CONTENTS
iii
Foreword
Preface
Chapter 1- Design Parameters for Transmission Lines
1.1
Introduction
1.2
Mechanical Design
1.3
1.2.1
Wind Speed
1.2.2
Maximum Temperature of Current Carrying Conductor
1.2.3
Span
1.2.4
Tower Steel Sections
3
1.2.5
Stresses in Bolts
3
1.2.6
Ground Clearance
3
1.2.7
Quality of Zinc
4
1.2.8
Weight of Zinc Coating
4
1.2.9
Minimum Zinc Coating
4
1.2.10
Sag Template
4
Electncal Design
5
1.3.1
Electrical Clearances
5
1.3.2
Air Clearances
5
1.3.3
Minimum Ground Clearance
5
1.3.4
Minimum Clearance above Rivers/Lakes
6
1.3.5
Air Clearance and Swing Angles
6
1.3.6
Clearance between Conductor & Groundwire "At Tower"
7
1.3.7
Clearances at Power Line Crossings
8
1.3.8.1 Power Lines Crossing each other
8
1.3.8.2 Power Lines Crossing Communication Lines
8
Power Line Crossing Railway Tracks
9
1.3.10 Power Lines running along or across the Roads
9
1.3.9
1.3.11
Clearances to Ground and Buildings as per IE Rules 1956
(latest edition)
9
1.3.12
Insulators / Insulation
10
1.3.13
Right of Way Requirement
11
1.3.14
PTCC
12
x
1.4
Conductor
12
1.5
Earth Wire
14
Annexure A
Typical sag template drawing-Dog ACSR conductor
16
Typical sag template drawing-Panther ACSR conductor
17
Typical sag template drawing-Zebra ACSR conductor
18
Typical sag template drawing-Moose ACSR conductor
19
Chapter 2- Inspection and Maintenance Formats of Transmission Lines
2.1
Introduction
20
Inspection from Ground
20
2.3
Inspection after Climbing the Tower
20
2.4
Schedule of Inspection and Maintenance Activities
21
2.5
Fault Inspection of Line
21
2.6
Inspection / Check Report for Major Maintenance Work
21
Fomlat-I
- Ground Patrolling Report
22
FOn11at-II
- Tower Climbing Patrolling Report for Critical Lines/ Critical
Stretches (Non Outage)
23
FOn11at-Ill
- Live Line Puncture Insulator Detection
24
Fonnat-IV
- Maintenance Schedules of Transmission Lines
25
Fonnat-V
- Line Declared Faulty Inspection Report
27
FOn11at-VI
- Inspection Report for Major Maintenance/ Breakdown Works
28
Fomlat-VIl
- IR Value and other Details ofInsulators Under Shutdown
29
Fonnat-VIII
- Measurement of Contact Resistance of Joints
(After Replacement of Conductor/ Joints)
30
Chapter 3 - Probable Causes of Failure of the Transmission Line Components
3.1
Introduction
31
3.2
Probable Causes of Damage of Insulators and Hardware Fittings
31
3.3
Probable Causes of Failure of Conductor and Conductor Accessories
33
3.4
Adverse Affects of Vibration
34
3.5
Probable Causes for Damage of Earthwire and its Accessories
34
3.6
Probahle Causes for Failure of Towers
35
3.7
Probable Causes for Rusting
37
3.8
Probable Cause of Failure of Tower Foundation
37
Xl
3.9
Causes of Erosion at the Base of Foundation / Tmver Legs
38
3.1 0
Probable Causes of Damage of Earthing Electrode and Earthing Strip, etc.
