SU48795A1 - Device for determining partial breakdown of insulation - Google Patents

Description

To find defective insulation In high voltage circuits, an insulation test for breakdown, measurement of the dielectric loss angle and capacitance, and, in some cases, insulation resistance, are currently used.

A modern high-voltage insulator with a considerable dielectric thickness can be considered as a series of series-connected capacitors equivalent to separate insulating layers.

Under certain conditions, the electrical strength of individual layers decreases unevenly, for example, a capacitor sleeve, part of the layers of which is punctured by a pulse, in a wire of suspension insulators with a punched element or In an oil-filled sleeve with distorted gradient distribution, etc. subjected to a breakdown test. Discharges may occur in the weakened parts. However, the remaining parts of the insulator can be quite strong and pass the test; therefore partially

a punctured isolator will not be detected.

Methods for measuring the angle of loss and capacitance, or methods for measuring the insulation resistance, also cannot serve to detect partial breakdown, since these parameters, with practically acceptable test voltages, can change only slightly due to partial damage.

In contrast to the known insulation testing methods, the present invention allows to detect the occurrence of partial insulation.

For this purpose, an additional device that reacts to the appearance of bits during partial breakdown of the test insulation is introduced into the test facility.

Various embodiments of the device are shown in FIG. 1, g and 3. It consists of a high voltage transformer T, a protective resistance R and an oscillating channel LC, equipped with an indicator G. A is the test object. The oscillatory circuit can be connected to the test circuit in various ways. FIG. 1 shows a serial connection of the contour with the object; FIG. 2 - parallel. In the second case, an additional capacitor C is needed to protect the circuit from high voltage. Finally, an oscillating circuit, as shown in FIG. 3 may be inductively coupled to the test circuit.

The operation of the device is as follows. If, when tested in object X, discharges arise, they will cause oscillations in the LC circuit, whose frequency will be determined by the parameters of the circuit.

If there are oscillations on the circuit, some voltage will be indicated by the indicator G. The magnitude of this voltage will depend on the intensity of the discharge in the insulation, i.e. the spark length, the values of internal capacitances that limit the power of the discharge current , discharge channel charredness, test voltage, etc. In addition, the magnitude of the voltage in the LC circuit itself affects the magnitude of the voltage on the LC circuit, i.e. its self-induction, resistance capacity, and attenuation introduced into the Circuit by the indicator G and others and external chains. ,

As it follows from the above, the LC circuit may have different parameters, however, to obtain the greatest sensitivity, it is better to adhere to certain defined limits. Thus, for example, with experimental testing, good results were obtained with a contour with a frequency of its own oscillations ranging from a thousand to several tens of thousands of hertz. In this case, the device can be small in size, and easily detects very weak bits. In addition, the LC circuit should not have noticeable resistance. It is desirable that the indicator G in turn introduces a minimum attenuation to the LC system.

Chroshig results gives, for example, a cathode voltmeter with high internal resistance.

Thus, the principle of operation of the described device differs essentially from the known insulation testing facilities in that it is based on the evaluation of the insulation not by its electrical properties, but by the presence and magnitude of bits inside the insulation, an unconditional sign of a partial decrease in electrical strength. This makes it possible to detect not only perfectly punctured, but also partially punctured insulators, and the equipment required is simple and the test procedure is not complicated.

This principle can be applied both in ordinary insulation tests and in the form of a device permanently connected to a high voltage network and marking the occurrence of high frequency currents that are indicative of a possible damage to the insulation. The device, if necessary, can be equipped with an amplifier or associated with a relay protection.

The subject matter of the invention.

Claims (3)

1. A device for determining partial isolation isolation, characterized in that it employs an oscillatory circuit associated with the circuit of the test object, in which, with abrupt changes in the current in the test circuit, oscillations occur, marked by some indicator. 2. The form of the apparatus according to claim 1, characterized in that for adjusting the magnitude of the connection between the test circuit and the oscillating circuit, serve resistance, inductance, capacitance or mutual inductance, through which the oscillatory circuit is connected to the test circuit. 3. In the device according to claim 1 and 2, reinforce / m to use it in order to increase its sensitivity.  copyright certificate A, N. Vlasov E.S. Arkhangelskogo M 48795 CtlHr.l