JPH0279750A - Diagnostic method of insulation of electrical equipment - Google Patents

Abstract

PURPOSE:To diagnose insulation simply and positively before the start of operation by applying pulse voltage between the winding terminal and core of an electrical equipment and informing an operator of abnormality on the basis of the phase difference between the applied voltage current. CONSTITUTION:When an operating switch for a motor 5 is turned ON and a startup command is transmitted, a current phase detector 2 is brought to the state of operation instantaneously, and the high-frequency pulse voltage of several pulses is applied among each terminal of the winding of the motor 5 and a core from a high-frequency pulse generating circuit 1. The phase of currents made to flow into the winding at that time is detected by the current phase detector 2, and the current phase and the phase of pulse voltage are compared by a voltage-current phase comparison circuit 3. When the phase difference is brought to a specified value or less at that time, an electromagnetic contactor is not turned ON, and 'abnormality of insulation to ground' is displayed in an indicator 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for diagnosing the insulation of electrical equipment equipped with windings.

(Prior Art) With the recent development of semiconductor technology, there are many occasions where a pseudo sine wave formed by a collection of square wave pulse voltages is applied to electrical equipment, such as an output waveform from an inverter device. However, since such voltage waveforms often include steep surges, insulation of electrical equipment tends to become a problem.

In this regard, conventional methods for diagnosing the insulation of electrical equipment include a method of determining the direct current leakage current Al1 using a direct current insulation resistance meter, or a method of measuring the dielectric loss angle by applying an alternating current voltage.

(Problem to be solved by the invention) However, in both methods, the 71-3 constant results must be read using a special device/testing device and then judged by humans, so in reality, it is quite difficult to It's a hassle. For this reason, insulation diagnostic tests, which are normally required on a regular basis, are rarely carried out reliably, and in reality, insulation abnormalities are only discovered when smoke or sparks occur after the power is turned on.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an insulation diagnosis method for electrical equipment that can easily and reliably perform insulation diagnosis before starting operation of the electrical equipment.

[Structure of the Invention] (Means for Solving the Problems) One of the methods for diagnosing the insulation of electrical equipment of the present invention is to apply a pulse voltage between the winding terminal and the iron core of the electrical equipment before starting operation, The feature H is that the phase difference between the current flowing at this time and the pulse voltage is detected, and an abnormality is notified when the phase difference is less than a predetermined value.

Another feature is that instead of between the winding terminal and the iron core in the above method, a pulse voltage is applied between the windings of different phases with the star connection of the electrical equipment open. .

(Function) The current that flows when a voltage is applied to the insulator of an electrical device is a composite current of a leakage current that is in phase with the voltage and a charging current that is 90'' ahead of the voltage, as shown in FIG. And the leakage current of a new, undegraded insulator is about 1n-"
Since the leakage current/charging current ratio is extremely small, A~10-''A, and the ratio of leakage current/charging current is sufficiently small, the dielectric loss angle δ is small.

Therefore, when a pulse voltage is applied between the winding terminal and the iron core or between the windings of different phases with the star connection open, the phase difference Δ between the applied voltage and the current flowing at that time is due to the deterioration of the insulator. When there is no alarm, it is loud and no abnormality is notified.

However, when the insulation deteriorates due to thermal oxidative decomposition due to long-term use, the insulation becomes more likely to absorb moisture.
Local carbonization due to tracking may occur, increasing leakage current. Then, when a pulse voltage is applied, the phase difference Δ between the applied voltage and the current becomes larger than a predetermined value,
An abnormality is reported.

(Example) Hereinafter, an example 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 potential 10 output 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 200 KH2, for example, and this is applied between the winding end -r of the motor 5 and the iron core (earth) or between the windings. Although not shown, the motor 5 is equipped with an electromagnetic contactor for separating and opening the star connection portion of the windings. The current phase detection circuit 2 detects the phase of the current flowing into the windings of the motor 5 based on the signal from the current detector 2a. Further, the voltage-current phase comparison circuit 3 compares the phase of the pulse voltage outputted from the high-frequency pulse generation circuit 1 and the phase of the current detected by the current phase detection circuit 2, and the phase difference between them is greater than or equal to a predetermined value. When it is, an electromagnetic contactor 7 provided between the motor 5 and the power source 6
When the phase difference is less than a predetermined value, the electromagnetic contactor 7 is prevented from being turned on and the indicator 4 is activated.

Now, the functional configuration of this embodiment is shown in FIG. 1 in detail.

