Test Transformer
Overview
YD (JZ) series oil-immersed test transformer is a new type of test transformer which is produced according to the standard of Ministry of Electrical and Mechanical Services "Test Transformer" after a lot of improvements on the basis of the original similar products. Test transformer is in the YD (JZ) series of test transformers on the basis of the national standard "JB / T 9641-1999" after the improvement of a new type of products. This series of products has a small volume, light weight, compact structure, complete functions, strong versatility and easy to use and so on. It is especially suitable for electric power system, industrial and mining enterprises, scientific research departments and other high-voltage electrical equipment, electrical components, insulating materials for industrial frequency or DC high-voltage insulation strength test. It is an important and indispensable equipment for high voltage test.
Second, the meaning of the product model
Third, the product structure
YD (JZ) series of oil-immersed test transformer adopts a single-frame core type iron core structure. The primary winding is wound on the core, the high voltage winding is outside, this coaxial arrangement reduces the leakage flux, thus increasing the coupling between the windings.
The shell of the product is made of octagonal structure with better core coordination, and the overall appearance is beautiful and generous. Its external structure is shown in Fig. 1, and its internal structure is shown in Fig. 2.
1-Short-circuit rod D 2-voltage equalizing sphere 3-High-voltage bushing 4-Transformer carrying handle
5-Oil valve 6-7-Secondary voltage inputs a, x 8-9-Measuring terminals E, F 10-Transformer shell ground terminal
11-High-voltage tail X 12-High-voltage output A 13-High-voltage silicon stack 14-Transformer <
15-core 16-secondary low-voltage winding 17-measurement winding 18-secondary high-voltage winding
In YD (JZ) test transformer, a, x are low-voltage input terminals, E, F are instrumentation measurement terminals, and A, X are high-voltage outputs. there is no high-voltage silicon stack in YD (JZ) series.
Four, working principle
YD (JZ) series of oil-immersed test transformer is a single-phase transformer, with frequency 220V (10kVA or more 380V) power supply into the XC/TC (for the production of the company's special equipment for the test transformer, please see the specific instruction manual for details) series of operating box (table), through the autocoupler in the operating box. ), by the operation of the box autotransformer (50kVA or more regulator attached) adjusted to 0-200V (or 0-400V) voltage output to the initial winding of the YD (JZ) test transformer, according to the principle of electromagnetic induction, in the high-voltage windings of the test transformer can be obtained for the test of the required high voltage.
1, a single YD (JZ) test compressor working principle diagram in Figure 3
2, a single YD (JZ) test transformer working principle diagram in Figure 4, the figure in the high-voltage casing is equipped with a high-voltage silicon pile, series in the high-voltage circuit for half-wave rectification, to obtain DC high voltage. When a short-circuit rod will be high-voltage silicon pile shorted, can obtain high frequency voltage, as the AC output state; cancel the short-circuit rod, as the DC output state.
3, three test transformers in series to obtain a higher voltage junction principle see figure 5. series of high-voltage test transformer has a great advantage, because the whole test set by several single test transformer, a single test transformer capacity is small, low-voltage, light weight, easy to transport and installation. Since it can be connected into a series of several times higher than the output voltage of a single test transformer combined use, and can be separated into several sets of single test transformer used alone. The whole set of device investment is small, economical. Figure 5, in the first and second level of each unit test transformer has an excitation winding A1, C1 and A2, C2. in the series of test transformer basic principle diagram, the low-voltage power supply is added to the primary winding a1x1 of test transformer I, a single test transformer I, Ⅱ, Ⅲ output voltage are V. Excitation winding A1, C1 to the second stage of the test transformer Ⅱ of the primary winding power supply; the second stage of the test transformer Ⅱ of the excitation winding A1, C1 to the second stage of the test transformer Ⅱ power supply; the second stage of the test transformer Ⅱ of the excitation voltage is V. The excitation windings A2 and C2 of test transformer II supply power to the primary winding of test transformer III of the third stage. The boxes of the second-stage test transformer Ⅱ and the third-stage test transformer Ⅲ are respectively at a high potential of 1V and 2V to ground, so the box is insulated to ground, and the box of the test transformer I is grounded. So that the first level, the second level, the third test transformer rated output voltage to ground were 1V, 2V, 3V; its rated capacity were 3P, 2P, 1P.
YD (JZ) test transformer high-voltage casing in the high-voltage silicon pile is not drawn, the principle is the same as the above figure.
Fifth, the use of
YD (JZ) test transformer to do the test product frequency withstand voltage test using the wiring schematic diagram shown in Figure 6.
