The ABB SPAJ 110 C-AA is a secondary protection relay designed for earth-fault detection in power systems. It connects to current transformers (CTs) and can measure earth-fault currents using either residual current (three-phase CTs) or core-balance CT methods. When a fault occurs, the ABB Overcurrent and Earth-Fault Relay SPAJ 110C triggers alarms, trips circuit breakers, or initiates auto-reclose functions based on its configuration, ensuring reliable system protection.

The Earth-fault relay SPAJ 110 C  features adjustable low-set (Io>) and high-set (Io>>) stages with definite-time (DT) or inverse-time (IDMT) operation. The IDMT mode offers four standardized curves (Normal, Very, Extremely, and Long-time Inverse), complying with IEC 255 and BS 142. A start signal contact function allows coordination with other relays, while an optical logic input enables external blocking signals for enhanced system integration.

To maximize reliability, the New in box ABB SPAJ 110 C-AA Integrated protective relay includes an auto-diagnostic system that continuously monitors hardware, software, and auxiliary power. If a fault is detected, the relay illuminates an IRF indicator, activates an output relay, and sends a fault code via its display or serial communication. This proactive self-supervision reduces downtime and improves system availability.

Ideal for substations and industrial networks, the Comprehensive Protection Relay SPAJ 110 C-AA ensures precise earth-fault protection with flexible settings and robust diagnostics. Its compliance with international standards and compatibility with core-balance/residual CTs make it a versatile solution for modern power systems.