Grid Standards, Grid Connectivity Standards and Regulations on Installation & operation of meters

1. Grid Standards, Grid Connectivity Standards and Regulations on Installation & operation of meters Ajay Talegaonkar Superintending Engineer, NRPC

2. Regulations issued by CEA • Safety requirements for construction, operation and maintenance of electrical plants and electric lines Regulations 2011 • Measures relating to Safety and Electricity Supply Regulations, 2010 • Grid Standards Regulations 2010 • Installation and Operation of meters (Amendment) Regulations 2010 • Technical Standards for Construction of Electrical Plants and Electric Lines Regulations 2010 • Installation and Operation of meters Regulations 2006 • Procedure for Transaction of Business Regulations 2006 • Technical Standards for Connectivity to the Grid • Furnishing of Statistics, Returns And Information

3. Regulations under finalization • Technical Standards for Connectivity of the Distributed Generation Resources • Technical Standards for Construction of Electrical Plants & Electrical Lines Regulations (Amendment) • Technical Standards for Connectivity to the Grid (Amendment)

4. Legal Background • Section 73 of the Electricity Act, 2003: Empowers Authority to specify amongst others: - technical standards for connectivity to the grid - Grid Standards for O&M of transmission lines - conditions for installation of meters • Section 177 of the Act: reiterates powers of the Authority to make regulations and lists out regulations

5. Grid Connectivity Standards

6. Necessity • De-licensing of generation under the Electricity Act, 2003 • Prior to this Act, techno-economic clearance by CEA was required • Under the new Act, economic regulation by Regulatory Commissions- examination of capital cost (by CEA) no longer required • But to take care of technical aspects- necessity of Grid Connectivity Standards

7. Necessity …….. Contd. Section 7 of the Electricity Act, 2003: “7. Any generating company may establish, operate and maintain a generating station without obtaining a licence under this Act if it complies with the technical standards relating to connectivity with the grid referred to in clause (b) of section 73. ”

8. Applicability • Users, requesters, STUs, Generating Companies, Transmission Licensees, Distribution Licensees and Bulk Consumers • Connected to the grid at voltage level 33 kV and above.

9. Objective • Safety, integrity and reliability of the grid • No adverse effect from new connection (however, converse not necessarily true) • Advance information about standards to be met

10. General Connectivity Conditions • Request to be made for interconnection. • The requester to furnish data sought • Facilities for voice and data communication and transfer of on-line operational data • Requester and user to cooperate with the RPC on operational aspects. • Interconnection study • Connection agreement (in case of connection with transmission licensee, a tripartite agreement involving CTU/STU as well)

11. Standards for Connectivity- General • The effects of wind, storms, floods, lightening, elevation, temperature extremes, icing, contamination, pollution and earthquakes must be considered in the design and operation of the connected facilities • Sub-station grounding as per IEEE- 80. • Protection System and Co-ordination - Protection co-ordination by the RPC. - SPS to avert system disturbances. • Every generating station and sub-station connected at 220 kV or above to have DR and EL with time synchronization facility.

12. Standards for Connectivity- New Generating Units • AVR with digital control and PSS for Generators of 100 MW and above • All generating machines to have electronically controlled governing system with droop - 3 to 6% - Thermal units and 0 to 10%. - Hydro units • Voltage and current harmonics : IEEE Standard 519. • Power Factor: Units located near load centre : 0.85 lagging to 0.95 leading Units located far from load centre: 0.9 lagging to 0.95 leading (To be achieved with voltage variation of ± 5% of nominal, frequency variation of +3% and -5% and combined voltage and frequency variation of ±5%. However, for gas turbines, the above performance shall be achieved for voltage variation of ±5%)

13. Standards for Connectivity- New Generating Units ….contd. • Primary Response - Coal and lignite based units: 105% of MCR for short duration - Hydro units: 110% of rated capacity (subject to rated head being available) on continuous basis • For units greater than 100 MW: 2 independent sets of protections acting on two independent sets of trip coils fed from independent DC supplies. • Hydro generating units having rated capacity of 50 MW and above shall be capable of operation in synchronous condenser mode, wherever feasible. • Bus bar protection - At the switchyard of all generating station. • For hydro units, self-starting facility may be provided.

