Wind grid code for India - National Institute of Wind Energy

Draft Report On

Indian Wind Grid Code Submitted to

Centre for Wind Energy Technology Velachery - Tambaram Main Road, Pallikaranai, Chennai - 600 100, Tamil Nadu, INDIA

July 2009

Power Research and Development Consultants Private Limited No 5, 11th Cross, 2nd Stage, West of Chord Road, Bangalore - 560086, Karnataka, INDIA. Ph: +91- 80-23192168 / 23192159, FAX: 23192210, E-mail – [email protected] Web site: www.prdcinfotech.com

Indian Wind Grid Code –Version 1.0

July 2009

Purchase Order No: C-WET/R&D/Grid Code/PR&DC/2008-09, Dated 03/03/2009 Document ref

PRDC/2009-2010/C-WET/831

Signature

Date

Mr. Sarasij Das Prepared by

Mr. Ramesh Pampana

Reviewed by

Mr. V. Venkata Subba Rao

Approved by

Dr. K. Balaraman

Power Research and Development consultants (PRDC) Pvt. Ltd

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Preamble With due consideration of the fact of growing wind energy sector in India, a Technical Working Group was formed by the Ministry of New and Renewable Energy (MNRE), to formulate guidelines in addressing the technical issues/problems of power evacuation and grid synchronization related to wind power projects. The following are the members of the Technical Working Group: i. Shri M.P. Ramesh, Ex-ED (C-WET)

-

Chairman

ii. K.P.Sukumaran, Advisor & Head, WE, MNRE

-

Member

iii. Shri P.S. Jagannatha Gupta, CE (Retd.), KPTCL -

Member

iv. Shri R.N. Nayak, ED, PGCIL

-

Member

v. Chief Engineer (GM),CEA or his representative

-

Member

vi. Director (Transmission), Ministry of Power

-

Member

vii. Representative from TNEB

-

Member

viii. Representative from IWTMA

-

Member

ix. Shri S.K.Soonee, ED, PGCIL

-

Member

x. Director, MNRE

- Member Secretary

The Technical Working Group met twice, first on19-01-2009, secondly on 17-04-2009 with regard to the requirement and development of grid code for wind power generation in India. As a part of addressing the technical issues/problems of power evacuation and grid synchronization related to wind power projects, the Technical Working Group has awarded the task of “Developing of grid code for wind power generation in India” to M/s Power Research and Development consultants (PRDC) Pvt. Ltd, Bangalore. PRDC has formulated a draft report on the grid code for wind power generation in India named as “Indian Wind Grid Code” which will be presented before the committee.


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Chapter 1

INTRODUCTION The Indian Electricity Grid Code (IEGC) provides the technical rules to facilitate the operation, maintenance, development and planning of electricity grid. The objective of IEGC is to maintain safe, reliable and disciplined operation of power system. The IEGC guidelines and standards are to be followed by the various agencies and participants of the power grid.

Indian power generation sector is changing its nature like elsewhere in the world with focus on environmental impacts of conventional sources and need to encourage renewable energy. More and more renewable energy sources, mainly wind energy, are being integrated into the grid. Today, wind generation, whose penetration is increasing have significant impact on Indian power grid. The IEGC as well as the state grid codes were originally developed considering the synchronous generators generally used in conventional power plants. Wind turbine generators (WTG) do not have the same characteristics as synchronous generators and hence a modification or change in the grid code is necessary. Indian Wind Grid Code (IWGC) has been developed for the reliable and secure operation of the wind farms and their integration into the Indian electrical system. This grid code can be used in tandem with the IEGC/State Grid code or the IEGC and state grid codes can be amended with the provisions. 1.1 Objective The primary objective of IWGC is to establish the technical rules which all wind farms must comply with in relation to their planning, connection and operation on the Indian grid. 1.2 Scope All grid connected wind farms and those who operate the associated transmission system are required to abide by the principles defined in the IWGC in so far as they apply to them. The IWGC (except sections 4.6.6 and 5.10) shall come into effect from dd/mm/yyyy. The timeline for implementing fault ride through capability (section 4.6.6) and wind energy forecasting (section 5.10) shall be specified separately by the concerned authority taking into account the penetration levels of wind energy, cost of implementation and tariff structure and their usefulness in terms of grid management strategies.


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1.3 Structure of the IWGC IWGC gives guidelines for transmission planning, grid connection and operation of wind farms. The content of IWGC is as follows: i)

Role of various organizations and their linkages: This chapter defines the functions of the various organizations as are relevant to IWGC. The organizations and their linkages are defined to facilitate development and smooth operation of regional grids.

ii) Planning code for transmission systems evacuating wind power: This chapter provides the policy to be adopted in the planning transmission system for wind power evacuation. The planning code stipulates the various criteria to be adopted during the planning process. iii) Connection code for wind farms: This chapter specifies minimum technical and design criteria to be complied with by wind farms connected to the system or seeking connection to the grid, to maintain uniformity and quality across the power system. iv) Operating code for wind farms: This chapter describes the operational philosophy to maintain efficient, secure and reliable grid operations of power grids having wind farms and conventional power plants. 1.4 Non-compliance In case of a persistent non-compliance of any of the stipulations of the IWGC by a constituent or an agency (other than RPC, RLDC and SLDC), the matter shall be reported by any agency/RLDC to the Member Secretary, RPC or the designated agency. The Member Secretary, RPC or the designated agency, shall verify and take up the matter with the defaulting agency for expeditious termination of the noncompliance. In case of inadequate response to the efforts made by the Member Secretary, RPC, the non-compliance shall be reported to CERC/SERC. CERC/SERC, in turn after due process, may order the defaulting agency for compliance, failing which; the CERC/SERC may take appropriate action. RPC or the designated agency shall maintain appropriate records of such violations. In case of a non-compliance of any of the stipulations of the IWGC by RLDC/SLDC or RPC, the matter shall be reported to the CERC / SERC. 1.5 Exemptions Any exemption from provisions of IWGC shall become effective only after approval of the CERC/ SERC, for which the agencies will have to file a petition in advance.


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1.6 Glossary and definitions Item

Definition

Act

The Electricity Act, 2003

Available Active

The amount of active power that the WTG could

Power

produce based on current wind conditions.

BIS

The Bureau of Indian Standards

Capacity factor

The ratio of maximum generation in MW to sum of installed capacity of individual WTGs in the Wind Farm

CEA

Central Electricity Authority of India

CERC

The Central Electricity Regulatory Commission referred to in sub-section (1) of Section 76 of the Act

CTU

Central Transmission Utility means any Government company, which the Central Government may notify under sub-section (1) of Section 38 of the Act.

