INDUSTRY COMPONENT

Grading Rings/Capacitors

Grading rings and capacitors are critical components in high-voltage bushings that manage electric field distribution and prevent insulation breakdown.

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Component Specifications

Definition
Grading rings (also called corona rings) are metallic rings installed at strategic points on high-voltage bushings to control and equalize electric field gradients, reducing corona discharge and preventing insulation failure. Capacitors in this context refer to capacitive grading elements embedded within bushing insulation to create uniform voltage distribution along the bushing length. Together, these components ensure reliable operation of high-voltage equipment by managing electrostatic stress.
Working Principle
Grading rings work by providing a smooth conductive surface that redistributes electric field lines, preventing concentration at sharp edges. Capacitive grading uses series-connected capacitor layers within the bushing insulation to create a controlled capacitive voltage divider, ensuring linear voltage drop along the bushing axis. This combination prevents partial discharges, reduces thermal stress, and maintains dielectric integrity under high-voltage conditions.
Materials
Grading rings: Aluminum alloy (typically 6061-T6) or copper with corrosion-resistant coating. Capacitor elements: Aluminum foil electrodes with kraft paper or polypropylene film dielectric, impregnated with mineral oil or synthetic ester fluid. Insulation: Porcelain or composite polymer housing.
Technical Parameters
  • Frequency 50/60 Hz
  • Voltage Rating 72.5 kV to 1200 kV
  • Creepage Distance 25-35 mm/kV depending on pollution class
  • Temperature Range -40°C to +105°C
  • Capacitance Tolerance ±5%
  • Partial Discharge Level <5 pC at 1.5x rated voltage
Standards
IEC 60137, IEEE C57.19.00, DIN 42523

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Grading Rings/Capacitors.

high-voltage bushing grading ring corona ring capacitive grading insulation components electric field control transformer bushings IEC 60137 Grading Rings/Capacitors Grading Rings/Capacitors in Electrical Equipment Manufacturing

Parent Products

This component is used in the following industrial products

High-Voltage Bushings

Insulating components that allow high-voltage conductors to pass safely through grounded barriers in test chambers

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Engineering Analysis

Risks & Mitigation
  • Corona discharge leading to insulation degradation
  • Moisture ingress causing capacitance changes
  • Thermal cycling stress on connections
  • Pollution accumulation reducing creepage distance
FMEA Triads
Trigger: Corrosion of grading ring surfaces
Failure: Increased corona discharge and eventual insulation breakdown
Mitigation: Use corrosion-resistant coatings and regular cleaning; implement cathodic protection where applicable
Trigger: Dielectric aging in capacitor elements
Failure: Capacitance drift leading to uneven voltage distribution
Mitigation: Regular capacitance measurements; use thermally stable dielectric materials; monitor partial discharge activity

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
Capacitance: ±5%; Dimensions: ±2mm; Surface finish: Ra ≤ 3.2μm
Test Method
Capacitance measurement at 1kV, 50Hz; Partial discharge test per IEC 60270; Power factor test; Visual and dimensional inspection

Procurement Evaluation Criteria

Not customer reviews or live demand data. These dimensions support RFQ preparation and supplier evaluation.

Technical documentation
4/5
Manufacturing capability
4/5
Inspection readiness
5/5
Supplier transparency
3/5

These scores are example evaluation dimensions, not real customer ratings, country-specific buyer feedback, or live inquiry activity.

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Frequently Asked Questions

What is the difference between grading rings and capacitors in high-voltage bushings?

Grading rings are external metallic rings that control surface electric fields, while capacitors are internal elements that create uniform voltage distribution through capacitive grading. Both work together to prevent insulation failure.

How often should grading rings be inspected?

Visual inspections should be conducted annually, with detailed electrical testing every 3-5 years or after severe weather events. Look for corrosion, contamination, or physical damage.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

Data Basis

CNFX manufacturer profiles, technical classification, publicly available product information, and ongoing plausibility checks.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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