Transcript grid stds-alka

Grid Connectivity Standards,
Grid standards
alka
NPTI, PSTI
Bangalore
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CEA’s 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 the
following
a.
CEA “Manual on Transmission Planning Criteria: 1994”
CEA “Report of the Committee for Updating the Best Practices
in Transmission System for the Country: 2002”.
Latest Issue of CBIP Manuals on: Layout of Substations,
Transmission Towers
Grid code
State Grid code
b.
c.
d.
e.
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1.Transmission system Planning & Design
ii.
a.
b.

The integrity of the regional grid is not affected under various
operating conditions including stipulated system contingencies
all elements of the transmission system shall be designed
taking into account the specified factors of safety in regard to
electrical, mechanical and civil aspects in the respective
standards
optimal system to be chosen after performing load flow, short
circuit, stability studies of the various transmission alternative
The system designed shall not impinge on the rating of the
substation equipment in any other sub station in the vicinity.
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2. Overhead Transmission Lines
d.
The transmission line proposed to be connected shall be
comply with the following
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
Foundation design for the tower to be developed by the
transmission licensee for various soil categories.
Use of multi circuit and narrow based towers wherever ROW
constraints exist
Each type of tower to be type tested for mechanical strength
ii.
Clearance from PTCC shall be obtained
i.
a.
b.
c.
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3. EHV/HV Underground Cables
i.
a.
b.
c.
d.
e.
f.
g.
Cables proposed to be connected to the system, shall comply with the
following
Shall be of XLPE type corresponding to IS 7098
Cable conductor to be of adequate size considering continuous current,
short circuit current, voltage drop etc, & shall correspond to IS-8130
Cables to be provided with proper sheathing, armoring & screening
Prior permission from appropriate authority to be obtained for digging
trenches, precautions to be taken
Route maps to be kept at Substation & markers shall be fixed to trace the
cables
Road crossing to be carried out by providing Hume pipes or GI pipes
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 and operational
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
Planning and design of substations to be based on the following
v.
All EHV circuit breakers to be of SF6 type
vi.
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
Planning and design of substations to be based on the following
xii. Power Supply to the sub station auxillaries
a. 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 to
be 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
Planning and design of substations to be based on the following
xiv. Reliable communication link shall be provided on all EHT
lines for voice, Fax, protection, telemetry & SCADA
xv. Substation grounding shall be done in accordance with IEEE80
xvi. Size and no. of ICTs to be selected such that outage of one
shouldn’t overload the remaining ICTs or the underlying
system
xvii. The stuck breaker condition in the substation shall not cause
disruption of more than 4 feeders in 132 or 220 kV system,
more than 2 feeders in 400 kV system and more than one
feeder in 765 kV system
xviii. In substations of 220 kV and above, control room, PLCC
room, Relay testing room and electronic laboratory shall be air
conditioned
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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 Compatibility
A 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.
ii.
iii.
iv.
For new connections, the CTU/ STU/ transmission licensee,
shall inform the transmission users seeking connectivity, the
BIL and important parameters of the equipment and ratings of
the surge arresters in its system adjacent to the connection
point.
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
The CTU/ STU/ transmission licensee shall determine the
ratings of the surge arresters to be installed at the connection
point
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 CEA’s 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, 2010
These 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. Definitions
•Bulk consumer – means a consumer who avails supply at
voltages of 33 kV or above
•Entity - means a Generating company or a transmission licensee
or a distribution licensee or a bulk consumer
•Voltage Unbalance – Ratio of the maximum voltage deviation of
the phase voltage from the average phase voltage to the average
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phase voltage
3. Standards for operation and
maintenance of transmission lines

All entities
 LDCs
 RPCs
a)
Frequency Control
Operating Range : 49.5 to 50.2 Hz or as per grid
code, except during the transient period
following tripping.
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b) Operating Voltage Limits
S.No.
Normal system
Maximum (kV
Voltage (kV rms) 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
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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
2
4
132
170
3
5
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Decided by the state
commission in the respective
State grid code
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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 series
compensation
 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 periodically review the
performance of the grid for 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 shall prepare annual maintenance plan for
Generating stations, ISTS
Coordinate the annual maintenance plan for inter
regional transmission system
Organise monthly operating committee meetings in the
region to review and revise the coordinated generation and
transmission system plan
The SLDC shall do the above for intra-state constituents
in consultation with the concerned transmission licensees
The generating company/ transmission licensee shall
obtain approval of the appropriate LDC before actual shut
down
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6. Coordination in operations

No entity shall introduce or take out the element of the
grid without 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 parties of
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 operations of power
system equipment in their control room

These instructions to be consistent with the manufacturers’
instructions

Instructions and procedures to be reviewed and revised by
generating company/ licensee.
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8. RLDCs and SLDCs Instructions’ to be recorded
• All operating instructions given by RLDC and SLDC through phone, 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 relays in
accordance with RPC plan to provide adequate load relief for
grid 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
systems with a view to save healthy system from total collapse in
case of grid disturbance.
•
All entities shall ensure proper implementation of the
islanding schemes.
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11. Categorization of Grid incident and
Grid disturbance based on severity

“Grid Incident” means tripping of one or more power system
elements 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 Disturbance” means 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 at 220 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 tripping of generating station or transmission element
shall be promptly reported by the respective entity to the
appropriate LDC in the prescribed format.

