Full Text
5964 GI/2026 (1)
REGD. No. D. L.-33004/99
The Gazette of India
CG-DL-E-04082026-275152
EXTRAORDINARY
PART III—Section 4
PUBLISHED BY AUTHORITY
No. 485] NEW DELHI, FRIDAY, JULY 31, 2026/SHRAVAN 9, 1948
CENTRAL ELECTRICITY AUTHORITY
NOTIFICATION
New Delhi, the 31st July, 2026
No. 12/X/STD(CONN)/GM/CEA.—The following draft regulations, which the Central Electricity Authority
proposes to make in exercise of the powers conferred by clause (e) of sub-section (2) of section 177 of the Electricity
Act, 2003 (36 of 2003), and in supersession of the Central Electricity Authority (Technical Standards for Connectivity
to the Grid) Regulations, 2007 and amendments thereof, except as respects things done or omitted to be done before
such supersession, are hereby published, as required under sub-section (3) of section 177 of the said Act, for the
information of all persons likely to be affected thereby; and notice is hereby given that the draft regulations shall be
taken into consideration after the expiry of a period of thirty days from the date on which copies of this notification, as
published in the Gazette of India, are made available to the public.
The objections or suggestions which may be received from any person with respect to the said draft regulations before
the expiry of the period specified above shall be considered by the Central Electricity Authority.
The objections or suggestions, if any, on the said draft regulations may be sent to the Chief Engineer , Legal Division,
Central Electricity Authority, 6th Floor, Sewa Bhawan, R.K. Puram, New Delhi – 110066, or through e-mail: celegal
[email protected] .
Draft Regulations
1. Short title and commencement: -
(3) These Regulations may be called the Central Electricity Authority (Technical Standards for Connectivity to
the Grid) Regulations, 2026.
(4) These Regulations shall come into force on the date of their publication in the Official Gazette.
2. Definitions: -
(3) In these regulations, unless the context otherwise requires: -
(i) "Act" means the Electricity Act, 2003 (No. 36 of 2003);
(ii) “Active Current Priority Mode” means a mode in which the active current output (Ip) is given
priority and has the full current rating of the generating station available to it (i.e., maximum current
ac, Imax), while the reactive current output (Iq) is constrained.
(iii) "Appropriate Load Despatch Centre" means the National Load Despatch Centre (NLDC), Regional
Load Despatch Centre (RLDC) or State Load Despatch Centre (SLDC) or Area Load Despatch
Centre as the case may be;
(iv) "Area Load Despatch Centre" means the centre as established by the state for load despatch and
control in a particular area of the state;
(v) "Appropriate Transmission Utility" means the Central Transmission Utility or State Transmission
Utility as the case may be;
(vi) “Asynchronous Generating Station” means a generating station comprising of asynchronous
generating unit(s);
(vii) “Asynchronous Generating Unit” means a Generating Unit, that is not a synchronous generating
unit.
(viii) "Automatic Generation Control (AGC)” means capability to regulate the power output of selectable
Generating unit(s) in response to total power plant output, tie-line power flow, and power system
frequency;
(ix) "British Standards (BS)” means those standards and specifications approved by the British
Standards Institution;
(x) "Bulk consumer" means a consumer who avails supply at voltage of 33 kV or above;
(xi) “Co-located generating station” means two or more generating stations, including energy storage
systems, that are operated and controlled as separate facility and are connected behind a single PoI;
(xii) “Collector system” means equipment and systems utilized in the aggregation of generating unit(s).
This includes switch-gear, cables, transmission lines, transformers, and reactive compensating
devices etc. between the generating unit(s) and the PoI;
(xiii) "Earth Fault Factor" at a location in a three-phase system means the ratio of the highest root mean
square (r.m.s.) phase-to-earth power frequency voltage on a sound phase during a fault to earth
(affecting one or more phases)to the r.m.s. phase-to-earth power frequency voltage which would be
obtained at the selected location without the fault;
(xiv) "Energy Management System” (EMS) means a complete system comprising software for facilitating
operation of a power system, maintaining safety, reliability and economy;
(xv) “Event Logging Facilities" means a device provided to record the chronological sequence of
operations of the relays and other equipment;
(xvi) “Energy Storage System (ESS)” in relation to the electricity system, means a facility where
electrical energy is converted into any form of energy which can be stored, and subsequently
reconverted into electrical energy and injected back into the grid such as Battery Energy Storage
System (BESS) and Pumped Storage Plant (PSP);
(xvii) “Energy Storage System (ESS) Unit” means
(a) an electrical generator coupled to a prime mover within a power station together with all plant and
apparatus at the power station which relate exclusively to operation of that generator in case of
Pumped Storage Plants (PSP);
Or
(b) battery module(s) connected under an inverter along with other equipment in respect of Battery
Energy Storage System (BESS);
(xviii) “Facility” means a specific type of equipment or installation that plays a role in power generation,
transmission, or distribution;
(xix) “Fast Frequency Response” means active power injected to the grid in response to changes in
measured or observed frequency during the arresting phase of a frequency excursion event to
improve the frequency nadir or initial rate-of-change of frequency;
(xx) “First Time Energisation” means the initial energisation of a new or modified power-system element
(for testing, commissioning and/or integration with the grid), carried out as per the procedure
prepared by appropriate load despatch centre;
(xxi) Flexible AC Transmission Systems (FACTS)” means alternating current transmission systems
incorporating power electronic-based and other static controllers to enhance controllability and
increase power transfer capability;
(xxii) "Frequency" means the number of alternating cycles per second [expressed in Hertz (Hz);
(xxiii) “Generating Unit” means
(a) a unit of a generating station having electrical generator coupled to a prime mover within a power
station together with all plant and apparatus at the power station which relate exclusively to
operation of that generator;
Or
(b) an inverter along with associated photovoltaic modules and other equipment in respect of generating
station based on solar photovoltaic technology;
Or
(c) a wind turbine generator with associated equipment, in respect of generating station based on wind
energy;
(xxiv) “Grid Forming (GFM)” means a control that maintains an internal voltage phasor that is constant or
nearly constant in the sub-transient to transient time frame;
(xxv) ‘HVDC system’ means an electrical power system which transfers energy in the form of high
voltage direct current between two or more alternating current (AC) buses;
(xxvi) “HVDC Converter Station” is a part of an HVDC System which consists of one or more HVDC
Converters installed in a single location together with buildings, reactors, filters, reactive power
devices, control, monitoring, protective, measuring and auxiliary equipment;
(xxvii) “Hybrid Generating Station” means a generating station comprising of a combination of
synchronous and asynchronous generating unit(s), with or without energy storage systems,
controlled and operated as a single generating station behind a single PoI;
(xxviii) “IEC Standard" means a standard published by the International Electrotechnical Commission;
(xxix) "Indian Standards" (IS) means standards specified by Bureau of Indian Standards;
(xxx) “Installed capacity”
(a) in case of coal, lignite, gas engines and hydro stations, means the summation of the name plate
capacities of all the unit(s) of the generating station or Maximum Continuous Rating of the
generating station;
Or
(b) in case of wind generating stations and generating stations using inverters, means the summation of
the name plate capacities of wind turbines or solar generating unit(s), as the case may be;
Or
(c) in case of ESS means the rated Peak Capacity (MW) and energy capacity (MWh) to be delivered to
the connected load;
(xxxi) "Inverter" means a device that changes direct current power into alternating current power;
(xxxii) “Inverter based resource (IBR)” means any source of electric power that is connected to the grid via
power electronic interface, and consists of one or more IBR unit(s) capable of exporting active
power from a primary energy source or energy storage system and a collector system or a
supplemental device may also be part of an IBR;
(xxxiii) IBR continuous rating (ICR): The steady-state, continuous active power rating of an IBR plant
guaranteed by the IBR owner at the PoI;
(xxxiv) “Inverter-based resource plant (IBR plant)” means a grouping of one or more IBR unit(s) and
possibly supplemental device(s) operated by a common facility-level controller along with a
collector system to achieve the performance requirements at the PoI;
(xxxv) “Inverter based resource unit (IBR unit)” means an individual inverter device or a grouping of
multiple inverters connected together behind a single PoI and for type III wind turbine generators,
the wind turbine itself, the doubly-fed generator, the rotor-circuit inverter, and the three-winding
unit transformer, if present, make up an IBR unit;
(xxxvi) “Inverter-Interfaced Bulk Consumer” means a bulk consumer who receives power through
