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IG502 - IEC 60870-5-101 to IEC 60870-5-104 Protocol Conversion

Product Model: IG502 (InGateway 502)

1. Executive Summary

In power utilities, smart grid, water / gas pipelines and other industrial control environments, a very large installed base of RTUs (Remote Terminal Units), protection relays, IEDs and metering devices still communicates over IEC 60870-5-101 — a serial, byte-oriented telecontrol protocol designed for low-bandwidth links (RS-232 / RS-485 / fiber modems).

Modern SCADA / DMS / EMS master stations and cloud-based monitoring platforms, however, expect IEC 60870-5-104 — the IP-based variant of the same telecontrol standard, transported over TCP/IP (port 2404).

The InHand IG502 Edge Gateway bridges these two worlds. Acting as an IEC 101 master on the serial side and an IEC 104 server on the Ethernet / cellular side, it converts traffic transparently — preserving Type IDs, Information Object Addresses (IOA), Cause of Transmission (COT) and ASDU addressing — so existing legacy devices can be integrated into modern IP-based SCADA systems without replacing any field equipment.

This document describes the application scenarios, system architecture and value the IG502 delivers in such projects.

Reference Topology — IEC101 to IEC104 Conversion

2. Background & Pain Points

2.1 The Legacy Reality

Field assets such as substation RTUs, feeder terminal units (FTUs), distribution transformer terminal units (TTUs), pole-mounted reclosers and older protection IEDs were installed years — sometimes decades — ago. They typically expose:

  • RS-232 / RS-485 / RS-422 serial ports
  • IEC 60870-5-101 as the application protocol (balanced or unbalanced mode)
  • 1200 / 2400 / 9600 / 19200 bps speeds
  • Proprietary cabling and short-range fiber modems

Replacing these devices to gain native IEC 104 connectivity is rarely feasible — both because of CAPEX and because of the operational risk of touching critical primary equipment.

2.2 The Modern Requirement

At the same time, control centers are being modernized:

  • Master stations move from dedicated serial fan-out cabinets to IP-based SCADA / DMS platforms
  • Centralized telemetry is required for fault location, isolation and service restoration (FLISR)
  • Cyber-security standards (IEC 62351, NERC CIP and similar) require network segmentation, authentication and audit trails — natural for IP, painful for raw serial
  • Cellular (4G / 5G) backhaul is used to reach unmanned, geographically dispersed sites
  • Cloud / edge analytics require a uniform northbound data plane

2.3 The Gap

The protocol-conversion gap between IEC 101 and IEC 104 is the single largest barrier to integrating brownfield assets into greenfield SCADA infrastructure. A purpose-built protocol-conversion gateway resolves this gap.

3. Solution Overview

3.1 Role of the IG502

The IG502 sits at the field edge and performs three roles simultaneously:

  1. IEC 101 master on the RS-232 / RS-485 serial port, polling one or more downstream IEC 101 outstations.
  2. IEC 104 server on the Ethernet (or cellular WAN) port, accepting connections from upstream SCADA masters on TCP/2404.
  3. Edge router providing 4G / 5G / wired uplinks, VPN, firewall and remote management.

Because the IG502 keeps the IEC 101 / 104 data model identical (Type ID, IOA, COT and ASDU address are preserved one-for-one), the SCADA master station sees the legacy device as if it were natively IEC 104.

3.2 Reference Architecture

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┌──────────────────────┐     RS-485       ┌──────────────┐     Ethernet / 4G      ┌──────────────────┐
│  IEC 101 Outstations │ ───────────────► │   IG502      │ ─────────────────────► │  IEC 104 SCADA   │
│  (RTU / IED / FTU)   │   IEC 60870-5-101│   Gateway    │  IEC 60870-5-104 (2404)│  Master Station  │
└──────────────────────┘                  └──────────────┘                        └──────────────────┘
                                          │   Protocol   │
                                          │   conversion │
                                          │ + edge router│

A four-layer model:

Layer Components Role
Field / Sensing RTU, IED, FTU, TTU, recloser, meter Generate telemetry / accept controls (IEC 101)
Edge / Gateway IG502 Polls IEC 101, exposes IEC 104, buffers, secures, routes
Transport Wired Ethernet, 4G / 5G, optional VPN Carries IEC 104 traffic to the control center
Application SCADA / DMS / EMS / cloud HMI Consumes IEC 104, drives dashboards and controls

3.3 IEC 101 vs IEC 104 — Standards at a Glance

Aspect IEC 60870-5-101 (serial) IEC 60870-5-104 (TCP/IP)
Physical layer RS-232 / RS-485 Ethernet / 4G / 5G
Link layer FT 1.2 frame, balanced / unbalanced TCP, APCI (start / stop / test)
ASDU Type IDs identical (M_SP_NA_1, M_DP_NA_1, M_ME_NC_1, C_SC_NA_1, …) Type IDs identical
Application data Preserved end-to-end through the gateway Preserved end-to-end through the gateway
Typical TCP port n/a 2404

The IG502 bridges the link-layer and physical-layer differences while keeping the application-layer data model untouched — this is what allows a SCADA point list developed for IEC 104 to remain valid against legacy IEC 101 devices.

