Configuring distributed redundant UPS systems

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A distributed redundant UPS configuration can be used as an inexpensive way to obtain complete redundancy as it is less expensive than a 2N architecture. It is usually chosen for large multi-megawatt installations where concurrent maintenance is a requirement and space is limited. It involves 3 or more UPS modules with independent input and output feeders. The critical load is connected through multiple PDUs. In some cases, STS are also used.

For further information about UPS System Design Configurations, see White Paper 75.

IT Advisor allows you to model all distributed redundant UPS design configurations mentioned in the white paper.

Distributed redundant "catcher" UPS configuration

This configuration includes 3 UPS modules in a distributed redundant design that could also be referred to as a "catcher system". In this configuration, module 3 is connected to the secondary input on each STS, and would "catch" the load upon the failure of either primary UPS module. It is only supported to have one "catcher" UPS per "catcher system" and it must be unloaded. Otherwise, you should set up a distributed redundant UPS configuration as described below.

Configuration:

1. Add UPS modules, PDUs, STS, and racks to the floor layout as illustrated.
   For the STS, add ATS from Genomes, right-click them and rename them STS.
2. Add servers and rack PDUs to the racks.
3. Configure the power paths.
   1. Right-click the UPS modules one by one and select Properties>Power to set up redundancy feeds.
      1. For UPS 1, select "With Catcher" (Distributed Redundant).
      2. For UPS 2, select "With Catcher" (Distributed Redundant).
      3. For UPS 3, select "Catcher" (Distributed Redundant).
   2. Connect all equipment to the power paths (see tip below).

In normal operation, UPS 1 and 2 carry the full load.
In case of a failure of either UPS 1 or 2, UPS 3 catches the load of the failing UPS.

102239844_360038495393.png

Distributed redundant UPS configuration (with STS)

This is a distributed redundant design with three STS and the load evenly distributed across the three modules in normal operation. The failure on any one module would force the STS to transfer the load to the UPS module feeding its alternate source.

Configuration:

1. Add UPS modules, PDUs, STS, and racks to the floor layout as illustrated.
2. Add servers and rack PDUs to the racks.
   1. Right-click the UPS modules one by one and select Properties>Power to set up redundancy feeds, all Distributed Redundant.
   2. Right-click the STS one by one and select Properties>Power Dependency to set up primary and secondary connections.
      1. Set the primary load so each UPS carries its own load.
      2. Set the secondary load so the UPS modules alternately catch the load for each other in case of a failover.
   3. Connect all equipment to the power paths (see tip below).

In normal operation, the load is evenly distributed across all 3 UPS modules.
In case of a failure of any of the UPS modules (but only one at a time), the load gets transferred (failover) to the other UPS modules.

102239837_360038495393.png

Distributed redundant UPS configuration (no STS)

As the quantity of single-corded loads in data centers today are becoming fewer and fewer, it is becoming more practical and less costly to apply multiple, small, point of use transfer switches close to the single-corded loads. In cases with 100% dual-corded loads, this configuration could be designed without STS units. This design is typically known as a tri-redundant and uses no static transfer switches.

Configuration:

1. Add UPS modules, PDUs, and racks to the floor layout as illustrated.
2. Add servers and rack PDUs to the racks.
3. Right-click the UPS modules one by one and select Properties>Power to set up redundancy feeds, all Distributed Redundant.
4. Connect all equipment to the power paths (see tip below).

In normal operation, the load is evenly distributed across all 3 UPS modules.
In case of a failure of any of the UPS modules (but only one at a time), the load gets transferred (failover) to the other UPS modules.

102239813_360038495393.png

Tip

Use different colors for the power paths to visually distinguish between them. (Right-click on the UPS, select Properties>Power>Power Path Color.)

The Power overlay tool tips displaying when you hover over equipment in racks provide a visual overview of the load distribution and redundancy settings.