Load shedding is the intentional, temporary reduction of electrical power supply to certain appliances and/or circuits. This is done to reduce electrical consumption and is a cost saving measure. Load shedding helps to balance supply and demand, ensuring the stability of the overall electrical system during times of high demand or when there are issues with power generation.
Why use a Script for Load Shedding?
Using a script running on a Shelly Pro 3EM has a lot of advantages, especially when combined with various other Shelly relays. Scripting can offer a highly customizable and extremely efficient way to accomplish load shedding. A script either from the repopulated Shelly library or manually entered is used to create a system where you can dynamically control and shed loads based on certain conditions, such as high energy consumption or demand.
Prerequisites
Shelly EM Devices
These devices will be used to gather the consumption data required for load shedding
Steps to Setting up Load Shedding
1. Setting Up Shelly Pro 3EM
Wire and Configure the Pro 3EM
Install and Configure: Install the Pro 3EM per the diagram below to monitor the energy consumption of the entire home.
In scenarios where CT-B is not used, it is advised to repurpose it to cover Neutral. This requires recalibrating in the device’s settings.
Standard split single phase electrical systems in North America will only use CT-A and CT-C to cover incoming feeds.
Note: Shelly Pro 3EM must use the C terminal connection to power the meter’s microcontroller, so CT C must always be used. Either CT A and CT B can be used for the other phase.
Terminal C must be connected to line voltage to power the microcontroller of the Pro 3EM.
Legend
Terminals | Cables | ||
|---|---|---|---|
A | Phase A input | LA | Phase A live (110-240 V) cable |
B | Phase B input | LB | Phase B live (110-240 V) cable |
C | Phase C and power supply input | LC | Phase C live (110-240 V) cable |
N | Neutral terminal | L | Mono-phase live (110-240 V) cable |
IA | Phase A current transformer input | N | Neutral cable |
IB | Phase B current transformer input | Current transformers | |
IC | Phase C current transformer input | CTA | Phase A current transformer |
IN | Neutral current transformer input | CTB | Phase B current transformer |
CTC | Phase C current transformer | ||
CTN | Neutral current transformer | ||
Connect to Network: Using Shelly Smart Control, connect the Pro 3EM to your network.
Shelly Pro 3EM supports both Wi-Fi and Ethernet
Shelly Cloud (optional): Add Shelly Pro 3EM to a Shelly Cloud account for remote access.
2. Set Up Additional Shelly Relays
Install Shelly Relays: Install Shelly relays to control the specific loads you want to manage.
Product Specific installation information can be found at the Knowledgebase
Connect to Network: Using Shelly Smart Control, connect the Pro 3EM to your network.
Shelly Pro 3EM supports both Wi-Fi and Ethernet
Shelly Cloud (optional): Add Shelly Pro 3EM to a Shelly Cloud account for remote access.
3. Adding the Load Shedding Script to the Host Pro 3EM
The below steps should be done on a computer using control.shelly.cloud instead of using the App on a mobile device.
Navigate to the Scripts Menu: Shelly Smart Control has a section for Scripts for each compatible device. For Load Shedding we will use a Shelly Pro 3EM. With that device select click on the { } Icon.
Click Open Library and Select the Script: On this screen we will select; Load Shedding with Shelly Pro 4PM and Pro 3EM. Expand this option and press the button labeled Insert Code
Name the Script: At the top of the screen give your script a name.
Setting the Devices to be Shed: The devices to be shed are specified under first_to_last_to_shed
This is an ordered list defining how and when specified devices will be controlled. This list also specified the on and off url’s for the devices.
You are not restricted to using only 5 devices; you can use fewer or more. The number 5 is simply used as an example here. Keep in mind that the higher-numbered entries (4 and 5 in this example) are considered the most important circuits—they will be the last to be turned off and the first to be turned on.
Configuring the Shedding Trigger Parameter:
max_before_shedding
Ensure that the value assigned to max_before_shedding is greater than the value set for min_before_re_adding
A 10% difference should be considered the minimum, but a 20% difference is preferable.
The larger the gap between the minimum and maximum values, the less "churn" you'll experience. Providing sufficient space between these values will enhance the efficiency of your load shedding.
Configuring the Reading of Devices:
min_before_re_adding
Ensure that the value assigned to max_before_shedding is greater than the value set for min_before_re_adding
A 10% difference should be considered the minimum, but a 20% difference is preferable.
The larger the gap between the minimum and maximum values, the less "churn" you'll experience. Providing sufficient space between these values will enhance the efficiency of your load shedding.
Configuring the Polling Frequency:
poll_time
Minimum interval between executing normal on/off steps
short_poll
Interval after toggling on a device assumed to be already on
The minimum value for poll_time should be 60. During "turn on" cycles, ensure you allow sufficient time for inrush spikes to stabilize.
Set Logging Parameters:
logging
will populate the Activity Log
By default logging is set to false meaning it is off.
Set Simulation Parameters:
simulation_power
Set this to manually test in the console
White this can be a helpful tool for troubleshooting, care should be taken to ensure this is set to 0 during normal operation.
Saving and Executing the Script:
Click the Save Button in the top right next the the Script Name and Play Button
Click the Play Button in the top right next to the Script Name.
5. System Testing
Simulate High Load: Increase the load to trigger the thresholds.
Verify Script Actions: Check if the Activity Log to verify the Load Shedding Script is executing the defined commands.
Adjust Settings: After a satisfactory system test setting should be fine-tuned in regard to the thresholds and actions based on your requirements.
By following these steps, you can effectively use a Script with Shelly Pro 3EM and various Shelly relays to implement load shedding, helping to manage and reduce energy consumption dynamically.