C-WET

Centre for Wind Energy Technology

Dynamic VAr

An electrical facility designed for the purpose of

compensation

generating or absorbing reactive power.

Frequency

The automatic adjustment of active power output

Response

from a WTG in response to frequency changes

Grid connection

The point where all WTGs of a wind farm are

point

connected to the grid. Point G in the following figure is referred as Grid connection point.

Grid substation

The substation to which the wind farm is connected.

Installed capacity

The sum of rated generating capacity of each WTG in a wind farm in MW

IEC

The International Electro technical Commission.

IEGC

Indian Electricity Grid Code


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Inter State

Inter-State Transmission System includes

Transmission

i) any system for the conveyance of electricity by

System (ISTS)

means of a main transmission line from the territory of one State to another State ii) The conveyance of energy across the territory of an intervening State as well as conveyance within the State which is incidental to such inter-state transmission of energy iii) The transmission of electricity within the territory of State on a system built, owned, operated, maintained or controlled by CTU.

IWGC

Indian Wind Grid Code

Plant Load Factor

Plant load factor is the ratio of the energy actually supplied by a plant (in a year) to the product of the installed capacity and number of hours in a year.

Regional Load

‘Regional Load Dispatch Centre’ means the Centre

Dispatch Center

established under sub-section (1) of Section 27 of the

(RLDC)

Act.

Regional Power

“Regional Power Committee” means a Committee

Committee (RPC)

established by resolution by the Central Government for a specific region for facilitating the integrated operation of the power systems in that region.

SEB

State Electricity Board including the State Electricity Department.

SERC

State Electricity Regulatory Commission.

State Load

‘State Load Dispatch Centre’ is the Centre establish-

Dispatch Centre

ed under sub-section (1) of section 31 of the Act.

(SLDC) State Sub Load

State's Sub Load Centre for local control at various

Dispatch Centre

places in the state.

(SSLDC) State Transmission

‘State Transmission Utility’ means the Board or the

Utility (STU)

Government Company specified as such by the State Government under sub-section (1) of Section 39 of the Act.

TSO

Transmission System Operator


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Indian Wind Grid Code –Version 1.0 WTG

Wind turbine Generator

Wind farm

A wind farm is a collection of WTGs that are

July 2009

connected to the grid at a common point Wind farm operator

The operator of the wind farm.

Wind farm owner

Entity having legal right of the wind farm


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Chapter 2

ROLE OF VARIOUS ORGANIZATIONS AND THEIR LINKAGES Chapter 2 of IEGC shall be followed.


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Chapter 3

PLANNING CODE FOR TRANSMISSION SYSTEMS EVACUATING WIND POWER This chapter comprises various aspects of transmission system planning for wind power evacuation. Planning policy, planning criteria for transmission lines evacuating wind power are discussed in this chapter. 3.1 Introduction i)

The planning code specifies the policy and procedures to be applied in planning of transmission lines for evacuating wind power.

ii) Role of various organizations in wind farm planning procedure will be same as planning procedure for conventional generators. iii) The planning procedure shall be governed by IEGC and “Electricity Act, 2003”

3.2 Objective The planning code for transmission systems for wind power evacuation shall be part of bigger plan that encompasses overall grid planning. The objectives of the planning code are: i)

To specify the principles, procedures and criteria which shall be used in the planning and development of the transmission system evacuating wind power.

ii) To promote co-ordination between wind farm developers, system operators and regional constituents in any proposed development of wind farms. iii) To provide methodology and information exchange amongst regional constituents and agencies in planning of transmission system for evacuation of wind power. 3.3 Scope The planning code applies to transmission licensees, wind farms, SEBs, CTU/STUs and Distribution licensees involved in developing the transmission/ evacuation system for wind power evacuation. 3.4 Planning policy CTU/STU/TSO may formulate perspective transmission plan for wind power evacuation in a region. The transmission planning shall consider both short term and long-term expected wind generation in the region. The planning shall fit into


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Indian Wind Grid Code –Version 1.0 National Electricity Plan formulated by Central Government,

July 2009 perspective

transmission plan developed by CEA, Electric Power Survey of India published by CEA and policy guide lines (if any) issued by concerned ministry regarding renewable energy development and shall be done taking into account the state transmission plan.

3.5

Planning criterion

3.5.1 Study of transmission system for wind power evacuation 3.5.1.1 The transmission system shall be adequate for various wind generation and load scenarios. The transmission system shall operate without violating any system conditions during following scenarios: i)

System Peak Load with High Wind Generation

{Explanation:During peak loading condition all the generating units in a region will be running at or near to its maximum capacity. Power flow through the transmission network will be at higher level. Evacuation planning of wind farm shall ensure that power injected by wind farm shall not cause any overloading/ congestion in the network during peak load condition. }

ii) System Light Load with High Wind Generation

{Explanation:Here, the aim is to ensure that during system light load condition, all the available wind power is evacuated. }

iii) Local Light Load with High Wind Generation

{Explanation:Sometimes wind farms can have significant local load near the wind farms. Here, the aim is to ensure that during local light load condition, all the available wind power is evacuated to the system. It is to be noted that low local load and low system load may not coincide in many parts of India due to geographical diversity. }


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As the wind farms are distributed over large geographical area, the maximum generation depends on geographical spread.

For scenarios mentioned in IWGC section-3.5.1, the “High Wind Generation” shall correspond to: i)

100% capacity factor for wind farms connected below 66kV.

ii) Minimum 90% capacity factor for wind farms connected at 66kV or 110 kV or 132 kV. iii) Minimum 80% capacity factor for wind farms connected above 132 kV.

{Explanation:Normally in India, plant load factors of wind farms would lie in the range of 2030%.But, capacity factor may go up to 100% in a small wind farm. So, to have economic viability, transmission planning of wind farms should consider capacity factor as a parameter. Wind turbines in a smaller wind farm face similar wind speeds as they are spread over smaller geographical area. Output of these wind farms can reach 100% of installed capacity during high wind season. As the wind farm size grows, capacity factor of wind farm decreases due to large geographical spread. Normally, higher capacity wind farms are connected at higher voltage levels. Here, voltage level at the grid connection point is chosen as criteria because power system behavior can be better categorized with voltage levels than power. 100%, 90%, 80% values are based on consultation experience and also available data from the literature. }

3.5.1.2 Generally there shall be no restriction on the wind farm size and the voltage level at which it shall be connected to the grid, provided all the requirements in this IWGC are fulfilled.

