JP2623885B2 - Partial discharge detection device for resin mold transformer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preventive maintenance device for a resin-molded transformer widely used for high-voltage power reception, which is generated inside a primary winding on a high-voltage side. The present invention relates to a partial discharge detection device for detecting a partial discharge to be performed with high sensitivity.

[Conventional technology]

FIG. 5 is a front view showing an example of a three-phase resin mold transformer, and FIG. 6 is a schematic configuration diagram of a conventional partial discharge detection circuit including a cross-sectional view of a resin mold winding. In the figure, a three-layer resin mold transformer 1 has a U-phase, V
Phase, W-phase high-voltage windings 3U, 3V, 3W, etc., and low-voltage windings 9 wound inside the windings.
By being sandwiched between the pair of frames 19 through
The high-voltage winding 3 and the low-voltage winding 9 are resin-molded so as to be concentric with each other while maintaining the main insulation gap length G therebetween, and to maintain the gap length g between the low-voltage winding 9 and the iron core. The transformer 1 is configured.

The high-voltage winding 3 is formed by stacking a plurality of unit coils 11 in which foil conductors of a fixed width are overlapped and wound in the axial direction at intervals from one another, and connecting the unit coils 11 in series by a lead 11A. Are integrally resin-molded in an epoxy resin-based resin mold layer to form a high-pressure resin molded winding 3. Both winding ends are embedded leads 13
3 and 3 are connected to each other in the inter-phase connection lead 4 which is drawn out to the embedded metal fitting by resin and molded by resin, and the inter-phase connection lead 4 is provided with high voltage terminals 5U, 5V, 5W and the like 5. Further, among the unit coils 11 indicated by unit coil numbers u1, u2... U11, u12, etc., u6 and u7 located adjacent to each other at the center thereof are configured as tapped coils and drawn out from each tap. The buried tap leads 16 and 17 are conductively connected to the buried tap terminals 6 and 7, and one of the tap terminals 6 and 7 is conductively connected by a connection conductor 8, so that primary and secondary windings are formed. A high-voltage winding 3 with a no-load switching tap capable of switching the turn ratio between the no-load states is obtained.

As shown in FIG. 6, the measurement of the partial discharge of the resin mold transformer configured as described above is performed by connecting the coupling capacitor 22 to the high-voltage terminal 5 and connecting the partial discharge detection sensor (hereinafter abbreviated as a sensor) to the ground end thereof. To connect 21 and coupling capacitor
The sensor 21 detects a discharge pulse included in the charging current 22 as a voltage pulse or a current pulse. The detection pulse is amplified to a predetermined level by the amplifier 23,
24 measures the magnitude of the pulse (discharge charge), the frequency of occurrence of the pulse, and the like. As the sensor 21, a detection impedance such as resistance, capacitance, or inductance is used to detect a voltage pulse, and a high-frequency AC device is used to detect a current pulse.
As a measuring instrument, a dedicated measuring instrument such as a waveform observing device having a built-in amplifier such as an oscilloscope or a partial discharge measuring device is used. Further, a calibration pulse generator 25 composed of a square wave pulse generator and a series capacitor is used to calibrate the detection sensitivity of the partial discharge, and this is connected between the high voltage terminal 5 and the ground to inject a known discharge charge. By measuring the magnitude of the pulse appearing on the measuring device 24, the amount of discharged electric charge can be known (for example, see the Institute of Electrical Engineers of Japan, the Standards Committee, JEC-204).

[Problems to be solved by the invention]

The high voltage winding 3 of the resin mold transformer is a unit coil
The 11 series-connected bodies and the embedded leads 13, 14, 16, 17 and the like are poilessly cast by a vacuum method or a pressure impregnation method of epoxy resin, and are integrally molded into a completely heat-cured resin mold layer 12. Insulation design is performed with the goal that no partial discharge occurs at the operating voltage (referred to as corona-free). Therefore, in a partial discharge test that verifies whether or not it is corona-free as designed, the detection sensitivity of the partial discharge is required to be as high as possible, but the detection sensitivity is limited by the influence of external noise. In general, the detection sensitivity is set to 50 PC.

