Greenbyte Documentation

Time-Based Availability

Time-based availability is calculated as

Equation 1. 
At=(1-TuTa+Tu)x100 A_t=\left(1-\frac{T_u}{T_a+T_u}\right)x100


where:

At is the availability

Tu is unavailable time

Ta is available time.

Greenbyte implements a number of different time-based availability calculations. The difference between the calculations is how time periods are allocated to available time or unavailable time. The IEC availabilities are based on the standard IEC 61400-26-1 and use the information model described there.

Contractual Availability

Contractual availability is based on the categories defined in your asset's availability contract. The contract determines whether the categories should be excluded from the calculation or allocated to either available time or unavailable time.

Time-based contractual availability

Availability is the extent (in %) to which a wind turbine is performing its intended services within its design specification. In other words, it is the measure of the potential for a wind turbine to generate electrical power. Contractual availability is based on the categories defined in the wind turbine’s availability contract. The contract determines whether the categories should be excluded from the calculation or allocated to either available time or unavailable time.

Allocation of available time and unavailable time is based on contract categories. Each category specifies whether the time of a status event should be allocated to available time or unavailable time (or excluded altogether). Contractual categories have a priority, which is used to determine how to allocate the time period when statuses from multiple categories are active at the same time.

Technology

Wind: Turbine

Equation

Time-based contractual availability is calculated as the sum of time periods, according to the resolution:

time-based-contractual-availability-eq.jpg

where:

ATC

is the time-based contractual availability

Ta

is the amount of time where data is Available

Tu

is the amount of time where data is Unavailable

For each time period, the turbine will be seen as Available, unless one of the following conditions applies:

  • If there is no status or its priority >= priorityThreshold, and w < cut-inPC, the setting Windspeed below cut-in in the contract will determine if the period is Available, Unavailable, or Excluded.

  • If there is no status or its priority >= prioritythreshold, and w > cut-outPC, the setting Windspeed above cut-out in the contract will detetmine whether the period is Available, Unavailable, or Excluded.

  • If there is no status or its priority is not part of the contract or its priority >= priorityThreshold and neither P nor w has a value, the period will be seen as Excluded.

  • There is an active status, where the set category of that status determines that the period is Available, Unavailable, or Excluded.

  • If the status is a stop that is uncategorized and P <= 0, the period will be seen as Unavailable.

  • If there is no status and P <= 0, the setting No status event and no power output in the contract will determine whether the period is Available, Unavailable ,or Excluded.

where:

P

is power

w

is wind speed

cut-inPC

is the power curve cut-in

cut-outPC

is the power curve cut-out

priority

is the priority set in the contract for the status category

priorityThreshold

s the “out of environmental specification” threshold, with value 104

Inputs
time-based_contractual_availability_in.jpg
Example

This is an example of a Low wind contract, where the priority on all status categories is set to higher than the priorityThreshold (i e 104).

This means that even with an active status, the contract settings

  • Wind speed below cut-in

  • Wind speed below cut-out

will always be used if w < cut-inPC and w > cut-outPC.

time-based_contractual_availability_ex.png
System Availability

System availability does not use any user-defined categories. It is calculated using the status events logged by the turbines.

  • All stop events are always categorized as unavailable

  • Warning events are categorized as unavailable if the turbine is stopped (power <= 0) at the same time as the event and if the wind speed is cut-in wind speed from the power curve + 1 m/s.

  • Informational events do not affect system availability.

  • Time periods without a status event are always categorized as available.

Time-based Operational Availability (IEC B.2.2 User’s View)

Operational availability represents the user’s view of availability and defines the portion of time (in %) that the wind turbine is generating power. All standstill time without status codes is allocated to unavailable time.

Categories considered available

IN SERVICE categories:

  • Full performance – The WEGS is operative and functioning per design specifications with no technical restrictions or limitations beyond the ones specified in the design specifications.

  • Partial performance – The WEGS is operating at reduced performance due to internal or external conditions.

  • Ready standby – The WEGS is in the category READY STANDBY when ready to respond to a predefined event. READY STANDBY is not applicable to the active energy service.

Categories considered unavailable

OUT OF SERVICE categories:

  • Technical Standby – The category TECHNICAL STANDBY is defined as periods when the WEGS is temporarily not functioning due to performance of autonomous tasks required for maintaining the intended functions.

  • Out of Environmental Specification – The category OUT OF ENVIRONMENTAL SPECIFICATION is active when the WEGS is operative but not functioning as the environmental conditions are beyond the design specifications.

  • Requested Shutdown – The category REQUESTED SHUTDOWN is active when the WEGS is operative but not functioning as it has been stopped by a request.

