Grid Standard

8/12/2019 Grid Standard

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Grid Connec t iv i ty Standards,Gr id standards

alka

NPTI, PSTI

Bangalore


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CEAs Standards for

Grid Connectvity


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1.Transmission system Planning & Design

i. The transmission licensee shall plan and design the

inter state/ intra state transmission system based on thefollowing

a. CEA Manual on Transmission Planning Criteria: 1994

b. CEA Report of the Committee for Updating the Best Practices

in Transmission System for the Country: 2002.

c. Latest Issue of CBIP Manuals on: Layout of Substations,

Transmission Towers

d. Grid code

e. State Grid code


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1.Transmission system Planning & Design

ii. The integrity of the regional grid is not affected under various

operating conditions including stipulated system contingenciesa. all elements of the transmission system shall be designed

taking into account the specifiedfactors of safetyin regard to

electrical, mechanical and civil aspects in the respective

standardsb. optimal system to be chosen after performing load flow, short

circuit, stability studiesof the various transmission alternative

The system designed shall not impinge on the rating of thesubstation equipment in any other sub station in the vicinity.


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2. Overhead Transmission Lines

i. The transmission line proposed to be connected shall be

comply with the followinga. Tower design shall be based on the technical standards for the

construction of electrical lines specified by the authority under

section 73(b) of the Act

b. Foundation design for the tower to be developed by thetransmission licensee for various soil categories.

c. Use of multi circuit and narrow based towers wherever ROW

constraints exist

d. Each type of tower to be type tested for mechanical strength

ii. Clearance from PTCC shall be obtained


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3. EHV/HV Underground Cables

i. Cables proposed to be connected to the system, shall comply with the

following

a. Shall be ofXLPE typecorresponding to IS 7098

b. Cable conductor to be of adequate sizeconsidering continuous current,

short circuit current, voltage drop etc, & shall correspond to IS-8130

c. Cables to be provided with propersheathing, armoring & screening

d. Prior permission from appropriate authority to be obtained for diggingtrenches, precautions to be taken

e. Route maps to be kept at Substation & markers shall be fixed to trace the

cables

f. Road crossing to be carried out by providing Hume pipes or GI pipes

g. Jointing & termination to be carried out as per relevant standards

ii. Clearance from PTCC shall be obtained


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4. Substations

Planning and design of substations to be based on the following

Security of supply, extendibilty, maintainabilty andoperational flexibility

Statutory safety requirements

Protection from direct lightening stroke

Switching scheme:-

765 kV Substation: Double bus double breaker

400 kV Substation: One and half breaker scheme/ double main

and transfer bus bar scheme

220 kV Substation: Double main and transfer scheme/ double

main with breaker by-pass scheme

132kV Substation: Main and transfer scheme

below 132 kV Substation: as decided by licensee


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4. Substations


v. All EHV circuit breakers to be of SF6 typevi. Isolators to be pneumatic or motor operated

vii. ICTs to be provided with OLTCs

viii. Surge arrestors to be of metal oxide type (as per IEC 60099)

ix. Control room to be extensible

x. All substation structures to be of lattice steel. Structures to

conform to IEC 865, IS-875, IS-802, IS-800

xi. Electrical, mechanical and civil designs to be standardised to

the extent possible


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4. Substations


xii. Power Supply to the sub station auxillariesa. AC Supply;

2 HT supplies shall be arranged from independent sources.

In addition, a DG set of suitable capacity to be provided

b. DC Supply:

2 sets of 220 V batteries each equipped with own charger for

substations of 220 kV & above. 2 sets of 50 V batteries for

PLCC system.

