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COMPANY STANDARD EE 10421629 ST 7:2001 TECHNICAL REQUIREMENTS FOR CONNECTING WIND TURBINE INSTALLATIONS TO THE POWER NETWORK Tehnilised nõuded elektrituulikute liitumiseks elektrivõrguga EESTI ENERGIA AS OFFICIAL PUBLICATION FOREWORD Company Standard EE 10421629 ST 7:2001 “Technical Requirements for Connecting Wind Turbine Generator Systems to the Electrical Network” is a rework of the research work titled “Theoretical Bases and Technical Requirements for Connecting Wind Turbines to the Substations of the Electrical Network”, prepared by the Department of Electrical Power Engineering of the Tallinn Technical University in 2001. The research was prepared by the following working group: Rein Oidram – Associate Professor, Ph.D. – project manager Kalju Möller – Senior Research Fellow, Ph.D. Peeter Raesaar – Associate Professor, Ph.D. Eeli Tiigimägi – Associate Professor, Ph.D. The following working group drafted the Standard and prepared the Standard for adoption: Enno Saluvee – Support Services of Eesti Energia AS, head of the working group Indrek Aarna – Support Services of Eesti Energia AS Mati Kalda - Support Services of Eesti Energia AS Rein Kraav – National Grid of Eesti Energia AS Raivo Rebane – Distribution Network of Eesti Energia AS Mati Roosnurm – Distribution Network of Eesti Energia AS The Standard format is based on the EVS Instruction 4:2000 “Drafting and Presentation of Standards”, drafted by the Estonian Centre for Standardisation. The Standard has been approved and introduced by the Eesti Energia AS directive No 47 of 22 May 2001. The Standard has been entered in the Eesti Energia AS Registry of Normative Documents, Ref. No 30 of 22 May 2001. The Standard shall serve as a guidance upon the connection of wind turbine generator systems and wind farms to the electrical network of Eesti Energia AS. © The rights of publication and copying belong to Eesti Energia AS. II CONTENTS 1. Scope .............................................................................................................................. 1 2. Referenced normative documents............................................................................... 1 3. Definitions...................................................................................................................... 2 3. Symbols, units and abbreviations................................................................................ 4 5. General technical requirements for the electrical network...................................... 5 5.1. Requirements arising from the transmitting capacity of the electrical network ..................5 5.2. Requirements for the WTGS power quality ........................................................................6 5.2.1. Steady-state voltage.......................................................................................................6 5.2.2 Flicker and voltage fluctuations ....................................................................................7 5.2.2.1. Procedure for the assessment of flicker emission due to the WTGS......................8 5.2.2.2. Procedure for the assessment of the relative voltage change due to the WTGS switching operations................................................................................................................9 5.2.3 Permitted emission limits on harmonic currents ...........................................................9 5.2.4 Telecommunication line interference..........................................................................10 5.2.5 Interference in remote switching equipment...............................................................10 5.3. Requirements for relay protection and automation............................................................10 5.3.1. General ........................................................................................................................10 5.3.2. Avoidance of feeding from the WTGS only ...............................................................11 5.3.3. Automatic reclosing ....................................................................................................11 5.3.4. Automatic voltage regulation of the WTGS ...............................................................11 5.4. Stability requirements ........................................................................................................12 5.5. Requirements for telemechanics ........................................................................................12 5.6. Metrological requirements .................................................................................................12 6. Data to be submitted with the application for connection...................................... 