Rethinking Pole Top Voltage Regulators

A few years ago Ergo was involved in the design of pole top 2 x voltage regulator (VR) installations on the Piha and Tomarata 11kV feeders using Siemens single phase voltage regulators. These have since become the Vector standard design template for 2 x VR installations. They have a 3 phase Air Break Switch (ABS) or automated recloser as a bypass switch and drop out links for isolation, as well as a separate pole mounted comms panel for control and monitoring of the VR’s via the GPRS network. Auxiliary power is provided by a resin cast phase to phase voltage transformer.

As a result of this experience, Vector asked us to provide primary, secondary and civil/structural design for a unique pole top 3 x VR installation at the Vector/Counties power network border in Kawakawa Bay. The design required a total rethink of the way pole top voltage regulators are installed, due to a recent change in Auckland Council regulations which limit the quantity of oil in a single installation to 1000 litres.

We resolved this issue by spreading the 3 x VRs across three separate poles and using single phase omnirupter ABS’s and drop out fuses. The three-pole installation is controlled and monitored by a single comms panel mounted on the 1st pole, with comms connected via aerial fibre optic cable to the 2nd and 3rd pole. In this case auxiliary power is provided from an adjacent pole top distribution transformer via Aerial Bundled Cable (ABC).

The installation was modelled in 3D to demonstrate that it would perform as expected and provide all safety clearances. This model was also used, in co-ordination with PLC Electropar, to modify the design for the ABS.  The civil design also had its challenges due to the soil type at Kawakawa Bay. This was resolved by using longer poles and drilling down to the bedrock layer.

This three-pole design will become the new Vector template for this type on installation.  The final design will provide alternative connections to reinstate the site as a 2 x VR installation in the event of a vehicle colliding into one of the poles.

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