for substations of 132 kV & below, 1 set of battery each tobe provided

xii. For high current, XLPE cables to be employed. For LV/MV

systems, PVC cables corresponding to IS-1554, can be

employed


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4. Substations


xiv. Reliable communication link shall be provided on all EHTlines for voice, Fax, protection, telemetry & SCADA

xv. Substation grounding shall be done in accordance with IEEE-80

xvi. Size and no. of ICTs to be selected such that outage of one

shouldnt overload the remaining ICTs or the underlyingsystem

xvii. The stuck breaker condition in the substation shall not causedisruption of more than 4 feeders in 132 or 220 kV system,

more than 2 feeders in 400 kV system and more than onefeeder in 765 kV system

xviii. In substations of 220 kV and above, control room, PLCCroom, Relay testing room and electronic laboratory shall be airconditioned


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5. Earth Fault Factor

In the event of a point in the EHT system of a transmission licensee

being earthed, the Earth fault Factor shall be less than 1.4

6. Electromagnetic CompatibilityA line or equipment in the transmission system shall not generate

excessive electromagnetic field and the RIV (radio

interference voltage) shall be within permissible limits as per

relevant standards


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7. Insulation coordination

i. For new connections, the CTU/ STU/ transmission licensee,

shall inform the transmission users seeking connectivity, theBIL and important parameters of the equipment and ratings of

the surge arresters in its system adjacent to the connection

point.

ii. The transmission users and licensees seeking connectivity

shall furnish to the CTU/ STU, the BIL of the proposed

system/ important items of the equipment and the rating of the

surge arresters adjacent to the connection point

iii. The CTU/ STU/ transmission licensee shall determine the

ratings of the surge arresters to be installed at the connection

point

iv. Requisite insulation coordination to be done by the CTU/

STU/ transmission licensee.


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8. Grid standards

The transmission utility, transmission licensee and the load dispatch

center shall comply with the CEAs Grid standards


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Grid Standards


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1. Short title and commencement and application

These are CEA (Grid standards) Regulations, 2010These regulations came into force on their publication in

official gazette i.e.June 26, 2010

These shall apply to the entities, appropriate LDCs, and RPCs.

2. DefinitionsBulk consumermeans a consumer who avails supply at

voltages of 33 kV or above

Entity - means a Generating company or a transmission licenseeor a distribution licensee or a bulk consumer

Voltage UnbalanceRatio of the maximum voltage deviation of

the phase voltage from the average phase voltage to the average

phase voltage


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3. Standards for operation and

maintenance of transmission lines

All entities

LDCs

RPCs

a) Frequency ControlOperating Range : 49.5 to 50.2 Hz or as per grid

code, except during the transient periodfollowing tripping.


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b) Operating Voltage Limits

S.No. Normal system

Voltage (kV rms)

Maximum (kV

rms)

Minimum (kV

rms)

1 765 800 728

2 400 420 380

3 220 245 198

4 132 145 122

5 110 121 99

6 66 72 60

7 33 36 30


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c) Temporary over voltage range d) voltage unbalance limits

S.No. Nominal System

Voltage (kV rms)

Temporary over voltage

Phase to Neutral (kV peak)

Voltage

unbalance (%)

1 765 914 1.5

2 400 514 1.5

3 220 283 24 132 170 3

5 33 Decided by the state

commission in the respective

State grid code

3


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e) Max fault clearance time

S.No. Normal system Voltage

(kV rms)

Maximum time

in milliseconds

1 765 and 400 100

2 220 and 132 160

Time delay for Back up breaker operation 200 ms.


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f) Grid shall with stand one of the following

contingencies without loss of stability

Outage of one single largest generating unit

Outage of a 132 kV double circuit line

Outage of a 220 kV double circuit line

Outage of a 400 kV single circuit line

Outage of a 400 kV single circuit line with seriescompensation

Outage of a 765 kV single circuit line without series

compensation Outage of one pole of HVDC Bipolar line

Outage of one interconnecting transformer


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g) N-1 criteria for system stability- system shall

be stable for one of the following contingencies

Tripping of single largest generating unit

Transient SLG fault of a 765 kV line close to bus

A SLG Fault on 400 kV line and isolation of the line

A fault on one circuit of a 400 kV double circuit line in

operation

A transient SLG fault in one of the 400 kV double circuit

line when the second circuit is already under outage

A 3 ph fault in 220 kV or 132 kV line

A fault in one pole of HVDC bipolar in a HVDC

Converter station


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h) Limits for harmonic distortion in

