- (1.) The petitioner, Southern Regional Load Despatch, has filed the present petition inter -alia seeking direction to SLDCs to ensure that LVRT setting of the available wind turbines is installed in terms of the Central Electricity Authority (Technical Standards for Grid Connectivity) Regulations, 2007. The petitioner has made the following prayers: (a) Direct SLDC to expedite implementation of contingency demand disconnection scheme for mitigating impact of sudden loss of wind generation in line with order dated 22.2.2014 in 120/MP/2011. (b) Direct the SLDC to ensure Data Acquisition System/Real Time data availability of their SCADA system as envisaged in the IEGC and extended geographically consolidated data to SRLDC. (c) Direct the SLDC to ensure that LVRT setting of the available wind turbines as prescribed in CEA (Technical Standards for Grid Connectivity) Regulations, 2007 amendment dated 15.10.2013. (d) Issue suitable guidelines for protection to be provided by the existing machines not having LVRT feature to mitigate the cascading effect on the grid during sudden loss of wind generation. (e) Direct proper forecasting and scheduling by Renewable Energy generators and demand estimation by SLDC in compliance with IEGC. (f) Direct SLDC to study line loading in the STU) network and ensure strict N -1 compliance by expediting works under progress, particularly wind evacuation system. (g) Direct CTU/STU/SLDC to ensure that the new units being commissioned and getting connected to the grid are fully complying with CEA (Technical Standards for Grid Connectivity) Amendment Regulations, 2013.
(2.) Gist of the submission of the petitioner is as under: (a) Wind generation in India has been systematically growing every year. As per the Centre for Wind Energy Technology. Ministry of New Renewable Energy (MNRE), the overall installed capacity up to 31.1.2014 is 20,226 MW out of which Tamil Nadu has highest installed capacity of 7,251 MW followed by Gujarat (3,384 MW) and Maharashtra (3427 MW). (b) In the Southern Region, there is Talcher Kolar HVDC as well as the upcoming Raigarh Pugalur HVDC in close proximity to the wind generators. The existing Raichur -Sholapur 765 kV inter -connector has high sensitivity to sudden change in Southern Region generation/load. In case the faults in the system are not cleared on time, it would result in an adverse impact on HVDC systems, inter -connectors and wind generators. This would result in cascading failures impacting the All India Grid. (c) During the meeting of the Forum of Regulators held on 27.6.2014, it was discussed that Variability and Intermittent Generation, Frequency fluctuations due to generation or load loss/poor Frequency Response Characteristics (FRC) of individual sub -systems, absence of Fault Ride Through (FRT) capabilities, low voltage situation and heavy wind injection are the challenges which are grappling the grid. (d) As per CEA report on 'Large Scale Grid Integration of Renewable Energy Sources -Way Forward' dated November, 2013, the basic technical challenge comes from the variability of wind and solar power affects the load generation balance and varying demand for reactive power, and has an impact on voltage stability. However, the burgeoning problem lies in the sudden loss of wind generation, which has a much more cascading effect as opposed to the gradual variability. In the Southern Region, due to the Grid Incidents (Gl)/Grid Disturbances (GD) in the recent past, there has been loss of wind generation by more than 800 MW as under: (e) During the above incidents, the loss of wind generation were primarily due to cascade tripping of wind mills which do not have Low Voltage Ride Through (LVRT) protection during momentary low voltage. This delayed clearance of fault by more than 450 m/s. In the absence of LVRT protection as well as contingency load disconnection scheme for loss of wind generation, the impact has been passed on to the grid within rush of power flow in the inter -regional links, operation of SPS on such links as well as drop in system frequency. Such instances poses threat to grid security since it involved compounding tripping, with severe oscillation on 765 kV Sholapur -Raichur link, thereby impacting the line loading across S1 -S2 and causing multiple SPS/UFR operations. On 5.6.2014, one of the instances led to tripping of 765 kV Sholapur -Raichur transmission line. (f) LVRT mechanism boosts the terminal voltage of the point of connection of the wind machine when there is a fault at the remote location to provide transient stability support. LVRT is the capability of the electrical device to operate through periods of lower grid voltage. (g) The Central Electricity Authority (Technical Standards for Connectivity to the Grid) (Amendment) Regulations, 2013 provides that wind generating station connected at voltage level of 66 kV and above shall remain connected to the grid when voltage at inter -connection point on any or all phases dips up to 0.15 Pu. However, no LVRT protection has been provided by the wind energy generators so far. As per the said regulations, the new generators connected with effect from the date of the Regulations i.e. 15.4.2014 are required to meet technical requirement by taking care of the impact of future addition. Moreover, it is silent on the way out required to mitigate the impact of the existing wind generators. (h) In the present scenario, major portion of wind generators operating without LVRT protection creates the risk of making any temporary faults in the transmission system in the situation of grid disturbance near wind energy areas. The level of risk is maximum in the State of Tamil Nadu followed by Karnataka and other States in Southern Region. On 5.6.2014, multiple trippings occurred at NLC TPS -II, which is a typical example to visualize such situations. Due to fault at Neyveli, the wind generators at Udumalpet area also responded with cascade tripping, thereby creating simultaneous crisis at more than one geographical location of the grid. Since 2009, SRLDC has been emphasizing the issue of Automatic Demand Management Scheme (ADMS) to mitigate the contingency of sudden loss of wind generation and the issue of LVRT requirement has been taken up for more than three years. (i) SRLDC filed Petition No. 120/MP/2011 seeking direction to Tamil Nadu Electricity Board (TNEB) to maintain grid security of the Southern Regional Grid by curbing overdrawal and to effect proper load management by TNEB. One of the primary reasons submitted by TNEB was sudden change in huge quantum of wind generation. In