Reliable Double-Float Buchholz Relay for Efficient Transformer Operations

• Customization: Available
• Theory: Electromagnetic Relay
• Usage: Transformer
• Model NO.: QJ series
• Phase: 1
• Electricity Type: Ac
• Number of Pole: 8
• Load: High Power Relay
• Protective Characteristics: Open Relay
• Action Principle: Electromagnetic Type
• Size: Subminiature
• Type: Electric Parameter Relay
• Transport Package: Wooden
• Trademark: E-Cloud
• Origin: Beijing, China
• HS Code: 8536490090
• Production Capacity: 1000

Product Description

Product Description

Double float type gas relay is a safety protection device for oil-immersed transformers. The gas relay is installed on the connecting pipe between the transformer oil tank cover and the oil storage cabinet. It can be equipped with a gas guide pipe and a gas box to realize ground exhaust sampling. When a fault occurs inside the transformer and causes the insulating liquid to decompose and produce gas or cause oil flow to surge, the contacts of the gas relay will operate and connect the specified circuit, thereby sending out electrical signals in time or automatically cutting off the power equipment; when the transformer leaks or accumulates a large amount of unknown gas and causes the liquid level in the gas relay to continue to drop, the lower float drives the contacts to operate and sends out an alarm or trip command in time to further protect the safe operation of the transformer.

Usage Conditions

Working temperature: -40ºC~120ºC;
Installation method: The axis of the relay pipeline should be parallel to the transformer oil tank cover, and the end leading to the oil storage cabinet is allowed to be slightly higher, but the inclination angle of its axis to the horizontal plane shall not exceed 4%.

 

Product Parameters

Model Series	QJ Series
Type	Double-Float Gas Relay (Buchholz Relay)
Application	Oil-immersed transformers
Operating Temperature Range	-40°C to +120°C
Installation Angle	≤4° relative to horizontal
Contact Capacity	AC 220V/0.3A, DC 220V/0.3A
Power Factor	≤0.6
Contact Resistance	≤5×10^-³Ω
Insulation Resistance	≥100MΩ at 25°C
Dielectric Strength	≥2kV between contacts and ground
Signal Outputs	Light gas alarm, heavy gas trip
Models	QJ20-80, QJ22-80, QJ23-80, QJ31-80, QJ32-80, QJ33-80, QJ43-80
Pole Count	8, 10, 12
Connection Diagrams	Diagram 1-7
Overall Size	Compact design
Pipe Diameter	Ø80mm
Gas Pipe Length	9m

Key Product Parameters

Parameter	Specification
Model Number	QJ23-80A-8 (Example)
Float Type	Double float (upper + lower)
Alarm Trigger	Upper float: Gas accumulation (slow)
Trip Trigger	Lower float: Oil surge (rapid flow)
Pipe Diameter	Φ80mm (standard), other sizes optional
Gas Sampling	Built-in gas vent & sampling box
Operating Temp.	-40°C to +120°C
Tilt Angle Limit	≤4° (for proper installation)
Enclosure Rating	IP55 (dust/water-resistant)
Standards	IEC 60076-2, GB/T 7252

 

FAQ

Q1: How does the double float mechanism work?

A:

• Upper float: Triggers alarm for slow gas buildup (e.g., partial discharge).

• Lower float: Triggers trip for rapid oil flow (e.g., internal short circuit).

Q2: What does "QJ23-80A-8" mean in the model number?

A:

• QJ23: 23rd design iteration.

• 80: Pipe diameter (Φ80mm).

• A: Dual alarm outputs.

• 8: 8-meter guide pipe length (with gas sampling box).

Q3: Can this relay detect all fault types?

A: Yes! It identifies:

• Thermal faults (overheating → gas).

• Electrical faults (arcing → oil surge).

• Insulation degradation (gas composition changes).

Q4: How to install the relay correctly?

A:

1. Align the relay pipe parallel to the transformer cover.

2. Tilt slightly (≤4°) toward the conservator.

3. Ensure gas vent pipes are unobstructed.

Q5: Is the gas sampling box necessary?

A: Recommended! It allows:

• On-site gas collection for lab analysis.

• Fault type verification (e.g., H₂vs. C₂H₂ ratios).

Q6: What maintenance is required?

A:

• Annual inspection: Check float movement and contacts.

• 5-year calibration: Verify gas/oil flow thresholds.