Category: Current Transformer

Rogowski Coils: Revolutionizing Current Measurement in Metering

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Rogowski Coils: Revolutionizing Current Measurement in Metering

Introduction

Rogowski coils, an innovative and versatile current sensing technology, have become a staple in the metering industry. These coils provide precise and reliable measurements of alternating current (AC) without the need for direct electrical contact. This article delves into what Rogowski coils are, their historical development, and their critical applications in the metering industry.

What are Rogowski Coils?

A Rogowski coil is an electrical device used to measure AC current. It consists of a helical coil of wire wound around a non-magnetic core, typically air or another non-magnetic material. The coil is wrapped around the conductor carrying the current to be measured. As the AC flows through the conductor, it generates a magnetic field that induces a voltage in the coil proportional to the current. This induced voltage can then be integrated to provide an accurate measurement of the current.

One of the key advantages of Rogowski coils is their ability to measure high currents without saturation, a common problem in traditional current transformers (CTs). Additionally, they offer a broad frequency response, making them suitable for various applications, from power distribution to industrial machinery monitoring.

A Brief History of Rogowski Coils

The Rogowski coil was named after the German scientist Walter Rogowski, who first described the principle in the early 20th century. Rogowski’s work laid the foundation for modern applications of this technology. The concept was further developed and refined by other scientists and engineers over the decades.

The initial use of Rogowski coils was limited to laboratory settings due to the complexity of integrating the voltage signal. However, advancements in electronics, particularly the development of precise integrator circuits in the latter half of the 20th century, enabled the widespread adoption of Rogowski coils in practical applications.

Applications in the Metering Industry

  1. Energy Metering: Rogowski coils are increasingly used in energy meters, particularly in commercial and industrial settings. Their ability to accurately measure high currents and their wide dynamic range make them ideal for monitoring power consumption and load profiles. This data is crucial for energy management and billing purposes.
  2. Power Quality Monitoring: Power quality is a significant concern for utilities and consumers alike. Rogowski coils are employed in power quality analyzers to detect and measure harmonics, transients, and other disturbances in the power system. This information helps in diagnosing issues and improving the overall reliability of the electrical grid.
  3. Protective Relaying: In protective relaying systems, which safeguard electrical circuits from faults and overloads, Rogowski coils provide reliable current measurements. Their fast response time and high accuracy ensure timely detection and isolation of faults, minimizing damage and maintaining system stability.
  4. Renewable Energy Systems: With the rise of renewable energy sources like solar and wind, accurate current measurement is essential for integrating these variable power sources into the grid. Rogowski coils are used in inverters and other equipment to monitor and control the flow of electricity from renewable sources.
  5. Electric Vehicle (EV) Chargers: As the adoption of electric vehicles grows, so does the need for efficient and safe EV charging infrastructure. Rogowski coils are utilized in EV chargers to monitor the charging current, ensuring safe and optimal operation.
  6. Testing Current Transformers: Rogowski coils are also extensively used in test equipment for verifying and calibrating current transformers (CTs) to help reduce lost revenue. Their non-intrusive nature and high accuracy make them ideal for this purpose. During testing, a Rogowski coil can be placed around the conductors under test to measure the current without the need to disconnect the system. This setup allows for real-time testing and validation of CT performance, ensuring accuracy and reliability in the field. The flexibility of Rogowski coils in accommodating various conductor sizes and shapes further enhances their utility in CT testing applications.

Conclusion

Rogowski coils have come a long way since their inception, evolving from a laboratory curiosity to a critical component in modern metering and power management systems. Their unique characteristics, such as non-saturation, wide frequency response, and high accuracy, make them indispensable in a variety of applications. As the demand for precise current measurement continues to grow, Rogowski coils will undoubtedly play an even more significant role in the future of the metering industry.

Understanding Current Sensors and Their Role in the Electric Utility Industry

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Understanding Current Sensors and Their Role in the Electric Utility Industry

What Are Current Sensors?

Current sensors are devices used to measure the amount of electric current flowing through a conductor. They are essential components in various electrical systems and play a critical role in monitoring and controlling electrical power. By converting the current flowing through a conductor into a readable signal, current sensors enable accurate measurement and analysis, which is vital for maintaining electrical safety and efficiency. These are similar to current transformers but operate a little bit differently.