13 6.1. General...............................................................................................................................13 6.2. Application for connection ................................................................................................14 6.3. General data on the WTGS ................................................................................................14 6.4. Rated data...........................................................................................................................14 6.5. Data on the WTGS tests.....................................................................................................14 6.5.1. General ........................................................................................................................14 6.5.2. Maximum permitted power.........................................................................................15 6.5.3. Maximum measured power.........................................................................................15 6.5.4. Reactive power............................................................................................................16 6.5.5. Voltage fluctuations ....................................................................................................16 6.5.6. Harmonics ...................................................................................................................17 7. Analysis of the application for connection ............................................................... 18 7.1. General principles of the checking of preconditions for the connection of the WTG Systems to the electrical network ................................................................................................18 7.2. Simplified analysis of the application for connection........................................................18 III COMPANY STANDARD EE 10421629 ST 7:2001 TECHNICAL REQUIREMENTS FOR CONNECTING WIND TURBINE INSTALLATIONS TO THE POWER NETWORK Tehnilised nõuded elektrituulikute liitumiseks elektrivõrguga 1. Scope This Standard relates to the technical requirements for the connection of wind turbine generator systems and wind farms to the electrical network of Eesti Energia AS at high voltage (over 1,000 V). If there is a contradiction between this Standard and other technical normative documents, referred to in this Standard, guidance shall be taken from this Standard. Any amendments to the technical requirements of the Standard shall apply also to the wind turbine generator systems that are already connected. 2. Referenced normative documents This Standard refers to the following documents: Draft IEC 61400-21, Ed. 1 Wind turbine generator systems – Part 21: Measurement and assessment of power quality characteristics of grid connected wind turbines. IEC, 2000 EE 10421629 ST 8:2001 Vahelduvvoolu elektrienergia mõõtmine. Tehnilised nõuded tehingutes kasutatavatele mõõtekompleksidele kõrgepingel. Measuring of Alternating Current of Electric Power. Technical Requirements for Fixed Measuring Systems Used in the Transactions at High Voltage. Eesti Energia AS, 2001 Elektrijaamade liitumise tehnilised tingimused Eesti Energia ASi Jaotusvõrguga Technical requirements for the connection of power plants to the Distribution Network of Eesti Energia AS Uute generaatorite liitumistingimused Requirements for the connection of new generators Eesti Energia AS, Distribution Network, 1999 (09.11) Eesti Energia AS, National Grid, 1999 (05.11) Eesti Energia AS Ametlik väljaanne 1 Põhivõrguga liitumise, võrguühenduse kasutamise ning ülekande-, juhtimis- ja muude teenuste osutamise tüüptingimused Standard conditions of connection to the National Grid, use of network connection and provision of transmission, control and other services IEC 61000-3-7 CCITT 1978 Eesti Energia AS, National Grid, 2001 Electromagnetic compatibility (EMC) - Part 3: Limits − Section 7: Assessment of emission limits for fluctuating loads in MV and HV power systems – Basic EMC publication Directives Concerning the Protection of Telecommunication Lines Against Harmful Effects from Electric Lines, 1978 3. Definitions In this Standard the following definitions are used: 3.1. Wind turbine generator system (WTGS) – a system that is comprised of a wind turbine, drive, generator, controller and tower and converts kinetic energy in the wind into electrical energy. 3.2. Wind turbine generator systems (WTG Systems) – a general term, used if there is no need to specify in the text of the Standard whether reference is made to the wind turbine generator system or wind farm. 3.3. Wind farm – an integrated unit comprised of several WTG Systems, as well as the buildings and equipment connecting the WTG Systems to the connection point and interconnecting the WTG Systems. 