CN102520382A - Method for detecting half-wave current transformation error of current transformer - Google Patents

Abstract

A detection method for the transformation error of a current transformer under half-wave current, characterized in that the method uses two diodes with a forward conduction current greater than the rated current of the current transformer on the basis of the existing current transformer verification circuit , one positive and one negative are connected in series with two test current transformers respectively to form a positive half-wave current transformer and a negative half-wave current transformer, and two symmetrical half-wave current transformers are connected in parallel to form a full-wave current transformer The error is measured by the transformer, and the measured error is the error of the half-wave current transformer. The present invention utilizes the current transformer verification equipment such as the existing AC current booster, the standard current transformer, the transformer calibrator, the load box, etc., and can realize the detection of the conversion error of the current transformer under the half-wave current. The method has the advantages of simple, economical, scientific, practical, strong operability and low cost. The invention is suitable for the technical field of measurement accuracy measurement of the anti-DC component of the current transformer.

Description

Method for detecting half-wave current transformation error of current transformer

the

technical field

The present invention relates to a detection method for the transformation error of a current transformer under half-wave current, which belongs to the technical field of detection of current transformers for electric power metering.

Background technique

Different models and different batches of current transformers produced by different manufacturers have different magnetic properties of iron cores, and the influence of residual magnetism on current transformer errors is also different. One possibility of strong residual magnetism in the current transformer in operation is that there is a DC component in the primary current, which saturates the iron core magnetically, resulting in a decrease in the equivalent magnetic permeability of the iron core, and the error will significantly move to the negative direction. The influence of the DC component on the error of the current transformer can be studied through the conversion error of the current transformer under the half-wave current. At present, the detection equipment used for current transformers at home and abroad are all AC full-wave types. The verification circuit diagram of the conventional voltage transformer verification wiring diagram stipulated in JJG1021-2007 "Current Transformer Verification Regulations" is shown in Figure 1, but it cannot The transformation error of the current transformer under the half-wave current is detected.

In order to solve the transformation error detection of the current transformer under the half-wave current, it is of great significance to study a detection method of the transformation error of the current transformer under the half-wave current to change the above situation.

Contents of the invention

The purpose of the present invention is, in order to solve the problem that the detection equipment used for current transformers at home and abroad are all AC full-wave types, and the conversion error of current transformers under half-wave current cannot be detected, how to use existing equipment to detect current Transformation errors of transformers under half-wave currents, the invention provides a method for detecting transformation errors of current transformers under half-wave currents.

The technical solution of the present invention is, on the basis of the existing current transformer verification circuit, use two diodes whose forward conduction current is greater than the rated current of the current transformer, and one forward and one reverse are respectively connected in series with two test current transformers, Form a positive half-wave current transformer and a negative half-wave current transformer, connect two symmetrical half-wave current transformers in parallel, combine them into a full-wave current transformer for error measurement, and the measured error is the error of the half-wave current transformer .

The main equipment used in the detection method of the transformation error of the current transformer under the half-wave current is: a standard current transformer (0.02 level), a transformer calibrator (2 level), a current load box (3 level ), 2 diodes with a forward conduction current greater than the rated current of the current transformer.

The wiring of the detection of the conversion error of the current transformer under the half-wave current is shown in the figure, that is, the secondary coils of the two tested current transformers CT _X1 and CT _X2 are connected in parallel, and one end is connected to the differential current test of the transformer calibrator Terminal K, one end is connected to the working current test terminal T _X of the transformer calibrator through the current load box Z; 2 diodes D ₁ and D ₂ whose forward current is greater than the rated current of the current transformer, one positive and one negative respectively connected to the two The current transformers of the test product are connected in series, the positive pole of D ₂ is connected to one end of the secondary coil of the current transformer under test CT _X2 , the negative pole of D ₂ is connected to one end of the current booster; the negative pole of D ₁ is connected to one end of the secondary coil of the current transformer under test CT _X1 , D ₁ The positive pole and D ₂ are connected in parallel to the current booster; one end of the primary coil of the standard transformer CT ₀ is connected to the current booster, and the other end is connected to the parallel end of the primary coil of the two tested current transformers; the secondary coil of the standard transformer CT ₀ One end of the secondary coil is connected to the working current test terminal T ₀ of the transformer calibrator, and the other end is connected to the parallel terminals of the secondary coils of the two tested current transformers; the other differential current test terminal of the transformer calibrator is D is grounded.

According to the requirements of the relevant regulations of current transformers, the steps are as follows:

(1) Select the upper limit load;

(2) Increase the current according to the requirements of the regulations, and test the upper limit load error of the current transformer at 1%, 5%, 20%, 100%, and 120% of the rated current;

(3) Reduce the current to 0;

(4) Select the lower limit load;

(5) Increase the current according to the requirements of the regulations, and test the lower limit load error of the current transformer at 1%, 5%, 20%, and 100% of the rated current;

(6) Reduce the current to 0;

(7) Complete the verification of the current transformer.