{Explanation:The relation between evacuating power and voltage level depends on many parameters, such as: - Local network and local load


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- Transmission conductor characteristics - Availability of substations

This relation can vary from one area to other. Providing a definite guideline on evacuating power vs. voltage relationship can restrict setting up of new wind farms in some areas where wind power can be evacuated reliably in spite of violating the “evacuating power and voltage” guideline. }

3.5.1.3 Lower ambient temperatures which are generally associated with higher wind velocities may be considered for increasing the loadability of transmission systems planned for evacuating wind power in cases where other alternatives are prohibitively expensive affecting viability of the renewable energy project. IEEE Std 738-1993 “IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors Contingency study " shall be followed while calculating line loadability with respect to wind speed. A sample calculation of transmission line loading with respect to wind speed is given in Appendix B. In Appendix B transmission line loading limits with increasing wind speeds are given for Zebra and Panther conductors.

3.5.2 Contingency study Plant load factors of wind farms are significantly less than the conventional generators. Hence, application of N-1 contingency criteria for planning of transmission line(s) from wind farm to grid substation may not be economically viable. Loss of generation from smaller wind farms may not have significant impact on the grid operation. 3.5.2.1 Planning of transmission lines from wind farms connected at 220 kV voltage level and above, to the grid substation shall be based on N-1 contingency criteria. However, wind farms connected below 220 kV voltage level and below 100 MW installed capacity at 220 kV voltage level can be exempted from N-1 planning criteria.

3.5.2.2 The upstream network connected from grid substation shall be capable of withstanding and be secured against the following contingency outages without necessitating load shedding or rescheduling of generation during steady state operation as defined in IEGC and State Grid codes a) Outage of a 132 kV D/C line or,


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b) Outage of a 220 kV D/C line or, c) Outage of a 400 kV S/C line or, d) Outage of single Interconnecting Transformer, or e) Outage of one pole of HVDC bipolar line, or f) Outage of 765 kV S/C line The above contingencies shall be considered assuming a pre-contingency system depletion (planned outage) of another 220 kV D/C line or 400 kV S/C line in another corridor and not emanating from the same substation. All the generating units may operate within their reactive capability curves and the network voltage profile shall also be maintained within voltage limits specified.

3.5.3 Any one of the events mentioned in the adequacy and contingency study shall not cause: i)

Unacceptable high or low voltage

ii) Prolonged operation of the system frequency below and above specified limits. iii) System instability iv) Unacceptable overloading of transmission system elements.

3.5.4 Reactive power compensation Reactive power compensation is important for wind farms to ensure reliable and trouble free grid operation and stable voltage profile. Adequate planning of reactive power compensation can minimize the reactive power loading on the transmission line. Further, there is a close relation exists between voltage instability and reactive power compensation. Hence, the reactive power compensation is to be addressed in the planning exercise and a careful study is required. 3.5.4.1 Reactive compensation of wind farms shall be able to maintain power factor between 0.95 lagging and 0.95 leading at grid connection point.

{Explanation: As per Indian state grid codes, power factor of conventional generators shall lie between 0.95 leading to 0.85 lagging. Wind grid codes of UK, Germany ask for 0.95 leading to 0.95 lagging power factor. Canadian grid code asks for 0.95 leading to 0.90 lagging power factor.


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So, it can be seen than grid codes mainly differ on the lagging power factor limit. In India, reactive power injection from wind farms is least expected. So, in IWGC the power factor range is limited between 0.95 leading to 0.95 lagging. }

3.5.4.2 Planning studies for power evacuation from wind farms through long distance transmission lines shall include voltage stability studies to investigate the requirements of dynamic VAr compensation to prevent voltage collapse during high wind generation. The modeling of WTG shall be based on the actual type planned to be installed in the area by the developer of wind farm. 3.6

Planning data

3.6.1 Wind farm owner shall provide planning data to CTU/STU as mentioned in Appendix A.

3.6.2 Wind power addition plan for every five years issued by the Ministry of New and Renewable Energy shall be considered for the planning of transmission lines of the CTU/STUs.


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Chapter 4

CONNECTION CODE FOR WIND FARMS This chapter comprises various technical requirements that wind farms have to satisfy for grid connection. These provisions shall apply for wind farms that are connected to the grid from dd/mm/yyyy. 4.1

Introduction The connection code for wind farms specify the minimum technical and design criteria which shall be satisfied by any wind farms seeking connection to ISTSs/STSs/STUs. This shall be pre-requisite for the establishment of an agreed connection.

4.2

Objective The objective of the connection code is to ensure that any new or modified wind farm connections, when established, shall neither suffer unacceptable effects due to its connections to ISTS/STS nor impose unacceptable effects on the system or the grid.

4.3

Scope The connection code applies to all wind farms connected to the grid at any voltage levels. The wind farms shall satisfy all requirements of connection code.

4.4

Procedure for connection The connection procedure of wind farms connected to ISTS shall follow IEGC section-4.4. Wind farms

connected to intra state lines

shall

follow

corresponding state grid code for connection procedure. 4.5

Connection agreement The connection agreement of wind farms connected to ISTS shall follow IEGC section-4.5. Wind farms

connected to intra state lines

shall

follow

corresponding state grid code for connection agreement. 4.6

Technical requirements to be met at grid connection point of wind farms The entire grid connected wind farms shall satisfy technical requirements at the grid connection point of the wind farm as mentioned in the following subsections.


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Indian Wind Grid Code –Version 1.0 4.6.1

July 2009

Transmission system voltage requirements

4.6.1.1 Transmission system voltage range The wind farms shall be able to deliver available or rated power when the voltage at the grid connection point remains within following range:

Table 4.1: Voltage withstand limits for wind farms

Voltage (kV) % Limit of

Nominal

variation

Maximum

Minimum

400

+5% to -10%

420

360

220

+11% to -9%

245

200

132

+10% to -9%

145

120

110

+10% to -12.5%

121

96.25

66

+10% to -9%

72.5

60

33

+5% to -10%

34.65

29.7

{Explanation: The minimum and maximum voltages for 400, 220 and 132 kV buses are taken from IEGC. The minimum and maximum voltages for 110, 66 and 33 kV buses are taken

from the planning criteria of Revised TNEGC(page 24) “The

permissible voltage at the point of commencement of supply during the steady state operation is +5% / -10% for system upto 33 kV voltage level…” . }

4.6.1.2 Resonance Wind farms shall avoid introducing undue resonance leading to over voltage at grid connection point. Of particular concerns are torsional interaction, self excitation of induction machines, transformer ferro-resonance, and the resonant effects of capacitor additions. Wind farms connected to the grid through series compensated transmission lines shall investigate the possibility of subsynchronous resonance due to torsional interactions.

4.6.1.3 Voltage unbalance Voltage unbalance is defined as the deviation between the highest and lowest line voltage divided by the average line voltage of three phases.


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Connection of a WTG to an unbalanced system will cause negative phase sequence current to flow in the rotor of the machine.