38
Effect of Vibrations on Perfomlance of Components of
Transmission Line
39
Annexure 1
Chapter 4 - Condition Monitoring of EHV Transmission Lines
4.1
Introduction
40
4.2
Philosophy of Condition Monitoring
4.2.2
Advantages
40
40
4.3
Condition Monitoring of Transmission Line
41
4.3.2.1
Corrosion Measurement of steel (stub / anchor bolts) in
foundation Resistance Measurements Method
41
4.3.2.2
Tower Footing Resistance Measurement
41
4.3.2.3
Conductor Corrosion Detection
42
4.3.2.4
Conact Resistance Measurement of Conductor Joints
43
4.3.2.5
Checking of Clearances of Conductor
43
4.3.2.6
Condition Monitoring of Insulator
44
4.3.2.7
Coronography of Transmission Line
48
4.3.2.8
Line Signature Analyzer (LSA) Unit
49
4.3.2.9
Thermovision Scanning of the Lllle
50
4.3.2.10
Monitoring of Spacers/Spacer Dampers/Hardware Fittings
50
4.3.2.11
Advanced Condition MOl1ltoring Teclmiques
51
Chapter 5 - Maintenance Procedures of EHV Transmission Lines
5.1
Introduction
53
5.2
Methodology
53
5.2.1
Locating the Fault
53
5.2.2
Patrolling and Scheduling
54
5.3
General Safety Precautions
54
5.3.1
Purpose
54
5.3.2
Scope
55
5.3.3
Definitions
55
5.3.4
Dangers
55
5.3.5
General Precautions to be taken before Climbing or Working on
Transmission Towers or working on Conductors
56
xii
5.4
Attending to Tower Collapse
5.5
Attending 10 Stuh
R~pair
58
5.5.1
PI\)('cdnre
58
5.5.2
T,~,;)i:,
required for Rectification of Stubs
62
5.5.3
;"/!:nerial required for R"'c:tJtlcatioll of Chimney
63
5.5.4
'lower Material Generallv re4uired for Rectification of Stubs
5.5.5
Additional Detail,:
5.5.4.1
5.6
57
STlTB:.:
~els
63
Insulator R cplacemc111
63
5.6.1
Bundle Conductor (Twin / Quad) Transmission Line
63
5.6.2
Bundle Conductor crwm) TransmiSSIOn Line
68
5.6.2. Replacement of Suspension Insulator (1- String)
68
Replacement of Tension Insulator - Procedure 1 (Fig. 9)
220 KY Tension Insulator Disc Replacement
74
78
66 KV & 132 KV Tension Insulator Disc Replacement
78
5.6.3
5,6.4
5.6.5
5.7
Catching Off / HoIoll1g Twin/Quad Conductors at Suspension Tower
81
5.8
Raising and Lowering Twin/Quad Conductor and Insulators
to the Ground
85
5.9
Repairing ofT\vin Conductor at Ground of400 KV Line. - Tension Tower 87
5.10
Procedure for repall'lng of Conductor at Ground of 400 KV Line.
- Suspension TowCT
89
5.11
Jointing Procedure
90
5.12
Repair of Twin/Quad Conductor ill situ with Mid Span
Compression Joint
93
situ with Repair Sleeve
94
5.13
Repair of TwiniQuad Conductor
5.14
Temporary repair of Twin/Quad Conductor in situ with Mid Span /
Dead End Compression Joints
95
5.15
Repair of Failed Jumpers
95
5.16
Repair of Failed Earth Wire
96
5.17
Replacement of Nuts and Bolts
103
5.18
Replacement IRepair of Spacer ISpacer Dampers
103
5.] 9
Anti-Corrosive Measures
106
5.20
Preventive Maintenance of Tower Foundation
107
5.21
Earthing Maintenance of Transmission Lines
107
ill
l(lll
5.22
Tree Cutting/fnJ1ll11ing
108
Chapter 6 - Hot Line Main!enance
6.1
Introduction
110
6.2
History ~Jl1d Ik,dopment of Hot Line Maintenance Tools
110
6.3
Trainin.c!
