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ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator
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ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator
ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator
ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator
ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator

I. Overview

Huazheng Electric 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 Huazheng Electric 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 ultra-low frequency and high voltage generator 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 (see table 1), and 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.), which conforms to the national standard of electric power industry, general technical conditions for ultra-low frequency and high voltage generator (d) newly issued in 2004 l / t849.4-2004.

 

0.1Hz voltage-withstand equipment type

HV control method

High voltage waveform

Energy saving

Noise

Lifespan

Electrical life

mechanical

HV mechanical switch switching polarity

Square wave

Not energy-saving: consume excess energy with high-power resistors

High

short

Short

Electronic

HV electronic switch switching polarity

Sine wave

Energy saving: feed back excess power to the grid

A little

No lifespan, can use long-term

Long

 

Table 1 performance comparison between mechanical type and electronic type of 0.1Hz voltage withstand test equipment


II. Advantages of 0.1Hz ultra-low frequency withstand voltage technology

In fact, the ultra-low frequency insulation withstand voltage test is an alternative to the power frequency withstand voltage test. In the power frequency withstand voltage test of large and medium-sized generators, motors, power cables and other test objects, due to their large capacitance in the insulation layer, a large capacity test transformer or resonance transformer is required. Some of these huge equipment is not only heavy and expensive, but also inconvenient to use. In order to solve this contradiction, the method of reducing the test frequency and the capacity of the test power supply is widely used in the world. It has been proved from many years of theory and practice at home and abroad that replacing power frequency withstand voltage test with 0.1Hz ultra-low frequency withstand voltage test can not only have the same equivalence, but also greatly reduce the volume and weight of the equipment, theoretically, the capacity is about one fifth of the power frequency, and the operation is simple. This is the main reason why this method is widely used in developed countries.

According to the actual situation of China's power system, the national development and Reform Commission has formulated the industry standard of ultra-low frequency (0.1Hz) withstand voltage test method for 35kV and below XLPE insulated power cables. In 2004, the industry standard DL / T 849.4-2004, general technical conditions for ultra-low frequency and high voltage generators, which is being promoted in China. Although the DC voltage withstand test equipment has the advantages of small size, light weight and low cost, the DC voltage withstand test is also the most destructive to the insulation of the tested object. (see Table 2) therefore, the latest national regulations on preventive test of electrical equipment have expressly stipulated that DC high voltage is no longer used for voltage withstand test of electrical equipment, and AC voltage withstand test is recommended.

The new generation of 0.1Hz ultra-low frequency high voltage generator developed by our company adopts the latest power electronic components and the latest ARM7 single-chip technology, further reducing the volume and weight of the equipment, fool operation, more stable performance, overcoming the shortcomings of the first generation of mechanical booster, such as short service life, high failure rate and large volume. Through years of practice, a large number of user feedback shows that: - 80kV ultra-low frequency high voltage technology is leading in the country, with the highest cost performance!

Table 2 performance comparison of various withstand voltage test equipment:

Compare content

Power frequency withstand voltage

Frequency withstand voltage

0.1Hz withstand voltage

DC withstand voltage

Equivalence

good

Good

Good

Bad

Insulation destructive

small

small

small

big

Operation safety

low

low

high

A little low

Wiring

Complicated

Most Complicated

Most easy

complicated

Volume and weight

Heavy and big

Heavy and big

Light and small size

Light and small size

 

III. technical parameters of series products

Ground voltage generator








Model

Rated Voltage


Load

Fuse

Weight


















40kV


0.1Hz,≤1.1µF


Controller6Kg


  40KV /1.1



8A



0.05Hz,≤2.2µF


Peak Value


Booster20Kg









0.02Hz,≤5.5µF

















50kV


0.1Hz,≤1.1µF


Controller6Kg


 50kV/1.1



10A



0.05Hz,≤2.2µF


Peak Value


Booster45Kg









0.02Hz,≤5.5µF
















80KV/0.5

80kV

Peak Value

0.1Hz,≤1.1µF





20A

Controller4Kg


0.05Hz,≤2.2µF





booster50Kg


0.02Hz,≤5.5µF









 

1) Select products of appropriate specifications according to the subjects

When in use, the capacitance of the test object shall not exceed the rated capacitance of the instrument. If the capacitance of the test object is too small, the output waveform will be affected. If it is less than 0.05 μ F, the instrument will not output normally. At this time, 0.05 μ f capacitor (provided by the company) can be connected in parallel for auxiliary output. See Table 4 and table 5 for the estimation of capacitance of common electrical equipment.

Table 4 single phase earth capacity of different types of generators.


Steam turbine generator

Hydro generator

Capacity MW

200

300

600

85

125-150

300

400

Single phase ground capacitance(uF

0.198

0.18-0.26

0.31-0.34

0.69

1.8-1.9

1.7-2.5

2.0-2.5

 Table 5 capacitance of XLPE insulated single core power cable (μ f / km)

Voltage(KV)

capacitance

(uf/Km)

Cross-sectional areamm

16

25

35

50

70

95

120

150

185

240

10

0.15

0.17

0.18

0.19

0.21

0.24

0.26

0.28

0.32

0.38

35

0.11

0.12

0.13

0.14

0.15

0.16

0.17

 

2) Estimation method of test object current:

Calculation formula: I = 2 π FCU


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ultra low frequency cable withstand test equipment vlf high voltage generator very low frequency generator

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+8618330222305 +8618330222305 sales08@bdhuazheng.com 0086-18330222305 Julia Jin-huazheng