DLR Operating Envelope 🌡️📈

Environmental sensor collection and IEEE 738 dynamic line rating calculations

Pre-requisites

• python 3.13+
• Raspberry Pi

Sensors

Sensor	Interface	Purpose	Data Type
FLIR Lepton	SPI	Conductor temperature	Thermal imaging
DHT22	GPIO	Ambient temp/humidity	Digital
SI1145	I2C	Solar radiation	UV/Visible/IR
YL-83	ADC	Rain detection	Analog
Calypso ULP STD ultrasonic	I2C	Wind speed + direction	Digital

Anemometer required for IEEE 738 compliance — convective cooling from wind is the dominant heat-dissipation mechanism for overhead conductors. Ultrasonic preferred over cup-style: zero stall speed, no inertia, accurate at the low wind speeds where DLR matters most.

Component choice: Calypso Instruments ULP STD Ultrasonic Wind Meter — 0.12 W average draw fits the solar/LiFePO4 budget, runs over the existing I2C bus (no new transceiver IC needed on the carrier — same bus as the SI1145), gives speed + direction in one telegram. Marine-origin IP-rated enclosure for outdoor mast mount.

Cheaper fallback: Modern Devices Wind Sensor Rev. P (MEMS hot-wire, analog 0–3.3V) — reuses an ADS1115 channel; no direction.

Core Algorithm

Dynamic rating calculation using IEEE 738 standard:

$$ P_{max} = \frac{(T_{max} - T_{amb} - ΔT_{solar} + ΔT_{rain})}{R_{thermal}} $$

Where:

• Conductor max temp (80°C): $T_{max}$
• DHT22 reading: $T_{amb}$
• SI1145 radiation factor: $ΔT_{solar}$
• YL-83 cooling coefficient: $ΔT_{rain}$
• FLIR Lepton thermal resistance: $R_{thermal} = \frac{(T_{conductor} - T_{ambient})}{P_{current}}$

Context Deployment

rectangle dlr_operating_envelope

cloud sensors
queue mqtt_broker
rectangle dlr_pst_sim
rectangle industrial_gateway

dlr_operating_envelope -- sensors
dlr_operating_envelope -- mqtt_broker: mqtt
mqtt_broker -- dlr_pst_sim
dlr_operating_envelope -- industrial_gateway: dnp3

Context Sequence

participant sensors
participant dlr_operating_envelope
participant dlr_pst_sim
participant industrial_gateway

sensors -> dlr_operating_envelope: environmental readings
dlr_operating_envelope -> dlr_pst_sim: mqtt measurements
industrial_gateway -> dlr_operating_envelope: poll dnp3 points

Deployment

rectangle dlr_operating_envelope #line.dashed {
  rectangle thermal_camera
  rectangle temp_humidity_sensor
  rectangle uv_light_sensor
  rectangle rain_sensor
  rectangle ieee738_calc
  rectangle mqtt_publisher
  rectangle dnp3_outstation
}

queue mqtt_broker
rectangle industrial_gateway

dlr_operating_envelope -- mqtt_broker: mqtt
dlr_operating_envelope -- industrial_gateway: dnp3

Sequence

participant sensors
participant ieee738
participant mqtt_publisher
participant dnp3_outstation
queue mqtt_broker
participant industrial_gateway

sensors -> ieee738: temp + humidity + solar + rain
ieee738 -> mqtt_publisher: derived values
ieee738 -> dnp3_outstation: update analog input points
mqtt_publisher -> mqtt_broker: publish measurements
industrial_gateway -> dnp3_outstation: poll Group 30 + Group 1

MQTT Topics Published

Per ems/topic_structure_adr.md. Payload is FloatSample {ts, value} unless noted.

• sites/{site_id}/devices/{device_id}/measurements/conductor_temp/celsius
• sites/{site_id}/devices/{device_id}/measurements/ambient_temp/celsius
• sites/{site_id}/devices/{device_id}/measurements/humidity/percent
• sites/{site_id}/devices/{device_id}/measurements/solar_irradiance/watts_per_m2
• sites/{site_id}/devices/{device_id}/measurements/rain/none — BooleanSample
• sites/{site_id}/devices/{device_id}/measurements/dynamic_rating/amps — derived per IEEE 738
• sites/{site_id}/devices/{device_id}/measurements/status/none — EnumSample, LWT-backed

Project Structure

├── pyproject.toml           # Dependencies and build config
├── src/
│   ├── main.py              # Application entry point
│   ├── sensors/             # Sensor driver modules
│   ├── __init__.py
│   ├── thermal_camera/
│   │   ├── thermal_camera_client_test.py
│   │   ├── thermal_camera_client.py
│   │   ├── thermal_camera_driver.py
│   │   └── __init__.py
│   ├── temp_humidity_sensor/
│   │   ├── temp_humidity_sensor_client_test.py
│   │   ├── temp_humidity_sensor_client.py
│   │   ├── temp_humidity_sensor_driver.py
│   │   └── __init__.py
│   ├── uv_light_sensor/
│   │   ├── uv_light_sensor_client_test.py
│   │   ├── uv_light_sensor_client.py
│   │   ├── uv_light_sensor_driver.py
│   │   └── __init__.py
│   ├── rain_sensor/
│   │   ├── rain_sensor_client_test.py
│   │   ├── rain_sensor_client.py
│   │   ├── rain_sensor_driver.py
│   │   └── __init__.py
│   ├── ieee738.py           # IEEE 738 calculation engine
│   ├── ieee738_test.py      # Algorithm unit tests
│   ├── mqtt_client.py       # MQTT publisher
│   ├── mqtt_client_test.py  # MQTT client tests
│   └── config.py            # Configuration management
├── tests/
│   └── test_integration.py  # End-to-end integration tests
└── README.md                # This file

Usage

uv run python src/main.py