Displaying items by tag: CP Automation

Friday, 15 July 2022 11:02

Power quality in remote locations

When they are based in remote locations, transformers and other power equipment are vulnerable to harmonics and noise caused by insufficient dampening and exposure to surrounding electrical currents. If these issues aren’t addressed, they can cause component failure and severe damage to the local power supply. When Fairfields Control Systems, a systems integrator specialising in unique control and automation systems, experienced failures at two recently-upgraded sites, it approached power quality specialist CP Automation for a solution.

Fairfields Control Systems provides turnkey mechanical, electrical, instrumentation, control and automation (MEICA) solutions for a range of industries including flood defence and factory automation.

Transformer in actionTransformer in actionAs a contractor for the Environment Agency (EA), Fairfields had recently upgraded the borehole pumps on seven of its groundwater sites in the UK with variable speed drives that were fed from transformers. Each transformer helped to power a pumping station, that are used to alleviate low river flows.

Transformers and harmonics

Transformers are common in many industrial settings, reducing the voltage of conventional power circuits to operate low-voltage devices. They can also be used in remote locations to transmit power to more isolated sites. When situated in more remote outdoor locations, transformers are generally smaller and installed high-up on concrete or wooden poles or platforms.

Fairfields had recently upgraded the borehole pumps at seven of the EA’s sites. But, soon after the upgrade, the surge protection devices (SPD) 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 is 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. It was also important that Fairfields resolve the issue to stay compliant with the Engineering Recommendation G5/4, which specify the planning levels for harmonic voltage distortion.

Revcom passive flitersRevcom passive filtersTurning a corner

Fairfields already had a relationship with CP Automation, as the company had carried out various surveys and consulted on different projects in the past.

“CP Automation’s power quality expertise has been crucial for protecting our systems,” explained Peter McMorrow, engineering director at Fairfields Control Systems. “The ground water project was different. While we can often foresee issues with noise and power quality, in this case, we were already experiencing issues. Once they were identified, our priorities were to determine the source of the abnormal supply and its characteristics. Our plan was to retrofit equipment to mitigate the effects.

“The total harmonic distortion (THDi) was falling outside its normal rage and the voltage was becoming unstable, so long-term damage to the transformer and its components was a real risk,” explained John Mitchell, global business development manager at CP Automation. “After surveying the situation, we suggested replacing the failed SPDs with two SineTamer transient voltage surge suppression (TVSS) devices, which protect from surges and transient spikes.”

After proving that the SineTamer could function effectively in the high harmonic environments where the original SPDs failed, CP Automation agreed to fit the new devices across all the EA sites. Meanwhile, it supplied two REVCON Harmonic Filters (RHF) for the high-harmonic sites to help protect the transformer and other nearby equipment. The RHFs prevent the harmonic distortion of nonlinear loads and sources, reducing the THDi to below five per cent, which is essential for staying within G5/4 levels.

A stable power supply

Fairfields purchased two RHF-5P double stage passive filters. As well as reducing the THDi of variable frequency drives (VFD) and other non-linear loads, the filters can reach an efficiency of up to 99.5 per cent. As a result, power losses are up to 75 per cent less than those produced by alternative devices.

Ever since Fairfields installed SineTamer and the RHFs, the transformers have been running as normal across the EA’s ground water sites. By minimising voltage distortions, the technologies supplied by CP Automation have prevented issues like voltage notching, motor vibration, nuisance tripping, electromagnetic interference (EMI) and overheating. Furthermore, the sites are now compliant with G5/4 standards, because the RHFs limit frequency voltage harmonics.

To find out more about how to mitigate harmonics by visiting the CP Automation website.

About CP Automation: CP Automation is a specialist in the repair and replacement of automation equipment including electronic boards, PLCs and Ac and DC drives. It was established to provide an independent maintenance service, without exclusive ties to any manufacturer. However, it does have strong relationships with the principal inverter, encoder, resistors and motor manufacturers.

