basics of switchgears

7/29/2019 Basics of Switchgears

http://slidepdf.com/reader/full/basics-of-switchgears 1/14

Cummins Global Brand 10/28/2009 1:23:01 P

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.,




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




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




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




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)




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.




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)




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




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




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)




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




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




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.




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?

basics of switchgears

Documents