Supplier High-voltage Neutral Grounding Resistors (MRD-BJ-NGRs):
generator switch box
generator switch box
Standards Carried Out:
DL/780-2001 Neutral Grounding Resistance in Power Distribution
GB6450 Dry-Type Power Transformer
DL/T620-1997 Overvoltage Protection and Insulation Co-ordination of AC Electrical Equipments
GB/T16927-1997 Experimental Technique of High Voltage
GB1208-1997 Current Transformer
GB4208-93 Shell Protection Grade (IP code)
IEEE32-1972 Standard Technique, Terms and Experiment of Neutral Grounding Device
GB311.1-1997 Insulation Co-ordination of Transmissional and Distributed Device of High Voltage.
DL/T593-1996 Common Specifications for Purchasing High Voltage Switch Equipment.
GB50150-1991 Electrical Equipment’s Hand-over and Test Standard of Electrical Device Installation Project.
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FUNCTION
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Neutral Grounding Resistors are used to protect power transformers, power generators and other associated equipment in your power systems against 50/60 Hz faults (short circuit) and transient phenomena (lightning).
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SPECIFICATIONS
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There are six parameters needed to specify the neutral grounding resistor.
1. Rated voltage line to neutral or system voltage.
2. Rated fault current.
3. Rated “duration time” of the line to neutral voltage not exceeding the allowable temperature rise.
4. Rated Resistance.
5. Application environment, indoor or outdoor.
6. Enclosure material, ss plate or normal cold rolled sheet.
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TESTING AND QUALITY
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with IEEE-32. Routine tests performed on each Neutral Grounding Resistor are measurement of resistance, high voltage power frequency, insulation measurement, aspect verification, dimensional control. Mingrui’s internal quality system has been developed and certified under ISO 9001 quality system
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CONSTRUCTION
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Standard unit includes the stainless steel resistor assembly plus all the required insulators, internal connections and hardware installed in a standard safety enclosure. Neutral Grounding Resistor units are completely assembled, prewired, and tested at our facility. For shipping all units are crated for added protection and ease of handling.
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ENCLOSURE FEATURES
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• Forged eyebolts in all four corners for easy hoisting.
• Removable front and rear louvered covers for easy access for connection and inspection.
• Corrosion resistant nameplate provides complete ratings and manufacturers information.
•Heavy gauged enclosure polyester powder coated finish provides maximum protection.
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ENCLOSURE OPTIONS
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•Stainless steel, cold rolled plate construction. Custom paint finish is available.
• Top or side mounted entrance bushing(s). • Screened covers for indoor applications. • Support stands for elevating the enclosure above ground. |
Parameters of Grounding Transformer
Insulation Grade: H
Cooling-down Method: AN
Temperature Rise ≤ 100K
Proctective Grade of paper insulation dry-type connected transformer is IP00 (without casing), IP20 and ip23 (with casing)
Insulation level, impedance voltage, no-load loss and on-load loss are as per National Standards.
Test of inpedance: high voltage to low voltage or grouding ≥300 MΩ, low voltage to grounding ≥100 100 MΩ
Order Notes
1. system rated voltage
2.short-time withstand current;
3. normal resistance;
4. with current transformer or not; transformation ratio, capacity and compound deviation of the current transformer;
5. method of wiring (optional): a. wire in from the top, and out at the bottom, b. wire in and out from the bottom, c. wire in and out from the side, d. wire in from the side and out at the bottom;
6. durable time for short-time withstand current;
7. material of resistance cabinet, protection grade of (IP), color code and installation site of the resistor cabinet;
8. with earthing record and temperature and humidity control equipment or not