Published in Power & water
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Friday, 25 February 2022 12:20

Choosing the right harmonic filter

The range and complexity of electrical and electronic equipment used in manufacturing environments has increased dramatically over the last few years. Here, John Mitchell, global business development manager of supply, repair and field service specialist CP Automation explains how to manage the increasing harmonic levels in the modern industrial landscape.

The introduction of variable speed drives, fluorescent lighting and transformers has brought a rise in the number of non-linear loads. One of the unwanted consequences of non-linear loads is the creation of harmonic currents, which can cause voltage distortion and quality problems.

To address the issues caused by high harmonics levels, including motor vibration, voltage notching, electromagnetic interference and overheating, companies can use harmonic filters.

Active or passive?

When choosing a harmonic filter, the first thing to consider is whether you need a passive or an active one. The traditional choice is a passive filter, used to minimise power quality problems in the network. These filters operate mainly on a fixed basis and are tuned to a harmonic order close to the order to be eliminated. One drawback of passive filters is that they are most efficient when the load is operating above 80 per cent and they cannot adapt the amount of compensation current they inject into the system.

On the other hand, active harmonic filters are the most flexible solution on the market. They monitor the network and inject the necessary amount of compensation current at any given time, which restores current waveform and lowers current consumption. This makes them ideal for installations in which current load changes constantly.

Regardless of what type of harmonic filter you decide to use, make sure it has the relevant UL certifications for the environment in which it is going to run. If unsure, you should always refer to an expert.

Another option is a mixed solution. You could use a passive filter on some applications and add a smaller active filter overall, which will help you save costs in the long run.

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Excess heat?

Another thing to consider when choosing a harmonic filter is that harmonic currents can induce additional heating in generators. Harmonics can also lead to heating of busbars, cables and equipment, cause thermal damage to induction motors and generators and thermal tripping of safety devices, like fuses or sensors in breakers. These relatively minor issues can have a negative effect on the entire system and can increase maintenance costs.

Luckily, some active filters produce up to a third less heat than competitor products due to the switching techniques of the insulated-gate bipolar transistors (IGBTs). Equally, the REVCON RHF Series of passive filters offer up to 99.5 per cent efficiency.

When comparing filters, active or passive, you should look closely at the total cost of ownership for the end user. After all, heat loss is a direct cost in energy bills. This is particularly important on the shop floor, in marine and offshore applications or any other environments where space and heat is particularly precious.

Before choosing a harmonic filter, it is important to assess the entire system and size the right solution for your specific needs. It is not enough to look at one troublesome application individually. Instead, you should have an accurate representation at the entire operation as a whole. Often what looks like the cause of a problem can actually be an effect.

CP Automation suggests performing a plant survey and collecting data over several days. After the initial analysis, we can recommend the most appropriate product and install it without significant disruptions.

Once the harmonic filter has been live for a few weeks, another survey is necessary to check if all problems have been resolved. This ensures the product is appropriate and it gives companies real peace of mind.

Unfortunately, harmonics are not going anywhere, so businesses can’t afford to just ignore them. Instead, the best solution is to tackle the problem head on and if you are unsure of anything, always consult an expert.

About CP Automation: CP Automation is a specialist in the repair and replacement of automation equipment including electronic boards, PLCs and Ac and DC drives. It was established to provide an independent maintenance service, without exclusive ties to any manufacturer. However, it does have strong relationships with the principal inverter, encoder, resistors and motor manufacturers.

Published in Technology News
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Monday, 23 August 2021 09:46

Active and passive harmonic mitigation

~ Filtering techniques to combat current harmonics~

The rise of non-linear loads in industrial environments over the last two decades has resulted in the growing problem of harmonic currents and utility-level voltage distortion. Facing a lack of awareness, the industry has struggled to implement effective mitigation techniques. Here, John Mitchell, global sales & marketing director at power quality specialist CP Automation explores active and passive filtering.

In industry, voltage distortion caused by current harmonics can wreak havoc on a plant. Damage can be serious, causing voltage notching, motor vibration, arcing, nuisance tripping, electromagnetic interference (EMI/RFI) and overheating. Thermal stress can cause components to wear out quicker and results in increased energy costs in the long term.

