Transformer Training

4

What is transformer :

an electrical device that converts AC electric energy at

one voltage or current level to another voltage or current

level at the same frequency

G

Load Distribution Transforme r 20 / 0.4 kV Distribution Transforme r 20 / 0.4 kV Interconnecti on Transformer 150 / 20 kV Interconnecti on Transformer 150 / 20 kV Step up Transforme r 20 / 150 kV Step up Transforme r 20 / 150 kV 150 kV 20 kV _{0.4 kV}

6

Basic Principle of Transformer:

- consist of two inductive coils (primary and secondary) which are electrically separated but magnetically linked

- mutual induction between the two circuit

- if one coil is connected to a source of alternating voltage, alternating flux is set up in the laminated core which is linked with the other coil. Then it produces mutually induced emf.

- If the second coil circuit is closed, a current flows in it and so electric energy is transferred.

N

f

E

=

4

,

44

.

.

φ

_m

.

1 2 2 1 N N I I = 2 1 2 1 V V E E = Φ V 1 V 2 N 1 N 2

I p U_p N_s N_p I s _U s ΔU

»

»

S

S

_IECIEC

= U

= U

_pp

x (I

x (I

_ss

x N

x N

_ss

/

/

N

N

_pp

)

)

»

»

S

S

_{ANSI ANSI}

= U

= U

_ss

x I

x I

_ss

»

»

_{Cooling capacity =Cooling capacity =}

»

»

IEC 60076 = max. load loss + no load loss 100% excitation +

IEC 60076 = max. load loss + no load loss 100% excitation +

sun rad.

sun rad.

»

8

The party active is immersed in the tank by air or gas

The party active is immersed in the tank by dielectric liquid

There are two type transformer based on its insulation :

The expansion of dielectric takes

place in an expansion tank placed

10

Expansion of the dielectric is

absorbed by compensating on the

The oil volume expansion is

compensated with

inert gas layer between the surface of the dielectric

12

micro ordinat eur

¾

HV 60° oblique winding patented by

AREVA

three dimensional

computerized

control automatic

and vertical

winding machine

fully automated

casting and

mixing under

vacuum

¾ No liquid dielectric

¾ no danger for environment due to oil leakage ¾ no loss of dielectric strength due to oil leakage ¾ no need for oil dams or containment systems

¾ no fluids to be targeted for regulation in the future resulting in costly change-outs

¾ Excellent Fire resistance ¾ self-extinguishing, ¾ fire retardant, ¾ not explosive,

¾ no release of toxic or corrosive products and opaque smokes in the event of fire

¾ Excellent response to service conditions ¾ High short circuit withstand ratings

¾ Resistant to mechanical and thermal stress caused by over-loads, over-voltages and harmonics

14

- Core

- Cooling equipment

- Winding

- Termination

- Cooling medium

- Control/Protection

- Insulation structure

‰

Tank cover.

‰

Internal connection bushings

‰

Tap changer barrel and lead

outs connection

‰

Core & coil assembly

‰

Yoke clamping

‰

Pedestal

16

T

ransformer for Hazardous Area

Basic description :

X Definition : Those areas where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust or ignitable fibers

X For hazardous areas with risks of explosion, specific electrical equipment is required.

X Application fields: Based on decades of filled tested experience in electrical generation and distribution for both offshore and onshore installations

18 • Arcs and sparks produced by the normal operation of equipment, like motor

starters, contactors and switches, can ignite a hazardous location atmosphere

• The high temperatures of some heat-producing equipment, such as lamps and lighting fixtures, can ignite flammable atmospheres if they exceed the ignition temperature of the hazardous material. The National Electrical Code requires special marking of heat-producing equipment with temperatures above 100°C (212°F)

• Electrical equipment failure is another way an explosion could be set off. A burn out of a lamp socket or shorting of a terminal could spark a real disaster in a hazardous location

Zone 0 : an area in which an explosive gas atmosphere is continuously present or present for long periods Zone 1 : an area in which an explosive gas atmosphere is

likely to occur in normal operation

Zone 2 : an area in which an explosive gas atmosphere does not normally exist

Type of Area IEC NEC

Continuous Hazard ZONE 0 DIVISION 1 Intermittent Hazard ZONE 1 DIVISION 1 Hazard under abnormal conditions ZONE 2 DIVISION 2

20 SEALING FITTING

CONDUIT CABLES EXPLOSION PROOF TERMINAL

¾ Standard Applicable

IEC 76, ANSI C-57 and AS 2734

Information required with enquiry and order:

A.General Information - dry type or oil immerse - single or 3 phase

- frequency

- indoor or outdoor - type of cooling

- rated power and voltage

- tapping (if needed); on load or off load - highest voltage level

- method of earthing

- BIL and power frequency - connection

- Accessories

B. Special information - impedance

- altitude and ambient temp. - special installation space

22

- Part active

: this is the main part of transformer, consist of core magnetic and winding

-

Bushing

-

Cooling Device

: oil (for oil immersed transformer), radiator, fan

- Protection Device

: Bucholz relay, protection relay for OLTC RS 2001, pressure relief device, pressure vacuum gage & bleeder

