khizar bhullar

POWER CIRCUIT BREAKERS
AND
SUBSTATIONS
BY
“Prof Dr. Suhail Aftab Qureshi”
"Prof Dr. Suhail Aftab Qureshi" 1

Power Circuit Breakers and Substations
Classification of circuit Breaker and isolators,
Terminology’ Circuit Breakers, Arcs, SF 6 Switchgear & Circuit
Breakers, Air Blast Circuit Breakers, oil Circuit Breaker, Special
Purpose Circuit Breakers & Isolators, D.C Circuit Breakers,
Breakers requirement, Testing, Switchgear Testing, Synthetic Testing,
Substation Layout and Design,
"Prof Dr. Suhail Aftab Qureshi" 2

Power Circuit Breakers and Substations
BOOKS
1. "Advances in H.V insulation and Arc
interruption'in SF 6 and Vacuum",
By V.N. Maller & M.S Naidu.
2. "Power Circuit Breakers Theory and Design",
By C.H. Flurscheim.
3. "ELECTRICAL SUBSTATION", ENGINEERING
AND PRACTICE,
BY S RAO.
"Prof Dr. Suhail Aftab Qureshi" 3

Contents
1. Classification of Circuit Breakers and
Isolators
a. Introduction
b. Circuit Breakers, Switching Isolators,
Isolator or Disconnectors
"Prof Dr. Suhail Aftab Qureshi" 4

2. Terminology:
Contents
a. Service Voltage
b. Recovery Voltage
c. Restriking Voltage (TRV)
d. Interruption with Restrikes
e. Prospective Current
f. Prospective Breaking Current
g. Breaking Capacity
h. Symmetrical Breaking Capacity
i. Asymmetrical Breaking Capacity
j. Making Current
k. Arcing Duration
l. Make Time
m. Operating Duty
"Prof Dr. Suhail Aftab Qureshi" 5

Contents
2. Terminology:
n. Load Current Interruption
o. Interruption of Induction Current (Fault
Currents, small, inductive current)
p. Interruption of capacitive Currents
q. Asynchronous switching
r. Auto Reclosure
s. Delayed Current Zero
t. Fault Making
u. Evolving faults.
"Prof Dr. Suhail Aftab Qureshi" 6

Contents
3. Circuit Breaker Arcs
a. Plasma and Thermal Ionisation (Substance i.e.
solid liquid, Gas, Plasma)
b. Ionisation Due to collision of Electrons
c. Deionization
d. Properties of the Arc
e. Striking the Arc
f. External Characteristics of the Arc
g. Arc stability.
h. Dynamic Arc characteristics
i. The A.C Arc
j. General Mathematical Arc Model
k. The Mayr Arc equation
l. The Cassie Arc equation
"Prof Dr. Suhail Aftab Qureshi" 7

Contents
3. Circuit Breaker Arcs
m. Application of Arc Models.
m1. Pre-zero current (low Arc Resistance)
m2. Post-zero current (High Arc Resistance)
"Prof Dr. Suhail Aftab Qureshi" 8

4. SF 6 Switchgear
Contents
a. Arc Interruption is SF 6
al .
Physical & Chemical Properties
a2. Arc Extinction is SF 6
a3. Nozzle Design
a4. Arc Extinction Parameters.
a5. Throat Blocking)
"Prof Dr. Suhail Aftab Qureshi" 9

4. SF 6 Switchgear
Contents
b. SF 6 Circuit Breaker
bl.
Arc chamber; General
b2. Double pressure Arc chamber
b3. Circuit Breaker Type. (Live Tank &
Dead)
c. SF 6 switching Isolators & other equipment.
cl.
Switching Isolators.
c2. Current Transformers
"Prof Dr. Suhail Aftab Qureshi" 10

Contents
5. Air Blast Circuit Breakers.
a. Arc extension
b. Pressurised Head- Atmospheric Head, Air
Blast C.B
b1. Constructions.
b11. Auxiliary Chambers.
b12. Tripping/Closing resistors.
b13. Auxiliary Equipment.
"Prof Dr. Suhail Aftab Qureshi" 11

Contents
6. Oil Circuit Breaker
a. General
b. Bulk-Oil circuit Breakers.
c. Minimum Oil Circuit Breaker.
7. Special Purpose Circuit Breakers &
Isolators.
a. Air Blast Breakers with transverse air Jet
b. Water circuit Breakers
c. Pantograph Isolator
"Prof Dr. Suhail Aftab Qureshi" 12

Contents
8. D.C Circuit Breakers.
a. Producing of current zero (Four different methods)
9. Circuit Breakers requirement.
a. Current Interruption
b. Recovery voltage withstand.
c. Recovery voltages calculation by current Injection
Techniques
c1. Current injection sequence.
c2. Examples of current Injection
d. Arc theory in short-line fault calculations
"Prof Dr. Suhail Aftab Qureshi" 13

Contents
10. Switchqear Testinq
a. High voltage TYPE TESTS (IEC-56-4)
al. Lightning Impulse Tests
a2. Switching Impulse test.
a3. Power-Frequency voltage tests
b. Short circuit current TYPE TESTS.
b1. Short-time current
b2. Breaking current
b3. Transient Restriking
b4. Load switching
b5. Earthing Condition
b6 Latching
b7. Contact Condition
b8. Critical current
"Prof Dr. Suhail Aftab Qureshi" 14

Contents
c. Type tests related to service conditions
c1. Short line fault
c2. Asynchronous switching
c3. Close loop switching
c4. Transformer magnetisting current
switching
c5. Capacitance current switching
"Prof Dr. Suhail Aftab Qureshi" 15

Contents
d. Miscellaneous TYPE tests.
d1. Mechanical
d2. Climatic Conditions
d3. Geographical Conditions
d4. Thermal
"Prof Dr. Suhail Aftab Qureshi" 16

Contents
e. Testing Equipment
e1. Generators and Transformers
e2. Part testing
e2.1 Single phase testing
e2.2 Unit testing
"Prof Dr. Suhail Aftab Qureshi" 17

Contents
11. Synthetic Testing
f1. Principles of synthetic testing
f2. Skeats Circuit
f3. Parallel Injection test circuit
f4. Series Injection test circuit
"Prof Dr. Suhail Aftab Qureshi" 18

Contents
12. Substation Layout and Design
a. Introduction
b. Basic Requirements
b1. System security
b2. Flexibility of operation
b3. Maintenance Facilities
b4. Protection Facilities
b5. Site-area & location
b6. Cost
"Prof Dr. Suhail Aftab Qureshi" 19

Contents
12. Substation Layout and Design
c. Busbar Configuration
c1. Single busbar
c2. Duplicate Busbar
c3. Duplicate Back to Back
c4. Transfer Busbar
c5. 1&1/2 Circuit Breaker Arrangement
c6. Mesh Arrangement
c7. By Pass Facilities.
c8. Location of current transformers
c9. Indoor or Outdoor substation
c10. Segregation
e11. Phase-segregated & Insulated phase Busbar.
"Prof Dr. Suhail Aftab Qureshi" 20

Contents
12. Substation Layout and Design
d. Substation Earthing.
d1. Earth Resistivity
d2. Design of earth meshes.
"Prof Dr. Suhail Aftab Qureshi" 21