AGL Series Cable VS Conventional LV Cable
AGL series cable is specially designed for medium-voltage, constant-current airfield lighting series circuits. Conventional LV cable is designed for conventional low-voltage electrical distribution, generally in parallel circuits. The biggest difference is the circuit philosophy: AGL uses a series circuit with a Constant Current Regulator (CCR), while conventional LV distribution normally uses constant voltage with parallel loads.
At a Glance
| Feature | AGL Series Cable | Conventional LV Cable |
|---|---|---|
| Typical system | Airfield Ground Lighting | General electrical distribution |
| Circuit type | Series | Usually parallel |
| Supply | Constant Current Regulator (CCR) | Constant-voltage source |
| Typical operating voltage | Can be several kV, design-dependent | Typically LV system voltage |
| Current | Controlled by CCR | Depends on connected load |
| Main purpose | AGL series lighting circuit | Power distribution |
| Individual light connection | Through isolation transformer | Usually directly/parallel connected |
| Insulation requirement | Medium-voltage series-circuit insulation (rated to 5,000V per FAA L-824) | LV insulation appropriate to system |
| Cable construction | AGL-specific | General-purpose power cable |
| Installation environment | Airfield pavement/duct/trench | Building, underground, industrial, etc. |
| Main design concern | Series-circuit integrity and insulation | Voltage drop, ampacity, fault protection |
What Is AGL Series Cable & Conventional LV Cable?
AGL Series Cable
A cable system designed for the series-circuit environment of airfield ground lighting, where a CCR regulates the current through a string of isolation-transformer-fed fixtures rather than applying a fixed voltage across parallel loads. In the FAA framework this is the L-824 underground electrical cable, specified under AC 150/5345-7 in 600V and 5,000V ratings with EPR (Type B) or XLPE (Type C) insulation.
Main characteristics
- Carries the CCR-regulated series-circuit current
- Insulated for the circuit's operating voltage (commonly rated 600V or 5,000V), not just its current
- Interfaces each fixture through an isolation transformer
- Uses AGL-specific connectors and accessories where required
Conventional LV Cable
A general-purpose power cable designed for constant-voltage LV distribution, where loads are connected in parallel across the supply and draw current according to their own characteristics.
Main characteristics
- Sized around ampacity, voltage drop and fault protection
- Loads connected in parallel, independently
- Uses conventional LV accessories and terminations
- Suited to buildings, underground and industrial distribution
The Biggest Difference
The easiest way to remember the difference between AGL series cable and conventional LV cable:
AGL Series Cable
CCR → constant current → series cable → isolation transformer → light
Conventional LV Cable
LV supply → constant voltage → LV cable → parallel load
Easy memory: AGL cable → series + CCR. LV cable → parallel + constant voltage.
Series Cable vs Parallel LV Cable
AGL Series Circuit
The CCR regulates the series-circuit current; each light is connected through its own isolation transformer.
Conventional LV Circuit
Each load is connected independently across the LV supply; the supply maintains system voltage while the loads determine their own current.
Series-Circuit Voltage Considerations
An AGL series circuit can reach a relatively high circuit voltage because the voltage across the complete circuit depends on the number of connected loads and the transformer characteristics — not on a single fixed system voltage as in LV distribution. The cable insulation system must therefore be suitable for the specified AGL series-circuit voltage and environmental conditions.
A conventional LV cable selected only for normal LV distribution should not automatically be used for an AGL series circuit, even where its conductor current rating looks sufficient.
How Current Behaves on Each System
| Condition | AGL Series Cable | Conventional LV Cable |
|---|---|---|
| Governing quantity | Regulated series current from the CCR | Voltage held constant by the supply |
| Current through the cable | Same regulated current through the whole circuit | Varies with each connected load |
| Effect of adding a load | Current stays at the set value; voltage adjusts | Total current increases with the added load |
| Circuit topology | Loads connected one after another (series) | Loads connected independently (parallel) |
Voltage-Drop Design Doesn't Carry Over
On a conventional LV system, voltage drop is normally evaluated along the cable to ensure the load receives an acceptable voltage at its terminals. On an AGL series circuit, the circuit is operated using a regulated current, and the circuit voltage is instead related to the total series-circuit impedance and connected load — it is the outcome of the regulation, not the design target in the same sense.
AGL cable design should not simply be treated like ordinary LV voltage-drop design. The series-circuit impedance and required circuit voltage need their own calculation, based on the CCR and connected transformer/load characteristics.
What Governs Selection for Each
AGL Series Cable Selection
- System/circuit voltage
- Conductor size
- Current rating
- Insulation system
- Mechanical strength
- Environmental suitability
- Installation method
- Compatibility with AGL connectors and transformers
Conventional LV Cable Selection
- System voltage
- Continuous current/ampacity
- Voltage drop
- Short-circuit withstand
- Installation method
- Ambient temperature
- Grouping
- Mechanical/environmental conditions
Where Each Is Installed
AGL series cable may be installed in underground ducts, trenches, airfield cable routes, pavement crossings and cable pits — the installation must account for the airfield environment and the applicable AGL installation requirements. Conventional LV cable is typically installed in buildings, underground runs, and industrial or general electrical settings, following standard LV installation practice.
Connecting the Cable to the Load
AGL systems use specialized connection methods — AGL-specific connectors interfacing the series cable to each isolation transformer — to maintain electrical and environmental integrity along the circuit. A conventional LV installation may instead use standard cable glands, lugs, joints and termination systems appropriate to general LV installation practice.