- Accessories

: Oil Level Indicator (OLI), Oil Temperature Indicator (OTI), Winding Temperature Indicator (WTI), etc

- Magnetic core

- Low voltage winding - High voltage winding - Active part clamping

24

LV Winding

Gradins

HV Winding

Choice of gradins used must be as

close as possible to the circle

section

1 3 4 5 2 1 Top yoke 2 Bottom yoke

3 Left outer limb

4 Center limb

• There are two kinds of magnetic core stacking :

1. Flat yoke :

The silicon steels of the

yoke are arranged with

the same distance to

each other

26

2. Non flat yoke :

The silicon steels of the

yoke are arranged like

stairs

There are three kinds of

wire used for winding:

1. Round wire (email)

2. Rectangular (meplate)

3. Foil (Bande)

Current density (δ)

limitation used :

Copper wire :

1.4 <= δ <= 4.4 A/mm

2

Aluminium wire :

0.6 <= δ <= 2.4 A/mm

2

28

Winding Temperature Indicator

Function :

Winding Temperature Indicator

1. Case 2. Locking Glass Ring 3. Fixing Rear Flange 4. Air Hole 5. Capillary Output 6. Dial 7.Microsw. Setting Dial 8. Max. indicating pointer 9. Microsw. Setting Pointer 10. Junction Box 11.Glass or polycarbo-nate window 12. Potentiometer for heating resistance adjustment

30

Oil Temperature Indicator

Function :

To measure the oil temperature inside power transformer tank

Oil Temperature Indicator

1. Case

2. Locking Glass Ring 3. Fixing Rear Flange 4. Air Hole 5. Capillary Output 6. Dial 7.Microsw. Setting Dial 8. Max. indicating pointer 9. Microsw. Setting Pointer 10. Junction Box 11.Glass or polycarbo-nate window

32

Oil Level Indicator

Function :

to measure the level reached by the oil in a transformer conservator

Pressure Vacuum Gauge

Function :

To check the vacuum pressure inside the tank

34

Sudden Pressure Relay

Function :

To minimize the damage on the equipment caused by excessive gas pressure that occurred from internal arcing in oil filled transformers.

Pressure Relief Device

Function :

An equipment to relieve large volumes of gas or insulating fluid rapidly when the pressure inside a transformer reaches a pre-determined limit.

1. Measurement of Winding Resistance 2. Measurement of voltage ratio

3. Measurement of no-load loss and no-load current

4. Short duration induced AC withstand voltage test (induced overvoltage test) 5. Measurement of short-circuit impedance and load loss

38

1. Lightning impulse test 2. Temperature rise test

1. Measurement of partial discharge 2. Measurement of sound levels

Carefully examined to detect any signs of damage in transport: • Damaged or deformed packing blocks

• Dielectric stains or leaks

• Broken pieces of wooden crate • Cracked or spilled bushings • Broken or damaged wiring

• Low nitrogen pressure on pressure gauge • No dielectric oillevel reading on gauge • Damaged tank body

42

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! USE THE LIFTING AND JACKING POINTS SHOWN ON THE GENERAL ARRANGEMENT DRAWING !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

¾ Purpose:

To condition oil before filling of transformer

44

9

Check the list of components

9

Check the condition of parts

9

Any operation involving opening a passage into the inside of the

transformer must be done in the shortest time and good weather

9

Installation, erection, and commissioning of transformer may only

be carried out by qualified, skilled personel and only in

Tools should be ready for Erection :

DESCRIPTION QUANTITY REMARK

Crane 5 ton 1 unit Lifting and assembling

Sling wire for crane 5 ton 1 set

Oil filtering/purely and vacuum machine 1500 - 3000

lt./hours equipment with horse 1 unit Filling & treatment oil if necessary

Torque wrench 1 set

Spanner : 8mm, 13mm, 22mm, 30mm etc 1 set

Adjustable wrench 1 set

Screw driver (plus & minus) 1 set

Multi tester 1 unit

Megger 1 unit

46

¾

Take a sample, to ensure it meets the requirements for dielectric

strength

¾

DO NOT pour dielectric directly into the transformer

¾

Oil should flow in through a valve located below the level of the

dielectric already in the transformer

48

1. Inject N2 gas through N2 injection valve

2.

Control N2 gas pressure (± 6 psi.)

3.

