*Chapter Device characteristics and parameters

LYFA-5000Transformer comprehensive tester It is a new generation of innovative testing equipment developed on the basis of the traditional transformer volt ampere characteristic transformation ratio polarity comprehensive testing instrument based on voltage regulator, booster, and current regulator. After extensively listening to user opinions, conducting extensive market research, and conducting in-depth theoretical research, it has been developedCTThePTTesting instruments. The device adopts high-performance technologyDSPandFPGAThe manufacturing process ensures stable and reliable product performance, complete functions, high degree of automation, high testing efficiency, and is at a high level in China. It is a professional testing instrument used for transformers in the power industry.

Capacitive voltage transformer tester

1.1 Main technical features

1. Fully functional, meeting various needsCT(such as protection, measurement, etc.)TPThe excitation characteristics (i.e. volt ampere characteristics), transformation ratio, polarity, secondary winding resistance, secondary load, ratio difference, and angle difference of the class can also be used for various testing requirementsPTTesting of excitation characteristics, transformation ratio, polarity, secondary winding resistance, and ratio difference of electromagnetic units.
2. On site calibration of current transformers does not require standard current transformers, current transformers, load boxes, voltage regulation control boxes, or high current wires. It uses extremely simple testing wiring and operation to achieve the calibration of current transformers, reducing work intensity and improving work efficiency, making it convenient to carry out on-site transformer calibration work.
3. Measurable ratio difference and angle difference, with a larger ratio difference and an allowable error of ±0.05%The allowable error for large angular differences is ±2minCan be carried out0.2SThe measurement range for the transformation ratio of the current transformer is1~40000.
4. Based on the frequency conversion method to test the CT/PT volt ampere characteristic curve and 10% error curve, it can output an AC voltage of only 180V and an AC current of 12Anms (peak value of 36A), but can handle CT tests with inflection points as high as 60KV.
5. Automatically provide inflection point voltage/current10%(5%)Error curve, accuracy limit coefficient（ALF）Instrument security factor（FS）Quadratic time constant(Ts)Residual magnetism coefficient(Kr)Saturated and unsaturated inductors, etcCTThePTParameters.
6. Testing meetsGB1208（IEC60044-1）TheGB16847(IEC60044-6)TheGB1207Wait for various transformer standards and automatically select which standard to test based on the type and level of transformer.
7. Testing is simple and convenient, one click completionCTDirect resistance, excitation, transformation ratio, and polarity testing, in addition to load testing,CTAll other tests use the same wiring method.
8. Full Chinese dynamic graphical interface, wiring and parameter setting can be completed without referring to the manual: dynamic display of parameter settings, automatically displaying relevant parameters based on the currently selected test project; Dynamically display the help wiring diagram, and display the corresponding wiring diagram based on the currently selected test project.
9. 5.7Inch graphic transparent and reflectiveLCDClear visibility under sunlight.
10. Using a rotating optical mouse for operation, it is simple, fast, convenient, and easy to master.
11. The panel comes with a printer that can automatically print the generated test report.
12. The test results are availableUDisk export, program availableUDisk upgrade, convenient and fast.
13. The device can store1000Group test data, not lost in case of power failure.
14. Equipped with backend analysis software, it facilitates the saving, conversion, and analysis of test reports, and can be used for comparing, judging, and evaluating experimental data.
15. Easy to carry, device weight<9Kg.

Capacitive voltage transformer tester

1.2 Device panel description

The structure of the device panel is shown in the diagram on the right, with wiring terminals from left to right:

·Red and BlackS1TheS2Terminal: Test power output

·Red and BlackS1TheS2Terminal: Output voltage backtesting

·Red and BlackP1TheP2Terminal: Inductive voltage measurement terminal

·LCD screen: Chinese display interface

·Micro printer: printing test data and curves

·Rotate mouse: Enter numerical values and operation commands

1.3 Main technical parameters

Chapter 2 User interface and operationmethod

2.1 Current Transformer Test

inparameterInterface, using Rotate the mouseSwitch cursor totypeColumn, select the type of transformer asCT.

2.1.1Test wiring

The experimental wiring steps are as follows:

*Step: According to the table2.1describedCTExperimental project description, according to the diagram2.1Or picture2.2Wiring (for various structures)CT, can refer to the appendixDThe actual wiring method described.

table2.1 CTExperimental project description

picture2.1 CTWiring methods for direct resistance, excitation, and variable ratio tests picture2.2 CTWiring method for secondary load test

Step 2: SameCTOther windings are open circuited,CTOne end of the primary side should be grounded, and the equipment should also be grounded.