3.4. Electrical network – an integrated unit for the transmission or distribution of electrical energy, comprised of buildings and equipment. Note 1. For the purpose of this Standard, the electrical network means the electrical network of Eesti Energia AS, if not specified otherwise. 3.5. Wind turbine generator system terminals – a point being a part of the WTGS and identified by the WTGS supplier at which the WTGS may be connected to the power collection system. 3.6. Cut-in wind speed – the lowest wind speed at hub height at which the WTGS starts to produce power. 2 3.7. Connection point – a precisely defined point of connection of customer’s electrical installation to network operator’s network; if not agreed otherwise, the connection point shall define the responsibility of the customer and network operator, and the service boundary of the electrical installations. 3.8. Switching operation – start-up or switching-over of generators. 3.9. Flicker step factor – a normalised measure of the flicker emission due to a single switching operation of the WTGS. 3.10. Rated current – the current from the WTGS while operating at rated power and nominal voltage and frequency. 3.11. Rated apparent power – the apparent power from the WTGS while operating at rated power and nominal voltage and frequency. S n = Pn2 + Qn2 Here Pn is the rated (active) power and Qn is the corresponding reactive power. 3.12. Rated reactive power – the reactive power from the WTGS while operating at rated power and nominal voltage and frequency. 3.13. Rated power – the maximum continuous (active) output power from the WTGS under normal operating conditions. 3.14. Normal operation – fault-free operation complying with the description in the WTGS manual. 3.15. Voltage change factor – a normalised measure of the voltage change due to a switching operation of the WTGS. Note 2. The voltage change factor kU is similar to ki being the ratio between the maximum inrush current and the rated current, though kU is a function of the network impedance phase angle. The highest value of kU will be numerically close to ki . 3.16. Continuous operation – normal operation of the WTGS, excluding start-up and shutdown operations. 3.17. Flicker coefficient for continuous operation – a normalised measure of the flicker emission during the continuous operation of the wind turbine. Note 3. The flicker coefficient for continuous operation is the same for a short-term (ten minutes) and long-term period (two hours). 3 3.18. Maximum permitted power – the ten-minute-average power that shall not be exceeded irrespective of weather and network conditions. 3.19. Maximum measured power – the maximum power (with a specified averaging time) observed during the continuous operation of the WTGS. 3.20. Wind turbine – a device which converts kinetic energy in the wind into rotating mechanical energy of the WTGS shaft. Note 4. In English a wind turbine is often denoted a WTGS. 3.21. Rated wind speed – wind speed at which a wind turbine’s rated power is achieved. 3.22. Network impedance phase angle – phase angle of network short-circuit impedance ψ k = arctan( X k Rk ) Here Xk is the network short-circuit reactance and Rk is the network short-circuit resistance. 3.23. Output power – electric active power delivered at the WTGS terminals. 3.24. Flicker – a visual perception of variations, caused by the fluctuation of brightness of electric lighting or by changing in time spectral distribution. 3. Symbols, units and abbreviations ∆U dyn Un ψκ ∆S ∆Udyn c(ψκ ,va) ci(ψκ ,va) cos φ d EPlti EPsti ET fh h Ii lub In kf(ψκ) maximum permitted voltage change network impedance phase angle (º) apparent power change dynamic voltage change flicker coefficient for continuous operation flicker coefficient of a single (i’th) WTGS power factor relative voltage change long-term flicker emission limit short-term flicker emission limit wind turbine generator system frequency of the h’th harmonic (Hz) harmonic order permitted continuous current of a single (i’th) network element (A) rated current (A) flicker step factor 4 ki kU(ψκ) N10 N120 Nwt P0,2 P60 Plt Pmc Pn Pst Q0,2 Q60 Qmc Qn r Rk SET Si Si lub Sn Sn, i Sk Smax i THD THFF U1 Uh Un va Xk ratio of maximum inrush current and rated current voltage change factor number of one type of switching operations within a 10-minute period number of one type of switching operations within a 120-minute period number of WTG Systems connected to a single connection point maximum measured power (0.2-second-average value) (W) maximum measured power (60-second-average value) (W) long-term flicker emission (flicker disturbance factor) maximum permitted power (W) rated power (W) short-term