Types of Current Sensors

There are several types of current sensors, each with unique characteristics and applications:

  1. Shunt Resistors: These are simple and cost-effective devices that measure current by detecting the voltage drop across a resistor placed in the current path.
  2. Hall Effect Sensors: These sensors use the Hall effect principle to measure current. They are known for their ability to measure both AC and DC currents and are widely used in various applications due to their accuracy and reliability.
  3. Rogowski Coils: These are flexible, non-intrusive sensors that are ideal for measuring AC currents, especially in applications where the conductor is large or difficult to access.
  4. Fluxgate Sensors: These sensors offer high accuracy and are used in applications requiring precise current measurement, such as in laboratory instruments and specialized industrial equipment.

Applications in the Electric Utility Industry

Current sensors are indispensable in the electric utility industry, providing numerous benefits and applications, including:

  1. Power Monitoring and Management: Current sensors enable utilities to monitor power flow in real-time, ensuring efficient distribution and minimizing losses. This monitoring helps in detecting and addressing issues such as overloads, faults, and inefficiencies. These sensors can be used in field equipment like capacitors and field reclosers.
  2. Transformer Monitoring: By measuring the current in transformers, utilities can assess their performance, detect anomalies, and schedule maintenance to prevent failures. This proactive approach extends the life of transformers and ensures reliable power delivery.
  3. Grid Protection: Current sensors are integral to protective relays used in the grid. They detect abnormal conditions, such as short circuits or overcurrents, and trigger protective devices to isolate the affected section, preventing widespread outages and damage.
  4. Energy Metering: In both residential and commercial settings, current sensors are used in smart meters to measure electricity consumption accurately. This data is crucial for billing purposes and helps consumers monitor their energy usage, promoting energy conservation.
  5. Fault Detection and Isolation: Current sensors help in pinpointing faults in the electrical network. By identifying the location and nature of the fault, utilities can quickly isolate and repair the affected section, minimizing downtime and improving service reliability.
  6. Integration with Renewable Energy: As the adoption of renewable energy sources grows, current sensors play a vital role in integrating these sources into the grid. They help in monitoring and managing the variable output from renewable sources, ensuring a stable and balanced power supply.

Conclusion

Current sensors are fundamental components in modern electrical systems, offering precise and reliable current measurement. Their applications in the electric utility industry are vast and critical, from power monitoring and grid protection to energy metering and fault detection. As the demand for efficient and sustainable energy solutions grows, the importance of current sensors will continue to rise, driving advancements in technology and further enhancing their role in the utility sector.

By understanding and leveraging the capabilities of current sensors and voltage sensors, utilities can improve their operations, enhance service reliability, and contribute to a more sustainable energy future.

Increasing Revenue with High Accuracy CT’s

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Increasing revenue is something that we all want to do. High accuracy CT’s can help us achieve that goal. When it comes to instrument rated metering installations we have to remember that our meter is only as accurate as our CT’s. So, the first step in making sure we are accurately measuring our metering installations is making sure we have the most accurate CT’s installed.

Standard Vs. High Accuracy

This is where high accuracy CT’s come into play. Remember that standard current transformers are only guaranteed accurate to within 0.3% from the nameplate value to the rating factor. Also, standard CT’s are 0.6% accurate from 10% of the nameplate value up to the nameplate value. This means that for a common 600:5 CT that anything below 60 amps is not guaranteed to be measured accurately. So, what do you do?

You install a high accuracy CT that is 0.15% accurate from 5% of its nameplate rating through the rating factor. Now, using the same 600:5 ratio as an example, we are now able to measure down to 30 amps with 0.15% accuracy. This is high accuracy CT’s are used to help with increasing revenue.

Where can high accuracy CT’s help with increasing revenue?

One of the places where high accuracy CT’s can help with increasing revenues are department stores or industrial factories that have been converted to warehouse space. These types of customer changes can cause revenue losses because the infrastructure that was put in for these larger customers who have now left or have converted their spaces is no longer being utilized.








