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Instrument current transformer

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Instrument current transformer
Instrument current transformer

Instrument current transformer

Instrument current transformer

As we all know, for the sake of safety, medium and high voltage current transformers in transformer test stations are mostly placed on the platform between the medium transformer and the tested transformer.

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    Instrument Current Transformer

    As we all know, for the sake of safety, medium and high voltage current transformers in transformer test stations are mostly placed on the platform between the medium transformer and the tested transformer. Because the platform height is between 2-4m, it is very inconvenient to manually change the connection range to go up and down the platform.

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    In recent years, there are several ways to solve this problem in the domestic industry, which are not satisfactory
    (1) The current transformer is divided into 2-3 sections at the first time and 3-4 sections at the second time. The secondary can be switched by tap changer. It reduces the number of switching once, but after all, it has to change the line on and off the platform once, which increases the unsafe factor for the test personnel.
    (2) It can be used as electric primary high voltage tap changer. The switch and current transformer are independent of each other and connected with copper bar. High voltage switch has high cost, high failure rate and poor reliability. The partial discharge is above 50pc. No partial discharge.
    (3) Some manufacturers have manufactured the integration equipment of current transformer and tap changer. It looks compact, but most of them are damaged due to switch failure during the warranty period, resulting in the production stop.
    In recent years, our company has developed a new type of current transformer according to the requirements of foreign users
    (1) Completely in the secondary switching range, on load switching, in the secondary electric control switching, it is very convenient to use, and saves the primary switch with high failure rate.
    (2) Compatibility with power analyzer: the secondary rated current is 1a, not 5A. Using the power analyzer, the secondary rated current can be 1a. Taking the W-3000 power analyzer as an example, this paper explains the adaptability of this kind of current transformer and power analyzer: the current channel of W-3000 power analyzer has two large and small channels, and the small current channel is selected. The rated current is 5mA, 10mA, 20mA, 50mA, 100mA, 200mA, 500mA, 1A and 2a, with 9 gears in total, which can shift automatically with the input current. It can be adapted to the current transformer of secondary 1a.
    The input impedance of small current channel of W-3000 power analyzer is 0.5 Ω, and the secondary circuit impedance is 0.3 Ω at most, so the rated output should be 0.6-0.8va.
    (3) Due to technical limitations, the rated current range: IMAX / Imin ≤ 400, see Table 1 and table 2 for details.
    (4) Error: with the increase of current range, the accuracy level increases from 0.2 to 0.01. This feature is just suitable for transformer test. As we all know, because the power factor of no-load test is in the order of 0.2, high-precision transformer is not needed. At this time, the low range of 50A and below is used, and the accuracy is enough. The power factor of load test is very low (up to 0.02-0.01), which requires high accuracy of the transformer. At this time, the high range section of 100A and above is used, and the accuracy is very high, up to 0.01 level.
    When IMAX / Imin ≤ 400, the accuracy levels of various current ratios are shown in Table 1 and table 2
    Table 1

