GE Digital Energy provides a unique technology called Redundant Parallel Architecture™ (RPA™) that can parallel Uninterruptible Power Supply (UPS) modules with true redundancy.

With RPA, there is no need for external electronics or switches to control the UPS modules in the parallel system. One of the UPS modules in the system arbitrarily takes a leadership role, while the other UPS modules have access to all control parameters. If one UPS fails to operate, the load is automatically redistributed among the others. If the lead UPS fails to operate then a different UPS automatically takes on the leadership role.

The RPA systems designed to have no single points of failure, ensuring the highest level of power protection for critical loads.

FEATURES & BENEFITS

• RPA Configuration provides complete redundancy of all critical components; allows paralleling of up to eight units for increased load capacity; and ensures excellent dynamic behaviour based on output voltage load sharing. This provides the highest reliability and availability for mission-critical applications.
• Modular design allows for system upgrades to meet future power needs without any interruption to the critical load or transfer to by-pass.
• Easy to install and maintain.
• Scaleable design allows for efficient use of capital.
• Redundant high speed data bus& control electronics facilities fast decision process with high reliability.
• Peer-to-Peer architecture where any UPS can be the “logic leader” ensuring no single points of failure.
• Sequential soft start (during mains recovery) avoids over-rating of the generator, over heating of cable and fuses, and avoids electrical disturbances to other loads connected at the input.
• Intelligent Energy Management™(IEM™) capability for optimal energy utilization of UPS modules in a parallel configuration.

GE's Redundant Parallel Architecture™(RPA™)

A comparative Overview

Multiple UPSs are configuration in a system to either support increase in load capacity and/or to improve reliability. There are several configurations that include multiple UPSs.

PARALLEL SYSTEM WITH AUTOMATIC TRANSFER SWITCH

The parallel system with an Automatic Transfer Switch (ATS) consists of one or more UPS modules with outputs connected by a switch that senses a loss in voltage and transfers the load to a different module or modules.

Pros:

• If one of the UPS modules fails, another unit is available to provide power to the load.

Cons:

• No load sharing
• Additional cost of the ATS
• The ATS is a single point of failure, which if it fails, the load will be interrupted even if utility power is available.
  

PARALLEL SYSTEM WITH PARALLELING CABINET

The parallel cabinet configuration uses an external set of centralized electronics to distribute the load between the system's UPS modules.

Pros:

• No ATS required

Cons:

• Motor-operated breakers replace the function of the ATS. While less expensive than an ATS, they operate much more slowly.
• Failure or malfunction of the shared control electronics will result in a load interruption, which is possible even if the power is present. The shared electronics package is a single point of failure.
• Non-redundant communication links.
• System price is increased because of the additional cost of the shared control electronics and motor-operated breakers.
  

PARALLEL SYSTEM WITH CENTRALIZED LOGIC

The parallel system with centralized logic is basically designed the same as the paralleling cabinet configuration. The difference is that they utilize the control electronics of one 'lead' UPS module to control the distribution of the load between the system's other modules.

Pros:

• No ATS required

Cons:

• If the 'lead' UPS module fails, the remaining units are uncontrolled. The system may go to bypass on all units, or may stop operation completely.
• If the communication link between the lead and other units fails, the load may be interrupted even without a utility power failure.
  

IISOLATED REDUNDANT SYSTEM

The isolated Redundant or hot-standby system uses the bypass static switch of the primary UPS to tie the output of a secondary (stand-by) UPS to the load.

Pros:

• Inexpensive, since no additional components are added to the system.

Cons:

• There are many single points of failure.
• No sharing of the load. If the primary unit fails, the secondary unit must be able to accept a 100% load increase in 8.4 milliseconds.
• Overload capacity is limited to the rating of the static switch of the primary module.
• System MTBF* is typically lower than the MTBF of a single module.

*Mean Time Between Failure