Let’s say that the customer was doing some small scale manufacturing and decided that the space was no longer big enough for its manufacturing needs. So, they decide to move into a larger space and convert this previous space into warehousing. Let’s keep with the standard 600:5 for this example. For this example let’s also assume that the rating factor of this standard CT was three. We are also going to assume that we were using this rating factor. Meaning that this was a 1200 amp service and we installed 600:5 CT’s with a rating factor of 3, to make sure that the CT’s were as saturated as possible.

The customer in this example typically pulls around 750-800 amps. This is well within the range of our standard accuracy 600:5 CT’s. Now when they leave, they take all of the manufacturing equipment with them and only leave a few lights. There new load is now only around 40 amps. They do not need to heat or cool the space because what they are storing does not require it. So now, the standard 600:5 CT is not guaranteed to measure the 40 amps accurately.

What if we had installed a high accuracy CT?

If we had installed a high accuracy CT to begin with then we would not be worried. The high accuracy 600:5 CT is able to measure down to 30 amps with 0.15% accuracy. This means we capture those 40 amps and we do so accurately. This is how high accuracy CT’s play a vital role in increasing revenue.

Conclusion

In conclusion, if you are concerned with increasing revenue make sure that you are giving a look to high accuracy CT’s. They can be placed anywhere your standard accuracy CT’s are and can instantly start increasing revenue. High accuracy CT’s help mitigate low current situations such as when large customers move out or convert. If you are in the market for high accuracy CT’s check out Peak Demand.








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Reducing Inventory with High Accuracy CTs

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Reducing inventory is a big concern with utilities these days. This is primarily driven by the fact that reducing inventory means reduced costs. Reducing costs means that the profit margin can be higher. So, what does that have to do with high accuracy CT’s? How can high accuracy CT’s reduce inventory?

Use the Extended Range of High Accuracy CT’s

When placing new CT’s in service we traditionally had a variety of different CT ratios to choose from. Among the most popular are 200:5, 400:5 and 600:5 variants. This means that when a new service is built the meter tech or engineer will look at the service and size the CT’s according to the projected load. This is done because we want the amps on the service as close to the nameplate rating as possible. We do this because standard CT’s are most accurate at their nameplate rating up to their rating factor.

So, if we have a 400 amp service that is projected to normally run around half of that or less we may use 200:5 CT’s with a rating factor of at least two. This ensures that when the amperage is low we can measure it as accurately as possible.

Enter the new kid on the block. The high accuracy CT. With the high accuracy CT, with its extended range features we can now use one size CT for most of our installations. For instance a 600:5 high accuracy CT will allow us to measure down to 30 amps. But there is more. Many manufacturers are offering these high accuracy CT’s with extended ranges that can measure down even further.



How can High Accuracy CT’s be useful in Reducing Inventory?

High accuracy CT’s can reduce inventory by reducing the number of different ratios that you need. You can now purchase a 600:5 CT with a rating factor of 2 or more that can cover all your needs. This means that you no longer need to use 200:5 or 400:5 CT’s. You can stock one size. This allows you to purchase less. Even if you do not have a new job coming up, in the past you would have needed to keep a certain number of 200:5 and 400:5 CT’s on the shelf for emergencies.

So, instead of having a couple of sets of each size, you can have just a couple of sets of 600:5 CT’s that can be used for each service type. Instead of having purchased four sets of CT’s now you have only purchased two. This is beneficial to reducing inventory and cutting costs. Also, it leads to a reduction in storage space as well.

Conclusion

High accuracy CT’s can be a great way of reducing inventory in your meter shop or warehouse. Look at what you have stored in your warehouse and see if you could benefit from reducing the number of CT’s that are just sitting on the shelf as spares. If you are interested in high accuracy CT’s check out the offerings from Peak Demand.









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Extended Range CTs VS High Accuracy CTs

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Extended range CT’s are all the rage with CT sales people now. But what exactly is and extended range current transformer? Don’t we already have high accuracy CT options out there? Is there a difference in extended range current tranformers and high accuracy current tranformers? I will try and break these terms down and explain what the difference is between extended range CTs and high accuracy CTs.

What are Extended Range CTs?

To understand what extended range CTs are we need to understand what standard range CTs are. Standard range CTs have a measurement range from 0 amps through their rating factor. However, notice that I said measurement and not accuracy. That is because if we remember correctly that standard CTs are only certified as being accurate to 0.6% from 10% of their nameplate rating through the nameplate rating. Furthermore, at the nameplate rating up through the rating factor they are accurate to within 0.3%.