  • Out of Electrical Specification – The category OUT OF ELECTRICAL SPECIFICATION is active when the WEGS is operative but not functioning as the electrical parameters of the WEGS are out of design specifications. This might be caused by grid parameters exceeding operational specifications.

NON-OPERATIVE categories:

  • Scheduled Maintenance – The category SCHEDULED MAINTENANCE is entered during scheduled maintenance of elements of the WEGS preventing the entire WEGS from performing the intended functions.

  • Planned Corrective Action – The category PLANNED CORRECTIVE ACTION is entered during actions required to retain, restore, or improve the intended functions of the WEGS when these actions are not part of normal scheduled maintenance. For the WPS, PLANNED CORRECTIVE ACTION is active when such work is on-going simultaneously on all WTGSs or on elements of the WPS (e.g. BOP) preventing the entire WPS from performing the intended functions.

  • Forced Outage – The category FORCED OUTAGE is obtained when damage, fault, failure or alarm has disabled the WEGS. This can be detected manually or automatically. For a WPS, FORCED OUTAGE is active when such events occur simultaneously on all WTGSs or on elements of the WPS (e.g. BOP) preventing the entire WPS from performing the service.

  • Suspended – The category SUSPENDED is applied to all situations when activities in SCHEDULED MAINTENANCE, PLANNED CORRECTIVE ACTION and FORCED OUTAGE have to be interrupted or cannot be initiated due to conditions which compromise personal safety or equipment integrity.

  • Force Majeure – The category FORCE MAJEURE is applied to all situations where an extraordinary event or circumstance beyond the control of the parties involved, prevents the parties from fulfilling their obligations.

Categories not considered

  • Information unavailable

Note

All definitions are taken from IEC 61400-26-1 Wind energy generation systems – Part 26-1: Availability for wind energy generation systems.

Time-Based Operational Availability Calm (IEC B.2.3 User's View)

Operational availability represents the user’s view of availability and defines the portion of time (in %) the wind turbine is and is not generating because the wind speed is below the turbine’s cut-in wind speed. All standstill time without status codes and during which the wind speed is above cut-in is allocated to unavailable time.

Categories considered available

IN SERVICE categories:

  • Full performance – The WEGS is operative and functioning per design specifications with no technical restrictions or limitations beyond the ones specified in the design specifications.

  • Partial performance – The WEGS is operating at reduced performance due to internal or external conditions.

  • Ready standby – The WEGS is in the category READY STANDBY when ready to respond to a predefined event. READY STANDBY is not applicable to the active energy service.

Categories considered unavailable

OUT OF SERVICE categories:

  • Technical Standby – The category TECHNICAL STANDBY is defined as periods when the WEGS is temporarily not functioning due to performance of autonomous tasks required for maintaining the intended functions.

  • Out of Environmental Specification – The category OUT OF ENVIRONMENTAL SPECIFICATION is active when the WEGS is operative but not functioning as the environmental conditions are beyond the design specifications.

  • Requested Shutdown – The category REQUESTED SHUTDOWN is active when the WEGS is operative but not functioning as it has been stopped by a request.

  • Out of Electrical Specification – The category OUT OF ELECTRICAL SPECIFICATION is active when the WEGS is operative but not functioning as the electrical parameters of the WEGS are out of design specifications. This might be caused by grid parameters exceeding operational specifications.

NON-OPERATIVE categories:

  • Scheduled Maintenance – The category SCHEDULED MAINTENANCE is entered during scheduled maintenance of elements of the WEGS preventing the entire WEGS from performing the intended functions.

  • Planned Corrective Action – The category PLANNED CORRECTIVE ACTION is entered during actions required to retain, restore, or improve the intended functions of the WEGS when these actions are not part of normal scheduled maintenance. For the WPS, PLANNED CORRECTIVE ACTION is active when such work is on-going simultaneously on all WTGSs or on elements of the WPS (e.g. BOP) preventing the entire WPS from performing the intended functions.

  • Forced Outage – The category FORCED OUTAGE is obtained when damage, fault, failure or alarm has disabled the WEGS. This can be detected manually or automatically. For a WPS, FORCED OUTAGE is active when such events occur simultaneously on all WTGSs or on elements of the WPS (e.g. BOP) preventing the entire WPS from performing the service.

  • Suspended – The category SUSPENDED is applied to all situations when activities in SCHEDULED MAINTENANCE, PLANNED CORRECTIVE ACTION and FORCED OUTAGE have to be interrupted or cannot be initiated due to conditions which compromise personal safety or equipment integrity.

