Cable Lug / Crimp Terminal Symbol
Definition: The Cable Lug / Crimp Terminal symbol represents a mechanical crimped or compression terminal — standardised under IEC 61238-1 and ANSI/NEMA standards — that permanently joins a stranded conductor to a bolted connection point such as a busbar, earthing stud, or equipment terminal, providing a gas-tight, low-resistance electrical joint.
Also known as: cable lug, crimp terminal, compression lug, ring terminal, fork terminal, tongue terminal, cable end terminal.
What the Cable Lug / Crimp Terminal symbol means
The Cable Lug / Crimp Terminal symbol marks a conductor termination where a bare or insulated lug barrel is crimped onto the stripped end of a stranded cable, and the flat tongue of the lug is then bolted to a terminal stud or busbar. The symbol indicates the physical end of a conductor run and the method of connection — crimping rather than screw-clamping or soldering.
In power and earthing diagrams the symbol communicates the lug type (ring, fork, pin, or bootlace ferrule), the conductor cross-section, and sometimes the bolt-hole diameter. Engineers use it to specify correct tooling, verify conductor sizing, and ensure the termination meets the current-carrying and mechanical requirements of the installation per IEC 60947-7-1 (terminal blocks) and IEC 61238-1 (compression joints).
How to identify the Cable Lug / Crimp Terminal symbol
The cable lug symbol is drawn as a short rectangle (representing the crimp barrel) connected to a flat oval or ring shape (the tongue with the bolt hole). The top pin (Wire) represents the cable conductor entering the barrel from above, and the bottom pin (Bolt) represents the bolt-hole tongue that attaches to the terminal stud. Ring-type lugs show a closed circle at the tongue; fork/spade types show a U-shape.
Function and usage boundary
A cable lug creates a gas-tight mechanical and electrical joint between a stranded conductor and a bolted connection point. The crimping process compresses the barrel around the conductor strands, eliminating voids that would cause oxidation and increasing resistance over time. The flat tongue then distributes the clamping force of the bolt evenly across the contact area, providing a stable, vibration-resistant connection capable of carrying full rated current without significant voltage drop.
Standards: IEC vs ANSI
| IEC 60617 | IEC 61238-1 specifies compression and mechanical connectors for power cables up to 36 kV, including type testing for crimped lugs. IEC 60228 classifies conductor constructions. IEC 60947-7-1 covers terminal block requirements where lugs terminate. The symbol appears in panel wiring diagrams and earthing layouts. |
|---|---|
| ANSI/IEEE 315 | ANSI/NEMA CC1 covers the electric power connectors including compression lugs. UL 486A-486B covers wire connectors for aluminium and copper. ANSI/IEEE 315 (IEEE Std 315-1975) does not define a dedicated crimp lug symbol; US drawings use a text annotation or generic terminal symbol. |
| Key difference | IEC practice uses a graphical crimp-lug symbol in panel layout and earthing drawings. ANSI/US practice typically annotates the conductor end with a text call-out specifying lug type and part number rather than a distinct standardised glyph. |
The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.
Logical terminals
| Logical ID | Editor terminal name |
|---|---|
| wire | Wire |
| bolt | Bolt |
Where the Cable Lug / Crimp Terminal symbol is used
- Busbar connections in switchgear and MCC panels — bolting power conductors to copper or aluminium busbars
- Earthing and bonding systems — connecting earth conductors to earth bars and equipment studs per IEC 60364-5-54
- Motor terminals — terminating flexible motor leads onto the motor terminal box studs
- Battery systems — connecting battery cables to battery posts and inter-cell links
- Solar PV and energy storage — large-format cable lugs on DC cable runs between inverters and battery banks
- Transformer connections — secondary conductor lugs bolted to low-voltage transformer terminals
- Cable trays and trunking — splice connectors and through-lug joints between cable sections
Key facts
- A cable lug (crimp terminal) is a mechanical connector that permanently joins a stranded conductor to a bolted terminal via compression crimping, creating a gas-tight joint per IEC 61238-1.
- The symbol has two pins: Wire (conductor entering the crimp barrel) and Bolt (the tongue that bolts to the terminal stud or busbar).
- Lug types include ring (closed hole), fork/spade (open U-slot), pin/ferrule (for socket terminals), and tubular splice connectors.
- Correct tool-die selection is critical: the wrong crimp die leaves voids in the barrel that cause oxidation, increased resistance, and eventual failure — IEC 61238-1 mandates resistance and pull-out testing.
- Conductor cross-sections range from 0.5 mm² (control wiring) to 630 mm² (LV power cables); AWG 22 to 4/0 in North American practice.
- Bi-metallic (Al/Cu) lugs must be used when connecting aluminium conductors to copper bus to prevent galvanic corrosion.
- In earthing systems, earthing lugs must be sized to carry the prospective fault current for the fault clearance time without exceeding the adiabatic limit (IEC 60364-5-54, IEC 60909).
Frequently asked questions
What does the cable lug symbol mean in a wiring diagram?
The cable lug symbol indicates the method and point of termination for a conductor — specifically a crimped compression lug that attaches the conductor to a bolted terminal. It communicates lug type (ring, fork, pin), conductor cross-section, and bolt-hole size to the installer and specifies that a crimp tool must be used rather than soldering or a screw clamp.
What does the cable lug / crimp terminal symbol look like?
The cable lug symbol shows a rectangular barrel (the crimp section) connected to a flat oval or ring tongue (the bolt-hole section). The Wire pin enters the top of the barrel representing the stripped conductor, and the Bolt pin at the bottom represents the tongue face that contacts the busbar or stud. Ring lugs have a closed circle; fork lugs show an open U-slot.
What standard covers cable lugs?
IEC 61238-1 is the primary international standard for compression and mechanical connectors for power cables; it specifies type-test requirements including electrical resistance, tensile strength, and heat-cycle performance. In North America, ANSI/NEMA CC1 and UL 486A-486B govern compression lugs and wire connectors.
What is the difference between IEC and ANSI representations of cable lugs?
IEC-based drawings use a graphical symbol for the crimp lug in earthing and panel wiring diagrams. ANSI/IEEE 315 drawings typically use a text annotation or a generic terminal dot rather than a distinct lug glyph, with the lug type and part number called out in a separate BOM or terminal schedule.
When should I use a ring lug versus a fork (spade) lug?
Ring lugs provide a more secure connection because the conductor cannot slide off the stud even if the nut is slightly loose — they are preferred for power, earthing, and vibration-prone applications. Fork (spade) lugs allow disconnection without fully removing the nut, making them convenient for control wiring and frequently serviced terminals, but they risk dislodging if the nut loosens.
Why must bi-metallic lugs be used for aluminium conductors?
Connecting an aluminium conductor directly to a copper busbar with a copper lug creates a galvanic cell that corrodes the aluminium and increases contact resistance over time. Bi-metallic (Al/Cu transition) lugs have an aluminium barrel (matched to the conductor) and a copper tongue (matched to the busbar), preventing direct Al-Cu contact and ensuring a stable, low-resistance joint.
How do I size a cable lug for an earth conductor?
The earth conductor cross-section is sized using the adiabatic equation in IEC 60364-5-54: S = (I × √t) / k, where I is the prospective fault current in amperes, t is the fault clearance time in seconds, and k is a material constant (115 for copper conductors with PVC insulation). The lug barrel must match the calculated conductor cross-section, and the tongue must fit the earthing stud diameter.
Related symbols
- Doorbell Camera symbol
- Fuse Terminal Block symbol
- Ground / Earth symbol
- Neutral Rail symbol
- Power Rail symbol
- Terminal Block symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
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