SU853570A1 - Device for locating grounding in networks with isolated neutral - Google Patents

Description

one

The invention relates to electrical measuring equipment and can be used to create devices for remotely determining the location of a ground fault in a current-source network with an insulated neutral.

A device for determining the location of a ground fault in high voltage networks, comprising current and voltage transformers, direct and reverse sequence filters, and meters l. A disadvantage of this device is the low accuracy due to the influence of the magnitude of the transient resistance at the location of the closure and the magnitude of the resistivity of the soil.

Closest to the proposed device contains a meter, a three-phase voltage transformer, the primary windings of which are connected according to the star circuit and connected to the corresponding phases of the monitored network, and the secondary windings are connected according to the open triangle scheme 2. .

The aim of the invention is to improve the accuracy.

To achieve this goal, a known device for determining the location of a ground fault in networks with insulated neutral, contains

Claims (1)

10 meter, a three-phase voltage transformer, the primary windings of which are connected according to the star circuit and connected to the corresponding phases of the monitored network, and the secondary windings are connected according to the open triangle circuit, equipped with a matching transformer, rectifier, capacitor, resistor, DC source, compens20 by a variable current source with a variable resistor, the terminals of the variable resistor are connected to the poles of the compensation current source, and the middle terminal is connected, respectively The meter input and the positive pole of the DC source, the terminals of the primary winding of the matching transformer are connected to the corresponding terminals of the secondary windings of a three-phase voltage transformer, and the terminals of the secondary winding of the matching transformer are connected to the inputs of the rectifier, the outputs of which are connected respectively to the positive pole a sensing current source and with a common bus. In this case, the neutral of the primary windings of the three-phase voltage transformer is connected to the second input of the meter directly and to the common bus through the capacitor, and the negative pole of the direct current source is connected to the common bus through the resistor. The drawing shows the structures on the electrical circuit of the device. The device contains a three-phase voltage transformer 1, the primary windings of which are connected to the controlled network 2, and the neutral is connected to the meter.3 and, through a capacitor 4, to the common wire 5,. The secondary winding of the three-phase voltage transformer is connected to the matching transformer 6, and the secondary winding of the transformer 6 is connected to the switch 7, the common power supply 8 and the resistor 9 are connected to the common bus 5 and the resistor 9, the rectifier 7 is connected opposite to the compensation current source- 10, which is connected via a variable resistor 11 to the meter 3. The device operates as follows. In the normal operating mode of the three-phase controlled network 2, there is no ground fault current, and the DC meter 3 is not fixed em. When one of the phases of the network is shorted to earth, a path is created for direct current from the source through meter 3, primary windings of transformer 1, network 2, ground fault location, common bus 5. At the same time, the secondary windings of transformer I across the open triangle terminals is a voltage of zero in consequence, which is transformed according to a transformer 6 and recr 04. A rectifier 7 is applied. The DC voltage at the rectifier output is counter to the voltage of the compensation current source 10, which, together with the variable resistor 11, serves to set the meter 3 to zero. and compensation source 10, as the voltage of the zero sequence increases, linearly decreases to zero, which provides automatic compensation of the zero meter when the transition resistance in the place of the circuit changes and on the ground. Since the return path of the current lies through the common busbar 5, which has a low longitudinal resistance (0.004–0.006 ohm / km), the ohmic resistance of the three-wire network 2 system is decisive for the direct current of source 8, and the meter scale is graduated in terms of distance to points zamzhani to the ground. Measurement accuracy is provided by automatic zero compensation depending on the zero-sequence voltage, as well as through the use of a DC source 8, the direct current of which in the ground fault location is superimposed on the sinusoidal current of the industrial frequency. In addition, the presence of a common bus 5, laid along the network 2, eliminates the error due to changes in the conductivity of the soil and reduces the error from the transient resistance at the location of the s Ikani to earth, t, k, the input ohmic resistance of the pipeline (t, i. Earth) is practically zero. The invention The device for determining the location of a ground fault in networks with insulated neutral, containing a meter, a three-phase voltage transformer, the primary windings of which are connected according to the star circuit and connected to the corresponding phases of the monitored network, and the secondary windings are connected according to the open triangle scheme, different that, in order to increase