Electricity and Control September 2022

TRANSFORMERS, SUBSTATIONS + CABLES

Safeguarding power quality in remote locations When transformers and other power equipment are based in remote locations they are vulnerable to harmonics and noise caused by insufficient dampening and exposure to surrounding electrical currents. If these issues are not addressed, they can cause component failure and severe damage to the local power supply. In the case of a UK installation where Fairfields Control Systems had experienced failures of equipment at two of several remote groundwater sites recently upgraded for the Environment Agency, it approached power quality specialist CP Automation for a solution.

F airfields Control Systems is a systems integrator spe cialising in unique control and automation systems. It provides turnkey mechanical, electrical, instru mentation, control and automation (MEICA) solutions for a range of industries, including flood defence and factory automation. As a contractor for the Environment Agency (EA), Fairfields had recently upgraded the borehole pumps on seven of its groundwater sites, installing variable speed drives that were fed from transformers. Each transformer helped to power a pumping station, used to alleviate low river flows.

Transformers and harmonics Transformers are used in many industrial settings, reducing the voltage of incoming power supply circuits to operate low voltage devices. They are also used in remote locations to transmit power to more isolated sites. In such outdoor locations, transformers are generally smaller and often in stalled in an elevated position, high on concrete or wooden poles or platforms. Soon after the upgrade of the borehole pumps at the EA sites had been completed, the surge protection devices (SPDs) that limit transient voltages by diverting or limiting surge current began to fail on two of them. It was clear that abnormal supply characteristics were present, and that harmonic distortion levels were too high. Voltage distortion describes any deviation from the nominal sine waveform of the ac line voltage. It is caused when current harmonics increase the voltage and electric currents in a circuit and can overheat the power system, destabilise the voltage and damage equipment. Hence, Fairfields needed to resolve the issue effectively and it was also important that it should stay compliant with the (UK’s Energy Networks Association’s) Engineering Recommendation G5/4, which specifies the planning levels for harmonic voltage distortion. Overcoming the problem Fairfields had worked with CP Automation previously, as the company had carried out various surveys and had been consulted on different projects in the past. “CP Automation’s power quality expertise has been crucial for protecting our systems,” said Peter McMorrow, Engineering Director at Fairfields Control Systems. “The groundwater project was different. While we can often fore see issues with noise and power quality, in this case, we were already experiencing issues. Once we had identified these, our priorities were to determine the source of the abnormal supply and its characteristics. Our plan was to retrofit equipment to mitigate the effects.” John Mitchell, Global Business Development Manager at CP Automation, noted that, “The total harmonic distortion (THDi) was falling outside its normal range and the voltage was becoming unstable, so long-term damage to the trans former and its components was a real risk.

One of the transformers feeding power to the borehole pump system at an EA groundwater site.

24 Electricity + Control SEPTEMBER 2022