technical of LIGHTNING ARRESTERS
1. Ultimate Tensile Strength (UTS)
1. Refers to the mechanical breaking strength of the arrester under tension.
2. Depends on core material (typically Fiber Reinforced Plastic (FRP) rods for polymer type).
3. Typical UTS range:
I. 11–33 kV arresters: 15–45 kN
II. 66–132 kV arresters: 45–70 kN
III. 220–400 kV arresters: 70–120 kN or more
4. Tested under IEC 60099-4 / ANSI C62.11 standards.
2. Working Load / Safe Working Load (SWL)
1. Typically 30% to 40% of UTS to ensure long-term durability.
2. Example: A 60 kN arrester will have an SWL of ~20–25 kN.
3. Designed to withstand mechanical load from line tension, wind, and mounting stress.
3. Conductor Diameter Compatibility
1. Lightning arresters are connected via terminal clamps, compatible with a wide range of conductors.
2. Conductor clamp compatibility: 8 mm to 40 mm, suitable for ACSR, AAAC, and copper conductors.
3. Terminal options: flat, eye, lug, or NEMA pads.
4. Slip Strength:
1. Refers to the resistance of terminal clamps or fittings from loosening or shifting under mechanical or electrical stress.
2. Slip strength >90% of UTS; typically 25–60 kN depending on rating.
3. Terminal connections must not shift under thermal expansion or high current flow during surge events.
5. Temperature Withstanding Capacity:
1. Operating temperature: –40°C to +85°C
2. Short-term high-temperature tolerance: up to 250°C to 300°C during discharge events
3. Thermal stability essential for long-term MOV block performance and mechanical integrity.
6. Corrosion Resistance:
1. Polymer-housed arresters: Silicone rubber with hydrophobic and UV-resistant properties
2. Metal parts: Stainless steel or hot-dip galvanized steel for hardware and terminals
3. Rated for use in coastal, desert, and industrial polluted environments without degradation.
7. Impact & Fatigue Strength:
1. Polymer arresters can absorb mechanical impacts from wind, birds, and accidental knocks.
2. Excellent vibration and fatigue resistance, especially under conductor galloping and mechanical oscillations.
3. Withstand short-circuit impact loads >20–40 kA without structural failure.
8. Mechanical Endurance:
1. Service life: 30–40 years under normal operating conditions.
2. Tested for:
I. Vibration resistance
II. Thermal cycling
III. Leakage current aging
IV. Continuous environmental exposure
9. Design Safety Factors:
1. Mechanical safety factor: 2.5 to 3.0 on tensile and structural load
2. Electrical design includes:
I. High Energy Absorption Capability (10–20 kJ/kV MCOV)
II. Pressure Relief Channels
III. Internal arc fault containment for safe failure
Top 5 Quality Assurance
1. Electrical Type & Routine Testing (as per IEC 60099-4 / IS 3070 Part 3 / ANSI C62.11)
a. Includes:
I. Residual voltage test
II. Energy withstand test
III. Long-duration current impulse test
IV. Partial discharge and leakage current test
V. High-voltage withstand test
VI. Accelerated aging test for MOV blocks
2. Mechanical Testing & Validation
a. Tensile strength test on arrester body
b. Vibration fatigue and cantilever load test
c. Terminal torque and slip resistance tests
d. Internal arc test to ensure pressure relief during failure
3. Environmental & Pollution Testing
a. Salt fog, acid rain, and UV weathering resistance tests
b. Hydrophobicity retention and recovery test (for silicone housings)
c. Sealing test to ensure moisture ingress protection (IP67/IP68 standards)
4. Dimensional & Visual Inspection
a. All units visually inspected for:
I. Housing cracks, voids, improper sealing
II. Terminal integrity
III. Surface defects or rubber discontinuities
b. Dimensional tolerances verified for mounting centers and terminal interfaces
5. Documentation, Marking & Traceability
a. Supplied with:
I. Routine test reports
II. Type test certificates (CPRI/ERDA/NABL labs)
III. GTP (Guaranteed Technical Particulars)
IV. Compliance to ISO 9001, ISO 14001
b. Markings include:
I. Manufacturer’s name
II. Rating (kV/MCOV/kA)
III. Serial number and batch traceability