JPS6140943B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for electrically diagnosing insulation damage status of coil insulation of a rotating electric machine.

[Technical background of the invention and its problems]

In contrast to conventional coil insulation, as well as to coil insulation due to the recent rise in voltage, reliability has been a major issue in conventional coil insulation configurations, and electric field mitigation materials have been used as a means of improving characteristics and reliability. A method of coating or winding the material in the innermost layer or insulating layer is used. However, diagnostic tests and life estimation of equipment insulation currently in operation have not yielded significant results, and there is a strong demand for life estimation.

Insulation deterioration of rotating electrical machine coils during operation is
This is due to electrical deterioration combined with mechanical deterioration, thermal deterioration, etc. In particular, this electrical deterioration often takes the form of deterioration called electric tree accompanied by partial discharge. Generally, electrical coil insulation takes the form of composite insulation, and is opaque, making it almost impossible to observe the progress of this electrical tree.

Among various methods for diagnosing insulation life, there is one that tracks dielectric loss tangent (tan δ), insulation resistance, etc. as an easy non-destructive diagnostic test. The characteristics determined by these tests have a small rate of change as shown in FIGS. 1A and B, and empirical judgment and difficult statistical processing are essential for life estimation. As a breakdown diagnostic test that diagnoses the coil insulation by breaking it down, the coil is pulled out every predetermined operating time as shown in Figure 1C, and the dielectric breakdown voltage is measured, and the change in electric field strength is tracked by dividing this by the coil insulation thickness. There is a way to do it. This test clearly shows a decrease in the electric field strength, making it easy to estimate the insulation life. The various costs involved in manufacturing and assembling the system will be large.

[Purpose of the invention]

The present invention provides an insulation diagnosis that can electrically detect damage caused by electrical, thermal, mechanical, etc. stress on the coil insulation in the iron core slot of a rotating electric machine and near the slot exit, and can obtain effective insulation diagnosis results. The purpose is to provide a method.

[Summary of the invention]

The present invention forms a semiconducting layer in the coil insulation layer of a rotating electric machine, and measures the capacitance between the low resistance shield layer provided on the outer periphery of the coil insulation layer or the iron core and the coil conductor to detect changes in the coil insulation. Let's make a diagnosis.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 2 to 4. Figure 3 A, B,
C and D are second cross-sections, showing portions located near the iron core slot and slot outlet in the rotating electric machine. The coil insulation 2 is formed on the coil conductor 1 by winding a mica tape or the like, and in accordance with the process of winding the mica tape or the like, the semiconducting material is coated with equally spaced layers or layers with respect to the thickness of the coil insulation. The first semiconducting material layer 3 and the second half are wrapped around an appropriate spacing layer from the part of the coil insulation that requires coil insulation diagnosis located in the core slot 6 to the vicinity of the core slot outlet 7. It has an insulating structure with a flow layer 4 of conductive material. In order to prevent corona discharge occurring in the gap between the core slot 6 and the coil insulation 2 when the coil configured as described above is inserted into the core slot 6, a portion of the outer circumference of the coil insulation 2 located in the core slot 6 is Low resistance corona shield layer 9 provided near the slot exit 7
form. Then, the capacitance is measured using the low-resistance corona shield layer 9 or the iron core 8 and the coil conductor 1 in contact with the low-resistance corona shield layer 9 as measurement electrodes.

The development of the electrical tree, which is a form of insulation deterioration during operation, takes a long time until the electrical tree 5 of FIG. 3B is formed and then accelerates. When the electrical tree 5 reaches the first semiconducting material layer 3 as shown in FIG. 3C, the total distance of the coil insulation 2 (the distance between the coil conductor 1 and the low resistance corona shield layer 9) d in FIG. 3B
is apparently the distance d ₁ between the first semiconducting material layer 3 and the low-resistance corona shield layer 9. Furthermore, when the electrical tree 5 reaches the second semiconducting material layer 4 as shown in FIG. 3D, the total distance d of the coil insulation 2 in FIG. 3B becomes
The apparent distance between the second semiconducting material layer 4 and the low-resistance corona shield layer 9 is d ₂ . When d changes in this way, C=εS/d (where, C: capacitance, ε: permittivity, S: area,
The capacitance determined by d: interval) changes, and an inflection point appears as shown in FIG. 4, and the state of development of the electric tree inside the coil insulation 2 becomes clear, making it easy to estimate the service life.

The semiconductive material used here is preferably a material that has a surface resistivity of 10 ³ Ω to ^{10 9} Ω, does not impair its function as a coil insulator, and can be processed into a sheet or tape shape. For example, asbestos tape, carbon powder treated tape, carbon fiber treated tape, etc. In a structure made of a semiconducting material with a surface resistivity of 10 ⁹ [Ω] or more, it is difficult to measure capacitance to detect the progress state of the electrical tree.
In addition, this insulation structure is applied to all the coils or only to the high voltage application section coils of each phase, and by incorporating it into an electrical device, insulation diagnosis can be performed for those coils.

Next, other embodiments will be described. That is,
The semiconducting material layer formed in the coil insulation 2 of the above embodiment is one layer. The position relative to the thickness of the insulation to be formed is such that it is possible to detect the progress of the electrical tree when the coil insulation reaches the end of its service life, for example, when the dielectric strength is halved.In the longitudinal direction of the coil, the position is within the slot of the iron core as described above. It is formed from the part where the slot is inserted to the vicinity of the slot exit. When we measure the capacitance of a coil configured in this way in the same way as above, we get
The state of deterioration, especially the point at which the dielectric strength is reduced by half, becomes clear.

〔Effect of the invention〕

In the insulation diagnosis method of the present invention, a coil insulation with a semiconducting material layer embedded is used, so by measuring the capacitance of the outer periphery of the insulation layer and the coil conductor layer, the state of deterioration of the insulation can be clearly determined. This makes it possible to easily and accurately diagnose the insulation life.

[Brief explanation of the drawing]

Fig. 1 is a diagram generally showing changes in electrical characteristics in a rotating electrical machine coil, Fig. 2 is a cross section of a rotating electrical machine coil according to an embodiment of the present invention, and Fig. 3 is a diagram showing -
FIG. 4 is a cross-sectional view along a line showing the evolution of an electric tree, and FIG. 4 is a diagram showing a change over time in the capacitance of the coil in FIG. 3. 1...Coil conductor, 2...Coil insulation, 3...
First semiconducting material layer, 4... Second semiconducting material layer, 5
...Electric tree, 6...In iron core slot, 7...
Slot exit, 8... Iron core, 9... Low resistance corona shield layer.

Claims (1)

[Claims] 1 A semi-conducting layer is formed in the insulating layer of the coil of a rotating electrical machine, and a low resistance corona shield layer is provided on the surface of the coil, or the capacitance between the iron core in which the coil is housed and the conductor of the coil. A method for diagnosing the insulation of rotating electric machine coils by measuring .