Vibration Aspects of TL Engg.- CPRI

8/9/2019 Vibration Aspects of TL Engg.- CPRI

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INTRODUCTION

j Total performance

Design Material Process Workmanship Quality &

Inspection

j Product Testing Evaluation Qualification

j Mechanical reliability as important as Electrical reliability

j Cost of line components constitute 30 45 %of overall project cost


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PERFORMANCE OF TRANSMISSION LINE SYSTEM

Expected life of Transmission Line 35 Years

ASSURANCE OF

QUALITY

RELIABILITY

SAFETY

MAINTAINABILITY

PREVENTION OF FAILURE

Premature failures (Internal flaws & External factors)PREDOMINANT FACTOR AFFECTS PERFORMANCE

Natural Wind


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WIND INDUCED CONDUCTOR MOTION

AEOLIAN VIBRATION

CONDUCTOR GALLOPPING

WAKE- INDUCED OSCILLATION

LIFE ESTIMATION

NATIONAL / INTERNATIONAL STANDARDS

IEEE RECOMMENDATION


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TYPES OF WIND INDUCED MOTION

AEOLIAN GALLOP WAKE- INDUCED

LINES AFFECTED ALL ALL LIMITED

FREQUENCY (Hz) 3 - 150 0.08 - 3 0.15 - 10

AMPLITUDE(Pk Pk)

0.01 - 1 7 - 18 4 - 18

WIND VELOCITY(m/s)

1 - 7STEADYBARE/UNIFORMICED

7 - 18STEADYASYMMETRICALICED

4 - 18STEADYBARE DRY

CAUSE-DEVELOPDAMAGE

CYCLIC BENDING3 mos 20 YEARS

HIGH DYNAMICLOADS1 - 48 HOURS

CONDUCTORCLASHACCELERATEDWEAR1 mo 8 YEARS

AFFECTEDCOMPONENTS

CONDUCTOR-SHIELD WIRESTRANDS

CONDUCTOR,HARDWARE,INSULATOR STRUCTURES

SUSPENSIONHARDWARESPACERS DAMPERSCONDUCTOR

STRANDS


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Aeolian Vibrationmoderate wind speed 0.8 to 7 m/sec

frequency lies between 5 to 60 Hz,

high frequency, low amplitude

Excessive bending strain nearsuspension OR spacer clamp can causefatigue failures of conductor strands

Cumulative effect of the conductorvibrations can damage the conductor


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Conductor Galloping

U sually occurs in strong windU nstable aerodynamic characteristicsof conductors caused due toasymmetrical ice depositVery low frequency 0.1 to 0.75 Hz,amplitude of the same order of theconductor sag, mode shapes of one,two or three loops per span

In general bundle conductors aremore prone to galloping under icingconditions than single conductors

M odes of oscillation


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W ake induced oscillation

U sually occurs moderate to strong windin the range of 7 to 18 m/sec

Aerodynamic instability of the leeward

sub conductor of the bundle as itmoves in the wake of the windwardones.

Frequency lies in the range of 0.7 to 2Hz, amplitude of 0.5 to 20 timesdiameter of conductor

The most common form of wakeinduced oscillation is sub-span mode ofoscillations.

M odes of oscillation


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CONDUCTORS

TYPE OF CONDUCTOR : ACSR, AAAC, ACSR/TW, AASC

TYPE TESTS AS PER STANDARDSTYPE TEST, SURFACE CONDITION TEST, ULTIMATE

BREAKING LOAD TEST, STRESS-STRAIN TEST, SELF

DAMPING TEST., ETC


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PP

LC

LI

FEHLD

C

S URF ACE CO NDITIO N UBL TESTS URF ACE CO NDITIO N UBL TEST


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FEASIBILITY STUDIES ON ACSS CONDUCTOR

HIGH TEMPERATURE & LOW SAG CONDUCTORS


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FEASIBILITY STUDIES ON ACSS CONDUCTOR


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Mechanical test on insulators

24 HOURS MECHANICAL TEST, BENDING TEST,

FATIGUE/ VIBRATION TEST ., ETC

INSULATOR

Porcelain, glass insulators , polymeric insulators


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TYPE OF INSULATOR STRINGS

1. Single suspension I & V string

2. Double suspension I & V string

3. Single/twin/triple/quad tension string

4. Single/twin/triple/quad suspension string

Electro mechanical strength of insulator disc

45 kN, 70 kN, 90 kN, 120 KN, 210 KN, 245 KN


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STRESSES IN INSULATORS

A. Static Stress due to tension

B. Bending stress due to Sag

C. Dynamic Stress due to Wind induced vibration

D. Ultimate dynamic limit stress

E. Static Ultimate stress limit

A + B + C D withstand Fatigue test

A + B + C u Not withstand


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QUAD TENSION STRING FOR 800 K V SYSTEM


