JPH048382Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a device for detecting insulation deterioration of a coil housed in an iron core of a rotating electric machine and having a low resistance corona shield layer on the outer surface. This type of insulation result detection device non-destructively and accurately insulates the coil at the location where insulation deterioration is most likely to progress, without removing the coil from the iron core and even while the rotating electric machine is operating. It is necessary that deterioration can be detected.

[Prior art and its problems]

Coil insulation of rotating electric machines, especially high-voltage rotating electric machines, is based on thermal effects such as continuous heat and thermal cycles, electrical effects such as surge voltage, or mechanical effects such as vibration and impact encountered during the operation of the rotating electric machine. Due to stress, the initially provided functions gradually decline, and when this exceeds a certain limit, so-called dielectric breakdown occurs. In recent years, plants have become larger and more sophisticated, as dielectric breakdown in this type of coil can cause significant damage from unexpected suspension of operation of rotating electric machines or even the suspension of operation of the plant itself. As part of preventive maintenance aimed at preventing the above-mentioned scandals and maintaining equipment in a reliable state, insulation diagnosis of the coils of rotating electric machines has become increasingly important.

Insulation resistance tests, dielectric loss tangent tests, alternating current tests, partial discharge tests, etc. are conducted as tests necessary for insulation diagnosis of the coils as described above, but in this case, the rotating electric machine is usually stopped temporarily, and the coils are While it is stored in the core slot,
Each of the above tests is conducted non-destructively using a test high-voltage power supply and various coil insulation property measuring instruments.

Furthermore, the so-called high-voltage coil 1 whose rated voltage is 6 kV or higher and which is the object of the above-mentioned insulation diagnosis mainly has an insulating layer 3 on the outer surface of the conductor 4 and a slot in the iron core 7 in which the coil 1 is housed, as shown in FIG. In order to prevent surface corona generated between the coil insulation layer 3 and the wall, a low resistance corona shield layer 2 is formed on the outer surface of the coil insulating layer 3, and the low resistance corona shield layer 2 is connected to the iron core through a semiconductor positive liner 6. It is electrically connected so that it has the same potential as that of 7. All the coils 1 stored in the slots of the iron core of a rotating electrical machine in the above state are divided into three groups, and each coil 1 of each group is connected in series, and the neutral point is connected to the neutral point as shown in FIG. 3, for example. A three-phase star connection with N is configured.

When performing the various tests described above on the three-phase star-shaped wiring, conventionally the neutral point N of the three-phase star-shaped wiring was disconnected from the ground, and the three-phase windings were tested all at once or each of the three phases were tested. Coil conductor 4 and iron core 7 for each phase winding
This is done by applying a voltage between.

On the other hand, the influence of the thermal, electrical, or mechanical factors on the deterioration of the coil insulation of rotating electric machines depends on the model,
Naturally, this varies depending on operating conditions and environmental conditions, but as mentioned above, thermal cycling is the main influence on the insulation deterioration of coils with a rated voltage of 6kV or more, especially long coils used in large electric machines. It is thought that a mechanical factor due to electromagnetic force is added to this. According to the results of experiments and analyzes conducted by the present inventor regarding the influence of thermal cycles in particular, when the coil 1 is not housed in the slot of the iron core, the coefficient of linear expansion of the coil conductor 4 and the insulating layer 3 Thermal stress due to the difference and the temperature difference are decisive, but in the actual case where the coil 1 is housed in the core slot, a restraining force by the core 7 is applied to these.
As a result, the stress generated in the coil insulating layer 3 is
is not uniform in the length direction, and shows a maximum at the part corresponding to the end of the iron core 7 of the coil 1, and the inner part and the outer part of the iron core 7 of the coil 1 center around the end of the iron core. It has become clear that the thermal stress distribution within the coil insulating layer 3 is as shown in FIG. 4, and the shear stress distribution is as shown in FIG. 5, as the stress gradually decreases as it moves away from the end.

Furthermore, investigation data on coil insulation accidents of rotating electrical machines delivered in the past also shows that the accident occurred in core 7.
It has become clear that these are concentrated in the vicinity of the edges.

