In transmission engineering, choosing the voltage level is never trivial. Electrical voltage levels in Chile define the network topology, minimum safety clearances, right-of-way width, structure type, and compliance with the SEC and the CNE.
In Chile, electrical voltage levels are classified as low voltage (≤1 kV), medium voltage (1–36 kV), high voltage (>36 kV up to 500 kV), and extra-high voltage (≥500 kV), according to the Regulations of the General Electric Services Law and associated technical standards.
This classification has a direct impact on the electrical and mechanical design of transmission lines. When selecting the electrical voltage level, we also choose conductors, calculate Joule losses, and define conductor-to-ground clearances and safety corridors required by the regulations.
A 66 kV project has nothing to do, in terms of CAPEX, permits, and rights-of-way, with a 220 kV or 500 kV project. The differences are drastic and, frankly, sometimes underestimated during the conceptual stage.
Official Classification of Electrical Voltage Levels in Chile (SEC and CNE)
The Superintendence of Electricity and Fuels (SEC) establishes the classification of voltage levels through Technical Regulatory Document RPTD No. 01. This document sets the nominal voltages and frequencies for the entire National Electric System.
The classification is not just a formality: it defines design criteria, minimum safety clearances, insulation requirements, and the regulatory scope of each installation.
Low Voltage (LV): Nominal voltages ≤1 kV in alternating current. This includes secondary networks and residential service connections.
Its impact lies in the design of switchboards, protection systems, and residential and industrial metering systems.
Medium Voltage (MV): Between 1 kV and 40 kV. The five distribution levels in Chile are 23 kV, 15 kV, 13.8 kV, 13.2 kV, and 12 kV.
These values determine compatibility with existing networks, MV cell sizing, and protection coordination.
High Voltage (HV): Between 40 kV and 220 kV. This includes subtransmission systems (66 kV, 110 kV) and backbone transmission (154 kV, 220 kV).
In this range, rights-of-way, structures, and minimum clearances change radically according to the NTCSE.
Extra-High Voltage (EHV): Nominal voltages ≥220 kV. In Chile, 500 kV lines require rights-of-way wider than 60 meters and large-scale structures.
Insulation coordination studies at this level are much more demanding and, honestly, the margin for error drops to zero.
From a project engineering perspective, this classification defines CAPEX. Moving from 66 kV to 110 kV means modifying conductor cross-sections, structure height, insulator type, and corridor width.
The official classification also covers generation, transport, and storage installations. An EPC project must consider these regulations from conceptual engineering through technical inspection of works.
Relevance of Voltage Levels in the Planning of the Chilean Electrical System
Electrical voltage levels define the complete architecture of the national electrical system. When planning transmission expansion, selecting the nominal voltage is not just a technical matter: it determines regulatory categories, remuneration models, safety requirements, and permitting timelines with the SEC and the CNE.
Integration with CNE Planning
The CNE classifies installations according to nominal voltage for centralized planning. HV lines ≥220 kV are part of the backbone and zonal system, subject to long-term transmission planning.
By contrast, MV or LV lines fall under the logic of additional or dedicated systems, with different investment and right-of-way criteria. It is not uncommon to see projects that, because of only a few kV, end up under a completely different regulatory regime.
Regulatory Categories by Voltage
- Backbone: ≥220 kV, centrally tendered expansion
- Zonal: 110 kV – <220 kV, planned by zoning
- Additional/Dedicated: <110 kV, developed by distributors or private project owners
This segmentation affects CAPEX, right-of-way timelines, and tariff structure. A jump from 110 kV to 220 kV changes the regulatory regime, and it is not always easy to anticipate all the consequences.
Safety and Continuity of Supply
Higher voltage levels imply greater system inertia and a reduction in short-circuit levels at remote points.
From experience, operating the National Electric System with a longitudinal topology requires redundancy in critical substations and transient stability analysis that depends, almost obsessively, on the selected voltage level.
Nominal voltage defines safety clearances, insulator type, structure dimensions, and right-of-way widths. All of these parameters can determine whether a corridor is technically and socially viable.