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V STRING FOR 400 K V SYSTEM


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V-STRING INSULATOR

UNDER FATIGUE TEST

QUAD TENSION STRING

UNDER FATIGUE TEST


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ELECTRO MECHANICAL SHAKER SYSTEM


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FAILURE OF INSULATOR STRING FAILURE OF BALL PIN

FATIGUE/VIBRATION TEST ON INSULATOR STRING


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FATIGUE/VIBRATION TEST ON INSULATOR STRING

FAILURE OF CORONA RINGS


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POLYMERIC INSULATOR (132 kV)


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Self damping capacity of ACSR/AAAC conductors is too lowto dissipate effectively the wind induced vibration energy

Use of external devices to supplement the dissipation of energy to reduce the fatigue failure

The mechanical behavior of different type of dampers

to be evaluated

Effectiveness of vibration damper depends on location,conductor tension, diameter, frequency etc.

Energy imparted to the conductor by wind should bedissipated by the conductor and external damping device

Pw = Pc + Pd

Pw - power imparted into the conductor by windPc - Power dissipated by the conductor Pd - Power dissipated by the damper

VIBRATION DAMPERS


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TYPE OF DAMPERS: 2-R, 4-R, DOG BONE, BRETTLE, TORSIONAL

TESTS ON DAMPERS:

Clamp Slip Test, Clamp Bolt Torque Test, Mass Pull Off Test,

Damping Efficiency Test, Dynamic Characteristic Test,

Fatigue/Vibration Test ., Etc

VIBRATION DAMPER


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6 R - VIBRATION DAMPER


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FE

ET

C

A

MS ES LI

EP ET LC SPB EW (LE)

VD

DAMPER EFFICIENCY/ FAT-VIB TESTDAMPER EFFICIENCY/ FAT-VIB TEST


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DAMPER E FF ENCY EST O N 4R V B RATI O N DAMPER FO R ACSR M OO SE

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

FREQUENCY in

z

E F F I C I E N C Y

ACCEPTANCE CURVE 4R VIBRATION DAMPER

SPAN= 400 m. TENSION=25% OF UTS{FOR ACCEPTANCE CURVE ONLY}

DAMPER EFFICIENCY CUR V E


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EDS

FT

A

DYNAMIC CHARACTERISTIC TESTDYNAMIC CHARACTERISTIC TEST


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ROCTEST RECORDERS IN POSITION


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ROCTEST VIBRATION RECORDER


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SAFE LIMIT FOR VIBRATION DAMPER

Bending Amplitude = 230 dy

= Strain in micro inch/inch

d = Individual strand dia. in inch

y = BA in mills (Pk-Pk)

Safe limit - BA 10 mils (Pk-Pk) or

0.25 mm (Pk-Pk)

BS- 300 micro strain (Pk-Pk)

GI L T Trans ission line reference book- Wind induced conductor

otion I R esearch digest 742, USA 1979


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SPACER DAMPERS

PURPOSE :

- To maintain the separation of sub conductors used in bundle

conductor design.

- Reduce the level of aeolian vibration and sub conductor oscillation

- Sub conductor spacing 450 mm

TYPE OF SPACER DAMPER

-TWIN SPACER/SPACER DAMPERS

-QUAD SPACER/SPACER DAMPERS


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TEST CONDUCTED:

CLAMP SLIP TEST, MECHANICAL TEST, TENSILE AND

COMPRESSIVE TEST , LOG DECREMENT TEST, DYNAMIC

CHARACTERISTIC TEST, FATIGUE/ VIBRATION TEST ., ETC

SPACER / SPACER DAMPERS


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QU AD SPA CER DAMPER


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LOG DECREMENT TESTLOG DECREMENT TESTC

SP-DP

AC

OSC ES LI

EWLC

FE

LOG DECREMENT/ FAT-VIB TESTLOG DECREMENT/ FAT-VIB TEST

EFFECTIVENESS

OF DAMPING


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LOG DECREMENT CURVE


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LOG DECREMENT TESTLOG DECREMENT TEST

DYNAMIC CHARACTERISTIC T ESTDYNAMIC CHARACTERISTIC TEST

STIFFNESS

DAMPING FACTOR


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Corona control ring, yoke plate, arching horn,

tension clamps, suspension clamps etc

OTHER LINE HARDWARE


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NEW TESTS/ PRODUCTS

1000 KVA SUBSTATION UNIT - SAUDI ARABIA

HOT LINE TOOLS - ELECTRICITY COMPANIES

POLE BASED MODULAR WORK STATION

CABLE TRAY

COMPOSITE SILICON INSULATOR

INSULATION PIERCING CONNECTOR


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NEW FACILITIES

NEW WAKE SIMULATION LABORATORY

FOR CONDUCTING TESTS ON 800 KV HVDC

STRINGS AND HARDWARE


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Vibration Aspects of TL Engg.- CPRI

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