electronic based converters for feeding the loads;
(xxxvii) "Isolator” means a device for achieving isolation of one part of an electrical system from the rest of
the system;
(xxxviii) “Line – Commutated Converter (LCC)” based HVDC converter means a converter that relies on the
line voltage of the ac system to which the converter is connected in order to affect the commutation
from one switching device to its neighbor and it uses switching devices that are either uncontrolled
(such as diodes) or that can only be turned on (not off) by control action, such as thyristors;
(xxxix) “Operating mode” means mode of IBR or IBR plant operation that determines the performance
during normal or abnormal conditions;
(xl) “Overshoot” means the maximum system output minus the final steady state value, divided by the
actual change in system output (i.e., from its initial value to the final settled value), when the final
settled value is within the defined settling band, expressed as a percentage of final steady state
value;
(xli) " Point of Interconnection (PoI)" means a point on the grid, including a sub-station or a switchyard,
where the interconnection is established between the facility of the requester /user and the grid and
where electricity injected into or drawn from the grid can be measured unambiguously for the
requester/user;
(xlii) ''Power Factor" means the cosine of the electrical angle between the voltage and current complex in
an AC electrical circuit;
(xliii) "Primary energy source” means energy sources like solar irradiance in the case of a photovoltaic
IBR, instantaneous wind energy (determined by wind speed at a given moment) in case of a wind
turbine generator, stored chemical energy in case of a Battery Energy Storage System (BESS), and
stored potential energy in case of Pumped Storage Plants (PSP);
(xliv) “Primary frequency response (PFR)” means the immediate and automatic adjustment of power
generation based on droop characteristics to stabilize the frequency deviations;
(xlv) "Protection System" means the equipment by which abnormal conditions in the grid are detected
and fault clearance, actuating signals or indications are initiated without the intervention by the
operator;
(xlvi) “Reactive Current Priority Mode” means a mode in which the reactive current output (Iq) is given
priority and has the full current rating of the generating station available to it (i.e, maximum current
ac, Imax), while the active current output (Ip) is constrained;
(xlvii) “Reaction time (Treact)” means the duration from a step change in a system quantity measured at a
defined location until the output of the system at the same defined location measurably changes in
the direction of the control effort;
(xlviii) "Reactive Power" means in relation to an AC electrical system, the product of root mean square
(r.m.s.) voltage, root mean square (r.m.s.) current and the sine of the electrical phase angle between
the voltage phasor and current phasor, as measured in volt-amperes reactive (VAr);
(xlix) “Requester” includes a generating company, captive generating plant, energy storage system, transmission
licensee (other than Central Transmission Utility and State Transmission Utility), distribution
licensee, or bulk consumer seeking connection to the grid for its new or expanded
electrical plant or Substation or Transmission line or any power system element at voltage level of
33 kV and above;
(l) “Ride-through” means ability to withstand voltage or frequency disturbances within the specified
limits and to continue operating as specified;
(li) “Rise time (Trise)” means the time for the output of a system to go from 10% to 90% of required
output change;
(lii) "SCADA" means Supervisory Control and Data Acquisition System that acquires data from remote
locations over communication links and processes it at centralised control location for monitoring,
supervision, control as well as decision support;
(liii) “Settling band” means the region around the value change where the system output is required to
settle in after a step change in a system quantity measured at a defined location;
(liv) “Settling time” means the duration from a step change in a system quantity measured at a defined
location until the output of the system settles to within a specified settling band around its final
value change at the same defined location;
(lv) "Site Common Drawing" means a drawing prepared for a connection site, which depicts layout of
connection site, electrical layout, common protection and control drawings and common services;
(lvi) "Site Responsibility Schedule" (SRS) means a Schedule for demarcating the ownership,
responsibility for control, operation and maintenance of the equipment at the PoI;
(lvii) “Step response” means the output of a system as a function of time when the input is a step function
of time also;
(lviii) “Step response time” means the time between the step change in a system quantity measured at a
defined location and when the output of the system reaches 90% of required output change, before
any overshoot;
(lix) “Supplemental device: means any equipment within a facility, that is only used to obtain compliance
with some or all of the technical requirements specified in these regulations;
(lx) “Synchronous Generating Station” means a generating station comprising of synchronous
generating unit(s);
(lxi) “Synchronous Generating Unit” means a generating unit which can generate electrical energy such
that the frequency of the generated voltage, the generator speed and the network voltage are in a
constant ratio and thus in synchronism;
(lxii) “Synchronous Condenser Unit” means a unit similar in construction to a Synchronous Generating
Unit which operates at the equivalent speed of the frequency of the power system to dynamically
generate or absorb reactive power to regulate voltage, improve the power factor, and provide
essential mechanical inertia, and, when operating in steady state conditions, neither generates nor
consumes active power other than consumption for losses within the unit;
(lxiii) "Total Harmonic Distortion" (THD) means a measure of distortion of the voltage or current wave
form (which shall ideally be sinusoidal) and is the square root of the sum of squares of all voltage or
current harmonics expressed as a percentage of the magnitude of the fundamental;
(lxiv) "Transmission System" means a network of transmission lines and sub-stations;
(lxv) “Type test” means a test of one or more devices manufactured to a certain design to demonstrate, or
provide information that can be used to verify, that the design meets the requirements specified in
this standard;
(lxvi) “Under Frequency Relay” means a relay which operates when the system frequency falls below a
preset value;
(lxvii) “user” includes a generating company, captive generating plant, energy storage system, transmission
licensee (other than the Central Transmission Utility and State Transmission Utility), distribution
licensee, or bulk consumer whose electrical plant or Substation or Transmission line or any power
system element is connected to the Grid at voltage level of 33 kV and above;
(lxviii) “Voltage Source Converters (VSC)” means a converter that has a forced commutated device (for
example, IGBT) based self-commutated converter that is capable of generating ac voltage from dc
capacitor voltages;
(lxix) "Voltage Unbalance" means the deviation between highest and lowest line voltage divided by
Average Line Voltage of the three phases;
(lxx) “Wind turbine generator (WTG)” means an IBR unit which converts the kinetic wind energy into
electric energy;
(2) Any other words, terms, definitions and symbols which are used herein and not defined in these regulations
shall have the same meanings respectively as assigned in the Act or any other regulation published by the
Authority.
3. Applicability of the Regulations:-
These regulations shall be applicable to all the users, requesters, Central Transmission Utility,
appropriate Load Despatch Centre and State Transmission Utility.
CHAPTER – I
GENERAL CONNECTIVITY REQUIREMENTS
4. The requester/user shall be responsible for the planning, design, construction, reliability, protection and safe
operation of its own equipment subject to the regulations for construction, operation and maintenance,
connectivity, and other statutory provisions.
5. The new connection shall not cause any adverse effect on the grid. The grid shall continue to perform with
specified reliability, security and quality as per the Central Electricity Authority (Grid Standards) Regulations
in force. However, these regulations are not to be relied upon to protect the plant and equipment of the
requester/ user.
6. A requester is required to be aware, in advance, of the standards and conditions his system has to meet for
being integrated into the grid.
7. The requester/user shall participate in contingency operations such as load shedding, increasing or reducing
generation, islanding, black start, providing start-up power and restoration as per the procedure decided by
the Appropriate Load Despatch Centre.
8. The requester/ user shall carryout modifications in his equipment with respect to short circuit level,
protection coordination and other technical reasons considered necessary due to operational requirements.
9. Site Responsibility Schedule:
(1) A Site Responsibility Schedule (SRS) for every connection point shall be filled by the requester/user
operating the facility at which connection is taking place.
(2) The appropriate transmission utility or distribution licensee shall publish the proforma for Site Responsibility
Schedule (SRS) to be filled by the requester/user.
