Electronic Load Controller / Protection Relay

Hydrocontrol - the flexible and communicative ELC

Electronic Load Controller (ELC) / Protection Relay/ Induction Generator Controller (IGC)

60kW Unit

Build your own ELCincluding ELC circuit diagram schematic - open source

For hydro power generators in off-grid / island operation. An ELC keeps your mains frequency stable. With an unstable frequency, electrical equipment can malfunction, get damaged and reduce its lifetime.A protection relay disconnects the power in an emergency situation in order to prevent damage to user equipment and the hydro system.

Features for the user

    • Very flexible - works for a wide range of installations,
    • with lots of options
    • Flexible handling of different dump load sizes and load priorities.
    • Easy adjustment on site due to microcontroller technology
    • P-I autotuning (beta).
    • Reliable - proven technology
    • Can be remote controlled via mobile phone network and SMS text messages.
    • The HydroControl can also send status information via SMS text messages.
    • The configuration can be stored on a SD memory card. In case of replacement, simply load the last configuration. Or transfer settings to another site.
    • If the system shuts down, the controller stores the fault/shutdown reason in memory for easy fault tracing.
    • Easily customizable for individual needs.

Technical specifications

    • Voltage nominal:
    • 110 - 130V (3 phase Line-Line: 190V - 220V) or
    • 220 - 250V (3 phase Line-Line: 380V - 430V) or
    • 400 - 430V
    • Frequency: 50/60 Hz (adjustable from 45 - 64 Hz)
    • very precise frequency measurement: +- 0.04Hz ( +/- 0.08%)
    • Power: from micro scale (few 100 watts) to medium scale (megawatts)
    • Phase: 1 or 3 phase
    • Generator: Induction generator (asynchronous) or synchronous generator

Protection Features

Overvoltage, Undervoltage

Overfrequency (overspeed), underfrequency (underspeed)


Overheating: freely configurable temperature sensors, e.g. to monitor roller bearings or generator temperature.

Every dumpload is protected with a fuse.

Optional: Lightning Protection

Metering on the display:

    • AC Mains Voltages for all 3 lines (TRUE RMS and peak, 100 samples per line per period, 1% accuracy)
    • Frequency
    • Current for all 3 lines
    • Temperatures
    • DC Voltage 12V or 24V, if present
    • Hour counter


    • Control water valves
    • Control main user relay / main contactor in case of fault
    • Connect 3 - 48 dumploads
    • Use any dumpload size (as long as they are resistive loads).You can mix different sizes.
    • Star wiring (Y wiring) or Delta wiring (Δ wiring) possible.
    • 3 Phase: line load balancing
    • Warning signal for users, if there is no remaining system capacity
    • Automatically switch low priority user loads, depending on available system capacity
    • choose between zero crossing and phase angle switching
      • zero crossing:
      • does not create RF interference/noise and does not distort the sine waveform, but is a bit slower in regulation -> maximum deviation from setpoint, if big user loads are switched, is a bit bigger.
      • phase angle regulation:
      • fast regulation, but can introdue RF-Interference and waveform distortion, especially if there are few dumploads connected.


Up to 5 mechanical SPDT relays on the PCB. They are low power auxiliary control relays. You will need to install power relay(s) for motors etc. The auxiliary relays will then control the power relay for the motors or other gear.

Relay functions (assignable):

    • Control water valves, also spear valves, to automatically achieve maximum power output
    • control user mains contactor
    • switch pumps, heaters etc. if a defined amount of power is available.
    • switch a warning lamp, horn etc.
    • in case of failure, switch to a second, redundant AVR or generator

Features for the engineer

    • Simple to use, simple to repair
    • Standard components -> cheap to repair
    • Flexible: from micro hydro scale (few 100 watts) to medium scale (megawatts)
    • Customizable: simply change the software to add features and behaviour
    • In circuit serial programming ICSP via USB: firmware update on site possible, only a laptop and usb cable are required
    • No flywheel necessary: if there are oscillations, adjust the P-I regulation speed with the help of live graphs on the screen.
    • Password-protected settings
    • Anti-windup limiter for the P-I controller
    • DC component suppression while switching the dump loads on the AC line
    • Every dumpload channel is monitored. A faulty triac, dumpload or circuit breaker will be indicated.

Modular Design:

    • Get only the microcontroller unit and connect your own SSRs or triacs
    • Get the base unit for up to 35 kw and 12 dumploads, and connect your own additional SSRs / triacs if needed
    • Get a customized unit, with the specified amount of dump load connections, pre-wired in a switch cabinet

Operating conditions:

The heatsinks must be free ventilated, maximum ambient temperature 45° Celsius.

Microcontroller operating range -55 C to 125 C

If the heatsinks/triacs get to hot, the HydroControl will try to shut the water off to prevent damage (if electrical water valves are installed). The ballast loads will never get shut off, in order to prevent overspeed damage to the overall system.


Standard inputs

- 3 phase Mains voltage, 3x line and neutral

- frequency is calculated from the zero crossings of the 3 lines

Power outputs

The power outputs are calle channels. The configuration of these channels can be adapted to your needs.

Triac channels can swith 16A

SSR channels can switch 32A

Contactors can switch up to 300 A

Optional additional inputs and outputs

Auxiliary control/switching outputs

- 4 or 8 mechanical relays, e.g for controlling motorized valves or high power contactors

Sensor inputs

- temperature monitoring. e.g. temperature of triacs, heat sinks, air flow, bearings, water tanks

- DC voltage monitoring, e.g. for 12V system or 24V system

- hard wired inputs to evaluate the status outputs of AVR like the MeccAlte UVR6

Communication connections

- WiFi WLAN over Serial1

- Ethernet over SPI

- GSM over Serial1

- additional Serial UART, I2C, SPI

Example alternative usages

Protection Relay

Use the microcontroller unit in parallel to an existing ELC, to monitor the system. In case of fault, the microcontroller unit can do any/all of the following:

    • turn of the water
    • disconnect users
    • engage a mechanical brake
    • connect dumploads to slow down the system
    • connect a second generator
    • send an SMS text message

Automatic User load switching

If you have low priority user loads in a different location than the main ELC, use only the microcontroller unit to automatically switch these loads on an off, depending on available power. Or use SMS.

Backup ELC

Use it in parallel to the main ELC, but set the frequency a bit higher. If the main ELC fails, the backup ELC will kick in.

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60 kW unit - click to enlarge

35 kW Unit - click to enlarge