Wind Turbine Design Studying

Two key factors required for wind farm development at the site prospecting phase and which one is more important?

Wind and transmission. A project must have a good wind resource and adequate transmission capacity. A low wind speed site with a great transmission plan is better than great winds and poor transmission. With a great wind resource, the project can afford extra costs for transmission upgrades and interconnection challenges.

Name three agencies that you would work with to develop a wind farm

1. Federal aviation administration (Federal) 2. Department of fish and wildlife (state and/or federal) 3. department of transportation (state), army corp of engineers (state and/or federal)

What is a typical max tip height of a wind turbine in the us and why?

500 ft or 150m to account for FAA regulations and faster approval. The industry has achieved approval for tip heights up to 699 ft and beyond, but approval process can be extended to greater than 3-6 months.

What technical parameter would you evaluate before going forward with a taller tower?

Wind shear. It is used to evaluate the energy at the hub height and will help developers and engineers to determine if there is sufficient wind at higher hub heights.

What other constraints would impact a decision on tower height?

Transportation and delivery logistics, local bird and bad species, noise impact on community, and visual impacts for local community, and possibly more.

List 3 technical grid requirements that will be defined during the transmission and interconnection phase of wind farm development.

Reactive power, adequate design for short circuit ratio, protection against sub synchronous resonance, frequency range, voltage range, low voltage and high voltage ride through, SCADA/communications

When would you start the interconnection process and when is it typically complete compared to other development tasks?

The interconnection process starts as soon as you begin to invest any time or money in the development and following any fatal flaw studies. The process starts with electrical grid modeling and determination of the preliminary design of the wind farm. Then the interconnection application is submitted to hold a place in the queue for utility or ISO evaluation of your facility. Following the feasibility, system impact, and facility studies, the interconnection agreement can be executed. The interconnection agreement process will happen in parallel with permitting and power purchase agreement planning but prior to notice to proceed for construction.

SCADA

Supervisory Control and Data Acquisition. A centralized computer system combining software and hardware that monitors, controls, and analyzes wind turbines and site infrastructure in real time.

Provide a list of primary topics that you would focus on if you were the operations manager of a wind farm

1. develop an operations and maintenance plan for all major systems on the site; wind turbines, substation, gen-tie line, roads, rivers/wetlands, collection system, & O&M building.

2. create a complete list of safety and operating procedures for all standard work performed.

3. develop a training plan and requirements for all site staff, visitors, contractors, and emergency response teams.

4. generate a tools list for all in-house work and procure tools.

5. determine the top list of contractors that will be needed to support your operating site.

6. establish an effective spare parts list for all major systems and procure these parts based on lead time.

What are the differences between step and touch potential?

Step potential is a condition that is created when the ground becomes energized due to an electrical fault or lightning strike to a nearby object. In the ground, there is a voltage difference between concentric rings around the grounded object. If a human steps across the concentric rings, then a voltage difference is created from one foot to the other foot causing current to flow through the body.

Touch potential is a condition that is created when a human touches a grounded object while standing on uninsulated earth. this can create an alternative path to ground. during the time of contact, a voltage could be applied to the grounded object due to an electrical fault or lightning strike. therefore, current can flow through the body.

the difference between them is one is created by touching an electrically grounded object during a fault while standing on uninsulated earth and one is created by taking a step on uninsulated earth while in the vicinity of an electrically grounded object. Both involve grounded objects, and both involve contacting these grounded objects at the time of an electrical fault which could cause current to flow through the human body.

What PPE would you wear every day on a wind farm?

Hard hat, safety glasses, high visibility vest, steel/composite toed boots

What are some features added to the roads and each turbine location to account for crane movement and turbine delivery?

• Compacted roads with sufficient gravel to distribute load

• compacted shoulders to allow for the crawler cranes to walk from turbine to turbine on the road pathway

• sufficient area of compacted and finished gravel in roadways to account for turning radius and entrances

• turbines at the end of roads should include around areas for turbine delivery and equipment

• turbines should be located off the connector roads just far enough to allow for turbine installation to occur while not impeding traffic for other construction activities

• crane pads should be designed for the exact crane that is expected

• there should be sufficient area to maneuver turbine delivery trucks around the turbine to position the components per the lift plans

What is the main communication cable used between wind turbines? (SCADA)

Single mode fiber optic cable

Provide one critical device in the SCADA system and summarize how it is used?

• Remote Rerminal Unit - real time automation controller if made by SEL, this is the data concentrator for the site. it manages data coming from internal devices and external parties and distributes data and alarms as requested by other devices. certain models can also provide HMI capabilities through a built in server

• Firewall - manages all cyber security functions to prevent unauthorized external parties from accessing critical data and functions.