Technical Implications by Electrical Voltage Level in Chile
Each electrical voltage level brings with it specific design criteria that affect safety clearances, insulation specifications, and structural solutions.
These factors condition CAPEX, rights-of-way, and construction feasibility, sometimes in ways that are not visible until the detailed engineering stage.
Minimum Clearances According to Electrical Voltage Levels
The permitted nominal voltage variations established by the SEC define minimum clearances that increase exponentially with the electrical voltage level.
In low voltage (up to 1 kV), clearances to buildings can be 1.5 to 2 meters. In medium voltage (1 kV to 57.5 kV), they increase to 3–4 meters for 23 kV and up to 6–8 meters for 44 kV.
For high voltage, the impact is greater. At 110 kV, we need phase-to-ground clearances of at least 1.5 meters in substations and 6 meters on overhead lines.
At 220 kV, these values rise to 2.2 meters and 8–10 meters, respectively. There is not much room for improvisation here.
In extra-high-voltage systems (>230 kV):
- 500 kV requires 4.5 meters phase-to-ground and rights-of-way of 40–60 meters
- Vertical clearances above public roads reach 10–12 meters
- Tower sizing takes into account maximum sag under extreme temperature and wind
These clearances directly affect the width of the right-of-way, the number of affected properties, and the cost of land acquisition or compensation. Sometimes, that detail determines whether the project moves forward or remains on paper.
Insulation
The selection of insulators does not follow a linear relationship with voltage. We always work with electrical voltage levels and standardized insulation levels (BIL), considering switching surges and lightning impulses, in accordance with applicable technical standards.
| Voltage Level | Typical BIL | Number of Suspension Insulators | Specific Creepage Distance |
|---|---|---|---|
| 23 kV | 150 kV | 2–3 units | 20–25 mm/kV |
| 110 kV | 550 kV | 8–10 units | 25–30 mm/kV |
| 220 kV | 1050 kV | 14–18 units | 28–31 mm/kV |
| 500 kV | 1800–2100 kV | 26–32 units | 31–35 mm/kV |
In coastal areas or zones with high industrial pollution, we increase the specific creepage distance by around 20–30%. This helps prevent surface flashovers, which in turn requires longer strings or silicone insulators with a larger effective surface.
Insulation coordination with surge arresters and the Basic Insulation Level (BIL) establishes the protection margins and directly affects system reliability. If a 220 kV design is conservative, structure costs may rise by 15–20% due to greater weight and height.
Structures and Electro-Mechanical Design
Mechanical loads on towers and supports increase exponentially with voltage, since more conductors, heavier insulation, and longer spans are added. For 110 kV, we use lattice towers between 18 and 24 meters high, with foundations 2–3 meters deep.
At 220 kV, towers reach 30–40 meters, with vertical or triangular configurations. The weight of 400–750 MCM ACSR conductors per phase and OPGW ground wires generates loads of 15–25 tons per anchoring point.
Foundations require depths of 3.5–5 meters, with concrete blocks of 4–8 m³. It is not uncommon for calculations to yield values that seem oversized, but experience shows these margins are necessary.
For extra-high voltage (500 kV):
- Suspension towers 45–60 meters high and structural weight of 35–60 tons
- Double-circuit configuration, with 90–100 meters of base width
- Economic spans of 400–500 meters, compared to 250–350 meters at 220 kV
- Bundled conductors of 3–4 sub-conductors per phase
In substations, spacing between equipment at 220 kV ranges from 8–12 meters between phases. At 500 kV, that distance increases to 18–25 meters, multiplying the required yard area.
A 220 kV substation with 3 line bays occupies 8,000–12,000 m². At 500 kV, the same functionality requires 25,000–35,000 m². The jump in area and cost is brutal.
Structures in medium voltage (23–44 kV) use concrete poles 12–15 meters high and simple foundations 1.5–2 meters deep. Here, the cost per kilometer drops to one-quarter of that of a 110 kV line, although technical losses skyrocket over distances greater than 40–60 km.
Conductor Selection by Voltage Level
ACSR conductors still dominate in most Chilean lines, but technologies such as ACCC and HTLS have entered strongly, especially where electrical voltage levels and capacity requirements increase without modifying structures or rights-of-way. This is key in uprating projects and in areas with environmental restrictions or complex permitting.
