GEa220000a Page 1 Mardi, 13. avril 1999 8:40 08 three...

three-phase HV / LV transformers

mineral oil-immersed distribution models

Instructions forinstallation,

commissioningand maintenance

Contents

taking delivery 3

handling 4

installation 6

HV and LV connections 15

transformer operation in parallel 19

maintenance 20

after-sales service 23

precommissioning checks 24

GEa220000a Page 1 Mardi, 13. avril 1999 8:40 08

2

France Transfo

Warning

This guide intended for standard range oil-immersed distribution transformers as described in France Transfo product catalogues.

If in doubt, our After-Sales Service remains wholly at your disposal.

Tél. (33) 03 87 70 57 72fax: (33) 03 87 70 56 21


3

France Transfo

On receipt of equipment, ensure that it corresponds with your order by checkingmachine characteristics indicated on the rating plate (capacity, voltages, etc.)

Distribution transformers are delivered "ready for installation", i.e. completely filled with oil and with accessories either fitted or delivered separately.

When unloading, check that the transformer has not been damaged during transport (broken insulators, damaged tank, etc.) and that all accessories ordered have been delivered.

Also check that the tank lead seal, fixed to one of the cover screws (usually at a tank corner) is intact, because its breakage causes the transformer guarantee to lapse.

Should the unit have been damaged or if accessories ordered are found to be missing:

m

enter a reservation on the final haulage contractor's delivery note and confirm by recorded delivery letter within 3 days.

m

write a report and send it immediately to your supplier (France Transfo or a dealer as the case may be).

Taking delivery of equipment and preliminary checking


4

France Transfo

Transformers are usually stabilised during transit by heavy timber bearers fixed tothe vehicle bed. It is therefore essential to remove these bearers before lifting thetransformer unit off the vehicle.

Transformer units incorporate specific handling devices.

m

Lifting by means of slings or a lifting beam

(figure 1)

The unit must be handled using the 2 lifting rings located on the transformer cover.

m

Hauling

(figure 2)

The transformer must only be hauled from its chassis. 30 mm diameter holes have been drilled in the ends of chassis members for this purpose, except in the case of low capacity units or those built to a special specification. Hauling must only been undertaken in two directions: along and perpendicular to the chassis centre-line.

m

Handling using a forklift truck

(figure 2)

Forks must only lift the chassis from within the inverted channel sections, with idler rollers removed.

or

1

hole for hauling2

Handling


5

France Transfo

m

Positioning of idler rollers

(figure 3)

M

either by lifting with slings or a lifting beam.

M

or by lifting with a forklift truck.In this case, position the forks of the truck within the inverted channel sections.Place heavy timber bearers, which are slightly higher than the idler rollers, cross-wise beneath the ends of the chassis members and lower the unit onto these tim-bers.Position jacks and remove timber bearers one by one.At the same time, fix each idler roller in the required position (idlers swivel in 2 directions) using the locking screw.Then, remove the jacks and allow the unit to rest on its idler rollers.

Ground clearance due to the idler rollers is essential for transformer cool-ing.

3

timber bearer idler rollers

Handling


6

France Transfo

Ensure that machine characteristics shown on the rating plate correspond with installation conditions: primary voltage(s), tapping links.

This plate may be moved and attached to any side of the tank so that it is visible once the machine is in position.

In general, installation must comply with the requirements of IEC Standard

71-1, 2 and 3 in relation to insulation co-ordination.

E.g.: case of overhead-underground connection to be protected by lightning arresters installed at both ends of the HV cable.

m

unit to be installed at a maximum altitude of 1000 m, unless otherwise specified with order, because air rarefaction adversely affects cooling of the windings.

m

unless otherwise specified with order, transformers of standard design are sized in accordance with IEC Standard 76 for the following ambient temperatures:

• maximum : 40°C• average daily : 30°C• average annual : 20°C• minimum : – 25°C

When the transformer is live, the ambient temperature inside the plantroom must comply with the above values, unless the transformer has been specially designed on the basis of a particular specification.

