The Damaging Effects of Unbalanced Voltage Supply

Interview conducted by Jake WilkinsonJan 6 2016

 

ABB are global leaders in power technologies. AZoM spoke to Holger Hannemann, of ABB's Power Conditioning business, about the myriad of complications an unbalanced voltage supply can cause in industrial settings and the best ways to resolve them.

Could you provide our readers with an overview of the history of ABB’s power conditioning division and tell our readers about your most recent projects?

It started in 1995 with the idea of power electronics based products to protect industrial applications from power quality problems. Voltage sags or dips were identified as the problem with the highest financial impact on operations. In 1997 we successfully commissioned our first active voltage conditioner on a facility producing PET drinking bottles.

Together with our customers we developed a range of products and solutions to protect sensitive equipment from external supply problems and problems created by their own operations.

Depending on the customer’s protection philosophy and technical infrastructure, we offer industrial UPS systems at low and medium voltage levels, static frequency converters, reactive power conditioners and voltage conditioners. In 2014 we launched a Medium Voltage UPS and one year on, we have delivered units to a number of sites.

This year we gave our voltage conditioner a face lift. The PCS100 AVC-40 and most recently the PCS100 AVC-20, a new voltage regulator product targeting markets with generation issues, where the voltage is out of the tolerance band for long durations.  Since 1997 we have installed thousands of units with over 1000 MVA worldwide.

What are the main causes of an unbalanced voltage supply?

In most cases an unbalanced loading of the three phases causes voltage imbalance. These could be single or two phase loads that are not equally split over all phases, for example boilers, heaters, air conditioning, welding and single phase power supplies for computers or servers etc.

What issues can an unbalanced voltage supply cause for commercial and industrial companies?

The problems typically arise on connected three phase loads like motors, drives and rectifiers. The loads will draw the same amount of power but due to unbalanced voltage this will effect current wave forms causing increased stress on all of the components.

With motors you can hear it by an increase in noise and see it as torque and speed issues plus an extreme temperature rise. Voltage imbalance has a hugely negative impact on the life expectancy of motors and power electronics.

Let’s take an example; a 5% voltage imbalance results in a motor temperature increase of 50%! But every 10 degree temperature rise halves the life expectancy of the motor insulation. So operating a motor with 5% voltage imbalance means this machine will reach less than 5% -10% of its typical age.

ABB have just released a new voltage-regulating product, the AVC-20, where do you see this being used? Are there any specific markets that you are targeting?

The AVC-20 is targeting long duration voltage regulation problems, so called brown outs. The voltage deviates on one or more phases from nominal values, for minutes or even hours. Often it is a result of local generation capacity issues and can be seen in developing countries where the power supply can’t cope with the increased demand.

Typical areas are the Middle East, Africa or India where the supply voltage may be lowered by 10-20 % for many hours.

How does the AVC-20 correct an unbalanced voltage supply?

The AVC-20 uses the same topology as our AVC-40. We measure the supply voltage and correct voltage magnitude and phase angle problems on the load side of the device. While the AVC-40 dealt with very deep voltage dips for a short period of time (seconds), the AVC-20 can correct around +/-20 % of voltage deviation without any time limit.

Conventionally how have businesses resolved the complications of a fluctuating voltage? What advantages does the AVC-20 have over these methods?

In most cases it has been up to the business to deal with the problem. Typical solutions are a tap change transformer (usually 1-2% voltage steps) or a servo regulated transformer to adapt / correct the voltage.  They are physically big, introduce losses of another 3-5% and have a slow response time.

The AVC-20 is typically half the size and losses and are much faster in resolving the problem. After 20 milliseconds the voltage and phase angle problems are corrected and this is fast enough to protect assets and operations from tripping.

As the world becomes more developed and industrialised do you believe unreliable electricity sources will become a more prominent issue?

Utilities especially in developed countries do a very good job in offering a stable and uninterrupted power supply, but unfortunately they cannot protect from every scenario. Overhead lines are exposed to weather events, therefore exposed to lightning or trees touching a line.

Other customers connected to the same distribution can also introduce problems that are caused at their end. While we barely see power outages, we have voltage events everywhere in the world, so there is a growing demand in power protection.

Do ABB have plans to develop similar equipment in the future? What are the difficult problems in power regulation that you would like to solve?

We are always working on new solutions and currently have a lot of ideas and desires to implement these. A tendency that we often see is “bigger is better”, system sizes are growing and there is a demand for a complete power protection solution at higher voltage levels. These solutions are expected to offer a smaller footprint and higher efficiencies to lower operational expenses.

We are working on our next generation of power electronics which will be the base for new products to address our customers’ needs.

About Holger Hannemann

Holger studied electrical engineering at the Technical University in Chemnitz, Germany and the Novosibirsk Electro Technical Institute (NETI), Russia with a focus on power electronics and process control.

He worked for 19 years in Europe with low and medium voltage drive systems before moving to New Zealand where he joined ABB’s Power Conditioning business in Napier.

Here he was Product manager for grid connection and drove the development and market introduction of inverter systems for Energy Storage Systems (ESS) and STATCOMs. Since 2011, Holger manages the worldwide sales for ABB’s power conditioning products.