Device for determining turn-to-turn short circuits in power transformer windings with switching without excitation
SUBSTANCE: device contains current transformers, included into the phase break of the power circuit of the three-phase network, connected to the electric plant. The transformers are interconnected in delta circuit on the sides of the electric plant, forming a differential protection circuit, current circuits and a differential relay with the first and second compensating and differential windings, located on the same core leg and interconnected. The polar terminals of current transformers of different phases and sides of the electric plant are connected to one differential relay. To determine the turn-to-turn short circuit in the windings of the auto-type transformer winding ends are provided. The winding ends have respective digital marking in the number of the changer taps without excitation of the power transformer and allow increasing or decreasing the transformation ratio of the auto-type transformer depending on the changer tap without excitation of the power transformer. The terminals are fitted with pads for changing the turns of the adjustable winding in the number of the transformer phases. Each pad is a metal plate of at least 2.5 mm in cross-section, attached with its one end to the terminal of the dielectric plate, and with the other end to one of the terminals of the adjustable winding of the auto-type transformer, located on the same dielectric plate. The pad is fixed on the terminals of the auto-type transformer.
EFFECT: increase in the sensitivity to turn-to-turn short circuits and elimination of the influence of higher harmonics.
2 cl, 1 dwg
FIELD: electrical engineering.
SUBSTANCE: proposed differential current transformer that can be used as component part of computer-based control systems and tripping devices responding to differential current for protection against electric shock, fire set up due to leakage current heat, overload and short-circuit currents has primary winding assembled of three three-phase mains conductors spaced 120 deg. apart. Secondary winding is assembled of sections. One plus p identically wound coils of first section are connected in series through equal angles. Each coil has n turns. Six identically wound coils, each having m turns, are paired, disposed in diametrical opposition, and integrated in three sections. Coils are differentially connected in each section. One of coils in each section is tightly fitted to respective conductor of primary winding.
EFFECT: provision for electric isolation of differential current signals proportional to leakage current and unbalance signal proportional to load.
4 cl, 3 dwg
SUBSTANCE: electrical machine is in the first state of the machine, the first reference value is determined for measured values of electrical quantity. Detection of ground short-circuit includes continuous measurement of electrical quantity in the winding and detection of ground short-circuit based on the measured values of electrical quantity and the first reference value. The method includes receipt of signal (101, 102), detection of the machine state changing based on the received signal (120) and changing to the second reference value for electrical machine when change in the machine state is detected, at that the second reference value differs from the first reference value (100).
EFFECT: improved accuracy of ground short circuit detection when working state of the machine changes.
9 cl, 3 dwg
SUBSTANCE: method for improvement of detection reliability of generator ground fault at rotating electrical machine comprises delivery of a test signal at the preset frequency to the winding, measurement of the electric parameter response to the signal in the winding, which is a result of the delivered test signal and detection of the ground fault on the basis of the measured electric parameter value. At that frequency of the response signal is defined continuously and the measured value corresponding to a certain frequency is cleared out when this frequency deviates from the preset frequency at the first threshold value.
EFFECT: higher reliability of detection.
10 cl, 3 dwg
SUBSTANCE: invention relates to electrical engineering and can be used for pinpointing failed states in induction windings of electrical machines. The invention concept is as follows: the device comprises a three-phase transformer with regulated voltage in the wye-connected secondary winding having three linear conductors, a known good inductive winding coupled by one output with the first linear conductor, a comparison circuit containing a capacitor and resistor with variable resistance values, which may be connected by one of its outputs to the second linear conductor and the second output of the known good winding and an ammeter connected to the third linear conductor. The device is designed for measurements by an ammeter in the circuit of the known good winding with disconnected comparison circuit and tested circuit; it is capable to measure current when the comparison circuit is connected by its one output to the second linear conductor and by its second output to the second output of the known good winding with potential current measurement when the tested winding is coupled in the third linear conductor circuit to the junction unit of the known good winding in series with the ammeter. Operating condition of the tested inductive winding is judged by the current value in the third linear conductor.
EFFECT: expanded operating performances.
SUBSTANCE: current is measured via two connected in series windings and capacitor having fixed capacitance upon their connection to the voltage sources of increased frequency. Measurement is performed upon any combination of windings. Further based on measurement results the conclusion is made on presence of turn-to-turn short circuits.
EFFECT: possibility of diagnostics of turn-to-turn failures at an early stage of development.
SUBSTANCE: suggested method to measure current losses and excitation current of power transformers in field conditions and device for its implementation are referred to electric engineering and may be used for calculation and justification of standards for process power losses during its transmission through electric mains. The device comprises a controlled power source to change voltage at one winding of the transformer when the second winding is open. In order to reach the claimed result a free-running asynchronous generator with excitation capacitors is used as the controlled power source. Output voltage of the generator is controlled stepwise within the limits of 70-110% of rated voltage by reswitching of adjustment capacitors at transition of commutation voltage through zero value. Reswitching is made by three-phase contactless electronic keys controlled through optically coupled inputs by a decoder and a multiposition switch.
EFFECT: improved accuracy for real excitation losses of the power transformer.
2 cl, 3 dwg, 1 tbl
SUBSTANCE: amplitudes of runout phase voltages and periods of oscillation of these voltages. These values are compared with the values recorded earlier for the serviceable electric motor. By the measured values falling outside the allowable range provisioned by an measurement errors and allowable deviation of measured parameters from initial values the occurrence of turn-to-turn failures can be witnessed.
EFFECT: diagnostics of turn-to-turn failures at an early stage of development.
