Porcelain Housing Arrester limit excessive transient voltages and safely discharge surge currents to earth

Porcelain Housing Arrester

Porcelain Housing Arrester, also known as a Porcelain Surge Arrester or Porcelain Metal Oxide Surge Arrester (MOA), is a protective device used in electrical power systems to protect transformers, switchgear, transmission lines, and other high-voltage equipment from lightning surges and switching overvoltages.

It uses zinc oxide (ZnO) metal oxide varistor (MOV) elements inside a porcelain insulating housing to limit excessive transient voltages and safely discharge surge currents to earth.

Main Functions
·Overvoltage Protection: Limits lightning-induced and switching surge voltages.
·Equipment Protection: Protects insulation systems of transformers, circuit breakers, CTs, VTs, and cables.
·Surge Energy Dissipation: Conducts high surge currents safely to ground.
·System Reliability Improvement: Reduces equipment failure caused by transient overvoltage events.

Typical Applications
·Outdoor substations
·Transmission and distribution networks
·Transformer protection
·Generator protection
·Switchgear protection
·Cable termination protection
·Railway traction substations
·Renewable energy plants

Typical Technical Specifications
·Rated Voltage: 3 kV – 420 kV
·Maximum Continuous Operating Voltage (MCOV): According to system voltage
·Nominal Discharge Current: 5 kA / 10 kA / 20 kA
·Impulse Current Class: Class 1, 2, 3, 4
·Housing Material: Porcelain
·Protection Element: Zinc Oxide (ZnO) MOV
·Installation: Outdoor
·Frequency: 50 Hz / 60 Hz
·Mounting: Vertical installation

Construction
A typical porcelain housing arrester consists of:
1. Porcelain Insulator Housing
·Provides external insulation
·Resistant to weather and pollution
·High mechanical strength
·Suitable for outdoor environments
2. Zinc Oxide (ZnO) Valve Elements
·Non-linear voltage-current characteristics
·Conducts surge current during overvoltage
·Returns to high resistance after surge disappears
3. Internal Grading Components
·Ensures uniform voltage distribution
·Improves arrester performance at high voltage levels
4. Sealing System
·Prevents moisture penetration
·Maintains internal insulation reliability
5. Pressure Relief System
·Provides safe failure protection in case of internal faults

Operating Principle
During normal system operation:
·Arrester remains in a high-resistance state.
·Only a small leakage current flows.

During a surge event:
·Lightning or switching surge causes voltage rise.
·ZnO elements become highly conductive.
·Surge current flows through the arrester to earth.
·Voltage across protected equipment is limited to a safe level.
·Arrester returns to normal high-resistance condition after the surge.

Advantages
·Excellent mechanical strength
·High resistance to environmental aging
·Good outdoor insulation performance
·Long service life
·Stable electrical characteristics
·Suitable for high-voltage applications
·Reliable performance under pollution conditions
·Strong resistance to ultraviolet radiation

Common Types
Distribution Class Porcelain Arrester
·Used in distribution networks
·Typically below 36 kV
Intermediate Class Porcelain Arrester
·Used for industrial and substation applications
Station Class Porcelain Arrester
·Used for high-voltage substations and transmission systems
Gapless Metal Oxide Arrester
·Most modern design
·No series spark gaps
·Faster response and better protection performance

Typical Applications by Voltage Level
·6–12 kV Distribution transformers, switchgear
·24–36 kV Medium-voltage substations
·66–145 kV Substation equipment protection
·220–420 kV Transmission system protection

Applicable Standards
·IEC 60099-4 – Metal-oxide surge arresters without gaps for AC systems
·IEEE C62.11 – Metal-Oxide Surge Arresters for AC Power Circuits
·IEC 60099-5 – Selection and application recommendations for surge arresters

Key Features
·Porcelain insulated outdoor housing
·Zinc oxide (ZnO) non-linear resistor technology
·High discharge capability
·Excellent insulation coordination
·Low residual voltage
·Reliable lightning and switching surge protection
·Suitable for substations, transformers, and transmission networks
·Long maintenance-free service life