Medium Voltage Secondary Switchboard AIS SF6 Ring Main Unit

HMH Series Metal Enclosed Modular Switchgears :

These are the medium voltage switchgears designed for use in secondary distribution systems up to 40,5kV, in compact kiosk type transformer substations, in industrial facilities and indoor spaces.

All functional units which may be required in a switching and distribution centre can be easily installed side by side.

Switchgears which are produced in the factory with all routine and type tests conducted, can be commissioned in a very short period – practically and safely.

Isolating and breaking processes are carried out in SF6 gas environment and the busbars compartment in air.

Thanks to this, a safe isolating and breaking process is ensured and dimensions have been minimized.

HMH Series Modular Switchgears, can be easily and safely used in package type transformer stations due to their compact dimensions.


Manufactured in accordance with IEC 62271 – 200, 60265, 60129, 60694, 62271 – 100,
62271 – 102, 62271 – 105 standards.
Below are the switchgear types and definitions which are frequently used in secondary
distribution systems or industrial facilities.

– HMH Series 01 Incoming-Outgoing with LBS
– HMH Series 02 Transformer Protection Fuse-Switch Combination
– HMH Series 03 Voltage Transformer (Voltage Metering)
– HMH Series 04 Incoming-Outgoing with Circuit Breaker
– HMH Series 05 Bus Coupling
– HMH Series 06 Incoming-Outgoing with Switch Disconnector
– HMH Series 07 Cable Connection
– HMH Series 08 Current & Voltage Metering with LBS
– HMH Series 09 Bus Riser
– HMH Series 10 Current Metering + Bus Riser
– HMH Series 11 Current Metering
– HMH Series 12 Bus Riser with Breaker (side exit)
Please contact us in case you have specific requirements.


HMH Series Switchgears are designed under complete modular structure, in consideration
of functionality, appearance and security features. Switchgear carcasses are manufactured
of 2mm hot dip galvanized sheet metal and with its
galvanize thickness of 275gr/m² which is above the industry standards, it is not subject to
any deformation even under the dampest mediums.


All type tests of HMH Series Metal Encased Modular Switchgears are successfully performed in international independent and accredited laboratories in compliance with the IEC standards: 60298, 60265, 60129, 62271-1, 62271-100, 62271-200 and 62271-105

SF6 Ring Main Unit passed all necessary tests carried out in The Egyptian Electricity Authority Pyramids High Voltage Research Center and approved from The Egyptian Electricity Holding Company.

Basic Interlocking Systems:

* LBS can be closed only when the door is closed and earthing switch is open.
* Earthing Switch can be closed when the LBS is open.
* Switchgear door can be opened when the earthing switch is closed.
* LBS cannot be closed when the switchgear door is open.


Rated Voltage 24KV
Rated network frequency withstand voltage (1 min)50KV
Between isolating distance (open position between the contacts) 60KV
Rated lightning impulse withstand voltage125KV
Between isolating distance (open position between the contacts) 110KV
Nominal frequency 50-60HZ
Nominal current630-1250A
Nominal peak short circuit current40-63KA
Nominal short circuit current (1s) (3s)16-20-25KA
Nominal closed circuit breaking current630A
Nominal no load cable breaking current630A
Nominal no load line breaking current16A
Nominal idle cable breaking current1.5A
Nominal earthing fault current10A
Line and cable breaking current in case of an earth fault 10A
Nominal transfer current630A
Nominal short circuit closing current40KA-peak
Mechanical ClassM1-E3
Protection ClassIP3X
Internal Arc ClassAFL
Accessibility ClassLSC2A-PI
Fuses (Compliant with IEC 60282-1)24KV
Impact pin forcemiddle
Earthing Switch (ESH 36-01)24KV
Nominal short circuit breaking current (1s) (load factor) 16-20-25KA
Nominal short circuit closing current40-63KApeak
Earthing switch (ESH 36-02) 24KV
Nominal short circuit breaking current (1s) 1KA
Nominal short circuit closing current 2.5KA