Wind farms shall be able to withstand voltage unbalance limits specified in following Table 4.2:

Table 4.2: Voltage unbalance limits

Voltage level (kV) Unbalance (%) 400

1.5

220

2

150

Installed Capacity/1.5 Installed Capacity/5 100

30

{Explanation: This is in line with international practice. As per Irish wind grid code grid the ramp rate averaged over 1 minute should not exceed 3 times the average ramp rate over 10 minutes. }

5.2.3.5 The ramping up/down of the wind power generation shall be done by the wind farm operator as instructed by the system operator. On case to case basis, the maximum ramp limits mentioned in IWGC section 5.2.3.4 may be changed on the mutual consent between the system operator and the wind farm operator provided the WTGs ramp limits are not exceeded.

5.2.4

Power quality All the wind farms connected to the grid shall endeavour to maintain the voltage wave-form quality at the grid connection point. The wind farms shall comply with the “IEC 61400-21: Wind Turbine Generator Systems, Part 21: Measurement and Assessment of Power Quality Characteristics of Grid Connected Wind Turbines” standard.


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{Explanation: Power quality in relation to a wind turbine describes the influence of a wind turbine on the power and voltage quality of the grid. The main influences of wind turbines on the grid concerning power quality are the voltage flicker, harmonics (for wind turbines with power electronic equipment), voltage changes & fluctuations and the in-rush currents. }

5.2.4.1Voltage flicker The IEC 61000-4-15 (IEC, 1997) and IEC 61000-4-15 (IEC, 2003) standards shall be followed with respect to voltage flicker limits and measurement techniques.

{Explanation: Flicker means the flickering of light caused by fluctuations of the mains voltage, which can cause distortions or inconvenience to people as well as other electrical consumers. The flicker measurement is based on measurements of three instantaneous phase voltages and currents, which are followed by an analytical determination of Pst (short-term flicker disturbance factor) for different grid impedance angles. }

5.2.4.2 Harmonics Harmonics measurements shall be taken in accordance with methodologies of IEC 61400-21 or IEEE STD 519-1992. The harmonic content at the grid connection point shall be as follows:

{Explanation: According to the guidelines (IEC 61400-21), harmonic measurements are not required for fixed-speed wind turbines (Type A), where the induction generator is directly connected to the grid. Harmonic measurements are required only for variable-speed turbines with electronic power converters (Types C and D). }

a) Harmonic content of the supply voltage is indicated by the following index: Total harmonic distortion of voltage = VTHD (expressed as percentage)


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VTHD =

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n = 40

Vn2 ×100 ∑ 2 n = 2 V1

Where Vn: nth harmonic of voltage V1: fundamental frequency (50 Hz) voltage The maximum limits of VTHD shall be as per the following Table 5.3: Table 5.3: Voltage harmonic limits

System Voltage Total Harmonic Individual Harmonic of any (kV)

Distortion (%)

Particular frequency (%)

765

1.5

1.0

400

2.0

1.5

220

2.5

2.0

132

3.0

2.0

b) Harmonic content of the supply current is indicated by the following index: Total Harmonic Distortion of current = ITHD (expressed as percentage)

ITHD

I n2 = ∑ 2 ×100 I1

Where In: nth harmonic of current I1: fundamental frequency (50 Hz) current The maximum limits of ITHD shall be as per the following Table 5.4: Table 5.4: Current harmonic limits

Voltage level 69 kV ITHD

5.0

2.5

{Explanation: The limits for VTHD are taken from CEA standards (Grid standards) Regulations-2006 and the limits for ITHD are taken from IEEE STD-519, 1992. }


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5.2.4.3 Voltage fluctuations The wind farm operation shall comply with the following permissible voltage fluctuation limits at the grid connection point. a) Voltage fluctuation limit for step changes which may occur repetitively is 1%. b) Voltage fluctuation limit for occasional fluctuations other than step changes is 2%.

{Explanation: The voltage fluctuations in a wind farm can occur because of the switching operations (capacitor banks, WTG start/stop), inrush currents during WTG starting etc. Such voltage fluctuations shall be limited to the values mentioned in the above section. }

5.2.5

Start and stop criteria

5.2.5.1 All the WTGs in a wind farm shall have the capability to receive the start/stop signal from the wind farm operator and shall respond to the signal without any time delay.

{Explanation: This is to necessitate the wind farm owner’s control over the WTG operation. The system operator may request the wind farm operator to start/stop the WTGs as the situation demands. So, the WTGs shall respond to the start/stop command send by wind farm operator without any time delay. }

5.2.5.2 During the wind generator start-up, the wind farm operator shall ensure that the reactive power drawl (inrush currents incase of induction generators) shall not affect the grid performance.

{Explanation: Fixed speed WTGs directly connected to the grid directly draws huge inrush current during starting. This may cause voltage fluctuations and flickering at the grid connection point. }


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5.2.5.3 The wind farm operator has to ensure that the start up and stopping of the WTGs comply with the voltage quality requirements.

{Explanation: Because, the switching operations and the inrush currents may cause harmonics, voltage flicker and voltage fluctuations. }

5.2.5.4 It is recommended that all WTGs in the wind farm shall not start and /or stop simultaneously owing to high windy conditions.

{Explanation: Simultaneous starting/stopping of the WTGs can cause power quality problems. Also, it can cause large changes in the power injected into the grid. }

5.2.6

Operation during transmission congestion During network congestion the wind farm operator shall act according to the instructions given by system operators. System operator (SSLDC/ SLDC/ RLDC) shall make reasonable effort to evacuate the available wind power. System operator shall instruct wind farm operator to back down wind generation only as a last resort, in view of the fact that the variable cost for wind generation is all most equal to zero (just like overflowing reservoir mention in Merit Order Dispatch).

{Explanation: Taking into consideration the zero fuel costs and environmental issues, it is recommended to evacuate all the available wind generated power to the grid. During transmission congestion, the conventional generation shall be backed down. Under extreme conditions, when the wind power generated exceeds the system demand and when the local voltage limits are violated, it shall be the responsibility of the wind farm operator to back down sufficient amount of the wind generation, to maintain system security. This shall be done as per the system operator’s instructions. }


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Indian Wind Grid Code –Version 1.0 5.2.7

July 2009

Operation in emergency condition Under any emergency (faults in the vicinity of wind farms, loss of any of the wind farm equipment, faults within the wind farms) the wind farm operator’s prime priority shall be the grid security and shall act accordingly. Once the emergency has subsided, the wind farm operator shall take all recovery measures listed in IEGC section-5.8 to bring back the wind farm into normal operation and shall report the events to SLDC/RLDC as mentioned in IEGC section-5.9.