    Current ratio

    5/1A

    10/1A

    20/1A

    50/1A

    100/1A

    200/1A

    500/1A

    1000 /1A

    2000/1A

    Accuracy level

    0.2

    0.1

    0.05

    0.02

    0.01

    0.01

    0.01

    0.01

    0.01
    Table2

    Current ratio

    10/1A

    20/1A

    50/1A

    100/1A

    200/1A

    500/1A

    1000 /1A

    2000/1A

    4000/1A

    Accuracy level

    0.2

    0.1

    0.05

    0.02

    0.01

    0.01

    0.01

    0.01

    0.01
    We know that the formula of transformer loss measurement error: Δ P% = 0.0291 δ TG φ% (1) Where δ is the difference (unit: minute) φ of the angle difference between current transformer and voltage transformer is the power factor angle during the test. The range of small current is 5 / 1a-50 / 1a, which is mainly used for no-load test. Cos φ is about 0.2 when no-load test, that is, TG φ is 1.9. The maximum angular difference of the lowest level 0.2 is ± 10. The matched voltage transformer can be used as level 0.01, the maximum angle difference is ± 0.3, and the maximum difference δ between them is ± 10.3. The value is substituted into formula (1) Δ P% =0.0291 × (± 10.3,) × 1.9% = ± 0.57%, which is the maximum error of class 0.2. If the 0.1 gear is used, the error is still half, which should be said to be very accurate. The current ratio used in load test is above 100/1a, and the accuracy level is 0.01. For example, 35/10kv, 3150kva transformer, rated current at 35kV side is 52A, and 100/1a gear shall be selected.657ed23jst The cost of this product is less than the sum of the current transformer and its tap changer of primary switching range. All voltage levels can be used. This technology is based on the revolutionary innovation of electromagnetic current transformer itself, rather than using electronic amplifier to change range in the second time, like the Swiss company haefely trench. This model is the first in the world, exclusive production, and others will not. Compared with haefield, the advantages of our new current transformer are as follows: 
    (1) High cost performance. The transformer test can also be conducted in the second remote range switching, with the cost of about 1/10 of Switzerland. 
    (2) High reliability. Without electronic amplifier, high reliability. The electronic equipment is easily damaged by voltage in the high voltage laboratory environment. If it is damaged, it can only be sent to Switzerland for repair, which cannot be repaired in China. The domestic users of the new current transformer are shown in the following table:

    Unit name

    specification

    Qty

    Tianjin electric power company

    Rated voltage: 110/√3kV Rated current range: 10-2000A

    3Sets

    Shanghai Jiuzhi Electric Co., Ltd. (export to India)

    Rated voltage: 100kV Rated current range: 1-2000A

    4Sets

    Shanghai Shangfang Electric Appliance Co., Ltd. (export to India)

    Rated voltage: 100kV Rated current range: 1-2000A

    3Sets

    China New Era International Engineering Corporation

    Rated voltage: 110/√3kV Rated current range: 10-1600A

    3Sets

    Shanghai Lanqi Electric Co., Ltd. (export to India)

    Rated voltage: 100kV Rated current range: 1-2000A

    3Sets

    Baicheng power Zhenlai Transformer Co., Ltd

    Rated voltage: 110/√3kV Rated current range: 10-1600A

    3Sets

    Shenyang Xinxin United Electric Co., Ltd. (exported to India)

    Rated voltage: 100kV Rated current range: 5-2000A

    6Sets

    Tongbian Electric Appliance Co., Ltd

    Rated voltage: 80/√3kV Rated current range: 5-2000A

    3Sets

    China New Era International Engineering Corporation

    Rated voltage: 120/√3kV Rated current range: 5-2000A

    3Sets

    Changzhou Pacific power equipment (Group) Co., Ltd

    Rated voltage: 80/√3kV Rated current range: 5-1600A

    3Sets

    Beijing Huatian Electromechanical Research Institute Co., Ltd

    Rated voltage: 110/√3kV Rated current range: 5-1500A

    3Sets

    Beijing Huatian Electromechanical Research Institute Co., Ltd

    Rated voltage: 20/√3kV Rated current range: 5-400A

    3Sets

    TBEA Hengyang Transformer Co., Ltd

    Rated voltage: 252/√3kV Rated current range: 10-4000A

    3Sets

    Tianwei baobian (Hefei) Transformer Co., Ltd

    Rated voltage: 40/√3kV Rated current range: 2-800A

    3Sets

    Ruili Yixin Co., Ltd. (exported to Myanmar)

    Rated voltage: 12/√3kV Rated current range: 5-600A

    3Sets

    Shenyang Xinxin United Electric Co., Ltd. (exported to India)

    Rated voltage: 30kV Rated current range: 5-500A

    3Sets

    Shenyang Xinxin United Electric Co., Ltd. (exported to India)

    Rated voltage: 50kV Rated current range: 5-500A

    6Sets

    Shenyang Xinxin United Electric Co., Ltd. (exported to India)

    Rated voltage: 5kV Rated current range: 5-100A

    3Sets

    Jinan Siemens Transformer Co., Ltd

    Rated voltage: 110/√3kV Rated current range: 10-3000A

    3Sets

    China Qiyuan engineering design & Research Institute Co., Ltd

    Rated voltage: 150/√3kV Rated current range: 10-2000A

    3Sets

    China Qiyuan engineering design & Research Institute Co., Ltd

    Rated voltage: 80/√3kV Rated current range: 5-1000A

    3Sets

    Wujiang Transformer Co., Ltd

    Rated voltage: 20/√3kV Rated current range: 5-600A

    3Sets

    Shandong Electric Power Equipment Co., Ltd

    Rated voltage: 70/√3kV Rated current range: 5-1600A

    3Sets

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