0.01hz ac vlf tester for cables, transformer
I. Introduction
High voltage withstand test of electrical equipment is one of the most important items specified in insulation preventive test.
The withstand voltage test can be divided into ac withstand voltage test and dc withstand voltage test. The ac withstand voltage test can be divided into power frequency, frequency conversion and 0.1hz ultra-low frequency test technology, of which 0.1hz ultra-low frequency technology is the latest technology recommended by the current international electrotechnical commission. Our company's new generation of VLF tester equipment is the core product independently developed with the latest American technology. It adopts 7-inch touch screen, the latest arm7 single chip microcomputer, high-speed ad acquisition circuit, and is equipped with background management software. It overcomes many shortcomings of domestic similar products.Meanwhile, its cost performance is much higher than that of similar imported products. It is especially suitable for withstand voltage test of electrical equipment with large insulation equivalent capacitance (such as power cable, power capacitor, large and medium-sized generator and motor, etc.)
Hot tags:vlf test kit,vlf cable testing, vlf hipot test, AC hipot tester
II. Feature
- Advanced technology: digital frequency conversion technology, microcomputer control, pressure rise, pressure reduction, measurement, protection, etc
- The test process is fully automated.
- Easy to operate: simple wiring, fool operation.
- Comprehensive protection: multiple protection (over-voltage protection, over- current protection at high and low voltage sides), rapid action (when acting)
- Room ≤ 10ms), the instrument is safe and reliable.
- Safety and reliability: the controller is connected with the low voltage of the high voltage generator, with photoelectric control, safe and reliable use.
- The high and low voltage closed-loop negative feedback control circuit is adopted, and the output has no capacity rise effect.
- Complete configuration: capacitive touch screen, LCD Chinese character display, automatic storage, automatic printing.
- Large test range: 0.1Hz, 0.05Hz and 0.02hz multi frequency selection, large test range.
- Small volume and light weight: it is very convenient for outdoor operation.
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- III. Operation instructions
- Vlf test equipment output wiring method
Wiring instructions: connect the control output special line, high voltage output special line and grounding wire equipped with the product according to the method shown in Figure 3. The power cord of the power socket is connected to the AC of 220V / 50Hz/60HZ. (Input voltage can be customized)-
- IV. Upper computer background management software
This instrument is equipped with VLF super low frequency and high voltage generator upper computer background management software, as shown The software supports Windows XP \ 2000 \ 2007 and other operating systems. The software can be installed on the computer and connected with the USB of the controller through the USB connection line. All the operation functions of the controller can be operated on the software, such as setting parameters, starting the boosting test, saving historical data, etc.-
v. Power cable withstand voltage test method
- Disconnect all electrical equipment connected to the tested cable.
- Use a megger to test the insulation parameters of each phase of the cable, and carry out the ultra-low frequency withstand voltage test only after the test is qualified.
- Set the test voltage value: Umax = 3uo, where uo is the rated phase voltage of the cable.
Example 1: cable parameter: the rated line voltage is 10kV, and the rated phase voltage uo = 6kV, so the test voltage setting value is:
Umax = 3uo = 18kV
See Table 1 for the setting value of 0.1Hz ultra-low frequency test voltage of various rubber and plastic insulated power cables.
Table 1 0.1Hz ultra-low frequency test voltage and time of various rubber plastic insulated power cables.
Rated voltage
U0/US(kV) |
Handover test |
Preventive experiment |
| multiple |
Test voltage(kV) |
Test time(mins) |
multiple |
Test voltage(kV) |
Test time(mins) |
| 1.8/3 |
3U0 |
5 |
60 |
3U0 |
5 |
15 |
| 3.6/6 |
3U0 |
11 |
60 |
3U0 |
11 |
15 |
| 6/6 |
3U0 |
18 |
60 |
3U0 |
18 |
15 |
| 6/10 |
3U0 |
18 |
60 |
3U0 |
18 |
15 |
| 8.7/10 |
3U0 |
26 |
60 |
3U0 |
26 |
15 |
| 12/20 |
3U0 |
36 |
60 |
3U0 |
36 |
15 |
| 21/35 |
3U0 |
63 |
60 |
3U0 |
63 |
15 |
| 26/35 |
3U0 |
78 |
60 |
3U0 |
78 |
15 |
TABLE 1
Note: UN is the rated voltage of the cable, and uo is the phase voltage of the cable.
- Test time: 60 minutes for handover test and 15 minutes for preventive test.
- Setting current value of overcurrent protection:
Estimation method of capacitive current (or leakage current) of ultra-low frequency withstand voltage test article:
Io=2πfCU=2×3.14×0.1CU(mA)… (formula 1)
C is the electric capacity of the cable to the ground, unit: UF; u is the effective value of the test voltage, unit: kV.
Example 2: a 10KV (UN = 10kV, uo = 8.7kv) cable is 4km long, with a single phase to ground capacitance of 0.21uf/km and 0.1Hz super
If the low frequency test voltage is 26kv (peak value), the leakage current is approximately:
Io=2πfCU=2×3.14×0.1CU=0.628×0.21×4×26/ 2 =9.69(mA)
Setting current value of overcurrent protection: I=kIo (formula 2)
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Wiring instructions: connect the control output special line, high voltage output special line and grounding wire equipped with the product according to the method shown in Figure 3. The power cord of the power socket is connected to the AC of 220V / 50Hz/60HZ. (Input voltage can be customized)
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