• Master controller - provides all wind farm control of active power, reactive power, voltage and frequency to receive external and internal set points for distribution to each wind turbine, cap bank, reactor, DVAR, or other generation equipment

• SCADA server - provides data collection and recording of internal and external data. Can provide HMI capabilities for easy access and use of the data and system manipulation

• Switch - a device that connects different computing devices on a network. a managed switch or multilayered switch can also perform routing capabilities

What is a typical protocol used to communicate data between devices on a wind farm?

Modbus TCP/IP

Provide all inputs for cashflow analysis

• CapEx = wind turbine costs + BOP costs

• OpEx = operating wind turbine costs

• Production = annual energy production for the entire wind farm

• Depreciation Schedule = for tangible assets ( cash, property, equipment )

• Amorization Schedule = for intangible assets (goodwill, trademark, IP rights)

• Production Tax Credit Schedule

• Discount rate = interest rate

• Inflation rate

• Tax rate

• Life of the project

• Number of wind turbines on the wind farm

What are major steps tot take to perform an economic evaluation for turbine selection?

• confirm the wind farm preliminary design is complete

• select a group of possible wind turbines to evaluate

• model and calculate the annual energy production for the site with the selected turbines

• request wind turbine, construction, and operations pricing

• evaluate equipment, construction, and operations costs to confirm all features/services are included

• develop the economic spreadsheet with all the inputs highlighted above and calculated cashflows

• calculate NPV (net present value, want to be high) and LCOE (levelized cost of electricity, want to be low) to determine your top turbines

what is the thrust coefficient and how would it impact energy yield?

Thrust is the force on the disc created by the swept area of the rotor blades. The thrust coefficient is a non-dimensional number that ranges from 0 to 1. As wind speed increases, thrust increases until the turbine rated power is reached. Then thrust decreases as wind speeds increase in order to reduce loading on the turbine while continuing to produce rate power. energy yield is affected by the thrust coefficient through fine tuning of the control system.

What is a series compensated transmission line and why does it cause SSR?

have reactive power elements to help reduce inductance in the lines and generally increase stability. these reactive elements can introduce disturbances to the entire system, including the wind farm. these disturbances can cause resonance with the mechanical and electrical conversion components of the wind turbine, exciting the first natural mode of the system.

Why is a low SCR (short circuit ratio < 5) a problem for wind turbine suppliers?

Low SCRs are indicative of a weak grid. weak grids can cause large fluctuations in reactive power being injected into the wind turbine that are difficult for the power electronics in the turbine to handle.

What are two common types of generators used in wind energy production?

1. synchronous/doubly fed induction generators

2. asynchronous/squirrel cage induction generators

How do you control reactive power?

by controlling voltage and the power factor.

How do you control frequency?

active power is used to control frequency on the grid.

What are the steps you would take to develop a SCADA architecture?

1. review the SCADA technical specifications from client, major equipment suppliers and grid operator.

2. review the electrical design to determine which devices will require monitoring and controls

3. develop physical network design to successfully interconnect devices

4. assess the need for media and protocol converters

5. create a SCADA hardware list

6. generate a draft of the SCADA architecture for internal and external review and comments

What is a fiber ring network vs. lateral connection and why would you choose one over another?

fiber ring network connects all equipment into a loop where a lateral connection is set up for a single path to each piece of equipment. a ring configuration allows for redundant communication paths to maintain data when one path has failed. a lateral connection can be easier to install and less expensive.

What is the importance of a data concentrator or RTU in a substation?

the data concentrator or RTU manages all of the data from field devices. the SCADA system utilizes the RTU to coordinate signals both internally and externally. each substation will have an RTU.

What is attenuation in a fiber and what are some typical wavelengths and losses for multi-mode and single-mode fiber?

attenuation is the reduction of signal amplitude. signal loss can come from fiber scattering, bending, connectors, and more. multi=mode utilizes typical wavelengths of 850 nm and 1300 nm and single mode fiber utilizes 1310 and 1550 nm.

crosswind spacing

4-6D

downwind spacing

8-12D

Assuming the MV cable trench runs next to the road, what are some design elements to consider for the MV collection system

• county and state codes and standards (electrical constraints)

• local freeze line and potential digging/plowing impacts (depth of trench)

• thermal and electrical resistivity of the native soil and subsoil (cable protection and grounding constraints)

• circuit spacing within a trench or between trenches (electrical constraint)

• ampacity/voltage drop/losses (cable selection)

• backfill material selection (cable thermal impacts)