basics of switchgears
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Basics of Switchgear
Siva KumarRegional Support ManagerPower Electronics – Middle EastCummins Power Generation Kent
What do we mean byWhat do we mean byWhat do we mean byWhat do we mean by
Switchgear?Switchgear?Switchgear?Switchgear?
Switchgear is the Generic name for the
components used in Electrical Switchboards,
which can be for Low Voltage or High Voltage
Systems
Example of Switchgear Components: Air
Circuit Breakers (ACB), Moulded Case Circuit
Breakers (MCCB), Vacuum Circuit Breakers(VCB), etc.,
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What do we mean by System?What do we mean by System?What do we mean by System?What do we mean by System?
The complete Assembly of the Switchgear
Components, Enclosures, Busbars, Wiring and
accessories – Tested and certified by
designated Testing and Certification authorities
respectively in accordance with relevant
standards.
Why do we needWhy do we needWhy do we needWhy do we need
Switchgear / Systems?Switchgear / Systems?Switchgear / Systems?Switchgear / Systems?
To Safely and Efficiently supply power from the
point of Generation to the Ultimate point of
consumption.
SAFETY BEING THE KEY WORD
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How is the Safety being ensured inHow is the Safety being ensured inHow is the Safety being ensured inHow is the Safety being ensured in
a Switchgear Systema Switchgear Systema Switchgear Systema Switchgear System
By providing a physical barrier from live
components thus reducing the risk of
accidental contact
By Ensuring safe containment of Arcing
Current during normal operation or a short
circuit fault.
By tripping the protective devices, thus safely
clearing a fault condition.
How are physical barriersHow are physical barriersHow are physical barriersHow are physical barriers
specified?specified?specified?specified?
Ingress Protection (IP) – specify the extent to
which Physical objects or liquid can penetrate
a surface or an enclosures. Typically has two
numbers and an alphabet.
Specified in IEC529:1989
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How is Construction of How is Construction of How is Construction of How is Construction of
Switchboard Specified?Switchboard Specified?Switchboard Specified?Switchboard Specified?
The construction of Switchboards are broadly
called as Forms.
Form1 to Form4.
The difference between the forms is in the way
the Incomer unit, Outgoing Unit, Busbar,Glanding and Terminations are located.
Specified in IEC439-1
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Common Tripping DevicesCommon Tripping DevicesCommon Tripping DevicesCommon Tripping Devices
in Switchgear / Systemsin Switchgear / Systemsin Switchgear / Systemsin Switchgear / Systems
Overload
Short Circuit
Earth Leakage / Earth Fault
(IEEE has issued Standard Device Numbers
for possible protections in electrical Power
Systems – Recognized as ANSI Standard)
volt-amperes
Key:
A Ammeter
Hz Frequency meter
KW Kilowatt
KWH Kilowatt hour
KVA Kilovolt amperes
Pf Power factor
RVar’s Reverse volt-amperes
SS Sync scope
V Voltmeter
Under voltage
25 Sync check
32 Reverse power
40 Field over current
51 Over current
59 Over voltage
65 Governor
81u Under frequency
86 Lockout
90 Voltage regulator
PCC3201 ANSI Diagram
(Paralleling)
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Popular StandardsPopular StandardsPopular StandardsPopular Standards
UL – US and Territories
IEC / BS – Extensively used in rest of the world
VDE - Germany
CSA – Canada (based on UL)
Various other standards apply to specific
industry / products (NFPA, ATEX, Lloyds
Registry, etc.,)
IEC / BS / ENIEC / BS / ENIEC / BS / ENIEC / BS / EN
International Electrotechnical Commission
British Standards
Eurpeon Norm.
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How do we know that the system willHow do we know that the system willHow do we know that the system willHow do we know that the system will
perform what they claim?perform what they claim?perform what they claim?perform what they claim?