response, SRLDC explained that lack of contingency demand disconnection scheme matching the loss of wind generation is the root cause. After considering the submission of the parties, the Commission vide order dated 22.2.2014 in Petition No. 120/MP/2011 had directed TNEB to take necessary steps to implement ADMS to deal with the emergency situations such as sudden variation/loss of wind generation or forced outages, etc. and submit the monthly progress report to SRLDC and SRPC in this regard. SRPC convened special meetings in the regard and matter was taken up in all OCC meetings of SRPC and TCC. However, no tangible measures have been taken in this regard by TNEB. j) The issue needs to be taken up by STUs/DISCOMs/SLDCs with the concerned State Electricity Regulatory Commissions. The lines in wind intensive areas were often getting over loaded contributing to low voltages and fault was causing the pulling out of the generators. The State of Tamil Nadu needs to monitor the line loading/voltages in the critical areas and back down generation/curtail load as per the requirement. The evacuation issues also need to be addressed at the earliest. (k) The non -availability of real time data of wind generation to SLDCs is another important issue compounding the problem, particularly in Tamil Nadu. The real time data integration of wind generation to SLDC SCADA is far below 100%. Typical evidence is the cascade tripping of wind generation during NLC TPS -II instance, during which Tamil Nadu SLDC itself was not aware about the loss of wind generation for more than an hour. The availability of real time wind generation data in the State of Karnataka is better than other States having similar status as of Tamil Nadu. (l) Another prolonging issue, which has not been implemented since 2010, is the "Forecasting and Scheduling" of wind generation. Despite variation in the renewable energy sources, forecasting with fair accuracy can be done similar to other countries. As a system operator, the forecast error or deviation shall be as minimum as possible. However, the wind energy generators are encouraged for commencement of scheduling and getting expertise in forecasting and scheduling as the Central Electricity Regulatory Commission (Indian Electricity Grid Code) Regulations, 2010 as amended from time to time (Grid Code) permits flexibility upto 30% deviation. (m) Forecasting the power output of wind farms in the next hours or days is of prime importance for the management of a power system with high wind penetration. In the case for wind energy, the generation depends on weather conditions. Wind power forecasts are useful for power system scheduling, congestion management, storage management, reserves allocation and other functions. Wind farm operators also need forecasts to participate in a day -ahead electricity market or to plan maintenance of wind farms. However, it is observed that most of the wind generators are yet to commence the forecasting and scheduling practices. Moreover, the wind generators had filed appeals before various High Courts regarding technical limitations and commercial implication. In absence of proper forecasting and scheduling by renewable energy sources, SLDCs are not complying with the provisions of Regulation 5.3 of the Grid Code. (n) The growth of renewable energy sources in India is important, realizing the paramount need for a grid security. Anything hampering the secured operation of the grid would also impede the full growth of green energy. Therefore, the provisions with respect to scheduling, forecasting, demand estimation, contingency plans and protection system needs to be ensured. At present, in India renewable generation penetration is being done without ensuring essential features for integration with very large grid. The bird's eye view of present scenario is as under: (i) In Southern Region, about 10000 MW plus generation operates like infirm power injection. (ii) More than 80% of current capacity of wind generation operates without LVRT/FRT feature thereby adversely responding at low voltage either due to high load condition at wind pockets or any fault condition in different parts of the grid and becomes a source for grid incident. At present, 20% current installed capacity have LVRT. However, their settings are not uniformly matching with the provisions of the Central Electricity Authority (Technical standards for connectivity to the Grid) Regulation, 2007 as amended from time to time (CEA Technical Standards for Connectivity Regulations). (iii) Real time renewable energy data availability to the Load Despatch Centre SCADA system is partial. Major portion of Tamil Nadu wind data is manually entered/updated from SLDC Tamil Nadu periodically. (iv) None of the States has implemented contingency demand disconnection schemes to mitigate the sudden loss of wind generation. (v) Forecasting and Scheduling of renewable generation is still at the incubation stage. (vi) There is no evidence to the effect that demand forecasting is being done by SLDCs with the due consideration of weather forecast and its impact on renewable energy generation. (o) There is a need for contingency plan for sudden loss of wind generation. In order to reduce the delay in response and to ensure instantaneous load shedding, ADMS has to be in place to deal with contingencies. The contingency scheme to be implemented shall be different from the ADMS which is meant for regular load -generation balance in a time block interval.
(3.) The petition was admitted on 26.2.2015. Notices were issued to the respondents to file their replies. The Commission directed the petitioner to implead Wind Energy Association and Solar Power Association of Southern Region as party to the petition. During the course of hearing, the representative of Southern Regional Load Despatch Centre (SRLDC) submitted as under: (a) Regulation B2.(3) of the CEA Technical Standards for Connectivity Regulations provides that Low Voltage Ride Through (LVRT) is compulsory for machines installed after 15.4.2014, but for existing wind power generating stations, LVRT should be mutually discussed. It does not exempt any station from installing LVRT. (b) The issue of installing LVRT has been discussed from the time when the installed capacity of wind in Southern Region was 3000 MW. Presently, the installed capacity is around 13,000 MW. Out of this, 9000 MW wind capacity does not have LVRT. (c) No tangible action has been taken with regard to installation of LVRT. The responsibility of monitoring installation of LVRT has not been fixed under any Regulation.;