flicker emission (flicker disturbance factor) reactive power (0.2-second-average value) at P0.2 (var) reactive power (60-second-average value) at P60 (var) reactive power at Pmc (var) rated reactive power (var) frequency of voltage changes (hour-1, min-1) short-circuit resistance of the network (Ω) power generated by the WTGS (V·A) contractual apparent power of the i’th user of the medium voltage network (V·A) maximum permitted power of the i’th element of the distribution network (V·A) rated apparent power (V·A) rated apparent power of a single WTGS (V·A) short-circuit apparent power of the network (V·A) peak apparent power of the fluctuating load total harmonic distortion factor telephone harmonic form factor 50 Hz component of the phase voltage (root mean square (RMS)) (kV) the h’is harmonic of the voltage (root mean square) (kV) nominal phase-to-phase voltage of the electrical network (V) annual average wind speed (m/s) short-circuit reactance of the network (Ω) 5. General technical requirements for the electrical network 5.1. Requirements arising from the transmitting capacity of the electrical network The requirements arising from the transmitting capacity of the electrical network are based on the fact that in open 35 and 10 kV electrical networks, the direction of generated by the WTGS power S ET is opposite to the direction of the power flows due to the consumer loads. This situation is explained on Figure 1. 5 SET 35 kV SET SET 110 kV SET SET 10 kV SET SET 10 kV SET Power flows in the electrical Tarbijate koormustest tingitud network due to the consumer load võimsusvood jaotusvõrgus ET SET Elektrituuliku võimsusvoog Power flow from the WTGS Figure 1 – Power distribution in the electrical network with a WTGS In addition to the thermal tolerance, the transmitting criterion in this case shall be the permissibility of the difference between the power flows from the WTGS and any element i on the path between the WTGS and the 110 kV electrical network. S ET − S i ≤ S i lub (1) Provided that the power flows Si , due to the consumer loads, pose individually no thermal danger to any element, the most dangerous overload may occur in a situation where consumer loads are at minimum and the power of the WTG System(s) is at maximum. Therefore, if Si ≈ 0, then S ET ≤ S i lub (2) Consequently, the maximum power requirement for the WTG Systems to be installed shall be based on the transmitting capacity of the element with the minimum permitted continuous load in the existing distribution network, as follows: S ET ≤ min ( Si lub ) = min ( 3 ×U n × I i lub ) (3) In the case of lines, the minimum permitted power corresponds to the permitted current for the line section with the minimum wire cross-section at the voltage level in question. 5.2. Requirements for the WTGS power quality 5.2.1. Steady-state voltage The operation of installation of WTG Systems in the electrical network may affect the steady-state voltage in the connected network. It is required that load-flow calculations be conducted to ensure that the WTG Systems do not bring the magnitude of the voltage outside the permitted limits. During the load-flow analysis the impact of the WTG Systems shall be assessed as follows: - at rated power, or 6 - at active power P60 (60-second-average value) (kW) and reactive power Q60 (60-secondaverage value) (kvar), or at active power P0.2 (0.2-second-average value) (kW) and reactive power Q0.2 (0.2-secondaverage value) (kvar). The wind farm shall be assessed assuming its output power at the connection point. More specifically, the ten-minute-average power values (Pmc and Qmc) and 60-second-average power values (P60 and Q60) may be calculated by simple summation, and the 0.2-second-average values may be calculated according to the following equations: N wt P0 ,2 Σ = ∑ Pn , i + i =1 N wt Q0 ,2 Σ = ∑ Qn , i + i =1 5.2.2 N wt ∑( P 0 ,2 , i i =1 N wt ∑( Q 0 ,2 , i i =1 − Pn , i ) 2 (4) − Qn , i ) 2 (5) Flicker and voltage fluctuations Flicker emission from the WTG Systems shall not exceed the permitted limits: Pst ≤ EPst i (6) Plt ≤ EPlt i (7) Whereas the permitted emission limits at the connection point in question shall be as follows: EPst i = 0,35 EPlt i = 0,25 The relative voltage change due to the WTG Systems shall be limited in accordance with the following: ∆U dyn d≤ (8) Un The permitted voltage change limits are given in Table 1 Table 1 – Permitted voltage change limits r (hour -1) r≤1 1 < r ≤ 10 10 < r ≤ 100 100 < r ≤ 1000 ∆Udyn /Un (%) at the voltage of 35 kV at the voltage of 110 kV and lower and higher 4 3 3 2,5 2 1,5 1,25 1 7 5.2.2.1. Procedure for the assessment of flicker emission due to the WTGS Continuous operation The flicker emission from a single WTGS during continuous operation shall be expressed as