What is High-Voltage Equipment Discharge?
High voltage (HV) equipment discharge is the unintended release of the electrical energy in the form of:
- Partial Discharge,
- Corona Discharge,
- Arc Flash,
- Dielectric Breakdown.
These discharges can be caused by insulation failure, air gaps, moisture, or aging equipment, and they frequently result in sparks, electrical arcs (or) high-temperature surfaces.
Why is it important in Hazardous Environments?
Hazardous regions are those in which combustible gasses, fumes, or dust are prevalent.
In such conditions, even a small spark from an HV discharge can cause an explosion.
Typical hazardous areas:
- Petrochemical plants
- Refineries
- Grain silos
- Chemical processing zones
- Underground mines.
Risk Types
| Discharge Type | Risk in Hazardous Area |
|---|---|
| Corona Discharge | Can ignite gas-air mixtures |
| Partial Discharge | Leads to long-term insulation failure, potential flashover |
| Arc Flash | High temperature (up to 20,000°C), explosion risk |
| Electrostatic Discharge | Sparks in flammable atmosphere |
Key Safety Measures
Zoning and Classification
- To classify hazardous zones, use IEC 60079 or NEC 500/505 (Zone 0, 1, 2, or Class I Division 1/2).
- Utilize explosion-proof (or) intrinsically safe equipment in classified areas.
Proper Grounding and Bonding
- Prevent electrostatic buildup and discharge.
- Use of flameproof high-voltage equipment
- Utilize Ex-d, Ex-e, or Ex-p-protected HV panels & switchgear.
Regular Inspection and Testing
- Partial Discharge (PD) Testing
- Insulation Resistance Tests
- Thermographic scan for hotspots
Environmental Control
- Dehumidifiers & air purging devices are used to avoid moisture and dust collection.
- Control of the Maintenance Work
- Permit-to-Work (PTW) systems.
- Use of inherently safe tools.
- No live testing unless in a safe zone.
Standards
| Standard | Description |
|---|---|
| IEC 60079 Series | Equipment use in explosive atmospheres |
| IEC 62271-200 | High-voltage switchgear and control gear |
| NFPA 70 (NEC) | Electrical installations in hazardous locations |
| IS/IEC 60079 (India) | National adaptation of IEC hazardous area standards |
Discharges from high-voltage equipment provide considerable ignition threats in combustible conditions. Proper design, equipment selection, zoning & maintenance practices are essential for avoiding catastrophic explosions or fires.
When developing or maintaining high-voltage systems in hazardous regions, always involve qualified workers and strictly adhere to applicable requirements.