RU2659194C2 - Device for testing inter-winding and body insulation in windings of rotors of turbogenerators - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measuring equipment. Gist: the device contains a pulse generator loaded on the input winding of the transformer, output windings of which are connected to the windings of the rotor poles and to the series-connected resistors of the voltage divider. Middle point of the output windings, the rotor body and the input of the non-inverting amplifier are grounded, and the inverting input of the amplifier is connected to the midpoint of the voltage divider. Control output of the pulse generator is connected to the third input of the measuring unit. Signals from the outputs of the first and second comparators are fed to the first and second inputs of the measuring unit, respectively. Inputs of the comparators are connected to the output of the amplifier. Reference inputs of the first and second comparators have voltage levels of the upper and lower thresholds, respectively. Outputs of the first and second comparators are connected to the body indicator and the indicator of the inter-winding fault, respectively. Output of the measuring unit is connected to the block of indication of the short-circuit location.EFFECT: technical result: higher sensitivity of the insulation short-circuit detection between the turns of winding and winding on the rotor case of turbogenerators with the bandages fixed or when the rotor is rotated.1 cl, 3 dwg

Description

The invention relates to measuring equipment, in particular to devices for monitoring winding and housing short circuits in the windings of the rotors of turbine generators.

The aim of the invention is to increase the sensitivity and simplification of the method for determining the insulation circuit between winding and winding turns on the rotor case of turbo-generators with fitted tires in a stationary state or when the rotor rotates.

The idea of a “traveling wave” was proposed as far back as the invention (A.S. USSR 82724, declared 03/11/1948 for No. 378531, published on 05.31.49), when a short pulse from the generator is sent to two test windings connected in series, and two consecutive resistors with a grounded midpoint, and from the common point of the coils relative to the grounding point, the voltage is applied to the oscilloscope and the shape of the coil circuit is judged by the shape of the curve on the oscilloscope screen. The main drawback is the complexity of control due to the need for a visual assessment of the shape of the curve.

In the invention (A.S. USSR 82901, 30 07.1949 for No. 402023 was announced to the State Technical University of the USSR) short impulses from the generator are sent to the two test windings alternately. On the oscilloscope screen, both oscillograms are superimposed on each other. If there is no ect, then there is one curve, and if there is, then two, which have a common beginning.

On the basis of this method, developed devices EL-1 and EL-15.

In the method (A.S. USSR 136455, declared on July 3, 1959 No. 632634/24 to the Committee for Inventions and Discoveries at the Council of Ministers of the USSR, published in the Bulletin of Inventions No. 5, 1961), the idea of a traveling wave Refined to search for insulation closures on the case or between the turns of the turbine rotor coils. The disadvantage is the need to visually evaluate the curves on the oscilloscope screen by comparing with the calibration curves.

The idea of a "traveling wave" is implemented in the IU-57 installation (A. P. Zelenchenko. Diagnostic devices for traction motors of electric rolling stock. Study Guide, Moscow, 2002, p. 14).

In this setup, a voltage pulse is applied to the two test coils, and the shape of the curve is observed on the oscilloscope screen.

Significant changes in the way vz controls in this setting, as in the methods used in the EL-1, EL-15 devices, compared to the above inventions, no.

Especially for checking the rotors of turbogenerators, the company Kharkovenergoremont developed the device IKZ-2 (1975) and the device IKZ-3 (1979). The IKZ-3 devices were operated for a long time at the Electrotyazhmash plant in Kharkiv.

Closest to the claimed device is a device for detecting short circuits between coils and between the coil and the winding case of the rotors of the turbogenerators TGV50, TGV200, TGV300, TGV500 with wearing retaining rings (Short circuit indicator type IKZ-3 UHL 4.2. Passport A210.00.00PS) .

In this device, a voltage is applied from the pulse generator to the transformer and to the input of the horizontal scanning unit of the cathode ray tube. From the two output windings of the transformer, the voltage flows to the windings of the two poles of the tested rotor, and the rotor case is grounded. The midpoint of the output windings of the transformer is also grounded.

The resistive divider is connected to the output windings of the transformer, its midpoint is to the inverting input of the amplifier, and the non-inverting input is connected to ground.

At the output of the amplifier, a differential signal of two voltage waves is formed, which is then fed to the vertical plates of the cathode ray tube.

If both windings are symmetrical (no closures), then the difference signal, close to zero, and on the screen of the tube is a straight line.

