nlm3 Neutral Earth RELAY

PRODUCT OVERVIEW

Legacy-generation NER integrity protection built on proven 2000-era Bramco technology

NLM3 Neutral Link Monitor provides legacy-generation NER integrity protection for mining and industrial power systems.

Engineered using proven Bramco technology developed in the early 2000s, NLM3 continuously monitors the resistance grounded neutral point of a supply transformer and provides protection against NER failure, excess phase voltage rise, and  neutral-earth leakage current.

APPLICATION

Our NLM3 is compliant with key statutory and industry standards and is designed to:

• Monitor the current-limiting system between transformer star-point and earth

• Detect NER resistance faults (open, short, drift)

• Detect excessive neutral-earth voltage rise

• Detect neutral-earth leakage current

• Monitor direct earth connection systems

• Provide individually adjustable protection timers for coordination

It is suitable for:

• Mining distribution systems

• Underground and surface substations

• HRG/LRG systems with NER

• Industrial plants with resistance-grounded systems

FEATURES

• Connects directly to AC supply systems up to 1100 V — no barrier required

• Compatible with systems up to 4160 V (with external barrier assembly)

• Monitors NER resistance integrity

• Monitors excess phase-voltage rise

• Monitors neutral-earth leakage current via external EL toroid (toroid not included)

• LED indication for:

– Power On

– NER Integrity

– Excess Voltage

– Earth Leakage

• Unit configured as fail-safe with latch-on-fault

• Backup protection via voltage-rise detection across the NER

• Individually adjustable trip delay times for:

– Earth leakage

– NER integrity

– Over-voltage

• Adjustable earth leakage current trip

• Adjustable excess voltage trip

• Adjustable NER resistance limits

• Selectable earth leakage frequency response: 50–60 Hz or 5–100 Hz • Open-circuit toroid protection

• Reset push-button input

• Timestamped event log

• Password protection for parameter setting

SPECIFICATIONS

Supply

Power: 4 VA ±20%

Operating Temperature: 0–60°C

Communications

• RS-485 serial port, Modbus ASCII / RTU

(Hardware present — RS-485 not implemented)

Instrumentation Output

• 4–20 mA or 2–10 V

NER Resistance Values

• NER 10–650 Ω depending on system voltage and limiting current • Consult m-tronix for system-specific requirements

EL System Voltages

• 415 / 1100 V

• 240 / 635 V phase

NER Trip Value Adjustment

• 50% to +100% (as required by AS/NZS 2081:2011)

Trip Tolerance

• +10% / 0%

Earth Leakage Current Range

• 30–500 mA

Trip Delay Timer

• 50–500 ms for over-voltage & earth leakage

• 2–10 s for NER integrity

Excess Voltage Trip

• Adjustable from 5–50% of phase voltage

Relay Contacts

• 2 × changeover, 5 A @ 250 V AC (100 VA max) — earth leakage • 2 × changeover, 5 A @ 250 V AC (100 VA max) — over-voltage & NER integrity

ENCLOSURE

Dimensions: 150 mm (W) × 75 mm (H) × 110 mm (D)

Material:

• High-impact polycarbonate construction

• IP20 rating

Mounting: DIN rail

Terminals: Cage screw terminals

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m-tronix Pty Ltd

info@m-tronix.com.au | +61 435 939 513 | www.m-tronix.com.au