{Explanation: The wind farms shall be operated as an integrated part of the grid. The wind farm operator shall operate it deriving maximum benefits from the integrated operation. System security shall not be endangered because of the substandard/inefficient

operational

practices

of

the

wind

farms.

The

contingencies (loss of any of the wind farm equipment, faults within the wind farms) shall be attended by the wind farm operator, so that there is minimal damage to the wind farm equipment as well as the grid. For contingencies in the vicinity of the wind farm, the wind farm operator shall protect the wind farm equipment from any imminent damage and shall take necessary measures to mitigate the contingency. The measures can be riding through the fault or ramping down the generation till the contingency has been remove, running in island mode to meet the local demand etc. }

5.3

Demand estimation for operational purposes IEGC/ state grid codes describe the procedures/responsibilities of the SLDCs for demand estimation of active and reactive power. Wind energy forecasting described in IWGC section-5.10 shall be taken into consideration to meet the estimated demand.

{Explanation: The demand estimation for operational purposes is done on a daily/weekly/monthly basis. The wind forecasting data obtained by the day ahead forecasting can be useful in meeting the estimated demand. The hourly forecast data can also be used as a part of the scheduling and dispatching. }


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Indian Wind Grid Code –Version 1.0 5.4

July 2009

Demand management IEGC/ state grid codes describe the provisions to be made by SLDCs for demand curtailment in the event of insufficient generating capacity or in the event of breakdown or operating problems (such as frequency, voltage levels or thermal overloads) on any part of the grid. The demand management procedure of SLDC shall take into account variability of wind power generation.

{Explanation: In a power system wind power generation profile and system demand may not follow the same pattern. For e.g. system demand may be high when there is least possible wind generation. So, the demand management procedure shall consider the variations in the wind generation (can be known from the wind forecast data) to maintain power balance in system operation. }

5.5

Periodic reports IEGC/ state grid codes discuss the periodic reports issued by RLDC/SLDC to all constituents of the Region and RPC Secretariat requirements regarding grid operation. The reports shall also cover the wind power generation profile and injection to grid.

{Explanation: Periodic reports issued by RLDC give the description of the grid performance over a week/month. Wind generation in that region can also be included in the periodic reports, because that gives a picture of wind energy profile, demand met with wind generated power and also can be useful for evolving good operational practices in the future. } 5.6

Operational liaison The Operational liaison function is a mandatory built-in hierarchical function of the RLDC/SLDC and regional constituents, to facilitate quick transfer of information to operational staff and is specified in the IEGC section-5.6. The same shall be applicable to the grid connected wind farms.


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July 2009

{Explanation: Wind farms are through their communication interface shall exchange the information in relation to operations and/or events with SLDC/RLDC. It is the mandatory built-in hierarchical function of the RLDC and Regional constituents including the wind farms, to facilitate quick transfer of information to operational staff for decision making and actions to be sought. }. 5.7

Outage planning IEGC/ state grid codes set out the procedure for preparation of outage schedules for the elements of the regional grid in a coordinated and optimal manner keeping in view the regional system operating conditions and the balance of generation and demand. The outage planning of wind farm and its associated evacuation network shall be planned to extract maximum power from the wind farm.

{Explanation: The outage schedules prepared by the RPC Secretariat based on the inputs from all the SEBs/STUs, CTU and ISGS. Wind farms shall also submit their outage schedule(s), if any, to the concerned SEB/STU. The wind farm operator shall also be aware of the planned/maintenance outages taking place around the vicinity of the wind farm, so that these outages do not have any effect on the wind power generation. } 5.8

Recovery procedures IEGC/ state grid codes specify the recovery procedures i.e., restoration of the operation of the regional grid after severe disturbances, partial/total blackouts that are developed by RLDC in consultation with all regional constituents/RPC Secretariat. The grid connected wind farms shall comply with these recovery procedures and shall abide by the guidelines of RLDC/SLDC during the restoration process.

5.9

Event information The entire grid connected wind farms shall follow the event reporting procedure mentioned in IEGC section-5.9.


38


5.10

July 2009

Scheduling process As the penetration of wind power increases, the scheduling of other generating plants would be have consider the availability of wind generation. Hence, it would be necessary to carry out wind energy forecasting to know the predicted wind power in next day on hourly basis so as to minimize the scheduling errors. .

5.10.1 Forecasting Wind being of intermittent nature, needs to be predicted with reasonable accuracy

for

proper

scheduling

and

dispatching

generation

in

the

interconnected system. Hence wind forecasting is necessary for increased penetration. Centralized wind forecasting facility shall be provided in an area with aggregated capacity of 200 MW and above. The Centralized wind forecasting system shall forecast the wind flow over a certain geographic area (for a cluster of wind farms) and it shall be installed in consultation with SSLDC/SLDC/RLDC. The centralized wind forecasting facility shall be built and operated either by the system operator or wind developers in the area and sharing of the cost shall be mutually discussed and agreed.

The wind energy forecasting system shall forecast power based on wind flow data at the following time intervals: i)

Day ahead forecast: Wind power forecast with an interval of one hour for the next 24 hours for the aggregate wind farms.

ii) Hourly forecast: Wind power forecast with a frequency of one hour and interval of 30 minutes for the next 3 hours for the aggregate wind farms.

The day ahead forecasting shall be done to assess the probable wind energy that can be scheduled for the next day. The hourly forecast is necessary to minimize the forecasting error that can occur in the day ahead forecasting of wind power. The SSLDC/SLDC/RLDC shall receive the forecasted wind power data which shall be used for scheduling.

Wind energy forecasting system shall be implemented within the time specified by the concerned authority with due consideration of penetration level, cost and tariff.


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July 2009

{Explanation: Wind energy forecast corresponds to an estimate of the expected amount of power production from wind farms over the forecast period. Evacuation of large amounts of energy from intermittent sources like wind has considerable effect on the generation-demand balance of a power system. So, for reliable system operation wind energy forecasting is necessary for larger wind farms. As the penetration level increases, it becomes difficult for the system operator to maintain the correct generation mix. As the system operator is responsible for maintaining balance between generation and demand, he should know in advance the amount of wind generated power that can be scheduled and dispatched from the wind farm, much like the conventional generation scheduling and dispatching.} 5.10.2 Scheduling The scheduling of other generators by the SLDC/RLDC shall consider the available wind generation for the duration. While scheduling generating stations in a region, system operator shall aim at utilizing available wind energy fully and the Merit Order dispatch shall not be applied for wind farms. The wind farms shall be treated as over-flowing reservoir/run of the river hydro power plants as defined in Tamil Nadu Electricity Grid Code. 5.11

Spinning reserve/ backup generation The spinning reserve/ backup generation shall be necessary to account for the wind power forecasting error and to meet the sudden loss of wind power generation (due to contingency).The amount of the spinning reserve/ backup generation that is to be maintained shall be decided by the SSLDC/SLDC/ RLDC based on the wind power forecast information.

