Continuous Power: Mobile Generation


Aging infrastructure, compounded by peak season demands, has placed an enormous strain on grids worldwide, thus increasing the risk for potential power outages. The massive T&D infrastructure in North America is aging and breaking down in many areas, keeping utility company maintenance crews busy proactively upgrading infrastructure as well as reacting to expedient repairs. Capital infusion to upgrade T&D infrastructure is forthcoming, but due to the scale of T&D investment needed, the necessary improvements will span a couple of decades, rather than a couple of years. In addition to major T&D improvements, utility companies must also carefully balance capital investment on “clean” power sources as they divest from baseload power sources, such as coal.

Further, it was noted at a recent industry seminar that by 2020, North American electric utilities will add 48 GW of solar-based energy and 65 GW of wind-based energy, further increasing the urgency to upgrade and expand T&D grids.

Natural disasters such as the recent Hurricane Maria, one of the strongest ever to hit Puerto Rico, can cause unprecedented damage to an already fragile power grid. An unfortunate, but relevant example, just four weeks after making landfall, roughly 79% of Puerto Rico still doesn’t have electricity.

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A host of new, less traditional challenges are also taking center stage which could impact grid stability: rising cybersecurity threats; more demanding consumers; an influx of unpredictable renewable sources; and, with the shift toward distributed generation, an increasing number of innovative competitors and the growing popularity of “behind the meter” (BTM) onsite generation sources.

Rental Power
Many utility companies are turning to mobile power generation to ensure continuous service to customers during planned and unplanned outages. However, once the decision is made to employ mobile power generation as a cost-effective solution, the next question becomes “is it better to rent or own generators?”

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Aggreko equipment onsite to support PG&E power needs in Northen California

While ownership is often assumed to be the better choice, cost analyses consistently show that rented power generation equipment produces a better return on investment.

Because each situation addressed by mobile power varies greatly, and therefore requires different engineered solutions and equipment, utility plant owners’ inventoried generators rarely meet every need.

All too often, purchased equipment is deployed once, stored, and then found either unsuitable for the next need or is long-forgotten in a warehouse, producing no long-term value to the purchaser.

Additionally, seldom-used owner equipment typically does not receive the appropriate maintenance or safety and emissions testing that rental fleets routinely undergo.

Because fleet management is a core competency of a power generation rental company, technician training, parts management, fleet availability, and highly responsive service crews add significant value to the rental alternative when the true cost of ownership is calculated.

Rental power generation providers can get equipment into place very quickly to meet a utility’s load requirements. These engineered solutions help utilities improve customer service by keeping customers energized while planned work is performed or restoring power more quickly during an unplanned outage.

When considering a mobile power generation solution, it is important that the temporary power system is interconnected to the grid matching the specific requirements of the project. Each temporary generation project is unique and has different needs, so there is no such thing as “one size fits all.” Therefore, it is critical to work with a third-party generation provider that has in-house technical expertise, such as electrical engineers, that understand how to design a power system that can seamlessly tie into each utility’s infrastructure and adhere to unique grid interconnection processes.

PG&E Reduces Outages
 Utility companies worldwide are benefitting from the many advantages mobile power generation provides, from capital avoidance to improved customer service, and emergency response plans.

PG&E leverages robust portable generation systems by Aggreko for continuous power support while performing improvements to power lines and substation equipment. One such project recently took place when a 7-MW/12-kVA power generation solution energized more than 1,500 PG&E customers in San Luis Obispo County for 13 hours while upgrades were completed at the Cholame substation. Without the use of portable generators, customers in the San Luis Obispo County area would have experienced a “planned” outage for several hours while this work was being performed.

In a typical scenario, medium voltage lines put up 60 years ago must be upgraded because they are undersized to meet current demand. The preferred option is to perform the upgrade without taking customers offline.

It has been typical during such upgrades to take customers offline for incremental periods until the project is completed, increasing the utility’s Customer Average Interruption Index (CAIDI). However, whether the end user is industrial, commercial, residential, a combination of these, or a new type of electrical consumer, such as an urban medical center, any planned or unplanned offline incident is unacceptable, even for short increments, no matter how much notification the utility provides. For these constraints, PG&E can now provide temporary power and avoid interrupting customers’ services. In addition, PG&E can use portable generation systems for both large- and small-scale projects.

Because PG&E serves a large area where unplanned events such as earthquakes and large wildfires can’t be prevented, it also sees portable power as a way to restore service faster during unplanned outages.

Portable generation projects demonstrate the importance of optimizing strategies for staging crews and equipment in heavily impacted areas. Whether the requirement is for 1 MW or 100 MW, these temporary power projects validate the mobile distributed power plant concept’s ability to deliver repeatable and scalable solutions. PG&E’s efforts to modernize an aging grid sooner rather than later is why the utility sought outside expertise to resolve this challenge.

Unplanned outages cannot be controlled, but in the many instances where infrastructure needs to be upgraded or repaired, a portable system can be built reflecting a distribution-level power plant. The portable infrastructure consists of generators, distribution equipment (stepped up to the utility’s line voltage), and protective devices. Switchgear and the protective measures necessary to ensure synchronization with required voltage and frequency (12 kV, 60 Hz) are included.

If there is a fault in the line, for example, protective systems (relays, breakers, etc.) ensure the temporary service remains capable of disconnecting from the grid, if necessary. In many cases, the lead time is needed until the utility’s new assets (transformers, etc.) are delivered and energized. Other examples include sections of distribution lines that are at overcapacity and that overcapacity can be alleviated with temporary power until adequate resources are available to upgrade the line.

Mobile power generation can be interconnected to the grid at almost any location to keep customers energized. The time required to commission a temporary power project is largely dependent on factors such as project size, terrain, proximity from a service center, weather, and available space. A typical 10-MW medium voltage power project, for example, would take five to six days to fully commission and test before being ready for operation, and about half of that time to fully decommission.

Whether in PG&E’s or some other utility’s service territory, most customers no longer tolerate power outages. Numerous utilities are calling on temporary generators to restore power more quickly in response to unplanned outages. Whatever the application, temporary power solutions are utilized nationwide to help electric utilities provide reliable service to their customers. De Bug Web

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