(3) Following information shall be included in the Site Responsibility Schedule, namely, —
(i) Schedule of electrical apparatus services and supplies;
(ii) Schedule of telecommunications and measurement apparatus; and
(iii) Safety rules applicable to each plant and apparatus.
(4) Following information shall also be furnished in the Site Responsibility Schedule for each item of equipment
installed at the connection site, namely: —
(i) the ownership of equipment;
(ii) the responsibility for control of equipment;
(iii) the responsibility for maintenance of equipment;
(iv) the responsibility for operation of equipment;
(v) the manager of the site;
(vi) the responsibility for all matters relating to safety of persons at site; and
(vii) the responsibility for all matters relating to safety of equipment at site.
10. Access at Connection Site:
The requester or user, as the case may be owning the electrical plant shall provide reasonable access and
other required facilities to the licensee or Appropriate Transmission Utility or Appropriate Load Despatch
Centre, whose equipment is installed or proposed to be installed at the Connection Site for installation,
operation and maintenance, etc. of the equipment.
11. Site Common Drawings:
Site Common Drawings shall be prepared for each connection point by the owner of the Sub-station where
connection is taking place.
12. Cyber security:
(1) The requester/user shall comply with cyber security guidelines, regulations and the technical
standards for communication system in power sector laid down by the Authority.
(2) The requester/user shall also comply with cyber security guidelines/orders issued by the Central
Government, CERT-In, NSCS, NCIIPC from time to time.
13. The requester/user shall prepare single line schematic diagrams in respect of its facility and make the same
available to the Appropriate Load Despatch Centre, Appropriate Transmission Utility or licensee through
which his system is connected.
14. The requester/user shall follow the industry best practices and applicable industry standards in respect of the
equipment installation and its operation and maintenance.
15. The equipment including overhead lines and cables shall comply with the relevant Indian Standards and in
absence of Indian Standard, International Electrotechnical Commission Standard, Institute of Electrical and
Electronic Engineers Standard, European Norms Standard in the sequence of their appearance unless stated
otherwise:
Provided that whenever an International Electrotechnical Commission Standard, Institute of Electrical and
Electronic Engineers Standard, European Norms Standard is followed, necessary corrections or modifications
shall be made for nominal system frequency, nominal system voltage, ambient temperature, humidity and
other conditions prevailing in India before actual adoption of the said Standard.
16. The equipment shall meet the requirements in accordance with the provisions specified in these
regulations and other technical regulations published by the Authority.
17. 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 for
compliance of the provisions specified in these regulations.
18. All the provisions contained in these regulations shall be complied and met by the facility at the PoI.
19. The name plate rating, at specified environmental conditions, of various equipment including
transformers within the facility shall be used while assessing the compliance at PoI with the provisions
specified in these regulations.
20. There shall be no collector system limitation, internal network limitation, control system limitation,
protection system, environmental conditions or other limiting device in operation that would prevent the
facility from meeting the technical requirements at PoI specified in these regulations.
CHAPTER – II
REQUIREMENTS FOR GENERATORS AND ESS
Synchronous Generating Station
Active Power Capability
21. The generating station shall be capable of providing the summation of Maximum Continuous Rating (MCR)
capacity of generating unit(s) minus the declared auxiliary consumption at PoI.
22. Automatic facilities shall be provided in the generating station.
Reactive Power Capability
23. The generating station shall be capable of supplying and absorbing dynamically varying reactive power
compensation at the PoI commensurate to 61.97% (0.85 pf) of summation of MCR capacity of generating
unit(s) in lagging (over-excited) condition to 32.87% (0.95 pf) of summation of MCR capacity of generating
unit(s) in leading (under-excited) condition of generating station:
Provided further that the above performance shall also be provided on a continuous basis with voltage
variation of ±10% of nominal, frequency variation of (+) 4% and (-)5% and combined voltage and frequency
variation of ±5%. However, for gas turbines, the above performance shall be provided on a continuous basis
for voltage variation of ±5%.
Voltage Disturbance Ride Through
24. The generating station shall be able to operate for Short Circuit Ratio as per IEC 60034.
25. The generating station shall operate continuously in the voltage range 0.9 p.u to 1.1 p.u at the PoI and be able
to deliver the summation of MCR capacity of generating unit(s).
26. Voltage disturbances of any duration, for which the applicable voltage remains within the continuous
operation region, shall not cause the generating station or unit(s) to trip. The generating station or unit(s)
shall remain in operation during any such disturbance, and shall continue to deliver pre-disturbance level of
active power or available active power, whichever is less.
27. All instantaneous under / over voltage protection used within the generating station shall use filtered
quantities to reduce the possibility of mis-operation while providing protection to the desired equipment and
system. Any instantaneous under /over voltage protection(s) that has the possibility of disrupting the power
output of the entire generating station shall use at least one cycle (of fundamental frequency) measurement
window to reduce such possibility and the related impact on the grid.
Low Voltage Ride Through (LVRT)
28. The generating station connected to the grid, shall remain connected to the grid for the duration
corresponding to the under voltage at the PoI on any or all phases (symmetrical or asymmetrical under
voltage conditions) as depicted by the thick line in the curve in Fig. 1
Vt : Actual Voltage; Vn: Nominal Voltage—
Fig 1. Low Voltage Ride Through requirements for Synchronous Generating station
Note: The relevant voltage shall be the lowest magnitude fundamental frequency phasor component of the
phase-to-phase or phase-to ground voltages, whichever is less, at the PoI relative to the corresponding
nominal voltage.
The response of the generating station shall be stable if the voltage is outside the continuous operation limits
indicated in the Fig. 1. above:
Provided that during the low voltage ride through conditions, Generating Station shall have the overload
(current) capability as per IEC 60034.
High Voltage Ride Through (HVRT)
29. The generating station connected to the grid, shall remain connected to the grid for the duration
corresponding to the overvoltage at the PoI, on any or all phases (symmetrical or asymmetrical overvoltage
conditions) as depicted by the thick line in the curve in Fig. 2
Fig. 2. High Voltage Ride through requirements for synchronous generating station
Note: The relevant voltage shall be the greatest magnitude fundamental frequency phasor component of the
phase-to-phase and phase-to ground voltages, whichever is high, at the PoI relative to the corresponding
nominal voltage.
The response of the generating station shall be stable if the voltage is outside the continuous operation limits
indicated in the Fig. 2 above.
Multiple Fault Ride Through (MFRT)
30. The generating station connected to the grid, shall remain connected to the grid for a series of up to 15
voltage disturbance below 0.9 p.u within any 5-minute period as per the LVRT capability:
Provided that during such period generating station shall remain connected for at least 06 voltage disturbance
below 0.5 p.u:
Provided further that during the multiple LVRT conditions, the generating station shall meet the performance
requirements specified in LVRT conditions.
31. While assessing multiple voltage disturbances, a fault that is re-established following operation of automatic
re-close Protection Scheme shall be counted as a separate voltage disturbance.
Frequency Ride through
32. The generating station shall be capable of operating in the frequency range 47.5 to 52 Hz and be able to
deliver the summation of MCR capacity of generating unit(s) in the frequency range of 49.5 Hz to 50.5 Hz on
a continuous manner:
Provided that the generating station shall be able to maintain its performance contained in this sub-clause
even with voltage variation of up to (+/-) 10%:
Provided further that there shall be a provision of keeping over-frequency settings above 52 Hz in case of
hydro generating stations.
Active Power Control
33. The generating unit(s) of aggregate capacity of100 MW and above at PoI shall have the provision to receive
the signal from the State Load Despatch Centre or Regional Load Despatch Centre, as the case may be, for
varying active power output.
34. All generating unit(s) irrespective of capacity shall have electronically controlled governing systems with
appropriate speed/load characteristics to regulate frequency. The governors of thermal generating unit(s)
shall have a droop of 3 to 6% of MCR and hydro generating unit(s) including PSP shall have a droop of 0 to
10% of MCR.
35. The governor shall be set with respect to a reference frequency of 50.00 Hz and response outside the dead
band shall be with respect to a total change in frequency. The inherent dead band of the generating unit or
frequency controller shall not exceed (+/-) 0.03 Hz.