{Explanation: Keeping a certain amount of energy as spinning reserve/backup generation is necessary to ensure that sufficient generation can maintained to meet the demand incase of an unexpected loss of wind generation. Also to meet the uncertainty in wind energy forecasting (forecasting error) the spinning reserve/ backup generation is necessary.}


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July 2009

APPENDIX A Planning Data (Wind farm) The following data are to be made available to the planning wing of CTU/STU by all the wind farms A.1

Name of the Wind Farm

A.2

Wind Farms capacity i)

Total installed capacity

ii) Number of units and unit size A.3

Site map Provide the location map to scale showing roads, railway lines, transmission lines, rivers, reservoirs.

A.4

Wind farm type i)

Type of wind turbines used in the wind farm Fixed Speed/Variable Speed.

ii) Type of wind farm operation- continuous or seasonal. iii) Expected high wind and low wind seasons and MW generation output from the wind farm during these periods. A.5

Wind Turbine data

Data type

Unit

Wind turbine manufacturer

-

Wind turbine generator type

-

Rated power of each wind turbine

kW

Rated apparent power

kVA

Rated frequency

Hz

Frequency tolerance range

Hz

Rated wind speed

m/s

Cut-in wind speed

m/s

Cut-out wind speed

m/s

Rated voltage

Volt

Rated current

Ampere

Value

Short circuit ratio Synchronous speed

RPM


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July 2009

Rated slip Magnetizing reactance of generator

p.u

Stator leakage reactance

p.u

Stator reactance

p.u

Rotor leakage reactance

p.u

Rotor reactance

p.u

Magnitude of inrush current Time duration of inrush current

Ampere s

In addition to the above mentioned data, the wind farm owner has to provide dynamic model of wind farm. If all the WTGs in the wind farm are not identical, the model shall incorporate separate modules to represent each type of WTG. Appropriate data and parameter values must be provided for each model. The dynamic model must represent the features and phenomena likely to be relevant to angular and Voltage stability. These features include but may not be limited to: i)

Generator model

ii) Blade pitch control iii) Model of drive train iv) Model of converter (if any) A.6

Reactive compensation Give detail of reactive compensation, operating power factor range.

A.7

Wind Turbine transformer data i)

Transformer voltage ratio

ii) Percentage impedance iii) Winding connection iv) Tap settings (if any) A.8

Grid connecting transformer data i)

Transformer voltage ratio

ii) Percentage impedance iii) Winding connection iv) Tap settings (if any)


42

Indian Wind Grid Code –Version 1.0 A.9

July 2009

Power evacuation scheme The following documents are to be furnished: i)

Single line diagram of power evacuation scheme.

ii) Details of conductor used for power evacuation


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July 2009

APPENDIX B Conductor ampacity calculation and variation with wind speed In IEEE Std 738-1993[1], “IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors”, a simplified method of calculating the current-temperature relationship of bare overhead lines, given the weather conditions, is presented. This appendix gives an example for the steady-state thermal rating (ampacity) calculation. It also gives loadability of Zebra and Panther conductors with respect to varying wind speed. B.1 Problem statement: To find the steady-state thermal rating (ampacity) for a Drake conductor, 795 kcmil 26/7 ACSR, under the following conditions:

a) Wind velocity, V, is 2 ft/s at sea level perpendicular to the conductor. b) Emissivity, ε is 0.5. c) Solar absorptivity, α, is 0.5. d) Ambient air temperature, Ta, is 40 °C. e) Maximum allowable conductor temperature is 65 °C . f) Conductor outside diameter, D, is 1.108 in. g) Conductor ac resistance, R (Tc), is: R (20 °C) = 2.177 x 10 -5 Ω /ft R (75 °C) = 2.648 x 10 -5 Ω /ft h) The line runs in an East-West direction. i) Latitude is 30°N. j) Atmosphere is clear. k) Average sun altitude, Hc, between 10:00 am and 12:00 noon. B.2 Calculation: The natural convection heat loss is calculated by means of equation (1): 0.75 Convected heat loss, qc = 0.283ρ 0.5 (Tc − Ta )1.25 W/ft ---------------------------- (1) f D

Where, Conductor diameter, D =1.108 in Ambient temperature, Ta =40o C Conductor temperature, Tc =65o C Air film temperature (°C) T

film =

(Tc + Ta)/2 = 52.5 °C


44


Density of air,

July 2009

ρ f =0.06775 lb/ft3 (from Table1 of IEEE Std. 738 at 52.5 o C)

Therefore, substituting the above values in equation (1) gives, qc = 4.48 W/ft Since the wind velocity is greater than 0 ft/s, the forced convection heat loss for perpendicular wind is calculated according to both equations (2) and (3) corrected for wind direction, and compared to the natural convection heat loss. The larger of the heat losses due to both natural and forced convection is then used in calculating the thermal rating:

  D ρ f VW qc1 = 1.01 + 0.371  µf     D ρ f VW qc 2 = 0.1695   µf 

  

0.52

  k f (Tc − Ta ) ---------------------------- (2)  

0.6

  k f (Tc − Ta ) ----------------------------- (3) 

Where, D = 1.108 in Velocity of air stream, VW = (2 ft/s) · 3600 (s/h) Tc =65o C Ta =40o C Absolute viscosity of air, µf = 0.04775 lb/h (ft) (Table1 of IEEE Std. 738 at 52.5 °C) Density of air,

ρ f =0.06775 lb/ft3 (from Table1 of IEEE Std. 738 at 52.5 o C)

Thermal conductivity of air at temperature, kf = 0.00858 W/ft (°C) (from Table1 of IEEE Std. 738 a t 52.5 °C) Therefore, substituting the above values in equation (2) and (3), gives qc1 = 10.421 W/ft qc2 = 9.837 W/ft Therefore, qc= 10.421 W/ft of conductor Since the wind is perpendicular to the axis of the conductor, the wind direction multiplier, Kangle, is 1.0, and the forced convection heat loss is greater than the natural convection heat loss. Therefore, the forced convection heat loss will be used in the calculation of thermal rating.


