ABB 424K1105 Circuit Shield Sync Check Relay – Type 25S Synchronism Check

Application Scenarios:

A regional utility substation was experiencing nuisance trips and, on one occasion, mechanical stress on a 33kV bus tie breaker due to an improperly timed auto-reclose from a standby generator set. After investigation, the legacy timing relay lacked true phase-angle verification. The engineering team retrofitted the synchronizing scheme with the ABB 424K1105​ sync check relay. By connecting the PT secondary voltages from both sources to the 424K1105, the relay continuously compared voltage magnitude (adjustable ±% window), frequency deviation (±Hz), and phase angle difference (adjustable 0–30°). The relay only closed its output contacts—and thus permitted the breaker close coil—when all three conditions were satisfied simultaneously or, in the configured mode, when one side was detected as dead (dead-bus/dead-line permissive). This eliminated asynchronous closures, reduced contactor wear, and gave the operators confidence that auto-synchronization would only occur under safe electrical conditions.

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Technical Principles and Innovative Values:

• Innovation Point 1 — Solid-State Measuring with Electromechanical Reliability:​ The ABB 424K1105​ employs precision solid-state comparators to measure RMS voltage magnitude, frequency deviation, and phase-angle difference from the two PT inputs, while the output stage uses heavy-duty electromechanical contacts. This hybrid design gives accurate, drift-free synchronism detection with proven contact robustness for closing-coil circuits.
• Innovation Point 2 — Configurable Dead-Bus / Dead-Line Permissive Mode:​ Unique to the Type 25S variant of the 424K1105​ is the front-panel selector allowing sync-check-only, or permissive closing when either the line side or bus side is de-energized (within a settable undervoltage threshold). This eliminates the need for a separate undervoltage relay in many auto-changeover schemes.
• Innovation Point 3 — Wide Adjustment Ranges with Calibrated Controls:​ The ABB 424K1105​ provides clearly labeled, calibrated potentiometers or DIP switches for voltage match %, frequency deviation, phase-angle limit, and time delay—enabling field tuning to match specific generator characteristics or utility interconnection requirements without special tools or software.

Application Cases and Industry Value:

Case – Cogeneration Plant Generator Paralleling:​ A 6 MW natural gas cogeneration facility needed to parallel its generator with the utility grid under automatic control while meeting IEEE C37.94sync-check criteria. The ABB 424K1105​ was installed in the generator breaker control cubicle, wired across the generator and utility PT secondaries. During commissioning, the phase-angle window was set to ±15°, voltage match to ±5%, and frequency diff to ±0.2 Hz. Over three years of operation, the plant reported zero instances of out-of-sync closing during automatic synchronizing events. Maintenance staff appreciated the front-panel LEDs indicating “voltage OK,” “freq OK,” and “angle OK,” which accelerated troubleshooting during occasional utility disturbances. The ABB 424K1105​ delivered a low-cost, highly dependable synchronism check function that met both utility interconnection rules and internal safety standards.