Can Macromatic’s Three-Phase Monitor Relays Be Used with Open Delta Systems?

Three-Phase Monitor Relays

Issue: 

Can Macromatic’s Three-Phase Monitor Relays be used with open delta systems?

Answer: 

Yes, by following a few simple guidelines.

Here is an open delta schematic:

Open Delta system schematic using Macromatic Three-Phase Monitor Relay
  • The phase monitor needs to connect to A,B,C….not GND or Neutral
  • Select the correct phase monitor using the Phase to phase voltage of the power system, not Phase to neutral or ground voltages.
  • Ensure that Actual Unbalance is within the acceptable range of the phase monitor relay selected for proper operation or use a relay that does not provide unbalance protection. Open delta systems are predisposed to higher levels of unbalance.