SU143918A1 - Device for measuring capacitance between the corona wire of a high-voltage network and ground - Google Patents

Description

The proposed device for measuring capacitance between the corona wire of a high-voltage network and the ground is based on the well-known use of a wattmeter to control the load generated by the occurrence of corona discharges in the high-voltage network.

A feature of the device constituting the subject of the invention is the use of a bridge in it, in one diagonal of which a voltage meter of a wattmeter is included, the current winding of which is connected through a current transformer to one of the arms of this bridge.

The drawing shows a schematic diagram of the proposed device. The main element of this device is a four-shoulder bridge composed of two resistances RI and. shunting adjustable capacitors C and Cz; and two capacitors Cz and C4, of which capacitance Cz is the measured capacitance between the high-voltage wire and ground. In the shoulder, formed by the resistance and the capacitor Ca shunting it, the transformer includes a winding of a wattmeter W through a transformer TT, the voltage winding of which is connected to the diagonal of the bridge. Another diagonal through a high voltage transformer Ta is connected to the high voltage line.

If the bridge is in equilibrium, the voltage in the diagonal of the bridge is zero and the wattmeter shows nothing. In order to facilitate compensation, the resistors I and Rs are made variable, and the capacitor banks are used as capacitors C and C2.

When a voltage is applied to the balanced bridge circuit, it consists of a resistance, shunted by capacitor C, and capacitance C, and a current flows, causing current to flow.

No. 143918- 2 of the secondary transformer 77 of the transformer 77, and, consequently, in the current winding of a wattmeter W.

When a corona occurs on the wire, additional active reactive notaries in the line appear that cause the appearance of an additional uncompensated line current.

Part of this current flows through resistance R and capacitor C shunting it, and part passes through parallel connected resistance R and capacitor Cj and through the diagonal of the bridge. In turn, the current flowing through the diagonal of the bridge splits into two parts, one of which passes through the winding of the wattmeter voltage, and the other through the capacitor Cs driving the bypass. At the same time, the arrow of the power meter deflects by an angle proportional to the product of currents in its primary and secondary windings and the cosine of the angle between them.

The circuit element is selected in such a way that the condition:

f / i-fg-fs + f tt 0

In this expression, ф is the phase angle of the impedance Z;. + Zg, where Z and Z2 are the resistances of the arms R, Ci and Rz, Q of the bridge and Zg are the resistance of the wattmeter winding and parallel to it the switched capacitor

F1 and FS are the phase angles of the impedances Z and Z.

Here

where Zj - the resistance of the shoulder of the bridge, having a capacitor

F tt and (errors of current transformer TT and wattmeter:

F5 - phase angle of the capacitor C.

Capacitor Cj is used to fulfill the above condition. Indeed, if we neglect the errors (fn and f because of their small values, and count them, then the expression is simplified and transformed into the expression fl-f1-f5 0.

Subject invention

A device for measuring the capacitance between the corona wire of the high-voltage network and the ground, using a meter measuring device, characterized in that, in order to simplify the measurement process, the device uses a bridge circuit, the two arms of which are adjustable resistors shunted capacitors, the other two are capacitors, one of which is the measured capacitance between the high-voltage wire and the ground, and the wattmeter windings are connected: the voltage winding to the output diagonal of the bridge, and the currents and - to one of his shoulders, through a current transformer.

Z |. Z; i-b Z,

Fs