As mentioned above, both experimentally and empirically, the deterioration of the coil insulation of rotating electric machines, which has been shown to be locally concentrated near the iron core end, can be diagnosed by performing the conventional diagnosis of three-phase coils all at once or individually. In tests conducted separately for each phase, all coils or 1/3 of all coils of a rotating electrical machine are measured in parallel, so the detection sensitivity is extremely low and it is difficult to detect local insulation deterioration, which is the problem at hand. The disadvantage is that it cannot be done. For example, in the case of a dielectric loss tangent test of coil insulation, a locally deteriorated portion 31 of the insulating layer 3 of the coil 1
In the equivalent circuit of FIG. 6, in which a portion 32 consisting of a coil having many other healthy insulating layers exists in parallel, the dielectric loss tangent of the deteriorated portion 31 of the insulating layer is tanδ ₁ and its capacitance is C ₁ , the dielectric loss tangent of the healthy portion of the insulating layer is tan δ ₂ , and its capacitance is C ₂ , then the dielectric loss tangent of the insulating layer of the entire coil is tan δ = C ₁ /C ₁ +C ₂ tan δ ₁ +C ₂ /C ₁ +C ₂ tanδ _2However , in this case, since C ₁ ≪C ₂ , tanδ≒C ₁ /C ₂ tanδ ₁ +tan≪ ₂ δtanδ ₁ , and as in the past, all coils are processed at once or each phase coil is The result is that local deterioration of the insulating layer cannot be detected in the tests carried out.

To solve the above-mentioned defects in conventional tests, the part of the low-resistance corona shield layer of the coil under test located near the core slot exit is separated from the other part of the coil that is electrically connected to the core. An apparatus for measuring insulation deterioration of a rotating electrical machine coil, which uses a measuring electrode to measure insulation deterioration of a coil, has already been proposed. However, in this proposal, a separate portion of the low-resistance corona shield layer, which serves as the measurement electrode, is required on the outside near the end of the core. However, as already shown in FIGS. 4 and 5, thermal stress and shear stress in the coil insulation layer due to thermal cycles occur not only at the core ends and in the vicinity outside the core, but also in the vicinity inside the core. This shows a distribution that becomes significantly large locally, so if the device proposed above simply locates the measurement electrode on the low-resistance corona shield layer outside the core near the end of the core and detects it, the deterioration of the coil insulation cannot be detected. It is impossible to accurately determine the truth.

[Purpose of invention]

The present invention is designed to detect insulation deterioration in a coil having a low resistance corona shield layer on the outer surface of the insulation layer. It is an object of the present invention to provide a device for detecting insulation deterioration of a coil of a rotating electric machine with good sensitivity, which can easily and accurately detect deterioration of an insulating layer of the coil.

[Key points of the idea]

In order to achieve the above object, the present invention provides the above-mentioned detection device, in which the low-resistance corona shield layer, which is electrically connected to the iron core through a semiconductive liner, is provided with a portion inside the iron core near an end of the iron core. The coil is then detected by an insulation deterioration detection device, which forms a part that can be electrically insulated from the iron core as needed outside the iron core, and uses the part as a detection electrode to detect insulation deterioration of the coil. Insulation deterioration of the coil is detected non-destructively without removing it from the iron core.

[Example of idea]

Next, the present invention will be explained in detail based on the embodiments shown in the drawings.

In the partial view of the stator of the rotating electric machine shown in FIG. 1, the coil 1 housed in the slot formed in the stator core 7 is connected to a suitable wire provided on the outside of the conductor 4 as already explained with reference to FIG. of the insulating layer 3,
Low-resistance corona shield layers 2a and 2b are provided on the outer surface of the portion located within the slot and the outer surface of a portion of the coil end located outside the slot, respectively.
The low-resistance corona shield layers 2a and 2b are separated from each other through a suitable insulator 5b, and the low-resistance corona shield layers 2b and 2c are separated from each other through a gap 9. ,
At this time, the low-resistance corona shield layer 2b is located around the end of the iron core 7, extending between the inside and outside of the iron core. Furthermore, low resistance corona shield layer 2
a directly, and the low-resistance corona shield layer 2b is covered with a semiconductive liner 6 via a suitable insulator 5a, and the low-resistance corona shield layer 2a
are electrically connected to the iron core 7 by the semiconductive liner 6 so as to have the same potential. Furthermore, the low-resistance corona shield layer 2c is connected to the semiconductive liner 6 by a lead wire 8a provided in a portion not covered by the high-resistance corona shield layer 20, and is therefore similarly at the same potential as the iron core 7. electrically connected. On the other hand, the low resistance corona shield layer 2b connects the lead wire 8b and the changeover switch 1.
1, and is connected to the lead wire 8c provided on the semiconductive liner 6 by the switch 11 during steady operation of the rotating electric machine, so that the insulator 5
Although it is covered by a, it is electrically connected to the iron core 7 via the semiconductive liner 6 so as to have the same potential.

