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MV Switchgear

HV Power represents quality Siemens MV switchgear in New Zealand . Our team has experienced project management staff, commissioning engineers, protection engineers and factory trained staff to ensure our customers get the best solution.

Vacuum Interrupter

Many of these Siemens products are based upon their “vacuum interrupter”, a technology available from, and continuously developed by, Siemens for some 30 years. Siemens vacuum interrupters use chrome-copper contact material, which minimises chopping current and thereby keeps overvoltage to a minimum. In some designs radial magnetic field contacts are used to force high current (>10kA) arcs to rotate rapidly around the contact surfaces to reduce contact erosion, and in others axial magnetic field contacts are used, which force the arc to remain diffused, thus preventing excess contact erosion.

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Indoor Switchgear

Ring Main Units (11 & 22 kV)

8DJH Ring Main Unit

This compact switchgear offers a wide variety of modular choices. Designs can include, ring switches, transformer feeders using fuses or circuit breakers, cable feeders, bus sectionalisers and revenue metering panels. Your specific needs can be accommodated by specifying the modules and arrangement required.

Front panel locking is intuitive and fool proof – meeting the specific needs of the NZ distribution companies’ standard practices.

The Ring Main Unit is Siemens “8DJH” series of switchgear, which features low pressure, sealed-for-life tanks, to eliminate the need for maintenance and gas handling. The 8DJH can be specified with combined or separate tanks per panel and extensible capability where bus extension and addition of further modules may be needed in the future.

Further options are available for the 8DJH series including motorised operation of disconnectors and spring recharge, auxiliary switches for remote indication, surge protection, VT & CT options and a range of protection, indication and fault passage indicators.

With an optional LV compartment, advanced capability numerical relays can be installed, and the 8DJH series can be utilised for 11 kV switchboard applications (630 A rated).

HV Power Siemens 8DJH Ring Main Unit brochure

More information on 8DJH switchgear (Siemens web page).

The 8DJH Ring Main Unit is also available with outdoor enclosure options to suit your needs (see Outdoor section below).


Switchboard Components – Vacuum Contactors & Circuit Breakers

MV devices

A range of vacuum circuit breakers are available from Siemens for your own special requirements such as new or retrofit of industrial panels, motor controls, filters and furnaces. See also here.


Outdoor Switchgear

Ring Main Units (11 & 22 kV)

Bosecker outdoor enclosure for RMU

The 8DJH series of Ring Main Units are available with a variety of enclosures to enable the units to be used in outdoor applications. Refer to our above 'indoor' 8DJH section for information on the Ring Main Unit itself.

We supply three types of Type Tested enclosures for use with Siemens 8DJH series Ring Main Unit:

  • Class A [IAC A (authorised personnel) Front, Lateral and Rear]
  • Class B - Boescker [IAC B (unrestricted accessibility including public) Front, Lateral and Rear]
  • Class B - Flat pad [IAC B (unrestricted accessibility including public) Front, Lateral and Rear]

The enclosures are internal arc classified to IEC 62271-202. IAC B specification is critical for all network switching assets accessible to the public –especially where switching is untaken remotely or autonomously.

Download our:

HV Power Siemens 8DJH Ring Main Unit brochure

Class B Bosecker data sheet

Class B flat pad data sheet

More information on 8DJH switchgear (Siemens web page).


Reclosers (11, 22 & 33 kV)

3AD Vacuum recloser

Single and three pole outdoor reclosers with voltage ratings for 11 kV, 22 kV and 33 kV distribution systems are available from HV Power. The vacuum-only devices provide high performance and long life.

The Recloser head unit is electromechanical, containing no electronic devices. This eliminates the need for pole top replacements in later service due to failed electronics.

The controller is based on the Siemens (Reyrolle) ARGUS-M 7SR224 directional overcurrent protection relay, but with added features to suit the specific needs of protecting long rural lines such as differentiation of low-fault currents to overload situations, and thermal protection of lines. Although highly reliable, the controller is field removable, allowing line staff to hot-swap out the device if required, such as to apply new settings, without the need to have technical staff at site.

More info on 3AD


Outdoor Vacuum Circuit Breakers (11, 22 & 33 kV)

3AF Outdoor Circuit Breaker

Siemens Outdoor Vacuum Circuit Breakers are specifically designed to have a minimum of moving parts and a simple design in order to guarantee a long electrical and mechanical service life. The 3AG & 3AF series of live-tank circuit-breakers, use Siemens vacuum interrupters, but housed inside a porcelain pole column.

The 3AF0 and 3AG0 are restrike-free and offer reliable operation through their stored-energy spring operating mechanism. They are easy to install, operate, and maintain. Due to their modular structure and lightweight components, these Siemens live-tank circuit-breakers can easily be transported to their installation site. They can be optimally adapted to each application using current and voltage transformers mounted on the CB stand.

More info on 3AF


Disconnectors, Switch-disconnectors, Earthing switches & fuses

Air Break Disconnector

Siemens now offer a range of outdoor pole mounted load break switchgear for distribution applications.

See this Siemens webpage for details on:

  • Line Tension Disconnects
  • Bypass Switches
  • Distribution Class Disconnects
  • Topper – Group Operated Switches
  • Vector – Manual and Motor Group Operated Switches

Instrument Transformers

Instrument Transformers

Instrument transformers are a prerequisite for measuring high voltages or currents. Their task is to transform them into small current or voltage values for measurement or protection purposes. Instrumentation transformers can be equipped with several secondary windings with magnetically separated cores of the same or different characteristics, e.g., for measuring and protection purposes. Single-pole insulated voltage transformers can be provided with an additional winding for earth-fault detection.

More info on Instrument Transformers


Outdoor Step Voltage Line Regulators

Outdoor Line Regulators

As far back as 1933 Siemens, through its predecessor – Allis Chalmers – originated the 5-8% step voltage regulator. Today Siemens has the largest population of installed voltage regulators in the United States and worldwide.

While the range includes JFR single phase regulators, Siemens also produce the SFR three phase ground mounted regulators, which are used by several New Zealand lines companies where single phase regulators are unsuitable.

More info on JFR single phase regulators


Guide to Siemens Part Numbers

3AD   Pole Top Vacuum Recloser 11, 22 & 33 kV
3AF   22-33 kV Outdoor Circuit Breakers
3AG   11 kV Outdoor Circuit Breakers
8DJH   Indoor and outdoor Ring Main Units 11 - 22 kV
JFR & SFR  Line Regulators (Distribution Voltage Regulators)