On the other hand, the partial discharge caused by the voltage induced in the high-voltage winding 3 is caused by the external corona generated in the external air due to the surface of the resin mold layer 12 being contaminated with moisture or salt, and the internal Internal discharges (called void coronas). Since the high-voltage winding 3 is surrounded by a large air gap (for example, main insulation gap length G), the electric field in the resin mold layer 12 is generally low, and the void corona is directed toward the grounded object similarly to the external corona. Is unlikely to occur. On the other hand, since a plurality of embedded tap leads 16 and 17 are drawn out from between the tap coils u6 and u7, for example, the insulation distance between the embedded lead 16 and the tap coil u7 is locally reduced. Part occurs. On the other hand, the high voltage winding 3
Is composed of twelve unit coils 11 of u1 to u12 directly connected, and depending on the tap coils u6 and u7 and the tap position, a voltage of at most one unit coil is applied to each. You. Therefore, between the embedded lead 16 connected to the tap coil u6 and the tap coil u7, a voltage corresponding to one unit coil is applied at the maximum depending on the tap position. As described above, since the voltage corresponding to one unit coil is applied to a portion where the insulation distance between the embedded lead 16 and the tap coil u7 is locally reduced, the insulation distance is locally reduced. The portion has a higher electric field than others, and void corona due to residual bubbles and the like is likely to occur. Further, in the case where the voltage is applied to the inter-phase connection lead 4 through the side of the plurality of unit coils 11 as in the case of the extraction lead 13, a void corona is generated between the unit coil and the unit coil because the voltage corresponding to the plurality of unit coils is applied. More likely to occur. In particular, when void corona is generated in such a portion, there is a risk that the insulation may be eroded by corona discharge, and eventually the unit coil may be short-circuited through the lead. For this reason, in a resin-molded transformer with a no-load switching tap, it is important for the partial discharge detection device to detect the void corona generated near the tap coil located near the center of the winding with high sensitivity. Will be an issue.

By the way, in the conventional detection device in which the sensor 21 is connected between the high-voltage terminal 5 of the high-voltage winding 3 and the ground via the coupling capacitor 22, the detection is performed from the surface of the resin mold layer to the earth potential portion such as the iron core or the low-voltage winding. Since the pulse current of the external corona generated by the current flows through the entire winding and the series circuit of the coupling capacitor 22 and the sensor 21, it can be detected with high sensitivity by the sensor 21,
Since the discharge pulse current of the void corona generated between the unit coil and the embedded lead flows back in a series circuit formed by the capacitance between the unit coils, the sensor 21
Almost no reflux.

As described above, in the conventional method, since the discharge pulse current flowing back to the sensor 21 becomes small for the void corona, not only a high detection sensitivity cannot be expected, but also the influence of extraneous noise is high. There is a problem that becomes more difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a partial discharge detection device capable of obtaining a particularly high detection sensitivity with respect to a void corona which is likely to be caused by an extremely high shared voltage between an embedded lead and a unit coil. is there.

[Means for solving the problem]

According to the present invention, there is provided a resin molded transformer having a no-load switching type tap terminal on a high voltage winding side, wherein a partial discharge detection sensor is connected between the tap terminals. An E / O conversion unit that converts an output signal of the partial discharge detection sensor into an optical signal as necessary,
An optical fiber that transmits an optical signal output from the E / O converter, and an O / E converter that converts the optical signal transmitted by the optical fiber into an electric signal and outputs the electric signal to an indicator. I do.

[Action]

According to the structure of the present invention, the partial discharge detection sensor is connected between the tap terminals of the high voltage winding, and the partial discharge detection sensor is provided in a state of being floated at a high potential. Since a pulse circuit composed of a detection sensor can be formed, void corona generated in the vicinity of the tap coil can be detected with particularly high detection sensitivity, and a part of the discharge pulse generated in a portion far from the tap coil is also included. Pass through the detection circuit, the detection can be performed without significantly lowering the detection sensitivity than the conventional method. Also, if an optical transmission line is provided on the output side of the amplifier circuit, the indicator can be placed on the ground potential side, and therefore, the influence of external noise does not float on the indicator located at a remote place. It becomes possible to transmit a signal.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

FIG. 1 is a configuration diagram showing a partial discharge detection device for a resin mold transformer according to an embodiment of the present invention, together with a sectional view of the resin mold transformer. FIG. 2 is a connection diagram of a detection circuit in the embodiment. Transformers are given the same reference numbers as in prior art devices. In the figure, the partial discharge detection device
Reference numeral 33 denotes a series circuit of the sensor 31 and the coupling capacitor 32 connected between the no-load switching tap terminals 6 and 7 of the high-voltage winding 3, a detection pulse amplifying circuit 33 of the sensor 31, and a magnitude of the amplified signal. It is constituted by an indicator 34 for displaying and is connected between the tap terminals of the high voltage winding 3 which is a high potential portion with respect to the ground potential. Therefore, a battery driven type amplifier and indicator are used. The partial discharge detection sensor 31
Any of a voltage pulse detection type and a current pulse detection type may be used. Further, the amplifier circuit 33 is a narrow band amplifier having a center frequency in a specific frequency region and is configured to reduce external noise.
It may be configured to increase the S / N ratio. In addition, indicator 34
May use either a peak value indicator or an average current indicator.