The appropriate LDC shall intimate the event to the SLDC
and RLDC of the affected regions for further dissemination to
all concerned.
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13. Reporting of grid disturbance
•
The RLDC shall inform occurrence of the grid disturbance to 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 Authority within 24 hours
of 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.
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14. Restoration of grid following incidence or
disturbance

The RLDC in consultation with RPC shall develop procedures for
enabling restoration and normalization of the grid for inter-state
system at the earliest.

The SLDC shall also develop restoration procedures for intra-state
system.

The restoration procedures shall be reviewed following 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).
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15. Operational data during normal and grid
disturbance conditions

All real time data as required by the appropriate LDC shall be
furnished 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 event
logger reports, for analysing grid incident / disturbance shall be
furnished by all entities 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 measures to be taken on
the disturbance report of RLDC to prevent recurrence of GI and
GD.
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16. Operational data records

Operational data (including equipment and system
parameters) logged manually and electronically shall be
preserved for at least three years.
 Logbooks to be maintained by every by every manned
switchyard and substation. The unmanned sub-station data
shall be maintained by the concerned control centre.
 All observations shall be in chronological order.
 The observations made during inspection including
important parameters and deviation of parameters outside
permissible tolerances also be recorded in the log book.
 The RPC shall keep the record of grid incidences and grid
disturbances for each financial year. It shall include
sequence of tripping, the cause, and the sequence of
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restoration, remedial measures taken to avert such
17. Communication Facilities

The communication facilities installed by the transmission
licensee shall be in accordance with CEA(Technical Standards
for Connectivity to the Grid) Regulations, 2007 and shall be
maintained in good operating condition.
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18. Safety procedure

The entity shall prepare contingency procedures for use of
operators at each sub-station and switchyards and these shall be
regularly updated.

All operating personnel shall be trained in contingency
procedures at regular intervals and they shall follow the
procedures.

The fire fighting equipment shall be made available at all
sub-stations, switchyards, etc and shall be checked periodically for
its upkeep and mock exercises in fire fighting shall be carried out
at least once in a year.
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19. Maintenance of tools and equipment

The maintenance staff shall be made aware of the 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 made
readily available and certified for usage.
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20. Maintenance procedures
The entity shall prepare maintenance procedures for each
equipment in line with the manufacturer’s recommendations and
prudent utility practices.
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21. Hot line methods
• The hot line techniques for maintenance of critical transmission
lines and sub-stations shall be adopted where ever possible.
• Only trained staff shall be used for the hot line techniques and
the tools employed shall have necessary certification from a national
or international laboratory before use.
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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
Lines in case of tower failures.
( “Emergency Restoration System” means 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 or
failed transmission line towers or sections)
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23. Inspection and patrolling
• All essential parameters which indicate the healthiness of the
equipment in a sub station, shall be inspected by the shift engineer
once in each shift and periodically by the officer in charge.
• Overhead lines shall 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 lines shall 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.
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24. Maintenance schedules
• Entities shall identify critical equipment and as far as possible, practice condition
based maintenance for 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 winter so 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.
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25. Use of diagnostic Techniques for Condition
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 equipment at voltage level of 220 kV and above
shall be carried out at least once in a year and necessary
remedial measures shall be taken where hot spots are detected.
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27. Failure Analysis

All failures of the equipment and tower collapse shall be
analyzed by the entity to avoid recurrence and a copy of the
report 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 data which may help the group of experts in
analysing the failures shall be furnished by the respective
Entities.
 The recommendations of the group of experts shall be
submitted 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.
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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 be
developed by the entities to optimise inventory.
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29. Maintenance Audit
•
An internal audit committee may 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 committee shall be put up to the
management of the entity for perusal and taking corrective
action, if any.
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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 shall be trained in disaster
management and a detailed procedure for the same shall be
developed by the entity and displayed prominently.
•
The detailed procedure shall be reviewed periodically and
also based on mock exercises carried out by the entity.
•
The equipment including vehicles, diesel generating sets
and fire fighting equipment, etc shall be kept at sub-station
or 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 person involved in O&M of transmission lines shall be
trained at the induction level and at least once in a year.
•
The shift staff shall be trained to make them thorough in
carrying out operations at each substation and every person
concerned with real time operation shall be trained.
•
Every grid operator shall undergo training in real time digital
simulator and a refresher course at least once in two years.
•
The maintenance personnel of every entity shall also be trained
in preventive and breakdown maintenance of various
equipment and the personnel shall be trained in detailed
maintenance procedures.
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Thank you
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