7/24/2019 CT Impulse

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Appendix 1 FTA for Impluse Fai lure Decision 1 = not cause2 = possible cause

3 =most possible cause

Event No. Evaluation Decision Countermeasure

(*) : Corrective action only

1

1

------------

------------

No Load Test Showing similar

result before and after impulse

failure

1 ------------3

Not sufficent Clearance

Defect Insulation

1Clearancse are sufficient as per

drawing & standard

Visual Inspection did not found

any defect2

Factors

Impulse

Failure Lead

Winding Defect Insulation (Interturn)

Area of non live part too small

(limited safety) (Big Bushing)4 2

if using Big Bushing, live

area space will be added

5

Did not consider the length of

CT wire and understanding of

live are inside transformer

3

1. Training & Path of CT

Cables will be provided bu

Design

2. Make new Procedure for

CT Installation

MaterialCT secondary wire

insulation7

CT secondary Wire Design

Manufacuring

Inspection 6

CT secondary insulation is

designed only 3kV impulserated, and must be located in

non live area. In this event, CT

secondary wire is accidentaly

located in live area which cause

impulse failure

1

During corrective action, CTsecondary insulation is

repaired and added, due to

its insulation was little bit

burned (*)

Secondary Wire too

long

Inspection not done

after installing the

CT Wire

No specific Inspection/Check

List for CT Wire3

Add Specific Inspection

Cheklist for CT wire after

connection to terminal Box