أنظمة حفظ الزيت بالخزان التمددي ومرحلات بوخهولز وتشخيص مثلث دوفال DGA

حفظ الزيت بغشاء مطاطي، وآليات تراكم الغاز والفصل عند اندفاع الزيت في مرحل بوخهولز ذي العوامتين، وتشخيص تحليل الغازات الذائبة (DGA) وفق IEC 60599.

1. Oil Preservation Architecture in Conservator Tanks

In breathing power transformers, the oil expansion tank is equipped with an atmospheric isolation rubber membrane (diaphragm) and silica gel breather to eliminate ambient moisture ingress.

2. Buchholz Relay Dual-Float Operation (DIN EN 50216-2)

The Buchholz relay is mounted on the connecting pipe sloped at 2° - 4° between main tank and conservator:

Trigger MechanismPhysical ThresholdOperational ActionFault Type Detected
Upper Float Gas Volume200 - 300 cm3 accumulated gasAlarm Contact ClosesSlow incipient faults, local overheating, PD
Lower Surge FlapOil velocity > 1.0 - 1.5 m/sInstantaneous Breaker TripSevere short-circuit, high-energy arcing, phase fault

3. Dissolved Gas Analysis (DGA) Duval Triangle 1 Diagnostics

Per IEC 60599, fault diagnosis uses relative percentages of Methane (CH4), Ethylene (C2H4), and Acetylene (C2H2):

%CH4 = (CH4) / (CH4 + C2H4 + C2H2) × 100
%C2H4 = (C2H4) / (CH4 + C2H4 + C2H2) × 100
%C2H2 = (C2H2) / (CH4 + C2H4 + C2H2) × 100

Fault Classifications:

  • PD (Partial Discharge): Predominantly Hydrogen (H2) and Methane.
  • T1 / T2 / T3 (Thermal Faults <300°C to >700°C): Dominated by Ethylene (C2H4) and Ethane (C2H6).
  • D1 / D2 (Low / High Energy Electrical Discharges): Identified by elevated Acetylene (C2H2 > 5 ppm).

4. Field Sampling Best Practices

DGA oil samples must be drawn using airtight gas-tight glass syringes without air bubbles per IEC 60567.

*Reference: IEC 60599:2015; IEEE Std C57.104-2019; DIN EN 50216-2.*