36. The primary response requirement shall be as mentioned in Table 1 below:
+----------------------------------------+------------------------------------------+
| Type | Response range |
+========================================+==========================================+
| Coal, Lignite & Gas based thermal | (+/-) 5% of MCR |
| generating unit | |
+----------------------------------------+------------------------------------------+
| Hydro generating unit and On-stream PSP| (+/-) 10% of MCR (subject to rated head |
| unit | being available) |
+----------------------------------------+------------------------------------------+
| Off-stream PSP unit | (+/-) 10% of MCR (subject to rated head |
| | being available) for short duration |
+----------------------------------------+------------------------------------------+
37. The generating unit shall give primary response instantaneously as per the capability upto (+/-) 5% or (+/-)
10% of their operating level/MCR, when the frequency deviates from the reference frequency:
Provided that ramping down is limited to the minimum technical level of the generating unit/station.
38. The ramp rate of the generating unit shall be as per Central Electricity Authority (Technical Standards for
Construction of Electrical Plants and Electric Lines) Regulations in force.
Reactive Power Control
39. The generating unit(s) of aggregate capacity of 100 MW and above at PoI shall have the provision to receive
the signal from the State Load Despatch Centre or Regional Load Despatch Centre, as the case may be, for
varying reactive power output.
40. The excitation system for every generating unit:
(1) shall have state of the art excitation system;
(2) shall have Automatic Voltage Regulator (AVR).
Provided that a generating unit of 100 MW rating and above shall have Automatic Voltage Regulator with
digital control and two separate channels having independent inputs and automatic changeover; and
(3) must have must have excitation control system that is capable of operating the stator continuously at 110% of
nominal voltage when operating at the MCR capacity.
41. Hydro generating unit having rated capacity of 50 MW and above shall be equipped with facility to operate
in synchronous condenser mode.
42. The Automatic Voltage Regulator of generating unit of 100 MW and above shall include Power System
Stabilizer (PSS) with the following capabilities:
(1) two washout filters for each input, with ability to bypass one of them if necessary;
(2) sufficient (and not less than two) lead-lag transfer function blocks (or equivalent number of complex poles
and zeros) with adjustable gain and time-constants, to compensate fully for the phase lags due to the
Generating Unit;
(3) monitoring and recording equipment for key variables including inputs, output and the inputs to the lead-lag
transfer function blocks;
(4) equipment to permit testing of the power system stabilizer in isolation from the power system by injection of
test signals, sufficient to establish the transfer function of the power system stabilizer;
(5) measurements of rotor speed/voltage and Active Power/reactive power output of the Generating Unit as
inputs;
(6) an output limiter, which is continually adjustable over the range of (-)10% to (+)10% of stator voltage; and
(7) sufficient flexibility to enable damping performance to be maximised, with the stabilising circuit responsive
and adjustable over a frequency range.
43. The Generating Station must have equipment capabilities and Control Systems sufficient to ensure that:
(1) power system oscillations, for the frequencies of oscillation of the Generating Station against any other
Generating Station or device, are adequately damped;
(2) operation of the Generating Station does not degrade the damping of any critical mode of oscillation of the
power system; and
(3) operation of the Generating Station does not cause instability (including hunting of Tap-Changing
Transformer Control Systems) that would adversely impact other Equipment connected to the
grid.Synchronous Condenser
44. Synchronous condenser unit shall comply with the voltage disturbance ride-through, frequency ride-through,
and multiple fault ride-through and reactive power control requirements applicable to synchronous generating
stations as specified in these regulations.
Asynchronous Generating Station
Active Power Capability
45. The generating station shall be capable of providing its ICR capacity at PoI as per the maximum and
minimum ambient temperature determined as per the procedure given in Schedule I.
Reactive Power Capability
46. The capability is to be provided in compliance with the maximum and minimum ambient temperature
determined as per the procedure given in Schedule I.
47. The generating station shall be able to provide minimum dynamic reactive power capability for all active
power levels (Including at zero) as per the PQ curve in Fig. 3. The generating station shall be capable of
absorbing or supplying dynamically varying reactive power continuously when operating anywhere inside
the PQ curve in Fig. 3
Fig. 3. Minimum Reactive power capability of generating station in terms of active power and reactive
power injection measured at PoI.
NOTE — 1) Exchange of reactive power may require the generating station to consume active power from
the grid due to losses when there is no available primary energy source.
2) The figure shows the minimum range for the reactive power capability required by this clause. The actual
capability of generating station may be higher.
3) WTG Type-III machines shall provide reactive power support as per dotted line below 0.1*ICR active
power output
PQ Curve to be followed in case of BESS during charging (absorption of active power, -P) and discharging
(injection of active power, +P) as well as in case of variable speed PSP during motoring (absorption of active
power, -P) and generating (injection of active power, +P), shall be the same as above.
48. The minimum dynamic Reactive Power Capability may be varied as shown in the QV curve when the
voltage at the PoI varies between 0.9 per unit and 1.1 per unit, where the generating station shall be capable
of absorbing or supplying Reactive Power continuously when operating anywhere inside the QV curve in
Fig.4.
Fig. 4. Minimum Reactive power capability of generating station in terms of Voltage and reactive
power measured at PoI
QV Curve to be followed in case of BESS during charging (absorption of active power, +P) and discharging
(injection of active power, -P) as well as in case of variable speed PSP during motoring (absorption of active
power, -P) and generating (injection of active power, +P), shall be the same as above:
Provided that the generating station should coordinate their LVRT and HVRT activation limits so as to
achieve the above QV curve requirements.
Voltage Disturbance Ride Through
49. The Short Circuit Ratio at the PoI where the generating station is proposed to be connected shall in general
not be less than 5. However, the generating station shall stably operate at minimum SCR of 5 or the actual
SCR at the PoI, whichever is lower.
50. The generating station shall be capable of operating continuously in the voltage range 0.9 p.u to 1.1 p.u at the
PoI and be able to deliver ICR capacity.
51. The generating station shall have configurable low and high voltage ride through activation & deactivation
settings, the range of which shall be decided based on system studies to ensure stable plant operation during
voltage ride through conditions.
52. Voltage disturbances of any duration, for which the applicable voltage remains within the continuous
operation region, shall not cause the generating station or unit(s) to trip. The generating station or unit(s)
shall remain in operation during any such disturbance, and shall continue to deliver pre-disturbance level of
active power or available active power, whichever is less.
53. All instantaneous under / over voltage protection used within the generating station shall use filtered
quantities to reduce the possibility of mis-operation while providing protection to the desired equipment and
system. Any instantaneous under /over voltage protection(s) that has the possibility of disrupting the power
output of the entire generating station shall use at least one cycle (of fundamental frequency) measurement
window to reduce such possibility and the related impact on the grid.
54. The generating station reactive current response during voltage disturbance ride through shall meet the
following performance specifications as given in Table 2 below:
+---------------------------+---------------------------------------+---------------------------------------+
| Parameter | Generating Station with Type-III WTGs | All other Asynchronous Generating |
| | | Stations |
+===========================+=======================================+=======================================+
| Step response time | NA | ≤ 30 ms |
+---------------------------+---------------------------------------+---------------------------------------+
| Settling time | ≤ 120 ms | ≤ 100 ms |
+---------------------------+---------------------------------------+---------------------------------------+
| Settling band | (-)2.5%/(+)10% of generating station | (-)2.5%/(+)10% of generating station |
| | maximum current | maximum current |
+---------------------------+---------------------------------------+---------------------------------------+
Note: 1) The time delay required for the measurements is included in the step response time and settling time
specified in this table.
3) System conditions may require a slower response time. If so, the generating station shall have the
necessary flexibility in the settings to increase the response time as per the directions of the appropriate load
despatch centre.
