Key Takeaways
Why buried pipelines near HV/MV power cables face risks like induced voltage, corrosion, and coating stress.
How FEM-based simulations modeled electromagnetic interactions under both steady-state and fault conditions.
What the results revealed: induced voltages and currents stayed well below IEEE, CSA, and NACE safety limits.
How design measures (trefoil arrangement, trench conductors, strong grounding) minimized EMI effects.
Why EMI studies are critical for ensuring safe coexistence of power cables and critical infrastructure.
⏱ Estimated reading time: 5–6 minutes.
Project Overview
WiseGrid Energy recently carried out a detailed electromagnetic interference (EMI) study involving a 35 kV underground collector system and a parallel buried metallic pipeline. The goal was to determine whether the presence of HV and MV power cables in close proximity to critical infrastructure could pose risks such as induced voltages, accelerated corrosion, or coating stress during normal operation and fault events. The corridor under study included approximately 4 km of cable length, with separation distances between the cable trench and the pipeline ranging from as little as 5 meters to up to 50 meters, and included multiple physical crossings.
Technical Challenge
When underground HV cables share a corridor with metallic infrastructure such as pipelines, there is a risk of electromagnetic coupling through inductive, capacitive, and conductive paths. This coupling can induce voltages and currents in the pipeline, which if high enough, may cause:
• Safety hazards due to elevated touch voltages.
• Accelerated AC-induced corrosion.
• Excessive coating stress leading to insulation breakdown.
The challenge was to evaluate these risks under both steady-state load currents and under worst-case fault conditions.
Approach & Methodology
The analysis was conducted using the an advanced FEM based software suite, which solves Maxwell’s equations to model electromagnetic fields and interactions between power systems and adjacent metallic structures. The model included four circuits of 35 kV cables arranged in trefoil formation, installed in two trenches, each with a dedicated trench conductor for bonding. The pipeline was modeled with realistic physical and electrical properties, while soil resistivity was represented with a layered model based on summer conditions.
The study evaluated two scenarios:
1. Steady-State Conditions : when each cable circuit carries its rated balanced three-phase current (500 A).
2. Fault Conditions: when a single-phase-to-ground fault occurs, with a fault current up to 6kA.
Key Findings
The results demonstrated that the induced voltages and currents in the pipeline remained well within international safety and performance standards (IEEE, CSA, NACE) under both normal and fault conditions:
• Steady-State Operation:
– Maximum induced potential: 1.0 V.
– Maximum touch voltage: 0.9V (limit = 15 V).
– AC current density: 8.7 A/m² (well below the 20 A/m² corrosion risk threshold).
• Fault Condition (6.0 kA single-phase-to-ground fault):
– Maximum induced voltage: 95.0 V.
– Maximum touch voltage: 95.0 V (limit = 237 V).
– Maximum coating stress: 95.0 V (limit = 1 kV).
These results confirm that the studied system operates safely within applicable design thresholds.
Value Delivered
The study showed that despite close proximity (as small as 4 meters) and multiple crossings between power cables and pipelines, induced effects remained minimal due to effective design measures. Key factors contributing to low interference levels included:
• Adequate separation in most sections.
• Trefoil cable arrangements with concentric neutrals.
• The use of trench conductors bonded at regular intervals, which enhanced magnetic field cancellation.
• Strong grounding systems with low resistance at both the generation and substation ends.
By quantifying these interactions, WiseGrid Energy provided assurance that the infrastructure operates within safe limits without the need for additional mitigation measures. This project highlights the importance of comprehensive EMI studies in safeguarding infrastructure when power systems and pipelines share corridors.
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