14. Standards for Connectivity- Existing Generating Units For generating units in existence on the date of implementation of Grid Connectivity Standards AVR and PSS for Generators of 100 MW and above (digital control not mandatory)

15. Standards for Connectivity- Transmission Line and Sub-Station • Bus bar protection on all sub-stations at and above 220 kV for all new sub-stations. (For existing sub-stations, this to be implemented in a reasonable time frame) • LBB protection for all sub-stations of 220kV and above. • Two main numerical Distance Protection Schemes for all the transmission lines of 220 kV and above for all new sub-stations (to be implemented in a reasonable time frame for existing lines)

16. Standards for Connectivity- Transmission Line and Sub-Station …….contd. Power Supply to Sub-Station Auxiliaries:  (a) for alternating current (AC) supply (for new sub-stations): • 220 kV and above: Two HT supplies from independent sources (one main, one standby) + an emergency supply from DG source. • 66 kV - below 220 kV: One HT supply and one DG source. • 33 kV - below 66 kV: One HT supply. (b) for direct current (DC) Supply (For new sub-stations): • For 132 kV and above: Two sets of batteries, each equipped with its own charger.  • For sub-stations below 132 kV: there shall be one set of battery and charger

17. Standards for Connectivity- Distribution Systems and Bulk Consumers • UFR and df/dt relays based load shedding in accordance with the decision taken in the RPC. • Not to depend upon the grid for reactive power support. The power factor of the distribution system and bulk consumer not less than 0.95. • Voltage and Current Harmonics: - THD for voltage at the connection point not to exceed 5% with no individual harmonic higher than 3%. - THD for current drawn from the transmission system at the connection point shall not exceed 8%. - These limits to be implemented in a phased manner. (Complete compliance not later than five years from the date of publication of these regulations in the official Gazette)

18. Standards for Connectivity- Distribution Systems and Bulk Consumers …..contd • The Voltage Unbalance at 33 kV and above: not to exceed 3.0%. • Voltage Fluctuation limits: - for step changes: 1.5%. - For occasional fluctuations other than step changes:3%. - These limits to come into force not later than five years from the date of publication of these regulations in the Official Gazette.

19. Grid Standards

20. Legal Background Section 34 of the Electricity Act 2003:  “34. Every transmission licensee shall comply with such technical standards, of operation and maintenance of transmission lines, in accordance with the Grid Standards, as may be specified by the Authority.”

21. Standards for O&M of Transmission Lines • Frequency band: 49.2 to 50.3 Hz or a narrower frequency band specified in the Grid Code • Also specifies upper limits for transient over voltages due to sudden load rejection • Maximum permissible values of voltage unbalance (1.5% for 765 kV & 400 kV and 2% for 220 kV) • Protection coordination by the RPC • “fault clearance time” (100 ms for 765 kV and 400 kV, 160 ms for 220 kV and 132 kV), breaker fail protection for tripping of all other breakers in the concerned bus-section to clear the fault in the next 200 milliseconds

22. Standards for O&M of Transmission Lines…contd Voltage limits during steady state operation

23. Standards for O&M of Transmission Lines…contd Harmonic Limits

24. Operational & Maintenance Planning Operational Planning By RPC based on past performance of grid Maintenance Planning • RPCs to prepare an annual maintenance plan for the generating stations and ISTS • Review and revision of the coordinated generation and transmission system maintenance plan in monthly OCC meetings • SLDC to coordinate for Intra-State transmission system • The generating company or transmission licensee to obtain the approval of the Appropriate LDC before actual shutdown

25. Instructions by LDCs • All operational instructions given by RLDCs and SLDCs through telephone, Fax, e-mail, etc to be given a unique operating code number. • Every RLDC and SLDC to maintain a voice recorder for recording and reproduction of conversation with time tag or stamp. • The record of instructions to be kept for at least six months.

26. Defense Mechanism UFR based load shedding • Plan to made by the RPC • All constituents to submit a detailed report of operation of these Relays to RLDC and RPC on daily basis • RPCs to carry out inspection of these Relays as and when required. Islanding Schemes •  RPCs to prepare Islanding schemes for separation of systems with a view to save healthy system from total collapse in case of grid disturbance

27. Grid Incidents "Grid Incident" means tripping of one or more power system elements of the grid which requires re-scheduling of generation or load, without total loss of supply at a sub-station or loss of integrity of the grid.  • Category GI-1: Grid incident due to tripping at 220 kV level (132 kV in NER) • Category GI-2: Grid incident due to tripping at 400 kV level and above (220 kV in NER)

28. Grid Disturbances “Grid Disturbance” means tripping resulting in total failure of supply at a sub-station or loss of integrity of the grid, at the level of transmission system at 220 kV and above (132 kV and above in the case of NER) • Category GD-1 - When less than 10% of the antecedent generation or load in a regional grid is lost; • Category GD-2 - Loss of generation or load >= 10% but < 20% • Category GD-3 - Loss of generation or load >= 20% but < 30% • Category GD-4 - Loss of generation or load >= 30% but < 40% • Category GD-5 - Loss of generation or load >= 40%