Low Voltage Ride Through (LVRT)
55. The generating station connected to the grid, shall remain connected to the grid for the duration
corresponding to the under voltage at the PoI on any or all phases (symmetrical or asymmetrical under
voltage conditions) as depicted by the thick line in the curve in Fig. 5
Vt : Actual Voltage; Vn: Nominal Voltage—
Fig. 5. Low Voltage Ride Through requirements for Asynchronous Generating station
Note: The relevant voltage shall be the lowest magnitude fundamental frequency phasor component of the
phase-to-phase or phase-to ground voltages, whichever is less, at the PoI relative to the corresponding
nominal voltage.
56. The generating station shall have the capability to select operation in either active current priority mode or
reactive current priority mode during low voltage ride through events. The mode during real-time operations
shall be selected as per the directions of appropriate load despatch centre. The generating station shall operate
in reactive current priority mode by default:
Provided that in the reactive current priority mode, the generating station shall provide incremental reactive
current:
Provided further that the reactive current priority mode does not necessarily mean that active power (or active
current) is reduced to zero. It means that the reactive current output (Iq) is given first priority and has the full
current rating of the generating station available to it while the active current output (Ip) is constrained. The
active current Ip range varies from a maximum of to a minimum of zero for asynchronous
generating stations and to (-) for energy storage systems, where Iq is the present value of
reactive current:
Provided also that, active power be restored to at least 90% of the pre-fault level within 1 second of
restoration of voltage. The active power recovery time shall be adjustable within a configurable range of 1.0
to 10 seconds.
57. During LVRT condition, the generating station shall have the overload (current) capability of minimum
1.1pu of the rated capacity and the reactive/active current shall be supplied considering apparent current
rating of 1.1pu.
58. The step response time for LVRT conditions shall be maximum 30 ms i.e. the generating station shall be
capable of injecting the incremental reactive current within 30 ms into the network. The injection of the
incremental reactive current shall also be withdrawn within 30 ms of the return of the voltage within the
continuous operating range. The response of the generating station shall be adequately damped.
59. For balanced faults and symmetrical over-voltage conditions, the generating station shall provide incremental
positive sequence reactive current support dependent on the PoI voltage:
Provided that the quantum of positive sequence reactive current injection shall be dependent on the reactive
current gain i.e. LVRT “K+” factor, value of which shall be decided through simulation studies by the
appropriate transmission utility and appropriate LDC based on the system strength and network stability in
the complex. The LVRT “K+” factor shall typically be in the range of 0 to 10.
60. For unbalanced faults and unsymmetrical over-voltage conditions, in addition to the incremental positive
sequence reactive current, the generating station shall inject negative sequence current dependent on PoI
negative sequence voltage:
Provided that the quantum of negative sequence reactive current injection shall be dependent on the reactive
current gain i.e. LVRT “K-” factor, value of which shall be decided through simulation studies by the
appropriate transmission utility and load despatch centre based on the system strength and network stability
in the complex. The LVRT “K-” factor shall typically be in the range of 0 to 10:
Provided further that incremental negative sequence current from generating stations with Type-III WTG
may not be completely controllable and shall be governed as per machine dynamics & converter control.
61. In the event the generating Station apparent current limit of 1.1pu is reached, either positive or negative
sequence current shall be reduced with a preference to be given to equal reduction of both currents.
High Voltage Ride Through (HVRT)
62. The generating station connected to the grid, shall remain connected to the grid for the duration
corresponding to the overvoltage at the PoI, on any or all phases (symmetrical or asymmetrical overvoltage
conditions) as depicted by the thick line in the curve in Fig 6:
Fig. 6. High Voltage ride-through requirements for asynchronous generating station.
Note: The relevant voltage shall be the greatest magnitude fundamental frequency phasor component of the
phase-to-phase and phase-to ground voltages, whichever is high, at the PoI relative to the corresponding
nominal voltage.
63. The generating station shall have the capability to select operation in either active current priority mode or
reactive current priority mode during high voltage ride through events. The mode during real-time operations
shall be selected as per the directions of appropriate load despatch centre. The generating station shall operate
in reactive current priority mode by default:
Provided that, in the reactive current priority mode, the generating station shall provide incremental reactive
current:
Provided further that the reactive current priority mode does not necessarily mean that active power (or active
current) is reduced to zero. It means that the reactive current output (Iq) is given first priority and has the full
current rating of the generating station available to it while the active current output (Ip) is constrained. The
active current Ip range varies from a maximum of to a minimum of zero for asynchronous
generating stations and to (-) for energy storage systems, where Iq is the present value of
reactive current:
Provided also that, active power be restored to at least 90% of the pre-fault level within 1 second of
restoration of voltage. The active power recovery time shall be adjustable within a configurable range of 1.0
to 10 seconds.
64. During HVRT condition, the generating station shall have the overload (current) capability of minimum
1.1pu of the rated capacity and the reactive/active current shall be supplied considering apparent current
rating of 1.1pu.
65. The step response time for HVRT conditions shall be maximum 30 ms i.e. the generating station shall be
capable of absorbing the incremental reactive current within 30 ms from the network. The absorption of the
incremental reactive current shall also be withdrawn within 30 ms of the return of the voltage within the
continuous operating range. The response of the generating station shall be adequately damped.
66. For balanced faults and symmetrical over-voltage conditions, the generating station shall provide incremental
positive sequence reactive current support dependent on the PoI voltage:
Provided that the quantum of positive sequence reactive current absorption shall be dependent on the reactive
current gain i.e. HVRT “K+” factor, value of which shall be decided through simulation studies by the
appropriate transmission utility and appropriate Load Despatch Centre based on the system strength and
network stability in the complex. The HVRT “K+” factor shall typically be in the range of 0 to 10.
67. For unbalanced faults and unsymmetrical over-voltage conditions, in addition to the incremental positive
sequence reactive current, the generating station shall absorb negative sequence current dependent on PoI
negative sequence voltage:
Provided that the quantum of negative sequence reactive current absorption shall be dependent on the
reactive current gain i.e. HVRT “K-” factor, value of which shall be decided through simulation studies by
the appropriate transmission utility and load despatch centre based on the system strength and network
stability in the complex. The HVRT “K-” factor shall typically be in the range of 0 to 10:
Provided further that incremental negative sequence current from generating stations with Type-III WTG
may not be completely controllable and shall be governed as per machine dynamics & converter control.
68. In the event the generating Station apparent current limit of 1.1pu is reached, either positive or negative
sequence current shall be reduced with a preference to be given to equal reduction of both currents.
Multiple Fault Ride Through
69. The generating station connected to the grid, shall remain connected to the grid for a series of up to 15
voltage disturbance below 0.9 p.u within any 5-minute period as per the LVRT capability:
Provided that during such period generating station shall remain connected for at least 06 voltage disturbance
below 0.5 p.u:
Provided further that during the multiple LVRT conditions, the generating station shall meet the performance
requirements specified in LVRT conditions.
70. While assessing multiple voltage disturbances, a fault that is re-established following operation of automatic
re-close Protection Scheme shall be counted as a separate voltage disturbance.
Frequency Ride Through
71. The generating station shall be capable of operating in the frequency range 47.5 to 52 Hz and be able to
deliver its ICR capacity in the frequency range of 49.5 Hz to 50.5 Hz on a continuous basis:
Provided that the generating station shall be able to maintain its performance contained in this sub-clause
even with voltage variation of up to (+/-) 5% subject to availability of commensurate primary energy
source.
72. Within the specified frequency range of operation, the generating station shall ride through and shall not trip
for frequency excursions having an absolute rate of change of frequency (ROCOF) magnitude that is less than or
equal to 5.0 Hz/second. ROCOF shall be the average rate of change of frequency over an averaging window
of at least 0.1 second.
73. The rate of change of frequency (ROCOF) protection shall not impede the generating station from meeting
the voltage and frequency ride-through requirements specified in these regulations inclusive of ROCOF ride
through requirements.
Voltage Phase Angle Change Ride Through
74. The generating unit shall ride through positive-sequence phase angle changes within a sub-cycle-to-cycle
time frame of the applicable voltage of less than or equal to (+/-) 25 electrical degrees. In addition, the
generating unit shall remain in operation for any change in the phase angle of individual phases caused by
occurrence and clearance of unbalanced faults, provided that the positive-sequence angle change does not
exceed the forestated criterion.
