Relay Controlled Fuse Groups

Overview

A Relay Controlled Fuse Group is a specific type of functional group that includes a fuse, a switch, and a relay. There are two different fuses required: one outside and upstream from the group (referred to here at the main fuse) and the fuse inside the group, referred to as the controlled fuse.

The image below displays a typical example.

Figure 1: Relay Controlled Fuse Group Example

Relay Controlled Fuse Group Conditions

The following conditions must be met for the group to be valid:

  • There must be a main fuse upstream from the controlled fuse, with no more than two buses between the main and controlled fuses.
  • The main fuse must be set to a device library style that has the Relay Controlled Fuse Group check box selected. In addition, the model must be set to the first model for that style. See Relay Controlled Fuse Group Settings.
  • The fuse group must contain a fuse (the controlled fuse), a switch, and a relay.
  • The fuse that is inside the group (the controlled fuse) must be set to a device library style that has the Relay Controlled Fuse Group check box selected in the library. In addition, the model cannot be set to the first model for that style. See Relay Controlled Fuse Group Settings.
  • The controlled fuse and the switch must be in parallel to each other.
  • The relay must be downstream from the fuse and switch.
  • The relay must have at least one phase or maintenance phase type function that points to a valid CT. This is set up in the Relay Data dialog box, on the Specifications tab, under the Dev Fctn Type and CT columns.
  • There must be at least one bus downstream of the CT.
  • All of the items must be connected and active.

You will receive a warning if you open the Coordination focus and the required conditions for the functional group are not met.

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