Switchgear Design

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PURPOSE OF PROTECTIVE RELAYS

  • TO DETECT ABNORMALITIES (FAULTS)
  • TO ELIMINATE SUCH ABNORMALITIES

By isolating smallest portion of the system
In a shortest period of time.

  • TO PREVENT DAMAGE TO EQUIPMENTS
  • TO PREVENT INJURIES TO PERSONNEL

RELAY OPERATION WHEN A FAULT OCCURS

Each relay should protect a specific zone in the system
If fault is inside its zone,relay should operate and isolate the zone
If fault is outside zone,Relay should not operate –Some other relay should operate and isolate

CONNECTION DIA OF O/C & E/F RELAY


CONNECTION DIA OF O/C & E/F RELAY

Protection Relay

A device which sense the fault and give a signal to the circuit breaker for tripping.

WHAT DO WE MEAN BY PROTECTION?

PROTECTION OF VARIOUS COMPONENTSOF POWER SYSTEM AGAINST VARIOUSTYPES OF SYSTEM FAULTS

VARIOUS TYPES OF EQUIPMENTS

  • GENERATORS
  • TRANSFORMERS
  • MOTORS
  • FEEDERS
  • TRANSMISSION BUS BARS
  • LINES
  • CAPACITORS
VARIOUS TYPE OF FALUTS
 R-Y-B-G OR R-Y-B(Symmetrical Fault)
 R-Y
 Unsymmetrical Faults
 Y-B
 B-R
 R-Y-G
 Y-B-G
 B-R-G
 R-G
 Y-G
 B-G

POWER SYSTEM -FAULTS


 Current

Over Load
Over Current
Earth Fault
Current Unb.
Dir. Over Cur.
Dir. Earth Fault
 Voltage

Over Vol.
Under Vol.
Voltage Unb.
Neutral shift
 Power
Over power
Under power
Reverse power
Computed
Over fluxing
Loss of field
Diff. O/C
Restricted E/F
Under Imp.
Frequency
Over Freq.
Under Freq.
dF/dT
Control/Mgmt.
Synchronising
Load sharing
Islanding
Load shedding

Breaker Selection Chart For Normal Design and RE Design

Breaker Selection Chart For Normal Design
Breaker Slection chart for RE-Design
 #8BK80-12KV-600mm Width-3AH5

STC-26.3KA & UPTO 31.5KA
3AH5 is available for 800A & 1250A

#8BK80-12KV-800mm Width-3AH3
STC-31.5KA & UPTO 40/44KA
3AH3 is available for 1250A & 3150A

#8BK88PLUS-12KV-600mm Width-3AH0
STC-UPTO 26.2KA
3AH0 is available for 800A,1250A & 1600A

#8BK80-24KV-1000mm Width-3AH3
STC-UPTO 26.3KA
3AH3 is available for 1250A & 2000A

#8BK80-36KV-1100mm Width-3AH3
STC-UPTO 31.5KA
3AH3 is available for 1250A,2000A & 2500A

 #8BK80-12KV-600mm Width-3AH5P

STC-26.3KA & UPTO 31.5KA
3AH5P is available for 800A & 1250A

#8BK80-12KV-800mm Width-3AH5P
STC-UPTO 31.5KA
3AH5P is available for 2000A & 2500A

#8BK80-12KV-700mm Width-3AK6
STC-40/44KA
Rating Should be <=1250A

#8BK80-12KV-800mm Width-3AK6
STC-31.5/40/44KA
Rating Should be >1250A

CABLE & CT COMPARTMENT

The cable compartment contains:


  • Bushing with the mating contacts for the lower contact arms of the withdrawable part.
  • Cable termination pieces.
  • A section of the main earth busbar.
  • Current transformers.
  • The cable termination pieces are accessible from the rear.
  • Earth switch, Lightning arrestor, Drawout type PT are also mounted in cable chamber

COMPARTMENT FOR LOW VOLTAGE EQUIPMENT
This compartment contains all the low voltage devices. 

e.g.

  • Protective relays, 
  • MCB’s,
  • Terminals,
  • Control fuses etc.
  • Indications and relays are accommodated in door cutouts.

CIRCUIT BREAKER COMPARTMENT

  • The circuit breaker compartment Contains a withdrawable truck with vacuum circuit breaker.
  • The breaker terminals are fitted with contact arms. 
  • The withdrawable trolley can be transferred between the Service and Test positions behind closed doors using a hand crack.
BUSBAR COMPARTMENT


Busbar compartment contains:

  • The busbars. 
  • Bushing with the mating contacts for the upper contact arms.
  • Feeder Connections.
  • The main Busbars are mounted on cast resin insulators.
  • Smaller main Busbars are connected with the longer Busbar links extending from one panel to the next.