal coil disposed in the body and including a plurality of coil patterns; and a sensing coil disposed on the body and facing the internal coil.

An electricity meter for metering an amount of energy in accordance with a primary AC current and an AC supply voltage. The electricity meter comprises a current transformer comprising the primary conductor, a secondary winding, an auxiliary winding, and a magnetic core arranged to be magnetically coupled with the three windings. The electricity meter further comprises a circuit configured to provide the auxiliary winding with a test signal modulated in accordance with at least one of a first and a second modulation state. The test signal has the same frequency as the AC supply voltage. The electricity meter further comprises an electrical energy consumption measurement unit, coupled to the secondary winding, and being configured to provide a first test value as a function of a secondary current flowing through the secondary winding when the test signal is in a first modulation state, to provide a second test value as a function of a secondary current flowing through the secondary winding when the test signal is in a second modulation state, and to determine, on the basis of the first and second test values, whether a measurement fault warning signal is to be generated.

The present invention discloses a method for the detection and diagnosis of faults in running electric machines. The method consists of: i) simultaneously obtaining a current signal and a voltage signal associated with the rotor winding of the electric machine; ii) defining a group of vectors whose components are DC and/or AC values at different separation and amplification levels of the current and voltage signals; iii) simultaneously obtaining a current signal and a voltage signal associated with an emulated fault; iv) defining a group of vectors whose components are DC and/or AC values at different separation and amplification levels of the current and voltage signals associated with an emulated fault; v) determining the variations in the components of the vectors; vi) comparing the vectors that show component variations with the emulated fault vectors; vii) analyzing the variations and comparisons in order to detect whether or not there is at least one type of fault; and viii) reporting the presence or absence of at least one type of fault in the electric machine. The present invention also discloses a system to carry out this method, consisting of: i) a unit that obtains the current and voltage signals associated with the winding of the electric machine; ii) a unit that emulates faults; iii) a unit that sensitizes the signals by separating the DC and/or AC levels and amplifies the resulting signal; iv) a memory unit that stores the DC and/or AC values; and v) a unit that processes, analyzes and reports on the status of the machine.

A CNG leak detection system has a plurality of CNG tanks. A plurality of control valve mechanisms, equal in number to the plurality of CNG tanks, is coupled with each CNG tank. A sensor is coupled with each control valve mechanism. The sensor monitors the CNG in the tank. A processor is electrically coupled with the sensor. A display is coupled with the processor to display the sensed condition of at least one desired tank of the plurality of tanks.

A threshold voltage measuring device may include a metal-oxide-semiconductor (MOS) transistor, a drain voltage clamping circuit configured to control a drain voltage of the MOS transistor wherein the drain voltage having a substantially constant level, and a constant current supply circuit configured to cause a drain-source current to flow through the MOS transistor wherein the drain-source current having a substantially constant magnitude.

A method and system are disclosed for detecting turn-to-turn and phase-to-phase winding short circuits in an electric motor. The motor is tested at a standstill condition by injecting a current signal into the virtual d-axis of the motor while controlling q-axis current to zero. Steady state feedback current from the motor is measured, and current harmonics are calculated using FFT or peak-to-peak techniques. It is determined that a short circuit is present in the winding if feedback current harmonics higher than a nominal level are detected, where the increased feedback current is an indication that winding inductance has decreased due to a short circuit. Testing at standstill using a small current advantageously prevents the possibility of damaging the motor and avoids inductance variation due to changing rotor position.