When the operation switch of the motor is turned on and a command to start operation is given, the current phase detection circuit 2 is immediately activated, and then the high-frequency pulse generation circuit 1 is first connected between each terminal of the winding of the motor 5 and the iron core. Several pulses of high-frequency pulse voltage 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 potential comparison circuit 3. Here, when the difference is equal to or greater than a predetermined value, the electromagnetic contactor 7 is not turned on, and the display 4 displays "ground insulation abnormality". This large phase difference means that the angle Δ
is large, which means that the ground insulation has deteriorated and the leakage current is large. Thereby, it is possible to prevent the motor 5 from burning out due to operation even though the ground insulator has deteriorated.

On the other hand, when there is no abnormality in the ground insulation and the phase difference is greater than or equal to a predetermined value, an electromagnetic contactor (not shown) is activated.
The star connection of the winding of motor 4 is separated from the ground.
open to each other. After this, between the windings of each phase (U-V,
V-W, W-U) l: A high-frequency pulse voltage is sequentially applied 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, and the current phase and pulse voltage are detected by the current phase detection circuit 2. The voltage-current phase comparator circuit 3 compares the phase with the voltage-current phase comparison circuit 3. Here, when the phase difference between any of the windings is less than a predetermined value, it means that the interphase insulator has deteriorated and the leakage current has increased.
Again, the electromagnetic contactor 7 is not turned on, and the display 4 displays "...Insulation abnormality". This results in
Motor 5 is operated even though the interphase insulation has deteriorated.
It is possible to prevent a burnout accident from occurring.

Further, when there is no abnormality in the phase insulation and the phase difference is equal to or greater than a predetermined value, the magnetic contactor is activated to close the star connection of the windings of the motor 4, and the magnetic contactor 7 is also turned on to connect the motor 5. operation will begin.

As described above, in this embodiment, each time the operation switch of the motor 5 is turned on, an insulation diagnosis of the insulation between the N/I ground and the phase is performed, and if there is a defect in the insulation, the operation is not started and the insulation is normal. Since operation is started only at a certain time, it is possible to prevent a burnout accident of the motor 5 due to deterioration of the insulator or the like.

In general, burnout accidents of industrial motors occur frequently when restarting operation after a long period of suspension, so performing an insulation diagnosis every time operation is started as in this example is important from the viewpoint of accident prevention. It is extremely H-effective.

Furthermore, since the voltage applied to the windings for insulation diagnosis is several high-frequency pulses, rapid diagnosis is possible.

Furthermore, since high-frequency pulses apply less power to insulators than low-frequency commercial power sources, damage to insulators is not a serious problem even if the diagnosis is performed every time the motor 5 is operated. It won't happen. This point is made clear from the energized life characteristics of the motor windings shown in FIG. In the figure, the vertical axis shows the voltage, the horizontal axis shows the number of pulses, and
The frequency is compared between 60H2 and 200KH2, and it is shown that even at the same voltage, 200KHZ has a longer life.

In the above embodiment, an example was shown in which the method was applied to a method for diagnosing insulation of motor windings, but the present invention is not limited to this, and of course may be applied to a method for diagnosing insulation of other electrical equipment such as transformers. be.

[Effects of the Invention] As described above, according to the present invention, a pulse voltage is applied between the winding terminal and the iron core of an electrical device, or between the windings of different phases with the star connection part open. Since abnormality notification is made based on the phase difference between the current flowing at the time and the pulse voltage, an excellent effect is achieved in that insulation diagnosis can be performed easily and reliably by 71% before starting the operation of the electrical equipment.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with Fig. 1 being a flowchart, Fig. 2 being a block diagram, Fig. 3 being a diagram showing the energized life characteristics of motor windings, and Fig. 4 showing when a voltage is applied to an insulator. FIG. 2 is a vector diagram showing the 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 (electrical equipment). Figure 1 Figure 3

Claims (1)

[Claims] 1. Before starting operation, a pulse voltage is applied between the winding terminal and the iron core of the electrical equipment, and the phase difference between the current flowing at this time and the pulse voltage is detected and the phase difference is calculated. 1. A method for diagnosing insulation of electrical equipment, characterized in that an abnormality is notified when is less than a predetermined value. 2. Before starting operation, open the star connection of the windings of the electrical equipment, apply a pulse voltage between the windings of different phases, and detect the phase difference between the current flowing at this time and the pulse voltage. A method for diagnosing insulation of electrical equipment, characterized in that an abnormality is reported when a phase difference is less than a predetermined value.