111
6.4
Methods oj' riot Line Maintenance
111
6.5
Hot Line ()perations
112
6.6
Safety
112
6.7
6.6.1
Safety Rules
112
6.6.2
Safe Electncal Clearance
113
6.6.3
Effect of Leakage Current flow in Body
113
Ropes and Hot Line Knots
113
6.7.1
Types of Ropes
113
6.7.2
Care of Ropes
115
6.7.3
Knots
115
6.8
Safe Practices for Live Line Barehand Mallltenance
115
6.9
Hot Stick Method
6.9.1
Design Considerations
116
6.10
116
6.9.2
Advantages of Epoxy Glass Stick
116
6.9.3
Type of Epoxy Tools and its Loading Capacities
117
6.9.4
Metallic Tools
117
6.9.5
Care of Tools
118
6.9.6
Maintenance of Tools
118
6.9.7
Replacing Femlies on Epoxiglass Poles
119
6.9.8
Protecting Tools during Transportation
120
6.9.9
Inspection of Tools
120
6.9.10
Repainng Broken Metal Members
120
6.9.11
Using LImitations
120
6.9.12
Caution
120
Live Line Barehand Maintenance
121
6.10.1
Principle of Live Line Barehand Work
121
6.10.2
History of Live Line Barehand Work
121
XIV
6.10.3
Equipment
122
6.11
Bondmg procedure
123
6.12
Important Tools
124
6.13
Procedure
6.13.1 Preliminary Works to be taken up before Starting the
Hot Line Work
126
6.13.2 Terminology used in the Procedure for Hot Line Maintenance
126
6.14
Hot Line Tools
127
6.15
Procedure for Hot Line Maintenance Work upto 220 KV) - Hot Stick
Method
6.15.1 Suspension Insulator String
127
127
6.15.2 Tensiop Insulator String
128
6.15.3
129
Precautions
126
Procedure for the Hot Line Maintenance work in 220 KV Double
Circuit Suspension Tower (Middle Phase) using Trolley pole by
Hot Stick Method
129
6.17
Procedure for Hot Line Maintenance work (66KV/132KV)
133
6.18
Procedure for Hot Line Maintenance Work - Bare Hand Technique
134
6.16
6.18.1
400 KV Single Circuit Suspension Tower (Middle Phase)
134
6.18.2 400 KV Single Circuit Tension Tower (Middle Phase) Using
the Method of Controlling of Ladder from Ground
141
6.18.3 400 KV Single circuit Suspension Tower (Outer phase) using
Trolley Pole method
150
6.19
Procedure For Hot Line Maintenance Work in 400 KV Single Circuit
Suspension Tower (Middle Phase) using Trolley Pole Method
159
6.20
Tightening of nut bolts/ Replacement of spares/ jumper
6.21
Replacement of Spacers/Tightening of Nut BoltslReplacing Jumper in
165
Substation - Line up to 400 KV
164
Annexure A - Typical List of Hotline Tools Required for Maintenance of Line
Upto 220 KV by Hotstick Method
167
Annexure B - Typical List of Hotline Tools Required for Maintenance of 400
KV line
169
Chapter 7 -
7.1
Insulator Washing/Cleaning
Introduction
172
xv
7.2
Type of Contaminants
172
7.3
Pollution Management/Methods of Cleaning
173
7.3.1
Pollution Management
173
7.3.2
Methods of Insulator Pollution Cleaning
174
7.3.2.1.2
Washing with Medium Pressure Water
185
7.3.2.1.3
Washing with low Pressure Water
185
7.3.2.1.4
Compressed Air - Dry Cleaning
186
7.3.2.1.5
Hot Wiping (Hot Cleaning)
188
7.3.2.2
Cleaning under De-Energized Conditions
189
7.3.2.2.1 Hand Cleaning
189
Cleaning of Polymer Insulators
189
7.3.2.3
7.4
7.5
7.6
7.7
7.8
Safety Procedures
189
7.4.1
Technical Considerations for Energized Cleaning with Water
189
7.4.2
Resistivity Measurement and Monitoring
191
7.4.3
Water Pressure
191
7.4.4.
Nozzle Orifice
191
7.4.5
Safety
192
Frequency and Results of Cleaning
192
7.5.1
Frequency
192
7.5.2
Results
192
General Guidelines
193
7.6.2
Training
194
7.6.3
Equipment
194
7.6.4
Public
194
7.6.5
Limitations
195
Practical Experience in Hot Line Washing in India
195
7.7.1
Insulator Washing Methods by other Utility
195
(A)
Live Line Washing
195
(B)
Cold Line Washing
199
Other Pollution Cleaning Methods
7.8.1
Cleaning of Coated (Greased) Insulator
200
200
XVI
7.8.2
Silicone Protective Coatings 200
7.8.3
Silicone RTV Coatings 201
Chapter 8 - Emergency Restoration of Damaged Transmission Lines
8.1
Introduction
203
8.2
Advantages of ERS
203
8.3
Components ofERS
204
8.4
Deployment of ERS System
205
8.4.1
Route Alignment
205
8.4.2
Computerized Calculations
205
8.4.3
Erecting Structure
206
8.4.3.1 Gin Pole Method
206
8.4.3.2 By Light Duty Crane
206
8.4.3.3 Winch Line Method
206
8.4.3.4 Helicopter Method
206
Anchoring System
207
8.4.4.1
Cross Plate Anchor
207
8.4.4.2
Screw/Marsh Anchor
207
8.4.4.3
Dead Weight Anchor
207
8.4.4
8.5
8.4.5
Stringing and clipping of conductor
207
8.4.6
General Precautions
207
8.4.7
Safety Aspects
207
Training
About the Authors
208
209