SU1234795A1 - Device for determining magnetizing characteristics of current transformers - Google Patents

Abstract

The invention relates to the testing of electrical equipment, in particular to the testing of measuring current transformers during their installation and operation. The purpose of the invention is to increase the performance and accuracy of the determination of the magnetization characteristics. It is achieved by programmatically setting the current values at the control points of the characteristic and automatically fixing the corresponding voltage values at these points, as well as by varying the amplitude values of the current and average voltage values. The device contains an adjustable source of alternating voltage 1, an exemplary resistor 2, a test magnetizing winding of a current transformer 3, a voltage divider 4, a large-scale amplifier 6, a software unit 9 having a memory block 14 and a code-analog converter 15, a recording unit tO, a command unit 11. To achieve the set goal, the device additionally includes: a measuring voltage converter 5 with a detector 12 of the arithmetic mean of the input voltage and a converter 13 analog-code at the output, amplitude The specific detector 7 and the comparator 8. 2. f-ly, 2 ill. SL C

Description

The invention relates to the field of electrical engineering, in particular to the testing of electrical equipment, in particular to the testing of measuring current transformers during their installation and operation.

The removal of magnetization characteristics is the main test of the health and suitability of current transformers for operation. This characteristic is the dependence of the voltage at the terminals of the secondary winding of the current transformer on the current in it and can be presented in the form of a table containing voltmeter and ammeter readings at the control points of the characteristic, or as a curve.

The circuit of the invention is to improve the performance and accuracy of the determination of the magnetization characteristics by programmatically setting the current values at the control points of the characteristic and automatically fixing the corresponding voltage values at these points, as well as measuring the amplitude values of the current and average voltage values.

Fig. 1 shows the block diagram of the device; Figure 2 shows the temporary digrams of his work.

The device (Fig. 1) contains an adjustable source of alternating voltage 1, to the output of which, through an exemplary resistor 2, the magnetizing winding of the test current transformer 3 is connected. The terminals of the last are connected to the input of a voltage divider 4, the output of which is connected to the input of the measuring voltage converter 5, and to the terminals of a common- resistor 2 resistor - to the input of a large-scale amplifier 6, to an output connected to the input of an amplitude detector 7. Vio4 is the input of a comparator 8, the second input of which is connected to the analog output of the software block 9, the digital output of which is connected to the first signal input of the recording unit 10 connected by the second signal input to the output of the measurement transform Ovatel 5 voltage, and the control input - with the output of the comparator. 8 i The command block 11 is used to control the software 9 with a voltage divider 4 and a large-scale amplifier 6. Measuring transducer

five

0

five

voltage equalizer 5 comprises the arithmetic mean voltage detector 12 at the input and converter 13 analogue — the output code. Program block 9 contains a memory block 14, the output of which is the digital output of a program block, and converter 15 is an analog code, the Kojroporo input is connected to the output of memory block 14, and the output is an analog output of program block 9. The preferred implementation of the controlled source 1 voltage is its execution in the form of a controlled, sinusoidal voltage generator of industrial frequency, containing a generator of 16 pulses, the output connected to the first input element And 17, the second input of which is connected to the output A comparator 8 and one output are connected to the input of a pulse counter 18, the output of which is connected to the input of the converter. 19 Code — AC voltage, which is a transformer, to the switch of the secondary windings. The device works as follows.

Using the command unit 11, the operator enters data on the type of current transformer being tested, according to which the voltage transfer factors of voltage divider 4 and scale are automatically set.

5 of the amplifier 6. At the time t, the number corresponding to the current at the first control point of the magnetization characteristic for this type of current transformer, the value of which remains unchanged until time tj (signal figa). This signal is fed to the first signal input of the recording unit 10, and after being converted to analog form in converter 15, to the second input of the comparator 8. The voltage of the adjustable source 1 starts to increase and through the reference resistor 2 and the magnetizing winding of the current transformer 3 passes current. At the time tj, the voltage drop from this current at resistor 55, amplified by the scale amplifier 6, reaches the value at which the amplitude value at the output of the latter, selected by amplitude 0

0

The detector 7 (Fig. 26) and receiving the first input of the comparator 8 is compared with the voltage at its second input; the comparator 8 causes the command (Fig. 2b) to register the number 10 input to its signal inputs. In this case, from the second signal input, the average value of the voltage on the control winding of the current transformer 3 is recorded, coming from the output of the measuring voltage converter 5 (Fig. 2d). After registration of the current and voltage at the first control point of the magnetization characteristic, the unit 11 at the time tj causes the command to retrieve the current value from the second memory to the second test point. The voltage of the adjustable source 1 increases, the second control point is fixed, the values of current and voltage in it are recorded at time t and at time t a command to test the third control point is received, etc.

When performing the adjustable voltage source 1 in accordance with Fig. 1, the pulse counter 18 is filled with pulses from the generator t6 through the element AND 17 until the number in the counter 18 converted to the AC voltage by the converter 19 reaches the value which triggered the comparator 8 (figv), after which the voltage rise stops before issuing a command to work out the next control point. After registering the current and voltage at the last control point, the operator has all the necessary information about the magnetization characteristic in a form suitable for comparison with similar characteristics.

The device command block may contain a switch for selecting programs recorded in the device memory for the 16 most common standard sizes of current transformers and for selecting 8 control points.

The registration unit may contain 55 two four-digit seven-segment LED indicators.

Claims (2)

1. Device for determining the magnetization characteristics of current transformers, containing an adjustable AC voltage source, to the output of which a magnetizing winding is connected to an output, a voltage divider whose input is connected to magnetizing winding terminals, an amplifier whose input is connected to a sample resistor, and a unit registration, characterized in that, with entire performance, accuracy of magnetization characterization, amplification is additionally introduced into the device A difficult detector, a measuring voltage converter and a comparator, as well as serially connected command and program blocks, the input of the amplitude detector connected to the output of the amplifier and the output to the first input of the comparator, the second input of which is connected to the analog output of the program block the input of the registration unit, with the second input of the command unit and the input of an adjustable source of alternating voltage, the first signal input of the registration unit is connected to the digital output of the software block minute, with a second output transducer voltage, which input is connected to the output of the voltage divider, 2. The device according to claim 1, characterized in that the adjustable source of alternating voltage is made in the form of a series-connected pulse generator element I, a pulse counter and a converter code — the alternating current voltage whose output is connected to the output of the adjustable alternating voltage source, and the second input element And connected to the output of the comparator 3, the device according to claim 1, wherein the voltage measuring transducer is made in the form of a series-connected average voltage detector and an analogue-code converter. 3 t2 tj tifts t, t2 tj tif ts 0Ut.Z t5