Beckwith M-3310 Transformer Protection Relay Complete Guide

Full analysis of engineering application of Beckwith M-3310 transformer comprehensive protection relay

In the field of transformer protection in power systems, traditional electromagnetic relays and early microcomputer devices face dual challenges of flexibility and reliability. The M-3310 transformer protection relay launched by Beckwith Electric is a fully digital multifunctional integrated protection system designed for various capacity dual winding transformers and some three winding applications. This device not only provides comprehensive differential, overcurrent, grounding fault and backup protection, but also has programmable input/output, multi fixed value group switching, waveform recording and multiple communication protocols, providing a one-stop protection solution for power plant step-up transformers, substation main transformers and industrial distribution transformers. This article is based on the M-3310 specification book, systematically sorting out its protection functions, hardware configuration, wiring definitions, parameter settings, and engineering application points, providing in-depth technical references for relay protection engineers.

Product positioning and system architecture

M-3310 is a standard 19 inch rack mounted (3U high) digital relay with a modular design that includes a motherboard, power board, optional M-3931 human-machine interface module (HMI), and M-3910 target indication module. Its core design concept is "highly integrated and flexible configuration", suitable for the following scenarios:

Main and backup protection for double winding power transformers (of any capacity);

Partial three winding transformer (configured with two sets of winding CT inputs);

Optional three-phase voltage protection package, realizing overexcitation, undervoltage, neutral point overvoltage and low-frequency protection;

Through external I/O expansion, achieve logic such as load shedding, rapid isolation of bus faults, and backup tripping of feeder switches.

The standard protected function library (corresponding to ANSI number) includes:

Negative sequence inverse time overcurrent (46)

Double winding double segment instantaneous phase overcurrent (50W1 # 1/# 2, 50W2 # 1/# 2)

Circuit breaker failure (50BF)

Transformer neutral point instantaneous/inverse time overcurrent (50G/51G)

Double winding inverse time overcurrent (51W1/51W2)

Residual inverse time overcurrent (51NW1/51NW2)

Dual winding phase to phase differential (87T) and high-value instantaneous differential (87H)

Grounding differential (87GD)

Six external functions (programmable delay exit)

Optional voltage protection package (to be ordered) added:

Overexcitation (24) V/Hz

Undervoltage (27) is used for load shedding

Neutral point overvoltage (59G)

Low frequency (81U)

Hardware structure and external wiring

2.1 Chassis and Power Supply

Physical dimensions: 19 "wide x 5.21" high x 10.20 "deep (approximately 48.3 x 13.2 x 25.9 cm), 3U high, can be installed horizontally or vertically.

Power input: You can choose 110/120/230/240V AC or 110/125/220/250V DC (UL range 85~265V AC/80~288V DC), or choose the 24/48V DC low voltage version. Power consumption is about 20VA. Optional redundant power supply (dual power module).

Power status indication: The PS1/PS2 LED on the front panel indicates that the power supply is normal, and the self-test status relay (normally closed) is closed after the device self-test is passed.

2.2 Analog input (see Figure 1 for terminal definitions)

Voltage input: 4-channel voltage (Va, Vb, Vc, Vn), rated at 60-140V AC, used for voltage protection package and differential voltage reference (such as V/Hz). Can be connected to phase voltage or line voltage.

Current input: 7 current inputs, corresponding to:

Winding 1 three-phase current (IA1, IB1, IC1)

Winding 2 three-phase current (IA2, IB2, IC2)

Neutral point/ground current (IG)

The CT rating can be selected as 5A or 1A (specified when ordering). Tolerance: 2 x In continuously, 100 x In for 1 second.

2.3 Control inputs and outputs

6 programmable digital inputs (terminals 5-10, common terminal 11): with 24V wet contacts inside, only dry contacts are allowed to be connected (external voltage is strictly prohibited). Can be configured as:

Block any protective function;

Trigger waveform recording;

Switch between fixed value groups (Profile 1-4);

Drive output relay;

Circuit breaker status (used to indicate the position of the circuit breaker).

8 programmable output relays: 1~6 are type A normally open contacts, and 7~8 are type C conversion contacts. Output 1-4 with high-speed drive circuit (about 4ms faster than 5-8). All contact ratings comply with IEEE C37.90, UL certification: 8A current carrying, 6A disconnect (120V AC), 0.1A disconnect (125V DC).

Self check alarm output: a normally closed contact (opens in case of power failure or self check failure).

Power status relay: normally open, closed when the power supply is normal.

Wiring precautions: Terminal blocks require # 22~12 AWG copper wire with a torque of 12 in lbs (terminals 1~34), and other terminals require 8~9 in lbs.

Detailed description and setting of core protection functions