follows: S Pst = Plt = c(ψ k , va ) × n (9) Sk where c(ψk, va) is the flicker coefficient of the WTGS for the given network impedance phase angle, ψk at the connection point, and for the given annual average wind speed, υa measured at the hub-height of the turbine at the site of the WTGS. The WTGS flicker coefficient c(ψk, va) for the actual ψk and va at the installation site, shall be found from the table of measuring results, applying linear interpolation. If there are more than one WTGS connected to the connection point, the sum of their flicker emission shall be estimated as follows: Pst Σ = Plt Σ = 1 Sk N wt ∑ (c (ψ i k , va ) × S n , i ) 2 (10) i =1 Switching operations The flicker emission due to the switching operations of a single WTGS shall be estimated applying the following equations: Pst = 18 × N 100,31 × k f (ψ k ) × 0, 31 Plt = 8 × N 120 × k f (ψ k ) × Sn Sk (11) Sn Sk (12) where kf(ψk) is the flicker step factor of the WTGS for the given network impedance phase angle, ψk at the connection point. The WTGS flicker step factor kf(ψk) for the actual ψk at the installation site shall be found from the table of measuring results, applying linear interpolation. If there are more than one WTGS connected to the connection point, the sum of their flicker emissions shall be estimated from the following equations: Pst Σ 18 N wt 3, 2 = ∑ N10, i × (k f , i (ψ k ) × S n , i ) Sk i =1 Plt Σ 8 = Sk 0, 31 N wt 3, 2 ∑ N120, i × (k f , i (ψ k ) × S n , i ) i =1 8 (13) 0 , 31 (14) where N10, i and N120, i are the number of switching operations of the individual WTGS within a 10-minute and 2-hour period, respectively kf, i(ψk) is the flicker step factor of the individual WTGS Sn, i is the rated apparent power of the individual WTGS 5.2.2.2. Procedure for the assessment of the relative voltage change due to the WTGS switching operations. The relative voltage change due to the switching operations of a single WTGS shall be estimated applying the equation below: S d = kU (ψ k ) × n (15) Sk The WTGS voltage change factor kU(ψk) for the actual ψk on the installation site, shall be found from the table of measuring results, applying linear interpolation. If there are more than one WTGS connected to the connection point, it is still unlikely that even two of them will perform a switching operation at the same time. Hence, no summation effects need to be taken into account to assess the relative voltage change of an installation consisting of several WTG Systems. If the applicant for connection has submitted a report on the power quality test results with no data on the voltage change factor, the relative voltage change may be found from the Equation (15), applying the voltage change factor value kU(ψk) = 1,0. 5.2.3 Permitted emission limits on harmonic currents Harmonic currents must not cause voltage rise at the connection point. Table 2 gives the permitted emission limits on odd harmonic currents in a continuous situation. Within the same frequency range, the emission limits on even harmonic currents shall not exceed 25% of the values given in Table 2. Table 2 – Permitted emission limits on odd harmonic currents Harmonic order Emission limits on harmonic currents with respect to the current 4,0 % 2,0 % 1,5 % 0,6 % 0,3 % 5,0 % h < 11 11 ≤ h < 17 17 ≤ h < 23 23 ≤ h < 35 35 ≤ h < 50 Total harmonic distortion factor (THD) 9 The total harmonic distortion factor (THD) shall be defined as: THD = 100 5.2.4 Uh ∑ h=2 U1 50 2 (%) (16) Telecommunication line interference The Telephone Harmonic Form Factor (THFF) shall be defined as: THFF = Fh = Ph × h × Uh × Fh ∑ h =1 U 1 50 2 fh 800 (17) (18) where Ph is the relative interference at frequency fh in a telecommunication circuit as determined from a psophometric weight factor according to CCITT (Directives Concerning the Protection of Telecommunication Lines Against Harmful Effects from Electric Lines, CCITT 1978). The THFF factor shall not exceed 1% at the connection point. 5.2.5 Interference in remote switching equipment The WTG Systems shall not generate noise more than –35 dB (0 dB = 0.775 V) in the frequency range of (40…500) kHz, measured in the input of a standard remote switching device at the connection point. The measured frequency bandwidth shall be at least 2 kHz. 5.3. Requirements for relay protection and automation 5.3.1. General Upon the connection of the WTG Systems, the requirements for relay protection and automation shall be complied with, based on the following documents of Eesti Energia AS: - Technical requirements for the connection of power plants to the Distribution Network of Eesti Energia AS Requirements for the connection of new generators - Standard conditions of connection to the National Grid, use of network connection and provision of transmission, control and other services. In addition, the Network Operator shall specify the following requirements for the connection: 10 - the need to upgrade the relay protection and automation of the electrical network in connection with the increase in short-circuit currents and (or) introduction of a feeding from several independent sources; avoiding the feeding from the WTG Systems of the part of the network that has been disconnected under an abnormal operation; automatic reclosing, and automatic synchronisation of the WTG Systems; the need for automatic voltage regulation of the WTG Systems; avoidance or mitigation of start-up shocks in the case of WTG Systems with asynchronous generators. 