ACSR
The ACSR (Aluminum Conductor Steel Reinforced) conductor remains the de facto standard in HV and MV lines in Chile, especially in projects with tight budgets or challenging topography. Its cost-to-mechanical-strength ratio makes it ideal for long spans and windy areas.
Its maximum operating temperature (75–90 °C, depending on design) limits transmission capacity. In projects above 220 kV, this restriction forces us to increase the cross-section or reduce spans, which directly impacts the CAPEX of structures and foundations.
ACSR shows higher electrical resistance than optimized alloys, and this translates into significant annual losses on heavily loaded lines. If one evaluates the life cycle (30-year OPEX), it is not uncommon for alternative technologies to be more convenient.
Applications where ACCC justifies the investment:
- Uprating 110–220 kV lines with original structures in good condition
- Projects with environmental constraints or impossibility of widening the right-of-way
- Lines with high load density and sustained growth projections
- Areas with high solar radiation or ambient temperatures above 35 °C
ACSR selection criteria:
- Spans greater than 400 m with high mechanical loads (wind, ice)
- Projects with initial budget constraints
- Lines with stable projected load and no planned expansions
- Compatibility with existing towers and insulators in replacements
ACCC
The ACCC (Aluminum Conductor Composite Core) conductor replaces the steel core with carbon fiber composite. This reduces weight by 20–40% and allows more aluminum in the same cross-section.
With ACCC, current capacity doubles compared to ACSR of the same diameter, operating at 180–200 °C without losing sag control or compromising structural fatigue. In the uprating of existing lines, this allows transmitted power to be doubled without touching towers, rights-of-way, or minimum clearances required by the SEC.
In practice, we evaluate ACCC when the cost of new right-of-way far exceeds the conductor differential. This happens often in urban, protected, or community-sensitive areas. The technical-economic analysis must weigh savings in structures, reduction of electrical losses, and faster regulatory approval.
HTLS and Performance
HTLS (High Temperature Low Sag) conductors include technologies such as ACCC, ACCR, GTACSR, and ZTACIR. All are designed to operate between 150–250 °C while maintaining controlled sag.
The benefit goes beyond thermal performance: on backbone lines, every additional MW has a high economic value, and HTLS can defer investment in new lines by 10–15 years. From the perspective of the CNE and expansion models, that incremental capacity affects energy planning and marginal costs.
In EPCM projects, integrating HTLS requires reviewing electrical clearances under contingency, adjusting protections (higher admissible short-circuit current), and validating high-temperature connectors and splices. The NTCSE does not specify conductors, but it does define minimum clearances, which must be recalculated considering sag at maximum operating temperature, not only at 75 °C.
We recommend a comparative CAPEX/OPEX analysis considering:
| Factor | ACSR | HTLS (ACCC/ACCR) |
|---|---|---|
| Operating temperature | 75–90 °C | 150–210 °C |
| Capacity (Amperes) | Base | +50% to +100% |
| Electrical losses | High DC resistance | Lower DC resistance |
| Relative cost | 1.0× | 1.8–2.5× |
| Impact on right-of-way | Requires widening | No changes |
Impact on Transmission Line Design
Electrical voltage levels determine from the outset the physical dimensions, mechanical loads, and construction criteria of a line. In our projects, moving from 110 kV to 220 kV usually doubles minimum safety clearances, increases structure costs by 40–60%, and widens the legal right-of-way by 5 to 15 meters per side.
Spans
Operating voltage defines the economic distance between supports and the type of admissible conductor. In high-voltage transmission lines, we use spans of 300–450 m at 220 kV and up to 500 m at 500 kV.
At 110 kV, we rarely exceed 350 m because of sag and galloping limitations. Selecting the optimum span is always a balance between the cost of towers, foundations, and conductor.
In mountainous areas, we have reduced spans to 250 m at 220 kV to control wind and ice loads on lattice structures. There is no universal formula, but experience helps avoid costly mistakes.
