verified connector library

SEL-751A feeder protection relay

Register map(s) for this device, each at the trust rung it earned. Addresses are 0-based as on the wire; word order and scaling are only confirmed at the hardware-verified rung.

interop-verified

Read + decoded cleanly over a real network vs an independent third-party Modbus test server (transport and framing; reads are remapped into the server's register window, so the map's own addresses are NOT exercised). Does NOT prove word order/scaling against the actual device.

pointaddress (0-based)typescaleunit
ia_current650U161A
ia_angle651I160.1deg
ib_current652U161A
ib_angle653I160.1deg
ic_current654U161A
ic_angle655I160.1deg
in_current656U161A
in_angle657I160.1deg
ig_current658U161A
ig_angle659I160.1deg
average_current660U161A
neg_seq_curr_3i2662U161A
current_imbal663U160.1%
vsn664U161V
vsn_angle665I160.1deg
vdc666U160.1V
vab667U161V
vab_angle668I160.1deg
vbc669U161V
vbc_angle670I160.1deg
vca671U161V
vca_angle672I160.1deg
average_line673U161V
van674U161V
van_angle675I160.1deg
vbn676U161V
vbn_angle677I160.1deg
vcn678U161V
vcn_angle679I160.1deg
vg680U161V
vg_angle681I160.1deg
average_phase682U161V
neg_seq_volt_3v2683U161V
voltage_imbal684U160.1%
real_power685I161kW
reactive_power686I161kVAR
apparent_power687I161kVA
power_factor688I160.01
frequency689U160.01Hz
mwh3po_hi690U160.001MWhr
mwh3po_lo691U160.001MWhr
mvarh3pi_hi692U160.001MVARh
mvarh3pi_lo693U160.001MVARh
mvarh3po_hi694U160.001MVARh
mvarh3po_lo695U160.001MVARh
mvah3p_hi696U160.001MVAh
mvah3p_lo697U160.001MVAh
max_winding_rtd712I161°C
max_bearing_rtd713I161°C
max_ambient_rtd714I161°C
max_other_rtd715I161°C
rtd_1716I161°C
rtd_2717I161°C
rtd_3718I161°C
rtd_4719I161°C
rtd_5720I161°C
rtd_6721I161°C
rtd_7722I161°C
rtd_8723I161°C
rtd_9724I161°C
rtd_10725I161°C
rtd_11726I161°C
rtd_12727I161°C
ls_1729U160.1%
ls_2730U160.1%
ls_3731U160.1%
ls_4732U160.1%
vs_rms739U161V
ia_rms740U161A
ib_rms741U161A
ic_rms742U161A
in_rms743U161A
va_rms744U161V
vb_rms745U161V
vc_rms746U161V
vab_rms747U161V
vbc_rms748U161V
vca_rms749U161V

link settings as documented (unverified): RTU/TCP; default 9600 8N1; unit ID 1; FC 01,02,03,04,05,06,08,16,96,97,98,125,126; Supports up to two Modbus TCP sessions on Port 1 (default port 502). Modbus RTU is supported on Port F, Port 2, Port 3, and Port 4.

⚠ Default passwords should be changed to private passwords at installation. Failure to change each default password may allow unauthorized access. — Starkest reads only; we never write a control register.

bench facts as documented (unverified)
terminalsIP20
A/B polarityObserve proper polarity on power connections: +/H (terminal A01) and -/N (terminal A02)
terminationEnsure proper line termination at the receiver for EIA-485 (up to 1200 m)
connector9-pin D-subminiature male for EIA-232, 5-pin Euro for EIA-485, RJ-45 for copper Ethernet, LC for fiber Ethernet
isolationPOWER terminals are isolated from chassis ground. Port 1, Port 2, Port 3 (EIA-485), and Port 4A are isolated.
shield/groundChassis ground connector located on the rear-panel card Slot A must always be connected to the local ground mat.
wiring notesEIA-485 plug-in connector accepts wire size AWG 24 through AWG 12.
max registers/read125
protocol notesMaximum of 125 registers can be read at once with function codes 03h and 04h. Maximum of 100 registers can be written at once with function code 10h.
serial register640
firmware register4004
identification notesSerial number is split across registers 640 (high) and 641 (low). Firmware revision is at register 4004.
FC 43 device IDnot supported
powerHigh Voltage: 110-250 Vdc, 110-240 Vac, 50/60 Hz (<40 VA ac, <20 W dc). Low Voltage: 24-48 Vdc (<20 W dc).
environmentOperating temperature: -40 to +85°C. Altitude: up to 2000 m. Relative humidity: 5 to 95% noncondensing. Pollution Degree 2. Overvoltage Category II. Atmospheric pressure: 80 to 110 kPa.
accuracyPhase Currents: +/-2% of reading, +/-2 deg. Line-to-Line Voltages: +/-1% of reading, +/-1 deg. System Frequency: +/-0.01 Hz of reading.
certificationsISO 9001, UL, cUL, CSA, CE, Hazardous Locations Approvals (Class 1, Division 2, Groups A, B, C, D, T4)
doc revision20130329
firmware applicabilityR300, R400 series

generated by gemini:gemini-3.5-flash · harvested from https://nepsi.com/resource/SEL-751A-Instructions.pdf (Schweitzer (SEL)); manual-faithful — the document's claims, panel risk: ELEVATED — panel is not confident; proved interop-verified on 2026-06-10 · recorded 2026-06-10

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

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