45


July 2009

B.3 Radiated heat loss (qr):

 (T + 273)  4  (T + 273) 4  a qr = 0.138 Dε  c  −   ----------------------------- (4)  100   100   Where, D = 1.108 in

∈ = 0.5 Tc = 65 °C Ta = 40 °C Radiated heat loss, qr = 2.64 W/ft of conductor Solar heat gain

qs = α Qs ( sin θ ) A' ----------------------------- (5) Effective angle of incidence of the sun's rays,

θ = cos −1 ( cos H c ) . ( cos ( Z c − Z1 ) )  ----------------------------- (6) Where, Solar absorptivity, α = 0.5 Projected area of conductor, A' =D/2= 0.092 ft From Table 2 of IEEE Std. 738 at 30° North latitude : Altitude of sun, Hc at 10:00 am = 62° Hc at 12:00 noon = 83° Hc at 11:00 am = (83°+62°)/2 = 72.5° Azimuth of sun, Zc at 10:00 am = 98° Zc at 12:00 noon = 180° Zc at 11:00 am = (98°+180°)/2 = 139° From Table 3 of IEEE Std. 738, Hc = 72.5° with a clear atmosphere: By interpolation, Qs= 95.2 W/ft Azimuth of line, Zl=90° or 270° From equation (5), qs= 4.293 W/ft of conductor From equation (6), θ =78.62°


46


July 2009

B.4 Resistance at 65° C

 R(75) − R(20)  R(65)=R(20)+  ( 65 − 20 )  75 − 20  = 2.313 x 10–5 Ω /ft B.5 Steady-state thermal rating The steady state thermal loading is given by, I =

qc + qr − qs ---------------------- (7) R ( 65 )

qc = 10.421 W/ft of conductor qr = 2.64 W/ft of conductor qs= 4.293 W/ft of conductor R (65) =2.313 x 10–5 Ω /ft From equation (7), I = 615.7 A.

In general, the transmission line loading is a function of the following factors: i)

Conductor type

ii) Line length iii) Weather conditions The weather conditions that mainly impact the loading are the ambient temperature and the wind velocities. Though, the ambient temperature is directly related to the wind flow velocities, calculation have been made with varying wind velocity with constant ambient temperature and are presented in Table B1 for Zebra and Panther conductors. It is observed that with raise in wind speed, the ampacity of Zebra conductor would increase by an average of 50A for 0.5m.sec increase in wind speed. Further, it is noted that wind turbine would operate only with the wind speed above 4m/sec.


47


July 2009

Table-B1: Conductor ampacity variation with wind velocity

Conductor age< 1yr;Ambient temp: 40oC;Final temp:65oC Conductor ampacity (A) Wind speed (m/s) ACSR Zebra conductor

Panther conductor

0.5

687.43

439.91

1.0

793.69

509.64

1.5

876.81

557.75

2.0

945.79

601.88

2.5

1004.06

639.44

3.0

1054.96

672.23

3.5

1100.43

701.51

4.0

1141.71

728.08

Further, the relation between conductor ampacity and ambient temperature mentioned in CBIP Technical Report 77 of May 1991 is furnished in Table B2 [2].

Table-B2: Conductor ampacity variation with ambient temperature

ACSR Zebra (54/3.18mm AL + 7/3.18 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : upto one year Ambient Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Temperature(oC) 60 oC 65 oC 67 oC 75 oC 0.0 1090.3 1126.5 1140.5 1193.5 2.5 1067.8 1105.2 1119.5 1174.8 5.0 1044.9 1083.4 1098.4 1155.0 7.5 1021.4 1061.4 1076.8 1134.9 10.0 952.0 998.3 1013.1 1078.0 12.5 897.8 945.5 963.6 1030.5 15.0 839.4 891.2 910.5 982.4 17.5 784.9 840.7 861.8 963.1 20.0 766.2 823.4 844.8 947.8 22.5 708.9 771.3 794.4 903.6 25.0 658.3 724.1 749.1 864.1 27.5 604.0 701.2 728.0 826.6 30.0 541.7 647.5 677.2 783.2 32.5 503.8 596.1 628.7 742.6 35.0 495.0 588.9 622.0 737.3 37.5 378.6 495.6 535.1 667.4 40.0 352.2 477.6 518.6 654.3


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July 2009

ACSR Zebra (54/3.18mm AL + 7/3.18 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : one to ten years Ambient Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Temperature(oC) 60 oC 65 oC 67 oC 75 oC 0.0 1147.8 1187.4 1202.8 1261.2 2.5 1124.8 1165.5 1181.1 1241.5 5.0 1101.2 1143.1 1159.4 1221.4 7.5 1076.9 1120.4 1137.2 1200.7 10.0 1003.8 1051.8 1070.0 1138.9 12.5 948.8 998.5 1018.2 1091.3 15.0 885.4 941.4 962.5 1040.9 17.5 828.1 888.5 911.1 1018.2 20.0 809.0 870.8 894.0 1002.7 22.5 748.7 816.2 841.2 956.4 25.0 693.8 768.7 793.8 915.2 27.5 639.2 740.5 769.0 876.0 30.0 571.1 694.1 716.2 830.5 32.5 530.6 630.1 685.2 788.3 35.0 522.4 623.2 658.8 783.0 37.5 397.2 524.7 567.2 709.5 40.0 371.9 506.2 550.3 696.2

ACSR Zebra (54/3.18mm AL + 7/3.18 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : beyond ten years Ambient Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Temperature(oC) 60 oC 65 oC 67 oC 75 oC 0.0 1168.3 1207.0 1222.6 1282.8 2.5 1143.1 1184.9 1201.0 1263.0 5.0 1119.3 1162.3 1179.1 1242.8 7.5 1094.8 1139.4 1156.7 1221.9 10.0 1022.3 1071.4 1090.1 1160.6 12.5 965.7 1018.4 1038.5 1113.3 15.0 904.6 961.7 983.2 1063.3 17.5 847.7 909.1 932.2 1040.4 20.0 828.1 891.0 914.6 1024.5 22.5 768.3 836.7 862.2 978.4 25.0 713.5 787.5 814.9 937.3 27.5 659.5 760.9 790.7 898.2 30.0 594.2 704.9 737.3 853.0 32.5 551.9 651.3 686.6 810.8 35.0 542.1 643.2 679.9 804.6 37.5 420.5 546.63 589.0 732 40.0 394.3 527.1 571.1 717.9


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July 2009

ACSR Moose (54/3.53mm AL + 7/3.53 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : upto one year Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Ambient 60 oC 65 oC 67 oC 75 oC Temperature(oC) 0.0 1259.0 1301.8 1316.0 1379.8 2.5 1234.0 1277.2 1293.6 1357.6 5.0 1207.5 1252.1 1269.4 1335.1 7.5 1180.3 1226.7 1244.6 1311.8 10.0 1098.3 1149.7 1169.3 1242.3 12.5 1034.5 1089.9 1110.9 1188.7 15.0 965.5 1025.9 1048.3 1132.0 17.5 901.2 968.3 990.6 1080.2 20.0 880.0 948.7 971.6 1045.6 22.5 812.3 885.2 912.2 1011.0 25.0 750.3 829.7 858.9 964.4 27.5 689.2 775.9 807.4 920.3 30.0 914.6 711.7 746.4 868.8 32.5 541.1 650.4 688.5 821.1 35.0 534.5 645.0 683.6 817.1 37.5 384.9 530.1 577.3 732.6 40.0 358.4 511.7 560.5 719.5

