Transformer P28 Compliance

Ensuring P28 compliance for an 11kV cast resin transformer.

Transformer P28 Compliance

The Problem in Detail

Our customer used an 11kV cast resin transformer to power their testing facility. They were experiencing issues when energising the test transformer, sometimes the inrush current and voltage dip would trip the site out completely. They were also concerned about P28 compliance issues.

Transformer P28 Compliance
shunt reactor switching

Finding the Solution

We proposed applying Point-on-Wave switching to the sites existing 11kV 3-pole breaker to solve the sites transformer P28 compliance issues. The SynchroTeq will calculate the residual flux when the transformer is de-energised and control the exact angle of re-energisation to avoid saturation and inrush current.

Transformer P28 Compliance
shunt reactor switching

Making it all Work

Enspec power offered a turnkey solution, carrying out the full supply, installation and commissioning. The install was a retrofit as the site had been in operation for a number of years, we assisted with the wiring diagram modifications and carried out all on-site integration wiring.

Transformer P28 Compliance
reactive power compensation

What that means for the project now

After the successful installation and commissioning the transformer inrush current was reduced from a peak of over 1000A to a maximum of 112A, a more than 8 fold reduction. There was also a notable improvement in light flicker when the transformer was energised, this was significant prior to the install.

Transformer P28 Compliance

What GE say...

"After commissioning our new HVDC Valve Test Facility in Stafford we became aware that of one of our cast resin supply transformers was seeing repeated energisations at high levels of inrush current. After looking at several other solutions to mitigate the inrush (11kV Pre Insertion resistor bank, LV switchgear on the transformer secondary) we came across Enspec's Point-on-Wave switching solution for ganged pole breakers.

Enspec's approach from the outset was inspiring. They returned a binding quote with 3 days of our initial inquiry and showed diligence and professionalism throughout our contractor qualification process. Once awarded the job, they then produced, installed and commissioned a quality, cost effective solution, safely and within the agreed timeframe and budget. It was simply a pleasure working with them.

Since the installation of the SynchroTeq MV relay, thus far we have seen an 8 fold reduction in our average peak inrush levels ensuring our facility operates within the ER P28 recommendations and our cast resin supply transformer is protected from the mechanical shock loading associated with high inrush levels." Greg Bennett, GE’s Grid Solutions, HVDC

Find out more about Point-on-Wave switching here.