Type Test Certificates
These are documents issued by the certifyingauthorities such as ASTA, Alpha, Kema, etc.,against test results from approved TestingLabs
Type Test
A test carried out on the Component / System
to determine compliance to specified Standard
LV and MV Switchgear Systems
- Low Voltage System <1000V
(380V, 400V, 415V, 440V, 660V are the common
3 Phase Voltages.)
- Medium Voltage System 1kV to 35kV
(3.3kV, 6kV, 11kV, 22kV, 33kV are the common
3 phase Voltages)
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Voltage Selection(These Statements are ‘GENERALLY’ True)
Low voltage systems have lowest equipment cost, easiest service
Applications with long runs may mitigate toward operatingat higher voltage levels
Line voltage is probably best for emergency servicereliability
Use medium voltage when:
Genset (current or total in future) ampacity exceeds 8000amps
If using Utility main, >5000A
Genset fault current exceeds 200kA
Can use step up transformers on LV gensets
What do we consider to be “standard” system types??
Medium Voltage Components
-Circuit Breakers
-Load Break Switches
-Single Operation Switches
-Ring Main Units
-Switch Fuse Units
-Busbar Assembly
-Protection (Relays, PTs, CTs)
-Earthing Switch
-Metal Clad Switchgear
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What to look out for in a project
specification
System Voltage
Busbar Current Rating
Feeder Current Rating
Breaking Capacity
Neutral Grounding Resistors
Construction
-Fixed or Withdrawable
-Vacuum or SF6
Applicable Standards for MV
Circuit Breaker: IEC62271-100 / ANSI C.37-09
Load Break
Switches: IEC60265-1 / ANSI C37.74
Switch Fuse
Combination: IEC62271-105
MV Switchboard: IEC62271-200
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Type Tests on Circuit Breakers andSwitches
Making and Breaking of Short Circuits
Mechanical Endurance
Making and Breaking of circuits with capacitive
loads
Dielectric Tests
Temperature Rise Tests
Type Tests on MV Switchboards
Short Time Current on Main & Earthing Circuits
Internal Arc Fault Tests
In Addition to the tests on individual circuit
breakers (mentioned in previous slide)
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Basic CalculationApparent Power (kVA) = √3 x U x I
Active Power (kW) = √3 x U x I x CosΦ
Reactive Power (kVAr) = √3 x U x I x SinΦ
U – RMS Phase to Phase Voltage (in kilo Volts)
I – RMS Phase Current (in Amperes)
CosΦ – Power Factor
Φ – Phase Angle (Between Apparent Power and
Active Power)
Graphical Representation
k V A = l
o a d ( A p p a
r e n t P o
w e r )
kW = Actual Power - Engine
k V A r =
R e a c t i v e P o w e r - A l t e r n a t o r
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Basic CalculationApparent Power (kVA) = √3 x U x I
Active Power (kW) = √3 x U x I x CosΦ
Reactive Power (kVAr) = √3 x U x I x SinΦ
Therefore,
Apparent Power = Active Power x CosΦ (PF)
No Load PF of a Genset is set at 0.80
Sample Calculation
Apparent Power = 150 kVA
System Voltage = 400V (equals 0.4 kV)
Active Power = 150 x 0.80 = 120kW
What is Current Delivered by the genset?
Apparent Power (kVA) = √3 x U x I
I = kVA / (U x √3)
I = 150 / (0.4 x 1.732) = 216.51 Amps
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QuizWhat is the current rating of GTEC to be selected
for a prime rated C300D5?
Missing information?
Oops!
System Voltage = 400V
Answer
Answer = 433.02 Amps
Selection: 500A GTEC
It was meant to be a trick question.
You should consider Standy Rating for
calculations, because
1. Prime Ratings do allow for 10% Overload.
2. 400A GTEC barely permits a 1% OverloadCapacity on 396.94 Amps Full Load Current.
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Switchgear Systems Supplied by PESwitchgear Systems Supplied by PESwitchgear Systems Supplied by PESwitchgear Systems Supplied by PE
We ensure that the Switchboards and the
Components are fully type tested assembled by
the original manufacturer.
Pros
Ensure that the system is Authentic.
Peace of Mind for the Client
Cons
Marginally, more expensive compared to the
locally assembled
Thanks for your time
Any Questions or Comments?
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