Description
SEG XU2-AC Protection Relay | Multi-Voltage Monitoring Relay In-Stock
Dynamic Product Introduction
Operating critical power distribution panels or industrial generator sets without precise voltage supervision risks severe thermal damage and equipment failure caused by line voltage sags, phase loss, or unmitigated overvoltage spikes. The SEG XU2-AC serves as an industrial-grade AC voltage monitoring relay, delivering microprocessor-controlled overvoltage and undervoltage evaluation. Built into a compact, panel-friendly DIN-rail housing, it continuously measures incoming phase voltages against user-defined trip limits, driving dry output contacts to isolate loads or trip upstream circuit breakers before system degradation occurs.
When an active monitoring relay suffers power supply degradation, drift in potentiometer threshold calibration, or contact welding due to transient events, procuring an exact-fit SEG XU2-AC replacement unit keeps critical infrastructure operational. Installing a fully bench-tested replacement module allows control system engineers to clip a working relay directly onto existing 35mm DIN rails without redesigning terminal pinouts or modifying wire harness routing. Replacing a suspect relay restores precise voltage trip boundaries, rapid fault detection, and reliable system protection.
XU2-AC
Key Technical Specifications
- Model Designation: XU2-AC
- Manufacturer: SEG Electronics (formerly Woodward SEG)
- Measuring Input Nominal Voltage (U_n): Selectable 100 V AC, 110 V AC, 230 V AC, 400 V AC (phase-to-phase)
- Frequency Range (f_n): 35 Hz to 78 Hz
- Auxiliary Voltage Options: 19–55 V DC (Terminals A1/A2) or 36–520 V AC / 50–750 V DC (Terminals A1/A3)
- Protection Functions: Independent Overvoltage (U>) and Undervoltage (U<) thresholds with adjustable time delay (t)
- Parameter Setting Method: Front-panel DIP switches and rotary potentiometers
- Output Contacts: Heavy-duty changeover relay contacts (alarm & trip execution)
- Enclosure Mounting: 35mm standard DIN-rail / snap-on mounting
- Operating Temperature Range: -20°C to +60°C (-4°F to 140°F)
- Storage Temperature Range: -30°C to +70°C (-22°F to 158°F)
Global Sourcing & Live-Test SOP (Transparency Core)
Procuring secondary-market protection hardware like the SEG XU2-AC requires strict bench testing to verify potential transformer (PT) measuring inputs, potentiometer setting accuracy, and trip output relay contact resistance. Every incoming module passes through an intensive five-stage quality assurance protocol:
- Inbound Verification: Serial numbers, software revisions, and rating plates are cross-referenced with original SEG/Woodward manufacturing specifications. Technicians inspect the housing enclosure, terminal block screws, and front-panel setting potentiometers for physical wear or tampering.
- Live Simulation: The SEG XU2-AC is installed into a automated protection test bench powered by a precision AC voltage generator and variable DC auxiliary power supply.
- Diagnostics: Technicians inject secondary test voltages across the measuring terminals to verify pick-up (U>, U<) and drop-out levels against front-panel DIP switch settings. Oscilloscope-backed timing measurements verify that tripping delay times (t) execute within exact design tolerances. The relay then completes a thermal burn-in run under full auxiliary power to rule out component drift under heat.
- Final Prep: Rotary switches and DIP switches are reset to default neutral configurations, terminal screws are torque-verified, and the relay is sealed inside anti-static ESD packaging prior to dispatch.
The Field Engineer’s Pitfall Guide
- ❗ Incorrect Nominal Voltage (U_n) Selection: —though you might expect the relay to automatically sense the system voltage, failing to set the front DIP switches to match your specific line-to-line voltage (100V, 110V, 230V, or 400V AC) will result in false overvoltage or undervoltage trips immediately upon powering the circuit.
- ❗ Auxiliary Voltage Terminal Wiring Errors: Connecting low-voltage DC auxiliary power (19–55 VDC) to the high-voltage AC/DC terminal pair (A1-A3) will leave the unit unpowered, while applying high AC voltage to the low-voltage DC terminals (A1-A2) will permanently blow the internal auxiliary power supply board. Always check terminal labels carefully.
- ❗ Disregarding Potential Transformer (PT) Phase Rotation: While the relay monitors voltage amplitude, installing secondary sensing wires with floating ground reference connections can induce voltage offsets that cause unstable pickup behavior on three-phase systems. Ensure solid ground bonding and clean signal wiring.
Intent-Driven FAQ
What is the primary difference between the SEG XU2-AC and standard single-phase voltage monitoring relays?
The XU2-AC is a industrial-grade protection relay designed for utility, generator, and plant applications, supporting selectable system nominal voltages (up to 400V AC) with adjustable trip times and separate LED indications for overvoltage (U>) and undervoltage (U<) fault events.
Can the SEG XU2-AC be operated without an auxiliary power supply connected?
No. The XU2-AC relies on an independent auxiliary power source (connected across terminals A1/A2 or A1/A3) to power its internal microprocessor, measuring circuits, and trip relays. The voltage being monitored across the measuring terminals cannot power the unit directly.
How do I clear a latched trip LED on the front panel after a voltage fault resolves?
Once the measured line voltage returns to normal operating parameters within the hysteresis window, the unit automatically resets its internal output relays. The LED trip memory can be cleared according to the configured reset mode via the front panel or by cycling auxiliary power depending on parameter setup.
Why is the front-panel status LED flashing instead of remaining solid red?
A flashing LED indicates that the measured AC voltage has crossed the overvoltage (U>) or undervoltage (U<) pickup threshold and the internal trip delay timer (t) is actively counting down. If the fault persists until the timer expires, the LED switches to steady lit and the output contacts change state.
What warranty coverage comes with pre-inspected SEG XU2-AC replacement units?
All verified SEG XU2-AC protection relays come backed by a comprehensive 1-year replacement warranty. If the unit experiences auxiliary power supply failure, voltage sensing calibration drift, or contact relay failure under standard operating parameters within 12 months, it is swapped directly from available warehouse inventory stock.
