Increasing Transformer Reliability by SMART Bushing

OVERVIEW TECHNOLOGIES

Types RBP OIP RIP RIS RIF

Insulation Srbp Paper+Oil Paper+Epoxy Synth+Epoxy Glass+Epoxy

Tan δ 0.7 0.4 0.4 0.35 0.3

Pressure Nil Yes Nil Nil Nil

Life 25 40 40 50 50

Population 8 % 80 % 10 % 1 1

PD high <10pC <10pC <10pC <10pC

50 % of failure-

>fire

FAILURE ANALYSIS…EUROPE

45%

7%

1%

17%

3%

26%

1%

Windings

Lead exit

Insulation

Bushing

Core

Tapchanger

Others

50% >400kV

RD2

Slide 3

RD2 Ramachandran Damodaran, 05-08-2016

ROOT CAUSE ANALYSIS

� 80% leakage (OIP Bushings )

� 13% deterioration of insulation

� 7% mechanical damage (mainly

porcelain insulators)

WEAK LINKS

Water accumu

late

High RPN

Summary of IMPROVEMENTSBY PROBLEM SOLVING + FMEA

� LOWEST RPN ON SEALING- ALL JOINTS – UNDEROIL

� LOWEST RPN ON CONDUCTOR- CASTINGS – WELDING

� RISK REDUCED AT TOP CONNECTION- 3 NOS TAPPED HOLES

� HEAT SINK FOR HOTSPOT- SOILD TOP TERMINAL

� CURRENT SHARE EQUALLY- PLANETARY + SINGLE PIECE

�ELCTROPLATING DEFECTS- ELECTROLESS

We understand and We care

SOME CASE STUDIES

NO WELDING –better conductance

INTEGRAL terminal –thermal performance

ElectrolessNickel

SOME CASE STUDIES

JOINTS ABV OIL LVL

SOME CASE STUDIES

JOINTS ABV OIL LVL

AGEING of BUSHING

� High ambient temperatures & temperature changes

� High & frequent load cycles (e.g. pump storage power plants)

� Overvoltage/transients (switching, lightning, harmonics)

� Leakage à moisture ingress

� Oil leakage (OIP only) à loss of insulation/dielectric properties

� Corrosive contaminants in oil (for OIP only)

� Capillary cracks (RBP types)

� Partial discharges

SMART PLANS

Step 1: Identify & Clustering Bushing Fleet

• Voltage level

• Current level

• Technology

• Age

• Type of transformer

• Importance of substation

SMART PLANS

� Step 2: Risk Assessment of Installed Bushing Fleet

• Based on Age

• Site Measurements

- Tandelta + Capacitance

- thermography

- Dissolved Gas Analysis-oil sampling

- Partial Discharge limited by background noice

< 1% OK1`2%..??>2%..ICU

� Step 3: Definition of Bushing Style to Replace Installed Fleet

� Step 4: Set Up Risk-Based Replacement Schedule

� Step 5: Execution of Bushing Fleet Replacement Strategy

THANK YOU

OIL + PAPER INSULATION

� Oil Impregnated Paper (OIP)

� Century Old Proven need Long Process time

� Need Monitoring of oil level + Quality

� Moisture settles down at most stressed part

� Failure may lead to a devastating fire

RIP IS POPULARMANY

APPLICATIONS

RESIN + PAPERRESIN + PAPERRESIN + PAPERRESIN + PAPER

� Dry type Resin Impregnated Paper (RIP)

� A big relief against the nuance of oil

� But RESIN do not marry PAPER well

� Long Process time to remove water from paper

� SLOW Impregnation of RESIN to Paper

� PAPER absorb moisture STORAGE in store

� RIP is BETTER than OIP but not the BEST

being fully dry and pressure-free;

• featuring a higher temperature class;

• being partial-discharge free;

• having low dielectric losses;

• being fire resistant, and;

• having outstanding mechanical properties

SEARCH FOR Alternative to RIP…..

ABBMICAFIL

RESIN INFUSED GLASS

� Most proven FRP system Resin Infused Glass widely

accepted from Boat to Aircraft

� Superb Electrical and Mechanical properties

� Popular for Polymer INSULATORS, Wind Mill etc..

� Factory tested values retain life Long

P.Keith Ellis ..IEEE ex.chairman…

“….seen many failures of RIP leading fire…if you need a safer bushing for transformer…look in to fiberglass impregnated Glass.

RESIN +GLASS

� Safer, no risk of fire and explosion.

� Totally maintenance-free, low cost of ownership.

� Superior resistance to mechanical and thermal stresses.

� Environmentally friendly – no risk of toxic leakage.

� Sealed and impervious to water and pollution.

� Real time tracking for unmatched peace of mind.

MGCPCORE

TRENCH

BETTER with POLYMER HOUSING

TRANSFORMER BUSHINGSTRANSFORMER BUSHINGSTRANSFORMER BUSHINGSTRANSFORMER BUSHINGS

No Grading

with Grading