With the above configuration, in the coil 1, the part of the insulating layer 3 that abuts the end of the iron core 7 where insulation deterioration is most likely to progress and the part that extends inside and outside of the iron core centering on the end of the core are provided with other coils. Since a low-resistance corona shield layer 2b is formed that is separate and independent from the low-resistance corona shield layers 2a and 2c and is covered with an insulator 5a, the low-resistance corona shield layer 2b is used as an electrode for detecting insulation deterioration for measurement. This makes it possible to accurately detect local insulation deterioration in the part to be measured without being affected by other healthy insulation layers. That is, in that case, in FIG. 1, the changeover switch 11 is switched to change the connection of the lead wire 8b from the lead wire 8c to the lead wire 8d leading to the measuring instrument 10, and the conductor 4 of the coil 1 to be measured is connected via the lead wire 8e. By applying a predetermined voltage to the coil, it is possible to measure the state of deterioration of the insulating layer 3 of the coil in the portion covered by the low resistance corona shield layer 2b. At that time, if the voltage applied to the coil conductor 4 is convection, a corona measuring device, a dielectric loss tangent measuring device, or an alternating current measuring device is used as the measuring device 10.
If it is direct current, use a direct current measuring device. Furthermore, when the rotating electric machine is in operation, it is preferable to use a measuring device with low detection impedance.

As an example, there is one on the line side of each phase of a three-phase winding.
The electric field of the dielectric loss tangent measured only for the coils equipped with the detection electrode section 2b of a rotating electrical machine in which a coil equipped with the detection electrode section 2b as shown in FIG. The characteristics are shown as curve A in FIG. Comparing this with curve B showing the electric field characteristics of the dielectric loss tangent when three-phase windings including the coil equipped with the detection electrode portion 2b are measured all at once as in the past, it is found that It is clear that the state of local insulation deterioration, which could not be detected by conventional measuring means that performs measurements, can be significantly detected with good sensitivity by the detection device of the present invention.

Therefore, if the coil equipped with the detection electrode portion 2b according to the present invention is placed on the high voltage side where insulation layer peeling or voids are likely to occur due to thermal cycle deterioration of the stator winding, the deterioration of the coil insulation layer can be prevented early. It can be detected accurately, and a great effect can be expected in terms of preventive maintenance of rotating electrical machines.

[Effect of idea]

As explained above, the present invention is an insulation deterioration detection device for a coil that is housed in the iron core of a rotating electric machine and has a low-resistance corona shield layer on the outer surface, and is electrically connected to the iron core through a semiconductive liner. A portion is formed in the low-resistance corona shield layer near the end of the core, covering the inside of the core and the outside of the core, and can be electrically insulated from the core as necessary, and the portion is used as an electrode to connect the coil. The insulation deterioration detection device, which is designed to detect insulation deterioration, provides good sensitivity while keeping the coil housed in the core of a rotating electrical machine in the part where the insulation deterioration of the coil housed in the core is most likely to occur. Since the insulation deterioration can be detected, the efficiency of preventive maintenance can be increased and unexpected suspension of operation of the rotating electric machine can be prevented.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional schematic diagram showing the relationship between a coil equipped with the coil insulation deterioration detection device of the present invention and an iron core that houses the coil, and Fig. 2 shows a general high-voltage coil housed in the iron core. A schematic cross-sectional view showing the configuration, FIG. 3 is a three-phase star wiring diagram of a typical rotating electric machine, and FIGS. 4 and 5 show the thermal stress distribution and shear that occur in the insulating layer of the coil based on thermal cycles. Figure 6 is a diagram showing stress distribution, Figure 6 is a diagram showing an equivalent circuit at the time of measurement consisting of a deteriorated insulation part and a healthy part of the coil in an insulation deterioration detection test, and Figure 7 is a diagram showing the detection of insulation deterioration of a coil according to the present invention. 2 is a diagram illustrating the electric field dissipation tangent characteristic in a test measured using a device and the electric field dissipation tangent characteristic in a conventional test measuring all coils at once. DESCRIPTION OF SYMBOLS 1... Coil, 2a, 2b, 2c... Low resistance corona shield layer, 3... Coil insulating layer, 4... Coil conductor, 5a, 5b... Insulator, 6... Semiconductive liner, 7... Iron core, 8a, 8b, 8c, 8
d, 8e...Lead wire, 9...Gap, 10...
... Measuring instrument, 11... Changeover switch.

Claims (1)

[Scope of utility model registration request] In an insulation deterioration detection device for a coil housed in an iron core of a rotating electric machine and having a low resistance corona shield layer on the outer surface, the low resistance corona shield layer is electrically connected to the iron core via a semiconductive liner. A portion that can be electrically insulated from the iron core is formed as necessary over the inside and outside of the iron core near the end of the iron core, and the portion is used as a detection electrode to detect insulation deterioration of the coil. A device for detecting insulation deterioration of a rotating electrical machine, which is characterized by: