Design Aspects, Major Challenges 765 kV Substation Substations s
Purshottam Kalky , 25.03.10
Design Aspects, Major Challenges 765 kV Substation Substations s
Purshottam Kalky , 25.03.10
Index Development of HVAC in world and Areva T&D Experience of
765k 765kV V Syst System em.. Design Asp Aspects and Major Challenges of 765kV System. Des as c
es gn parame ers .
State-of-the-art -art –technologie –technologies. s. State-of-the
Future Ma or Challen e .
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Retu Returrn of Exper xperie ienc nce es –Case Case Studi tudies es..
Development of Voltages Levels for AC Power Transmission World
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Development of Voltages Levels for AC Power Transmission World
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Development of Voltages Levels for AC Power Transmission India
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765kV Substations – Areva Presence S.No. Substations
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Customer
Status
1
765 KV in Venezuela
EDELCA’s,Brazil
Commisioned
2
765kV Sipat
NTPC
Commisioned
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765kV Anpara –C
Lanco Infratech Ltd. (LITL) Ongoing
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765kV Lucknow and Balia
PGCIL
Ongoing
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765kV Bhivani
PGCIL
Ongoing
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765kV Anpara - D
UPPTCL
Ongoing
9
765kV Sasaram
PGCIL
To Start
Basic Design Parameters
System Operating Voltage System Highest Voltage Lightning Impulse withstand Voltage (kV) Switching Surge withstand Voltage (kV) Power Fre uenc Withstand Volta e r.m.s. (kV) Max. Fault Level for 1 sec. (kA) Minimum Creepage Distance (mm) Minimum Corona extinction voltage (kV) Clerances (mm) Phase to Phase Phase to Earth Sectional Clearances
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765 kV 800 kV ± 2100 ± 1500
400 kV 420 kV ± 1500 ± 1050
830 40 20000 508
630 40/50/63 10500 320
7600 4900 10300
4200 3500 6500
Basic Design Parameters 4.5 Inch (120mm) or Rigid Conductor higher Flexible Conductor Per Phase Flexible conductor Arrangement (mm) At Main Bus and Jack Bus Level At Equipment Level Equipment Level (m) Main Bus Level (m) Phase to Phase spcing (m) Bay Width (m) 9
Bull (38.24mm Dia)
4 Inch Moose (31.77mm Dia)
4 X Bull
4 X Moose
450/457 300
450/457 450/457
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8
26/27 14/15
15 6/7
51.5
24 /27
State-of-the-art technologies The detail study was done to find an acceptable balance between parameters impacting in the bundle design in EHV like corona, short circuit pinch effect and electrical field in a 765 kV . »
»Short circuit mechanical criteria
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Corona – RIV criteria
Electrical field & health criteria
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Size of bare stranded conductor bundle
SELECTED WORKING AREA
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'
State-of-the-art technologies Electric and Magnetic Field Consideration related
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to the 765 kV Substations. The advent and increasing use of higher voltage lines has increased the relative importance of field effects such as induced voltage and current in conducting bodies.
concerned about potential adverse health effects of exposure to electric and magnetic fields at extremely low frequencies (ELF). Such exposures arise mainly from the transmission and use of e ectr ca energy at t e power requenc es o 50/60 z. WHO's International EMF Project has been established to work towards resolving the health issues raised by EMF exposure.
identified. A formal task group meeting to assess the results was held by IARC in 2001. WHO adopted IARC's conclusions after assessment of noncancer health risks in 2002.
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State-of-the-art technologies The International Commission on Non-Ionizing Radiation Protection as pu s e gu e nes on exposure m s or a .
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The guidelines provide adequate protection against known health effects and those that can occur when touching charged objects in an external electric field. »
Limits of EMF exposure recommended in many countries are broadly similar to those of ICNIRP, which is a non-governmental organization (NGO) formally recognized by WHO and a full partner in the »
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State-of-the-art technologies following geometry based on the layout :
S.No. Variable 1
Umax
Qualifier 800 kV .
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3
Conductor bundle
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Conductor Diameter
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Sub-Conductor Spacing
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Phase conductor separation
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Phase conductor height above ground
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Busbar Current
4 X Bull 38.25 mm 450/300mm 14 m 14,26 & 38 m 600 A
State-of-the-art technologies , most exposed area (lower connection level) is 7.20 kV/m < 10 kV/m…taken into account all future extension with 300mm quad bull bundle for equipment at 14m level.
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State-of-the-art technologies
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State-of-the-art technologies »
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Equipotential lines
State-of-the-art technologies »
Magnetic field in 765 kV substations
Ball
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In any cases the magnetic fields in this the working area is 67 T < 500 T.
State-of-the-art technologies »
The corona effect on conductor and connectors.
The Corona effect (disruptive discharge) is due to important electrical field in the ver close area of the bare conductor / bare accessories). For 765 kV it’s a main criterion. »
Due to increment of the corona effect with the proximity of the ground, the management of the bundle design needs deep nves ga ons or connec on e ween appara uses. »
The critical surface gradient of a cylindrical cable has been evaluated using Peek's formula (inception of Corona effect). »
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State-of-the-art technologies Following observation was made during corona study.