Next, the calibration result of the detection sensitivity of the partial discharge detection device according to the embodiment will be described with reference to the connection diagram of FIG. As a resin molded transformer, a three-phase transformer having a primary rated voltage of 6300 V and a secondary rated voltage of 420 V is used, and full taps 6 a and 7 a of a triangularly connected W-phase high-voltage winding are connected by a connection conductor 8 and a tap terminal 6 b , A series connection of a coupling capacitor 32 having a capacitance of 750 PF and a high-frequency current device 31 as a sensor is connected between the high-voltage terminal 5 and an arbitrary tap terminal.
(See FIG. 6), a known calibration charge Q (PC) is injected, the indicator 34 obtains a calibration charge Q indicating a 0.1 V pulse voltage, and the calibration charge Q in the prior art shown in FIG. Compared to Q. The calibration of the detection sensitivity of the partial discharge detection device itself was performed by injecting a calibration charge into the sensor 21 or 31, and it was confirmed that the indicator showed a 0.1 V pulse output when Q = 4 PC was injected. .

In the circuit configured as described above, when the calibration charge is first injected between the tap terminals 6C and 7C, the circuit of the embodiment shown in FIG. In the conventional circuit shown in FIG. 6, a pulse output of 0.1 V was displayed when Q = 45 PC was injected. The charge injection between the tap terminals 7b and 7c was 26PC for the former and 90PC for the latter. Further, in the charge injection between 6a and 6c, the former is 55PC,
The latter was 180PC. According to the calibration results by the charge injection between the tap terminals, the detection sensitivity of the void corona of the detection device according to the embodiment is several times higher than that of the conventional device, and is required in the partial discharge test of the resin mold transformer. It was proved that a detection sensitivity sufficiently satisfying 50PC was obtained.

In the circuit of FIG. 2, the detection sensitivity when the calibration charge is injected between the high-voltage terminals 5U, 5V, and 5W of each phase and the ground is 10 to 35 PCs, which is slightly higher than that of the conventional circuit of 5 to 25 PCs. Although it decreased, it became clear that the required sensitivity of 50PC could be sufficiently cleared.

In the above description, the connection conductor 8 is connected to the tap terminal 6a.
Although the case where the connection conductor 8 is connected to each of the plurality of tap terminals 6 and 7 is shown in FIG.
It is selected according to the receiving voltage and the load condition, and tap switching is performed when there is no voltage.

FIG. 7 is a partially enlarged view showing an arrangement of tap terminals in the embodiment of the present invention. For example, when the tap terminals 6a, 6b, 6c, 7a, 7b, 7c in FIG. 2 are arranged as shown in FIG.
Is connected to either 6a and 7a, 6b and 7a, 6b and 7b, 6c and 7b, or 6c and 7c.

Next, it is not uniquely determined which of the plurality of tap terminals 6, 7 is connected to the series body of the coupling capacitor 32 and the high-frequency current transformer 31, that is, the sensor unit of the partial discharge detection device. However, in a state where one of the tap terminals 6 and one of the tap terminals 7 are connected by the connection conductor 8, the tap terminal 6, which can obtain the highest detection sensitivity, can be obtained.
It is practical to select 7 combinations and connect the sensor section of the partial discharge detection device to these terminals.

For example, in the arrangement of the tap terminals 6 and 7 as shown in FIG. 7, when the tap terminals 6a and 7a are connected by the connection conductor 8, the combination of the tap terminals connecting the sensor unit is 6b. There are four types: 7a, 6b and 7b, 6c and 7b, and 6c and 7c. In addition to the above four combinations, for example,
Although the sensor unit can be connected to 6b and 7c, the distance between the terminals is larger than the above four types, so that the structure of the terminal connection unit of the sensor unit cannot be shared, Not practical.

When the tap terminals 6c and 7c are connected by the connection conductor 8, the combination of the tap terminals for connecting the sensor unit is 6a.
And 7a, 6b and 7a, 6b and 7b, and 6c and 7b.

FIG. 3 is a schematic configuration diagram of a partial discharge detection device according to a different embodiment of the present invention. For example, the above-described embodiment is formed as a single resin molding together with the connection conductor 8 and integrally molded with the connection conductor 8 so that the primary conductor 8 and the secondary coil are insulated by the resin molding layer so as to sufficiently withstand the ground voltage of the tap coil. Unlike the example, the coupling capacitor 32 becomes unnecessary, and the amplifier circuit and the indicator can be placed on the ground potential side, so that the configuration of the detection device can be simplified and the measurement work of the partial discharge can be simplified. Benefits are obtained. As for the different examples, the detection sensitivity was calibrated by charge injection, and as a result, a detection sensitivity almost equivalent to that of the above-described examples was obtained.