Installation


7

France Transfo

Determining the height and cross-sectional areas of ventilation wall openings (figure 4)

In the general case involving natural cooling (AN), the purpose of the plantroom ventilation system is to disperse the heat, resulting from the total heat losses generated by the operating transformer, by natural convection.

An efficient ventilation system comprises a fresh air inlet wall opening of cross-sectional area S positioned low down in the room, and air outlet opening of cross-sectional area S' positioned high up on the opposite wall of the room at a height H above the air inlet opening.

It should be noted that restricted air circulation around the unit causes a reduction in available power. For this reason, the transformer must be positioned at a minimum distance of 200 mm from any solid wall.

Design calculation:

P = sum of losses under no load and losses due to load on transformer, expressed in kW at 75°C, plus losses generated by any other unit in the same room.

S = cross-sectional area of fresh air inlet wall opening (deduct possible area obstructed by grill), expressed in m

2

.

S’= cross-sectional area of air outlet wall opening (deduct possible area obstructed by grill), expressed in m

2

.

H = difference in height between inlet and outlet wall opening centre-lines, expressed in m.

and

This formula is valid for an average annual ambient temperature of 20°C and at a maximum altitude of 1000 metres.

H

S

S’

Groupe Merlin Gerin · Usine de Maizières-lès-Metz (Moselle) France nº 216540

4

200 mm mini

S 0 18P,H

-----------------= S ′ 1 10 S×,=

Installation


8

France Transfo

Forced ventilation of plantroom (figure 5)

A ventilation system of this type is required for a cramped or poorly ventilated plantroom, or for a room in which the ambient temperature is much higher than the temperature outside, in view of the ambient temperatures used for designing the transformer. Should the transformer be frequently overloaded, a forced ventilation system can help to disperse the heat generated by the unit, although it will not reduce the adverse effects of such overloading on the equipment's life.

An air extract fan discharging outside the plantroom

may be fitted to the outlet wall opening, located at high level, in order to increase natural convection in the room; this fan can be thermostat-controlled.

Recommended discharge rate (m

3

/s) at 20°C = 0.10 P

P = total heat losses to be dispersed, expressed in kW, for all equipment installed.

Groupe Merlin Gerin · Usine de Maizières-lès-Metz (Moselle) France nº 216540

H

S

S’

5

200 mm mini

Installation


9

France Transfo

Setting the voltage commutator

Commutator setting is carried out in the following way:

- unscrew fully the red locking knob,

- simultaneously pull and turn the commutator rotating head until the pointer indicates the right setting,

- push the rotating head back ensuring that the pointer is engaged in the notch for the setting required,

- rescrew fully the red locking knob

©Tapping links

Set the tapping point commutator to the required position:

Pos. 1: upper primary voltage

Pos. 2: rated primary voltage

Pos. 3: lower primary voltagered locking knob

commutator rotating headindex

Adjustments to tapping point or voltage commutators must be undertaken with the transformer off-load and de-energized.

1

2

©Double primary voltage

For units using 2 primary voltages, select position as required.

Pos. 1: HV1

Pos. 2: HV2

Installation


10

France Transfo

Statutory restrictions for oil-immersed transformers

Each country issues its own regulations covering the installation of oil-immersed transformers on its territory. These regulations invariably respond to concerns for the protection of people, property and the environment. Available protection systems depend on the technology adopted for the transformer concerned.

When the unit is in service, the volume of the dielectric fluid used to cool its coils (usually mineral oil complying with IEC Standard 296) varies continually, due to temperature variations in the windings.These volume changes must be "absorbed" by a suitable expansion system which has given rise to two distinct technologies:

Hermetically sealed type transformer

The unit's tank, containing the active part, is hermetically sealed: variations in volume are absorbed by expansion of the cooling fins positioned around the tank, the dielectric fluid is not exposed to the surrounding air.