If there is a closure in any winding, then a reflection occurs from the location of the closure to the winding input and a differential signal pulse is generated. The distance from the moment of the pulse to the arrival of the reflected pulse on the screen of the tube determines the location of the circuit.

Performing in advance the artificial closure of one turn and the closure of the pole coil to the body, we obtain the calibration curves. A set of calibration curves is required for each type of rotor and separately for loop closures and short circuits to the body.

The disadvantage is the complexity of the control due to the need for a visual assessment of the shape of the curve. In addition, through a wide range of time from the moment of applying a pulse to the arrival of a reflected pulse from the circuit (time interval) - from 2 to 80 μs with a possible difference of 1 μs between some reflected pulses in adjacent coils, the waveforms of these pulses are difficult to see, which reduces instrument sensitivity.

The basis of the invention is the task of simplifying the method of determining the location of the circuit by eliminating the visual assessment and increasing the sensitivity by increasing the resolution in the evaluation of reflective pulses.

The task is solved by the fact that in the device for testing the coil and cabinet insulation in the windings of the rotors of turbogenerators containing a pulse generator loaded on the input winding of the transformer, the output windings of which are connected to the windings of the rotor poles and the series-connected resistors of the voltage divider, the midpoint of the output windings the rotor housing and the non-inverting input of the amplifier are grounded, and the inverting input of the amplifier is connected to the midpoint of a voltage divider, according to the invention, The output from the pulse generator is connected to the third input of the measuring unit, and the first and second inputs of the measuring unit are output from the output of the first and second comparators, respectively, the inputs of the comparators are connected to the output of the amplifier, the reference inputs of the first and second comparators have voltage levels of the upper and lower thresholds respectively, moreover, the outputs of the first and second comparators are connected to the indicator of the housing and indicator of turn-through closures, respectively, the output of the measuring unit is connected to the unit ohm indication of the location of the circuit.

The calibration of the device is as follows.

Performing in advance an artificial closure of one turn and a closure to the case for each pole coil, we obtain a list of time intervals for each rotor for closure of the coil, and for closure to the case. In the prototype, it is necessary to obtain a set of calibration curves.

Simplification of the method of determining the location of the circuit is provided by replacing the visual assessment of the shape of the curve on the readout of the indication of the block indicating the location of the circuit in digital form.

The increase in sensitivity is ensured by the fact that the accuracy of the digital indicator of the block of indication of the location of the circuit can be provided with a resolution of less than 1 μs, which makes it possible to distinguish the reflecting pulses with the minimum possible difference in the intervals of the pulses.

The inventive device is illustrated by the following graphics.

FIG. 1 is a device diagram, where:

1 - pulse generator

2 - transformer

3, 4 - winding rotor poles

5, 6 - voltage divider resistors

7 - power amplifier

8 - the first comparator

9 - case closure indicator

10 - second comparator

11 - indicator of short circuit

12 - measuring unit

13 - block indication of the location of the circuit

14 - upper threshold voltage

15 - lower threshold voltage

FIG. 2 - stress diagrams, where:

16 - generator control output

17 - amplifier output at case coil circuit closure

18 - amplifier output at VZ. in coil

19 - upper threshold

20 - lower threshold

21 - output from the first or second comparator in case of case closure in the coil

22 - output from the first or second comparator in the absence of closures

23 - output from the first or second comparator at i.e. in coil

24, 26 - time interval at case closure in the first and last coils, respectively

25, 27 - the time interval at v.z. in the first and last coil, respectively

FIG. 3 is an example of the practical implementation of the measuring unit, where:

28 - generator

29 - electronic key

30 - counter

31 - logical element 3I

32 - R-S trigger

33 - delay element

The generator 1 supplies a pulse voltage to the input winding of the transformer 2, from which two anti-phase voltages relative to zero are applied to the windings of the two poles 3 and 4 of the rotor. The rotor housing is connected to the zero point.

Two identical resistors of divider 5 and 6 are also connected to the output windings of the transformer. The common point of these resistors is connected to the inverting input of the amplifier 7, and its non-inverting input has zero potential.

The voltage difference from the output of the amplifier 7 through the first comparator 8 (upper threshold) is fed to the indicator of body short circuits 9 and simultaneously through the second comparator 10 (lower threshold) - to the indicator c.h. eleven.

The first, second and third inputs of the measuring unit 12 receives signals from the output of the first comparator, the second comparator and the generator control output, respectively.

