SU552571A1 - Apparatus for testing current transformers in transient conditions - Google Patents

Description

one

The invention relates to testing of electrical signals and can be used to determine the potential of current transformers in transient conditions during certification tests at manufacturing plants or test centers.

Devices are known that simulate a transient short circuit current in which two components are applied: periodic and aperiodic. The periodic component is formed by a power transformer, and the aperiodic component is switched on by means of a different current throttle in the primary circuit of the current transformer under test 1.

However, such a device allows for the testing of low-power electrical apparatus.

The closest to the proposed technical entity is a device comprising a periodic current driver consisting of a percussion generator and a power system, as well as switching devices, percussion transformers of inductance, a communication transformer, current sensors and measuring devices 2.

However, due to the limited power of the device for testing current transformers in transient conditions, they are produced at insignificant short-circuit currents

(12-18 kA) and constant vsmepi of their attenuation (up to 0.08 s).

Since the registration of the operation of current transformers in transient conditions is performed

PA photosensitive material, or storage devices, the analysis of the information obtained is difficult and is performed with errors, and often reaches 20% or more.

The purpose of the invention is to expand the working range of test currents and to measure accuracy.

This is achieved by the fact that a device for testing current transformers in transient conditions, containing an operating frequency current driver, connected to the primary circuit of the transformer under study, the secondary circuit of which includes a load,

the current sensor and ammeters connected to the circuits of the latter are equipped with direct current generators with ammeters connected in series to the secondary circuit of each stage of the transformer under study, the current transformer with two counter-connected primary windings being used as the current sensor, one of which is included in secondary circuit of the transformer under study,

and a friend through a choke, a variable reznetor and an ammeter into the circuit of a DC source.

The drawing is a schematic diagram of the proposed device for testing a three-stage current transformer.

The device contains an operating frequency driver 1 connected to the primary circuit of transformer 2, load 3, current sensors 4, 5, ammeters 6-8 included in the circuits of direct current 9-I, ammeters 12, 13 and direct current source 14 connected to the additional primary winding of the measuring transformer through an ammeter 15, a variable resistor 16 and a choke 17.

Transformer tests in transient conditions are performed in the following order. By the ammeters 6-8 from the formers 9-11, in all steps of the current transformer under test, direct currents are set, the magnitude and polarity of which are determined by calculating the aperiodic magnetization current for a given current transformer. The periodic current of the operating frequency, determined by the passport data of the current transformer under test, is set from the driver 1 connected to the primary circuit of transformer 2. The signals from the secondary windings of sensors 4, 5, proportional to the flowing periodic currents: primary and magnetization of the current transformer being tested, can be measured with using ammeters 12, 13, or other high-speed current meters, followed by issuing information to the digital printing device, if the test time is limited by thermal oh transfomers resistant current is insufficient for relieving ammeters.

When used as a sensor 5 of a measuring current transformer, through an additionally introduced primary winding connected to source 14, a constant current equal in magnitude and opposite to the direct current flowing through the main winding is established using an ammeter 15.

The magnitude of the inductive resistance of the choke is chosen from the condition of ensuring the required accuracy of the measuring current transformer.

The total error of the current transformer under test in transient conditions is determined by the readings of ammeters 12, 13 from the expression

S-iiL 1QO JO / A 2

where / 13 is the current on the ammeter 13; - current on the ammeter 12.

When current transformers are tested with a number of transformation steps not equal to three, the measuring circuit remains the same, and the number of drivers must be

10 is equal to the number of stages of transformation.

The use of direct current drivers in this device allows the test transformer to create a steady state mode similar to the transient

15 any given point in time, which makes it possible to obtain quantitative values of errors in a wide range of load variations, primary currents and constant damping times using electric measuring instruments, using simple equipment and reliable equipment at low capital expenditures.

Claims (2)

1. An apparatus for testing current transformers in transient conditions, comprising an operating frequency current driver connected to a primary circuit of a transformer under study, the secondary circuit of which includes a load, current sensors and ammeters connected to the latter circuits, characterized in that range of test currents and an increase in measurement accuracy, it is equipped with direct current formers with ammeters connected in series in the secondary circuit of each stage of the test 0 transformer. 2. The device according to claim 1, characterized in that a current transformer with two counter-connected primary windings is used as a current sensor, one of which is connected to the secondary circuit of the transformer under investigation, and the other through a choke, variable resistor and ammeter to the source circuit direct current. 0 Sources of information taken into account in the examination: 1.Avt. St. USSR № 474073, cl. H 02 H 11/00, 16.10.72. 2. Avt. St. USSR number 390478, cl. G 01R 31/02, 18.03.71.