Current transformer summarize:
LVQB (T)-35/110/220/330/500W3 CT with bottom-up type which developed by our factory independently is insulated by SF6 gas. It has the advantages which immersing oil instrument transformer doesn`t have, such as excellent insulating capability, long useful time, short producing periods, simple techniques, non-oil, maintenance free, safe and reliable operation. In order to comply with the development trend of non-oil substations and satisfy the requirements of the modern grid for the input and output equipments, the transformers are adopting SF6 gas with high anti-current intensity as the insulated media.
The meaning of the type letters:
L-Current transformer
V-Post
Q-Using gas as the main insulating materials
B-With protection class
T-With transient protection
35 ~ 500-rated voltages, kV
W-Anti-pollution
The main technical specification:
1. Using environments
(1) Sea level altitude: not exceed 2000m
(2) Temperature: Max:+50oC/Min:-40oC;average temperature in the daytime not exceed 30oC
(3) Max relative humidity average per month: 90%
(4) Max average for wind speed within 10min: 35m/s
(5) Max thickness for the covered ice: 10mm
(6) Pollution level: III, IV class
2. Highest voltage for equipment: 40.5/126/252/363/550kV
3. Rated frequency: 50Hz
4. Rated continuous thermal current: 300~4800A
5. Rated current ratio: 300/1~4000/1, 300/5~4000/5
6. Secondary combination: 0.2,0.2S,0.5,0.5S,5P,TPY,TPS and etc. Random combinations.
7. Rated secondary load: 0.2,0.2S,0.5,0.5S,5P:15VA~60VA,TPY:15ohm~20ohm
8. Accuracy limit factor: 20~40
9. Security factor: not exceeding 5
10. TPY accuracy limit condition:
a. The primary time constant TP=100ms
b. DC component of Short-circuit current 100% (full offsetting)
c. Stated working cycle: C100ms O400ms C100ms O
twice electrified to make sure accuracy time 40ms
11. Rated insulation level:
35kVCT: 40.5/95/185kV
110kVCT: 126/200/480kV
220kVCT: 252/395/950kV
500kVCT: 680/1175/1550kV or 740/1175/1550kV
12. Short-time thermal stability current: 50~63kA 3s
13. Rated dynamic stability current: 125~160kA(max)
14. Zero gauge pressure level: 1.3 times of the max operation voltage
15. Partial discharge level: under 1.2 times of the max equipment working voltage not exceeding 5Pc
16. Annual gas leakage: not exceeding 0.1%
17. Water content in the SF6 gas: not exceeding 150 * 10-6 (V/V)
18. Radio interference level: under 1.1 times of the max equipment working voltage, the radio interference voltage not exceeding 500*10-3V
19. External insulation creeping distance: GE 25mm/kV or 31mm/kV
20. Static allowable load of the primary outlet terminal: 4000N~6000N
21. Total max weight: 35kVCT: 500kgs (gas weight 4kgs)
The characteristics of principal insulation structure:
1. The principal insulation structure is same axis columniform type. Primary conductive rod, secondary screen and case body make up of in-line columniform even electric field, the space for principal insulation distance is equal and electric field is fully symmetrical. The above features can fully maximize its insulation effect. Because we can lengthen the base body and secondary screen at the same time, the qty of secondary windings can be increased without limit according to the requirements of the customer. All the rated current ratio can obtain from the secondary terminal directly because the use of one circle for primary winding. We don't need to change series-parallel connection. The above features are simplified the structure, improved the dynamic and thermal stability capability and made convenience for our clients.
2. The insulating gap distance is larger. For example, the insulating gap distance of 500kVCT is at least 150mm, and its zero gauge pressure level shall exceeds 1.3Um/1.73205081
3. Adopting reasonable rated pressure to ensure the reliability of the insulation. The rated pressure for 500kVCT is 0.45Mpa.
4. The partial pressure structure adopts absolutely gas insulation between the main partial pressure screen and high voltage and low voltage. The screen is perpendicular to the ground in order to stop pollution.
5. The 500kVCT products under 680kV power frequency voltage, when we put the products in the dark high voltage center, the corona phenomenon will not appear and partial discharges will less than 5pC.
1)A piece of explosion-proof metal is on the top of the case body. The insulation inside of SF6 transformer has high reliability. Generally, it will not bring internal error electrical arc. But considering the unpredictable factors maybe bring internal electric arc, we have installed explosion-proof metal with explosion-proof pressure 0.8~0.9Mpa to protect the security. This special design can get rid of hidden troubles.
2)The outer insulating bushing: 110 and 220 kV products are using the SF6 special high strength porcelain bushing or hollow high-temperature silastic composite insulator, as well as 500 kV products. The rated pressure they can undertake is 1.6Mpa (The destruct pressure>4.0MPa). The hollow high-temperature silastic composite insulator has good capability to anti-ageing. And the inner underprop is a glass steel canister which assures the bushing intensity.
3)We installed gas density controller in the base of the products, the rated pressure of the products is 0.35Mpa(330 and 500kVCT is 0.45Mpa). When the inner pressure is 0.30Mpa(330 and 500kVCT is 0.40Mpa), the controller will warning. This controller can supply temperature automatically if the indicative pressure figure (density) is the same as the figure under 20oC and the temperature is between -40 oC ~ +60 oC. The density control key is equipped with a special unilateral auto-block valve. If the pressure gauge was removed, valve will close automatically. Gas leakage not exceeding 10-15Mpa.m3/s
4)It has very strict inhibiting sealed structure. The ternary rubber adopts In order to guarantee the airproof capability and extend the useful time, we adopt airproof and waterproof cement to avoid aging. We are sure that the annual gas leakage is less than 0.1% for all of our products which can operate safely for a long time.
5)Moisture is the key problem for SF6 apparatus. Our factory holds very mature oil-immersed paper insulating body drying facility and techniques. Secondary winding though drying in the circular hot air vacuum flow drying facility and adopting the same vacuum drying techniques with oil-immersed products. The products will put into the hothouse (70oC) for dehumidification after thorough drying and whole assembled. We put FO3 absorbent in the products to insure the stability of the gas insulating capability.
Products
Gas-insulated current transfomers
