IFEA 25Jan12 SusaD RUN TEST The heat run test, i.e. temperature rise test, is the type test carried...

SINTEF Energy Research

Dejan Susa on behalf of SINTEF Electric Power Technology Department

[email protected]

1

POWER TRANSFORMERS


Transformer design • Insulation– Liquid, Air

– Solid

• Stresses– Thermal

– Dielectric

– Mechanical

2

Electrical Breakdown


Insulation Degradation: Remaining lifetime

3

TRE

ENDNOWA

eADPDP

emainingLifRe

11

SINTEF Energy Research 4

Transformer Life Parameters

H2O

DGA

Top-Oil Temp.Load Current

Hot-Spot Temp.

Bottom-Oil Temp.

Ambient Temp.


Characteristic Temperatures

Cool

er

Core

LV w

indi

ng

HV

win

ding

H x gr

gr

Bottom Oil-Winding

Ambient

Top Oil-Winding

Average Winding

Top Oil Tank

Average Oil

Temperature rise

Rela

tive

Pos

ition

Hot-Spot


Temperature limits are based on expected lifetime

6

IEC 60076-2: Temperature rises

Requirements forTemperature rise limits

K

Top liquid 60Average winding (by winding resistance variation):

65

70

– ON.. and OF.. cooling methods – OD.. cooling method

Hot-spot winding 78

Ambient temperatures

°C

Correction of temperature

rise

K *yearly average

monthly average

maximum

20 30 40 025 35 45 –530 40 50 –1035 45 55 –15

* Referred to the values given in Table 1.


HEAT RUN TEST The heat run test, i.e. temperature rise test, is the type test carried out to verify the

guaranteed temperature rises for oil and windings

It is also used to reveal the possible overheated locations inside and outside windings due to high stray fields for the high powers

In addition, as indicated above, the temperature rises obtained during a heat-run test are used for estimating transformer loading capability by application of the relevant thermal models

During a heat run test the following temperatures could be directly measured: Ambient temperature Top-oil temperature Bottom-oil temperature Hot-spot temperature, hottest winding temperature (if fiber optic sensors are installed)

There are two methods used for performing the heat run test: short circuit back-to-back

7


Hot-Spot Temperature Direct Measurements


Transient state: Hot-spot and Top-oil Temperatures

9

Hot-spot to top-oil gradient

Top-oil rise over ambient

Ambient Temperature

= H • gr ·Ky • fhs-oil(t)

=(Top-oil rise)r •[(1+R·K2)/(1+R)]x • foil(t)

Ambient Temperature

Top-

oil t

emp.

Hot

-spo

t te

mpe

ratu

re

f1(t)

oil TIME TIME

f2(t)

k21

foil(t)=f1(t)=(1-e-t/(k11·o,r)) fhs-oil(t)=f2(t)=k21[1-e-t/(k22w,r)]-(k21-1) [1-e-t/(o/k22)]

SINTEF Energy Research10

Recommended thermal characteristics for exponential equations


0

10

20

30

40

50

60

70

80

90

100

0 100 200 300Time, min

Tem

pera

ture

, deg

C

Hot-Spot Temperature:400 MVA ONAF UNIT/120 kV WDG

IEC 76-7: New and Active Guide Measured

IEC 354: OLD GUIDE


IEC 60076-7 versus IEC 354

1. Oil pocket

2. CT

3. Heating element

4. Matching Resistance

1

2

3

4TIME

-IEC 76-7

oil

oil

oil,ss

1

TIME

3,4

TIME

-IEC 354


Oil Viscosity Effect on Power Transformer Thermal Performance: New Oils

TIME

-IEC 76-7


Transformer Oils:Mineral Oil- Natural Ester – Synthetic Ester

• Viscosity-temperaturerelationship is not strictlyArrhenius type


Transformer Oils

15

Ester


Accelerated Ageing Testing

lnk

1/T

tDPDP

k STARTEND

11

t

DP

0 t

Ageing rate of paper:

TREA

eAk

TRE

ENDNOWA

eADPDP

emainingLifRe

11


A and E Parameters


Moisture in Paper• Equilibrium Charts


Pictures – Paper Sampler Rig


Paper Sampler Rig - schematic


Characteristic Ageing Parameters


Application

Load History Temperature

A:Contamination Moisture, LMA

Age EA:Process Material

New Now End

Year 2011 ?

1000 ? 200DP scale

Age scale

Condition scale

Load Forecast Temperature

A:Contamination Forecast Moisture, LMA

EA:Process Forecast Material

TRE

ENDNOWA

eADPDPemainingLifRe

1111

START

TRE

NOW DPteADP

A


Example:Eidsiva Anlegg AS; Gjøvik T1

• Top-Oil Temperature=40 degC• Moisture in Paper=1.5% (Equilibrium Curves)• Production Year: 1986• DPSTART=1000• DPEND=200

TRE

ENDNOWA

eADPDP

emainingLifRe

11

11

START

TRE

NOW DPteADP

A


Example: Loss of Life (IEC 60076-7) Relative Aging Rate due to Hot-Spot Temperature (V):

Non-thermally Upgraded Paper

Thermally Upgraded Paper

The relative ageing rate V = 1,0 corresponds to a temperature of 98 °C for non-thermallyupgraded paper and to 110 °C for thermally upgraded paper:

6/)98(2 hV

)273

15000273110

15000(

heV

Loss-of-Life (L)

Over certain period: L=ΣVnxtn, where n(1,N)


Loss of Life Example

Load Steps of the Transformer

0,00

0,50

1,00

1,50

2,00

2,50

0 4 8 12 16 20 24

Time (hours)

Load

Fac

tor

Hot Spot Temperature Calculation

0

50

100

150

200

250

0 4 8 12 16 20 24

Time (hours)

Hot

Spo

t Tem

p (D

eg C

)

Loss of Life Calculation

0102030405060708090

100

0 4 8 12 16 20 24

Time (hours)

Loss

of L

ife (d

ays)

Dry and Clean IEC 76-7

Load Profile Hot-Spot Temperature Profile

Time, hoursTime, hours

Time, hours

Load

fact

or, K

Loss

of l

ife,

day

s

Tem

pera

ture

, deg

C


Monitoring Gasses

• DGA

Limited gas range monitor

Complete gas range monitor

•Hydrogen, H2•Methane, CH4•Ethane, C2H6•Ethylene*, C2H4•Acetylene*, C2H2 •Carbon Monoxide, CO•Carbon Dioxide, CO2•Oxygen, O2•Nitrogen, N2

•Hydrogen, H2 (100%)•Ethylene, C2H4 (8 %)•Acetylene, C2H2 (1.5)•Carbon Monoxide, CO(18%)


Typical gasses generated:

27

IN CASE OF TRACKING DISCHARGE IN WET INSULATION

IN CASE OF CORE CIRCULATION CURRENTS

Low energy electrical discharge: Hydrogen H2, Methane CH4

Circulation currents in the core: Ethylene C2H4, Methane CH4 and Hydrogen H2


Typical gasses generated:

28

IN CASE OF OVERHEATED CONNECTION

IN CASE OF WINDING OVERHEATING

Local hot-spots: CO and Ethylene C2H4, Methane CH¤

Thermal degradation of insulating paper: CO

IFEA 25Jan12 SusaD RUN TEST The heat run test, i.e. temperature rise test, is the type test carried...

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Transcript of IFEA 25Jan12 SusaD RUN TEST The heat run test, i.e. temperature rise test, is the type test carried...