JPS596137Y2 - Insulation monitoring device for rotating machine windings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that utilizes corona characteristics to monitor insulation of rotating machine windings during operation.

The conventional technique for measuring the insulation performance of the windings of a high-voltage rotating machine using corona characteristics is as shown in FIG. A corona current detector 3 composed of a coil is connected to the corona measuring device 4 which counts the number of times a corona pulse current flows to the detector 3 through the coupling capacitor 2 within a certain period of time.

However, while the rotating machine 1 is in operation, external noises such as bushing, corona pulse current generated in power transmission lines, induction noise and switching surges that are biased towards the rotating machine through cables flow through the capacitor 2 to the detector 3. The measuring instrument 4 detects external noise as well as corona generated in the winding insulation, and the accuracy of determining the insulation performance of the winding is poor, and measurement becomes impossible when there is a lot of external noise.

An object of the present invention is to provide a monitoring device that reduces noise entering from the outside and improves the accuracy of detecting corona pulse currents generated from rotating machine windings.

The monitoring device according to the present invention connects a series connection body of a coupling capacitor and a corona current detector to two-phase windings of the multi-phase windings of a rotating machine, and converts the voltage difference between the outputs of both detectors into a differential transformer. By detecting this, external noise is canceled out and only the corona pulse current generated from the winding is detected.

FIG. 2 shows an embodiment of the present invention.

Coupling capacitors 2u and 2■ are connected to the windings 1u and lv of the rotating machine 1 at the connection with the power source 5, respectively, and both capacitors 2u
, 2■ and ground, resistor or coil detectors 3u and 3v are connected.

The output voltages of the detectors 3u and 3V are determined by the differential transformer 6.
The output of the differential transformer 6 is the input of the filter 7.
It is input to the corona measuring device 8 through.

The measurement results of the corona measuring device 8 are sent to a monitoring output section 9 which has a function of determining the quality of the insulation state of the rotating machine and further having an alarm display function.

In this way, the pulse current generated on the high voltage side of the arbitrarily selected two-phase winding is detected by the detectors 3u and 3v, and the detected voltage difference is detected by the differential transformer 6.

Therefore, the power cables of the rotating machine 1 are close to each other in parallel, and external noise is applied to the windings of the same phase noise current of each phase cable through capacitive coupling between each phase of the cable, so the external noise component is transmitted to the detector 3. They are extracted at substantially the same phase and level as u and 3v, and are canceled out by the differential transformer 6.

Incidentally, the slight phase difference between the two signals is balanced by an impedance element 10 as shown in FIG.

On the other hand, since the corona generated in the insulated part of the winding occurs only on the high voltage side, part of the corona current generated in the insulated part flows through the coupling capacitor connected to the same phase, and part of it flows from the in-phase to the phase winding. propagates and flows through the coupling capacitor of the other phase.

The corona current flowing into the windings of other phases is divided at the neutral point, and because the line length is large, the degree of attenuation becomes large and there is a phase lag.

Therefore, the current flowing through the coupling capacitor connected to the high voltage side of the phase in which the corona current is generated becomes larger than the current flowing through the coupling capacitor connected to the other phases, and the differential transformer 6 can detect only the corona current.

Note that external noise may not be superimposed on each phase at the same phase and level, and in this case it is difficult to distinguish it from the corona current in the winding, but corona measuring equipment 8 etc. perform averaging processing within a certain period of time and To determine insulation abnormalities based on changes over time, etc.
External noise components that are measured sporadically do not pose a problem in terms of measurement accuracy.

As described above, the monitoring device according to the present invention has the effect of being able to accurately detect the corona pulse current from which external noise has been removed with relatively simple precautions.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional rotating machine winding insulation monitoring device, Figure 2 is a circuit diagram showing an embodiment of the present invention, and Figure 3 is a balance circuit for the corona current detector in Figure 2. FIG. 1...Rotating machine, 2u, 2■...Coupling capacitor, 3u, 3v...Corona current detector,
6...Differential transformer, 7...Filter, 8...Corona measuring device, 9...Monitoring output section, 10...Impedance element.

Claims (1)

[Scope of utility model registration request] Corona current detectors of the windings are connected to the high-voltage sides of two sets of windings of the rotating machine through coupling capacitors, respectively, and a differential transformer is used to detect the differential voltage between the outputs of both detectors. An insulation monitoring device for a rotating machine winding, characterized by measuring corona characteristics of an insulating part of the rotating machine winding from output.