US 72,5 - 123 kV - outdoor earthing switches


Earthing switches are used to earth the disconnected sections of substations. The earthing switches are devices to be installed outdoors. They can be supplied as a single-column stand-alone devices used for grounding or as the earthing switches mounted on the base of the ONE type disconnectors. Universal design of the earthing switches US type also allows you to mount them to the disconnectors located on the a substation.


Carrying element of the earthing switch is the supporting base, which through the mounting plate the post insulator is attached. It maintains the main contact of the earthing switch and high-voltage terminals, suitable for flat or bolt connections (optional). The earthing switch’s arm is permanently connected to the grounded frame by flexible connection. In the open position of the earthing switch’s blade is positioned along the support frame. All components are protected against atmospheric conditions: the steel parts that could corrode are hot galvanized.


The earthing switch may be driven individually or in a set of three of the earthing switches. The construction of the drive pull rods are formed such that a dead point is achieved before the mechanism achives the end position. This prevents accidental opening or closing of the device (eg. during the vibration caused by the earthquake, short circuits, etc.).

The energy required to close the earthing switch is transmitted to the shaft of the earthing switch through the string, causing the contacts of earthing switch going up. In the closed position the contact’s fingers rest with initial tension on the limiter.


Three-pole earthing switch needs one drive - manual or motor. The drive is fixed to the supporting structure to which it is mounted the earthing switch. For higher installed units, it is possible to mount the drive with the relevant driving shaft so as to be accessible from the ground level.


The drive motor can be locked electrically. The drive motor can be locked electrically. If necessary, the drive can be equipped with a locking solenoid that prevents any operation of manual drive or contingency start of the motor drive without a signal from the control room. This enables central supervision over all the manual operations of the earthing switches in the whole substation.


Due to the careful selection of materials and constant lubrication the earthing switches practically do not need conservation. Inspections are mainly limited to the check of elements exposed to the influence of the atmosphere. Under normal climatic conditions the inspection is performed once every 5 years.

Compliance with the standards:

The earthing switches type US comply with the the standards IEC 62271-102; IEC 60694 and most other national standards. Devices are available for voltages from 72.5 kV up to 123 kV.

Technical data:






rated operating voltage

72,5 kV

123 kV


peak current

125 kA

125 kA


short-circuit current (1 sec.)

31,5 kA

31,5 kA


test voltage for insulation of 50 Hz

140 kV

230 kV


mechanical durability

2000 cycles

2000 cycles



76 kg

100 kg


drive: manual | motor

NSO 110 | NRO 110

NSO 110 | NRO 110


Dimensions of manual drive to US earthing switch
Dimensions of earthing switch US

All technical data presented in the catalog can be changed due to technological progress.



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