Maintenance of this type of unit is thus greatly reduced (see page 20).

Installation


11

France Transfo

Protection accessory: the protection relay (figure 6)

Fitted directly to the transformer cover, this relay ensures protection against internal faults, prolonged overvoltages and fire risks associated with the use of inflammable dielectric fluids.

The accessory continuously monitors:- dielectric fluid level,- tank internal pressure,- dielectric fluid temperature at two different thresholds.

To operate properly, the protection relay must be fully filled with fluid (level higher than the float visible in the transparent section of the unit). If this is not the case, check the instructions which appear inside each casing.

To ensure optimum protection, the following action and adjustments are recommended:

Finding Recommended adjustment

Fault detected Action to be taken

Gas emitted or drop in level Large float at the top

Serious fault

De-energize unit

Pressure switch 0.20 bar

Serious fault

De-energize unit

Thermostat threshold 1 90°C

Overvoltages

Activate alarm

Thermostat threshold 2 100°C

Overvoltages

De-energize unit

6

oil

sensors

Installation


12

France Transfo

Faults detected on live transformer unit

m

Dielectric fluid level is detected as lowThe protection relay is empty and the large float is at the bottom.May be due to:- air entering; there must be a dielectric fluid leak and thus oily stains should be

visible on the ground.Accurately localise the fault, carry out repair, then recheck the level with the body of fluid at a temperature of 20°C, before switching the unit live again (see oil grades, page 20),

- internal gas emission: gas should be sampled using a syringe and then analy-sed.Whilst awaiting results, under no circumstances should the transformer be switched live again because a risk of total destruction exists.Should gas analysis reveal an inflammable gas, contact FRANCE TRANSFO After-Sales Service (see page 23), or your SCHNEIDER correspondent.

m

Overheating is detectedThis may be due to:- improper cooling of the transformer (insufficient air flow around unit or plant-

room ventilation),- continuous overvoltage.

m

Excess pressure is detectedThis may be due to:- overheating: see above,- internal gas emission: see above,- topping up of dielectric fluid with the body of fluid below 20°C; drain the

overflow with the transformer de-energised and the dielectric fluid at 20°C.

Installation


13

France Transfo

Breather type transformer with expansion tank (figure 7)

The transformer tank is connected by pipework to an expansion tank, mounted above the unit, which ensures that the dielectric fluid level remains sufficiently high in the transformer tank: variations in dielectric fluid volume are absorbed by the expansion tank which remains at atmospheric pressure.

This type of unit therefore requires maintenance which is both regular and suited to the climatic conditions in the vicinity of the transformer (see page 21).

Protection accessory : the Buchholz relay

Fitted to the pipework linking the expansion tank to the transformer tank, this accessory ensures protection against internal faults only, by monitoring dielectric fluid levels and fluctuations.

To ensure proper operation, the Buchholz relay must be completely bled of air.

Faults detected on live transformer unit

m

Dielectric fluid level is detected as low.The Buchholz relay is partially empty, the top level float is at the bottom.Reasons for this low fluid level are the same as those given for the protection relay (see page 11) but in the present case, the relay will activate automatically the alarm.

m

Major discharge of oil towards the expansion tank is detectedA violent emission of gas, resulting in serious electrical faults within the transformer tank, leads to a large discharge of oil to the expansion tank, which causes the Buchholz relay bottom float to pivot; the transformer unit must be de-energised immediately and permanently.Contact FRANCE TRANSFO After-Sales Service (see page 23), or your SCHNEIDER correspondent.

7oil

Installation


14

France Transfo

Dielectric fluid retention system

In an environmental protection context, the retention system used must be capable of containing the total quantity of dielectric fluid, unless otherwise specified by local regulations.

It may comprise:- a raised door threshold if the plantroom floor is oil tight,- a low oil tight wall around the transformer,- a steel trough positioned beneath the transformer.

