IEC Relay Protection Code Table

IEC relay protection codes use standardized numbers and symbols to identify protective relay functions, often mapped to ANSI/IEEE device numbers for reference.

Overview of IEC Relay Codes

The International Electrotechnical Commission (IEC) defines relay functions using IEC 60617 graphical symbols and numeric codes. These codes identify the type of protection or control function a relay performs in a power system, such as overcurrent, undervoltage, or differential protection . Unlike ANSI device numbers, which are primarily numeric with optional suffix letters, IEC codes often combine numbers and symbols to represent the relay function clearly in diagrams and schematics .

Common IEC Relay Functions

Some of the widely used IEC relay protection codes include:

• 50 – Instantaneous overcurrent relay
• 51 – Time overcurrent relay
• 52 – AC circuit breaker
• 59 – Overvoltage relay
• 27 – Undervoltage relay
• 46 – Reverse phase or phase-balance current relay
• 87 – Differential protection relay
• 86 – Lockout relay
• 32 – Directional power relay These codes are used in single-line diagrams and relay schematics to indicate the specific protective function of each device .

Mapping IEC Codes to ANSI/IEEE Device Numbers

For engineers working in systems that use both IEC and ANSI standards, a conversion table is often used. For example:

• IEC 50 → ANSI 50 (Instantaneous overcurrent)
• IEC 51 → ANSI 51 (Time overcurrent)
• IEC 87 → ANSI 87 (Differential protection)
• IEC 59 → ANSI 59 (Overvoltage) This mapping helps in relay selection, documentation, and cross-standard design .

Usage in Protection Engineering

IEC relay codes are applied in:

• Substation protection schemes
• Motor and transformer protection
• Overcurrent, overvoltage, and differential protection
• Automation and control systems They provide a universal language for engineers to specify relay functions, ensuring consistency across international projects .

References for Detailed Tables

For a complete IEC relay protection code table, including graphical symbols and ANSI equivalents, the following resources are recommended:

• IEC 60617 standard for graphical symbols
• IEEE C37.2 standard for device numbers
• ABB Protection Relay Selection Table
• Online references comparing ANSI and IEC codes These references provide full tables, device descriptions, and typical applications, which are essential for protection engineers and system designers.