Active Power Control
75. The generating station with installed capacity of more than 10 MW connected at voltage level of 33 kV and
above:
(1) shall be equipped with the facility to control active power injection in accordance with a set point, capable
of being revised based on directions of the State Load Despatch Centre or Regional Load Despatch Centre,
as the case may be;
(2) The frequency controller shall be set with respect to a reference frequency of 50.00 Hz and the response
outside the dead band shall be with respect to a total change in frequency.
(3) shall have frequency controller with a settable droop of 1 to 6% of ICR. The inherent dead band of the of the
frequency shall not exceed (+/-) 0.03 Hz:
Provided that for frequency deviations in excess of 0.3 Hz, the Generating Station shall have the facility to
provide an immediate (within 1 second) real power primary frequency response of at least 10% of the
maximum Alternating Current active power capacity.
(4) shall have the operating range of the frequency response and regulation system from 10% to 100% of the
maximum Alternating Current active power capacity, corresponding to solar insolation or wind speed, as the
case may be;
(5) shall be equipped with the facility for controlling the rate of change of power output at a ramp rate not more
than ± 10% per minute at PoI.
76. The primary response requirement shall be as mentioned in Table 3 below:
+------------------------------------------+----------------+
| Type | Response range |
+==========================================+================+
| Solar, Wind and Battery Energy Storage | (+/-) 10% of |
| System (BESS) | ICR |
+------------------------------------------+----------------+
77. The generating unit shall give primary response instantaneously as per the capability upto (+/-) 10% of their
operating level/ICR, when the frequency deviates from the reference frequency.
78. The overall dynamic primary frequency response capability of the generating station for a step change in
applicable frequency shall be within the ranges specified in Schedule II.
Reactive Power Control
79. The generating station of aggregate capacity of 10 MW and above shall have the provision to receive the
signal from the State Load Despatch Centre or Regional Load Despatch Centre, as the case may be, for
varying reactive power output.
80. The generating station shall provide voltage regulation capability by changes in reactive power output
whenever the PoI voltage is in the continuous operation region for voltage.
81. The generating station shall provide the capabilities of the following mutually exclusive operating modes of
reactive power control functions:
(1) Voltage control
(2) Power factor control
(3) Reactive power set point control
The generating station shall be capable of activating each of these modes one at a time. The generating
station shall be responsible for implementing setting modifications and mode selections, as specified by the
appropriate system operator within a time acceptable to the appropriate system operator.
The dynamic response of the generating station in all the control modes shall be stable and any oscillations
shall be positively damped.
Black Start Capability
82. BESS of aggregate capacity of 50 MW and above shall be capable of providing Black Start support. This
capability shall be utilized by appropriate load despatch centre based on system requirements.
83. The black start functionality shall be demonstrated during commissioning and verified periodically through
testing in accordance with these standards and other requirements as specified by the appropriate Load
Despatch Centre.
Grid Forming Control
84. The generating station with Grid Forming control shall comply with all regulations applicable to
asynchronous generating station.
85. The generating station with Grid Forming control shall independently provide near-instantaneous frequency
and voltage support. The primary control objective shall be to maintain the voltage phasor of the internal
voltage source, established through control strategies, as constant during the sub-transient time frame,
utilizing the converter’s full available current capacity.
86. The generating station with Grid Forming converters shall be capable of seamless transition to and from
islanded operation, ensuring stable reconnection to the main grid.
87. The generating station with Grid Forming control shall also be capable of injecting negative-sequence
currents for the purpose of maintaining voltage symmetry under unbalanced conditions, both during steady
state and fault conditions.
88. The generating station with Grid Forming control shall be capable of riding through positive-sequence phase
angle variations of up to ±60 electrical degrees within a sub-cycle to one-cycle timeframe, relative to the
applicable voltage.
Energy Storage System (ESS)
89. The requirements applicable to ESS are as specified in Table 4 below:
+-------------------+--------------------+
| Fixed Speed PSP | Regulation 21 to 44|
+-------------------+--------------------+
| BESS | Regulation 45 to 88|
+-------------------+--------------------+
| Variable Speed PSP| Regulation 21 to |
| | 23, 32 to 44, 49 to|
| | 55 and 62 |
+-------------------+--------------------+
CHAPTER – III
REQUIREMENTS FOR HVDC SYSTEMS AND FACTS (FLEXIBLE AC TRANSMISSION SYSTEM)
DEVICES
General Requirements
90. The HVDC system and FACTS devices shall be designed to meet all performance requirements specified in
these regulations and shall be compatible with the existing power system.
91. HVDC links can either be used to connect asynchronous grids with each other or can be embedded within a
single synchronous AC grid.
92. The HVDC system shall be capable of finding stable operation points with a minimum change in active
power flow and voltage level, during and after any planned or unplanned change in the HVDC system or AC
network to which it is connected.
93. The HVDC system owner shall ensure that the tripping or disconnection of an HVDC converter station, as
part of any multi-terminal or embedded HVDC system, does not result in transients at the PoI.
94. The HVDC system and FACTS devices shall withstand transient faults on HVAC lines in the network
adjacent or close to the HVDC system, and shall not cause any of the equipment in the HVDC system to
disconnect from the network due to auto-reclosure of lines in the network.
95. HVDC systems, including DC overhead lines, shall be capable of fast recovery from transient faults within
the HVDC system.
96. The appropriate transmission utility and distribution licensee shall specify and make available the method
and the pre-fault and post-fault conditions for the calculation of the minimum and maximum short circuit
power at the PoI. The ratio of fault level in MVA at any of the convertor station (for conventional current
source type), to the power flow on the LCC based HVDC bipole shall not be less than 3.0.
97. The HVDC system and FACTS shall be capable of operating within the range of short circuit power and
network characteristics specified by the appropriate transmission utility and distribution licensee.
98. The appropriate transmission utility and distribution licensee shall provide the network equivalents
describing the behavior of the network at the PoI, enabling the requester/user to design their system with
regard to at least, but not limited to, harmonics and dynamic stability over the lifetime of the HVDC system
and FACTS device.
99. The requester/user shall maintain a complete HVDC system and FACTS Devices control and protection
replica system without redundancy along with a real time simulator based on project specification at its
premises.
100. HVDC System and FACTS devices should have the feature of active filtering to manage the background
harmonics. The order and magnitude of harmonics to be attenuated at PoI may be decided by appropriate
transmission utility.
101. Performance of HVDC and FACTS devices shall be tested by a third-party accredited testing agency before
getting connected to the Grid.
102. System studies for evaluating dynamic performance testing of HVDC and FACTS devices during EMT
modelling stage and Real time Simulation shall be carried out considering at least two network cases i.e Peak
and Off-peak.
103. System studies for interaction between nearby HVDC systems, FACTs devices, Generating Stations
(Asynchronous and synchronous) and Conventional AC equipment should be carried out in line with CIGRE
Technical Brochure (TB-934) (Interaction between nearby VSC-HVDC converters, FACTs devices, HV
power electronic devices and conventional AC equipment).
Reactive Power Capability
104. The VSC based HVDC system (at both converter ends) shall be capable of supplying and absorbing
dynamically varying reactive power at the PoI commensurate to 32.87% (0.95pf lagging/leading) of rated power capacity of the
HVDC system. The capability is to be provided in compliance with the maximum and minimum ambient
temperature determined as per the procedure given in Schedule I.
105. The VSC HVDC system shall be able to provide minimum dynamic reactive power capability for all active
power levels (including at zero) as per the PQ curve in Fig.7. The VSC HVDC system shall be capable of
absorbing or supplying dynamically varying reactive power continuously when operating anywhere inside the
PQ curve in Fig. 7:
Fig. 7. Minimum Reactive power capability of HVDC system in terms of active power and reactive
power measured at PoI.
NOTE — 1) Exchange of reactive power may require the VSC HVDC system to consume active power from
the grid due to losses when there is no transfer of active power.
3) The figure shows the minimum range for the reactive power capability required by this clause. The VSC
HVDC system actual capability may be higher.
Provided that the PQ curve to be followed during charging (absorption of active power, -P) and discharging
(injection of active power, +P) shall be the same as above.
