For pilot testing real-time distribution monitoring, the “best” free options are usually the ones that give you:

• SCADA/DMS-like visualization
• Real-time telemetry ingestion
• Open protocols like MQTT, Modbus, IEC 60870-5-104, OPC UA
• Easy integration with sensors, RTUs, or simulators
• Low cost to deploy on-prem or in the cloud

Here are the strongest free / open-source options to consider:

1) OpenDSS

Best for: Distribution system simulation and basic monitoring studies

• Open-source distribution system simulator from EPRI
• Excellent for feeder analysis, volt/var studies, DER impacts, load flow
• Often used with Python or MATLAB interfaces
• Not a full real-time control platform, but very good for pilot testing monitoring logic and analytics

Why choose it: If your pilot is more about what to monitor and how the grid behaves rather than building a live SCADA screen, OpenDSS is a top choice.

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2) GridLAB-D

Best for: Detailed distribution simulation with time-series behavior

• Open-source simulator designed for distribution networks, smart grid, DERs, and load interactions
• Supports dynamic simulations
• Good for testing monitoring algorithms, sensor placement, and control strategies

Why choose it: Strong for research-grade pilot projects where you want realistic feeder and load behavior.

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3) Pandapower

Best for: Python-based grid modeling and analytics

• Open-source Python library for power system modeling and analysis
• Great for fast prototyping, integration with data pipelines, and visualization
• Works well if you want to connect simulated telemetry into dashboards or analytics tools

Why choose it: Best if your team already uses Python and wants flexible experimentation.

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4) OpenMUC j60870 / Eclipse Ditto / Eclipse Kura

Best for: Communication and edge integration
These are not full grid management suites, but useful for real-time data acquisition and device integration.

• OpenMUC j60870: IEC 60870-5-104 protocol support
• Eclipse Ditto: digital twin and device state management
• Eclipse Kura: edge gateway framework

Why choose it: Good when your pilot needs to ingest data from field devices and pass it into a dashboard or simulation environment.

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5) ScadaBR

Best for: Free SCADA-style monitoring for small pilots

• Open-source SCADA/HMI platform
• Supports common industrial protocols and real-time monitoring screens
• Useful for basic distribution monitoring dashboards

Why choose it: A practical free option if you need a simple SCADA-like interface quickly.

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6) RapidSCADA

Best for: Lightweight SCADA and telemetry monitoring

• Free and open-source
• Good for real-time data collection, alarms, trends, and dashboards
• Supports various data sources and protocols

Why choose it: Often easier to set up than larger enterprise systems for small pilots.

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7) ThingsBoard Community Edition

Best for: Real-time IoT dashboards for grid telemetry

• Open-source IoT platform
• Good for telemetry visualization, alarm rules, time-series dashboards
• Works well if you want to monitor sensors, meters, or simulated feeder data in real time

Why choose it: Strong choice for a pilot where the main goal is a live dashboard rather than deep power-system modeling.

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8) Node-RED + InfluxDB + Grafana

Best for: Flexible DIY real-time monitoring stack

• Node-RED: data flow orchestration and protocol integration
• InfluxDB: time-series storage
• Grafana: dashboards and alerts

Why choose it: Probably the most flexible free stack for rapid pilot deployment.
It’s not a grid-specific suite, but it’s excellent for:

• ingesting RTU/PLC/sensor data
• transforming telemetry
• building real-time dashboards
• alerting on thresholds/anomalies

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Best picks by use case

If you want grid simulation + monitoring studies

• OpenDSS
• GridLAB-D
• Pandapower

If you want real-time dashboarding and telemetry

• ThingsBoard CE
• RapidSCADA
• ScadaBR
• Grafana + InfluxDB + Node-RED

If you want device/edge integration

• Eclipse Kura
• OpenMUC
• Eclipse Ditto

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My practical recommendation for a pilot

If your goal is pilot testing real-time distribution monitoring, I’d suggest:

Option A: Best all-around free pilot stack

• Pandapower or GridLAB-D for simulation
• Node-RED for data flow
• InfluxDB + Grafana for real-time dashboards

Option B: If you want a SCADA-like experience quickly

• RapidSCADA or ThingsBoard CE

Option C: If your focus is power-system behavior and analytics

• OpenDSS or GridLAB-D

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Things to watch out for

Free tools often have limitations:

• weaker vendor support
• fewer built-in utility-specific functions than commercial DMS/SCADA
• more integration work
• cybersecurity and redundancy features may be limited

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Short answer

For most pilot projects, the best free options are:

1. GridLAB-D or OpenDSS for distribution modeling
2. ThingsBoard CE or RapidSCADA for real-time monitoring dashboards
3. Node-RED + InfluxDB + Grafana if you want the most flexible low-cost stack

If you want, I can also give you:

• a comparison table
• a recommended architecture for a pilot
• or a list of free tools specifically for IEC 61850 / Modbus / SCADA monitoring.