Download Bushings Testing PDF

TitleBushings Testing
TagsElectricity Components Capacitor Insulator (Electricity) High Voltage
File Size3.1 MB
Total Pages25
Document Text Contents
Page 1

Introduction to

Doble Bushings Testing

Doble Engineering Diagnostics

Toolbox

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 2

• Capacitor/Condenser Type:

– Oil-Impregnated Paper Insulation

– Resin Bounded Paper Insulation

• Non-Condenser Type:

– Solid

– Alternate Layers of Solid and Liquid Insulation

– Gas-filled

Page 2

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 3

Main Insulation C1

CA = CB = CC = CD = CE = CF= CG = CH = CI = CJ

V1 = V2 = V3 = V4 = V5 = V6 = V7 = V8 = V9= V10 Tap

Electrode

CK Center
Conductor

Line-to-Ground System Voltage

Grounded

Layer/Flange

The Condenser type bushing allows an energized

conductor to penetrate a ground plane

Voltage is stressed equally across each layer of the

Condenser type bushing

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 4

Core Wind

C2 Plate

Foil

Tap Electrode

Grounded Layer/

Flange

CA

CB

CC

CD

CJ

C
E

N
T

E
R

C
O

N
D

U
C

T
O

R


CK

CE
CF

CG
CH

CI

Grounded

Layer/Flange

Page 12

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 23

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 24

Page 13

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 25

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 26

When to perform Bushings Hot-Collar Tests

• Compound-Filled Bushings

• Solid Porcelain Bushings

• Gas-Filled Bushings

• Oil Filled Bushings not equipped with taps and Overall Test cannot be
performed
– Single Hot-Collar Test on small Bushings 15 KV and below

– Several single Hot-Collar Tests for Bushings rated above 15 KV

• To check Oil level on all liquid filled Bushings without liquid level
gauges or sight glass

• To check Bushings with liquid level gauges whenever the gauge is
suspect

• As supplementary tests when Overall, C1, C2 Tests indicate possible
problem

Page 24

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 47

Type Description Typical PF Questionable PF

A* Through Porcelain 3.0% 5.0%

A** High Current 1.0% 2.0%

B* Flexible Cable, Compound Filled 5.0% 12.0%

D Oil Filled Upper Portion, Sealed 1.0% 2.0%

F Oil Filled, Sealed 0.7% 1.5%

L Oil Filled Upper Portion, Sealed 1.5% 3.0%

LC Oil Filled Upper Portion, Sealed 0.8% 2.0%

OF Oil Filled Expansion Chamber 0.8% 2.0%

S* Force C & CG, Rigid Core, 1.5% 6.0%

Compound Filled

* Type S, Form F, DF & EF (flexible cable) redesigned as Types B, BD, and BE,

respectively. Type S, no Form letter (through porcelain) redesigned as Type A

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 48

Typical Questionable

C1 C1

PF PF

Type ERC (Epoxy-Resin-Core, Plastic or Oil Filled) 0.8% 1.5%

Type PRC and PRC-A (Paper-Resin-Condenser Core) 0.8% 1.5%

Typical C2 power factors for older PRC design range from 4-15% due to injected

compound used

during manufacturing.

Page 25

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 49

Types Typical %PF Questionable %PF

Class LK-Type A, 23 to 69 kV 0.4 1.0

ODOF, Class G, and Class L Oil-Filled:

Prior to 1926 and 1.0-5.0 Change of 22%

after 1938 from initial

Between 1926 and 2.0-4.0 Change of 16%

1938 from initial

Type S, OS, and FS 0.8 2.0

On OCB and Inst. Trans. 69 kV and below 1.5 3.0

(except Types S, OS, and FS)

89 Years of Diagnostic Instrumentation and Services for the Electric Power Industry 50

Typical %PF Questionable %PF

On OCB and Inst. Trans. 92 kV to 139 kV 1.5 3.0

(except Types O, O-A1, OC and O Plus)

On Power and Dist Trans of all rating, 1.0 2.0

and OCB & Inst. Trans. 161 kV to 288 kV

(except Types O, O-A1, OC, and O Plus)

All Type D Transformer Bushings 1.5 3.0

( Semi-Condenser)

Type RJ

(Solid Porcelain) 1.0 2.0

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