For leakage test, the voltage regulator is applied by 6-psi

pressure for 24 hours

4. After the test the pressure is down to 2 psi on pressure

vacuum gauge

¾ Protective Accesories and Setting Values

SET VALUES No NAME OF PROTECTIVE _ACCESSORIES

ALARM TRIP

NOTE

1 Sudden Pressure relay OK

OK

-2 Oil temperature indicator 85o ₉₅o _Adjustable

3 Winding temperature indicator

- Winding temperature 95o ₁₀₅o _Adjustable

- Fan (future) • start 70o _{/stop 60}o _{C 70}o _{- Adjustable}

4 Oil level indicator for main tank Min level

50

¾ Inspection and checking before operation

No. CHECK ITEMS DESCRIPTION SPECIFIED REMARK

1 Out line drawing Specification Compliance with drawing and specification

2 Oil level Main tank Level gauge to read correctly for existing level and oil temperature

1. Valves

2. Radiator valves 3 Valve position

Open and close position 3. Other valves

4 Off load tap changer Manual operation through all tap

position As specified

1. Insulation resistance of

windings 1 MΩ/kV

As reference

2. Ratio and polarity Acc. to specification 3. Dielectric strength of oil See CT606MO 5 Electrical tests

4. Alarm, tripped, control circuits, and auxiliary circuit

1. Wired properly and comply with wiring 2. Contacts open or close

¾ Inspection and checking before operation (Cont’d)

No. CHECK ITEMS DESCRIPTION SPECIFIED REMARK

6 Earthing Tank and Marshalling kiosk It should be connected to earth

1. Porcelain 2. Spark Gap

7 Bushing Clean

Proper continuity and tightness

3. Connected

8 Other Cleans rust Cleans Clean and

52

Efficient protection should prevent the transformer from any incident. ¾ Setting of Protective Devices

Most of the protective devices, ordered wtih the transformer are installed and pre-adjust at the factory.

The choice of the protective device thet is not directly installed on the

transformer must take into account the effect of switching transient voltages and currents caused by energising the transformer.

¾ Inrush Current

Energising a transformer gives rise to high over current. This inrush current is between 3 – 5 times the rated current of the transformer.

This current reduces accordingly to an exponential law whose time constant depend on the winding resistance and the secondary load.

NORMAL OPERATION

¾ All radiators valves must be opened, and all other valves closed ¾ The tap changer secured in correct position.

54

EMERGENCY OPERATION ¾ Over load

Can be operated under permissible load, which is given according to IEC publication 354

¾ Over excitation

¾ Maximum duration of short circuit in second is 2 second at LV and HV feeder. 1 2 3 5 7 10 20 ₃₀ 50 70 100 200 300 500 700 100 110 120 130 140 150 0 50/60 Hz at No Load time (sec)

¾ Maintenance Check-List

NO ITEMS CONTENTS NOTES JUDGING STANDARD ACTION IN CASE _{OF ABNORMAL}

1. Check and record oil indicator 1. Winding and Oil

temperature indicator _{2. Record ambient temperature,} load (MW, MVAR)

Reading in proper range considering load and

ambient temperature Watching

temperature variation

2. Oil level indicator Check oil level gauges.

Difference within 10° between oil level indicator reading and temperature indicator reading

Watching oil level variation

3. Noise Check for abnormal sounds Without abnormal sound

compared with other units Stop operation 1. Check for loose connections

such as those found in main circuits, grounding circuits, auxiliary circuits and others. 4. Loose connections

2. Check valves for looseness

Without loosening of nuts

56

¾ Maintenance Check-List (Cont’d)

NO ITEMS CONTENTS NOTES JUDGING STANDARD ACTION IN CASE _{OF ABNORMAL}

5. Oil leakage

Check for oil leaks in connections such as those of valves, meter especially in gaskets joints and welded parts

Without oil leakage Refastening 1. Check for leaks Without oil leakage Stop & repair 2. Check for abnormal rotating

sounds and vibration Without abnormal sound compared with other units Stop & repair 6. Cooling equipment

can not operate

3. Check valve status Shall be open 7. Bushing

Evaluate the extent of the porcelain contamination by

appropriate method Without much dust Cleaning

8. Instrument Check indicators and relays Without oil leakage Stopping and coating the anti-oil leak paste

¾ Maintenance Check-List (Cont’d)

NO ITEMS CONTENTS NOTES JUDGING STANDARD ACTION IN CASE _{OF ABNORMAL}

9. Hazardous Area Sealing Fitting Bar properly seal Find leakage, reseal

10. Paint Work

Check to see if paint is chipped or pitting

Check to see if rust is

showing Clean off rust and touch-up painting 11. Oil strength Take oil sample and test every 2

years Should not be less than 30kV/2.5 mm Filter oil, or add new oil, or change all oil 12. Other

58

¾Elimination of Leakage Leakage can occur in: • HV or LV bushings

• Transformer Instrumentation • Tank sealing gaskets

• Pipework device • Valves

¾ Leakage on HV and LV bushings Cause → Cracked insulator

→ Defective seal

Solution → Tightening

→ Replace the defective seal

Note: It is important for all seal and gasket replacement operations to be carried out in a dry palce

60

¾ Safety precautions:

• The tap-changer is to be operated off-load. Before operating ensure that the transformer is de-energized.

• Installation, erection, and commissioning of transformers may only be carried out by qualified, skilled personel and only in accordance with the instruction manual.

• When handling the transformer, use the lifting and jacking points shown on the general arrangement drawing for lifting the complete unit (see outline drawings).

• If possible the transformer should be placed at least 0.5 m from the walls, to avoid excessive and harmful temperature rises.