Step 3: Connect the power and prepare the parameter settings.

2.1.2Parameter Settings

The interface for setting experimental parameters is shown in the figure2.3.

picture2.3 Basic parameter setting interface

The parameter setting steps are as follows:

use Rotate the mouse Switch the cursor and select the test item to be conducted. When the cursor stays on a certain test item, the screen displays the parameter settings related to that test item; When the cursor moves away from the test item, the screen displays the wiring diagram corresponding to the selected test item.

The parameters that can be set are as follows:

（1）Number: Enter the number of this experiment for easy management and retrieval of printing and saving.

（2）Rated secondary currentThe rated current on the secondary side of a current transformer is generally1Aand5A.

（3）Level: The level of the tested winding, forCThavePTheTPYMeasurementPRThePXTheTPSTheTPXTheTPZwait8One option.

（4）Current temperature: The temperature of the winding during testing, which can generally be input as the temperature during testing.

（5）Rated frequency: Optional values are:50Hzor60Hz.

（6）Large test current: generally can be set as the rated secondary current value, forTPYlevelCTGenerally, it can be set as2Twice the rated secondary current value. ForPlevelCTAssuming it is5P40The rated secondary current is1ASo the large test current should be set5%*40*1A=2AAssuming it is10P15The rated secondary current is5ASo the large test current should be set10%*15*5A=7.5A.

If users want to see the following results, they need to set them accuratelyBasic parameters (recommended for user settings).

（1）Turn ratio error, ratio difference, and phase difference

（2）Accurately calculated ultimate electromotive force and its corresponding composite error

（3）Actual measured accurate limit factor, instrument safety factor, and symmetrical short-circuit current multiple

（4）Measured transient area coefficient, peak instantaneous error, and quadratic time constant

For different levels ofCTThe parameter settings are also different, as shown in the table2.2.

table2.2 CTparameter description

Step 5: Select the one on the rightstartButton for testing.

2.1.3Test results

experimentresultPage,The interfaces are shown in the figure2.4.

For different levels ofCTThe test results are also different from the selected test items, as shown in the table2.3.

table2.3 CTTest result description

2.2 Voltage Transformer Test

inparameterInterface, using Rotate the mouseSwitch cursor totypeColumn, select the type of transformer asPT.

2.2.1Test wiring

The experimental wiring steps are as follows:

*Step: According to the table2.4describedPTExperimental project description, according to the diagram2.7Or picture2.8Connect the wires.

table2.4 PTExperimental project description

Step 2: SamePTOther windings are open circuit.

Step 3: Connect the power and prepare the parameter settings.

2.2.2Parameter Settings

PTofThe interface for setting experimental parameters is shown in the figure2.5.

The parameter setting steps are as follows:

use Rotate the mouse Switch the cursor and select the test item to be conducted. When the cursor stays on a certain test item, the screen displays the parameter settings related to that test item; When the cursor moves away from the test item, the screen displays the wiring diagram corresponding to the selected test item.

The parameters that can be set are as follows:

（1）Number: Enter the experimental test number.

（2）Rated secondary voltageRated voltage of the secondary side of the voltage transformer.

（3）Level: The level of the tested winding, includingPMeasurement, etc2One option.

（4）Current temperature: The temperature of the winding during testing can generally be inputted as the current temperature.

（5）Rated frequency: Optional values are:50Hzor60Hz.

（6）Large test voltage: The high power frequency equivalent voltage output by the equipment during the test.

（7）High test current: The large AC current output by the equipment during the test.

Step 4: Select the one on the rightstartButton for testing.

2.2.3Test results

experimentresultPage,As shown in the figure2.6.

For different levels ofPTThe test results are also different from the selected test items, as shown in the table2.5.

table2.5 PTTest result description

2.3self test page

The self-test interface is shown in the figure2.8With the help of a multimeter, the self-test function can be used to check whether the device is damaged and whether the measurement circuit is normal.

picture2.8 Self check testing interface

2.3.1Parameter Settings

The parameters required for self-test testing are shown in the following table:

table2.6 Self Testparameter

After setting the test current or test voltage, set the test frequency, and the device will output the voltage or current corresponding to the frequency, and display the actual voltage or current detected. After selecting the voltage, if the load is too small, it may cause the actual effective current value to be greater than5ADisplay overload information. After selecting the current, if the load is too large, it may cause the actual test voltage effective value to be greater than100VIt will also display overload information.