The beneficial effects of the present invention are that, when detecting the conversion error of the current transformer under the half-wave current, two diodes whose forward conduction current is greater than the rated current of the current transformer are used, one forward and one reverse, to be connected in series with two test current transformers respectively, Form a positive half-wave current transformer and a negative half-wave current transformer to form a detection circuit for the transformation error of the current transformer under the half-wave current, and use the existing AC current booster, standard current transformer, and transformer calibration Current transformer verification equipment such as instrument and load box can realize the detection of transformation error of current transformer under half-wave current. The method has the advantages of simple, economical, scientific, practical, strong operability and low cost.

The invention is suitable for the technical field of measurement accuracy measurement of the anti-DC component of the current transformer.

Description of drawings

Figure 1 is a conventional current transformer detection wiring diagram;

Fig. 2 is a half-wave current transformer error detection wiring diagram;

Symbols in the figure: CT ₀ is the standard current transformer; CT _x is the current transformer of the tested product; CT _x1 is the current transformer of the #1 tested product; CT _x2 is the current transformer of the #2 tested product; Z is the current mutual inductance D ₁ is the #1 diode; D ₂ is the #2 diode; T ₀ and T _X are the working current test terminals of the transformer calibrator; K and D are the differential current test terminals of the transformer calibrator.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

Step 1: Prepare the test equipment

One standard current transformer (level 0.02), one transformer calibrator (level 2), one current load box (level 3), two diodes with forward conduction current greater than the rated current of the current transformer, two The current transformer under test.

Step 2: Wiring according to the wiring method in Figure 2;

Connect the secondary coils of the two tested current transformers CT _X1 and CT _X2 in parallel, one end is connected to the differential current test terminal K of the transformer calibrator, and the other end is connected to the working current test of the transformer calibrator through the current load box Z Terminal T _X ; 2 diodes D ₁ and D ₂ with a forward conduction current greater than the rated current of the current transformer, one forward and one reverse connected in series with the two test current transformers respectively, and the positive pole of D ₂ is connected to the tested current transformer CT _X2 One end of the secondary coil, the negative pole of D ₂ is connected to one end of the current booster; the negative pole of D ₁ is connected to one end of the secondary coil of the tested current transformer CT _X1 , the positive pole of D ₁ and D ₂ are connected in parallel to the current booster; the primary coil of the standard transformer CT ₀ One end of the coil is connected to the current booster, and the other end is connected to the parallel end of the primary coil of the two tested current transformers; one end of the secondary coil of the standard transformer CT ₀ is connected to the working current test end T ₀ of the transformer calibrator, and the other end is Connect with the parallel terminals of the secondary coils of the two tested current transformers; the other differential current test terminal D of the transformer calibrator is grounded.

Step 3: Verify the current transformer under test according to the requirements of JJG1021-2007 "Current Transformer Verification Regulations";

(1) Select the upper limit load;

(2) Increase the current according to the requirements of the regulations, and test the upper limit load error of the current transformer at 1%, 5%, 20%, 100%, and 120% of the rated current;

(3) Reduce the current to 0;

(4) Select the lower limit load;

(5) Increase the current according to the requirements of the regulations, and test the lower limit load error of the current transformer at 1%, 5%, 20%, and 100% of the rated current;

(6) Reduce the current to 0;

(7) Complete the verification of the current transformer.

Claims (2)

1. a current transformer is in half-wave current down conversion error detecting methods; It is characterized in that; Said method is used the diode of 2 forward conduction electric currents greater than the current transformer rated current on the basis of existing current transformer calibrating circuit, one positive one instead connects with two bench teat article current transformers respectively; Form a positive half-wave current transformer and a negative half-wave current mutual inductor; Half-wave current mutual inductor parallel connection with two symmetries is combined into the full-wave electric current mutual inductor and carries out error measure, records the error that error is the half-wave current mutual inductor.

2. current transformer according to claim 1 is characterized in that in half-wave current down conversion error detecting methods said calibrating circuit is tried current transformer CT with two _X1, CT _X2Secondary coil parallel connection, the difference testing current end K of a termination mutual-inductor tester, an end meet the working current test lead T of mutual-inductor tester through current capacity case Z _X2 forward conduction electric currents are greater than the diode D of current transformer rated current ₁, D ₂, one positive one instead connects D with two bench teat article current transformers respectively ₂Positive pole connects by examination current transformer CT _X2Secondary coil one end, D ₂Negative pole connects current lifting device one end; D ₁Negative pole connects by examination current transformer CT _X1Secondary coil one end, D ₁Positive pole and D ₂And ally the communists and connect current lifting device; Standard mutual inductor CT ₀Primary winding one termination current lifting device, the other end and two are linked by examination current transformer primary winding parallel connected end; Standard mutual inductor CT ₀The working current test lead T of secondary coil one termination mutual-inductor tester ₀, the other end and two parallel connected end by examination Current Transformer Secondary coil link; Mutual-inductor tester another difference testing current end D ground connection.

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