4. Application Scenarios

4.1 Smart Grid — Distribution Automation

Pain: Hundreds of pole-top FTUs and TTUs across a feeder still speak IEC 101 over serial. The new distribution master station only supports IEC 104.

Solution: Mount one IG502 per site (or per ring main unit). Serial side connects to the FTU; cellular side reports to the master via APN-private 4G. Existing FTUs are kept in service for their full economic life.

Benefit: No primary-equipment replacement, single-digit minutes per site for commissioning, fault data reaches dispatchers in real time.

4.2 Substation Retrofit

Pain: Indoor / outdoor substations with legacy protection IEDs aggregated by an IEC 101 bay controller. The utility wants centralized monitoring without rewiring the bay.

Solution: Place an IG502 in the substation telecom cabinet. Wire RS-485 to the bay controller; uplink via fiber Ethernet (or 4G backup) to the regional control center on IEC 104.

Benefit: Drop-in modernization; the substation appears as a native IEC 104 RTU; redundant WAN (wired + 4G) improves availability.

4.3 Renewable Generation — Solar / Wind Farms

Pain: Inverters, combiner boxes and weather stations expose IEC 101; the SCADA / energy management system at the regional operations center is IEC 104 only.

Solution: IG502 per inverter zone or per substation skid; converts IEC 101 telemetry (active power, reactive power, faults, switches) into IEC 104; uplink to operator's cloud SCADA.

Benefit: Plant-wide observability over standardized IP transport; ready for cyber-security hardening (VPN, firewall, role-based access).

4.4 Water, Gas and District Heating

Pain: Pumping stations, valve chambers and pressure regulators use serial IEC 101; the utility's IP network and SCADA expect IEC 104.

Solution: Pole-mounted or cabinet-mounted IG502s convert protocols and provide cellular backhaul where wired networks are not available.

Benefit: Single multi-purpose device (router + protocol gateway + edge compute) reduces BoM and footprint inside small cabinets.

4.5 Railway and Industrial Energy Systems

Pain: Traction substations and large industrial sites operate IEC 101 RTUs purchased a decade ago; new EMS platforms standardize on IEC 104.

Solution: IG502 sits between the RTU and the IT / OT boundary, exposing IEC 104 northbound and (optionally) MQTT for IT analytics.

Benefit: OT data is freed for digitalization initiatives without disturbing the safety-critical control loop.

5. Solution Highlights

  1. Drop-in conversion — same Type IDs, COT and IOA on both sides; no SCADA point-list rework required.
  2. Industrial-grade hardware — wide-temperature, fanless, DIN-rail; designed for substations and outdoor cabinets.
  3. Multiple uplinks — Gigabit Ethernet, 4G / 5G, with link backup and seamless failover.
  4. Edge compute & buffering — Python / Docker container, local caching, store-and-forward during WAN outages.
  5. Secure by design — IPsec / OpenVPN / L2TP, firewall, RBAC, signed firmware, optional IEC 62351 compatible TLS deployments.
  6. Remote management — InHand Device Manager Cloud for batch configuration, monitoring, firmware updates and remote troubleshooting.
  7. Verified interoperability — validated against widely-used IEC 101 and IEC 104 master / outstation systems.

6. Why InHand IG502

Requirement What the IG502 delivers
Protocol conversion IEC 101 ↔ IEC 104 Native — no scripting required
Other industrial protocols Modbus RTU/TCP, OPC UA, DLT/645, MQTT, transparent TCP — coexisting with IEC stack
Connectivity 2× GbE, RS-232, RS-485, 4G / 5G, Wi-Fi (model dependent)
Edge compute Python SDK, Docker, local rules, store-and-forward
Security VPN, firewall, RBAC, signed firmware
Remote O&M InHand Device Manager Cloud
Environmental -40 °C to +75 °C, fanless, DIN-rail, surge protection
Certifications FCC, CE, RoHS (regional models — confirm with InHand sales)

7. Deployment Outline

  1. Survey the field site: identify RTUs / IEDs, serial parameters, IEC 101 framing details.
  2. Select uplink: wired Ethernet, 4G , or both with link backup.
  3. Validate end-to-end with the customer's SCADA master station.
  4. Onboard the gateway to InHand Device Manager Cloud for long-term operations.