NGR Panel
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NGR Panel
Description
A Neutral Grounding Resistor (NGR) panel is a critical electrical safety enclosure used to protect industrial power systems from phase‑to‑ground faults. By connecting a specific resistance between the neutral point of a transformer or generator and earth ground, it limits transient fault currents to a safe, predetermined value
Core Technical Specifications
System Voltage: 415V to 33KV
Fault Current Rating: 10Α to 3000A
Time Duration Seconds: Continuous, 10 Seconds or 30
Ingress Protection: IP 33 TO IP 55 (indor Or Outdoor
Resistor Material: Stainless Steel (SS304, SS310, or SS430)
Key Internal Components
A standard NGR panel integrates several components within a single ventilated enclosure꞉
• Resistor Elements꞉ Grid or punched stainless steel banks designed to withstand massive thermal shock.
• Neutral Isolator Switch (NIS)꞉ Allows manual isolation of the neutral path for safe maintenance.
• Current Transformer (CT)꞉ Measures leakage current to trigger downstream protection relays.
• Space Heater꞉ Thermostatically controlled element to prevent internal condensation and corrosion.
• Support Insulators꞉ High‑dielectric porcelain or epoxy insulators rated for the system voltage.
Primary Working Functions
1. Limits Fault Current꞉ Caps explosive ground‑fault currents to prevent catastrophic equipment destruction.
2. Reduces Transient Over‑voltages꞉ Dampens destructive resonant voltages during arcing ground faults.
3. Ensures Personnel Safety꞉ Lowers step and touch potentials near the faulted machinery.
4. Enables Selective Fault Clearing꞉ Provides enough current for monitoring relays to pinpoint and isolate the exact fault location
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