In the embodiment of FIG. 3, the tap terminals 6,
7 are arranged as shown in FIG. 7, for example, at the time of tap switching, the connection conductors 8 are connected to 6a and 7a, 6b and 7a and 6b.
7b, 6c and 7b, or 6c and 7c.

On the other hand, since the partial discharge detection sensor 40 is formed integrally with the connection conductor 8, it is necessarily disposed between the same tap terminals 6, 7 to which the connection conductor 8 is connected.

FIG. 4 is a schematic configuration diagram of a partial discharge detection device according to another embodiment of the present invention, in which a coupling capacitor 32 and a sensor 31 connected between tap terminals 6 and 7 and an amplification of a detection pulse signal of the sensor 31 are shown. An optical fiber 53 is connected to a high-potential portion composed of the circuit 33 via an E / O converter 52 that converts an output signal of the amplifier circuit 33 into an optical signal, and a discharge pulse transmitted to the ground potential side by the optical fiber 53. Is converted into an electric pulse by the O / E conversion unit 54, and the magnitude is displayed on the indicator 34. Note that the sensor 31 may use either a detection impedance or a frequency current transformer, or may be configured to attach a high-frequency current transformer to the connection conductor as shown in FIG.

In the partial discharge detection device configured as described above, the power supply of the amplifier circuit and the E / O converter arranged in the high potential section may be a battery, and the tap voltage may be supplied from the mold transformer side. It can simplify the configuration of the high-potential section, and can transmit the detection signal through optical fiber to a remote location without being affected by external noise. The possible benefits are obtained.

〔The invention's effect〕

As described above, the present invention is configured such that a partial discharge detection sensor is provided between the no-load switching taps of the resin-molded transformer high-voltage side winding to amplify the detection signal and display the magnitude of the discharge pulse on the indicator. did. As a result, the electric field between the unit coil and the embedded lead locally becomes higher than in the conventional detection device in which the coupling capacitor and the detection sensor are connected between the high voltage terminal and the ground. With high detection sensitivity, it is possible to detect void corona of 50PC or less, which is especially required for resin mold transformers, with excellent S /
It is possible to provide a partial discharge detection device capable of detecting while maintaining the N ratio. Further, by combining the optical fiber transmission line, the detection pulse can be transmitted to a monitoring place separated from the external noise without being bothered by external noise, so that an advantage that the internal partial discharge of the resin mold transformer can be monitored online.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a partial discharge detection device of a resin mold transformer according to an embodiment of the present invention together with a cross-sectional view of the resin mold transformer, FIG. 2 is a connection diagram of a detection circuit in the embodiment, and FIG. FIG. 4 is a schematic diagram showing a partial discharge detecting device according to another embodiment of the present invention, FIG. 4 is a schematic structural diagram showing another embodiment of the present invention, FIG. 5 is a front view showing an example of a resin mold transformer, and FIG. FIG. 1 is a schematic configuration diagram of a conventional partial discharge detection circuit including a cross-sectional view of a resin mold transformer, and FIG. 7 is a partially enlarged view showing an arrangement of tap terminals in an embodiment of the present invention. 1 ... resin molded transformer, 2 ... iron core, 3 ... high voltage winding, 3U, 3V, 3W ... each phase high voltage winding, 5U, 5V, 5W, 5 ... high voltage terminal, 6, 7 ... Tap terminal, 8 connection conductor, 9 low-voltage winding, 11 unit coil, 12 resin mold layer,
_{u 1, u 2 ... u 12} ......... unit coil number, u6, u7 ...... tap coil, 16 and 17 ...... buried tap lead, 21,31,40 ......
Partial discharge detection sensor, 22, 32 …… Coupling capacitor, 23, 33
…… Amplifier circuit, 24,34… Indicator (measurement device), 25… Calibration pulse generator, 30… Partial discharge detection device.

Claims (2)

(57) [Claims] 1. A partial discharge detection of a resin mold transformer, wherein a partial discharge detection sensor is connected between the tap terminals in a resin mold transformer having a no-load switching type tap terminal on a high voltage winding side. apparatus. 2. An E / O converter for converting an output signal of the partial discharge detection sensor into an optical signal, an optical fiber for transmitting an optical signal output from the E / O converter, and an optical signal transmitted by the optical fiber. O / that converts it to an electrical signal and outputs it to the indicator
2. The partial discharge detection device for a resin mold transformer according to claim 1, further comprising an E converter.