2.3.2Wiring method

·When selecting voltage testing, theS1Short circuit another oneS1，S2Short circuit another oneS2Measure with a multimeter in the voltage rangeS1andS2If the voltage between them matches the actual voltage, it indicates that the equipment can output voltage and the voltage measurement process is normal.

·During current testing, turn on the power supplyoutputofS1TheS2Terminal short circuit. Voltage backtestingS1TheS2Not accepted. Can be output inS1andS2Connect the current range of the multimeter in series. If the current measured by the multimeter matches the actual current, it indicates that the device can output current normally and the current measurement process is functioning properly.

2.4Function button

2.4.1Parameter page function buttons

(1)．System Tools

System ToolsInterface, as shown in the figure2.11In this interface, operations such as time verification and system upgrade can be performed. among whichdebugUsed for factory debugging,upgradeUsed for upgrading software interfaces.

(2)．help

（3）Print

Users can print the current test results, and this report can be used as the original record of on-site testing.

2.4.2Result page function buttons

(1)Excitation curve

in the figure2.4Or picture2.6On the measurement result page, selectExcitation resultsThe excitation curve interface will appear, as shown in the figure2.13：

(2)Excitation data

in the figure2.13On the excitation curve page, selectExcitation dataThe excitation data interface will be displayed, as shown in the figure2.14：

Three forms of excitation data can be displayed in the above figure:

1. Actual measurement: The voltage and current sequences captured during the instrument's voltage boosting process;
2. Rounding: The result of rounding the measured excitation data by current shows that,10mAPress below1mAIncremental10mA~100mAPress above5mAIncremental100mAPress above0.1AIncremental and rounded results facilitate data recording and comparison;
3. Can display excitation data for any current point;

(3)、5%、10%Error curve

Only transformers with protection level (including transient protection level) are available5%、10%The error curve and error data; inCTSelected asP/PR/PX/TPxThe transformer is shown in the test result diagram2.4In the interface, selectError resultsdisplay5%Error curve, as shown in the figure2.15：

in the figure2.15In the middle, you can also choose to display10%The error curve. Protecting transformers10%The error curve is10%The graphical display of error data has the same meaning, which means that the composite error of the transformer is not greater than10%The relationship curve between secondary load and overcurrent multiple.5%The error curve is that the composite error of the transformer is not greater than5%The relationship curve between secondary load and overcurrent multiple.

(4)、5%、10%Error data

in the figure2.15In the middle, chooseError datadisplay5%、10%The error data, as shown in the figure2.16As shown:

(5)Comparison and angle difference table

Only measuring grade transformers have comparison and angle difference result tables;inCTSet the selected winding level as "metering" for the transformer, and select "error" as the test itemOnly projects have comparison and angle difference tables. in the figure2.4 CTIn the test result interface, selectError resultsA comparison and angle difference table will appear, as shown in the figure2.17：

The above figure shows the ratio and angle difference tables of the transformer at rated load and lower limit load, respectively. The rated load isCTIn the settings page, the lower limit load is specified as25%Rated load.

Appendix record

A.Principle of low-frequency method testing

IEC60044-6Standards (corresponding to national standards)GB16847-1977）Claiming,CTThe test can be conducted at a frequency lower than the rated frequency to avoid the winding and secondary terminals being subjected to unacceptable voltage.

CTThe principle circuit for measuring volt ampere characteristics is shown in the following diagram:CTOpen circuit on the primary side, apply voltage from the secondary side, and measure the applied voltageVCompared to input currentIThe relationship curve. This curve is approximatelyCTThe excitation potentialERelated to excitation currentIThe relationship curve.

setCTExcitation winding at a certain excitation currentIThe excitation inductance at the time isLThe excitation impedance isZ, then:

V = I·Z

inductanceLImpedance relatedZThere is the following relationship between them:

Z = ω·L = 2 π f L

Then:V= I·2 π f L

As can be seen from the formula, in a certain excitation inductanceLVoltage applied at the timeVAnd frequencyfDirectly proportional relationship.

Assuming that whenf = 50HzTo achieve the excitation currentIxThe required voltage to be appliedVxfor2000V

Vx = Ix·2 π f L = 2000V，

If different frequencies are applied:

f = 50Hz，Vx＝2000V

f = 5Hz，Vx≌200V

f = 0.5Hz，Vx≌20V

It can be seen that it is necessary to makeCTThe basic principle of frequency conversion method is that by entering the same saturation level, the voltage required for applying a lower frequency signal can be significantly reduced.