In the last two cases, ensure that the system does not adversely affect transformer cooling by preventing air circulation around the tank cooling fins.

Installation


15

France Transfo

Bushing type

Transformers may be provided with the following connections.

Example of bushing choice for LV = 400 V.

kVA 100 160 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150

LV busbar bushings — — 1250A 1250A 1250A 1250A 1250A 1250A 1600A 2500A 2500A 3150A 5000A 5000A

LV porcelain bushings

250A 250A 630A 630A 630A 1000A 1000A 1600A 1600A 2500A 2500A 3150A 4000A 5300A

385

M 12

250A

HV connections to plug-in bushings

locking ring locking ring

HV connections to porcelain bushings DIN 42531

N.B.: under no circum-stances should porcelain HV bushings be used with cover-protected HV systems.

with draw-out angle connector

with draw-out straight connector1250A

31,5

63

31,5

12

155

52

Ø 11 Ø 14,5

31,5

1600A

Ø 14,5Ø 11

221

52

12

31,5

31,5

97,5

31,5

6331,5

2500A

250

52

12

Ø 11Ø 14,5

106,

5

31,5

31,5 31,5100

31,5

3150A

250

45

12120

50

50

50

Ø 18

35

5000A

310

45

2012050

50

25

50

135

Ø 18

DT 250A

138

M 12

DT 630A

178

M 20

DT 1000A

263 M 30

1060

26 17

26Ø 1460

DT 2000A

340

10050 25

Ø 14

15

50

M 42

100

DT 3150A

15

120

372

12060 30

60Ø 14

M 48

5300A

20

165

465

150

Ø 65

150

LV connections to busbar bushings (only used above 250 kVA units)

LV connections to porcelain bushings (mandatory for 100 and 160 kVA units) DIN 42530

HV and LV connections


16

France Transfo

Assembly and tightening torque

Bushings must not be subjected to stresses resulting from cable or busbar connections; such loads can cause leaks at various joints.

Furthermore, the following connection details and tightening torque values shall be complied with:

F

HV or LV connection to porcelain bushing (U ≤ 52 kV - M12 stud)

nut tightening torque: 25 Nm

M12 brass stud

load in accordance with I.E.C. 137:connecting terminal inclined < 30°, F = 50 daNconnecting terminal inclined > 30°, F = 30 daN

clea

ranc

e:

appr

ox. 5

mm

reminder:1 N.m = 0.102 mkg1 mkg = 0.98 daN.m

LV connection to busbar bushing

steel bolt locknut

end lug

large diameter metric series steel plain washers

tin-plated copper busbar bushing

N.B.: end lug, bolt and washers are not supplied.



17

France Transfo

Table of tightening torque values

Tightening torque given in N.m.

Tightening tolerance ± 20%.

The above torque values are for assemblies incorporating plain washers. However, we recommend the incorporation of contact washers behind the plain washers; the above torque values should be increased by 35% if this is done.

Steel and stainless steel bolts shall be greased prior to fitting.

If aluminium bolts are used, please refer to manufacturer's recommendations.

Bolts Class 6.8anticorrosion -treated steel

Class A2-70 and A4-70 stainless steel

Class A2-80 and A4-80 stainless steel

Brass

M8 15.2 15.5 17.7 7.6

M10 30 30 35 15.1

M12 52 53 60 25

M14 83 85 97 41

M16 130 133 152 55



18

France Transfo

Protection

HV bushings

m

Draw-out connectors (straight or angle) may be kept plugged into the plug-in bushings using a padlockable locking device (padlock / lock not supplied);Release of this locking system may be made conditional on prior isolation of the transformer from the HV supply (figure 8);

m

Porcelain bushings may be fitted with a sealable protective cover, whose design will depend on the HV voltages, the configuration and number of cables.

