Beckwith M‑3311 Transformer Protection Relay

The Beckwith M‑3311 is a solid‑state transformer protection relay engineered to provide comprehensive protection for power transformers and associated equipment. This model, identified by catalog number 7113, incorporates differential protection, overcurrent backup, and thermal monitoring in a single compact unit. It is designed to detect internal faults such as phase‑to‑phase and ground faults, as well as external overload conditions, ensuring rapid isolation to minimize damage.

The relay features adjustable pickup settings, multiple time‑current characteristics, and a high‑burden capability that accommodates various CT ratios. Its rugged construction and panel‑mount design make it suitable for both utility substations and industrial power systems.

Key Features

• Differential protection with percentage restraint

• Backup overcurrent protection (phase and ground)

• Adjustable pickup: 10–50% of CT secondary

• Stabilising resistor for through‑fault stability

• Independent time delay settings

• Target indicator for fault identification

• Operating temperature: -10°C to +55°C

Technical Specifications

CT inputs: 1A or 5A; frequency: 50/60 Hz; pickup accuracy: ±2%; output contacts: 2 x SPDT, 5 A at 250 VAC; power supply: 125 VDC or 120/240 VAC; dimensions: standard panel mount case.

Applications

Ideal for protecting two‑winding and three‑winding power transformers, generator step‑up transformers, and industrial furnace transformers. The M‑3311 provides primary protection against internal winding faults.

Installation and Settings

Mount the relay on a standard panel. Connect CTs from both high‑voltage and low‑voltage sides. Configure the differential pickup, restraint slope, and time delays using the front‑panel controls. A test plug is provided for commissioning.

Reliability and Maintenance

The solid‑state design ensures long‑term stability and immunity to mechanical wear. Periodic testing with secondary injection is recommended to verify accuracy.

Why Choose the M‑3311?

This relay offers proven reliability and simple settings, making it a trusted choice for transformer protection in demanding environments. Beckwith Electric’s engineering excellence ensures dependable operation.

In summary, the Beckwith M‑3311 delivers robust transformer protection, safeguarding valuable assets from electrical faults.