Beckwith M-3425A Relay Guide

Rated voltage: VT secondary side rated line line voltage (50-140V)

Rated current: CT secondary side rated value (1A or 5A)

VT configuration: line to line/line to ground/line to ground conversion line to line

Delta-Y Transformer: If the generator is connected to the system through a Δ/Y transformer, Delta-AB or Delta-AC should be selected for the relay to automatically compensate for a 30 ° phase shift.

Phase sequence: ABC or ACB

59/27 amplitude calculation method: RMS (frequency range 10-80Hz, slightly lower accuracy) or DFT (only fundamental frequency, high accuracy)

CT/PT ratio: primary value/secondary value

3.3 Protection Function Configuration

In "Relay/Setup/Replay Setpoints", set them one by one according to the function number:

Enable/Disable: Check according to the purchasing options

Output contact allocation: Select the output relay (OUT1~OUT8/OUT9~OUT23) that closes when the function is activated

Locking input: Select which input contacts can lock the function (such as circuit breaker position, external locking signal)

Setting value: Input according to the generator nameplate, capacity curve, and system coordination requirements

Example of typical function settings:

87 phase differential

Minimum operating current: 0.2-3.0A (usually 0.3A)

Slope: 1-100% (usually 10%)

Time delay: 1-8160 cycles (usually 1 cycle)

40 demagnetization protection

Two M-O circles: circle 1 diameter=X'd (transient reactance), offset=- X'd/2; Circle 2 diameter=Xd (synchronous reactance), offset=- X'd/2

Delay: Short delay for circle 1 (e.g. 15 cycles), long delay for circle 2 (e.g. 3600 cycles), with the option to add undervoltage acceleration

78 step loss protection

Muo circle diameter, offset, impedance angle, blind plate impedance

Out of step delay, sliding pole count (usually once)

Optional 'trip when the M-O circle exits' to obtain a more favorable trip angle

64S 100% stator grounding (low-frequency injection)

An external 20Hz signal source, bandpass filter, and dedicated CT are required. Settings:

Total current starting value (2-75mA)

Real current starting value (2-75mA)

Delay (cycles)

Optional voltage braking and low-frequency locking

3.4 Fixed value group (Profile)

The relay supports 4 sets of fixed values, which can be switched manually, through input contacts, or through IPSigmic. The relay will temporarily lock for about 1 second when switching. During debugging, you can first configure a set of "online" settings, copy them to another set, and then modify them to "maintenance" settings.

Common troubleshooting

The following is a summary of common fault phenomena and countermeasures based on Chapter 7 of the manual.

4.1 Excitation Control Issues (FCR Mode)

Possible causes investigation and handling of phenomena

No excitation current output excitation not enabled, wiring error, PMG power supply missing inspection software excitation enabled and external excitation enabled input (EX-D+); Check the excitation output circuit; Measure PMG input voltage

If the excitation output is lower than the set value FCR and not selected, the gain is incorrect, and the magnetic field resistance is too high, confirm that AVR-FCR_Select=1; Check the gain; Disconnect the excitation output to measure the magnetic field resistance, which should be within the specification range

Unstable excitation, improper gain, wiring interference, and recalibration of PID; Check the shielding grounding

4.2 Voltage regulation issues (AVR mode)

Possible causes investigation and handling of phenomena

Non excited output is the same as FCR -

Voltage below set value AVR not selected, insufficient power supply voltage, generator speed not reaching rated, droop compensation driving voltage reduced, OEL limiter action confirmed AVR-FCR_Select=0; Check the PMG voltage; Increase the rotational speed; Check if the droop is mistakenly activated; View OEL-Active bit

Voltage above set value AVR not selected, gain too high, UEL limiter action check mode selected; Reduce AVR_Kg; View UEL_Active bit

Voltage instability, improper gain, unstable prime mover speed regulator, limiter oscillation, and recalibration of PID; Check the speed regulator; Adjust OEL/UEL gain

4.3 Uneven distribution of reactive power in parallel (sagging or cross flow)

Possible causes investigation and handling of phenomena

The voltage does not sag with reactive power changes and is not enabled. The cross current mode is selected incorrectly. Check for V_DrooopEn=1 and Drooop_CCC_Select=0 (sag); If cross flow is required, check the ID CT wiring

Unequal distribution of reactive power, improper cross current gain, and increased cross current gain due to CT polarity reversal; Measure the polarity of ID+and ID - with a voltmeter, compare with the voltage of phase B, and switch the polarity of CT in reverse phase

Transfer of reactive power in the opposite direction with CT polarity error. Compare the CT polarity of each machine's cross flow to ensure consistency

4.4 Misoperation or non operation of demagnetization protection

No action: Check if the 40 function is enabled; Confirm that the diameter and offset of the M-O circle have been correctly set according to the generator parameters (Xd, X'd); Check if the CT/PT polarity is correct.