Why You Should Not Substitute LV Cable on an AGL Circuit
Even if the conductor current is apparently sufficient, a conventional LV cable may not meet the requirements of an AGL series circuit — including voltage rating, insulation requirements, AGL connector compatibility, environmental requirements, mechanical requirements and project/airport specifications.
Cable selection must be based on the complete AGL circuit design and applicable specification, not conductor ampacity alone.
Full Comparison Table
| Parameter | AGL Series Cable | Conventional LV Cable |
|---|---|---|
| Supply architecture | CCR | LV constant-voltage supply |
| Circuit | Series | Usually parallel |
| Circuit voltage | Potentially several kV, system-dependent | LV |
| Current | Regulated | Load-dependent |
| Individual light | Isolation transformer | Usually direct parallel connection |
| Insulation | Suitable for AGL series-circuit voltage | Suitable for LV voltage |
| Main design objective | Reliable series circuit | Reliable power distribution |
| Cable accessories | AGL-specific where required | Conventional LV accessories |
| Application | Runway/taxiway/approach lighting circuits | General electrical loads |
Practical Difference
Think: AGL Series Cable
CCR → series cable → isolation transformer → light
Think: Conventional LV Cable
Supply → LV cable → parallel load
Myths vs Facts
AGL cable is a system designed for the electrical, mechanical and environmental requirements of a series circuit — insulation and connector compatibility matter as much as current rating.
Conductor ampacity alone is not enough — voltage rating, insulation, connector compatibility, and environmental and project requirements must all be checked before substitution is even considered.
AGL series circuits are governed by regulated current, and the circuit voltage is the outcome of total series-circuit impedance — it isn't evaluated with ordinary LV voltage-drop methods.
Choosing the Right Cable
When selecting cable for an AGL project, establish:
- Whether the circuit is series (CCR-fed) or a conventional LV parallel distribution circuit
- The specified series-circuit voltage or LV system voltage, as applicable
- Required insulation system and mechanical/environmental rating
- Compatibility with the specified connectors, transformers and accessories
- Applicable ICAO/national AGL requirements
- Airport-specific technical specifications and approved cable types
Which Cable Applies Where?
AGL series cable is purpose-built for the series-circuit environment of airfield ground lighting, carrying a CCR-regulated current at a circuit voltage that can be relatively high, insulated and constructed for that duty and its environment. Conventional LV cable is designed for constant-voltage parallel distribution, sized around ampacity, voltage drop and fault protection rather than series-circuit insulation.
The final selection for an actual airport project should always be based on the applicable current ICAO/national AGL standard, the approved circuit design and project cable specifications — not on a generic comparison alone.
Engineering & Expert Notes
Do Not Reuse LV Cable in a Series Circuit
CompatibilitySeries circuits operate at higher voltage and need cable rated and approved for that duty. Cable that looks similar may not be.
Water Resistance Is Part of the Specification
EnvironmentUnderground AGL cable faces moisture for decades. Check sheath and insulation suitability for the installation conditions.
Jointing Skill Matters as Much as the Cable
WorkmanshipA good cable can be ruined by a poor joint. Use trained staff, approved kits and recorded procedures.
Record Cable Type on the As-Built
RecordsFuture fault finding depends on knowing exactly what was installed and where.
Frequently Asked Questions
AGL series cable carries a CCR-regulated current on a series circuit feeding fixtures through isolation transformers, while conventional LV cable carries a constant voltage to loads connected in parallel.
Not automatically. Conductor ampacity alone does not confirm suitability — voltage rating, insulation, connector compatibility and environmental/project requirements must all be checked first.
Because the voltage across a complete AGL series circuit depends on the number of connected loads and transformer characteristics, and can reach a relatively high value that a standard LV insulation system is not designed for.
No. LV cable design evaluates voltage drop along the cable at constant voltage; an AGL series circuit is governed by regulated current, and its circuit voltage is derived from the total series-circuit impedance instead.
AGL fixtures are connected through an isolation transformer on the series circuit, while LV loads are usually connected directly or in parallel across the supply.
Underground ducts, trenches, airfield cable routes, pavement crossings and cable pits — the cable and its installation must account for the airfield environment and applicable AGL requirements.
No. Selection must be based on the complete AGL circuit design and applicable specification — voltage rating, insulation, connector and transformer compatibility, and environmental/mechanical requirements — not conductor ampacity alone.
Governing Documents
For an actual airport project, verify the current applicable editions of the relevant standards and the specific cable manufacturer's datasheets before using this comparison for project design.
FAA AC 150/5345-7 (L-824 Cable)
Specification for L-824 Underground Electrical Cable for Airport Lighting Circuits — the governing cable spec for AGL series circuits, covering 600V/5,000V EPR and XLPE constructions. Underlying cable construction also draws on ICEA S-96-659 (NEMA WC71).
ICAO Annex 14, Volume I
Aerodrome Design and Operations — series circuit requirements, CCR characteristics and isolation transformer interfacing for AGL.
ICAO Aerodrome Design Manual
Applicable material covering series circuit design, cable insulation requirements and electrical infrastructure guidance.
National CAA / DGCA / AAI Requirements
For Indian airport projects, also verify applicable DGCA requirements, AAI requirements, airport-specific technical specifications, project drawings and contract specifications.
Final Engineering Note
Exact cable voltage rating, insulation system and connector compatibility requirements can vary with the governing standard, equipment manufacturer and approved airport design. For final design, use the current applicable standard and manufacturer datasheets rather than a generic comparison page.
AGL series cable is built for a CCR-regulated series circuit with isolation-transformer-fed fixtures; conventional LV cable is built for constant-voltage parallel distribution — the two are not interchangeable based on current rating alone.
Compare the Systems. Then Learn How to Engineer Them.
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