5.3.2. Avoidance of feeding from the WTGS only If due to a fault in the electrical network (e.g. short-circuit) it is only the WTG Systems that remain feeding the customers, these WTG Systems shall be instantly disconnected from the electrical network in order to avoid non-permissible excessive deviations of voltage and frequency of the electrical energy supplied to the customers in the respective part of the network. The disconnection shall be conducted according to the values given in Table 3 Table 3 - The time limit set on the disconnection of the WTG Systems Electrical energy characteristic Frequency Voltage Values Time limit on disconnection s < 47,0 Hz ≤ 0,3 > 53,0 Hz ≤ 0,3 < 85 % Un ≤ 10 > 106 % Un ≤ 60 > 110 % Un ≤ 0,5 5.3.3. Automatic reclosing Given the transient nature of the majority of short-circuits, there shall be an automatic reclosing following the tripping off of the short-circuit. For a successful reclosing, also the WTGS must be tripped off instantly. The network operator shall define the duration of the voltage break of the automatic reclosing. 5.3.4. Automatic voltage regulation of the WTGS The need for the automatic voltage regulation of the WTGS may arise in the case of high-power generators, as well as in the case when the WTGS is connected to the same substation’s busbars that the customers are connected to. In order to reduce the voltage fluctuations due to the WTGS, the introduction of current compensation on transformers’ automatic voltage regulators and (or) readjustment may be required. The network operator shall perform the required calculations and prepare the technical solutions. 11 5.4. Stability requirements A wind farm that is connected to the National Grid shall be able to withstand the following faults in all operational situations, without losing its stability: - a three-phase short-circuit on a random line or transformer, with a lasting interruption of connection, with no reclosing; Note 5. A typical fault: occurrence of a short-circuit, tripping off of the line/transformer, no automatic reclosing. Typically, the tripping off of the short-circuit takes 0.5 seconds, but may last longer in some places. - a two-phase short-circuit on a random line, with unsuccessful reclosing. Note 6. A typical fault: occurrence of a short-circuit, tripping off of the line, unsuccessful automatic reclosing with a lasting tripping off of the short-circuited line. Typically, the tripping off of the short-circuit takes 0.5 seconds, and in the case of an unsuccessful reclosing the tripping off of the short-circuit takes (0.1…0.15) seconds. These requirements shall not apply to the faults, which are due to the radially- connected wind farms, because a fault in the radial connection will disconnect the wind farm from the power system. The stability assessment shall be based on the actual time required for remedying the damage identified by the relay protection. Stability shall be assessed under both the normal operation and overhaul schemes. The wind park shall withstand at least three faults within two minutes, without the connection being interrupted. This requirement mainly aims at providing the WTG Systems a sufficiently trouble-free auxiliary supply voltage. 5.5. Requirements for telemechanics The remote measuring and, if required, control of voltage, active power and reactive power at the connection point of the WTG Systems shall be taken to the regional dispatch centre. 5.6. Metrological requirements At the connection point of the WTG Systems to the electrical network at least the following shall be measured: the voltage and current of electrical energy, active power, reactive power, amount of active power and amount of reactive power. The power and energy shall be measured in both directions. The said measuring shall comply with the Metrology Act and other legislation, rules and normative documents on metrology valid in Estonia. The issues, which are not regulated by the Metrology Act or other legislation and normative documents valid in Estonia, shall be solved by way of co-ordination between the parties. The site of measuring of electrical energy at the connection point shall comply with the requirements of the Company Standard of Eesti Energia AS EE 10421629 ST 8:2001 “Measuring of Alternating Current of Electric Power. Technical Requirements for Fixed Measuring Systems Used in the Transactions at High Voltage.” 