JP2590232B2 - Diagnosis method for electrical equipment insulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for diagnosing insulation of an electric device having a winding.

(Prior Art) With the recent development of semiconductor technology, there are increasing opportunities to apply a pseudo sine wave by a set of square-wave pulse voltages to electric equipment, for example, an output waveform from an inverter device. However, since such a voltage waveform often includes a steep surge, insulation of an electric device tends to be a problem.

In this regard, as a conventional method of diagnosing insulation of electric equipment, there has been a method of measuring a DC leakage current using a DC insulation resistance meter or a method of measuring an dielectric loss angle by applying an AC voltage.

(Problems to be Solved by the Invention) However, in any method, the measurement result must be read using a special device / tester and judged by a person. . For this reason,
Insulation diagnostic tests, which are required on a regular basis, are rarely performed reliably, and in reality, it is actually the case that insulation abnormalities are discovered only when smoke or sparks occur after the power is turned on.

Therefore, an object of the present invention is to provide a method for diagnosing insulation of electric equipment, which can easily and reliably perform insulation diagnosis before starting operation of the electric equipment.

[Configuration of the Invention] (Means for Solving the Problems) One of the insulation diagnosis methods for electric equipment of the present invention is to apply a pulse voltage between a winding terminal of an electric equipment and an iron core before starting operation, A feature is that the phase difference between the current flowing at this time and the pulse voltage is detected, and when the phase difference is equal to or smaller than a predetermined value, an abnormality is notified.

Another feature is that, instead of between the winding terminal and the iron core in the above-described method, a pulse voltage is applied between windings of different phases in which the star connection portion of the electric device is opened. .

(Operation) The current flowing when a voltage is applied to the insulator of the electric device is a combined current of a leakage current having the same phase as the voltage and a charging current advanced 90 ° from the voltage, as shown in FIG. And the leakage current of a new insulator that has not deteriorated is about 10 ^-10 A
The dielectric loss angle δ is small because the leakage current / charging current ratio is extremely small, that is, as small as 10 ⁻¹⁹ A.

Therefore, when a pulse voltage is applied between the winding terminal and the iron core or between windings of different phases with the star connection part opened,
The phase difference Δ between the applied voltage and the current flowing at that time is large when the insulator is not deteriorated, and the abnormality is not notified.

However, if the insulator deteriorates due to thermal oxidative decomposition or the like due to long-term use, for example, the insulator easily absorbs moisture or local carbonization due to tracking occurs, thereby increasing the leakage current. Then, the phase difference Δ between the applied voltage and the current when the pulse voltage is applied becomes larger than a predetermined value, and the abnormality is notified.

Hereinafter, an embodiment in which the present invention is applied to a motor insulation diagnosis method will be described with reference to the drawings.

The overall schematic configuration is as shown in FIG. 2, and includes a high-frequency pulse generation circuit 1, a current phase detection circuit 2, a voltage-current phase comparison circuit 3, and a display 4. The high-frequency pulse generating circuit 1 outputs a high-frequency pulse having a frequency of, for example, 200 KHZ, which is applied between a winding terminal of the motor 5 and an iron core (earth) or between windings. Although not shown, the motor 5 is provided with an electromagnetic contactor for separating and opening the star connection portion of the winding. The current phase detection circuit 2 detects the phase of the current flowing into the winding of the motor 5 based on a signal from the current detector 2a. The voltage-current phase comparison circuit 3 compares the phase of the pulse voltage output from the high-frequency pulse generation circuit 1 with the phase of the current detected by the current phase detection circuit 2, and the phase difference is equal to or more than a predetermined value. In the case of, the electromagnetic contactor 7 provided between the motor 5 and the power supply 6 is turned on. When the phase difference is equal to or less than a predetermined value, the turning on of the electromagnetic contactor 7 is prevented and the display 4 is operated.

Now, the functional configuration of the present embodiment is specifically described as follows.
As shown in the figure.

When the operation switch of the motor 5 is turned on and an operation start command is given, the current phase detection circuit 2 is immediately activated, and then a high-frequency pulse generation circuit is connected between each terminal of the winding of the motor 5 and the iron core. One to several high-frequency pulse voltages are applied. Then, the phase of the current flowing into the winding at that time is detected by the current phase detection circuit 2, and the current phase and the phase of the pulse voltage are compared by the voltage-current phase comparison circuit 3. Here, when the phase difference is equal to or smaller than the predetermined value, the display 4 displays “abnormal ground insulation” without turning on the electromagnetic contactor 7. A large phase difference means that the angle Δ in FIG. 4 is large, the ground insulation is deteriorated, and the leakage current is large. As a result, it is possible to prevent a situation in which the motor 5 is burned due to operation while the ground insulation is deteriorated.