ACSR Moose (54/3.53mm AL + 7/3.53 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : one to ten years Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Ambient o 60 oC 65 oC 67 oC 75 oC Temperature( C) 0.0 1328.6 1374.5 1392.2 1460.3 2.5 1302.0 1349.3 1367.5 1437.6 5.0 1274.7 1323.4 1342.4 1414.4 7.5 1246.8 1297.3 1316.8 1390.5 10.0 1160.3 1216.2 1237.5 1317.5 12.5 1093.2 1153.4 1176.3 1261.5 15.0 1020.7 1086.1 1110.6 1202.1 17.5 953.1 1023.7 1050.1 1148.0 20.0 931.4 1003.7 1030.7 1130.9 22.5 860.3 939.2 968.5 1076.1 25.0 795.3 881.1 912.7 1027.5 27.5 731.2 824.5 858.9 961.4 30.0 652.9 757.5 795.0 927.6 32.5 575.7 693.3 734.4 900.8 35.0 569.4 688.1 729.7 874.0 37.5 412.3 567.5 618.1 785.4 40.0 384.9 548.4 600.8 771.9


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July 2009

ACSR Moose (54/3.53mm AL + 7/3.53 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : beyond ten year Ambient Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Temperature(oC) 60 oC 65 oC 67 oC 75 oC 0.0 1350.7 1397.9 1418.1 1488.2 2.5 1323.9 1372.4 1391.1 1483.3 5.0 1296.4 1346.4 1365.8 1439.9 7.5 1268.1 1319.9 1340.0 1415.6 10.0 1182.4 1239.5 1261.4 1343.5 12.5 1115.7 1177.2 1200.6 1287.8 15.0 1043.8 1110.4 1135.4 1228.9 17.5 976.7 1048.5 1075.4 1175.2 20.0 954.4 1027.9 1055.4 1157.5 22.5 883.9 963.9 993.7 1103.1 25.0 819.3 906.1 938.1 1054.7 27.5 755.7 850.1 884.6 1008.8 30.0 678.5 783.5 821.2 955.3 32.5 602.5 719.6 761.2 905.8 35.0 594.3 613.6 754.9 900.7 37.5 443.2 595.4 645.8 813.5 40.0 414.6 575.0 627.1 798.9

ACSR Bersimis (42/4.57 mm AL + 7/2.54 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : upto one year Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Ambient o 60 oC 65 oC 67 oC 75 oC Temperature( C) 0.0 1498.6 1548.7 1568.0 1641.7 2.5 1467.9 1519.5 1539.3 1615.4 5.0 1436.5 1489.7 1510.4 1588.6 7.5 1404.2 1459.5 1480.8 1561.0 10.0 1304.6 1365.9 1389.3 1476.5 12.5 1227.1 1293.4 1318.6 1411.7 15.0 1143.4 1215.6 1242.6 1342.8 17.5 1065.3 1143.5 1172.7 1280.2 20.0 1040.6 1120.6 1150.5 1260.6 22.5 958.4 1046.1 1078.5 1197.1 25.0 883.2 978.8 1014.0 1140.9 27.5 809.0 913.7 951.7 1087.6 30.0 718.0 835.7 877.6 1025.3 32.5 627.9 761.1 807.4 967.7 35.0 622.1 756.4 803.1 964.2 37.5 434.8 614.6 672.3 860.9 40.0 404.2 593.9 653.5 846.3


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July 2009

ACSR Bersimis (42/4.57 mm AL + 7/2.54 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : one to ten year Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Ambient 60 oC 65 oC 67 oC 75 oC Temperature(oC) 0.0 1583.1 1638.0 1659.2 1740.6 2.5 1551.5 1608.0 1629.7 1713.6 5.0 1519.0 1577.2 1599.9 1686.0 7.5 1485.8 1546.1 1569.4 1657.6 10.0 1380.8 1447.6 1473.2 1569.0 12.5 1299.5 1371.6 1399.0 1501.2 15.0 1211.4 1289.9 1319.4 1429.2 17.5 1129.5 1214.3 1246.1 1363.7 20.0 1104.1 1190.9 1223.4 1343.7 22.5 1017.8 1112.8 1148.1 1277.4 25.0 938.9 1042.4 1060.5 1218.7 27.5 861.2 974.3 1015.5 1163.1 30.0 765.8 892.6 937.9 1098.1 32.5 671.5 814.6 864.5 1037.0 35.0 665.8 810.0 860.3 1034.5 37.5 470.1 661.7 723.4 926.5 40.0 438.3 640.7 703.9 911.4

ACSR Bersimis (42/4.57 mm AL + 7/2.54 mm Steel); Region-Northern; Max design temperature -60,65,67 and 75 oC; conductor age : beyond ten years Ampacity(A) Ampacity(A) Ampacity(A) Ampacity(A) Ambient o 60 oC 65 oC 67 oC 75 oC Temperature( C) 0.0 1610.2 1666.7 1688.5 1772.3 2.5 1578.3 1636.4 1658.5 1745.1 5.0 1545.6 1605.4 1628.7 1717.3 7.5 1512.0 1537.9 1597.9 1688.8 10.0 1407.9 1476.3 1502.5 1600.8 12.5 1327.1 1400.8 1428.9 1533.5 15.0 1239.8 1319.8 1349.9 1462.1 17.5 1158.5 1244.8 1277.2 1397.2 20.0 1132.4 1220.7 1253.8 1376.5 22.5 1046.9 1143.2 1179.0 1310.7 25.0 968.7 1073.3 1111.9 1252.2 27.5 891.6 1005.6 1047.2 1196.9 30.0 797.6 924.8 970.4 1132.3 32.5 705.0 847.6 897.7 1072.4 35.0 696.9 841.0 891.6 1067.3 37.5 509.5 696.6 757.9 961.3 40.0 476.3 693.3 736.7 944.8


52


July 2009

References: [1] IEEE Std 738-1993 “IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors”, by Transmission and Distribution Committee of the IEEE Power Engineering Society. [2] S.K.Sonee, “Assessment of Transfer Capability in the Indian Bulk Electric Power System”, GSIOAR07, 8th – 9th August 2007, IT-BHU, Varanasi.


53