The output code from the output of the measuring unit is connected to the block of indication of the location of the circuit 13.

The device works as follows.

The generator 1 generates short voltage pulses that arrive at the input winding of the transformer and at the same time the control output from the generator (pulses 16) starts the measuring unit 12 to the start of time.

The error signal from the output of the amplifier 17, 18 is checked by level 19 by the first comparator 8, and by level 20 by the second comparator 10. Since the amplitude of the inconsistency impulse when shorting to the body is an order of magnitude greater than at high speeds, it is easy to separate them from friend. From the outputs of the comparators, they will look like 21 or 23.

If not. and short circuits to the housing, then the outputs of the comparators will be zero voltage 22.

Both outputs of the comparators are connected to the inputs of the measuring unit 12 to stop the timing. The size of the deducted time (time interval) in FIG. 2 is conventionally shown by the number of pulses 24, 25, 26, 27. When there is a cabinet short in the first coil of the pole, the pulse 17 reflected from the point of short is fed to the input of the amplifier 7 at a time interval of 24, and if it is in the last coil of the pole, then through the time interval of 26. Similarly, at vz. in the first and last pole coils, the time intervals will be respectively 25 and 27.

Experimental studies have shown that time intervals 24 and 25 are close to each other, as well as time intervals 26 and 27. Moreover, depending on the location of the circuit in the coil (coil number), the reflecting pulse from the body circuit 17 can outpace the reflection pulse from the e. 18 (as shown in FIG. 2), and vice versa.

Therefore, if a case and a coil circuit occur simultaneously in any pole (indicators 9 and 11 are lit), the device records the time interval from the first leading pulse, and if it is in one pole coil, the device identifies these two closures indicating location of the circuit, and if the second circuit in another coil, the device will show the first circuit (which is ahead), and the second circuit will be detected after the removal of the first. But cases with multiple closures in one pole are rare.

To completely test the rotor, it is necessary to check poles 3 and 4 alternately. To do this, you need to connect the leads from the device (in Fig. 1 to the wires from the transformer output) to the rotor rings (to poles 3 and 4) with one polarity - check one pole, and then change wires in places - the other pole is checked. A similar procedure is performed in the prototype.

The amplifier 7 may have at the output a negative pulse indication circuit. Then the glow of this indication indicates the presence of closures in the other pole and you need to change the polarity of the connection, and if it is not lit, then the first connection is enough.

FIG. 3 shows an example of the practical implementation of the measuring unit on discrete elements.

To the input of counter 30, the counting pulses from the generator 28 are received with the electronic key 29 closed. This key is controlled by the RS trigger 32. When the control pulse from the generator 1 arrives at the S input of the trigger, the trigger switches and opens the electronic key - the counter starts counting the pulses from the generator 28

When the output of the first comparator 8, or the output of the second comparator 10, or the overflow signal P from the counter output receives a signal, the trigger closes the electronic key and the counting stops.

The overflow signal P from the output of the counter is generated if the time interval exceeds the maximum possible value, for example, if there are no short circuits in the coils. In this case, besides stopping the counting, this signal goes through the delay element 33 to the reset input R of the counter and the latter is reset.

The counter counts the number of pulses from the generator, which is proportional to the time interval, and converts them into an output code, for example, seven-segment (depending on the model of the counter chip) for outputting the result to a seven-segment indicator of the circuit of the location of the circuit.

The generator 28 can be performed on the logical elements of any of the known schemes. If the generator frequency is 10 MHz, then the period will be 0.1 μs and the device resolution will be 0.1 μs. If the maximum interval does not exceed 80 µs, then the counter will be executed on three chips of decimal counter-dividers, and the indicator will contain three seven-segment indicators (the third is tenths of a microsecond).

If the device is developed on the basis of a microcontroller, then the measuring unit 12 is easy to implement programmatically without discrete elements. In this case, the algorithm of the program of operation of the measuring unit is performed on the basis of the algorithm of operation of the measuring unit on discrete elements, as shown in FIG. 3 and FIG. 2, or another possible method of measuring time intervals by software.

The generator 1 is performed by any known method, for example, on the basis of a charge-discharge storage capacitor circuit.

Transformer 2 - high frequency, for example, with a ferrite magnetic core.

Amplifier 7, comparators 8 and 10 can be performed on the microchips of the operational amplifiers.

Thus, the practical implementation of the device is possible using both discrete elements and on the basis of a microcontroller.

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