Transmission systems

S.No. System Voltage (kV rms) Total harmonic

distortion (%)

Individual

Harmonic of any

particular

frequency (%)

1 765 1.5 1.0

2 400 2.0 1.5

3 220 2.5 2.0

4 33 to 132 5.0 3.0


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4. Operations planning

Regional Power Committee shall periodical ly review theperformance of the gridfor the past period

RPC shall plan stable operation of the grid for future,considering various parameters and occurrences such as

frequency profile, voltage profile,

line loading,

grid incident,

grid disturbance, performance of protection schemes and

protection coordination


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5. Maintenance planning

The RPC shal l prepare annual maintenance planfor

Generating stations, ISTS

Coordinate the annual maintenance planfor inter

regional transmission system

Organise monthl y operating committee meetingsin the

region to review and revise the coordinated generation and

transmission system plan

The SLDCshall do the above for intra-state consti tuents

in consultation with the concerned transmission licensees

The generating company/ transmission licensee shall

obtain approval of the appropr iate LDCbefore actual shut

down


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6. Coordination in operations

No enti ty shal l introduce or take out the element of the

gridwithout the concurrence of the appropriate LDC

except in case of risk of safety of plant and personnel in

which case it must intimate the appropriate LDC.

The appropriate LDC shall inform all affected partiesof

the outage


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7. Operating instructions

Every generating company and transmission licensee shall

provide written operating instructions for each equipment

and operating procedure for sequence of operationsof power

system equipment in their control room

These instructions to be consistent with the manufacturers

instructions

Instructions and procedures to be reviewed and revisedby

generating company/ licensee.


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8. RLDCs and SLDCs Instructions to be recorded

All operating instructions given by RLDC and SLDC throughphone, fax, email shall be given a unique operating code number

and recorded . Voice recorder to be maintained for recording and

reproduction of conversation with time stamp/ tag.

Above records shall be preserved for six months.


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9. Under frequency relay settings

All entities shall set their UF relays and DF /DT relaysin

accordance with RPC plan to provide adequate load relief forgrid security and ensure the operation of these relays at the set

frequencies.

All entities shall include the Fr relay details in their daily report

to the RLDCs and RPCs. RPC shall carry our inspection of the

relays as and when required.


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10. Islanding schemes

The RPC shall prepare islanding schemes for separation

of systemswith a view to save healthy system from total

collapse in case of grid disturbance.

All entities shall ensure proper implementation of the

islanding schemes.

11 Categorization of Grid incident and


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11. Categorization of Grid incident and

Grid disturbance based on severity

Grid Incidentmeans tripping of one or more power systemelements of the grid, which requires rescheduling of load/

generator, without total loss of supply at the substation or loss

of integrity of the grid at 220 kV and above(132 kV in case of

NE region)

Grid Disturbancemeans tripping of one or more power

system elements of the grid, resulting in total failure of supply at

the substation or loss of integrity of the transmission system at220 kV and above(132 kV in case of NE region)


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11. Categorization of Grid incident and Grid

disturbance based on severity (contd)

Severity of grid incidents

GI 1: Tripping of one or more power system elements which requires

rescheduling of generator/ load, without loss of supply at a substation or

loss of integrity of grid at 220 kV level(132 kV in NE region)

GI 2: Tripping of one or more power system elements which requires

rescheduling of generator/ load, without loss of supply at a substation or

loss of integrity of grid at 400 kV level and above (220 kV in NER).

