1 General Description

1.1 Application

Oil immersed condenser bushing is used for high voltage transformer, insulating from the earth and supporting the conductor when the leading conductor passes throughout the cover of the transformer

1.2 Adopted standards

GB/T4109 “Specification of High Voltage Bushing”

GB13027 “Types and Dimensions of Oil Impregnated Paper Capacitance Bushing”

1.3 Types and bushings

 

 

a type designation of bushings  BR indicates oil immersed condenser bushing for transformer

b. characteristics of construction    D indicates short tail bushing and long tail not be designated

L indicates CTs may be mounted and no designation indicates CTs may not be mounted

c construction of outer insulation  W indicates pollution type and common type not be designated

d number of the design series   according to the sequence of design, the arrangement from 1 in accordance with the natural numeral.

e rated voltage  72.5KV 、126KV 、252KV

f rated current  630A、800A、1000A、1250A

g operation conditions  TH indicates applicable for tropical climate with high humidity

h pollution class of outer insulation   no designation     minimum nominal leakage distance ratio is 16mm/kv

      2   minimum nominal leakage distance ratio is20mm/kv

      3   minimum nominal leakage distance ratio is25mm/kv

      4   minimum nominal leakage distance ratio is31mm/kv

1.4 operation conditions

a. ambient temperature     -20℃~＋40℃ for bushing filled with no 25 transformer oil

        -40℃~＋40℃ for bushing filled with no 45 transformer oil

 

b altitude   bushing with common type outer insulation not excess 1000m

             bushing with reinforced outer insulation not excess 3500m

c pollution class Ⅱ、Ⅲ、Ⅳ class

1.5 main technical specification table

note: if test voltage is divided into two stages it will be determined according to the agreement to between the purchaser and manufacturer.

 

 

                          2 construction and principles

The main insulation of bushing is a condenser body。It is a multiplex cylindrical condenser which consists of high quality oil impregnated paper and aluminum grading layers for field control. The bushing is filled with transformer oil. Oil conservator located at the top is used for adjustment of the variation of pressure due to the variation of oil temperature in the bushing. On the oil conservator there is an oil level gauge by which the oil level can be checked and the oil quantity can be adjusted. The flange for installation and the oil sampling valve are located on the coupling cylinder. The little porcelain insulator is a test tap which is connected to the final layer of the condenser body .Using the test tap, the measurements of dielectric dissipation factor and partial discharge can be performed. During operation it must be grounded never be opened circuit.

                         3 Transport and storage

3.1 The packing cases are made of steel and wood with a composite structure. During packing the bushing must be substantially fixed on the base of the packing case. In transportation the packing case should be located according to the specified direction, don’t be inverted.

3.2 The bushing should be stored in the room keeping away from flammable, explosive matters. The storage temperature should not be lower than the condensation temperature of the transformer oil.

 

           4 Acceptance examination, erection and operation

4.1 After taking the product out of the packing case, following items should be examined: the outer view should be no damage. The tightening screws and bolts should be entire without loosing, the seals should be hermetical without any oil leakage and other damages, the spare parts and components and the technical documents provide by manufacturer should be complete..

4.2 Measurement of dielectric loss tanδ and capacitance of the bushing.

   Under the conditions of room temperature 10-40℃,the tanδof bushing should be not exceeds 0.007,no substantial difference between the actually measured capacitance and the value marked on the name plate is allowed.

4.3 The angle between the mounting axis of bushing and vertical axis should be not more than 30°

4.4 During mounting the bushing, after removing the terminal plate and conductor bolt, pulling out the leading cable of transformer from the empty tube, the lead conductor will be fixed on the location nut by cylindrical pin then ,screwing the conductor bolt, fitting on the terminal plate.

4.5。According to the ambient temperature, the oil level shall be determined as contrasted with coordination of the oil guage.If the oil level unduly high, the oil sampling valve should be unscrewed to drain out the remain transformer oil (together opening the oil obstructing bolt located on the oil conservator) If the oil level unduly low, the oil quantity should be replenished. The oil filled in the bushing should be with same designation (the best is from the same producing place) as to the quality of oil n the bushing does not decrease. If necessary, the oil compounding test should be performed.

4.6 For fixed and permanent purchasers, the oil filled in bushing is the transformer oil with designation NYREO 10GBX from Hong Kong Nynas Co.ltd. After treatment, attaining the following required specifications, the oil may be used.

Puncture voltage≧70kv/2.5mm(sphere electrode)

Value of micro water≦8PPm tanδ（90°）≦0.005

Other comply with the requirements of IEC296

Note: Owing to less oil quantity in the bushing, the oil replenishment always is necessary after the oil sample inspection. The quality of the bushing will decrease in consequence of oil compounding. Therefore we hope that this inspection will be carried out as little as possible.

4.7 During operation, the test tap must be earthed. Don’t open circuit.

4.8 Application of the oil-sampling valve

  a Direct sampling with syringe

Removing the protective cover, rotating the oil sampling joint2-3 turn along inverse clock direction, turning the needle of syringe on the rubber obstructer and penetrating in 10-30mm,the oil of the bushing will be exhausted out slowly.

  c Replacement of rubber obstructer

When the rubber obstructor of oil sampling joint has been penetrated by needle about 10 times or discovering that the oil flows or leaks out after tuning tight the oil sampling joint, the old obstructer should be removed and replaced by spare obstructer, every oil-sampling valve has two spare rubber obstructer.

4.9 During operation,the measurement of dielectric loss and capacitance of the bushing will be carried out periodically.If the capacitance change suddenly and dielectric loss notably increases, the bushing should be out of the operation immediately. After ascertaining reasons and the treatment having been performed, the qualified bushing may be taken into the operation.

4.10 6 The lifting of the bushing is shown in figure 6

Using four lifting ropes with enough strength and the same length to hang over the four lifting rings on the flange separately, using a nylon rope to tighten with the

Note:Under conditions that the safety of persons and product can be guaranteed other methods for lifting bushing may be allowed.

 

 

 

 5 Guarantee period of quality and ordering

1． Under condition that purchased comply with the requirement specified in this instructions for transport、storage/ erection and operation, in two years from the date of delivery the bushing will be repaired or replaced by manufacturer of no charge if it is not available due to the fault in the bushing. Over two years, the manufacturer will be commissioned to repair the bushing but some payment will be charged according to the actual condition.

2. When ordering please carefully indicate the name、type、specification、quantity and main technical characteristics of the bushing. If the particular requirements of purchasers are necessary the technical agreement will be signed.