LV bushings

m

Busbar or porcelain bushings may be protected by a sealable cover.

8



19

France Transfo

Connection of several transformers in parallel leads to the following constraints:

m

If their power outputs are different, the total available combined power output will be slightly less (< 10%) than the sum of the power outputs for each transformer coupled separately.

m

The power output of the largest transformer should not be more than twice that of the smallest unit.

m

Transformers must be supplied by the same network.

m

Connections must be of the same length and have similar characteristics between the LV terminals of the different units and the coupling circuit-breaker (figure 9).

m

Couplings must be identical.

m

Short-circuit voltages must be identical (±10%).

m

Differences in secondary voltages between the different units must not exceed 0.4%.

m

The switch shall be positioned identically on each unit.

9recommend to advise

LV

Transformer operation in parallel


20

France Transfo

Mineral oil and component materials

The transformer is filled with mineral oil complying with ICE Standard 296.

Transformer component materials are free of polychlorobiphenyls (PCB's), polychloroterphenyls (PCT's) and polychlorobenzyltoluene (PCBT).Moreover, the PCB content of this unit is guaranteed to be less than the detectable threshold (2 ppm*) in strict compliance with standards currently in force.

Hermetically sealed type transformer

Under normal operating and environmental conditions, maintenance of this transformer is reduced. It is in fact limited to regularly checking the tightness of connections and visual inspection of transformer oil tightness.Under conditions of extreme pollution (depositing of dust, salt, chemicals, etc.), cleaning of porcelain or busbar bushings may be required.As long as the dielectric fluid has not been exposed to the air for a particular reason (tank opening, repairs, fitting of accessories, topping up of oil, etc.), one dielectric withstand test, on a sample taken from the bottom of the tank (minimum breakdown voltage 30 kV), every 10 years is sufficient.The transformer is hermetically sealed and has no gas cushion. In other words, filling and closure have been carried out in such a way that pressures are balanced (internal and external atmospheric pressure) under conditions approaching normal, i.e. temperature of 20°C and pressure of 1013 mbar.

* parts per million.

Ce transformateur est garanti réalisé avec des

constituants neufs et exempts de tout élément de

récupération susceptible d’avoir été pollué par

des PCB.

We warrant that this transformer has been

manufactured with new material and is totally free

from second hand parts polluted with PCB’s.

Label placed on all transformers

Maintenance


21

France Transfo

If necessary, this transformer may be opened in accordance with the following recommendations:

m

Transformer is hot (

θ

> 20°C)

The unit's internal pressure is higher than atmospheric and opening it causes leakage of some dielectric fluid which can only be reinjected in full, once its temperature has returned to 20°C.Until this occurs, the unit can fulfil its functions. However, replacement of all the dielectric fluid lost at the earliest opportunity is preferable.

m

Transformer is cold (

θ

< 20°C)

The unit's internal pressure is lower than atmospheric and opening it causes a drop in oil level in the tank. After servicing and topping up dielectric fluid, if required, put the unit back into operation and purge when hot.To prevent excess pressure in the tank, the volume of dielectric fluid which may have been added (during topping up) should be drained, once the unit's operating temperature has risen to 20°C.

Maintenance


22 France Transfo

Breather type transformer with expansion tank

Because the dielectric fluid is exposed permanently to the surrounding air, the frequency of oil quality checks must be increased: once a year is an absolute minimum, which should be further increased if a gradual deterioration of fluid dielectric withstand is observed (reminder: minimum breakdown voltage: 30 kV).If an air dehumidifier has been fitted to the expansion tank to filter the incoming air, the colour of the silica gel it contains should be monitored:

- blue colour : silica gel is in a good condition for ensuring dehumidification,- pink or white colour : silica gel has absorbed humidity and has become inef-

fective, it should therefore be replaced (supplied by our After-Sales Service, see page 23).

Also check that the glass, located at the bottom of the dehumidifier, is filled with oil to the required level, in order that dust carried by the surrounding air flow is effectively retained.