On the other hand, when there is no abnormality in the ground insulation and the phase difference is equal to or more than the predetermined value, an electromagnetic contactor (not shown) is operated, and the star connection of the winding of the motor 5 is separated from the ground and opened to each other. Then, between the windings of each phase (U-
V, V−W, W−U) are sequentially applied with a high-frequency pulse voltage from the high-frequency pulse generation circuit 1, and the phase of the current flowing into the winding at that time is detected by the current phase detection circuit 2. The current phase and the phase of the pulse voltage are compared by the voltage-current phase comparison circuit 3. Here, when the phase difference between any of the windings is equal to or less than a predetermined value, it means that the interphase insulator has deteriorated and the leakage current has increased, so that the electromagnetic contactor 7 is also turned on. Instead, the display 4 indicates "interphase insulation abnormality". Accordingly, it is possible to prevent the motor 5 from being burned out even though the interphase insulator is deteriorated. When there is no abnormality in the inter-phase insulation and the above-mentioned phase difference becomes a predetermined value or more, the electromagnetic contactor is activated to close the winding star connection portion of the motor 4, and the electromagnetic contactor 7 is turned on to turn on the motor 5. Operation is started.

As described above, in the present embodiment, each time the operation switch of the motor 5 is turned on, the insulation diagnosis of the insulator between the ground and the phase is performed. When the insulation is defective, the operation is not started, and when the insulation is normal. Since the operation is started as long as possible, it is possible to prevent the motor 5 from being burned due to the deterioration of the insulator. In general, there are many cases of industrial motor burnout accidents, such as when restarting operation after a long period of inactivity. This is extremely effective from the viewpoint of. Further, since the voltage applied to the winding for the insulation diagnosis is a few high-frequency pulses, a quick diagnosis is possible. Further, since the high-frequency pulse gives less power to the insulator than the low-frequency commercial power supply, even if the diagnosis is performed every time the motor 5 is operated, the damage to the insulator does not actually pose a problem. . This point is made clear from the charging life characteristic of the motor winding shown in FIG. In the figure, the vertical axis represents the voltage, the horizontal axis represents the number of pulses, and the frequency is compared between 60 HZ and 200 KHZ.
It is shown that the life is long at 0 KHZ.

In the above-described embodiment, an example in which the present invention is applied to an insulation diagnosis method of a motor winding is shown. However, the present invention is not limited to this, and it is needless to say that the invention may be applied to an insulation diagnosis method of another electric device such as a transformer. is there.

[Effects of the Invention] As described above, according to the present invention, a pulse voltage is applied between a winding terminal of an electric device and an iron core, or between windings of different phases in which a star connection portion is opened. Since the abnormality is notified based on the phase difference between the current and the pulse voltage that flows sometimes, there is an excellent effect that the insulation diagnosis can be easily and reliably performed before the operation of the electric device is started.

[Brief description of the drawings]

1 is a flowchart, FIG. 2 is a block diagram, FIG. 3 is a characteristic diagram of an applied life of a motor winding, and FIG. 4 is a diagram when a voltage is applied to an insulator. FIG. 6 is a vector diagram showing a current phase of FIG. In the drawings, 1 is a high-frequency pulse generation circuit, 2 is a current phase detection circuit, 3 is a voltage-current phase comparison circuit, 4 is a display, and 5 is a motor (electric device).

Claims (2)

(57) [Claims] 1. A pulse voltage is applied between a winding terminal of an electric device and an iron core before starting operation, a phase difference between a current flowing at this time and the pulse voltage is detected, and the phase difference is set to a predetermined value. A method for diagnosing insulation of an electric device, wherein an abnormality is notified at the following times. 2. A pulse voltage is applied between windings of different phases by opening a star connection portion of windings of an electric device before starting operation.
A method for diagnosing electrical equipment insulation, comprising detecting a phase difference between a current flowing at this time and the pulse voltage, and notifying an abnormality when the phase difference is equal to or less than a predetermined value.