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ABB Power Technologies AB

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Current transformer type IMB

bb

1HSE 96001-30 en 3

Operating instruction

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PTHVP/PDM 1HSE 96001-30 | 3 | | | 1 | en | DOCUMENT (Released) Approved: 2004-03-11, J-E Rajakangas, PTHVP/IK.


UPON RECEIPT OF CURRENT TRANSFORMERS


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Table of contents 1 UPON RECEIPT OF CURRENT TRANSFORMERS ........... 3

2 ASSEMBLY......................................................................... 4

3 FINAL CHECKING AFTER ASSEMBLY............................. 5

4 MAINTENANCE .................................................................. 6

5 OIL SAMPLING, FILLING OF OIL....................................... 8 5.1 Transformers with gas cushion ............................................ 8 5.2 Transformers with metal bellows in cooler ......................... 10

6 STORAGE......................................................................... 11

7 TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 36-420 ............... 12

7.1 Transport ........................................................................... 12 7.2 Arrival inspection................................................................ 12 7.3 Lifting and handling............................................................ 13 7.4 Installation.......................................................................... 14

8 TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 420 and 800 ...... 15

8.1 Transport ........................................................................... 15 8.2 Arrival inspection................................................................ 15 8.3 Lifting ................................................................................. 16 8.4 Installation.......................................................................... 17

9 CHECKLIST FOR IMB ...................................................... 18

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UPON RECEIPT OF CURRENT TRANSFORMERS


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1 UPON RECEIPT OF CURRENT TRANSFORMERS The goods are to be checked for transport damage immediately upon receipt. Ensure that the packaging has not been damaged due to mishandling. Make a note of any damage (preferably a photograph) and contact the insurance company. Check the transformers. Take particular care to detect any signs of oil leakage, damage to the insulator, and make sure that oil is visible in the oil level gauge. With the transformer in vertical position, the oil level glass shall be dark. If the right side of the glass is bright or the oil level is visible in the glass the oil level in the transformer is too low. The leak must then be located immediately. Contact ABB for instructions before attempting any repair of damaged transformers. Instructions for primary terminals, unpacking and hoisting are enclosed with each transformer.

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ASSEMBLY


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2 ASSEMBLY Check the support and make sure that it is flat and horizontal, before placing the transformer on the support. Unbalanced tightening of the transformer may cause leakage. Adjustments can be made with washers between support and transformer. Lift the transformer by the four lifting lugs at the base of the tank and place it on the support. See instruction 1HSE 96002-30 (IMB 36-420) or -36 (IMB 420-800). Do not hoist the transformer by any other way as described in the lifting instruction on page 13 and 16. Tighten the fixing bolts to the support. The tightening torque should be determined with regard to the material and dimension of the bolts in order to obtain the specified pre-tensioning load. See table below. Connection of the secondary terminals should be made carefully. The terminals are marked on the terminal blocks. There is a circuit diagram on the transformer rating plate inside the terminal box. Secondary windings that are not in use are to be short-circuited and connected to earth.

Never leave a secondary winding open. Very high induced voltages are generated across the terminals and both the user and the transformer are subjected to danger. Each secondary winding must be earthed at one point to an earthing terminal. A suitable earthing rail is located in the terminal box. Mount the primary terminals according to instruction 1HSE 96002-31, -32 or -35 (IMB 420-800). The primary connection should be made in such a way that the static mechanical load on the primary terminal is minimized. This is achieved through a flexible connector in the primary connection. A fixed (not flexible) connection may lead to oil leakage in the primary terminals. All connections must be carried out very carefully, as a connection that is not sufficiently tightened may cause overheating and damage the transformer. Maximum permitted static load on each terminal is 4000 N (6000 N for IMB 420-800) in all directions and 1000 Nm torque. The earthing terminal of the transformer is located on one (or two) of the transformer mounting feet. The terminal can be moved to any foot. The capacitive terminal, if any, shall be earthed to the transformer tank if not in use. Assemble surge arrester etc. (if any).

Tightening torque on screws

M6 9,5 Nm M8 22,5 Nm M10 45 Nm M12 79 Nm M16 190 Nm M20 420 Nm M24 735 Nm

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FINAL CHECKING AFTER ASSEMBLY


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3 FINAL CHECKING AFTER ASSEMBLY After the assembly has been completed, a repeated check of the transformer is recommended.

