10LV&MVSwitchgear #10

Equipment behaviourd i h i iduring short‐circuits

1. Passive equipment

2 Active equipment2. Active equipment

M M M M

Active equipmentActive equipment

• This category comprises the equipment designed toThis category comprises the equipment designed toclear short‐circuit currents, i.e. circuit breakers andfuses.

• This property is expressed by the breaking capacityp p y p y g p yand, if required, the making capacity when a faultoccurs.

12

77

2

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

‐3

‐8

Current Limiting                    Non‐current Limiting 

12

77

2

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

‐3

‐8

Current Limiting                    Non‐current Limiting 

12

77

2

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

‐3

‐8

Current Limiting                    Non‐current Limiting 

Making Current

12

7

2

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

‐3

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

‐8

LV Circuit Breaker TypesLV Circuit Breaker Types

• Air Circuit Breaker (ACB)• Air Circuit Breaker (ACB)

• Molded Case Circuit Breaker (MCCB)

• Miniature Circuit Breaker (MCB)

Circuit Breaker TypesCircuit Breaker Types

• ACB: 630 to 6000 A, motorizableACB:  630 to 6000 A, motorizable

• MCCB: up 1600A, motorizable

• MCB (below 100A)• MCB (below 100A)

LV Circuit Breakers 

ACB

MCCB

M M M M

MCCBACB

M M M M

Air Circuit BreakerAir Circuit Breaker

Molded Case Circuit BreakersMolded Case Circuit Breakers

• This is the external cover of the MCCB, which houses,all the sensing and operating components.

• Resin/glass‐fiber materials, with high dielectricstrength.

• It is to be noted that the case is moulded and assuch, it is not possible to access the internalpcomponents in case of any failures and it will benecessary to replace the complete MCCB under thosecircumstancescircumstances.

Miniature Circuit BreakersMiniature Circuit Breakers

• The miniature circuit breakers are similar to mouldedThe miniature circuit breakers are similar to mouldedcase circuit breakers but as their name implies, theseare smaller in size and are mostly used for currentratings below 100 A.

• These are normally available in single pole(SP), single pole neutral (SPN), double pole( ) l l ( ) l l l ( ) d(DP), triple pole (TP), triple pole neutral (TPN) andfour pole (FP) versions.

LV Circuit Breaker CurrentsLV Circuit Breaker Currents

• Rated uninterrupted current, Iup ,

• Rated current, In

• Rated ultimate short‐circuit breaking capacity, Icug p y,• Rated service short‐circuit breaking capacity, Ics• Rated short‐circuit making capacity, Icm

• Rated short‐time withstand current Icw (1sec. , 3 sec.)

In, IuIn, Iu

LV Circuit Breaker CurrentsLV Circuit Breaker Currents

• Rated uninterrupted current, Iup ,

• Rated current, In

• Rated ultimate short‐circuit breaking capacity, Icug p y,

• Rated service short‐circuit breaking capacity, Ics

• Rated short‐circuit making capacity, IcmRated short circuit making capacity, Icm

• Rated short‐time withstand current Icw (1sec. , 3 sec.)Rated short time withstand current Icw (1sec. , 3 sec.)

LV Circuit Breaker CurrentsLV Circuit Breaker Currents

• Rated uninterrupted current, Iup ,

• Rated current, In

• Rated ultimate short‐circuit breaking capacity, Icu

• Rated service short‐circuit breaking capacity, Ics

• Rated short‐circuit making capacity, Icm

• Rated short‐time withstand current Icw (1sec. , 3 sec.)

Utilisation CategoryUtilisation Category

Utilization category Ag y• Without an intentional short‐time delay forselectivity under short‐circuit condition andtherefore without a short time withstand currenttherefore without a short‐time withstand currentrating.

Utilization Category B• With an intentional short‐time delay (which mayy ( ybe adjustable) provided for selectivity undershort‐circuit conditions.

Rated Short‐time Withstand CurrentRated Short time Withstand Current

MCBMCB

• For type ‘B’ the breaker must trip between the limits yp pof 3 to 5 times rated current

• For type ‘C” the breaker must trip between the limits of 5 to 10 times rated current

• For type ‘D’ the breaker must trip between the limits of 10 to 20 times rated currentof 10 to 20 times rated current.

CascadingCascading

NS250L (breaking capacity 150 kA)

NS100N (breaking capacity 25 kA)NS100N (breaking capacity 25 kA)

C60N (breaking capacity 10 kA)

MV Circuit Breakers 

M M M MM M M M

MV Circuit BreakersMV Circuit Breakers 

• Oil circuit breakersOil circuit breakers

• SF6 circuit breakers

• Vacuum circuit breakers

MV Circuit Breaker CurrentsMV Circuit Breaker Currents

• Rated normal currentRated normal current

• Rated short‐circuit breakingRated short circuit breaking

• Rated short‐circuit making

• Rated short‐time withstand current (1sec. , 3 sec.)

SubstationSubstation

• Medium‐voltage switchgear rooms

• Low‐voltage switchgear rooms

1 Medium voltage switchgears shall be1. Medium‐voltage switchgears shall be installed in separate rooms. 

2. In the case of single‐row arrangement, a passageway of min. 1‐1.5 m shall be provided.of min. 1 1.5 m shall be provided. 

3. On the rear side of the switchgear a clearance of 1‐1,5 m shall be foreseen. 

1.5 m

1.5m

4. In the case of two‐row arrangement, the g ,passageway between the two operating panels shall be min. 1‐1.5 m. 

1.5 m

5. The room height shall be min. 4 m. (clear height from floor level to lower edge of HVAC ducts)floor level to lower edge of HVAC ducts).

4 m

Incoming TypesIncoming Types

1. Cable 1. Top

2. Bus duct 2. Bottom

1‐ Cable‐Bottom

2‐ Cable ‐Top

3‐ Bus duct‐Top

4‐ Bus duct‐Bottom