What type of power systems can Macromatic relays protect?

Tuesday: June 11, 2019 : Three-Phase Monitor Relays


Question:

What type of power systems can Macromatic relays protect?

Answer:

Macromatic devices work on many systems. Here are the descriptions, recommended connections and guidelines for Corner Grounded, Open Delta and High Leg (Red Leg, Wild Leg) Delta systems. Contact Macromatic for technical information on other systems.

Corner Grounded Delta System

Macromatic 3-phase monitor relays provide reliable protection on corner grounded delta systems.

A corner grounded delta system is a common way to establish a reference to safety ground when dealing with an otherwise floating output from a delta secondary transformer. It is implemented by grounding any one of the three phases of the transformer secondary (corners of the delta).

  1. The phase monitor relay should be connected to phases A, B, and C; there is no separate connection for ground (GND) on the phase monitor, but one of the phases will be physically connected to ground.
  2. Use the Phase to phase (not Phase to neutral) voltage level of the power system, and your specific protection requirements, to select the correct phase monitor relay for your application. Read more>

 

Open Delta System

Macromatic 3-phase monitor relays provide reliable protection on open delta systems.

  1. The phase monitor relay should be connected to phases A, B, and C; there is no connection to ground (GND) or Neutral.
  2. Use the Phase to phase(not Phase to neutral) voltage level of the power system and your specific protection requirements to select the correct phase monitor relay for your application. Read More>

Note: Consider selecting a phase monitor relay that includes the ability to adjust the voltage unbalance trip point or does not provide unbalance protection; open delta systems are predisposed to high levels of voltage unbalance not common in other types of 3-phase power systems.

 

High-Leg (Red Leg, Wild Leg) Delta System

Macromatic 3-phase monitor relays provide reliable protection on high-leg delta systems.

A high-leg delta system (also commonly called red leg and wild leg, among others) is a common configuration involving a delta transformer secondary having one winding center tapped with neutral and grounded. It is commonly used to provide two 120V AC and one 208V AC circuit with reference to neutral although other voltages are possible depending on the phase to phase voltage on the secondary windings.

In order to apply a phase monitor relay in this installation, it is important to realize that despite the 120/208V AC circuits available with reference to neutral, that the phase to phase voltage is actually 240V AC on each of the three phase pairs (Vab, Vbc, Vca = 240V AC).

If your high-leg delta system operates with different system voltages, simply take the high-leg voltage and multiply by 1.15 to get the approximate phase to phase voltage used for selecting and configuring your phase monitor relay.

  1. The phase monitor relay should be connected to phases A, B, and C; there is no connection to ground (GND) or Neutral.
  2. Use the Phase to phase (not Phase to neutral or ground) voltage level of the power system, and your specific protection requirements, to select the correct phase monitor relay for your application. Read more>

Note: consider selecting a phase monitor relay that includes the ability to adjust the voltage unbalance trip point or does not provide unbalance protection; high-leg delta systems are predisposed to high levels of voltage unbalance not common in other types of 3-phase power systems.

 

©2019 Macromatic Industrial Controls, Inc.

W134N5345 Campbell Drive
Menomonee Falls, WI 53051

800-238-7474 • 262-781-3366

Rep Login | Newsletter Sign Up | Articles | Employment | Privacy Policy | Sitemap
Knowledgebase General | Alternating Relays | Current Sensing Relays | Intrinsically Safe Barrier Relays | Liquid Level Control Relays | Seal Leak Relays | Three-Phase Monitor Relays | Time Delay Relays | Voltage Monitor Relays