Overview

The IOMod FPI is a dedicated fault passage indicator module for medium voltage applications. As a core part of our portfolio of grid automation products, it provides crucial detection and monitoring capabilities. This fault passage indicator module can be used as a standalone unit or integrated into our mini RTU platform, supporting both current and voltage sensors or connected via adapters to current and voltage transformers, with communication protocols including Modbus RTU, IEC 60870-5-101 and IEC 60870-5-103. Designed to deliver accurate earth-fault and short-circuit indication, this fault passage indicator supports directional detection for enhanced event isolation and swift response.

The IOMod FPI is built for demanding environments in electrical distribution substations, renewable-generation sites, and railway power supplies, where an early indication of a fault enables faster restoration of service. With its compact size and high functional complexity, it fits easily into recloser installations, RTU cabinets, or switchgear retrofit projects. The ability to calculate neutral current (I0) and neutral voltage (U0), as well as full phase-by-phase active, reactive, and apparent power, power factors, and phase angles ensures that this fault passage indicator provides more than simple fault detection—it becomes part of a modern smart grid architecture.

When a fault occurs, the device triggers a local light signal along with digital messaging, ensuring field staff can quickly locate the fault passage indicator that has signalled the event. Utilities and distribution network operators gain real-time insight into the grid status, enabling precision in finding electrical circuits impacted by an event. By deploying this fault passage indicator across feeders, operators reduce general failure risks, improve system resilience, and turn every part of the network into a fault-aware node. This fault passage indicator is more than a detection tool—it’s a key component in your grid automation products strategy, enhancing automation, visibility, and control.

Features

Directional fault detection for all network types;
Earth fault detection/GND fault indicator;
50 Instantaneous overcurrent detection;
50N Neutral instantaneous overcurrent detection;
51/67 Phase directional overcurrent detection;
67N Neutral directional overcurrent detection;
27 Under voltage detection (with VT or voltage sensors);
59 Over voltage detection (with VT or voltage sensors);
59N Neutral over voltage detection / permanent earth fault (with VT or voltage sensors);
81HBL2 Inrush blocking for selected protections;
2 settings groups;
integration into Elseta mini RTU;
Measurements of RMS values for currents, phase, and phase-to-phase voltages.
Additional measurements of:
- Frequency;
- Active, reactive, and apparent power;
- Neutral voltage, neutral current;
- Power factor;
- Phase angle;

Analog inputs measurement in 16-bit resolution.
3x low-power (LoPo) current measuring inputs (225 mV) or 3x1A/5A CT with the adapter.
3x low-power (LoPo) voltage measuring inputs (3.25 V/√3) or 3x100V/400V VT with the adapter.
Frequency acquisition (Nominal frequencies: 50 and 60 Hz; Frequency range: 45–65 Hz).
Communication port: RS485.
Communication over Modbus RTU, IEC 60870-5-101, and IEC 60870-5-103 protocols.

Link to older version V1.1

Specifications

Device data
Article number	IOMOD-FPI V2.0
Product Description	3 Current sensor inputs and 3 Voltage sensor inputs module
Configuration software	IOMOD Utility*
Warranty	2 years
Measurement values and functions
Analog inputs	6x 16-bit resolution
Input types	Channel-independent
Current inputs	3
Current inputs measurement range	225 mV (IEC 61869-10) with external adapter 1A / 5A
Current input impedance	1 MΩ; < 170 pF
Accuracy	1%
Voltage inputs	3
Voltage input measurement range	3.25 V/√3 AC (IEC 61869-11) with external adapter 100VAC / 400VAC
Voltage input impedance	1 MΩ; < 170 pF
Accuracy	1%
Frequency measurement range	45..65 Hz
Overvoltage protection	±20V
Interface and communication
RS485 interface	ANSI/TIA/EIA-485-A-1998
Communication protocols	– Modbus RTU Slave; – IEC 60870-5-101 Slave; – IEC 60870-5-103 Slave.
Baudrate	600 – 115200
Parity	None, Even, Odd
Terminating resistors	120 Ohm (configurable)
USB interface
Type	Mini USB
Use	Configuration/Firmware upgrade
Power supply
Auxiliary power supply	9-58VDC (full range)
Power consumption	40mA @ 12VDC, 20mA @ 24 VDC
Insulation voltage	3 kV
Operating conditions
Operating temperature	-40°C … 85°C
Storage temperature	-40°C … 85°C
Humidity	max. 95 % (non-condensing)
Protection class	IP20
Dimensions and installation instructions
Case height x width x depth	119 x 22.5 x 101 mm
Installation type	DIN Rail mounting
Standarts	EN 61000-4-2:2009 EN 61000-4-3:2021 EN 61000-4-4:2013 EN 61000-4-5:2014+A1:2018 EN 61000-4-6:2024 EN 61000-4-8:2010 EN 61000-6-3:2021 EN 61000-6-4:2020
Changelog 1.1->2.0	Expanded Power Supply Range: Extended input range from 9–33V to 9–58V Improved Surge Protection. Added 4th current input. Different connectors option: Model with plug connectors; Model with RJ45 connectors. Added brownout extension to prevent device bricking.

* IOMOD Utility is configuration tool for IOMOD devices with firmware v2.x.

Fault passage indicator use cases:

For utilities aiming to improve reliability metrics — by speeding up fault detection and restoration, the module helps reduce outage duration and frequency (SAIDI / SAIFI), increasing overall customer satisfaction and grid stability.
In ring-connected distribution networks, placing the IOMod FPI units at strategic points helps isolate the faulted section precisely. The directional detection functionality built into the fault passage indicator simplifies fault location, so crews don’t need to patrol the entire network blindly.
In medium-voltage distribution substations — whether retrofit or new installations — IOMod FPI helps operators quickly detect downstream faults: its built-in fault passage indicator reveals when a fault has passed through the monitored line, making it much easier to identify that “something went wrong” immediately.
Detect damaged network cables with IOMod FPIs earth fault detection/GND fault indicator and identify the affected area quickly without the need to guess.