106. The minimum dynamic Reactive Power Capability may be varied as shown in the QV curve when the
voltage at the PoI varies between 0.9 per unit and 1.1 per unit, where the VSC HVDC system shall be
capable of absorbing or supplying Reactive Power continuously when operating anywhere inside the QV
curve in Fig. 8:
Fig. 8. Minimum Reactive power capability of VSC HVDC system in terms of Voltage and reactive
power measured at PoI.
Provided that the QV Curve to be followed during charging (absorption of active power, -P) and discharging
(injection of active power, +P) shall be the same as above.
Voltage Disturbance Ride through
107. The HVDC system and FACTS devices shall operate continuously in the AC voltage range 0.9 p.u to 1.1 p.u
at the PoI and be able to deliver rated output.
108. The HVDC station and FACTS devices shall have configurable low and high voltage ride through activation
& deactivation settings, the range of which shall be decided based on system studies to ensure stable plant
operation during voltage ride through conditions.
109. All instantaneous under / over voltage protection used within the HVDC system and FACTS device shall use
filtered quantities to reduce the possibility of mal-operation while providing protection to the desired
equipment and system. Any instantaneous under /over voltage protection(s) which have the possibility of
disrupting the power output of the entire HVDC system shall use at least one cycle (of fundamental
frequency) measurement window to reduce such possibility and the related impact on the grid.
110. The VSC HVDC system and FACTS device reactive current response shall meet the following performance
specifications as given in Table 5 below:
+-------------------+---------------------------------------------+
| Parameter | VSC HVDC System and FACTS |
+===================+=============================================+
| Step response time| ≤ 30 ms |
+-------------------+---------------------------------------------+
| Settling time | ≤ 100 ms |
+-------------------+---------------------------------------------+
| Settling band | (-)2.5%/(+)10% of HVDC System and FACTS |
| | maximum current |
+-------------------+---------------------------------------------+
Note: 1) The time delay required for the measurements is included in the step response time and settling time
specified in this Table.
(c) System conditions may require a slower response time. If so, the HVDC System and FACTS shall
have the necessary flexibility in the settings to increase the response time as per the directions of the
appropriate load despatch centre.
Low Voltage Ride Through (LVRT)
111. The VSC HVDC System and FACTS Devices connected to the grid, shall remain connected to the grid for
the duration corresponding to the under voltage at the PoI on any or all phases (symmetrical or asymmetrical
under voltage conditions) as depicted by the thick line in the curve in Fig. 9
Vt : Actual Voltage; Vn: Nominal Voltage—
Fig. 9. Low Voltage Ride Through requirements for VSC HVDC system and FACTS devices
Note: The relevant voltage shall be the lowest magnitude fundamental frequency phasor component of the
phase-to-phase or phase-to ground voltages, whichever is less, at the PoI relative to the corresponding
nominal voltage.
High Voltage Ride Through (HVRT)
112. The VSC HVDC System and FACTS Devices connected to the grid, shall remain connected to the grid for
the duration corresponding to the overvoltage at the PoI, on any or all phases (symmetrical or asymmetrical
overvoltage conditions) as depicted by the thick line in the curve in Fig 10:
Fig. 10: High Voltage ride-through requirements for VSC HVDC system and FACTS devices.
Note: The relevant voltage shall be the greatest magnitude fundamental frequency phasor component of the
phase-to-phase and phase-to ground voltages, whichever is high, at the PoI relative to the corresponding
nominal voltage.
Multiple Fault Ride Through (MFRT)
113. The HVDC System and FACTS devices connected to the grid, shall remain connected to the grid for a series
of up to 15 voltage disturbance below 0.9 p.u within any 5-minute period as per the LVRT capability:
Provided that during such period HVDC System and FACTS devices shall remain connected for at least 06
voltage disturbance below 0.5 p.u:
Provided further that during the multiple LVRT conditions, the HVDC System and FACTS devices shall
meet the performance requirements specified in LVRT conditions.
114. While assessing multiple voltage disturbances, a fault that is re-established following operation of automatic
re-close Protection Scheme shall be counted as a separate voltage disturbance.
Frequency Ride through
115. HVDC system and FACTS shall be capable of operating in the frequency range 47.5 to 52.5 Hz and be able
to deliver rated output in the frequency range of 48.5 Hz to 51 Hz:
Provided that the HVDC system and FACTS shall be able to maintain its performance contained in this sub
clause even with voltage variation of up to (+/-) 5%.
116. Within the frequency range of operation specified, the HVDC system and FACTS devices shall ride through
and shall not trip for frequency excursions having an absolute rate of change of frequency (ROCOF)
magnitude that is less than or equal to 5.0 Hz/second. ROCOF shall be the average rate of change of frequency over
an averaging window of at least 0.1 second:
Provided that during black start operation using HVDC, the ROCOF withstand capability may be higher.
117. The rate of change of frequency (ROCOF) protection shall not impede the HVDC system and FACTS
devices from meeting the voltage and frequency ride-through requirements specified in these regulations
inclusive of ROCOF ride-through requirements.
Voltage Phase Angle Change Ride Through
118. The VSC HVDC system and FACTS shall ride through positive-sequence phase angle changes within a sub
cycle-to-cycle time frame of the applicable voltage of less than or equal to (+/-) 25 electrical degrees. In
addition, it shall remain in operation for any change in the phase angle of individual phases caused by
occurrence and clearance of unbalanced faults, provided that the positive-sequence angle change does not
exceed the forestated criterion.
Active Power Control
119. The VSC HVDC system shall be capable of adjusting the transmitted active power up to its maximum
HVDC active power transmission capacity in each direction following an instruction from the appropriate
load despatch centre. The minimum step size for change in power shall be 1% of the maximum rated power.
120. The power reversal in LCC based HVDC links shall be possible from the maximum active power
transmission capacity in one direction to the maximum active power transmission capacity in the other
direction within 60 minutes. For LCC based HVDC Back-to-back stations, this duration shall be 30 minutes.
The VSC HVDC shall be designed for minimum 02 reversal operations per day. VSC based HVDC System
shall have the capability to transfer the maximum active power transmission capacity in one direction to the
maximum active power transmission capacity in the other direction on immediate basis.
121. The HVDC system shall be capable of adjusting the ramping rate of active power variations by at least 10%
per minute of active power order in upwards/downwards direction under all conditions.
122. The continuous and transient overload capability per pole shall be specified in the technical specifications.
123. The HVDC system designed for locations where low inertia/islanding situations are possible shall be capable
of providing synthetic inertia in response to frequency changes, activated in low or high-frequency conditions
by rapidly adjusting the active power to limit the rate of change of frequency.
124. The HVDC system shall be equipped with an independent control mode to modulate the active power output
of the HVDC converter station depending on the frequencies at all connection points of the HVDC system to
maintain stable system frequencies. The settings of frequency control shall be returnable to be changed on
recommendation of appropriate load despatch centre.
Reactive Power Control
125. The VSC HVDC system and FACTS devices shall provide voltage regulation capability by changes in
reactive power output whenever the PoI voltage is in the range for continuous operation.
126. The VSC HVDC system and FACTS devices shall provide the capabilities of the following mutually
exclusive operating modes of reactive power control functions:
(1) Voltage control
(2) Reactive power set point control
The VSC HVDC system and FACTS devices shall be capable of activating each of these modes one at a
time. The VSC HVDC system and FACTS devices shall be responsible for implementing setting
modifications and mode selections, as specified by the appropriate system operator within a time acceptable
to the appropriate system operator.
The dynamic response of the VSC HVDC system and FACTS devices in all the control modes shall be stable
and any oscillations shall be positively damped.
127. VSC HVDC system and FACTS devices shall be capable of operating in additional control modes as
specified by the appropriate transmissions utility and load despatch centre.
Power Oscillation Damping
128. HVDC and FACTS devices shall implement a power oscillation damping (POD) function in their controls,
which can be tuned to reduce the power system oscillations.
