Data Center's Redesign Saves Money, Time

At its 20,000-sq.-ft. data center in Dallas, J.P. Morgan Chase handles an array of global financial services—with mission-critical requirements.

Four 1,500-kW diesel generators operate in parallel on a common bus at the center. Two UPS systems, each consisting of two 375-kVA modules—with the ability to expand to four each—also operate in parallel on a common bus. Each UPS system feeds nine redundant 125-kVA static-switch power distribution units (PDUs).

A switchgear parallels the four diesel gensets, which are for standby power. A key software component allows facility operators to remotely monitor, control and even troubleshoot the gensets.

Lead times for orders of wet-cell battery strings were running at 28 weeks. Creative project scheduling led to immediate delivery of four strings of wet-cell batteries for the data center, but this meant keeping the batteries at a storage facility with the proper environment until needed.

Additionally, all switchgear requirements were bundled under one manufacturer. This required a new relationship to be forged between the switchgear and UPS makers.

Initial system requirements for the paralleling switchgear came up with a short-circuit rating of greater than 100 kiloamps interrupted current (kAIC)—not a "standard" rating—meaning longer lead times. The problem was solved by engineers who redesigned the switchgear to a lower kAIC rating that would still meet the data center's needs.

Reactors were installed in the neutrals of the diesel generators to limit their fault-carrying ability. A bus tie-circuit breaker was designed into the diesel paralleling gear. By controlling this breaker during any overlap transfer, the fault-carrying ability was limited. What's more, achieving a lower kAIC rating lowered the system's overall purchase price.

New generators had lead times of up to 20 weeks. Initially, the generator package included two refurbished generators and a new one—all three gensets sized at 1,750 kW, with the customer option to add a fourth. With Texas on the verge of utility deregulation, the firm was encouraged to look at the feasibility of exporting power back to the utility grid and set up its system to allow for that option.

As a result, the system design was switched to include the four 1,500-kW engine generators—with the supplier guaranteeing delivery dates. And the use of 1,500-kW, instead of 1,750-kW, units was another cost savings.

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From Pure Power, Spring 2002.