Recent decades have seen a rise in the use of non-linear loads such as transistor based variable speed drives (VSDs) and line commutated DC drive systems. The processes of high frequency switching and pulse width modulation (PWM) introduce unwanted multiples of the fundamental 50hz frequency in the form of harmonics.

Industry challenges
Various approaches have been used to combat harmonics over the years. This has led to many suppliers using setups which are not meant for harmonic mitigation, in complex configurations that often raise costs.

There is the added issue of meeting international requirements such as IEEE-519 which limits harmonic frequencies. Some form of filtering is subsequently recommended.

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Active vs passive
Active harmonic mitigation methods work by effectively cancelling out the harmonic disturbance by generating an opposing compensating current. Passive methods divert currents or block them completely using low or high impedance paths.

Passive and active solutions can be installed in series configurations or in parallel, or shunt, configurations. The methods work either in series or in parallel with a non-linear load respectively and can block or divert potentially harmful harmonic currents away from the power supply.

As series solutions operate in line with the load, units must be sized for the full current load. Shunt units are sized based on the harmonic disturbance. There are options available that offer shunt-active, series-active, shunt-passive and series-passive solutions.

Series-passive
A straightforward series-passive solution can be achieved using a line reactor. This is a three-phase choke placed in front of the rectifier. It can reduce current harmonics, while adding a level of protection to the rectifier. However, it's unsuitable for large drives and is unable to meet IEEE519 standards alone.

The next option is to use a series harmonic filter. It provides effective compensation, significantly reducing total harmonic distortion (THD). Although it works well as a "catch-all" it is grid sensitive and may lead to interaction. It's also not particularly suited to dynamic applications, working best on a well-balanced supply.

The last series-passive solution is multi-pulse — a multi-winding transformer with phase shift in the windings. Because every secondary winding has its own rectifier, an 18-pulse configuration can target and effectively cancel out the 18th, 19th, 35th and 37th harmonics.

The downside is that it's very sensitive to unbalance. At less than 100 per cent load, the current THD doubles from 8 per cent to 16 per cent. Units are also often large and difficult to retrofit.

Shunt-passive
Shunt passive is power factor correction, often using fixed capacitor banks, tuned and detuned contactor-based units, thyristor capacitor banks and fine-tuned passive filters.

An inherent weakness of passive solutions is the inability to control the load. The grid loading can cause several fine-tuned shunt filters to interact, resulting in resonance with other equipment.

Series-active
Series-active takes the form of an Active-Front-End (AFE) variable speed drive (VSD). It replaces the rectifier diodes in a regular VSD with an IGBT controlled rectifier to eliminate switching based signal noise and introduce regenerative braking.

Although this unit may at first seem to eliminate harmonics, this means twice the heat and with a 200kW AFE it soon adds up. For the panel builder or system integrator, bigger cooling systems are needed to cope with the excessive heat.

AFEs are great at significantly lowering THD and maintaining good power factor. However, to maintain a small form factor, lower switching frequencies are used, which result in high switch ripples on the voltage waveform. This can cause equipment to nuisance trip and malfunction.

Shunt-active
For shunt-active solutions, users may consider an active filter. It is particularly suited to VSD harmonics. It can cancel out harmonic frequencies by injecting equal and opposite, phase shifted, current frequencies.

Shunt active filters provide the most efficient harmonic compensation in a compact unit which has little loss, is insensitive to grid conditions, cannot be overloaded and is easy to retrofit. It is more costly but offers a better return on investment over the longer term.

Effective harmonic mitigation may seem intimidating, but it doesn't have to be. Understanding the differences between various techniques can yield better cost savings, reduce complexity and prolong equipment life.

About CP Automation: CP Automation is a specialist in the repair and replacement of automation equipment including electronic boards, PLCs and Ac and DC drives. It was established to provide an independent maintenance service, without exclusive ties to any manufacturer. However, it does have strong relationships with the principal inverter, encoder, resistors and motor manufacturers.

Published in Technology News
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