Product category : Isolating or insulating components & devices

Stelmac offers isolators. The disconnectors / isolators are used for electrical isolation of a system / equipment for maintenance. These disconnectors can be used to switch off unloaded lines or transformers and are provided with earth blades to keep the equipment earthed, thus rendering it safe to work on.

Construction
The disconnectors have a sturdy construction to ensure trouble–free performance. Current carrying parts are made of electrolytic copper / aluminium. Contacts are made of electrolytic copper, duly silver-plated. Hot dip galvanized or painted structures are also made in-house and are supplied alongwith the disconnector.
Solid core porcelain insulators with required cantilever strength and creepage can be supplied along with the disconnectors.

Design
Stelmec disconnectors are designed to provide maintenance free and reliable long life operation. These conform to is:921 / iec 129 and iec 694 and are fully type tested at cpri / erda.

Types
Center break type "hc"
Double break type "hd"
Pantograph type "pg"

Ratings
Rated voltage - 72.5 kv, 145 kv, 245 kv, 420 kv
Rated current - 630 a, 800 a, 1250 a,1600 a, 2500 a, 3150 a
Rated short time current - 72.5 kv, 25 ka / 3 sec.
145 kv, 40 ka / 3 sec.
245 kv, 40 ka / 3 sec.
420 kv, 40 ka / 3 sec.

Operating mechanism
Operating mechanisms available are as follows :
Motorised operating mechanism
Manual operating mechanism with reduction gear
Manual operating mechanism without a reduction gear but with a lever operating handle.
The mechanism is provided with requisite auxiliary contacts for signalling and interlocking the associated circuit breaker.

Interlocks - safety feature
The disconnectors / isolators are provided with a number of interlocks to ensure safety of operating personnel as well as of the equipments.

1. Standard interlocks
Operating mechanism for the disconnector is provided with padlocking facility, to prevent operating by unauthorized people.
When a disconnector is provided with an earth switch, the two are mechanically interlocked to ensure that;
- disconnector cannot be operated unless the earth switch is in an open position
- earth switch cannot be operated unless the disconnector is in an open position
Motorised operating mechanism, when provided, is equipped with a manual operating facility

An interlock ensures that :
- manual operating handle cannot be inserted when motor is connected
- motor cannot be connected when manual operating handle is inserted

2. Optional interlocks
Electrical [solenoid] interlock on the disconnector to enable its interlocking with the earth switch / other equipments.
Electrical [solenoid] interlock on the earth switch to enable its interlocking with the disconnector / other equipments.

Quality assurance
Every component of the disconnector passes through a stringent quality check system, supervised by qualified and skilled personnel, to ensure the supply of quality product.