Check:

the oil level

signs of oil leakage

damage to insulator, etc.

connections have been made correctly

no secondary windings are left open

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MAINTENANCE


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4 MAINTENANCE Due to the fact that the transformers are hermetically sealed, they require a minimum of maintenance. Normally a visual inspection is sufficient. See the enclosed checklist on page 18. Comments to some of the items in the checklist are listed below. Item 2. Signs of oil leakage The transformer should be checked for leakage in the following places:

Oil level glass, oil filling flange and oil test connection (if provided) Primary terminals

Upper and lower seals against the insulator

Seal between the bottom tank and the cover of the tank

Secondary terminal box and the capacitive terminal (if provided) Oil drain plug (when provided)

Item 3. Damage to the transformer Check metallic, insulator and epoxy parts. The insulator should be cleaned when necessary. Smaller damages to porcelain sheds can be repaired with epoxy resin. Instruction 2750 514-23, "Repair of damaged porcelain insulator", can be obtained from ABB.

Item 4. Correct oil level The oil level glass shall be dark at all ambient temperatures. If the right side of the glass is bright, or if the oil level is visible in the glass, there is an oil leak. This should be identified and rectified as soon as possible. In the event of leakage there is a risk of moisture penetrating into the transformer.

Item 6. Primary connection Check the tightening of all bolts and that the terminals and clamps are free from corrosion.

Item 7. Secondary circuits The secondary terminal box is to be examined for leakage. If rainwater leaks into the box, the cover seal should be replaced. Check that the drainage opening is not blocked. Check that the terminal screws are tightened, and that they are not corroded. The secondary windings of current transformers are to be short-circuited if no burden is connected.

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MAINTENANCE


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Item 8. Earthing Check the tightening of the earthing lead of the capacitor voltage terminal (if any), and of the earthing terminal on the foot of the transformer tank.

Item 14. Tan -measurement The dielectric loss angle (DLA, tan) of the insulation is a measure of the conductivity of the insulation. Good insulation - low conductivity - low tan. Bad insulation - high conductivity - high tan. Any change of tan value is an indication of changed insulation properties. Both normal ageing and moisture penetration into the paper from leakage affect the paper insulation (and the tan value). Limit values for tan of an old CT are difficult to give. Generally tan of 1-1.5 % at 20C can be accepted for 130 kV units and 0,5-1% for higher voltage units it is also very important to be alert for changes. Sudden increases in tan may be a sign of incipient failure.

Tan measurements are recommended to be performed with 3-5 years interval. After 15-20 years of service or if high values are recorded it is recommended to make measurements once a year. If so ordered, CT's can be provided with a capacitive voltage tap, i.e. a tap brought out from the second last foil in the primary winding. The tap is brought through the tank wall via an epoxy bushing and is normally grounded in the tank. This tap can be used for checking tan of the outer part of the primary insulation. Recommended test voltage 2-2.5 kV rms, maximum 5 kV rms. Note: The CT's must be deenergized before the tap is opened. Do not forget to ground tap after measurement. Voltages in the range 3-5 kV will arise on an open capacitive tap.

Item 15. Oil sampling After a long period of operation (20 - 25 years), or when a fault is suspected, for example after a major operational disturbance, an oil sample can be taken from the transformer in order to check the moisture and gas contents.

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OIL SAMPLING, FILLING OF OIL


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5 OIL SAMPLING, FILLING OF OIL Oil testing shall be performed in dry weather and the transformer shall be dry. The transformer must be taken out of service and the top of the transformer must be grounded. Be sure that tools and o-rings are at hand when starting the work. Normally the transformer is under a slight vacuum, so that a small amount of air will be drawn in upon opening. This is quite normal, and in no way endangers the transformer.

5.1 Transformers with gas cushion There is an oil-filling flange on top of the expansion housing of the transformer, through which oil samples can be taken. Before opening the transformer, check that:

spare seals are available

the glass syringe for sampling is clean and dry. Note that the valve of the syringe has three positions: closed, open through the hose and open through the side tap. Make sure that the plunger is not moved with risk of drawing in air.

all suitable tools to open and seal the transformer are available

there is a vessel available for catching surplus oil, in order to avoid oil spills on the ground.

Preferably a special kit is to be used for oil sampling. This kit can be ordered by sending an email to mailbox [email protected] or by calling phone number +46 70 522 19 37

fig. 5.1 fig. 5.2

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Oil sampling (fig 5.1, 5.2): 1.

Loosen the two screws

Lift off the cover

Insert the plastic hose until it reaches as long as possible into the oil

Extract the oil sample according to the instruction 5.1 above

Clean the sealing surfaces

Check the o-rings

Mount the cover (22,5 Nm) 2. The syringe must be rinsed with oil from the transformer. This ensures that

only the transformer oil is sampled, and not air or an eventual remnant oil (saturated with air) from the syringe, a small amount of which may be in the hose. Slowly pull the plunger, checking that oil is drawn and not nitrogen gas from the gas cushion. Fill the syringe with oil. Change the valve position, and empty the oil in the syringe through the side tap into the vessel for surplus oil without removing the hose from the transformer.