129. The HVDC system shall be capable of contributing to electrical damping of torsional frequencies with regard
to sub synchronous torsional interaction (SSTI) damping control. The appropriate transmission utility shall
provide input parameters, to the extent available, related to the equipment and relevant system conditions in
its network. The SSTI studies shall be carried out by the requester/user.
Black Start Capability
130. The Black start capability shall be possible for both the converter stations of the VSC HVDC system.
Transmission Service Provider (TSP) shall determine and provide any additional equipment that is required
to be able to carry out black start in both directions. This shall include any hardware and all the necessary
control functions to perform the black start.
CHAPTER – IV
REQUIREMENTS FOR BULK CONSUMERS AND DISTRIBUTION SYSTEMS
General Requirements
131. The bulk consumer(s) shall not energize transmission or distribution system by injecting supply from his
generators or any other source either by automatic controls or manually unless specifically provided for in the
connection agreement with the Transmission or Distribution Licensee.
132. The Short Circuit Ratio at the PoI where the Inverter-interfaced bulk consumer is proposed to be connected
shall in general be not less than 5. The Inverter-interfaced bulk consumer shall stably operate at minimum
SCR of 5 or the actual SCR at the PoI, whichever is lower.
133. The Voltage-disturbance ride-through, frequency ride through and Voltage Phase-angle ride through
requirements shall be applicable to Inverter-interfaced bulk consumers having capacity of 50 MW or above at
PoI.
Reactive Power Capability
134. The inverter-interfaced bulk consumers shall be capable of supplying and absorbing dynamically varying
reactive power at the PoI commensurate to 32.87% (0.95pf lagging/leading) of rated power capacity of
inverter-interfaced bulk consumers. The capability is to be provided in compliance with the maximum and
minimum ambient temperature determined as per the procedure given in Schedule I.
135. The inverter-interfaced bulk consumers shall be able to provide minimum dynamic reactive power capability
for all active power levels (including at zero power being drawn by the inverter-interfaced bulk consumers)
as per the shown PQ curve in Fig. 11. The inverter-interfaced bulk consumers must be capable of absorbingor
supplying Reactive Power continuously when operating anywhere inside the PQ curve in Fig. 11.
Fig. 11. Minimum Reactive power capability of inverter-interfaced bulk consumer in terms of active
power and reactive power drawal measured at PoI.
NOTE – 1) Exchange of reactive power may require the inverter-interfaced bulk consumers to consume
active power from the grid due to losses.
2) The figure shows the minimum range for the reactive power capability required by this standard. The
inverter-interfaced bulk consumers' actual capability may be higher.
136. The minimum dynamic Reactive Power Capability of the inverter-interfaced bulk consumer may be varied as
shown in the QV curve in Fig. 12. when the voltage at the PoI varies between 0.9 per unit and 1.1 per unit,
where the inverter-interfaced bulk consumer must be capable of absorbing or supplying Reactive Power
continuously when operating anywhere inside the QV curve.
Fig. 12. Minimum Reactive power capability of inverter-interfaced bulk consumer in terms of voltage
and reactive power measured at PoI.
137. The distribution licensee shall provide adequate reactive compensation to meet the reactive power
requirement in their system so that power factor is maintained within ± 0.95.
138. The bulk consumer other than inverter-interfaced bulk consumer shall provide adequate reactive
compensation in their system so as maintain unity power factor at PoI:
Provided that the bulk consumer other than inverter-interfaced bulk consumer shall have the capability to
maintain power factor in the range of ± 0.95 as per the directions of appropriate load despatch centre.
Voltage Disturbance Ride Through
139. The inverter-interfaced bulk consumers shall be capable of operating continuously in the voltage range 0.9
p.u to 1.1 p.u at the PoI and be able to draw rated power.
140. The inverter-interfaced bulk consumer shall have configurable low and high voltage ride through activation
& deactivation settings, the range of which shall be decided based on system studies to ensure stable plant
operation during voltage ride through conditions.
141. All instantaneous under / over voltage protection used within the inverter-interfaced bulk consumer shall use
filtered quantities to reduce the possibility of mal-operation while providing protection to the desired
equipment and system. Any instantaneous under /over voltage protection(s) which has the possibility of
disrupting the power drawl of the entire inverter-interfaced bulk consumer shall use at least one cycle (of
fundamental frequency) measurement window to reduce such possibility and the related impact on the grid.
142. The inverter-interfaced bulk consumer’s current response shall meet the following performance
specifications as given in Table 6 below:
+-------------------+---------------------------------------------+
| Parameter | Inverter-interfaced bulk consumers |
+===================+=============================================+
| Step response time| ≤ 30 ms |
+-------------------+---------------------------------------------+
| Settling time | ≤ 100 ms |
+-------------------+---------------------------------------------+
| Settling band | (-)2.5%/(+)10% of inverter-interfaced bulk |
| | consumer’s maximum current |
+-------------------+---------------------------------------------+
Note: 1) The time delay required for the measurements is included in the step response time and
settling time specified in this table.
2) System conditions may require a slower response time. If so, the inverter-interfaced bulk
consumer shall have the necessary flexibility in the settings to increase the response time as per
the directions of the appropriate load despatch centre.
Low Voltage Ride Through (LVRT)
143. The inverter-interfaced bulk consumer connected to the grid, shall remain connected to the grid for the
duration corresponding to the under voltage at the PoI on any or all phases (symmetrical or asymmetrical
under voltage conditions) as depicted by the thick line in the curve in Fig. 13
Vt: Actual Voltage; Vn: Nominal Voltage—
Fig. 13. Low Voltage Ride Through requirements for inverter-interfaced bulk consumer
Note: The relevant voltage shall be the lowest magnitude fundamental frequency phasor component of the
phase-to-phase or phase-to ground voltages, whichever is less, at the PoI relative to the corresponding
nominal voltage.
144. The inverter-interfaced bulk consumer shall have the capability to select operation in either active current
priority mode or reactive current priority mode during low voltage ride through events. The mode during
real-time operations shall be selected as per the directions of appropriate load despatch centre. The inverter
interfaced bulk consumer shall operate in reactive current priority mode by default:
Provided that, in the reactive current priority mode, the inverter-interfaced bulk consumer shall deliver
incremental reactive current:
Provided further that the reactive current priority mode does not necessarily mean that active power (or active
current) is reduced to zero. It means that the reactive current output (Iq) is given first priority and has the full
current rating of the inverter-interfaced bulk consumer available to it while the active current output (Ip) is
constrained. The active current Ip range varies from zero to (-) for inverter-interfaced bulk
consumer, where Iq is the present value of reactive current:
Provided also that, active power be restored to at least 90% of the pre-fault level within 1 second of
restoration of voltage. The active power recovery time shall be adjustable within a configurable range of 1.0
to 10 seconds.
145. During LVRT condition, the inverter-interfaced bulk consumer shall have the overload (current) capability of
minimum 1.1pu of the rated capacity and the reactive current shall be supplied considering apparent current
rating of 1.1pu.
146. The step response time for LVRT conditions shall be maximum 30 ms i.e. the inverter-interfaced bulk
consumer shall be capable of injecting the incremental reactive current within 30 ms into the network. The
injection of the incremental reactive current shall also be withdrawn within 30 ms of the return of the voltage
within the continuous operating range. The response of the inverter-interfaced bulk consumer shall be
adequately damped.
147. For balanced faults and symmetrical over-voltage conditions, the inverter-interfaced bulk consumer shall
provide incremental positive sequence reactive current support dependent on the PoI voltage:
Provided that the quantum of positive sequence reactive current injection shall be dependent on the reactive
current gain i.e. LVRT “K+” factor, value of which shall be decided through simulation studies by the
appropriate transmission utility and appropriate Load Despatch Centre based on the system strength and
network stability in the complex. The LVRT “K+” factor shall typically be in the range of 0 to 10.
148. For unbalanced faults and unsymmetrical over-voltage conditions, in addition to the incremental positive
sequence reactive current, the inverter-interfaced bulk consumer shall inject negative sequence current
dependent on PoI negative sequence voltage:
Provided that the quantum of negative sequence reactive current injection shall be dependent on the reactive
current gain i.e. LVRT “K-” factor, value of
Login to read full text