Beckwith M-3311A Transformer Protection Relay Configuration and Optimization Guide

Turning point: 1.0~4.0PU;

Second harmonic braking (2nd, 4th): 5%~50%, used to suppress excitation inrush current;

Fifth harmonic braking: 5%~50%, used for overexcitation suppression.

The high setting differential component 87H has a starting value of 5.0~20.0PU and an action time of less than 1.5 cycles (with a minimum delay of 1 cycle). CT ratio compensation can be achieved by setting the CT tap of each winding (1.00~100.00).

6. Grounding differential protection (87GD)

Suitable for ground fault detection of various windings, configurable as directional or non directional. The starting value is 0.2~10.00A, and the delay is 1~8160 cycles (recommended not less than 2 cycles). The zero sequence current source can be selected as the sum value or a single winding. The directional component automatically exits when the zero sequence current is extremely small.

7. IPSpeegic Programmable Logic

Provide Boolean logic combinations (AND, OR, NOT) based on component actions, control input states, output contact feedback, and other conditions, combined with timers (delay 0-65500 cycles), to construct complex interlocking and automatic switching schemes.

Optional voltage protection package

For applications that require voltage, M-3311A provides an optional voltage protection package that includes the following functions:

Overexcitation protection (24 V/Hz): using fixed time limit (starting value 100%~200%, delay 30~8160 cycles) and inverse time limit (starting value 100%~150%, multiple inverse time limit curves) components to prevent damage to transformers and generators due to overcurrent. Based on the rated secondary voltage and system frequency calculation, the accuracy is suitable for the range of 10~80Hz and 0~180V.

Undervoltage (27): Used for load shedding, with a starting value of 5-140V and a delay of 1-8160 cycles, and can be set to suppress voltage values. Provide 3 components in three winding applications and 2 components in four winding applications.

Phase overvoltage (59): 1-3 components, starting value 5-180V, can choose phase voltage, positive sequence or negative sequence components.

Grounding Overvoltage (59G): Used to detect system grounding faults, with a starting value of 5-180V. The zero sequence voltage can be taken from the VG input (open delta) or calculated as 3V0 (requiring four voltage inputs and VT configuration as LG).

Frequency protection (81O/U): 4 components each for overclocking and low-frequency, with a setting range of 45-65Hz, a delay of 2-65500 cycles, and an accuracy of ± 0.1Hz (60Hz models are within the range of 57-63Hz).

Standard hardware features and communication functions

1. Input and output

Standard I/O: 8 programmable output contacts (6 type A, 2 type C) and 6 control/status inputs (internal wet connection 24V, minimum excitation current ≥ 25mA). There is also a power failure alarm output (type B) and a self-test alarm output (type C).

Expansion I/O (optional): Add 8 A-type outputs and 12 inputs, and provide closing circuit monitoring (CCM), suitable for situations that require more switch signals.

2. Communication interface

Three serial ports: two RS-232 (one front and one back) and one RS-485.

Optional RJ-45 Ethernet port (10/100 Base-T), supporting MODBUS TCP/IP, DNP 3.0 over TCP/IP, or IEC 61850 protocol (up to 4 concurrent sessions).

Support IRIG-B time synchronization (modulation or demodulation) for precise timing of events.

Supports MODBUS and DNP 3.0 serial protocols, compatible with S-3300 IPScom ® Communication software that can perform fixed value reading and writing, real-time monitoring, waveform downloading, and other operations.

3. Recording and monitoring functions

Oscillatory waveform recording: The sampling rate is 16 times the system frequency, and the maximum storage capacity is 183-311 cycles (depending on the number of windings and partitions). The triggering method can be selected as state input, trip output, or communication command. The recorded data can be analyzed using IPSplot Plus software or exported in COMTRADE format.

Sequence of Events (SOE): Stores the last 512 events with time stamps.

Through Fault: Independently record through faults, store the duration of each fault, maximum fault current of each phase, I ² t value, and cumulative number of times (up to 256).

Target storage: Store the information of the last 8 trips, including the operating components, current values, and time scales.

Circuit breaker monitoring: Estimate the wear of each phase contact by integrating I ² t or It, and the cumulative value can set an alarm threshold (0-50000 kA · cycle), which needs to be triggered by the starting contact for timing.

Configuration options and typical application wiring

M-3311A supports multiple hardware configuration combinations to meet different main wiring methods:

Number of windings, grounding current, input voltage

2 1 0 / 2 / 4

3 2 0 / 2 / 4

4 3 0/2 (only two voltages)

For the four winding model, the two voltage inputs are phase voltage (for 59, 81, 27, 24) and open delta voltage (for 59G), and are independent of the winding.

Typical application wiring diagrams include:

Double winding transformer (Figure 3): Clearly displays the signal flow of CT connection, differential, overcurrent, and grounding protection for each winding.