Examples of operating an Intelligent Electronic Device (IED) during power swings, are described. In an example, voltage measurements for a phase is received and sampled. Root mean square (RMS) values of the voltage samples is calculated based on the voltage measurements. Delta quantities for each phase are calculated based on the RMS values. Each of the RMS values and delta quantities are associated with respective sampling instants. In response to a delta quantity being greater than a predefined threshold, a peak delta quantity is detected. A time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity is determined. Based on a comparison of the time interval with a threshold time, a disturbance condition may be detected as a power swing and consequently, fault detection at the IED may be blocked.

A current measuring device for switched-mode electronic power converters includes two independent sensors connected in series for the current to be measured, one of said sensors providing an admittance and the other providing a conductance. The current measuring device further includes a parallel current measuring resistor and an average value capacitor which are connected in parallel contribute to the provided admittance. The conductance is provided by a serial current measuring resistor as one of the sensors. The current to be measured has both DC and AC current components. The current measuring device further includes a filter is transferred back into the power path or merged with the current measuring sensors.

A current measuring device for switched-mode electronic power converters includes two independent sensors connected in series for the current to be measured, one of said sensors providing an admittance and the other providing a conductance. The current measuring device further includes a parallel current measuring resistor and an average value capacitor which are connected in parallel contribute to the provided admittance. The conductance is provided by a serial current measuring resistor as one of the sensors. The current to be measured has both DC and AC current components. The current measuring device further includes a filter is transferred back into the power path or merged with the current measuring sensors.

A method for determining a capacitance value of a capacitor is provided. The method includes receiving a current signal flowing through the capacitor and receiving a voltage signal applied across the capacitor. The received voltage signal and the received current signal are filtered with a low pass filter. The filtered voltage signal and the filtered current signal are then discretized. The discretized voltage signal and the discretized current signal are transformed into a frequency domain. The capacitance value of the capacitor is determined from the transformed voltage signal and the transformed current signal.

A method for determining a capacitance value of a capacitor is provided. The method includes receiving a current signal flowing through the capacitor and receiving a voltage signal applied across the capacitor. The received voltage signal and the received current signal are filtered with a low pass filter. The filtered voltage signal and the filtered current signal are then discretized. The discretized voltage signal and the discretized current signal are transformed into a frequency domain. The capacitance value of the capacitor is determined from the transformed voltage signal and the transformed current signal.

A method and system measure a characteristic of a signal under test (SUT) using a signal measurement device. The method includes receiving and digitizing the first and second copies of the SUT through first and second input channels to obtain first and second digitized waveforms; repeatedly determining measurement values of the SUT characteristic in the first and second digitized waveforms to obtain first and second measurement values, which are paired in measurement value pairs; multiplying the first and second measurement values in each of the measurement value pairs to obtain measurement products; determining an average value of the measurement products to obtain an MSV of the measured SUT characteristic; and determine a square root of the MSV to obtain an RMS value of the measured SUT characteristic. The RMS value substantially omits variations not in the SUT, which are introduced by only one of the first and second input channels.

A method of estimating a root mean square (RMS) of an alternating current (AC) voltage is provided. The system includes a rectifier configured to rectify the AC voltage and a controller configured to derive a delayed AC voltage by delaying the rectified AC voltage by a preset delay time. The controller is configured to estimate a root mean square (RMS) of the AC voltage based on the rectified AC voltage and the delayed AC voltage.

A method of estimating a root mean square (RMS) of an alternating current (AC) voltage is provided. The system includes a rectifier configured to rectify the AC voltage and a controller configured to derive a delayed AC voltage by delaying the rectified AC voltage by a preset delay time. The controller is configured to estimate a root mean square (RMS) of the AC voltage based on the rectified AC voltage and the delayed AC voltage.

A high voltage phasing voltmeter comprises first and second probes. Each probe comprises an electrode for contacting a high voltage electrical conductor. The electrodes are connected in series with a resistor. A meter comprises a housing enclosing an electrical circuit for measuring true rms voltage. The electrical circuit comprises an input circuit for connection to the first and second probes and developing a scaled voltage representing measured voltage across the electrodes. A converter circuit converts the scaled voltage to a DC signal representing true rms value of the measured voltage. A peak hold circuit is connected to the converter circuit to hold a peak value of the true rms value. A display is connected to the peak hold circuit for displaying the peak value of the true rms value.

A high voltage phasing voltmeter comprises first and second probes. Each probe comprises an electrode for contacting a high voltage electrical conductor. The electrodes are connected in series with a resistor. A meter comprises a housing enclosing an electrical circuit for measuring true rms voltage. The electrical circuit comprises an input circuit for connection to the first and second probes and developing a scaled voltage representing measured voltage across the electrodes. A converter circuit converts the scaled voltage to a DC signal representing true rms value of the measured voltage. A peak hold circuit is connected to the converter circuit to hold a peak value of the true rms value. A display is connected to the peak hold circuit for displaying the peak value of the true rms value.