Buchholz Relays

Protecting Transformers from Internal Faults

Insulation liquid condition is critical to transformer reliability and network continuity. Buchholz relays are a proven, first line of protection for liquid‑filled transformers, providing early warning and automatic shutdown in the event of internal faults.

Insulect supplies COMEM Buchholz relays, designed to detect gas accumulation and abnormal oil flow, helping operators minimize the risk of catastrophic transformer failure and unplanned outages.

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Protecting Transformers from Internal Faults

Application Overview

Installed in the pipework between the transformer tank and conservator, the relay provides reliable detection of developing and severe internal faults throughout the transformer’s service life.

These solutions are suitable for:

Liquid‑filled power and distribution transformers, where early gas detection is critical
Hermetically sealed transformers, requiring compact and maintenance‑free protection
Conservator‑type transformers with rubber bladders, ensuring accurate gas and oil flow monitoring
Transformers with on‑load tap changers (OLTC), including dedicated relay versions for OLTC protection
Railway and traction transformers, exposed to vibration, shock, and dynamic loading
New installations and retrofit projects, with flexible mounting and configuration options
Challenging environments, including offshore, coastal, seismic, and tropical climates

What We Solve For

Internal electrical or thermal faults within a transformer generate gas and cause sudden oil movement. If undetected, these conditions can lead to severe damage or total transformer failure. COMEM Buchholz relays continuously monitor insulation oil, detecting both slow‑developing faults (through gas accumulation) and severe internal faults (through rapid oil flow). When predefined thresholds are reached, the relay triggers alarms or trips to protect the transformer and the wider power supply network.

Why buy COMEM Buchholz Relays

Proven technology used globally in critical transformer applications
Adjustable settings for alarms and trip functions
Easy installation across a wide range of transformer designs
Maintenance‑free design reduces lifecycle costs
Wide application coverage, including hermetically sealed and conservator‑type transformers
Backed by Insulect’s local expertise and technical support

TECHNICAL

Functionality & Options

Detection of gas accumulation caused by internal transformer faults
Monitoring of oil flow speed to detect severe internal events
Alarm and trip contacts for early warning and rapid system shutdown
Adjustable oil flow triggering values (typically 1.0 to 3.0 m/s, model dependent)
Versions with double flow flaps for separate alarm and trip functions
Testable alarm and trip contacts (available from ground level on selected models)
Optional gas sampling capability (GSD2 compatible)
Optional 4–20 mA analog output for gas accumulation monitoring
Optional MODBUS RTU (RS485) communication for digital monitoring
Corrosion protection options for offshore, coastal, and harsh environments

Key Technical Specifications

Standard compliance: IEC 60076‑22‑1
Installation: Indoor and outdoor, tropical‑proof design
Ambient temperature: –40 °C to +80 °C
Oil temperature: –40 °C to +120 °C (up to +140 °C or +200 °C with optional gasket materials)
Degree of protection: IP65 (IP66 available on request)
Nominal pipe diameters: DN25, DN50, DN80 or G 1½” threaded connection
Housing material: Aluminium casting, powder‑coated (ISO 12944 corrosion classes available)
Contacts: Potential‑free NO, NC or CO contacts (up to 6 switches total)
Nominal voltage: 24–230 VAC/DC
Seismic resistance: EN 60068‑3‑3, level II
Vibration classes: 4M4 and 4M6 (EN 60721‑3‑4)

IMPLEMENTATION

Services & Support

Insulect offers comprehensive services and support for the products we specialise in, enhancing value for local utilities, major energy users, equipment manufacturers, and service operators.

LOCAL TECHNICAL TEAM

Our local technical team provides exceptional support and expertise, ensuring quick response times and personalised service to tackle any challenges that may arise during project execution.

ENGINEERING EXPERTISE

Through COMEM, our team utilises advanced technology and industry knowledge to assist customers.

PROCUREMENT & LOGISTICS

We facilitate smooth procurement and logistics processes by sourcing from trusted, proven partners and coordinating timely deliveries, ensuring projects remain on schedule and within budget.