Note: high-voltage tail must be reliably grounded.
Industrial frequency withstand voltage test current limiting resistor R1 should be selected according to the rated capacity of the test transformer. If the rated output current of high voltage side is 100-300mA, 0.5-1Ω/v (test voltage) can be taken; if the rated output current of high voltage side is more than 1A, 1Ω/v (test voltage) can be taken. Commonly used water resistor as current limiting resistor, the length of the tube can be considered as 150kV/m, the thickness of the tube should have enough heat capacity (water resistance liquid preparation method: using distilled water to add the appropriate amount of copper sulfate prepared into a variety of different resistance values).
Ball gap and protection resistance: when the voltage exceeds the ball gap setting value (generally take 110%-120% of the test voltage) ball gap discharge, the test piece to play a protective role. Ball gap protection resistance can be selected according to 1Ω/V (test voltage).
In the frequency withstand voltage test, the low-voltage side measurement voltage (instrument voltage) is not very accurate, the reason is that the test transformer there is a leakage pit, in which the leakage resistance on the inevitable existence of the voltage drop or capacitance rise, so that the voltage on the test specimen is lower than or higher than the low-voltage side of the measurement of the voltmeter reflected on the voltage.
Working frequency withstand voltage test, the voltage on the test article is higher than the output voltage of the test transformer, also known as the capacitive rise phenomenon. Induction withstand voltage test, the leakage reactance of the test transformer must exist a voltage drop.
In order to accurately measure the voltage applied to the test piece, so often in the high-voltage side of the access to the RCF resistive voltage divider to measure the voltage (see Figure 6).
Precautions for the operation of frequency withstand voltage test:
(1) The test personnel should do a good job in the division of labor, and make it clear how to contact each other. And there are special people to monitor the site safety and observe the state of the test specimen.
(2) The test article should be cleaned first, and absolutely dry, so as to avoid damage to the test article and the test brought about by the error.
(3) for large-scale tests, generally should be carried out first air test. That is, without the test piece when boosting to the test voltage, calibration of various meters, adjust the ball gap.
(4) boosting speed can not be too fast, and must prevent sudden pressurization. For example, the regulator is not in the zero position of the sudden closing. Also can not suddenly cut off the power supply, generally should be pulled when the regulator down to zero position.
(5) when the voltage rises to the test voltage, start timing, to 1min, quickly drop the voltage to 1/3 of the test voltage below, before pulling the power supply.
(6) In the process of voltage rise or withstand voltage test, if the following abnormalities are found, the voltage should be immediately reduced, cut off the power supply. Stop the test and find out why: ① voltmeter pointer swings greatly; ② found insulation burnt or smoke; ③ the test article has an abnormal sound.
(7) before and after the voltage test should measure the insulation resistance, check the insulation.
(8) YD (JZ) test transformer in the DC withstand voltage or leakage test of the test article wiring schematic diagram as shown in Figure 7.
Note: This test should be drawn out the short-circuit rod "D", shown in Figure 7.
Leakage test in the current limiting resistor R1 selected in the rated output voltage, the output short-circuit current does not exceed the maximum rectifier current of the high-voltage silicon pile. Such as voltage silicon pile of the maximum rectification current of 100mA for 60kV test device, current-limiting resistor according to R1 = 60/0.1 = 600kΩ selection. Current limiting resistor should also have sufficient capacity and discharge distance along the surface. High-voltage current filter capacitance C1 is generally selected in the 0.01- 0.1uF, when the capacity of the test piece is very large, C1 can be omitted.
Leakage test operation and precautions:
(1) Before the test should be checked whether the test article is blackout, grounding discharge, all external wires are wiped clean. To prevent the test voltage is added to the part of someone working up.
(2) After connecting the wiring of the test device, should be checked for errors before applying pressure. Special attention should be paid to check the high-voltage equipment and leads and ground, and the operator staff safety distance, whether the shell of the test product is reliably grounded, to be tested according to the contents of the safety regulations specified in the test.
(3) for large-capacity equipment should be slowly pressurized to prevent the charging current of the test piece burned microampere meter. If necessary, the voltage should be graded, respectively, read the stable reading of the microammeter at all levels of voltage.
(4) the test process, should closely monitor the test piece, the test device, microampere meter, once the breakdown, flicker and other abnormal phenomena should immediately reduce the voltage, cut off the power supply, and find out why, detailed records.
(5) After the completion of the test, reduce the voltage, cut off the power supply should be the subject and the test device itself fully discharged.
