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Are you in tension? If with HRN-100, it's good!

Introducing the latest model HRN-100, now a fully digital voltage monitoring relay that protects devices and equipment connected to a 3-phase network. 

Introducing the latest model HRN-100, now a fully digital voltage monitoring relay that protects devices and equipment connected to a 3-phase network. It monitors the upper and lower voltage and frequency values in 3-phase circuits. Thanks to the LCD display, important parameters can be set within a wide range as required. 
The HRN-100 is a modern 2-module device that can be mounted on a DIN rail.

HRN-100 setting options 

Let's take a look at the programming menu. Already after a quick study it is obvious that almost all important parameters can be freely set within a certain range, so for example:

  • 3 or 4-wire connection (with zero) can be selected
  • the reference voltage can be adjusted so that it can be used almost anywhere in the world
  • gives the possibility to choose the type of asymmetry tracking (absolute or percentage) 
  • 4-wire connection allows monitoring of zero wire breaks
  • has adjustable hysteresis 
  • switch-on delay can be set 
  • display backlight can be switched on or off 
  • the last five fault events are recorded and the history can be viewed retrospectively
  • password protection against unauthorised modification can be set (security is also provided by a sealable transparent cover for the display and controls). 
  • The two output relays can be configured separately (on/off and value setting for each function): 
  • overvoltage/undervoltage 
  • frequency increase/decrease 
  • asymmetry monitoring 
  • phase loss monitoring 
  • phase sequence monitoring
  • Fault delay 
  • delay from fault to "OK" state
  • NC or NO output contact 
  • enabling/disabling the fault status memory
  • the settings of the first relay can be copied to the second relay - this corresponds to a parallel relay connection, i.e. they react to fault events in the same way.

The voltage range Umin - Umax is selectable from 90 - 288 VAC for phase voltage monitoring and 155 - 500 VAC for interphase voltage monitoring. The frequency range for monitoring is 45 - 65 Hz. The delay can be set typically up to 999 s. The sufficiently wide voltage range ensures that the instrument can be used for a wide variety of electrical networks. 

Download the user manual here

3-Wire Wiring 
Figure 2 shows a three-wire connection of the HRN-100, therefore the "N" terminal is left blank and the instrument does not monitor the zero wire break or phase voltage.

The control voltage of the VS463-40/230 V contactor coil, which switches the motor, is connected to the coil by the HRN-100 relay. In order for one of the relay outputs to allow interlocking, the HRN-100 relay setting must use the copy function to allow both relays to operate simultaneously for any selected fault event. If it is necessary to detect, for example, overvoltage and voltage drop separately, the outputs of both relays must of course be connected in series to the contactor coil and the individual relay monitoring functions must be set separately. It is also important that the relays are set to the so-called "Fail Safe" mode, which means that in a network with safe operation they are both in the switched state and will open in the event of a fault.

4-wire wiring 
And we've also drawn a four-wire wiring diagram. In Figure 3, the "N" terminal is also used to connect the neutral wire. In this case, of course, the 4-wire mode must be selected in the menu, and if we really expect the relay to react to a break in the neutral wire, we must also enable its monitoring.


Setting the HRN-100 monitoring voltage may seem somewhat complicated at first, no doubt because of the multi-point menu. We recommend that you do not focus only on the necessary parameters when setting up, but go through the menu items one at a time from start to finish, checking and/or adjusting as necessary. This will minimize the possibility of incorrect or accidental settings. 

We wish you a day without tension - and when you do, only with it in the mains! 

Date of publication: 24. 11. 2021


December 2023
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