Abstract: A system measures the stability of a live a.c. power distribution grid, without disrupting sensitive loads on that grid. The system applies repetitive time-synchronized loads to create current pulses, and resulting voltage instabilities, on the grid. The current pulses are sized to ensure that the resulting voltage instabilities are too small to affect the sensitive loads. Time-synchronized voltage measurement devices record the voltage instabilities. The time synchronization, and the repetitive nature of the current pulses, allow the voltage instabilities caused by the current pulses to be extracted from the larger background voltage variations.

Abstract: A means and method for measuring precise voltage phasors on medium-voltage alternating current (AC) distribution grids, using existing distribution transformers as voltage sensors. The errors introduced by the distribution transformers are minimized by taking into account the transformer's vector impedance, combined with measuring the transformer secondary current phasor. The invention includes a means and a method of measuring the distribution transformer's vector impedance.

Abstract: A method and apparatus for detecting cyber attacks on remotely-operable elements of an alternating current distribution grid. Two state estimates of the distribution grid are prepared, one of which uses micro-synchrophasors. A difference between the two state estimates indicates a possible cyber attack.

Abstract: A method and apparatus for detecting cyber attacks on remotely-operable elements of an alternating current distribution grid. Two state estimates of the distribution grid are prepared, one of which uses micro-synchrophasors. A difference between the two state estimates indicates a possible cyber attack.

Abstract: A method and apparatus are provided for capturing voltage phase angle data on an alternating current power grid. The method includes periodically making a voltage phase angle measurement at each of a plurality of locations on the alternating current power grid relative to a timing reference signal (e.g., a GPS timing signal) that is available at each location. For each of the locations, the voltage phase angle measurements are stored locally at the location. A trigger event is selected that will be simultaneously detectable at two or more of the locations. The method includes monitoring for the trigger event at each of the plurality of locations. In response to detecting the trigger event at one or more of the locations, a select amount of pre-trigger and post-trigger measurements are transmitted over a data communications network to a pre-designated destination from each location at which the trigger event was detected.

Abstract: A means and method for measuring precise voltage phasors on medium-voltage alternating current (AC) distribution grids, using existing distribution transformers as voltage sensors. The errors introduced by the distribution transformers are minimized by taking into account the transformer's vector impedance, combined with measuring the transformer secondary current phasor. The invention includes a means and a method of measuring the distribution transformer's vector impedance.

Abstract: A system and method are provided for measuring a parameter of an alternating current power grid relative to a calibrated fourth signal. The method includes receiving a first signal at an antenna and transmitting it to a signal receiver. A second signal is generated at the signal receiver. A third signal is generated based on the second signal and electrically isolated from the second signal. The third signal is transmitted in the cable toward the measuring device. A fourth signal is generated based on the third signal and electrically isolated from the third signal. The fourth signal, which is calibrated by subtracting a delay constant from the generated fourth signal, is transmitted to the measuring device. The delay constant approximates the delay between receipt of the first signal at the antenna and receipt of the fourth signal at the measuring device.

Abstract: A portable harmonics measurement instrument performs in-situ self-calibration of its current transducers and their associated measurement channels and of its voltage probes and their associated measurement channels. In-situ self-calibration is performed immediately before making a measurement on the alternating current power distribution grid. In-situ self-calibration is performed by means of a built-in voltage reference source and a built-in current reference source, which generate highly-accurate voltage and current calibration waveforms with harmonic components.

Abstract: A portable harmonics measurement instrument performs in-situ self-calibration of its current transducers and their associated measurement channels and of its voltage probes and their associated measurement channels. In-situ self-calibration is performed immediately before making a measurement on the alternating current power distribution grid. In-situ self-calibration is performed by means of a built-in voltage reference source and a built-in current reference source, which generate highly-accurate voltage and current calibration waveforms with harmonic components.

Abstract: A voltage sag generator for alternating current power systems intentionally creates power quality disturbances. The sag generator combines different switching technologies to optimize power dissipation and transition performance.

Abstract: A voltage sag generator for alternating current power systems intentionally creates power quality disturbances. The sag generator combines different switching technologies to optimize power dissipation and transition performance.

Abstract: A voltage sag generator for alternating current power systems intentionally creates power quality disturbances. The sag generator has a switch-mode impedance between its input and its output. Varying the duty-cycle of the switch-mode impedance causes voltage sags.