So, obviously an extended range CT would be better than that right? Well, yes. However, there is a caveat. That being that there is no standard when it comes to the term “extended range CT.” These extended ranges are noted in the literature that comes from the manufacturer of the CT. This means that the CT could be accurate down to 3% of the nameplate value or even down to 1%. This however all depends on the manufacturer. Which leads us to our next point.

Don’t we Already Have High Accuracy CTs?

The answer to that question is yes. But let’s remember that to be classified as a high accuracy CT that there are certain guidelines that must be adhered to. The IEEE is the body that defines that standard. If you want to learn more about high accuracy CTs follow the link. So the next question then is why do we have extended range CTs if high accuracy CTs already exist and is there a difference?



What is the difference between extended range CTs and high accuracy CTs?

The first difference is that high accuracy CTs actually have a standard that must be met to be called high accuracy. Extended range CTs however do not have this standard. However, most extended range CTs are high accuracy CTs. The reason for this is because manufacturers need a way to separate themselves from the competition. It is not good enough for them to just meet the standard. They need to go above and beyond the standard to attract more customers.

This is good for utilities because it means that in the end they have access to more choices and better products. Utilities who want high accuracy CTs will find that not only are they available but they are available with more extended ranges than the standard requires. Just remember also that an extended range CT is not always high accuracy. Check and make sure that the CT has a rating for high accuracy before believing the salesman. Extended range is something that the manufacturer decides.

Conclusion

Extended range CTs can be used anywhere standard CTs are used. They allow you the ability to meter lower levels of current than you would have before now. This also permits greater revenue over the life of the CT. However, make sure that the CT is high accuracy before you jump on the extended range bandwagon.









What are High Accuracy CT’s?

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High accuracy CT’s are becoming more and more popular with utilities these days. Because of new manufacturing processes and materials, manufacturers such as Peak Demand are now able to make their CT’s more accurate. But, more accurate than what? Just saying that a CT is high accuracy still does not tell us what it is. So, what is a high accuracy CT?

What is a Standard Accuracy CT?

To understand what makes a CT “high accuracy,” we first need to know what the standard accuracy of a revenue grade CT is. To be classified as a revenue grade CT the IEEE states that it must be a Class 0.3. Well, that really does not tell us much. Class 0.3 means that the CT must be accurate to within 0.3% of the nameplate rating up to the rating factor.

We can use a common Class 0.3,  600:5 CT with a rating factor of 2 to create an example. From the nameplate value of 600 amps all the way up to 1200 amps when using the rating factor, the CT has to be accurate to within 0.3%. However, below 600 amps, more specifically from 10% of 600, which is 60 amps, all the way to 600 amps the CT only has to be 0.6% accurate. Below 60 amps the accuracy is not guaranteed. Thus the need for a higher accuracy solution.

What is a High Accuracy CT?

A high accuracy CT is a Class 0.15S. This means that the CT must be accurate to within 0.15%, but there is more. Not only does the Class 0.15S have a closer accuracy tolerance range, the ampere range is greater as well. Now, instead of only being accurate from the nameplate rating up to the rating factor, the CT must be accurate all the way down to 5% of the nameplate value.




We can use a Class 0.15S, 600:5 CT with rating factor of 4 to create another example. In the previous example the CT was accurate to within 0.3% from 600 amps all the way to 1200 amps. From 60 amps to 600 amps the CT was accurate to 0.6%. And below 60 amps there was no guaranteed accuracy. Now with the Class 0.15S 600:5 CT the accuracy is guaranteed from 5% of the nameplate value all the way to the rating factor. So, from 30 amps all the way to 1200 amps the CT is 0.15% accurate. What a difference. This offers a very big advantage to utilities.

Conclusion

A high accuracy CT can be a great solution for any utility that is looking to increase their revenue. Manufacturers like Peak Demand have high accuracy solutions available such as their Alta Series™ of High Accuracy 600V Metering Current Transformers line. The next time you are in the market for CT’s think about using high accuracy CT’s instead of the standard Class 0.3 CT’s you have been using all these years.









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