SUBSTANCE: counter comprises sensors of current for network phases "A", "B", "C", a microcontroller, an ambient temperature sensor, a square-ware generator, a register, a digital indicator, the first and second transceivers, a permanent memory, a computer.
EFFECT: increased accuracy due to taking into account dependence of active resistance of transformer windings on heating temperature and taking into account variations of ambient temperature, expanded functional capabilities of a device due to possibility of accurate determination of wear of insulation of windings at non-symmetrical load of phases.
SUBSTANCE: device for inductive winding diagnostics includes three-phase transformer with adjustable voltage of secondary winding connected in delta pattern, with one winding output connected by serial conductor to auxiliary circuit including serial ammeter with capacitor of variable capacity, shunted by a switch, and to the first of three outputs of inductive winding, while second output of inductive winding is connected directly to second output of secondary winding of three-phase transformer.
EFFECT: simplified electric diagram with the same functional capabilities of device.
FIELD: test equipment.
SUBSTANCE: invention refers to winding tests for DC collector machine armatures. Substance of invention involves shock pulse excitation mode run simultaneously in all parallel winding paths of rotating armature by excitation voltage pulse transmission from pulse voltage generator with repetition rate of 50 pulses per second or the like to collector against the case. Winding turn isolation fault is registered by inductance sensor of astatic structure with ferromagnetic core with air clearance slot oriented along coil outputs near commutator lugs in sections with maximum test voltages between turns in the middle of each parallel winding path due to armature winding symmetry about excitation point, and by magnetic pulse field metre with electronic memory cell for maximum levels of magnetic pulse field measured by contact-free method involving inductance sensor with magnetic pulse field metre and registered when electronic memory cell is actuated in automatic test mode upon each passage of turn outputs of defective section and sections connected to it by equalisers under the inductance sensor; maximum levels of magnetic pulse field evolve only by current in turn-to-turn short circuit under effect of centrifugal force on winding and collector and of vibration on rotating armature only.
EFFECT: detection of winding turn isolation fault leading to turn-to-turn short circuit under effect of centrifugal force on winding and collector and of vibration on rotating armature only.
FIELD: measurement equipment.
SUBSTANCE: invention relates to electrical measurement equipment and is intended to determine the quality of compounding of electric machine windings at test stages of winding insulation at manufacture and operation, and namely of stator windings of oil-filled submerged asynchronous electric motors. Essence of the invention is as follows: constant voltage U is supplied to a measurement object and resistance R(t) of the object is measured during the period of time, which is sufficient to achieve the resistance value of the practically set value. Then, values of transient current i(t)=U/R(t) are determined. A diagnostic feature of quality assessment of the winding compounding is determined as per the current curve in the form of a product of experimental values of the main characteristics of compound (εa·ρv)exp - absolute dielectric permeability and specific volumetric resistance respectively; then, compounding quality criterion Kk is determined by comparing experimental characteristics of the compound to its nameplate data by the following formula:
EFFECT: improving objectiveness of quality assessment of winding compounding.
4 dwg, 4 tbl
FIELD: the invention refers to electrical measuring technique and may be used for definition of the groups of joining of the windings of a three-phase transformer.
SUBSTANCE: the arrangement has a source of constant voltage and a commutative member providing by turn switching of a source of constant voltage to the outputs AB, BC, AC of the winding of the high voltage of the transformer. Besides the arrangement has additionally a digital oscillograph having a computation block, an energy independent memory, a port of conjugation with a personal computer and three measuring channels of voltage which are connected with the outputs of the winding of the low voltage of the three-phase transformer. At that the commutative member has a starting block, protection circuits of inner keys from overvoltage, an expectation block of nulling currents in the winding of high voltage of the three-phase transformer and has an additional output connected to an additional controlling input of the digital oscillograph.
EFFECT: possibility to automatically define the group of joining of the windings of the three-phase transformer, to operatively store in electronics shape the data of measurements and to document in the personal computer the data of definition of the group of joining of windings.
FIELD: electrical engineering.
SUBSTANCE: proposed device has three common-output voltage channels and three current channels. It is also provided with electrically isolated current sensors, switching surge protective circuits, electrically isolated current sensors in three current channels, analog-to-digital converter, computing unit that functions to measure dc current through star-connected grounded-neutral three-phase power transformer windings, nonvolatile memory designed to save measurement data and to transfer them to personal computer whenever necessary including organization of database and archive, liquid-crystal display, and personal computer interface port. Device is also provided with two four-conductor cables designed to connect its components to piece of equipment under measurement.
EFFECT: enhanced measurement accuracy and provision for saving measurement data in computer volatile memory.
3 cl, 2 dwg, 1 tbl
FIELD: power engineering.
SUBSTANCE: device can be used for testing power transformers during start-setting-up works as well as for complex inspection of power transformers. Device has adjusted ac voltage source provided with control input, commutating body having control input, and multi-vector meter with additional control output. Device also has analog-to-digital unit, energy-independent memory unit, computational unit, liquid crystal display, port for communication with computer. Circuit of the device is also provided with three-wire cable which connects terminals of commutating unit with object to be measured. Device simplifies process of measurement, eliminates affect of components of current and voltage of multiple frequencies of main harmonic. Readings of current, voltage, frequency and power of open-circuit loss are fixed simultaneously to exclude affect of error of measuring circuit's losses (connecting wires and so on). Data of measurement are kept in electronic form in energy-independent memory of the device; the data can be sent to personal computer for making database and for keeping them in archive.
EFFECT: improved precision; improved efficiency.
4 cl, 2 dwg