In an example method of trimming a voltage reference circuit, the method includes: setting the circuit to a first temperature; trimming a first resistor (R.sub.DEGEN) of a differential amplifier stage of the circuit; and trimming a first resistor (R1) of a scaling amplifier stage of the circuit. The trimming equalizes current flow through the differential amplifier stage and the scaling amplifier stage. The method includes: trimming a second resistor (R2) of the scaling amplifier stage to set an output voltage of the circuit to a target voltage at the first temperature; setting the circuit to a second temperature; and trimming a second resistor (R.sub.PTAT) of the differential amplifier stage, a third resistor (R1.sub.PTAT) of the scaling amplifier stage, and a fourth resistor (R2.sub.PTAT) of the scaling amplifier stage to set the output voltage of the circuit to the target voltage at the second temperature.

To allow reliable current measurement of the output current of the switching stage of an inverter, especially at switching frequencies of the semiconductor switches in the 100 kHz range, a voltage at the choke is measured and integrated over time to be representative for the leg current in the choke. The time integral is processed in a processing unit, whereas the processed time integral is used in an inverter controller for controlling the inverter. The voltage at the choke is analogously integrated over time by two serially connected integrator capacitors, whereas across each of the integrator capacitors a reset switch is provided, for alternately resetting the corresponding integrator capacitor.

To allow reliable current measurement of the output current of the switching stage of an inverter, especially at switching frequencies of the semiconductor switches in the 100 kHz range, a voltage at the choke is measured and integrated over time to be representative for the leg current in the choke. The time integral is processed in a processing unit, whereas the processed time integral is used in an inverter controller for controlling the inverter. The voltage at the choke is analogously integrated over time by two serially connected integrator capacitors, whereas across each of the integrator capacitors a reset switch is provided, for alternately resetting the corresponding integrator capacitor.

A monitoring system includes an array of optical sensors disposed within a transformer tank. Each optical sensor is configured to have an optical output that changes in response to a temperature within the transformer tank. An analyzer is coupled to the array of optical sensors. The analyzer is configured to determine a sensed temperature distribution based on the sensed temperature. The sensed temperature distribution is compared to an expected distribution. Exterior contamination of the transformer tank is detected based on the comparison.

An impedance sensing circuit includes first and second current sources and first and second bias current sources that are appropriately coupled to first and second resistors. The impedance sensing circuit also includes a comparator that compares a first voltage based on the first terminal of the first resistor to a second voltage based on the first terminal of the second resistor to generate a comparator output signal. Either the comparator output signal or a digital signal based on the comparator output signal operates to regulate the current signals output from the first and second current sources so that the first voltage is same as the second voltage. The comparator output signal and the digital signal is representative of a difference between the first voltage and the second voltage that is based on an impedance difference between the first resistor and the second resistor.

An energy harvesting device (CTH) installed in an electrical distribution system (EDS) for powering ancillary electrical devices (AD) used in the distribution system. The device includes a first voltage regulator circuit (CC) configured to produce a voltage matched to a power curve of a current transformer (CT) to which the device is electrically coupled. The device also includes a second and separate voltage regulator circuit (SVR) which continuously operates to maximize the amount of electrical energy recovered from the current transformer.

An energy monitoring device includes a power supply circuit electrically coupled to a power source via a hot conductor and a load via a load conductor; a relay circuit including a relay and a relay driver circuit, where the relay includes a plurality of coils and the relay contact electrically coupled to the hot conductor and the load conductor; a sensing circuit including a hot voltage sensor and a load voltage sensor; and a controller electrically coupled to the power supply circuit, the relay driver circuit, and the sensing circuit, and structured to receive a hot voltage from the hot voltage sensor and a load voltage from the load voltage sensor, and determine a load current based at least in part on a relay contact resistance of the relay contact and a delta between the hot voltage and the load voltage.

A method for identifying consumer phase connectivity in low-voltage distribution network based on voltage association characteristics is provided. The specific steps thereof are: first, acquiring users to be identified and voltage time series data of three-phase buses on the low-voltage side of the low-voltage distribution network where the users to be identified are located; then, calculating voltage time series curve correlation coefficients among the users, and classifying a user having the maximum voltage time series curve correlation value with respect to the user into one category to form a user category set; then, based on the user classification, determining an initial consumer phase connectivity according to voltage association characteristics between the users and the three-phase buses on the low-voltage side of the low-voltage distribution network; finally, verifying the initial consumer phase connectivity according to the voltage association characteristics among the users to obtain a final consumer phase connectivity identification result.

A power distribution monitoring system is provided that can include a number of features. The system can include a plurality of power line sensing devices configured to attach to individual conductors on a power grid distribution network. The sensing devices can be configured to measure and monitor, among other things, current values and waveforms, phase voltage, conductor current, phase-to-phase voltage, conductor temperatures, ambient temperatures, vibration, wind speed and monitoring device system diagnostics. The sensing devices can include an equipotential surface configured to reduce incumbent E-field disturbance of the conductor. The sensing devices can include a monitor-device conductor shell sized and shaped to position the equipotential surface at a distance with respect to the conductor regardless of diameter of the conductor. Methods of installing and protecting the system are also discussed.

Provided herein are approaches for determining a status of a fuse or relay. In some embodiments, a system may include a first fuse or relay connected between a first input and a first output, and an optocoupler electrically connected with the first fuse or relay, wherein the optocoupler is operable to monitor a differential voltage of the first input or the first output. The system may further include an input/output (IO) expander receiving a status signal representing a state of the first fuse or relay, wherein only a single input port of the IO expander receives the status signal representing the state of the first fuse or relay.