SU1620966A1 - Method of checking current transformers - Google Patents

Abstract

The invention can be used when checking current transformers (CTs), the primary windings of which are connected to the power supply circuit of the objects. The purpose of the invention is to increase the reliability of energy supply to consumers during verification. Compensate for the load current in the primary winding of the CT, then pass an additional current through the primary winding of the CT and, by changing the current in the secondary winding, conclude that the CT is suitable for the transformation ratio. Then, additional current is removed from the primary winding of the TT, the load of the secondary winding of the TT is disconnected, a voltage is applied to it and, based on the current value, it concludes that there are no short-circuited turns in it. 1 il.

Description

The invention relates to electrical measuring equipment and can be used when checking current transformers (CTs), the primary windings of which are connected to the power supply circuit of objects up to 0.4 kV and are under load.

The aim of the invention is to improve the reliability of the power supply to consumers during verification.

The drawing shows the functional scheme of the device, explaining the proposed method.

The essence of the method is as follows.

Compensate the load current in the primary winding of the current transformer, then pass the auxiliary current through the primary winding and, by changing the current in the secondary winding, conclude that the current ratio is suitable for the transformer, then the additional current from the primary winding is removed, the secondary winding is disconnected current transformer, they supply voltage to the secondary winding and, based on the current of the secondary winding, they conclude that there are no short-circuited turns in it.

The device contains a current transformer 1, a compensating current source 2, an additional current source 3 and voltage, which is connected with a switch 4 to the primary winding of a current transformer 1 flexo using a switch located in source 3, to its secondary winding through a measuring device 5, with load disconnection 6 (electric meter) with key 7.

The current transformer 1 under test is connected to the power supply of the plant and is under load, its secondary winding is connected to an electric meter 6. Consistently with meter 6, a measuring device 5 is connected, which is a microammeter, which is bounded by a set of 50 to 10A and key 7.

The primary winding of the current transformer 1 is connected via clamps to a compensation current source 2, which consists of autotransformers 8 and 9 and a load transformer 10. Autotransformer 8 can be connected to a lagging or leading phase, which is also controlled by the voltage on autotransformers 8 and 9 allows you to compensate for the load current flowing through the primary winding of the transformer

Current, in magnitude and phase.

Additional source 3 of current and voltage consists of autotransformer

11, a transformer 12, a switch 13, and two measuring devices 14 and 15. The autotransformer 11 controls the amount of current and voltage. Switch 13 applies either voltage to secondary winding

transformer 1, or the current from the load transformer 12 to the primary winding of the current transformer 1. In the first case, the key 7 disconnects the load in its secondary winding, and in the second case, the key 4

connect the output of the load transformer 12 to the primary winding of the current transformer 1. The measuring device 14 shows the additional current supplied to the primary winding of the transformer

1 current. The measuring device 5 records the amount of current in its secondary winding. The measuring device 15 (voltmeter) serves to monitor the voltage supplied to the secondary winding of the current transformer 1.

The device works as follows

Autotransformers 8–10 to 3 phase networks are connected, and the autotransformer 9 is connected to the phase with the current transformer 1 of the same name, the autotransformer 8 is connected to the lagging phase, if the loads of the consumer are inductive in nature, or to the leading

phase if the load is capacitive in nature. The autotransformer 11 is connected to the free phase to eliminate the effect of additional current on the compensation of the load current. To the primary winding of the transformer

1 is connected with the help of chain clips from the load transformer 10, the measuring device 5 and the key 7 are included in the secondary winding of the transformer 1.

I adjust autotransformers 8 and 9,

the current in the secondary winding is reduced to the minimum, and the primary current flowing through the current transformer 1 is compensated. Switch 13 is set to position G,

key 4 is locked, and on the measuring device 14 with the help of an autotransformer

I1 sets the required current in the primary winding of the transformer 1, the measuring device 5 is fixed

the current in its secondary and is calculated by CTT t-h

Then key 4 disconnects the current from the additional source 3 of the current and voltage.

After that, the key 7 disconnects the secondary load 6, the secondary winding of the current transformer 1 through the measuring device 5 connects the ends from the position of the switch 13. The switch 13 is switched to the tf-th position, and the voltage from the transformer 11 is applied to the secondary winding of the current transformer 1. According to the reading of the measuring devices 5 and 15, the absence of short-circuited turns in the secondary winding of the current transformer 1 is determined.

Thus, the proposed method makes it possible to test transformers without shutdown, in the workplace under load, which is especially important in cases where the de-energization of objects is undesirable or even unacceptable even for a short time.

Claims (1)

Claim method The test of current transformers, including the supply of current to its primary winding and the measurement of current in the secondary winding, characterized in that, in order to improve the reliability of the power supply to consumers during the test, they compensate the load current in the primary winding of the current transformer, then pass additional current through the primary the winding and the change in current in the secondary winding make a conclusion about the suitability of the current transformer on the transformer ratio, then the additional current from the primary winding removed, switch off the load current of the secondary winding of the transformer is supplied to the voltage on its secondary winding and conclude the absence korotkozamk- mentioned it turns on the secondary winding current magnitude.