3. Reset the valve and fill the syringe once more with oil from the transformer, still being careful not to draw in nitrogen gas. This will be the test sample. In the event that a small amount of nitrogen gas has entered the syringe, hold the syringe with the tap upwards and slowly push the plunger to press out the gas. Make an entry in the report about gas entering the syringe. Close the valve after sampling. Clean the oil spills and the sealing surfaces. Check the O-rings and replace if damaged. Mount the cover and tighten the M8-screws with 22,5 Nm.

4. Mark the syringe with the transformer manufacturing number and fill in the report.

5. Return the syringes with the reports, in the transport box, as soon as possible after completing the sampling to: ABB Power Technologies AB Power Transformers Dept. DD Goods Terminal 55 SE-771 80 Ludvika Sweden

Result A report on the result of the analysis and recommended measurements will be sent from ABB within 2 working weeks upon receipt of the oil samples.

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Enquiries Further information regarding the sampling or the results of the analysis can be obtained from: ABB Power Technologies AB High Voltage Products, Instrument Transformers Dept. IO SE-771 80 Ludvika Sweden Tel: + 46 240 782 000 Fax: + 46 240 783 891

Oil filling (fig 5.1, 5.2): Loosen the two screws

Lift off the cover

Top up with moisture-free and degassed oil

Normal oil level is dimension H1 below top flange surface at +20 C

Clean the sealing surfaces

Check the o-rings

Mount the cover (22,5 Nm) H1= 200 mm for expansion vessel with H2= 375 Fig. 5.1

H1= 270 mm for expansion vessel with H2= 425 Fig. 5.2



5.2 Transformers with metal bellows in cooler These transformers must not be opened because of inner overpressure. Contact ABB Power Technologies AB according to above for oil sampling. See also instruction 1HSE 96002-42, "Oil testing", chapter 2.1 and chapter 2.2 , item a-f.

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STORAGE


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6 STORAGE For storage of IMB current transformers (CT's), the units should be unpacked, checked for transport damages and then be stored in a vertical position. The vertical position is important in order for leveling the supporting, isolation quartz inside the unit. The storage of the CT's shall be made on a flat stable surface, preferably made of concrete, with suitable load carrying capacity. Since the CT has such a low point of gravity and has a comparatively high weight, there is no need for any fastening or support structure.

If a long storage is foreseen, more than 6 months, the storage should preferably be made indoors. The reason for this is that the primary contact surfaces could deteriorate if stored outdoors, also the secondary box when not having any cables connected is not tightly sealed and could be affected if stored outdoors in adverse ambient conditions. Storage in a humid climate without proper ventilation may lead to a discoloration of the aluminium surface. This discoloration is consisting mainly of aluminium-hydroxide and is the result of a chemical process between the aluminium and humidity. The long-term corrosion protection is not influenced, as the aluminium below the surface remains unaffected. The presence of aluminium-hydroxide is no reason for rejection of goods according to Swedish standards.

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TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 36-420


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7 TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 36-420

7.1 Transport CT's of type IMB 36-170, fig. 7.1, are normally transported in vertical position or, only if ordered, in horizontal position. If transported horizontally the unit shall be laid down with the secondary terminal box always facing upward. See on the rating plate which figure is valid, fig. 7.3 or 7.4. CT's of rated voltage 245-420 kV, fig. 7.2, are always transported horizontally.

7.2 Arrival inspection Upon arrival, the crates shall be checked for damage, rough handling, leaking oil etc.

Units for vertical transport may not be energized if by mistake they have been placed horizontally at any time. Under such circumstances nitrogen gas may have entered the insulation system, which makes the unit unsafe. ABB should be contacted in this case for further instructions.

IBM 36-170 IMB 245-420 or IMB 36-170 for high current or big cores

Fig. 7.1 Fig. 7.2

Fig. 7.3 Fig. 7.4

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7.3 Lifting and handling Horizontal transport The unit is lifted out of the crate in the manner shown in fig. 7.5. Note that the strap is to be attached at the top of the insulator, never further down as damage to the insulator may result. Chains or wires may not be used as these can damage the insulator surface. The unit is then placed on the ground resting on the top support as shown in fig. 7.5. Unfasten the top support. The unit is raised to vertical position by lifting it in a strap tied around the top of the insulator, see fig. 7.6. Any further movement of the unit shall be carried out as described below. Vertical transport Lift the unit in the four lifting lugs attached to the base as shown in fig. 7.7. Cross the straps around the primary terminals. Secure the top of the unit to the straps by means of a piece of rope or similar to prevent the unit from tipping over.

