SU1480008A1 - Device for measuring network capacity under operating voltage - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to reduce the mass-dimensional parameters of the device, improving measurement accuracy and electrical safety. The device contains a connecting filter 1, a transformer 2 with a magnetic core with nonmagnetic gaps, an exemplary low-voltage capacitor 3, a shunt 4, a measuring unit 6, a source 5 of a high-frequency signal F _R. The actual values of capacitance and capacitance of the electrical network are determined by the expression given in the description of the invention. Determining the actual value of the network capacity relative to a known exemplary capacity greatly improves the measurement accuracy. 1 il.

Description

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The invention relates to electrical engineering and is intended to determine the total capacitive current of the earth fault and the capacitive currents of parts of the network separated according to the operating conditions, determine the power of the self-guided reactors and select their installation sites and their settings, calculate the closure protection settings the earth.

The purpose of the invention is to reduce the mass and dimensional parameters of the device, improving measurement accuracy and electrical safety for the personnel performing the measurement.

The drawing shows a circuit diagram of a device for measuring network capacity under operating voltage.

The proposed device consists of a capacitive connecting filter 1 and a transformer 2 and a capacitor 3 of an exemplary capacitor connected in series with it, to the secondary winding of transformer 2 through shunt A is connected a source 5 of a high-frequency signal with frequency fr, and measuring unit 6 through a filter 7 tuned to frequency ff ,

connected to shunt 4.

Changing the value of the network capacity using the proposed device is performed as follows.

When the capacitive connection filter 1 is disconnected from the high-voltage network, a capacitor 3 of an exemplary capacitance is connected to the device and the high-frequency signal source with a frequency of ir is turned on. In the circuit consisting of elements 1, 2 and 3 (the capacities of the connecting filter are connected in parallel), a current of frequency fp flows, which from the primary circuit, from shunt 4 and filter 7 tuned to frequency fg, goes to measuring unit 6. According to The measuring unit 6 determines the value of V, which is proportional to the known capacitance (capacitive resistance).

Next, the capacitor 3 is disconnected, and the connecting capacitive filter 1 is connected through a switch or disconnector of any connection to the high-voltage network and a similar measurement is taken, the value of Vc proportional to the capacity of the electrical network (capacitive impedance of the network).

The actual values of capacitance and capacitance of the electrical network are determined by the expression

- C - C

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V

 V ,,

Determining the actual value of the network capacity relative to the known exemplary capacity significantly improves the measurement accuracy as compared with the direct method described in the prototype, since it eliminates the errors introduced by the instruments.

The use of a transformer tuned to resonance with the capacity of the attachment filter can significantly reduce the size of the device and improve the measurement accuracy. In the prototype it is necessary to use a connecting capacitive filter with a capacity of one order, as the network capacity. The use of a smaller capacity leads to an increase in the error, since the connecting capacitive filter and the network capacity are connected in series.

Claims (1)

In the invention, the capacitance capacitance filter capacitance is assumed to be 0.2-1 microfarads, which is 100-200 times smaller with respect to the network capacitance, and accordingly requires capacitor banks for the capacitance capacitance capacitance filter of much smaller dimensions. It is necessary to take into account that the capacitor banks of the connecting capacitive filter are the most expensive element. The capacitive resistance of the connecting capacitive filter is compensated by the inductive resistance of the transformer, which, in turn, reduces the required power of the high-frequency signal source with frequency fr for measurements. The use of high-voltage isolation in a transformer with a high-frequency signal source and a measuring unit makes it possible to increase the electrical safety of the personnel conducting the measurements when single-phase short circuits and overvoltages occur (switching, thunderstorms, etc.). Invention Formula A device for measuring the network capacity under operating voltage, containing a source of a high-frequency signal, a capacitive connecting filter with a means for connecting to the network and a measuring unit, characterized in that, in order to reduce the mass and dimensions of the device, to improve measurement accuracy and electrical safety, the device is equipped with a transformer, the magnetic circuit of which is made with non-magnetic gaps, a capacitor of an exemplary capacitance, an IT filter shunt, the primary winding of high voltage trans the formatter. One end is connected to the capacitive connection filter, and the other Hym to earth, with the inductive resistance of the primary winding of the transformer chosen to be equal to the capacitance of the connecting filter at the frequency fr produced by the high-frequency signal source, and the capacitor of the reference capacitor is made in parallel with the circuit consisting of the primary winding of the transformer and the connecting filter The measuring unit is connected to the shunt through a filter tuned to the frequency fr, and the source of the high-frequency signal is connected via the shunt to the secondary winding ke transformer.