ABB-SPAD346C3 Biased Differential Protection Relay

Description

Core performance characteristics

SPAD346C3 is panel‑mounted protection relay belonging to ABB SPAD series. It accepts 1 A or 5 A secondary current input from current transformers. Wide auxiliary power supply 110‑240 V AC/DC, typical power consumption below 5 W. Dual‑slope biased differential characteristic prevents false tripping caused by CT saturation during external through‑faults. Second‑harmonic and fifth‑harmonic restraint algorithm suppress transformer inrush current mis‑operation. Trip operating time can be adjusted within 20‑200 ms range. Front‑panel LED indicators display power status, trip action and IRF internal hardware fault. Built‑in disturbance recorder stores fault waveform data in COMTRADE format, downloadable via local service port. Supports manual / automatic fault reset mode. Continuous self‑supervision runs every 100 ms, detecting power supply abnormality, input circuit failure and internal chip anomaly. Panel‑mount installation, front‑side IP40 protection level, rear terminal area IP20. Operating ambient temperature‑20 ℃ ~ +55 ℃, satisfies IEC anti‑vibration and EMC immunity requirements for substation equipment.

Field usage conditions

Mainly installed in power plant and industrial substation medium‑voltage protection cabinets. It serves as main differential protection for two‑winding / three‑winding power transformers, large‑capacity generators and high‑voltage motors. When internal winding short‑circuit or turn‑to‑turn fault occurs inside protected equipment, it sends fast trip signal to open circuit‑breaker, limiting equipment damage. Harmonic restraint function guarantees stable performance during transformer energizing switching‑on. Common spare‑part for renovation and overhaul of old‑type power‑plant protection systems. It can cooperate with additional over‑current and earth‑fault modules to form complete bay protection configuration.

Practical deployment considerations

All CT secondary wiring work must be finished under de‑energized condition. Never open CT secondary loop while primary circuit is live, otherwise dangerous high‑induction voltage will appear. CT accuracy shall comply with specification, 5P‑class CT is recommended for differential protection loop. CT ratio correction, differential starting current and biased slope parameters must be calculated and set strictly according to protected equipment parameterseero. Panel cut‑out dimension shall follow official mechanical drawing. Keep distance from heating components inside cabinet. Use shielded twisted‑pair cable for CT signal wiring, single‑end grounding for shielding layer. Back‑up setting parameters before replacement. After hardware swap, complete parameter download and protection function simulation test with relay tester before putting into real service. On‑site component‑level repair is forbidden. When persistent IRF hardware alarm appears, replace the whole relay unit directly.

Typical on‑site symptoms & handling ideas

1. Power‑on with auxiliary LED off: Check AC/DC auxiliary power supply and fuse. Inspect rear screw terminals for loose contact. If input power is normal, internal hardware failure of relay shall be judged.
2. Protection false tripping during transformer switching‑on: Verify second‑harmonic restraint setting value. Inspect CT wiring polarity and connection correctness. Check whether CT circuit has loose or poor‑contact points.
3. Refuse to trip under simulated internal fault: Re‑check differential starting value and biased‑slope configuration. Confirm CT secondary circuit is not open‑circuited or short‑circuited. Inspect trip‑relay output contact loop.
4. IRF fault alarm keeps active: Read fault code displayed on front panel. Check auxiliary power fluctuation. Eliminate external circuit fault; replace whole relay if internal permanent defect is confirmed.
5. Disturbance record cannot be downloaded: Check local service communication cable. Confirm relay is not under hardware‑lock state. Verify PC configuration tool version compatibility.
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