Maintenance


23France Transfo

When making enquiries or ordering spare parts, it is essential to quote the main characteristics given on the rating plate and, in particular, the unit serial number. TECHNICAL MEMO

(data to be copied from unit rating plate)

No. :

Year :

Power output : kVA

Frequency : Hz

Cooling :

Coupling :

Rated high

voltage : kV

Low voltage : V

Mass of

dielectric : kg

Total mass : kg

Groupe Schneider · Usine de Maizières-lès-Metz (Moselle) France

NAL - 226489

complying ref.HzTREEPHASE TRANSFORMERaccording to year

impedancevoltage connection%

high voltage low voltage

pos 3 V

volta

ges

pos 4 V

pos 1 Vpos 2 V

pos 5 Vcurrents A

V

A

kVA Nº insulation level KV

nature windings

primary in service on

cooling

dielectricmass diel. kg

mass total kg

After-Sales Servicetel.: (33) 03 87 70 57 72fax: (33) 03 87 70 56 21

After-Sales Service


24 France Transfo

Operations prior to connecting transformer check data given on rating plate in relation to needs (power output, voltage,

etc...)

ensure transformer plantroom is clean and cannot flood

ensure correct ventilation- plantroom air vents are clear and of suitable area (pages 7 and 8)- sufficient clearance between unit and solid walls in plantroom (page 7)- sufficient clearance between unit and floor (unit resting on idler rollers -

page 5)

check general condition and cleanliness of transformer

measure values of insulation resistance using a 2,500 V insulation tester

If the measured values are significantly less than the usual values, please call your After-Sales Service (page 22).

check oil tightness of unit (welds, gaskets, valves, drains, plugs).

Checks carried out on: ......................................... by: .........................................

Measuring points Measured values Usual values for mineral oil

HV / earth

LV / earth

HV/LV

MΩ

MΩMΩ

250 MΩ

250 MΩ

50 MΩ

Precommissioning checks


25France Transfo

Operations prior to switching transformer live ensure there is no foreign body on the unit (metal filings, nuts and bolts, etc.)

if the transformer is an hermetically sealed type unit fitted with a protection relay, check that the large float is at the top and that the drain is properly closed (close by turning clockwise). Refer to instructions supplied with each transformer in relation to testing.

if the transformer is a breather type unit with an expansion tank and Buchholz relay, check that all air bubbles have been bled from the latter unit and carry out relay testing using the devices provided for this (rod to be pushed or pulled to activate alarm or trip).Check condition of silica gel in the dehumidifier and the level of oil in the bot-tom glass vessel.

ensure that cables and busbars are properly supported; no loads should be applied to the transformer connection lugs.

check wiring of protection or ventilation auxiliaries with respect to:- insulation clearances and cable fixings,

operation.check tightness of connections (pages 16 and 17)

check earthing continuity - to ensure the safety of operating personnel, the transformer earthing system must be grounded.

check that rotating switch head is correctly set to, and locked in, the required position.

ensure that ventilation grills are clear.- if unit is to operate in parallel, check short-circuit voltage, phase consistency

and voltage ratio (page 19)

Precommissioning checks


26 France Transfo

notes


N°

iden

t. T

VA

: FR

78

3578

0110

9 •

SA

au

cap

ital d

e 10

280

000

FR

F –

RC

S M

etz

B 3

57 8

01 1

09 •

Imp

rimé

en F

ranc

e

France TransfoBP 10140F 57281 Maizières-lès-Metz CedexTel.: (33) 03 87 70 57 57fax.: (33) 03 87 51 10 16

GEa 220000 a

Since this manual was edited, a number of alterations may have been incorporated in the equipment you have received. The sole reason for this resides in our constant efforts to improve the quality and performance of our equipment.

Edited by: France Transfo - 03/99Typesetting and illustrations: COREDIT


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