ISOLATOR

Standards Referred

IEC 62271-102 (High Voltage Switch gear and control

gear)

IEC 61128 (Alternating current disconnectors – Bus-

transfer current switching by disconnectors)

IEC 60060-1 (High-voltage test techniques)

IS: 9921 (Alternating current disconnectors)

IEC 60694 (Common Specifications For High-Voltage

Switchgear and Controlgear Standards)

Purpose of Isolators

Used to isolate the circuit under no load

conditions.

Used for isolation of networks for small

switching currents (<0.5 A) and also for

commutation currents.

Cannot be used to make or break the

circuit.

It is used in addition to Circuit Breakers.

Types of Isolators

Horizontal centre Break isolator (Two column Rotary Disconnector) (72.5KV – 765 KV)

Horizontal Double break Isolator( Three column rotary Disconnector) (12 KV – 765 KV)

Vertical Break Isolator( Two column Vertical Break Disconnector) (<25KV)

Knee Type Isolator (33KV – 765KV)Pantograph Isolator( Single column

Disconnector)(145KV – 765KV)

Horizontal centre break Isolator

Horizontal Double break Isolator

Vertical Break Disconnector

Knee Type

Pantograph Insulator

Operating Mechanism

Motor Operating MechanismSpur Gear followed by Worm Gear is installed for smooth operation and self locking

Manual with Gear MechanismHand operation with Worm Gear is used for self locking capability

Manual OperationHand operation using lever is

practiced

Spur Gear Worm Gear

Earth Switch

Connected between line conductor and

earth.

Usually mounted on frame of isolator.

Interlocked mechanically and electrically

with isolators

Single Coloumn Earth Switch

TerminologyParticulars Data for 400

KV

Rated Current under site conditions at 50ºC ambient

2000/3150Amp.

Rated Short Circuit current of Isolator and E/S for 1 sec.

50KA(rms)

Rated dynamic short circuit withstand current of Isolator and E/S.

125 KA(peak)

Rated Mechanical terminal Load

Dielectric Withstand Capacity 520 KVrms

One min. power freq. withstand voltagei. Against Groundii. Against Isolating Distance

520KVrms610KVrms

1.2/50 µsec. Impulse withstand voltagei. Against Groundii. Against Isolating Distance

1425KV(peak)1450(+240)KV(peak)

Corona Extinction Voltage 320 KVrms

Operating Time Less than 12 Sec.