Abstract: A system and method for detecting a current imbalance and a voltage imbalance in multiphase electrical energy provided to an energy meter. A phase single value is measured for each phase, a normalized phase value for each phase is determined, and a normalized phase value is compared to a first threshold, and the normalized phase value ratio is compared to a second threshold. It is determined that an imbalance exists when the high normalized phase value is greater than the first threshold and the normalized phase value ratio is less than the second threshold.

Abstract: An apparatus for determining loss of reference voltage (indicating possible tampering) in a 2-element electronic meter that includes a processor for determining electrical power from voltage and current signals, and a display for indicating an operating status of the meter. To determine if the reference voltage of the meter in a 3-wire delta or network installation has been lost, a measurement of the phase angle difference between the two phases is made. If the phase difference is equal to a predetermined value, the meter indicates on the display that loss of reference voltage and possible tampering has taken place. The apparatus may further be adapted to determine a length of time that this condition has occurred such that the appropriate enforcement and billing agencies may be informed.

Abstract: An apparatus for metering electrical energy over a predetermined range of voltages within a single meter. The meter includes a divider network for dividing the voltage to generate a divided voltage. The divided voltage is substantially linear with minimal phase shift over the wide dynamic range. A processing unit processes the divided voltage and a current component to determine metered electrical power. A power supply receives the voltage component and generates a supply voltage from the voltage component over the predetermined range to power the processing unit. The power supply may include a transformer having first, second and third windings, so that the voltage component is provided to the first winding and the second winding defines the output of the power supply. A switching member is connected to the first winding for permitting and preventing the flow of current through the first winding.

Abstract: A method of manufacturing a transformer coil encapsulated in casting resin utilizing a disposable casting mold where the disposable mold acts both as a winding mandrel and as an inner mold shell for resin encapsulation. The disposable casting mold may be oval shaped or circular shaped depending upon the desired shape of the coils to be encapsulated. The inner and outer mold shells are made from thin sheet metal and thus may be adjusted for the manufacture of a wide variety of sizes of oval shaped or circular shaped epoxy encapsulated coils.

Abstract: A method of manufacturing transformer windings embedded in casting resin is disclosed which utilizes an integrated winding mandrel for producing a non-standard oval shaped epoxy encapsulated low voltage coil for dry type distribution transformers. The method includes a process of winding a low voltage oval coil over a disposable mold which acts as both a winding mandrel and as an inner mold shell for epoxy encapsulation. Both the inner and outer molds are made of low cost sheet metal utilizing a “wrap and band” process The complete winding and molding processes can all be conducted on a standard winding machine.

Abstract: A stacked magnetic transformer core is disclosed with center leg curvilinear S-joints for reducing losses and for minimizing waste or scrap material during the manufacture of the laminations.

Abstract: A Voltage Instability Predictor (VIP) estimates the proximity of a power system to voltage collapse in real time. The VIP can be implemented in a microprocessor-based relay whose settings are changed adaptively to reflect system changes. Only local measurements (voltage and current) at the bus terminal are required. Contrary to the most common strategy to maintain voltage stability, which is to shed blocks of load when the voltage drops below a certain fixed threshold, which threshold is difficult to select since voltage magnitudes are a poor indicator of how close the system is to a collapse, the inventive VIP detects this proximity to collapse by monitoring the relationship between the apparent impedance {overscore (Z)}app and the Thevenin-impedance circle.

Abstract: A clamp for mounting a drip tray to a transformer fuse holder has only two connecting members which are a first arm and a second arm. The first arm comprises a proximal end attached to the drip tray and a distal male end. The second arm comprises a proximal end attached to the drip tray and a distal female end. The male end comprises an insertion member, a male mating detent protruding from the insertion member, and a male locking detent protruding from the male end. The female end comprises a receiving member, a female mating detent protruding from the receiving member, and a female locking detent protruding from the receiving member. When the insertion member mates with the receiving member, the male mating detent and the female mating detent align, and the male locking detent and the female locking detent align such that the clamp becomes locked in three perpendicular directions.

Abstract: Lifting tools for safe, 90 degree rotation of large, heavy objects are disclosed. A lifting tool includes a bar that can be positioned generally parallel to a centerline of the object, and first and second clamps that are rotatably or slidably coupled to first and second ends of the bar, respectively. The clamps are adapted to secure the tool to edges of the object. The tool also includes a pivot arm that is rotatably coupled to the bar, which allows the object to be lifted, rotated up to 90 degrees, moved, and then set down. The pivot arm includes a pair of idler pulleys disposed along a length thereof. A first end of the pivot arm can be coupled to a hoist hook, for example, via a cable that wraps partially around the pulleys and is coupled to the bar at a point between the clamps.

Abstract: A mapper to translate an input file from an input domain to an output domain. The mapper includes a canons utility which builds a canon, the canon being a tree relating all data attributes within a domain of information, and the domain being a collection of data that has a same data format, a maps utility which creates input and output maps that specify the translation from the input domain to the output domain, and a translator utility to perform the translation of the input file to an output file. The input map is a data structure that describes a format of the input domain and the output map is a data structure that describes a format of the output domain. The input map and the output map are derivation trees, and the mapper utilizes the input map and the output map to build a scanner/parser for the input file domain. The mapper traverses the input map to parse data from the input file into a list.

