MEDIUM VOLTAGE METAL OXIDIZED SURGE ARRESTER
It is used to limit the voltage rises in MV facilities at 36 kV and less level at transmission system. They are without gaps, variable metal-oxide-resistant, porcelain or silicone shell-phase to ground surge arresters. They are instituted as single phase units with all auxiliary equipment and materials.
Standards
Standards Subject
TS-EN ISO 9001: 2000 Quality Management System Certificate
IEC 60099-4 Surge arresters-Part 4: Metal-oxide surge arresters without gaps for a.c. systems
IEC 60099-5 Surge arresters-Part 5: Selection and application recommendations
IEC 60060-1 High voltage test techniques. Part 1: General definitions and test requirements
IEC 60060-2 High voltage test techniques. Part 2: Measuring systems
IEC 60270 High voltage test techniques - Partial discharge measurement
IEC 60815 Guide for the selection of insulators in respect of polluted conditions
TS 914 EN ISO 1461 Galvanization (with hot-dip method)
All chemical, physical and dielectric characteristics of the materials used in manufacturing of surge arresters are produced in accordance with ASTM (American Society for Testing and Materials) and DIN (Deutsches Institut for Normung) norms.
Working Conditions
-height : under 1000 m
-ambient temperature (*)
. maximum: +45°C
. minimum: -40°C
. average of 24 hours: under +35°C
- wind pressure : 70 kg/m² (on circular surface)
: 120 kg/m2 (on flat surface)
-maximum solar radiation: 1000 W/m2
-icing: class10, 10 mm,
-ambient air pollution : heavy
-earthquake
. horizontal acceleration : 0.5 g (ground level )
. vertical acceleration: 0.25 g
(*) For the facilities in places where are the ambient temperature can be out of the normal operating conditions at above, the preferred ranges of minimum and maximum which must be indicated as below:
-for very cold climates : -50°C ve +40°C
-for very hot climates : -5°C ve +50°
Technical Features
TYPES OF METAL OXIDE SURGE ARRESTER
Surge arresters are outdoor, variable metal-oxide-resistant, without gaps and porcelain or metal oxide silicon enclosed.
Electrical Properties
Surge arresters are in properties as below:
- Rated voltage:
Surge arrester rated voltage , Ur (kV-rms)
Maximum Direct Earthing Earthing on Resistor
System voltage (kV-rms) system system
7,2 6 7
12 10 12
17,5 15 18
6 30 36
-Rated frequency (**):50 Hz
-Rated discharge current (8/20 µsec) (kA-peak): 2.5 - 5 - 10 (line discharge class 1)
(Will be determined by the buyer)
-Pressure limiting current
(for surge arrester with porcelain enclosed)
.for 10 kA surge arrester : 20 kA-rms
.for 5 kA surge arrester : 16 kA-rms
-System earthing :Direct earthing / Earthing on Resistor
-Earthing failure factor : 1.4
- Time to clean the soil failure: maximum 3 sn
-Rated system voltage (kV-rms) : 6.3 10,5 15,8 33,6
- Lightning impulse withstand voltage of equipment will be protected (kV-peak): 60 75 95 170
(**)They are designed as surge arrestors to carry out their normal function without any failure in process that the network frequency is the range of 47.5-52 Hz continuously and for 20 sec in 47-47.5 Hz.
Constitutive Properties
All materials used in making of surge arrester were chosen most properly of purposes of use in terms of the properties of durability, strength and other physical, chemical and electrical.
Enclosure is porcelain or silicon rubber material as Material Listing and/or Guaranteed Property Listing.
Insulating enclosure is manufactured to withstand of short-circuit current, winding forces, earthquake and other vibrations and forces which occur cause of the atmospheric conditions in both normal operating conditions and conditions of over voltage occurred.
All metal parts exposed to the atmosphere on the insulating housing sections are made of hot-dip galvanized steel materials or corrosion-resistant materials. All metallic parts have been determined not to separate enclosure when the temperature changes and mechanical stresses, the materials used for determination are high quality and they do not make chemical reaction with metal parts. Also, they have not the feature of expansions break.
In listing of materials and/or guaranteed characteristics, otherwise specified, minimum surface leakage path length of the enclosure is at least 25 mm/kV.
Porcelain Enclosure
Its active parts and units of the surge arrester has been surrounded by a humidifier material, filled with dry air or nitrogen at atmospheric pressure and are placed into a closed porcelain housing sealed both ends with spoil elastic seals. Appropriate measures were taken to protect against the contamination and moisture for a long period of time. Porcelain containers; high-skilled and homogeneous structure, surface open to the atmosphere is smooth, flawsless, brown, covered with a bright glaze. They are tested and manufactured as foreign matter, cracks,skin, air bubbles, scratches, burrs, roughness, spots, stains and other defects that will not be in the containers.
Porcelain enclosures, which their rated discharge current is 5 kA and 10 kA, is equipped with an edit of pressure-limiting to prevent the explosion of enclosure cause of long term monitoring current or surface omission of inter of surge arrester.
Silicone-rubber Enclosure
Silicone-rubber enclosure is flame resistant, no spaces, hydrophopic (water repellent) and smudge and explosion-resistant.
Enclosure is passed over ageing test during the 5000 hours which difficult environmental conditions defined in IEC 60099-4.