29. Reporting of events and grid disturbances • Any tripping of generating unit or transmission element, along with relay indications to be promptly reported to the Appropriate LDC • LDCs to disseminate information about such events. • RLDC to inform occurrence of the grid disturbance to the constituents immediately and to the concerned RPC at the earliest. • The grid disturbance resulting in failure of power supply to large areas in a State to be reported by the RLDC to the Authority within 24 hours. • RLDC to post on its website a brief preliminary grid disturbance report, indicating the affected area or system, extent of outage and the likely cause of initiation

30. Restoration of grid • RLDC in consultation with RPC to develop procedures for enabling restoration and normalisation of the Grid • SLDC to develop procedures accordingly for restoration of intra-State system • Restoration procedures to be reviewed following any addition of generating station or transmission line or at least once in two years

31. Exchange of operational data • Entities to furnish real time data as required by LDCs. • RLDC to furnish data to RPC as required by them to discharge their responsibilities. • All operational data, including disturbance recorder and event logger reports to be furnished by all Entities within 24 hours to the RLDC and RPC. • RLDC to classify the grid incidents and grid disturbances, analyse them and furnish periodic reports of grid incidents and grid disturbances to the RPC which shall recommend remedial measures to be taken.

32. Operational Data Records • Operational data to be preserved for at least three years. • Logbooks to be maintained by every manned switchyard and sub-station or at the control centre responsible for operation of the unmanned switchyard and substation. • All operations to be recorded in chronological order in such a manner that there shall be no over-writing and any mistake shall be neatly cut by a line and new words written thereafter. • A compendium of grid disturbances to be maintained by the RPC.

33. Inspection and Patrolling • All essential parameters, which indicate the healthiness of the equipment in a sub-station, to be inspected by the shift engineer once in each shift and periodically by the officer-in-charge. • Different patrolling schedules to be implemented by the transmission licensees for normal terrain, vulnerable terrain and most vulnerable terrain. • The patrolling schedules for ground inspection of live lines and tower top inspection of de-energised lines shall be separately issued by the licensees. • Maintenance works such as tree cutting and replacement of damaged insulators to be carried out immediately after patrolling, wherever required.

34. Maintenance • Preference to condition based maintenance for critical equipment • Time based maintenance: Periodicity of maintenance to be fixed based on normal area or polluted area or coastal area. • Maintenance of equipment in polluted and costal areas to be completed once before onset of winter and summer respectively. • The Thermo-vision scanning at 220 kV and above to be carried out at least once a year.

35. Maintenance…..contd. • The records of all maintenance to be kept in electronic form and hard copy and the next due date for maintenance to be marked. • Maintenance audit: An internal committee to verify whether actual maintenance works are carried out at site in compliance of the procedures and the policy of the Transco. The observations of the Committee to be put up to the management.

36. Disaster Management • A detailed procedure to be developed by the Entity and displayed prominently. Employees to be trained for disaster management. • This procedure to reviewed periodically and also mock exercises carried out. • The maintenance staff to be trained in emergency restoration procedures for managing major failures and breakdowns. Emergency Restoration System Each transmission licensee to have an arrangement for restoration of transmission lines of 400 kV and above and strategic 220 kV lines through the use of Emergency Restoration System to minimise the outage time in case of tower failures.

37. Training • Every person involved in O&M to be trained at the induction level and at least once in a year. • Every grid operator to undergo training in real time digital simulator and a refresher course at least once in two years.

38. Regulations on Installation & Operation of Meters

39. Legal Background Section 55 of the Act • No licensee to supply electricity, after the expiry of two years from the appointed date, except through installation of a correct meter in accordance with regulations to be made in this behalf by the Authority • The State Commission may extend the said period of two years for a class or classes of persons or for such area. • For proper accounting and audit in the generation, transmission and distribution or trading of electricity, the Authority may direct the installation of meters by a generating company or licensee at such stages of generation, transmission or distribution or trading of electricity and at such locations of generation, transmission or distribution or trading , as it may deem necessary.

