A method for detecting radial deformation in a winding of a transformer may include synthetic aperture radar (SAR) imaging of the winding using ultra high frequency (UHF) electromagnetic signals in a first instance of the winding to obtain a first image of the winding; SAR imaging of the winding using UHF electromagnetic signals in a second instance of the winding to obtain a second image of the winding; and comparing the first image of the winding and the second image of the winding to detect a radial deformation in the winding. The UHF electromagnetic signals may be transmitted as a plurality of successive sinusoidal signals, where frequencies of the successive sinusoidal signals gradually change from a first frequency to a second frequency.

This invention provides two methods for detecting mechanical or electrical faults in a solenoid valve. In the first method, a force sensor is placed in the valve in such a way as to detect changes in the impact force of the plunger against the solenoid valve body or coil housing (depending upon the direction of movement of the plunger upon application of the electric current/magnetic field). A second method is provided which makes use of an accelerometer placed in such a way as to detect changes in the response of the plunger to the application of the magnetic field.

A method of testing a solenoid of a directional control valve in a subsea hydrocarbon production system, the solenoid having a coil and an armature for operating the valve and the coil being energized by a drive voltage across it, the method comprises removing or reducing the drive voltage and sensing current through the coil to produce an indication of movement of the armature.

A transformer test device (10) for testing a transformer (40) has connections (12) for releasably connecting the transformer test device (10) to the transformer (40). The transformer test device (10) has a source (13) for generating a test signal for testing the transformer (40). The transformer test device (10) has a controllable switching means (15) which is connected to the connections (12) during a transformer test for the purpose of short-circuiting at least one winding (42) of the transformer (40).

A method and an apparatus check a multiplicity of mutually insulated strands in a stator winding bar of an electric machine. The method includes injecting a test signal, determining a first component of the test signal, and comparing at least the first component with a reference signal in order to determine damage to insulation between individual strands of the multiplicity of strands. The apparatus includes a signal source and a measuring apparatus. The method and the apparatus are particularly suitable for checking stator winding bars as are used in a generator and/or an electric motor.

An apparatus for detecting leakage current through a solenoid coil that includes a capacitor connected to one end of the solenoid coil and a feedback circuit that monitors the rate of decay of the capacitor voltage to determine if an excessive leakage current is present.

The subject matter of this specification can be embodied in, among other things, a method that includes evaluating an analog electrical current waveform, determining a Boolean waveform based on the evaluated analog electrical current waveform, determining a collection of one or more first durations based on one or more on times identified from the Boolean waveform, determining a collection of one or more second durations based on one or more off times identified from the Boolean waveform, comparing the first durations and the second durations, determining, based on the comparing, an event based on the comparing, identifying a time at which the event occurred, and providing the time as a completion time.

Embodiments of the disclosure relate to detecting turn-to-turn faults in one or more windings of various objects. In one implementation, a fault detector uses a differential protection algorithm to detect a turn-to-turn fault in a winding of a three-phase shunt reactor. Various voltage and current measurements carried out upon the three-phase shunt reactor are used to calculate a difference value between a voltage-based parameter and a current-based parameter. The voltage-based parameter is indicative of a normalized negative voltage imbalance and the current-based parameter is indicative of a normalized negative current imbalance. A turn-to-turn winding fault is declared when the difference value is not equal to zero.

A device for testing a solenoid valve includes: a voltage generator for applying a short pulse of voltage, which is not long enough to open the solenoid valve, to the windings of the solenoid valve; a current meter configured for measuring the current flowing through the windings of the solenoid valve; and an analysis device which is configured for analysing the current measured by the current meter for detecting a potential fault of the solenoid valve.

A method for detecting an open-phase condition of a transformer having a grounded-wye high voltage side connection including monitoring current flowing in a neutral connection on the high voltage side of the transformer in real time by voltage relaying and current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude. A current signal may be injected onto the neutral terminal and the zero-sequence mode of the transformer monitored to detect an open-phase condition indicated by an increase in network impedance and decrease or elimination of the injection current.