An electronic circuit includes a first peak-hold circuit to output a peak surge voltage free of a ringing component included in a voltage at a voltage input node, a second peak-hold circuit to output a peak surge voltage on which the ringing component included in the voltage at the voltage input node is superimposed, and a subtractor to subtract an output voltage of the first peak-hold circuit from an output voltage of the second peak-hold circuit to output a voltage of the ringing component.

An AC/DC leakage detection method, which supports the detection of DC leakage and AC leakage. A DC leakage current and a low-frequency leakage current are measured by means of magnetic modulation technology, an AC signal is measured in the form of pure induction, and two detection modes are performed in a time-sharing manner. A collected leakage signal is converted into a digital signal through an AD converter. By means of the method of the present invention, the processing of a leakage signal is divided into three channels for respectively processing DC leakage, low-frequency AC leakage, and high-frequency AC leakage. The overall effective value of residual current is calculated by integrating results of DC detection and AC detection. The method of the present invention supports the detection of a suddenly increased current; and when there is a suddenly increased current, detection mode switching is performed by detecting the current sudden change of the current.

Methods and apparatus to detect blank images in a digital video broadcast signal are disclosed. An example method of detecting a blank image includes receiving a compressed digital image including a plurality of DC values, analyzing a total number of bits in the digital image to determine if the digital image has a data size small enough to be a blank frame candidate, if the data size is small enough for the digital image to be a blank frame candidate, analyzing multiple areas of the digital image to determine if the multiple areas exhibit substantially a same complexity, if the multiple areas exhibit substantially the same complexity, determining a number of DC values in the plurality of DC values that meet a criterion, comparing the determined number of DC values meeting the criterion to a threshold, and identifying the received digital image as a blank image if the determined number of DC values exceeds the threshold.

System and methods for high accuracy, non-intrusive current sensing are provided. A system may include two magnetic field sensors configured for differential sensing. The system may further include frontend circuitry configured to remove direct current (DC) offset of the magnetic field sensors, upconvert the outputs of the magnetic field sensors, and filter out at least one frequency component from the up-converted signals. The system may receive output signals from the front-end circuitry corresponding to each sensor. The system may further calculate a differential signal based on the output signals. The system may apply optimal detection based on the differential signal and a reference signal to calculate a measurement of current flow. The system may determine a phase angle measurement between the differential signal and the reference signal to calculate a direction of the current flow in the conductor and output various measurement information related to the detected current.

A test and measurement probe system (100,104), including an input (106) to receive an input signal, the input signal including a low frequency (LF) and/or direct current (DC) component and an alternating current (AC) component, an extractor circuit (110), such as an AC coupling circuit or a LF and/or DC rejection circuit, configured to receive the input signal and to separate the AC component and the LF and/or DC component from the input signal, a first output (118) to output the alternating current component to the test and measurement instrument, and a second output to output the direct current component to the test and measurement instrument. In some embodiments, the LF and/or DC component is digitized prior to being output by the second output.

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 includes obtaining electrical measurements of an input signal of a power system. The electrical measurements are obtained at a sampling frequency and the input signal is indicative of an operating frequency of the power system. The method includes generating an intermediate signal from the input signal. The intermediate signal has a direct current (DC) component indicative of a magnitude and a phase of the input signal. The method includes filtering the intermediate signal using an adjustable length filter to obtain the magnitude and the phase of the input signal. The length of the adjustable length filter varies based at least in part on a period measurement of the power system.

The present invention provides a trip control circuit for a circuit breaker capable of breaking a circuit when a fault current occurs due to a DC current component, as well as an AC current. The trip control circuit comprises a current transformer that has a core allowing a circuit to pass through and a secondary coil for detecting a current flowing on the circuit and providing a current detection signal; an oscillation circuit section that configured to apply an electrical signal to the secondary coil to increase a slope of a hysteresis loop of the current transformer to allow the secondary coil to detect a DC current and an AC current; and a trip determining circuit section that configured to compare a current value indicated by the current detection signal with a predetermined reference current value.

A method for determining a direct current component in an electric device that is connected to a high-voltage supply network. The method includes the following steps: acquiring operating noises of the electric device with the aid of acoustic sensors that are part of a portable unit and that provide acoustic signals at the output; breaking the acoustic signals down into their frequency components by a Fourier transformation, yielding a frequency spectrum; determining odd and even frequency components of the frequency spectrum in dependence upon a basic frequency of the high-voltage supply network and setting them in a ratio to one another; concluding that a direct current component is present if the ratio exceeds a predefined threshold value.

Determining direct current (DC) leakage current flowing through an insulating structure in a high voltage DC power system wherein the DC leakage current is a composite DC current having one or more high magnitude momentary spikes, and having a DC component and an alternating current (AC) component, wherein the AC component has a first rate of change, and wherein the DC component has a second rate of change less than the first, having (a) providing a waveform separator which is configured to receive the composite DC current flowing through the insulating structure and to separate the composite DC current into the corresponding DC component and AC component, and (i) receive at least one corresponding digital signal and the DC component, ii) analyze the at least one corresponding digital signal and the DC component, (iii) determine a resultant leakage current flowing through the insulating structure, (b) electrically connecting the waveform separator to the insulating structure, (c) separating, in the waveform separator, the composite DC current into the corresponding DC component and AC component, (d) receiving the AC component in at least one comparator and producing at least one corresponding digital signal, (e) counting one or more positive AC components in the at least one positive voltage comparator, (f) counting one or more negative AC components in the at least one negative voltage comparator, (g) producing at least one positive digital signal corresponding to the counted one or more positive components and a negative digital signal corresponding to the counted one or more negative components, (h) processing the positive digital signal and the negative digital signal, and the DC component, and determining a resultant leakage current flowing through the insulating structure.