Severity of Grid disturbance

GD 1: When Generation or Load loss in a region < 10%

GD 2: When Generation or Load loss in a region is between 10% to 20% GD 3: When Generation or Load loss in a region is between 20% to 30%

GD 4: When Generation or Load loss in a region is between 30% to 40%

GD 5: When Generation or Load loss in a region is between 40% to 50%


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12. Reporting of events affecting grid operation

Any tr ipping of generating station or transmission elementshall be promptly reported by the respective entity to theappropriate LDC in the prescribed format.

The appropriate LDC shal l intimate the event to the SLDCand RLDCof the affected regions for further dissemination toall concerned.


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13. Reporting of grid disturbance

The RLDC shall inform occurrence of the grid disturbanceto the constituents and RPC at the earliest

The disturbance resulting in failure of power supply to large

areas in a state shall also be reported by RLDC to Authoritywithin 24 hoursof the occurrence of the grid disturbance.

The RLDC shall also post on its web site a brief grid

disturbance report indicating the affected area or the system,extent of outage and the likely cause of initiation.

14 Restoration of grid following incidence or


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14. Restoration of grid following incidence or

disturbance

TheRLDC in consultation with RPCshall develop proceduresfor

enabling restoration and normalization of the gridfor inter-statesystemat the earliest.

The SLDCshall also develop restoration procedures for intra-state

system.

The restoration procedures shall be reviewedfollowing addition of

generating station or transmission line or at least once in two years

and revised if considered necessary.

The above procedures shall be made available to, and be followed

by all concerned (entities, RLDCs and SLDCs).

15 Operational data during normal and grid


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15. Operational data during normal and grid

disturbance conditions

All real time dataas required by the appropriateLDC shall befur nished by the entities.

All data required by RPC, in discharge of the responsibilities to

it, shall be furnished by RLDC.

All operational data, including disturbance recorder and eventlogger reports, for analysing grid incident / disturbanceshall be

furnished by al l enti ties within 24 hrs to RLDC and RPC.

All equipments such as disturbance recorders and event loggers

shall be kept in healthy conditions. The RPC shall recommend remedial measuresto be taken on

the disturbance report of RLDC to prevent recurrence of GI and

GD.


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17. Communication Facilities

The communication facilities installed by the transmission

licensee shall be in accordance with CEA(Technical Standards

for Connectivi ty to the Grid) Regulations, 2007and shall bemaintained in good operating condition.


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18. Safety procedure

The enti ty shall prepare contingency procedures for use

of operatorsat each sub-station and switchyards and theseshall be regularly updated.

All operating personnel shall be trained in conti ngency

procedures at regular intervalsand they shall follow theprocedures.

The f i re f ighting equipment shal l be made available at allsub-stations, switchyards, etc and shall be checked

periodically for its upkeep and mock exercises in firefighting shall be carried out at least once in a year.


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19. Maintenance of tools and equipment

The maintenance staf f shall be made aware ofthe list of

tools, devices and equipment for various maintenance and

rectification works on Transmission lines, Substations,

Switchyards and Converter stations and the tools shall be madereadily available and certi f ied for usage.


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20. Maintenance procedures

The entity shall prepare maintenance proceduresfor each

equipment in line with the manufacturers

recommendations and prudent utility practices.


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21. Hot line methods

The hot line techniques for maintenance of cri tical

transmission l ines and sub-stationsshall be adopted where

ever possible.

Only trained staff shal l be used for the hot line techniques

and the tools employed shall have necessary certification from

a national or international laboratory before use.

22 Emergency Restoration System


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22. Emergency Restoration System

Each transmission licensee shall 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 in order to minimise the outage of the Transmission

L ines in case of tower failures.

(Emergency Restoration Systemmeans a system comprising

of transmission towers or structures of modular construction,

complete with associated components such as insulators, hardware

fittings, accessories, foundation plate, guys, anchors or installation

tools and the like to facilitate quick restoration of damaged orfailed transmission line towers or sections)

23 Inspection and patrolling


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All essential parameters which indicate the healthiness of the

equipment in a sub station, shall be inspected by the shif t

engineer once in each shif tand periodically by the officer in

charge.