Abstract: A force-feedback accelerometer to measure small accelerations along two or more co-planar axes. A fiber suspension of a proof mass provides mechanical sensitivity; a cylindrical cross-section on the proof mass, with orthogonal optical position sensing, reduces sensitivity to torsional accelerations. Coupling both proof mass position and proof mass velocity to the feedback force eliminates the disadavantages associated with other forms of damping.

Abstract: A power supply for an instrument that measures waveforms on AC (alternating current) power systems. Under ordinary circumstances, the power supply draws its power from the signal that the instrument measures. The power supply includes energy storage means. When the instrument must make a precise measurement that could be affected by the power drawn by its power supply, the instrument temporarily disconnects its power supply from the measured signal and draws power from its energy storage means, effectively coasting on the stored energy. At the conclusion of the precise measurement, the instrument reconnects its power supply to the signal being measured.

Abstract: An improved system for charging a battery of a hand held device, such as an electric toothbrush. The system has a first coil coupled around a first magnetic core. The first magnetic core forms a substantially closed magnetic path except for a core gap. An AC power signal is applied to the first coil to create a varying magnetic field within the core gap. The core gap is configured to minimize radiation of magnetic flux whether the second magnetic core is in place or not by having its faces closely spaced and aligned substantially parallel to one another. A second coil is coupled around a second magnetic core. The second magnetic core is insertable into the core gap to form an AC current in the second coil. The second magnetic core is sized to substantially occupy the core gap to minimize radiation of magnetic flux. The size of the gap and the length of the second magnetic core are made as small as possible to keep the weight of the hand-held device low.

Abstract: An electronic instrument that records electric power measurements. The instrument contains two types of memories: the first type of memory can tolerate wide fluctuations in ambient temperature but is expensive per unit of storage capacity, and the second type of memory only operates in a narrow ambient temperature range but is inexpensive per unit of storage capacity. For example, the two types of memory may be static Random Access Memory (RAM) and a hard disk drive, respectively. The instrument contains more storage capacity of the second type than storage capacity of the first type. The instrument records all of its measurements in the first type of memory. It also monitors the ambient temperature. When it detects an ambient temperature that will permit the second type of memory to function properly, it flushes the first type of memory into the second type of memory, thus creating space for recording subsequent data in the first type of memory.

Abstract: A system transfers electric power between two devices using a magnetic coupling and no electrical connections. Each device incorporates a magnetic core surrounded by a coil. When properly aligned the cores form a closed magnetic circuit whereby stray magnetic fluxes are substantially reduced. In the preferred embodiment, a base unit incorporates a substantially `C` shaped magnetic core surrounded by its respective coil. A portable detachable device, such as an electric toothbrush, incorporates a substantially linear shaped magnetic core surrounded by its coil. The linear shaped magnetic core and the portable device are configured to fit within a gap formed in the `C` shaped magnetic core forming a substantially closed magnetic circuit thereby. Stray magnetic fluxes are thus significantly reduced. Additionally, an apparatus deactivates the power to the coil in the base unit when the portable device is removed from the base unit or when the battery within the portable device is charged to a predetermined level.

Abstract: An electronic measuring instrument measures and records power disturbances and other power parameters on an alternating current system. The instrument incorporates a speech synthesis subsystem, coupled to a telephone system, which is capable of providing a spoken report describing power disturbances and other power parameters. The telephone coupling system incorporates a structure for sharing a telephone extension in a non-disruptive way.

Abstract: An electronic measuring instrument measures and records the acceleration frequency spectra of a multi-story building while it is excited by wind. Such frequency spectra are indicative, in part, of building structural stiffness. When a tramatic structural event occurs, such as an earthquake, an explosion, or a hurricane, changes in wind-excited frequency spectra are used to detect hidden structural damage to the building.

Abstract: In data logging applications, a method and apparatus are disclosed for storing an increasing number of consecutive real-time data points, such as those descriptive of AC (alternating current) power line parameters, in a fixed amount of memory by periodically applying a novel compression technique. The compression technique preserves time relationships in the data while maximizing the level of detail consistent with a limited amount of memory. When the memory is full each data point stored is paired with another data point and one value is calculated that will represent the pair of data points, reducing the necessary memory to half and allowing more data points to be stored.