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Energy Meters: CT Connected/transformer Type Vs Direct Connected

Energy Meters: CT Connected/transformer Type Vs Direct Connected

Measuring the energy used is essential for various industrial applications and homes. The utility bills we pay are based on the energy measured by these meters. Industries also require energy measurement for the same reason, alongside monitoring and data acquisition. This enables them to understand how the equipment functions and whether the internal electrical processes behave as they should. Energy meters are used to fulfill all these demands. Energy meters are necessary equipment for power network systems and related applications. They are also available in various types, divided into two main categories: Direct connected and current transformer (CT) connected. We will take a closer look at these types so you can understand the differences and utility. Without further delay, let’s dive in.

What are energy meters?

Energy meters measure the amount of electrical energy an application consumes. They typically measure this energy and then convert it into the measurement, kilowatt-hours (kWh). This is the same unit of energy that you will see on utility bills. This means that if you use up one unit of electricity, it is equivalent to one kWh. The measurement is generally displayed on a small display for digital energy meters or a dial for analog meters.

Why are energy meters necessary?

Energy meters are required for various applications. This includes those that are industry, residential, or commercial based. Other names, like utility and electricity meters, are also used for energy meters. They are vital equipment because they enable accurate billing and tracking of the amount of energy that has been used. Furthermore, the data they provide can be used to understand the energy demands of a particular application. This can be done for a specific device or the entire population connected to a power system. In this way, they can be used for forecasting and to prepare for future energy needs.

What are the types of energy meters?

Energy meters are available in various forms but can be divided into two main types: Direct connected and CT-connected energy meters. These energy meters differ in how they are connected to the electrical system. The two types are:

Direct Connected Energy Meters

Directed connected energy meters are known by various names. This includes direct-driven, direct-drive, self-contained, and direct-connection energy meters. As their name suggests, these types of meters measure the electrical energy in a way in which the load current passes directly through them. They are directly connected to the electrical system through two terminals. One is for the voltage input, and the other is for the load output.

Uses and Utility

Direct-connected energy meters are generally used for residential buildings and small commercial buildings. The electrical loads involved are relatively low. For example, domestic appliances like kettles and microwaves do not deal with high loads. Directed connected energy meters are designed to operate at a specific voltage and current rating that is mentioned on it. This means that if the load exceeds these ratings, you cannot measure it. This is why it is vital that you carefully choose the suitable direct-driven energy meter for your needs. Typically, these energy meters are rated at a maximum of 100A. Anything more than that will require current transformer (CT) energy meters.

  • Some uses for these meters are:
  • The most common use for these meters is for billing customers by utility companies. These meters accurately measure the amount of electricity consumed. Customers pay their bills according to the measured units.
  • Owners of houses and buildings can also use them to track energy usage. They can use them to identify areas where energy is being consumed inefficiently and rectify them with efficient alternatives. In this way, they can reduce their costs long-term.
  • Utility companies can use it to avoid overloading the electrical grid. This tends to occur when too many people use electricity. They can do this by tracking energy usage, identifying peak hours, and balancing the grid during them. This way, power outages can be reduced, and electricity can be provided reliably.
  • Since energy meters are used in homes, they can also work hand in hand with solar panels. These renewable alternatives are beginning to see extensive use by homeowners. Smart energy meters can measure the energy provided by solar panels and reroute the excess to the grid. This helps reduce costs for homeowners while ensuring that clean energy is used efficiently.

Current Transformer (CT) Energy Meters

CT energy meters are used for industrial and large commercial facilities. In these cases, the power loads and energy demands are much higher and more complex. Generally, these loads will be much higher than 100A, which is the limit to which you can use directed connected energy meters. CT energy meters use current transformers to convert the load current into one easily readable and manageable by the meter. This is done through the principle of induction. Typically, the readable current is 5A, although it can also be 1A and 100mA.

  • Some of the uses for CT energy meters are:
  • They are used to measure industrial applications’ high current energy loads safely. Such high currents typically are incredibly unsafe to be around, as they can lead to injuries. Furthermore, these loads also increase the chances of short-circuiting by putting pressure on circuits. Such cases can lead to explosions and fires. CT energy meters convert the current into a safer form, ensuring workers around energy meters are protected. Additionally, these meters can be installed well away from the high loads being measured. This means you can have them in any desired location.
  • They allow higher loads to be measured accurately and effectively. Typically, measuring devices can measure low currents much more accurately than higher loads. CT meters convert high loads into manageable currents because accuracy is vital for industrial applications.
  • This means the measuring circuit has a lower burden, and electrical usage can be measured effectively.

Differences between directed connected and current transformer (CT) energy meters

The uses and utility we have discussed for these energy meters may have already shown you some significant differences. However, we will still highlight them here for a more comprehensive understanding. The significant differences are:

Connection type

These two meters differ in how they are connected to the electrical system being measured. Direct-connected energy meters connect directly to the system and measure loads directly. On the other hand, CT energy meters use a current transformer to convert the loads into one that is easily manageable for the energy meter to measure.


These energy meters have differing applications due to their working principles. Direct connected energy meters can only handle specific and low loads, usually up to 100A. Hence, they are appropriate for domestic and small commercial applications. On the other hand, CT meters can handle large loads by converting them into manageable loads, well over 100A. Therefore, these energy meters are used for large industrial and commercial buildings.


CT meters are much more versatile than direct connected energy meters. This is because they can measure a wide range of voltage and current levels, meaning they are suitable for various applications. On the other hand, directed connected energy meters are only ideal for specific ratings that are mentioned on them. This means if the load exceeds the rating, it will not be able to measure it.

In conclusion

Measuring energy usage is essential for various reasons, including utility bills and energy consumption. This is where energy meters are handy devices that can help achieve that. There are two main types of energy meters: directed-connected and CT connected. They have a variety of differences, with the main one being how they connect to the electrical system to be measured. This changes their working principle and the applications that they are suited for. In this article, we have looked at each energy meter’s various uses and utility so you can get a suitable one for your needs. Additionally, we have highlighted the main differences to understand why they are suited for different applications.

We hope this article has been informative and helps you understand the two main types of energy meters. Thank you for reading!


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