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The ratio of operating conductor surface gradient to corona inception gradient should Eops/Ec < 0.90 »
The optimum conductor spacing for the minimum conductor surface gradient (adjacent conductor spacing , not diagonal distance ) is seen from the range of 300 to 400 mm . »
Continuous corona will also generate high levels of radio noise and corona losses in dry conditions. The extraneous radio noise will increase background noise levels and so pollute the local »
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State-of-the-art technologies Following observation was made during corona study for
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connectors connectors and equipment limitations / design. Test have been carried from 200mm to 450mm cable spacing, u to 130% of Um i.e. 660 kV hase- round based on a corona design optimised initially for 457mm cable spacing. »
As expected extinction voltages are quite similar from 300mm and 450 mm spacing, except for the spacer. »
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State-of-the-art technologies
The spacer design is the most critical material in this case, a redesign of spacer had carried and tested again to meet requirement. »
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State-of-the-art technologies Some Important design issue in terms of Corona for Non –Ceramic Insulators (NCI). »
The presence of corona activity is a good indication of trouble with .
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Corona in such situations is common and not only results in customer complaints about audible noise and radio interference but also degrades the polymeric rubber material of the NCI, which in turn can cause premature a ure o t e nsu at on. »
Hence proper corona shielding shall be provided for NCI in 765 kV Substations. »
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State-of-the-art technologies Corona Issue with NCI
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State-of-the-art technologies Short Circuit force for Towers and Equipment terminals. At first simplified methods for calculation by hand had been developed for typical cases based upon International standard IEC 60865. In the past only the static behavior of the support has been taken into account.
es gn oa s sugges e n a e e max mum instantaneous values of short-circuit tensile force Ft, drop force Ff, pinch force Fpi as static load for design purposes. This methodology is not feasible as well as economical for higher system voltages.
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State-of-the-art technologies We find to alternate advance methods as International standard IEC 60865 is applicable for voltage class up to 420kV. Now days analytical and numerical methods or a combination of
finite element or finite difference modeling. These software further based upon combination of International standard IEC 60865 and CIGRE 214 : “The Mechanical effects of ” 23.03. Recent development concerns a more on true impact of dynamic loading .
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State-of-the-art technologies Some SCF videos which exactly can simulate in today’s software's.
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State-of-the-art technologies Taken a 450mm bundle as reference 100% for traction load at
apparatus terminals, a 300mm arrangement reduce the short circuit stress of 20% Stress on equipment terminal
120% 100%
Main
80%
BF
60% 40% 20% 0% mm
mm
mm
mm
Bundle spacing
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mm
mm
State-of-the-art technologies Control Switchin of Circuit Breakers.
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Optimizing a circuit breaker’s closing or opening moment is of utmost importance when switching reactive loads because random switching can sometimes result in high transient overvoltage's and inrush . »
These transients generate stresses for all substation and network equipment, leading to accelerated aging or – in the worst casedestruction of equipment. »
The RPH2 provides a reliable , low – cost way to reduces these switching transients to an acceptable level. Serving as a control unit , it delays the switching order – phase by phase –until the pre- defined switching time (depending on current / voltage network characteristics) that reduces switching transients to minimum level. »
The RPH2 is particularly important element when switching large transformer , shunt reactors, capacitors and uncompensated lines. »
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State-of-the-art technologies »Insulation Coordination The study shall be carried out using ELETROMAGNETIC TRANSIENT PROGRAM (EMTP), which is a well established program or suc s u es. »
The study shall be carried out in accordance with IEC71-1 and - .
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The switchyard along with the transmission lines shall be modeled
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equipments as well as the distances between the equipments shall be taken from this diagram. Various configurations (open close status of breakers) of the switchyard shall be considered to arrive at the maximum overvoltage levels at different points in the switchyard. »
Switching overvoltage study shall be carried out due to switching of incoming line breakers at remote end. »
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State-of-the-art technologies »Insulation Coordination The study shall be carried out using ELETROMAGNETIC TRANSIENT PROGRAM (EMTP), which is a well established program or suc s u es. »
The study shall be carried out in accordance with IEC71-1 and - .
»
The switchyard along with the transmission lines shall be modeled
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equipments as well as the distances between the equipments shall be taken from this diagram. Various configurations (open close status of breakers) of the switchyard shall be considered to arrive at the maximum overvoltage levels at different points in the switchyard. »
Switching overvoltage study shall be carried out due to switching of incoming line breakers at remote end. »
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Future Major Challenges Online Switching for Spare ICT
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Future Major Challenges Online Switching for Spare Line reactor with Single phase CB
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Return of Experience- Sipat Flashover at GT-4 Suspension Insulator.
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Return of Experience- Sipat Flashover at GT-4 Suspension Insulator. - Proposal
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Return of Experience- Sipat RPH2 – Alarm Indication
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On Rph2 following alarm indications shown on display “command time” min. and “operating time max.” »
Investigation carried out and final conclusion was to separate Input /output signal in separate cable. »
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Conclusion According to our experience, EHV Projects require a min i n i r i n f key-factors which may not be voltage Projects.
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Thank ou for our attention!
to provide additional information at the end of this lecture on any other topic of interest to you. »
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by you.
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