Abstract: A method and apparatus for over current backup protection is provided. The method generates a set of root mean square (rms) values from samples that are taken from the system current. Several rms current values are averaged to generate an estimated rms over current value. The estimated over current value is compared with a predetermined threshold value. If the estimated current is above the predetermined threshold value, a fault protection mechanism, such as opening a circuit breaker, is activated. A generator protection unit having digital signal processing capabilities executes the inventive method to provide protection from over current episodes.

Abstract: An electronic circuit, such as a UPS, interfaces a main ac power source and at least one secondary power source to a load. The secondary power source(s) may include one or more auxiliary generators, a flywheel motor generator or microturbine with high speed motor generator, and/or any of a variety of dc storage devices. The electronic circuit includes a dc bus, a first uncontrolled rectifier in combination with a first filter for coupling the main ac power supply to the dc bus, one or more additional uncontrolled rectifier(s) and filter(s) for coupling the auxiliary generator(s) to the dc bus, and a dc-to-ac inverter (between the dc bus and the load) for providing ac output power to the load. The advantages of reduced parts count, increased compatibility between the generator(s) and the electronic circuit, and a simpler method for paralleling many storage and generation devices with a very high power factor to the sources, regardless of the load power factor, are provided.

Abstract: A method and system for preventing sustained resonance conditions in a power system involves measuring voltage and current samples on a conductor to which a plurality of controlled capacitors are operatively coupled. The measured voltage and/or current is utilized to identify a resonance condition. The method or system determines whether the resonance condition is due to switching of a controlled capacitor and, if so a corrective switching operation is performed after a first time delay. If the resonance condition is determined not to be due to the switching of a capacitor, then a second switching operation, in which a second controlled capacitor is switched after a second time delay, is performed. The second time delay is preferably greater than the first time delay.

Abstract: A coil for use in the voltage section of the electromagnet in electromechanical utility watthour meters comprises a thermoplastic bobbin, a length of wire, and two terminals. The bobbin has an upper flange and a lower flange connected by a central, hollow core. The upper flange supports two terminal mounting boxes in which terminals are inserted. The first and second leads (i.e., wire ends) are electrically and mechanically isolated from each other in order for the coil to withstand high voltage power surges. The upper flange also supports a step that has a recessed, side profile that guides the path of the wire to the core without introducing sharp bends or turns into the wire. Excess length of the first and second ends of the wire length are secured to tie off posts that are located on the top of the terminal mounting boxes. These posts, along with the excess wire, are removed when the terminals are inserted into the mounting boxes.

Abstract: A low cost voltage disturbance mitigation system is capable of providing continuous power to a load despite short interruptions or sag disturbances of the utility power. The interruption and sag mitigation system makes use of a combination of unique thermal and electrical properties of magnetic components, power semiconductor devices, and high-discharge-rate energy storage devices. It also facilitates a modular solution that can be easily and economically scaled up or down for use over a wide range of voltage and power levels, e.g., 480 V to 36 kV and 500 kVA to 10,000 kVA.

Abstract: As a variation of the non-orthogonal filter, a phasor estimate is computed by using an N-point window. An aspect of the sub-window cosine filter is to repeat the basic cosine filter for only selected points of the window. In the end, a least-squares fit is used to obtain an estimate for the phasors components. Previous cosine techniques use a data window whose length is greater than 1 cycle while the present invention requires only 1 cycle.

Abstract: A power supply system for providing long and short term backup power to a load comprises a microturbine system, a flywheel system, and a power electronics module. The microturbine system includes a microturbine attached to a first, high speed motor-generator that includes a first stator, and the flywheel system includes a flywheel attached to a second motor-generator. The microturbine system is started by a direct connection of a high frequency AC voltage output of the flywheel system (in the range of from about 500 Hz to about 2 kHz) to the stator of the first motor-generator. The direct connection of the high frequency AC voltage to the stator involves no intervening electronics.

Abstract: A high sample rate cosine filter eliminates DC components by summing them such that they sum to zero. A non-orthogonal cosine filter is also provided. When the cosine filter is applied for N=4 samples per cycle, the samples are separated by 90 degrees. However, at higher sampling rates, it is not necessary to wait for 90 degrees to estimate the phasor value. Non-orthogonal components are used to estimate the phasor value. The time delay associated with the cosine filter is reduced in the process.

Abstract: A ground fault location system is used in a multi-phase ungrounded or high-impedance grounded power network. A signal generator is coupled to the network at a first location and generates for each network phase an individual non-DC voltage signal between such phase and ground. A ground fault detector is coupled to the network at a second location and has a summing device and an annunciator. The summing device is coupled to all of the phases of the network at such second location, sums any current passing therethrough, and produces a sum signal. The annunciator receives the sum signal and provides an indication when such signal is non-zero. Each phase of the network at the second location has a distribution current passing therethrough, the sum thereof normally being substantially zero and resulting in a substantially zero sum signal and the lack of an indication from the annunciator based on such distribution currents.

Abstract: A 2-element, three voltage connection electronic energy meter is disclosed for measuring 3-phase electrical energy supplied by a 4-wire delta service without external potential transformers. The meter employs non-isolating voltage sensors for sensing the line voltages and includes and an automatic service type detector and isolation detector. The meter generates voltage and phase angle measurements for each of the two voltages sensed by the meter. The service type detector compares the phase angles to automatically determine the service type supplying the electrical energy to the meter. The isolation detector compares the two voltages to automatically determine whether or not the installation includes external potential transformers. If the service type is a 4-wire delta service and no external potential transformers are used at the installation for isolating the voltage signals, the meter doubles the voltage measured over the first of the two elements when generating power measurements.