Three new MV and HV switches

Next generation MV metal-clad

Siemens’ US arm has introduced its next generation medium voltage air insulated switchgear product for the US market, the GM-SG. Based on the well-known GM switchgear design, the GM-SG now incorporates the well proven 3AH3 vacuum circuit breaker. The original 3AH design, which originated in Germany, is used in eight circuit breaker and switchgear products around the world. It enables the GM-SG to provide significantly higher performance including faster interrupting times and higher interrupting currents. Over 160 000 3AH breakers have been sold worldwide since its launch in 1998.

The GM-SG will initially be offered at 5 kV and 15 kV, with rated currents up to 3000 A self-cooled, and interrupting currents up to 50 kA with 3-cycle interruption. Deliveries start in early 2007. This will be followed by a two-high arc-resistant version as well as a 63 kA interrupting rating later in 2007.

The 3AH3 will be the common circuit breaker for all Siemens ANSI medium voltage switchgear/circuit breaker products, including the GM-38kV, the SDV6 distribution circuit breaker and the retrofit breaker. “By standardising on the 3AH3, we are able to offer a range of superior switchgear products while being able to meet customers’ demands for quality and life cycle costs,” says Doug Keith, vice president of the Distribution Products Division. The 3AH3 is claimed to double the life and number of available operations when compared with the current GMI breaker.

The unit is to be manufactured at the company’s switchgear factory in Queretaro, Mexico, where Siemens has made a considerable investment to manufacture the GM-SG including new plant equipment, manufacturing and quality processes. Customer services and marketing, project management and design engineering will continue at the Wendell, North Carolina, facility.

Compact switchgear.

The new 3AP1 DTC (dead tank compact) compact switchgear is rated at 145 kV and provides the functions of outdoor switchgear, consisting of circuit-breaker, disconnecting and earthing switches, as well as that of a current transformer. The special feature of the compact switchgear is its modular design: it is made up of components of high-voltage products that have proven themselves worldwide, including the following:

• The self-compression arc-quenching interrupter unit and the spring drive mechanism of the 3AP high voltage circuit-breaker

• The gas-insulated disconnector/earthing switch as well as the motor drive of the 8DN8 series gas-insulated switchgear

• The outdoor earthing switch from Siemens’ range of disconnecting and earthing switches

In this way, various models of switches can be put together – depending on the requirements – with a minimum of engineering effort.

72.5 kV switchgear

A new 72.5 kV unit expands Siemens’ range of GIS to include a compact modular type. The switchgear assembly has been optimised to meet the technical and economic requirements of this market, resulting in a switchgear assembly for breaking currents of 31.5 kA and rated currents up to 2500 A with dimensions up to 30% smaller than the 145 kV variant. Proven components and modular installation principles for indoor and outdoor installation have been retained for arc extinction and drive systems and in the design of the switchgear itself.