It must be strictly noted that the required voltage is not linearly proportional to frequency, nor does it decrease proportionally with frequency. It is necessary to strictly follow the mathematical model of the transformer for complete theoretical calculations.

B. 10%Error Curve Calculation and Application Method

The error of current transformers is mainly due to the excitation currentThe existence of it causes secondary currentThe primary current converted to the secondary sideNot only are they not equal in numerical values, but also in phase, which causes errors in current transformers.

The ratio difference of current transformers is defined as:

Relay protection requires the primary current of the current transformerWhen equal to the large short-circuit current, the ratio difference is less than or equal to10%. When the ratio difference is equal to10%When, secondary currentThe primary current converted to the secondary sideAnd excitation currentThe following relationship is satisfied between them:

definitionMFor the multiple of the primary side short-circuit current,KFor the transformation ratio of current transformers, there are

among whichFor a large short-circuit current on the primary side

Rated current on the primary side

Rated current on the secondary side

10%Allowable high load impedance when there is a difference in ratioofThe calculation formula is:

Where:Impedance of the secondary winding of the current transformer

To induce electromotive force in the secondary winding of the current transformer,The relationship is described by the excitation characteristic curve.

According to the above formula, the multiple of the large short-circuit current can be obtainedAnd the allowable high load impedancedescribed10%Error curve (see figure)2.29）.

10%Application method of error curve:

Obtain a certainCTof10%After the error curve, it is also necessary to check the flow through itCTThe large short-circuit currentAnd thisCTImpedance of the circuit carried by the secondary sideThe large short-circuit current is often obtained during the setting calculation, which is theCTShort circuit current during severe short circuit in the high operating mode of the line, multiple of high current(Rated current). Secondary circuit impedanceCan be usedCTAMeasured by the device.

getLater search10%Error curve, if a point（）Below the curve, it meets the requirements, indicating that in severe short circuit situationsCTThe current conversion error is less than10%Otherwise, it will be greater than10%.

C. CTAUsed for various purposesCTThe actual wiring method

CTAforCTBasic wiring steps for testing (see figure)C.1）As follows:

（1）Use4mm²Connect the grounding terminal on the left side of the tester to the protective ground.

（2）ConnectCTOne terminal on the primary side and one terminal on the secondary side are connected to the protective ground.

（3）EnsureCTAll other terminals are disconnected from the power transmission line, and all other windings are open circuited.

（4）Use2.5mm²The red and black lines willCTConnect the secondary side to the tester“Output”S1andS2Jack, use1.2mm²The yellow and black lines willCTConnect the secondary side to the tester“Sec”ofS1andS2Jack, pay attention to connecting the two black wiresCTOn the same terminal that has been connected to the protective ground on the secondary side.

（5）Use1.2mm²The green and black lines willCTConnect the primary side to the tester“Prim”ofP1andP2On the terminal,P2Through the black line andCTConnect the terminal on the primary side to the protective ground.

（6）Check the wiring for accuracy and start testing.

1The tester is used on a delta connected transformer for testingCTThe wiring method for testing is shown in the diagramC.2As shown.

2Testing instrument for transformer bushingCTThe wiring method during testing is shown in the diagramC.3As shown.

Note:primary terminalH1Cannot be grounded, otherwise if both sides are grounded, the tester cannot obtain the correct result.

4The tester is in use for testingGIS（SF6）On the switchCTThe wiring method during testing is shown in the diagramC.4As shown.

Note:Disconnect all switches connected to the busbar and close the grounding switch.

D.Measurement principle of four terminal wiring

Apply and output a voltage source signalVsTo an impedanceRUp, a current will be generatedI, as shown in the pictureD.1.

If the impedance value needs to be measured, the voltage on the impedance needs to be measuredV：

Due to the presence of a wire from the voltage source to the measured impedance, the wire has resistancer, leading toV=VsSo if you want to measure impedanceRYou cannot simply use the power supply voltageVsreplaceV.

impedanceRThe measurement circuit should use a diagramD.2 The wiring method for measuring voltage requires a separate wire to be used for the voltmeterROnly by connecting the two ends can measurements be takenRThe voltage valueVBecauseRBoth ends are adopted4The root wire connection is called4Terminal method wiring. pictureD.3The wiring method is incorrect.

adoptCTAWhen measuring the resistance, transformation ratio, and excitation of a transformer, it is necessary to use4Terminal method wiring, as shown in the diagramD.4.

Attention must be paid to the terminal connection of the tested winding when using the four terminal method for wiring. pictureD.5The correct connection method is shown in the pictureD.6、7All are incorrect connections.