ICEA S-94-649 Cable

XLPE TR-XLPE EPR Insulated single core concentric neutral cables rated 5 to 45KV which are used for the transmission and electrical energy. distribution of electrical energy.

1. Standard Overview

1. Standard No:

ICEA S-94-649 is a North American standard for medium-voltage power cables, published by the Insulated Cable Engineers Association (ICEA). Its full title is “Concentric Neutral Cables Rated 5 Through 46 kV.”

It is also recognized as a national standard by the American National Standards Institute (ANSI) and is therefore commonly cited as ANSI/ICEA S-94-649. This standard is widely regarded as one of the most critical technical specifications for medium-voltage underground distribution cables used in North America.

2. Voltage Ratings:

This standard applies specifically to solid dielectric insulated cables with a concentric neutral construction.

• Voltage Rating: 5 kV through 46 kV (phase-to-phase).
• Core Construction: Single-conductor or multiplexed (multi-conductor) concentric neutral cables.
• Application Environments: Suitable for wet, dry, direct burial, duct, or sunlight-resistant outdoor installations, primarily for power distribution.

3. Insulation Materials:

ICEA S-94-649 has three primary insulation materials, each offering different levels of electrical performance, especially regarding water tree resistance:

1. Cross-linked Polyethylene – Standard XLPE with excellent electrical and thermal-mechanical properties.
2. Tree-Retardant Cross-linked Polyethylene – TR-XLPE, modified to inhibit water treeing, significantly extending cable life in wet environments.
3. Ethylene Propylene Rubber – EPR, offering good flexibility and heat resistance.

4. Cable Construction:

The standard details a layered construction typical of URD (underground residential distribution) concentric neutral cables:

Conductor
Annealed copper or aluminum, compressed, compact,round.

Conductor Shield
Extruded semi-conducting layer that provides a smooth electrical interface and prevents partial discharge between the conductor and insulation.

Insulation
The primary dielectric layer. Nominal thickness varies by voltage rating (e.g., 15 kV class typically uses 220 mils).

Insulation Shield
Extruded semi-conducting layer.

• Stripping Force: A distinctive requirement – the standard specifies a quantifiable range for insulation shield strip force. For example, pulling a 0.5-inch-wide strip parallel to the conductor typically requires 3 to 24 lbf. This ensures the shield is easy to remove for terminating yet remains electrically sound.
• Resistivity: Volume resistivity shall not exceed 500 Ω·m.

Concentric Neutral
This is the defining feature of the standard. It consists of annealed bare copper wires helically wound over the insulation shield.

• Function: Carries return current (serving as the neutral) and provides a fault current return path.
• Configuration: The number, gauge, and lay pitch of neutral wires are carefully calculated. Industry sometimes uses dedicated “concentric neutral calculators” to verify compliance with ICEA S-94-649.

Jacket (Outer Sheath)
Extruded thermoplastic or linear low-density polyethylene (LLDPE).

• Function: Provides mechanical protection, waterproofing, and corrosion protection for the neutral wires.
• Requirements: The jacket must tightly fit (but not bond to) the neutral wires, fill the interstices, and resist sunlight exposure (typically via a 720-hour accelerated weathering test).