Overhead linesshall be patrolled at periodicity decided by the

transmission licensee and different patrolling schedules shall

be implemented by the transmission licensee for normal

terrain, vulnerable terrain and most vulnerable terrain .

The important l inesshall be inspected by senior engineers

after patrolling by junior staff and maintenance works such as

tree cutting, replacement of damaged insulators shall be

carried out immediately after patrolling wherever required.

23. Inspection and patrolling

24 Maintenance schedules


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Entities shall identify cri tical equipmentand as far as possible, practice

condition based maintenancefor such equipment in place of time based

maintenance.

In case of time based maintenance, the periodicity of maintenance of lines

and substations located in polluted area or coastal area shall be more

frequent.

The maintenance of lines passing through and sub-stations located in such

areas should be completed before onset of winterso as to minimise

tripping under conditions of fog or due to salt deposit on insulator discs in

coastal areas and once before onset of summer.

The maintenance work on various items of equipment may be advanced

depending on the condition of the equipment.

24. Maintenance schedules


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25. Use of diagnostic Techniques forCondition monitoring of equipment

The diagnostic methods of maintenance shall be preferred over

traditional time based maintenance.


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26. Thermo-vision scanning

The thermo-vision scanning for hot spots on all overhead

lines and sub station equipmentat voltage level of 220 kV

and above shall be carried out at least once in a yearand

necessary remedial measures shall be taken where hotspots are detected.


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27. Failure Analysis

All failures of the equipment and tower collapse shall be

analyzed by the enti tyto avoid recurrence and a copy of thereport shall be submitted to the RPC and Authority

The authority may appoint a group of experts for investigation

and analysis and the representatives of the manufacturers may

be invited to participate in such analysis. All relevant datawhich may help the group of experts in

analysing the failures shall be furnished by the respective

Entities.

The recommendations of the group of expertsshall besubmitted to the authority and the recommendations accepted

by the authority shall be implemented and circulated to all

within the organisation and to other organisations to prevent

recurrence of such failures.

28 Inventory Control and Spare Parts


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28. Inventory Control and Spare Parts

Management

The required spare parts shall be kept in stock, to ensure

speedy maintenance of the equipment.

Computerised materials management system shall bedeveloped by the entities to optimise inventory.


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29. Maintenance Audit

An internal audit committeemay be established by the

entities to verify whether actual maintenance works are

carried out at site in compliance of the procedures and the

policy of the transmission company.

The observations of the committeeshall be put up to the

management of the entity for perusal and taking corrective

action, if any.

30 R id l Lif A t


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30. Residual Life Assessment

The RLA shall be carried out for all major equipment

including transformers, reactors, breakers, etc as envisaged by

relevant standards specified by the Bureau of Indian standards,

manufacturers instruction or industry best practices and

suitable remedial action for breach of the same shall be taken

by the management of the entity.


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31. Disaster Management

The maintenance staff shal l be trainedin disastermanagement and a detailed procedure for the same shall bedeveloped by the entity and displayed prominently.

The detailed procedure shall be reviewed per iodical lyandalso based on mock exercises carried out by the entity.

The equipment including vehicles, diesel generating setsand fire fighting equipment, etc shall be kept at sub-stationor at appropriate location for disaster management.


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32. Maintenance records

The records of all maintenance carried out for each equipment

shall be kept in the table and formats in electronic form and

hard copy and the next due date for maintenance of each item

of work shall be clearly marked in such tables and formats.


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33. Training

Every personinvolved in O&M of transmission lines shall betrained at the induction level and at least once in a year.

The shi f t staffshall be trained to make them thorough incarrying out operations at each substation and every person

concerned with real time operation shall be trained.

Every grid operatorshall undergo training in real time digitalsimulator and a refresher course at least once in two years.

The maintenance personnelof every entity shall also be trainedin preventive and breakdown maintenance of variousequipment and the personnel shall be trained in detailedmaintenance procedures.


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Grid Standard

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