TECHNICAL AREA Project: Wind turbines´centralized system or energy measuring

The measuring of power and energy produced by the wind turbines of the farm, registered in their respective Scada, present a great diversity depending on the technologist.
This fact difficults the comparation of the results because of some factors:

• Power and energy measuring of each wind turbine carried out at different points of the Low-tension network depending on the technologist.
• Instantaneous measurings, not synchronized in time, because each technologies uses the reference of the respective Scada and this fact counteract the simultaneous curve of production of the wind farm.
• Different storage formats of the electric variables in the different Scadas.
• Absence of power data generated at certain intervals because of communication failure between wind turbine Plc and its respective Scada.

The project tries the achievement of a PERMANENT and centralized system of energy acquisition and active and reagent power measuring, registered at the different wind turbines of the farm and the substation.

The characteristics of this process of measuring will allow the surmounting of the problems previously quoted and so, determine the tasks necessary for the management of wind. These are important in order to determine:

• Real energetic fluxes of the farm.
• Deviations of wind turbines energy from the energy recorded in the meter of each machine.
• Real simultaneousness curve of production for extrapolation to predicting methods of wind production and checking of trails effects between wind turbines.
• Calculation of liquid assets and power curve from homogeneous measurings done at each wind turbine, resolving also this way the possible absences of data produced by problems of communication.

The action carried out in this project have been developed in two well distinguished stages:

• Installation of measuring and recording equipments.
• Configuration of the communication network.

Bellow are described the elements of each one.

3.1 Measuring and recording equipments

These are the elements that have to measure the strengths or generation currents of the different wind turbines. They have been located for each wind turbine on the three phases of the low tension wires, before of the connection to the transformer, criteria that allows the standardizacion of values and the stablishment of comparatives.

In the case of wind turbines doubly supplied (the case of Gamesa) it is necessary to register the rolorical and statorical powers generated. This is the reason why strength transformers have been doubled. Strength transformers have been installed in all the 24 wind turbines of the farm.

Network analysts

These are the electronic equipments that record the electric variables to be measured at the wind turbines from the strength recorded at the secondaries of the strength transformers.

The measurings of generated power don´t require the use of tension transformers, because these network analysts directly admit the tension of the 690 of generation of the wind turbines.

The electric parameters measured are:

• Simple and compound tension
• Strength per phase
• Active power in four quadrants
• Reactive power in four quadrants
• Power factor
• Active incremental power at intervals up to 1 minute
• Reactive incremental power at intervals up to 1 minute

The equipments make possible the displaying of these values directly in display.

Circutor network analysts have been installed in the 24 wind turbines and in the 132 Kv output to the transformer of the farm´s substation.

3.2 Configuration of the communications network

Local Pcs in wind turbines and sustation

25 Local pcs have been installed for the storage of all the information received from the respective network analyst through RS-232 communication. Each pc has been configurated with a communications software that do the following actions:

• Reading and displaying of instantaneous measurings.
• Storage of historicals.
• Checking of the state of communications.
• Real time interconection with the central server in order to incorporate this information to other programmes related to the management of the farm.

Likewise, each PC is equipped with a system of uninterrupted supply to avoid wastages of infomation in view of possible network failures.

Integration of wind turbines and substation into LAN network

The next stage consist of the total integration of the PCs of the wind turbines of the farm and the substation into an unique LAN network, pionneering system in Europe. The integrated system of communications used will Ethernet through TCP-IP protocol controlled through the central server placed into the control building.

The advantages of this communications network are:

• Greater stability
• Transmission speed of 100 Mbytes, largely superior than the systems used at other wind farms.

The system is operating perfectly, registering all the electric variables at intervals of one minute in the database.