12 The required accuracy classes of the measuring devices used in the transactions are given in Table 4. Table 4 - Required accuracy classes of the measuring devices used in the transaction Nominal value of the measured voltage kV 6 … 35 110 Accuracy classes of electricity meters Accuracy class of current transformer Accuracy class of voltage transformer Active power meter Reactive power meter 1,0 2,0 0,2 or 0,2S 0,2 0,5 1,0 0,2 or 0,2S 0,2 The requirements for the maximum permissible totalised error of the measuring of electrical energy are given in Table 5. Table 5 -The requirements for the maximum permissible totalised error of the measuring of electrical energy at the load of (10…100) % of nominal load in the range of (0.8…1.0) of the power factor cos φ Nominal value of the measured voltage kV 6 … 35 110 Maximum permissible error under verification requirements ±% Active power Reactive power measuring measuring 2,0 3,0 1,5 2,0 Maximum permissible error under operational requirements Active power measuring 2,5 Reactive power measuring 4,0 2,0 3,0 6. Data to be submitted with the application for connection 6.1. General The applicant for connection to the electrical network shall submit an application for connection and the following general and technical data, as well as test results for each type of WTGS to be installed: - general data; - rated data; - data on the tests of the WTGS type. The technical data and test results shall be submitted in the scope defined under Articles 6.3-6.6. 13 6.2. Application for connection The application for connection shall contain the following data: - data about the applicant; - desired installation-location; - desired connection point; - number of the WTG Systems; - data on the tests of the WTG Systems (separately for each type). 6.3. General data on the WTGS Table 6 Wind turbine type (horizontal-axis or verticalaxis) Number of blades (pcs) Rotor diameter (m) Hub height (m) Blade control (pitch/stall) Speed control (fixed/two-speed/variable) Generator type and rating(s) (kW) Frequency converter type and rating (kW) Transformer type and rating (kVA) 6.4. Rated data Table 7 Rated power, Pn (kW) Rated wind speed, vn (m/s) Rated apparent power, Sn (kVA) Rated reactive power, Qn (kvar) Rated current, In (A) Rated voltage, Un (V) Times inrush current kI Transformer transfer factor (kV/kV) Note 7. Upon the connection to the National Grid, in addition to the data requested in Table 7 also the data on generator’s electrical parameters shall be submitted in compliance with the document of the National Grid of Eesti Energia AS “Requirements for the connection of new generators”. 6.5. Data on the WTGS tests 6.5.1. General The testing of the WTG Systems shall be based on the standard IEC 61400-21 (until the publication of the standard, guidance shall be taken from the draft standard). The organisation that conducts the tests shall be competent to do so. 14 The characteristics are valid for the specific configuration of the tested WTGS only. Other configurations, including altered control parameters, that cause the wind turbine to behave differently in terms of power quality, require separate assessment. Data about the organisation that conducts tests and test description shall be submitted in the following scope: Table 8 Name of test organisation Report number WTGS type designation WTGS manufacturer Serial number of the WTGS tested Table 9 Type of information Description of the tested WTGS, including settings of control parameters Description of test site and network connection Description of test equipment Description of test conditions Note of exceptions to IEC 61400-21 Document name and date Table 10 Author Checked Approved Date of issue 6.5.2. Maximum permitted power Table 11 Assessed value, Pmc (kW) Normalised value, pmc = Pmc / Pn 6.5.3. Maximum measured power 60-second-average value Table 12 Measured value, P60 (kW) Normalised value, p60 = P60 / Pn 0.2-second-average value Table 13 Measured value, P0,2 (kW) Normalised value, p0,2 = P0,2 / Pn 15 6.5.4. Reactive power Table 14 Output power (% of Pn) 0 10 20 30 40 50 60 70 80 90 100 Output power (kW) Reactive power (kvar) Table 15 Assessed reactive power at Pmc (kvar) Assessed reactive power at P60 (kvar) Assessed reactive power at P0.2 (kvar) 6.5.5. Voltage fluctuations Continuous operation Table 16 Network impedance phase angle, ψκ ( °) Annual average wind speed, va (m/s) 6,0 7,5 8,5 10,0 30 Switching operations