40. Applicability • Applicable to meters installed and to be installed by all the generating companies and licensees who are engaged in the business of generation, transmission, trading, distribution, supply of electricity and to all categories of consumers. • Provide for type, standards, ownership, location, accuracy class, installation, operation, testing and maintenance, access, sealing, safety, meter reading and recording, meter failure or discrepancies, anti tampering features, quality assurance, calibration and testing of meters

41. Classification of Meters • Interface meter: For ABT accounting and accounting of customers permitted open access by the Appropriate Commission • Consumer meter: For accounting and billing to the consumer but excluding those consumers covered under Interface Meters • Energy accounting and audit Meter: meters used for accounting of the electricity to various segments of electrical system so as to carry out further analysis to determine the consumption and loss of energy therein over a specified time period

42. Ownership of Interface Meters (a) All interface meters installed at the points of Interconnection with ISTS to be owned by CTU. (b) All interface meters installed at the points of interconnection with Intra-State Transmission System excluding the system covered under sub-clause (a) above to be owned by STU. (c) All interface meters installed at the points of inter connection between the two licensees excluding those covered under sub-clauses (a) and (b) above to be owned by respective licensee of each end. (d) All interface meters installed at the points not covered above shall be owned by supplier of electricity

43. Location of Interface Meters

44. Meter reading and recording Responsibility of the Appropriate Transmission Utility or the licensee • To take down the meter reading, maintain database of all the information associated with the interface meters • To verify the correctness of metered data and • To furnish the metered data to various agencies as per the procedure laid down by the Appropriate Commission.

45. Interface Meter - Failure or Discrepancies (a) When difference between Main and Check meter for any month is more than 0.5%, following steps shall be taken:   (i) checking of CT and VT connections; (ii) testing of accuracy of interface meter at site with reference standard meter of accuracy class higher than the meter under test.   If the difference persists, the defective meter shall be replaced with a correct meter.   (b) In case of conspicuous failures like burning of meter and erratic display of metered parameters and when the error found in testing of meter is beyond the permissible limit of error provided in the relevant standard, the meter shall be immediately replaced with a correct meter.   (c) In case where both the Main meter and Check meter fail, at least one of the meters shall be immediately replaced by a correct meter.

46. Billing for the Failure period • The billing for the failure period as per the procedure laid down by the Appropriate Commission. • Readings recorded by Main, Check and Standby meters for every time slot to be analysed, cross checked and validated by the Appropriate Load Despatch Centre (LDC). • The discrepancies, if any, noticed in the readings shall be informed by the LDC in writing to the energy accounting agency for proper accounting of energy. • LDC to also intimate the discrepancies to the Appropriate Transmission Utility or the licensee, who shall take further necessary action regarding testing, calibration or replacement of the faulty meters in accordance with the provisions laid down.

47. Calibration and testing of Interface Meters • Mandatory testing at the time of commissioning • Testing at least once in five years or whenever abnormal or inconsistent (with adjacent meters) recording • Whenever there is unreasonable difference between the quantity recorded by Interface meter and the corresponding value monitored at the billing center via communication network, the communication system and terminal equipment shall be tested and rectified. • The meters may be tested using NABL accredited mobile laboratory or at any accredited laboratory and recalibrated if required at manufacturer’s works. • Testing and calibration of interface meters in the presence of the representatives of the supplier and buyer.

48. Standards for Interface meters • Static type, suitable for VTs having a rated secondary line-to-line voltage of 110 V and CTs with rated secondary current of I A or 5A. • The meters shall have a non-volatile memory in which the following shall be automatically stored: (i) Average frequency for each successive 15-minute block, as a two digit code (00 to 99 for frequency from 49.0 to 51.0Hz). (ii) Net Wh transmittal during each successive 15-minute block, upto second decimal, with plus/minus sign. (iii) Cumulative Wh transmittal at each midnight, in six digits including one decimal. (iv) Cumulative VArh transmittal for voltage high condition, at each midnight, in six digits including one decimal. (v) Cumulative VArh transmittal for voltage low condition, at each midnight, in six digits including one decimal. (vi) Date and time blocks of failure of VT supply on any phase, as a star(*) mark.

49. Standards for interface meters….contd • Data to be stored in meter for a period of at least ten days. • An optical port on its front for tapping all data stored in its memory using a hand held data collection device. • The meter shall be suitable for transmitting the data to remote location using appropriate communication medium. • Two reactive energy registers- one for the period when average RMS voltage >103% and the other for < 97%. • Export to be taken as +ve and import as –ve. • The meters shall also display (on demand), by turn, the parameters in a specified sequence.

50. Standards for interface meters….contd • In case any of line to neural voltage falls below 70%, the condition shall be suitably indicated and recorded. • Powered by VT secondary circuits, without the need for any auxiliary power supply. • Built-in calendar and clock, having an accuracy of 30 seconds per month or better. • The meters shall be totally sealed and tamper-proof, with no possibility of any adjustment at site, except for a restricted clock correction. • Only fundamental frequency quantities to be measured/computed. • The Main meter and the Check meter to be connected to same core of CTs and VTs.