NTCSE criteria require recalculating sag with a temperature of 85 °C and wind of at least 130 km/h. In coast-to-mountain projects, we apply a design temperature of 95 °C and extreme wind of 150 km/h, which forces us to oversize insulator strings and phase-to-ground clearances.
Towers
Structures must guarantee minimum electrical clearances phase-to-phase and phase-to-ground according to the CNE’s minimum design requirements for transmission installations. In the case of 220 kV electrical voltage levels, we use a minimum separation of 2.6 m between phases in horizontal configuration and 3.0 m in vertical double circuit.
| Nominal Voltage | Phase-to-Phase Distance (m) | Phase-to-Ground Distance (m) | Minimum Conductor Height at Crossing (m) |
|---|---|---|---|
| 110 kV | 1.8–2.2 | 1.5 | 7.5 |
| 220 kV | 2.6–3.0 | 2.0 | 8.5 |
| 500 kV | 5.5–6.5 | 4.0 | 12.0 |
In our suspension tower designs, the clearance below the conductor determines the effective right-of-way width. Every time the electrical voltage level increases, we add between 1.5 and 3.0 m of structural height, which immediately affects weight, foundation design, and cost per support.
Foundations
Geotechnical sizing responds to the vertical, horizontal, and overturning loads transmitted by the superstructure. At 220 kV, a suspension lattice tower generates vertical loads of 80–120 kN per leg; at anchor or angle supports, these rise to 180–250 kN.
We have used gravity foundations in competent soils (allowable bearing capacity > 2.5 kg/cm²) and drilled piles where soft clays or fills are present. Typical depth ranges from 3.5 m at 110 kV to up to 6.0 m at 500 kV, depending on the stratigraphic profile and water table.
Foundation costs represent between 18% and 25% of the total CAPEX of the line. When we identify collapsible or highly plastic soils, we opt for 15–20 m long micropiles with grout injection—yes, it is more expensive, but it reduces the risk of differential settlement.
Mechanical Stresses
Mechanical loads on conductors and structures come from self-weight, wind, ice, and imbalance due to phase breakage. According to the NTCSE, we size conductors for a maximum tension of 50% of the breaking load (EDS) under normal conditions, and up to 70% under extraordinary load assumptions.
In areas with high saline contamination, corrosion ends up reducing the mechanical strength of ACSR conductors by 8–12% after 15 years of operation. That is why, in transmission line projects near the coast, we specify alloys with higher aluminum content or anti-corrosion coatings.
We calculate wind loads with dynamic pressure of 1.0–1.3 kN/m² in the central zone and up to 1.8 kN/m² in mountainous areas. A 220 kV line with 477 MCM ACSR conductor can experience wind loads of 18–22 kN per 400 m span, so we size anchor strings with 12–15 disc insulators of 146 kN each.
Operational Safety and Safety Clearances by Electrical Voltage Levels
Minimum clearances and operational safety criteria vary significantly depending on electrical voltage levels, which has a direct impact on structure design, rights-of-way, and maintenance protocols. SEC regulations establish specific corridors and clearances that end up conditioning both CAPEX and route feasibility in HV and MV projects.
Clearances to Buildings and Roads
The voltage level dictates the minimum horizontal and vertical separations from structures and roads. In projects of 110 kV or more, these clearances may exceed 5 meters horizontally, considering maximum conductor sag and wind deviation.
For MV distribution lines (23 kV), the clearances are smaller but still critical in urban areas. The regulations on safety clearances require calculations considering an ambient temperature of 15 °C and maximum sag conditions.
Operational impact:
- Modification of structure height at road crossings
- Need for wider rights-of-way in HV
- Coordination with municipalities for construction permits
- Restrictions on permanent buildings under lines
In EPC projects, if we underestimate these clearances, we face delays in environmental processing and conflicts with landowners. We recommend validating clearances with real topography before detailed engineering.
These restrictions, which depend directly on the electrical voltage level, condition route feasibility and ultimately affect timelines, CAPEX, and territorial acceptance. That is why, at Esinel, we validate regulatory clearances with real topography during basic engineering, avoiding redesigns during construction and SEC observations at critical stages of the project.