Table 17 Type of switching operation Max. number of switching operations, N10 Max. number of switching operations, N120 Network impedance phase angle, ψκ ( °) Flicker step factor, kf(ψκ) Voltage change factor, kU(ψκ) 50 70 Flicker coefficient, c(ψκ ,va) 85 Start-up at cut-in wind speed 30 Table 18 Type of switching operation Max. number of switching operations, N10 Max. number of switching operations, N120 Network impedance phase angle, ψκ ( °) Flicker step factor, kf(ψκ) Voltage change factor, kU(ψκ) 50 70 85 Start-up at rated wind speed 30 16 50 70 85 In the case of the WTG Systems with more than one generator or with a divided winding generator: Table19 Type of switching operation Worst case switching between generators Max. number of switching operations, N10 Max. number of switching operations, N120 30 50 70 85 Network impedance phase angle, ψκ ( °) Flicker step factor, kf(ψκ) Voltage change factor, kU(ψκ) 6.5.6. Harmonics Relevant only for the WTG Systems with a power electronic converter Table 20 Output power Harmonic current Order Output power Harmonic current Order (kW) (% of In) (kW) (% of In) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Table 21 Maximum total harmonic current distortion (% of In) Output power at maximum total harmonic current distortion (kW) 17 7. Analysis of the application for connection 7.1. General principles of the checking of preconditions for the connection of the WTG Systems to the electrical network While handling the application for the connection of the WTG Systems to the electrical network, the values characterising the WTGS power quality shall be compared with the permitted limits. The values characterising the WTGS power quality shall be found based on the submitted by the applicant report, which contains data about the WTGS and power quality test results. The fulfilment of preconditions for the connections shall be checked in detail based on the comparison with the permitted emission limits and maximum permitted voltage change of the submitted by the applicant parameters, or indicators calculated from these parameters. It is assumed that one or several WTG Systems are to be connected, which power quality characteristics have been measured in accordance with the recommendations of the IEC draft standard IEC 61400-21. The defining for the medium and high voltage installations of permitted flicker emission limits and maximum permitted voltage change shall be based on the principles stipulated in Article 5.2. Upon the assessment of the voltage fluctuation limit levels, guidance shall be taken from Section 7 of Part 3 of the international electromagnetic compatibility standard (IEC 61000-3-7) Assessment of emission limits for fluctuating loads in MV and HV power systems. In this Enterprise Standard the IEC 61000-3-7 term “fluctuating load” has been replaced with the term “fluctuating power”. In compliance with the international flicker standard IEC 61000-3-7, the connected party shall take care that the emission from the WTGS at the connection point is below the minimum established by the Electricity Company. The electricity company and the connected party may co-operate, if required, in order to find optimal methods for emission reduction. The connected party is responsible for implementing the method. 7.2. Simplified analysis of the application for connection Upon a partial submission of test results referred to in Article 6 of this Standard, the possibilities for connection shall be checked as follows: S max i ≤ 0,1 % Sk (19) where Smax i is the peak apparent power of the fluctuating load Sk is the short-circuit apparent power of the network at the connection point. If there is data available about the frequency of power changes, the connection of the fluctuating power can be accepted without further analysis, provided that the maximum relative power changes with respect to the short circuit power (∆S/Sk)max at the connection point are within the limits given in Table 22. The limits depend on the number of voltage changes per minute, r (voltage drop with the subsequent recovery counts as two changes). 18 Table 22 - Limits on the relative power change, dependant on the number of changes per minute (∆S/Sk)max (%) 0,1 0,2 0,4 r (min−1) r > 200 10 ≤ r ≤ 200 r < 10 Power changes ∆S may be lower or higher than or equal to the rated power Sn of the respective device (e.g. in the case of an engine or WTGS account shall be taken of the apparent power at the start-up, and ∆S may be 3-8 Sn). Genrally, ∆S = ki × Sn (20) whereas the following requirement shall be met: S k ≥ 25 ki × S n (21) where Sk is the short-circuit power of the network Sn is the rated apparent power of the WTG Systems ki is the ratio of the maximum inrush current and rated current of the WTG Systems. 19