Beckwith M-3311 Transformer Protection Relay Setting and Engineering Application

Additional starting value under fifth harmonic braking: 0.10~2.00PU;

CT tap compensation: 1.00~10.00 per winding (or 0.20~2.00 corresponding to 1A rated).

87H: Start value 5.0~20.0PU, delay 1~8160 cycles (minimum action time<1.5 cycles at 1 cycle).

Each braking component can be independently enabled/disabled or set to cross phase averaging to increase flexibility.

6. Grounding differential (87GDW2/87GDW3)

Used to detect grounding faults in winding 2 or winding 3, as a directional differential element, the directional element automatically exits when the zero sequence current is extremely small. The startup value is 0.2~10.00A, and the recommended delay is not less than 2 cycles. The CT transformation ratio correction coefficient is 0.1~7.99.

7. External functions (EXT # 1~# 6)

Provide 6 external input/output logic functions, which can trigger specified outputs after delay (1-65500 cycles) for any input contact (IN1-IN6) or output contact (OUT1-OUT8), and can be combined with BECO Logic to form complex interlocks. This function facilitates the integration of non electricity protection (such as gas, temperature) and the unified recording of target information.

Optional single-phase voltage protection package

For applications that require voltage, M-3311 provides an optional single-phase voltage input (only one channel), which can be connected to either phase voltage (for frequency, undervoltage, overexcitation) or open delta voltage (for ground overvoltage), but the two cannot be used simultaneously. Specific functions include:

Overexcitation protection (24 V/Hz): Based on the rated secondary voltage and frequency, provide 2 timed limit elements (starting value 100%~200%, delay 30~8160 cycles) and 1 inverse time limit element (starting value 100%~150%, multiple curves to choose from). 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, a delay of 1-8160 cycles, and a suppression voltage (to prevent PT disconnection and misoperation).

Grounding overvoltage (59G): Only available when the voltage input is connected to the open delta VT, providing 2 components with a starting value of 5-180V and a delay of 1-8160 cycles.

Frequency protection (81O/U): 4 components each for overclocking and low-frequency, with a setting range of 45-65Hz (45-55Hz for 50Hz models), a delay of 2-65500 cycles, and an accuracy of ± 0.1Hz (57-63Hz for 60Hz models).

Attention: When selecting phase voltage input, 59G is not available; When selecting an open triangle, 24, 27, and 81 are not available and need to be balanced based on the actual main wiring.

Standard hardware and communication interface

1. Input/output configuration

Control/status inputs: 6 (INPUT1~6), internal wet connection 24Vdc, minimum excitation current>25mA. INPUT1 is dedicated to connecting the auxiliary contacts of circuit breaker 56a to provide circuit breaker status LED indication. There is also an independent input used to monitor the integrity of the trip circuit (expected to be supported in the future).

Programmable outputs: 8 (OUTPUT1~8), of which 1-6 are A-type normally open contacts and 7-8 are C-type conversion contacts; There is also a power failure alarm output (type B) and a self-test alarm output (type C). All output contacts are rated in accordance with IEEE C37.90 (specific parameters see below).

Output contacts 1-4 have high-speed operation characteristics, about 4ms faster than 5-8, suitable for fast tripping circuits.

2. Communication port

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

One IRIG-B port (BNC) for time synchronization (supporting modulation or demodulation);

Supports MODBUS, BECO 2200, and DNP 3.0 protocols, and with M-3820B IPScom software, it can achieve constant value reading and writing, real-time measurement, event extraction, and waveform download.

3. Measurement and recording

Real time measurement: voltage, three-phase current, neutral point current, frequency, and positive/negative/zero sequence components; Can record the required current and maximum value (with time stamp) for 15/30/60 minutes.

Accuracy: Voltage ± 0.5V or ± 0.5%; Current (5A rated) ± 0.1A or ± 3%; Frequency ± 0.1Hz.

Oscillatory recording: The sampling rate is 16 times the system frequency, and the total recording length can be configured with 1-4 partitions, with a maximum storage capacity of 152 cycles of data. The triggering methods include status input, trip output, or communication command. The recorded data can be analyzed or exported as COMTRADE using IPSlot Plus.

Target storage: It can store 32 recent tripping events, including action components, current values, time scales, and I/O states.

Circuit breaker monitoring: Estimate the wear of each phase contact by integrating I ² t or It, and trigger an alarm or trip when the cumulative value exceeds the user threshold. The timing needs to be triggered by an external starting contact.

4. Optional hardware modules

M-3931 HMI module: Provides a 2-line x 24 character LCD and a 6-key keyboard, supporting on-site fixed value viewing, modification, event retrieval, and measurement display, with three-level password protection.