Large renewable energy projects typically involve the addition of one or more new substations. Collection substations and even the main substation may be in remote or difficult to access locations. In some instances, the substations are on leased land and whether leased or purchased substation space is always at a premium. Additionally, projects may be on farmland or other sensitive areas and environmental image is very important. The attributes of modern digital substations make them the perfect choice for renewable energy project applications.
Developers have considerable latitude when designing collection substations within projects and a major role in designing the main interconnection substation for renewable projects. Matters surrounding the interconnection substation may see greater involvement by the host utility during both design and operation. While most utilities are migrating to digital systerms for new installations and are well aware of their benefits, developers also should be aware of digital system advantages when making technology selections. Accordingly, it’s worth a quick review of digital substation advantages and how they can benefit renewable energy projects. Digital substations exhibit the following traits according to manufacturers such as ABB:
- A reduction in copper cable by up to 80%. Intelligent Electronic Device (IED) control wiring is replaced by fiber optic communications between IEDs. This reduces material cost, transportation cost, construction time and independent connections that can later require maintenance.
- Space requirements are reduced by 30 to 60%. This includes reduced space for protection and control panels, conventional IO’s and CT/PT inputs. On the primary side, the reduction of the switchyard footprint can be up to 50% using circuit breakers with integrated disconnecting functionality and optical current sensors. Very importantly, the use of nonconventional instrument transformers (NCITs) means the elimination of large pieces of oil filled equipment.
- A high percentage of standardized and factory tested panels and components which contribute to shorter manufacturing and customization lead times and greater flexibility to modify the system late in the development/construction cycle.
- Less installation and outage time. The installation time for new protection and control systems can be reduced as much as 40% with corresponding reductions in feeder outage time.
- Increased safety. Personnel safety is improved since copper control wires and conventional instrument transformers are replaced with fiber optic communications and optical measurement devices.
- Effective and easier maintenance through automatic monitoring. Sensors, electronics and software monitor the status of the primary and as well the secondary devices of a substation for the optimization of maintenance activities.
Each of these benefits is significant for any project, but the synergy is quite relevant to renewable energy projects. The benefits of reduced space and construction time means reduced impacts to property owners, less permanently altered land and potentially reduced road construction which may otherwise need to be removed after construction. NCITs and digital buses mean greater safety and reduced potential for oil spills. The automatic monitoring and diagnostics in digital substations is highly beneficial for renewable projects which may be remote and have reduced staffing. At the same time, digital systems can be expected to achieve greater reliability and availability, both of which are critical to renewable energy projects. Bottom line: when going green also consider going digital.