Six, precautions
1, according to the test you carry out to connect the working line. The shell of the test transformer as well as the shell of the operating system must be reliably grounded. The X end of the high voltage winding of the test transformer (high voltage tail) and the F end of the measurement winding must be reliably grounded.
2, do series test, the second level, the third level of the test transformer of the low-voltage winding into the X-terminal, measurement winding F-terminal and high-voltage winding X-terminal (high-voltage end) are connected to the level of the test transformer with shell. The second and third stage test transformer shell must be grounded through the insulation bracket.
3, before turning on the power supply, the operating system regulator must be adjusted to zero before turning on the power supply, close the gate, start boosting.
4, from zero to rotate the regulator handwheel at uniform speed to boost. Boosting method: fast boosting method, that is, 20s step-by-step boosting method; slow boosting method, that is, 60s step-by-step boosting method; very slow boosting method for selection. Voltage from zero according to a certain boosting method and speed up to 75% of the rated test voltage you need, and then 2% of the rated test voltage per second to the speed of the test voltage you need, and pay close attention to the measuring instrument and the situation of the test article. If the indication of the measuring instrument and the test object are found to be abnormal in the process of voltage increase or test, the voltage should be reduced immediately, cut off the power supply and find out the situation.
5, after the test is completed, the regulator should be returned to zero within a few seconds at an even speed, and then cut off the power supply.
6, the product shall not exceed the rated parameters. In addition to the test necessary, never voltage energized or disconnected.
7, the use of this product to do high-voltage test, in addition to familiar with this manual, but also must strictly enforce the relevant national standards and operating procedures. Reference can be made to GB311.1 - 97 "high-voltage transmission equipment insulation with high-voltage test technology"; "Electrical Equipment Preventive Test Regulations" and so on.
Seven, supporting products
1, operating system:
Operating box: capacity: 1kVA - 5kVA Input voltage: 0.22kV
Operating desk: capacity: 10kVA-300kVA ? Input voltage: 0.22kV, 0.38kV
2, Protective digital microammeter
3, Capacitor-resistant AC/DC voltage divider 50, 100, 150, 200kV
4, High-voltage DC Discharge Bar 70, 140, 210kV
5, High-voltage silicon stack 150, 300, 450kV
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10, standard test oil cup 400ml
11, dielectric oil cup
12, folding trolley 150, 300 type
13, water resistor
14, high-voltage tester 10kV? 35kV
15, high-voltage phasor 10, 35, 110kV? 220kV
16, all kinds of universal testing device 10, 100, 150, 200, 250, 50017, high-voltage testing device 10, 35, 110kV?
16, a variety of multimeter, megohmmeter and test line
Eight, the capacity of the test transformer selection
The nominal test transformer capacity Pn determining formula: Pn=KVn2ωCt?0-9
The formula: Pn---- nominal test transformer capacity (kVA)
Vn-----RMS value of nominal output high voltage of test transformer (kV)
K------safety coefficient. K≥1, nominal voltage Vn≥1MV, K=2, nominal voltage is lower, K value can be taken higher.
Ct-----capacitance (PF)
ω----angular frequency, ω=2πf, f----frequency of the test power supply
The capacitance Ct of the equipment under test can be measured by an AC bridge.Ct varies greatly, and can be determined by the type of equipment. Typical data are as follows:
Simple bridge or suspension insulators A few tens of microfarads
Simple graded bushings 100 - 1000PF
Voltage transformers 200 - 500PF
Power transformers < 1000kVA - 1000PF
> 1000kVA 1000 - 10000PF
High voltage power cables and oil-immersed paper insulation 250 - 300PF/m
Gas insulation - 60PF/m
Enclosed substations, SF6 gas insulation 100 - 10000PF
For different test voltages Vn, different (appropriate) safety factors are selected, K. The values of K for different Vn are listed above for reference
Vn = 50-100kV K=4
Vn = 150 -300kV K=3
Vn > 300kV K=2
Nine, YD (JZ) main technical parameters of the test transformer table
(a), YD (JZ) series of lightweight AC and DC test transformers (see Table 1)
Table 1, YD (JZ) series of lightweight AC test transformers
Table 1, YD (JZ) series of lightweight AC test transformers
Note: The series of products have 200V taps, can be two or three cascade into 100kV, 150kV, 200kV, 300kV and higher high voltage. According to the user's needs, in the high-voltage winding can be drawn out 5-15kV medium-voltage taps for high-voltage motor for AC withstand voltage test.
Test Transformer