You're asking about safety clearances between Ultra High Voltage (UHV) / Extra High Voltage (EHV) cables and the presence of coke/blast furnace gas, along with the need for an Electromagnetic Compatibility (EMC) study. Here's a breakdown of what standards are likely relevant and why EMC is important

1. Relevant Standards & Guidelines for Clearances:
National Electrical Codes (NEC) / International Electrotechnical Commission (IEC) Standards



NEC (Primarily North America)

The National Electrical Code (NFPA 70) provides general requirements for electrical installations. While it doesn't specifically call out coke/blast furnace gas, it does address hazardous (classified) locations. Article 500 deals with these hazardous environments, and the NEC would require rigorous area classification of the coke/blast furnace gas area. This determines which wiring methods, equipment, and installation practices are permitted.

IEC (Globally Used)

IEC 60079-10-1 (Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres) provides guidance for classifying hazardous areas where flammable gases or vapors may be present. IEC standards are often adopted or adapted by national standards.

Key Concept

The presence of coke/blast furnace gas introduces the potential for explosive atmospheres. The area must be classified based on the frequency and duration of explosive gas presence (e.g., Zone 0, Zone 1, Zone 2 per IEC or Class I, Division 1, Division 2 per NEC).

Clearances Depend on Area Classification

The required clearance distances are heavily dependent on the zone/division classification. Zone 0/Division 1 areas have the most stringent requirements, and Zone 2/Division 2 areas are less restrictive.

Overhead Line Standards (National or Utility-Specific)



IEEE Std 1246

IEEE Guide for Temporary Protective Grounding Systems Used in Substations. While not directly addressing gas, it gives principles for safe grounding in electrical environments.

EN 50341 (Overhead Lines Exceeding AC 1 kV)

This is a European standard, but its principles are widely applied. It covers clearances to buildings, ground, and other objects. You'll need to look at the specific national deviations from EN 50341 that apply in your region.

Utility-Specific Standards

Most large utilities have their own detailed engineering standards that go beyond the national codes. These standards will likely address clearances to industrial facilities and potential hazards.

Key Concept

Overhead line standards specify minimum vertical and horizontal clearances for safety. These clearances are affected by voltage, sag, wind, and ice loading on the conductors.

Gas Industry Standards



Standards related to handling, storing, and transporting blast furnace gas or coke oven gas. These standards may specify exclusion zones or safety distances from electrical equipment. Check with local gas industry regulatory bodies.

How to Determine the Clearances


Hazardous Area Classification

Perform a thorough hazardous area classification study in accordance with IEC 60079-10-1 or NEC Article 500, as appropriate. This must be done by qualified personnel.2.

Consult Local Regulations and Utility Standards

Contact your local electrical inspector, regulatory authority, and the utility that owns the UHV/EHV lines. They will be able to provide the specific requirements that apply to your location.3.

Apply the Most Stringent Requirements

Choose the most conservative (largest) clearance distance from all applicable standards.4.

Consider Incident Scenarios

Think about potential events like gas leaks, explosions, or electrical faults. The clearance should be large enough to minimize the risk of these events affecting each other.

2. Need for an EMC (Electromagnetic Compatibility) Study



Absolutely YES. An EMC study is highly recommended, and may be mandatory, in this situation. Here's why: Potential Ignition Source

High-voltage cables generate electromagnetic fields. These fields can induce currents in nearby metallic objects (pipelines, structures, fences, etc.). If these currents are high enough, they can cause sparks or arcs that could ignite the coke/blast furnace gas.

Interference with Gas Detection Systems

The electromagnetic fields from the UHV/EHV lines can interfere with the operation of gas detection systems, making them unreliable. This is a major safety concern.

Corrosion

Stray currents induced by electromagnetic fields can accelerate corrosion in metallic structures. This can weaken pipelines and other critical components, leading to gas leaks.

Compliance with Regulations

Many jurisdictions require EMC studies for new electrical installations near hazardous areas.

What an EMC Study Should Include



Modeling of Electromagnetic Fields

Use software tools to model the electric and magnetic fields generated by the UHV/EHV lines under various operating conditions.

Induced Voltage and Current Calculations

Calculate the voltages and currents that could be induced in nearby metallic objects.

Arcing Risk Assessment

Determine the probability of arcing or sparking occurring.

Interference Assessment

Evaluate the potential for interference with gas detection systems, communication systems, and other sensitive electronic equipment.

Mitigation Measures

Identify and recommend mitigation measures to reduce the risk of ignition, interference, and corrosion. These measures may include:

Shielding

Using conductive shields to reduce electromagnetic field coupling.

Grounding and Bonding

Properly grounding and bonding metallic objects to minimize potential differences.

Surge Protection

Installing surge protection devices to protect equipment from voltage surges.

Filtering

Using filters to reduce electromagnetic interference.

Relocation

In some cases, relocating the UHV/EHV lines or the gas processing equipment may be necessary.*

Testing

Conduct on-site testing to validate the model and confirm the effectiveness of mitigation measures.

Who Should Perform the EMC Study?

The EMC study should be performed by qualified EMC engineers with experience in high-voltage systems and hazardous area safety. They should be familiar with relevant EMC standards and regulations.

In summary, proper planning, adherence to relevant standards, and a thorough EMC study are crucial to ensure the safe operation of UHV/EHV lines near coke/blast furnace gas facilities. Flag for review