Surge Arresters; Surge arrester works principle; Surge Suppersors

By -

Surge Arresters: Types, Working, and Applications

Surge arresters are one of the most important protective devices in electrical systems. They work on the same principle as lightning arresters—providing a low-impedance path to earth for transient overvoltages or lightning strikes, and then quickly restoring the circuit back to normal operating conditions.



👉 Think of a surge arrester like a safety relief valve in a boiler or hot water heater. When pressure (voltage) exceeds safe limits, the valve (arrester) opens and safely releases it to ground. Once the voltage returns to normal, the arrester resets and is ready for the next surge.

Functions of a Surge Arrester

  1. Provide a discharge path – Allow transient overvoltage (spike/surge) to pass to ground.
  2. Prevent follow current – Stop continuous current from flowing to ground after the surge has passed.

Types of Surge Arresters

1. Expulsion Type Arrester

  • Uses a series spark gap in a fiber tube.
  • When a surge occurs, an arc forms and gases are expelled, quenching the arc.
  • Low cost but requires frequent maintenance.

2. Valve Type Arrester

  • Uses nonlinear resistors (silicon carbide) in series with spark gaps.
  • Provides better voltage control compared to expulsion type.

3. Gapless Metal-Oxide Arrester (MOA)

  • Uses zinc oxide blocks without series spark gaps.
  • Provides very fast response and superior protection.
  • Most widely used modern surge arrester.

Surge Protective Devices (SPDs) by IEC Standard

Type

Installation Point

Tested Withstand

Use Case

Type 1

Main distribution board (with LPS)

Class I, 10/350 µs impulse

Direct lightning strike protection

Type 2

Main switchboard or sub-panels

Class II, 8/20 µs current

General surge protection in buildings

Type 3

Near sensitive equipment

Combination waveform (1.2/50 µs – 8/20 µs)

Protect delicate electronics

Surge Arresters by Class

Class

Application

Equipment Range

Substation Class

High voltage substations, >20 MVA equipment

Heavy-duty protection

Intermediate Class

Transformers, substations, 1–20 MVA

Medium-voltage protection

Distribution Class

Distribution transformers, 100 kVA range

Commonly used in networks

Secondary Class

Small appliances, low-level protection

Minimal protection, not for sensitive electronics

Other Protective Devices

  1. Earthing Screen – Provides shielding to substations/power stations by diverting lightning directly to ground.
  2. Overhead Ground Wires – Installed above transmission lines to intercept lightning strikes.
    • ✅ Effective, simple to implement
    • ❌ Expensive, risk of short circuits if they fall on conductors
  3. Lightning Arresters – Work along with surge arresters to safeguard overhead lines and substations.

Key Takeaway

  • Lightning arresters → Protect against direct strikes.
  • Surge arresters → Protect against transient overvoltages (switching + lightning-induced surges).
  • Modern installations rely heavily on gapless metal-oxide arresters (MOAs) for reliability.

Comments

Post a Comment

Popular posts from this blog

A2XWY; A2XFY Cables meaning; XLPE cables advantages over PVC cables

By -
Image
🏗 ️ Technical Specification of Aluminium Cables (IS 7098: Part 1 – 1988) When specifying aluminium cables, you will often come across codes like A2XWY . This code represents the construction, insulation, armouring, and sheath of the cable. 🔑 Cable Nomenclature Codes Code Meaning A Aluminium Conductor 2X XLPE (Cross-linked Polyethylene) Insulation Y PVC Outer Sheath W Steel Round Wire Armour F Steel Strip Armour WW Double Steel Round Wire Armour FF Double Steel Strip Armour Wa Non-Magnetic Round Wire Armour Fa Non-Magnetic Strip Armour AW Aluminium Wire Armour 👉 Example: A2XWY = Aluminium conductor + XLPE insulation + Steel round wire armour + PVC outer sheath. 📌 Note: For Copper Cables , no pref...
Read more

YWY, AYFY, AYY, AYCY, A2XCY Cables Meanings

By -
Image
📘 Cable Nomenclature Explained (PVC & XLPE Cables) Cable designations like YWY, AYFY, A2XCY might look confusing at first glance. But once you understand the logic behind each letter , reading technical specs becomes straightforward. 1. Basic Conductor Material ·          A → Aluminium conductor ·          (If “A” is absent, it means Copper conductor) 2. Insulation Material ·          Y → TROPODUR = PVC insulation ·          2X → TROPOTHEN-X = XLPE insulation 3. Armouring Types ·          W → Round Steel Wire Armouring ·          WW → Double Round Steel Wire Armouring ·          F → Flat (formed) Steel Strip Armouring ·       ...
Read more

Cable size and current carrying capacity

By -
Image
Cable size and current carrying capacity for XLPE insulated cable, non-armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. Cable size and current carrying capacity for XLPE insulated, Armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. For air and 20 degree Celsius for ground for installations require to comply with BS: 7671 Correction factors:- For Ambient temperature: Ambient temperature in degree Celsius Correction Factor 25 1.02 30 1.00 35 0.96 40 0.91 45 0.87 50 0.82 55 0.76 60 0.65 65 0.58 70 0.50 75 0.41 80 Ground Temperature Ambient temperature in degree Celsius Correction F...
Read more