Fig. 7.5

Fig. 7.6

Fig. 7.7

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7.4 Installation Each unit shall first be checked for transport damages such as oil leaks, porcelain splinters etc. Check that the oil level is above the oil indication glass. If not, check carefully for the oil leak and contact ABB for further instructions. When mounting the unit on the support, ensure that no free space is between support and unit before the bolt connection is tightened. If free space has been noticed between support and unit, correct with washers, then tigthen the bolt connection. It is not allowed, under no circumstances , to pressure the tranformer base on the support, due to risk for damage which can causes oil leakage on the unit. Mount the outer primary terminals according to separate instruction, which is enclosed in the crate. Also mount other enclosed details, if any, such as surge arresters etc.

Furthermore, check that:

if a core is not intended to be used, the winding has to be effectively short- circuited across the end terminals and connected to earth (min. 6 mm wire).

NOTE! Never open a secondary winding of a CT in service. Hazardous secondary voltages can be the consequence.

the capacitive tap ("F-terminal"), if any, is to be earthed to the tank if not being used for any purpose.

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TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 420 and 800


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8 TRANSPORTATION, LIFTING AND INSTALLATION OF CURRENT TRANSFORMER TYPE IMB 420 and 800

8.1 Transport Current transformers of type IMB 420-800 are always transported in horizontal position. The transformer shall always be turned according to fig. 8.3 when horizontal.

8.2 Arrival inspection Up on arrival crates shall be checked for damage, rough handling, leaking oil etc.

Fig. 8.2 IMB 420 and 800

with expansion tank

Fig. 8.1 IMB 420 and 800

with cooler

Always up

Fig. 8.3

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8.3 Lifting Horizontal lifting The unit is lifted out of the crate and is placed on supports in the manner shown in fig. 8.4. Note the strap is to be attached at the top of the insulator, never further down as damage of the insulator may result. Also check that the lifting strap do not touch the top shield. Chains or wires may not be used as these can damage the insulator surface. The unit is raised to vertical position by lifting it in a strap tied around the top of the insulator according to fig. 8.5. Any further movement of the unit shall be carried out as described below. Vertical lifting Lift the unit in the four lifting lugs attached to the cover as shown in fig. 8.6. Cross the straps around the primary terminals. Secure the top of the unit to the straps, by means of a piece of rope or similar, to prevent the unit from tipping over.

Fig. 8.5

Fig. 8.6

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8.4 Installation Each unit shall first be checked for transport damages such as oil leaks, porcelain splinters etc. Check that the oil level is above the oil indication glass. If not, check carefully for the oil leak and contact ABB for further instructions. When mounting the units ensure that the support structure is flat. If not, correct with washers. Deformation of the CT bottom which otherwise occurs is not accepted. Mount the outer primary terminals according to separate instruction enlcosed in the crate. Also mount other enclosed details, if any, such as surge arresters etc. Furthermore, check that:

if a core is not intended to be used, the winding has to be effectively short-circuited across the end terminals and connected to earth.

NOTE! Never open a secondary winding of a CT in service. Hazardous secondary voltages can be the consequence.

the capacitive tap ("F-terminal"), if any, is to be earthed to the tank if not being used for any purpose.

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CHECKLIST FOR IMB


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9 CHECKLIST FOR IMB What to check When Check if

1. External damage on packing A Boards broken. Signs of rough handling

2. Signs of oil leaks A,B,D,E, F,G,J Oil spots visible (even though packing is undamaged)

3. Mechanical damage on transformer B,E,F,G,J Terminals bent, porcelain damaged

4. Oil level B,D,E,F,G,J Oil visible in sight glass. (Glass being dark)

5. Support structure, plane, horizontal C Transformer resting on all mounting feet

6. Primary connections C,F,G,I,J Minimum one flexible link. Good contact

7. Secondary circuits C,I Properly connected. Secondary windings not left open

8. Ground connection C,E,F,G,I,J Transformer tank grounded

9. Capacitive tap (if supplied) C,I Grounded or used. Not left open

10. Secondary current D,E,F,G,I At correct (rated) value

11. Secondary terminal box F,G Tight and free from corrosion

12. Metal parts F G Free from corrosion

13. Connections and equipment F,G Undamaged and free from corrosion 14. Dielectric loss angle test, method depends on local practice H

Value depends on age, voltage and temperature change in value from last reading is important

15. Oil sample, gas analysis H Low concentration of critical gases

When to check A At receiving of transformer

B At unpacking

C During erection

D After energizing

E Weekly/monthly routine checks

F Annual routine checks

G Every fifth year

H After 15-20 years. Careful check of condition

I After reconnections, change of burdens etc.

J After fault conditions, short circuits etc.

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ABB Power Technologies AB High Voltage Products SE-771 80 LUDVIKA SWEDEN Telephone: +46 (0) 240 78 20 00 Telefax: +46 (0) 240 78 ?? ??


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