SU116004A1 - Test method for electric power equipment vanishing devices - Google Patents

Description

For testing electric power equipment tans without disconnecting them from the mains, methods are based on measuring the resistance of the nets - the seeding wire (neutral) - the secondary winding of the power transformer.

The described method differs from the known ones in that the tests measure the zero-sequence resistance of said loop. In this case, it is not necessary to perform a preliminary check for the absence of breaks or high transient resistances in the vanishing wiring and to connect the measuring devices under voltage. All of this makes it easier to carry out measurements under operating conditions and increases the safety of work.

FIG. 1, 2 and 3 depict test circuits for zaning devices according to the proposed method.

The test of a zaning device of an electrical installation / pro1; is started by measuring the zero-sequence resistance of a loop consisting of a line 2, a neutral-conducting neutral wire 3 and the winding of a power supply transformer 4 devices can be used grounding meters 5 (Fig. 1 and 2), included in the network through two asymmetry.

The voltage circuit asymmetry is performed as active resistances 5 (Fig. 1) no more than 300 oz per phase, the adjustable part of which is about 20%. At the same time, the asymmetry zero point potential is shifted within 7% of the mains phase voltage, which satisfies the practical need in all cases; the control of the neutral potential adjustment is carried out by the indicator 7; vibration Nb 116004

or voltmeter type. The asymmetry of the current circuit of the device is made of three unregulated capacitances 8.

The windings of three-phase electric motors 9 (Fig. 2) of any power can also serve as asymmetries, since the total resistance of the asymmetry is very small.

The measurement of the zero-sequence resistance of the loop "line - zapping wire - transformer can be optional, also can be verified using an ammeter 10 and a voltmeter // (Fig. 3). A voltmeter // is connected to the neutral of the adjustable asymmeter in series with the low-pass filter 12. The total resistance of the voltage circuit should provide a minimum measurement limit for the voltmeter from 1 to 1.5 volts and should not change when the asymmeter is adjusted. Therefore, three compensating resistors 13 are connected in series with the voltmeter 11, the magnitude of which varies inversely proportional to the adjustable resistance of the asymmetric arms.

The current circuit includes a resistance 14 with stepwise adjustment of the current to 10 a. With fully inserted resistance, the voltage on the probe does not exceed 3 volts, which ensures the safety of the preparatory work. The operability of the measuring circuit and the attachment of the probe to the object under test, in the absence of an open circuit in the wiring, are monitored by a voltmeter. // After the probe is connected and the asymmeter is adjusted, the load current increases. The load resistance stages are calculated so that at any value of the zeroing resistance, the potential of the probe is no more than 40 volts. The contacts of voltage relay 15 included in the asymmeter neutral are entered into the circuit. The relay is triggered for 1-2 periods when a potential above 40 V appears on the probe, ensuring the full safety of the operating personnel and the protection of measuring instruments during the test.

Subject invention

A method of testing electrical power equipment vanes without disconnecting them from the network, which consists in measuring the loop resistance of the line - zeroing wire (neutral) - the secondary winding of a power transformer, characterized in that, to simplify the measurement process, the zero sequence resistance specified loops.