  • Force Majeure – The category FORCE MAJEURE is applied to all situations where an extraordinary event or circumstance beyond the control of the parties involved, prevents the parties from fulfilling their obligations.

Categories not considered

  • Information unavailable

Note

All definitions are taken from IEC 61400-26-1 Wind energy generation systems – Part 26-1: Availability for wind energy generation systems.

Time-based System Availability

This calculation determines a turbine's availability based on several factors, providing an estimate for how much time the turbine was productive.

The calculation has 3 concepts of blocks of time: AvailableUnavailable and Excluded.

The output is a percentage indicating the ratio of available to unavailable time. Excluded time is not considered.

time_based_system_availability_wind_flow.jpg

Allocation of available time and unavailable time is based on status categories. Each category is defined for a set of status codes, and specifies whether the time of a status event should be allocated to available time or unavailable time.

The categories have a priority, which can be offset according to any curtailment schemes assigned to the turbine under corresponding time intervals. The priorities are used to determine how to allocate the time period when statuses from multiple categories are active at the same time.

Technology

Wind: Turbine

Equation

For each time period, the turbine will always be seen as Available if there is no status and: cut-outPC < w < cut-inPC + 1 m/s

If this is not true, it will still be seen as Available, unless:

There is no status or the status is uncategorized, and neither P nor w has a value, the period will be seen as Excluded.

The status is uncategorized and P<=0, where the period will be seen as Unavailable.

where:

P

is power

w

is wind speed

cut-in PC

is the power curve cut-in. As the turbine will never start producing at exactly the cut-in wind speed, a buffer of 1 m/s is added.

cut-outPC

is the power curve cut-out

Time-based system availability is then calculated as the sum of time periods, according to the resolution:

time_based_system_availability_wind_eq.jpg

where:

Ta

is the amount of time where data is available

Tu

is the amount of time where data is unavailable

Inputs
time_based_system_availability_wind_in.jpg
Example

Time-based system availability shows how long an asset has not been under a stop status code. This is useful for keeping track of the site's operation state, to benchmark assets within your portfolio, and to assess priority and make an action plan.

time_based_system_availability_wind_ex.png
Time-based System Availability (Planned)

Time-Based System Availability (planned) shows the availability (in %) of a device (turbine or inverter) as determined by the planned downtime that you schedule in Greenbyte. For a given time interval, there are three possible cases:

  1. If there is no planned downtime in the given interval the device is considered to be fully available

  2. If there is scheduled downtime partially overlapping the given interval the device is considered to be partially available

  3. If the given time interval is fully covered by a downtime the device is considered to be totally unavailable

Since downtime can be planned in the future, this signal is available for future time intervals.

Technology

Wind: Turbine, Solar: Inverter

Equation

For each bin (according to the ime resolution (default is 10-minute) the Time-based System Availability (Planned) is calculated as:

time-based-system-availability-planned-eq.jpg

where:

ATS, Planned

is Time-based System Availability (Planned)

Tdown

is the amount of downtime within the bin

Tbin

is the total amount of time in the bin

Inputs
time-based-system-availability-planned-in.jpg
Example
time-based-system-availability-planned-ex1.png
time-based-system-availability-planned-ex2.png
Time-Based Technical Availability (IEC B.3.2 Manufacturer's View)

Technical availability represents the turbine manufacturer’s view of availability and defines the percentage of time the wind turbine is generating according to its design specification. All standstill time without status codes and during which the wind speed is above cut-in is allocated to unavailable time.

Categories considered available:

  • Full performance

  • Partial performance

  • Technical Standby

  • Out of Environmental Specification

  • Requested Shutdown

  • Out of Electrical Specification

Categories considered unavailable:

  • Planned Corrective Action

  • Forced Outage

Categories not considered:

  • Scheduled Maintenance

  • Suspended

  • Force Majeure

  • Information not available

Time-Based Turbine Operational Availability (IEC B.2.4)

Turbine operational availability represents the user’s view of availability but differs from operational availability in that categories that are usually beyond the control of the turbine are excluded from consideration. Time during which the operator has requested a shutdown, when an electrical connection is not available, or a force majeure event has occurred are excluded from the calculation. All standstill time without status codes and during which the wind speed is above cut-in is allocated to unavailable time.

Categories considered available:

  • Full performance

  • Partial performance

  • Out of Environmental Specification – Calm

Categories considered unavailable:

  • Technical Standby

  • Out of Environmental Specification – Other

  • Scheduled Maintenance

  • Planned Corrective Action

  • Forced Outage

  • Suspended

  • Force Majeure

Categories not considered:

  • Requested Shutdown

  • Out of Electrical Specification

  • Information not available