Beckwith M-3425A Relay Guide

Beckwith M-3425A Relay Guide

Product Overview and Functional Architecture

M-3425A is a microprocessor based digital generator protection relay that utilizes digital signal processing technology to provide the following protection functions:

1.1 Base Package

24 overexcitation (V/Hz)

27 phase undervoltage

32 directional power (reverse power, low forward power, or over power, can be tripped sequentially)

40 demagnetization (dual zone offset mO, capable of under voltage acceleration)

46 Negative sequence overcurrent and alarm

50 instantaneous phase overcurrent

50/27 accidental power on protection

50BF circuit breaker malfunction

50N instantaneous neutral overcurrent

51N inverse time neutral point overcurrent

51V voltage control/voltage braking phase overcurrent

59 phase overvoltage

59N neutral point overvoltage

59X Multipurpose Overvoltage (Interturn Fault or Bus Grounding)

60FL voltage transformer fuse loss detection and locking

67N zero sequence direction overcurrent

81 Four Step Over/Under Frequency

87 phase differential

87GD zero sequence differential

IPSigmic Programmable Logic

1.2 Comprehensive Package

Add the following features:

21 Three section inter phase distance protection (can be used as out of step locking, with load intrusion blind zone)

27TN third harmonic neutral point undervoltage (in conjunction with 59N to achieve 100% stator grounding)

49 stator overload (positive sequence overcurrent)

50DT timed overcurrent (for split phase differential)

59D Third Harmonic Voltage Ratio Differential

78 step loss protection (Mu Ou characteristic)

81A frequency accumulation

81R frequency change rate

1.3 Optional advanced features

25 Synchronous inspection (with dead busbar/dead line closing)

64F/64B rotor grounding and carbon brush lifting detection (requires external M-3921 coupler)

64S 100% stator grounding protection (20Hz low-frequency injection method, requiring external 20Hz signal source, bandpass filter, and CT)

Installation and wiring points

2.1 Mechanical Installation

M-3425A is a standard 19 inch rack mount, with optional heights of 3U (without expansion I/O) or 4U (with expansion I/O), and can also be installed vertically on a panel. Environmental temperature -20~+70 ℃, humidity ≤ 95%, no condensation. Good heat dissipation and ventilation should be ensured during installation.

2.2 Power Supply and Grounding

Power supply: Optional 24/48Vdc (18-56V) or 110/125/220/250Vdc/110/120/230/240Vac, with a power consumption of approximately 40VA. Optional redundant power supply.

Grounding: The equipment grounding terminal (protective ground) must be reliably connected to the power station grounding grid, and the grounding resistance should be less than 0.1 Ω.

2.3 Voltage Transformer (VT) Wiring

M-3425A provides 5 voltage input terminals, which can be flexibly configured as:

Single phase (line to line or line to ground)

Open Triangle (Two PT)

Three phase three wire star

Three phase four wire star

Dual bus (single-phase only)

Important: The transformation ratio and wiring method of the generator side VT and the bus side VT need to be accurately configured in the system settings. When using line to ground voltage but wanting to calculate internally according to line to line, the "Line Ground to Line" mode can be selected. At this time, the rated voltage should be set to the line to line value (approximately √ 3 times the line to ground value), and the secondary line to ground voltage should be 69V (not 120V).

2.4 Wiring of Current Transformer (CT)

Provide 7 current inputs, which can be connected to:

Three phase current (IA, IB, IC)

Three phase neutral point side current (Ia, Ib, Ic) - used for differential

Neutral point current (IN) or residual current

Cross flow compensation CT (ID+/-)

The CT secondary rating can be selected as 1A or 5A. Warning: The CT circuit must not be open circuited, and the CT secondary side must be short circuited before debugging.

2.5 Switching input/output

6 programmable control/status inputs (with expandable I/O up to 14), providing 24V wet contacts internally, only able to connect dry contacts.

8 programmable output relays (with expandable I/O up to 23), contact capacity: disconnect 6A/120Vac, 0.5A/48Vdc, 0.3A/125Vdc, etc.

The output relay can be configured as a pulse or self holding.

2.6 Communication Interface

COM1: Front panel RS-232 (DTE)

COM2: Rear panel RS-232 (if Ethernet option is enabled, COM2 is not available, but IRIG-B is still available)

COM3: Rear panel RS-485

Optional RJ45 Ethernet (supports MODBUS TCP/IP, BECO2200 over TCP/IP, or IEC 61850)

IRIG-B: BNC interface (accepts modulated signals) or COM2 pin 6 (TTL level, requires jumper)

Software configuration and debugging

3.1 IPScom software installation and connection

The accompanying IPScom communication software runs on Windows 2000 and above systems. The first connection requires the use of a null modem cable to connect the RS-232 port and relay COM1 port of the PC, with a default baud rate of 9600, 8 data bits, 1 stop bit, and no verification. The default communication address is 1. If communication fails, COM1 settings can be viewed/modified through the front panel HMI.

3.2 System Setup

To select 'Relay/Setup/Setup System' in IPScom, the following system parameters must be entered correctly: