What makes Linden different
The Linden site, just east of the New Jersey Turnpike in an area replete with petrochemical plants, didn't provide a lot a room for the repowering project. The back side of the property is the Arthur Kill, the body of water from which the old plant drew its makeup water. It's only about 40 feet from the new plant's cooling towers, water treatment plant, and demin water storage tanks to the banks of the Arthur Kill.
The compactness of the site necessitated an unusual placement of the plant's prime movers and unique piping geometry as well. In a typical 4 x 2 plant (where there's enough room), the two gas turbines (GTs) and one steam turbine (ST) of one power block and the two GTs and one ST of the other are all laid out in a row. At Linden, at one end of the centerline are two GTs and two STs (one in line and the other offset), with the two remaining GTs at the other end. In other words, the configuration is wide rather than long (as the orientation of the white buildings—the power blocks—in Figure 1 makes clear).
Another consequence of the footprint constraint is that Linden has more bizarre piping geometry than all but perhaps six other plants worldwide (Figure 3). The dearth of standard bends and straight piping runs, and the need to have more piping bends than sweeps, raised the cost of construction a bit.
3. Do the twist. An example of the kind of extreme piping bends necessitated by Linden's limited site footprint. Courtesy: PSEG Power
Another unique aspect of Linden is the placement of its control room. At a typical independent combined-cycle plant, the control room is in a different building than the power blocks. Usually, it's at grade in the same building as the warehouse. At Linden, the control room is on the third level, at about 75 feet elevation, between and on the back side of the power blocks (Figure 4).
4. Upstairs, downstairs. At Linden, the control room is located on the third level, between the power blocks. Courtesy: PSEG Power
The control room was located there due to the footprint constraint. Though its location improves operators' access to the steam turbine, valves, and piping at that level, it does necessitate longer trips when making visits to rotating machinery two levels below.
The final, unique aspect of Linden has to do with its location. The plant is connected to two transmission grids of different voltage: 138 kV and 230 kV. In Unit 1, one gas turbine is on the 138-kV system and the other is on the 230-kV system. The unit was split that way to use the injection rights of the old plant. Unit 2 is connected only to the 230-kV grid. PJM uses different pricing mechanisms to pay Linden for the two capacity injections into its grid.
Perseverance pays off
The final (and perhaps most notable) aspect of the Linden plant is that more than five years elapsed between the laying of its foundation and its commercial operation, which began in April 2006.
At Linden, the consequences of leaving equipment (Table 1) exposed to the environment for extended periods of time due to construction delays was far worse than they would have been at a desert site, because the plant is surrounded by a saltwater marsh and is prone to high-humidity conditions.
1. Key suppliers to the Linden project. Source: PSEG Power
Having never dealt with construction of a plant whose site is exposed to salt water mist, PSEG didn't realize the extent of the corrosion until preparing to run the equipment. As a good utility practice, PSEG decided to inspect the majority of the station's rotating equipment to mitigate any possible impacts of the extended construction delay. All major pumps—including the circulating-water pumps—were removed, inspected, and returned to original equipment manufacturer (OEM) specifications. All of the GE prime movers were inspected and reconditioned to OEM specs as well. This paid huge dividends for Linden, whose performance has been exceptional since beginning commercial operation in late April of this year (Table 2).
2. Linden Generating Station's key performance indicators (YTD as of May 31, 2006). Source: PSEG Power
Linden was originally scheduled to be commissioned in the third quarter of 2002. Although some basic systems were validated in 2004, commissioning didn't begin in earnest until 2005. Necessary tasks weren't done at the typical 80 hour/week pace because, at that point, the project had become more cost- than schedule-driven.
If there's a moral to Linden's cautionary tale/success story, it's this: Given enough time and money, you can achieve the desired results by learning from your mistakes.
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