transformer oil กับการทำ cbm by k prawit

Transformer Oil CBM

Agenda

1

2

3

4

Insulation system of transformer

Condition Based Monitoring

Conclusions

Introduction

Introduction

Transformer Core Insulation Winding

Insulation system of transformer

Paper and Pressboard

- Made from cellulose fiber

- Pine tree produces long fibers with high mechanical strength

- Typical water content in shop 5 % , after drying < 0.5 % , final product < 1 %

- Must be free from contaminants

Oil

- Insulating material

- Heat transferring media

Major failure in transformer

Core

Overheating breakdown in core plate insulation leads to circulating currents

Core bolt and Core clamping structure Breakdown of insulation between parts of clamping structure results in circulating current

Windings and inter-winding insulation Overheating due to poor joints is a common fault in any part of the electrical circuit.

Breakdown of inter-strand insulation results in circulating current causing overheating of

insulation and hot spots at point of fault.

Tank, flux shields, and fittings The breakdown of insulation between portions of the tank shields or between the shields

and tank can lead to circulating current, this will be a function of load current.

The type of faults

The Type of Faults

Thermal Faults Electrical Faults


Transformer Healthy

Electrical Test Transformer Oil Test

- On line real time

- Time Based

- Off line test (Time Based)

- On line test (PD)


Transformer Healthy

Blood Test Transformer Oil Test

- Dissolved Gas

Analysis

- Moisture Content

- Furans Analysis - etc..

- Cholesterol

- Triglyceride

- Glucose - etc..

Mineral insulating oils in

electrical equipment Supervision and

maintenance guidance

IEC 60422

Power Transformer

Maintenance and

Application Guide

(EPRI)

Optimum Sampling

The optimum sampling frequency

depends on :

Function Voltage

Power Service conditions

Reliability requirements

Economic factors

Risk Based Inspection

(RBI)

Optimum Sampling

Equipment Number Failure Mode Damage Mechanism Probability

Consequence Risk Maintenance &

Inspection Daily Inspection Time Interval Risk Mitigation

Safety Environment Cost Safety Environment Cost

1 Insulation Failure Oxidization of oil 3 A A E 3A 3A 3E Oil screen test - 6 month CBM /TBM

2 Insulation Failure Thermal

decomposition of

oil

3 A A E 3A 3A 3E Oil screen test - 6 month

CBM /TBM

3 Insulation Failure Contamination

from moisture 3 A A E 3A 3A 3E Oil screen test -

6 month

CBM /TBM

4 Insulation Failure

Solid insulation

failure /moisture

ingress /external

contamination

4 A A E 4A 4A 4E

Power factor of

bushing /

visual

inspection

visual

inspection

2- 3 years TBM

Power

Transformer 5

Earthing

malfunction

Earthing

disconnected with

the earth or

resistance too

large

2 A A D 2A 2A 2D Grounding test visual

inspection

One year TBM

6 Fail to transform

voltage Open winding 1 A A E

1A

1A

1E

Resistance

test -

2- 3 years

TBM

Continuous

Current

7 Failure of cooling

system

Pump Block,

wrong

direction,deteriorat

ion

2 A D D 2A 2D 2D Vibration test visual

inspection

2- 3 years

Prepare Spare

Part

8 Failure of cooling

system

External heat

radiation restriction 2 A A D 2A 2A 2D

External visual

inspection

visual inspection

One year

CBM

Risk Based Inspection (RBI)

Description ASTM Number

Dielectric Strength D-877/D-1816

Acidity D-974

Interfacial tension D-971

Color D-1500

Water Content D-1533

Density D-1298

Visual examination D-1524

Power factor D-924

Inhibitor content D-4768

Dissolved gas analysis D-3612 Furan analysis D-5837

Standard ASTM Tests for Insulating Oil

What is a Dissolved Gas Analysis(DGA)?

The detection of certain gases

generated in an oil-filled transformer

in service.

Parts per million = ppm.

Dissolved Gas Analysis

What is a Dissolved Gas Analysis(DGA)?

Combustible Gas Hydrogen Methane Carbon Monoxide Ethane Ethylene Acetylene Propylene Propane

Non Combustible Gas Oxygen

Nitrogen Carbon Dioxide

11 gas components analyze


How does the gases occur?

Manufacturing Process(Before in service)

O2 N2

H2

CO

2

CO



Normal Aging

CO CO2 H2

CH4 C2H6 C3H8

C2H4

Stable

Small

amount



Abnormal Condition


Evaluation of Possible Fault Type by the Key Gas


C2H4 Key Gas

Cause:

- Laminated core short turn

- Loose connection

- Defective cooling

Ethylene

Conclusions

CO Key Gas

Cause:

- Winding short turn

- Defective cooling

- Cellulose decomposition

Carbon Monoxide

Conclusions

Key Gas H2

Cause:

- High electrical stress

around sharp point

- Insulation deterioration

Hydrogen

Conclusions

Key Gas C2H2

Cause:

- Electrical arcing between

high voltage to ground

- Loose connection

Acetylene

Conclusions

Conclusions

Reduce unplanned outages &

equipment failures

Detect first sign of failure

condition

Provide prior warning of

impending failure

Transformer

Healthy

Extend transformer life and

save money

Benefits of

Transformer Oil CBM

transformer oil กับการทำ cbm by k prawit

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