Nthytronic Group iRTUe I/O Expansion Module

Nthytronic Group iRTUe I/O Expansion Module: A High Performance I/O Solution for Substation Automation

In contemporary substation automation systems, there is an increasing demand for real-time performance, reliability, and flexibility. Traditional serial communication protocols and fixed configuration I/O modules are no longer sufficient to meet advanced application requirements such as logic interlocking and load offloading. The iRTUe series I/O expansion module has emerged - it transforms any main control unit (RTU, gateway, or third-party IED) into a powerful I/O processing center through IEC 61850 GOOSE communication (processing time less than 3ms), while being compatible with traditional Modbus protocol, making it an ideal choice for new construction and renovation projects. This article provides a comprehensive technical guide for power system engineers by analyzing the hardware configuration, communication mechanism, I/O characteristics, installation selection, and typical application scenarios of iRTUe from an engineering application perspective.

Product positioning and core values

IRTUe is a modular and flexible I/O expansion unit designed specifically for substations and the energy industry. It is connected to the main station equipment (such as iRTU, iGW, or other third-party control units) through dual Ethernet (copper or fiber optic) or serial EXP422 interface, greatly expanding the data acquisition and control output capabilities of the main station. Its core values are reflected in:

Fast GOOSE communication: IEC 61850 GOOSE messages based on publish/subscribe mechanism, processing time ≤ 3ms (compliant with IEC 61850 performance level P2), meeting the strict requirements of real-time protection and automation.

Highly flexible I/O configuration: Each iRTUe can accommodate two I/O cards, providing various combinations such as digital input, relay output, DC analog input, AC voltage and current input, and supporting up to 48 DI, 16 DO, 16 AI, or 3 AC voltage+3 AC current.

Wide protocol compatibility: Supports both modern IEC 61850 GOOSE and Modbus with event buffering and timestamps, facilitating communication with outdated substation equipment or third-party master stations.

Robust electromagnetic compatibility: compliant with power industry standards such as IEC 61850-3, IEC 60870-2-1, IEC 60255-26, suitable for harsh electromagnetic environments.

Deep Analysis of IEC 61850 GOOSE Communication Mechanism

2.1 Working principle of GOOSE

GOOSE (Generic Object Oriented Substation Event) is a fast and reliable message transmission mechanism defined in the IEC 61850 standard. It adopts a publish/subscribe model: iRTUe acts as a subscriber (or publisher), receives GOOSE messages from intelligent electronic devices (IEDs) in real time, parses the state variables (such as circuit breaker position, fault signals), and updates the local I/O status. The enhanced retransmission mechanism ensures reliable delivery of messages even in network congestion.

Processing time<3ms means that the end-to-end delay from GOOSE message reaching the network port of iRTUe to message content being parsed and applied to output relays or internal logic is extremely low, which allows iRTUe to participate in interlocking and fast load unloading logic with extremely strict time requirements.

2.2 VLAN and Priority Tagging

GOOSE messages support IEEE 802.1Q virtual LAN and priority tagging. By allocating GOOSE traffic to independent VLANs and assigning high priority (such as 4 or 5), it can be ensured that critical GOOSE messages will not be blocked by regular data flows (such as file transfers and log uploads) even when the network load is high. In the complex network of substations, this characteristic is the foundation for achieving reliable GOOSE communication.

2.3 GOOSE Configuration and Address Setting

The GOOSE communication address of iRTUe can be easily configured through the side dip switch, and the default multicast group is set to 0 (which can be modified through the iConf tool). For more complex logical node configurations, iRTUe predefines GCIO logical nodes, and future firmware upgrades will support importing any SCL (Substation Configuration Language) file, seamlessly integrating it into the entire IEC 61850 model.

I/O board configuration and electrical characteristics

IRTUe adopts a modular design, with each unit supporting the installation of two I/O cards. The following predefined configuration models are provided (a total of 8 standard configurations, which can also be customized according to needs):

Model suffix: Digital input, Relay output, Analog input (DC), AC input

#DIDI 48 0 0 0

#RIRI 0 16 0 0

#AIAI 0 0 16（4-20mA） 0

#DIRI 24 8 0 0

#DIAI 24 0 8 0

#RIAI 0 8 8 0

#OOQI 0 0 0 3 voltage+3 current

3.1 Digital Input (DI)

Maximum quantity: 48 channels (divided into two groups, each with 24 channels)

Isolation voltage: 2.5 kVrms (shared common terminal for every 8 inputs)

Activation threshold: ON when>85% rated voltage, OFF when<60% rated voltage (other thresholds can be customized as needed)

Rated voltage options: 24 Vdc, 48 Vdc, 125 Vdc, 220 Vdc

Special feature: Each input can be configured as a counter and comes with an independently adjustable anti shake filter. The timestamp accuracy reaches 1 ms.