Lightning Arrester

TECHNICAL SPECIFICATION
TECHNICAL SPECIFICATION FOR LIGHTNING ARRESTORS
1. SCOPE :
1.1. This Specification covers design, manufacture, testing at manufacturer’s Works, packing,
supply, delivery of 42 KV & 12 KV classes of gapless Lightning Arrestors complete with fittings
and accessories.
1.2. These arrestors shall be of Heavy Duty, Station Class / Distribution Class and Gapless Zinc
Oxide type.
1.3. Arrestors shall be hermetically sealed units suitable for outdoor installation on self-supporting
base or structures.
2. STANDARD :
Arrestors shall conform in general to IEC-99-4 document or its latest amendment and IS/IEC
as follows:
i) IEC-99-4 : Gapless Lightning Arrestor
ii) IS 3070 P-III : Metal Oxide Surge Arrestors without gaps for AC Systems.
iii) IEC 99 P-III : Artificial Pollution Testing of Lightning Arrestor
iv) IEC 270 : Partial Discharge Measurement.
v) IS 2071 : Methods of H V Testing
vi) IS 6209 : Methods for Partial Discharge Measurement
vii) IS 5621 : Hollow Insulators for use in electrical equipment
3. DEVIATION :
Normally the offer should be as per Technical Specification without any deviation. But any
deviation felt necessary to improve performance, efficiency and utility of equipment must be
mentioned in the ‘Deviation Schedule’ with reasons duly supported by documentary evidences
and advantages of such deviation. Such deviations suggested may or may not be accepted.
But deviations not mentioned in Deviation Schedule will not be considered.
4. DUTY REQUIREMENT :
The Surge Arrestors are being provided to protect the following equipment whose insulation
levels are indicated in the table given below:
Equipment to be protected L I for 42 KV
system (KVp)
L I for 12 KV
system KVp)
Power Transformer
+/-170 +/-75
Instrument Transformer +/-170 +/-75
CB/Isolator Phase to ground
+/-170 +/-75
Across open poles +/-195 –
4.1. The Lightning Arrestors shall be capable of discharging Lightning and switching surges and
temporary power frequency over voltages .The Surge Arrestor shall be capable of discharging
over voltages occurring during switching of unloaded transformers and long lines.
4.2. The Arrestors shall be capable of withstanding Maximum Continuous Operating Voltages
(M.C.O.V).
4.3. The Arrestors supplied shall be suitable for heavily polluted atmosphere.
4.4. The reference current of the Arrestors shall be high enough to eliminate the influence of
grading and stray capacitance on the measured reference voltages.
5. FITTINGS & ACCESSORIES :
5.1 Arrestor rating upto 42 KV shall be directly mounted on structure as there is no surge
counter.
5.2 Each single pole arrestor shall be provided with suitable name plate, at the base with the
following data :
i) Name of device
ii) Manufacturer’s name and trade mark, type and identification
iii) Year of manufacture
iv) Voltage rating & frequency rating.
v) Nominal discharge current
vi) MCOV (Maximum Continuous Operating Voltage in KV).
vii) Discharge class.
viii) Energy Discharge capability (KJ/KV rating)
ix) Purchase Order reference.
x) Applicable Standard.
xi) Pressure Relief rated current in KA rms (for arrestors fitted with Pressure Relief device)
xii) Serial Number
5.3 Clamp type terminal connector shall be suitable for either ACSR DOG Conductor for 42 KV and
WEASEL / RABBIT Conductor for 12 KV system voltage class L.A. having horizontal/
vertical take off. Detailed particulars have been indicated in the specification for
Clamps and Connector in this bid document.
5.4 Two ground terminal connectors suitable for G.I strip of required size shall be provided on
diagonally opposite sides.
5.5 Necessary hardware such as nuts, bolts, spring washers, etc. shall be supplied for different
units.
5.9 12 KV Lightning Arrestor should be of Distribution Type and should have suitable Fault
Indicator.
6 CONSTRUCTIONAL FEATURES :
6.1 The arrestor elements shall be designed in such a way as to obtain robust construction with
excellent mechanical and electrical properties even after repeated operation. The lightning
arrestors should be adequately designed to operate satisfactorily under temporary power
frequency over voltage as given in Specific Technical Parameters, after discharging two shots
of respective long duration surges. Uniform density of zinc oxide element shall be maintained
to provide uniform current distribution.
6.2 The lightning Arrestors shall be of adequate Pressure Relief Class as per IEC-99-4 , fitted with
Pressure Relief Devices and Arc diverting ports to minimise possibilities of shattering of
porcelain housing.
6.3 Sufficient creepage distance shall be provided to reduce excessive uneven voltages over the
porcelain due to contamination, for which the arrestor shall not fail.
6.4 Seals shall be provided in such a way that these are always effectively maintained even when