5 questions to ask when buying a current transformer

Current transformers are responsible for accurate regulation of power for efficient measurement by ammeters and multifunction meters. A mistake in choosing a reliable and durable current transformer could mean errors in measurement, which translate into higher power consumption and a host of power issues. Additionally, a poor-quality current transformer might fail, resulting in downtime and losses.

Choosing the current transformer involves consideration of several factors ranging from materials to performance parameters of the transformer. Apart from these, factors such as nature of the application and various ratings of the current transformer.

Here are 5 key questions to ask when buying a current transformer

Is the current transformer compatible with the power meter? 

Current transformers offer a range of output capabilities from 333mV, to 5A or 80mA. It is essential that the current transformer output should be compatible with your energy meter. If it is not so, the meter may not measure power accurately. In the worst case, if a protection type CT is used for metering, the fault current from power lines might directly arrive at the meter and damage it.

Find out what happens if protection-type transformers are used for metering and vice versa.

Sourcing meters, as well as current transformers from the same manufacturer, could offer the users an edge in compatibility, quality, and costs of the equipment. The meters and current transformers could be specially built to be compatible with each other.

Newtek Electricals offers highly reliable and durable nylon encased current transformers. The nylon casing makes the current transformers resistant to fire and damage from falls during installation. Additionally, Newtek also offers highly accurate multifunction meters with MODBUS communication protocol.

What is the size of the conductor I am measuring around? 

The current transformer must fit properly around the conductor through which the power being measured is passing. Here, oversizing the CT for a smaller conductor might just mean the CT occupies more space and drives up the user’s costs.

How many amps of power are to be measured? 

All the current transformers have a current input range which denotes the size of the load they can efficiently measure. If the peak load is known, and the load fluctuates during the day, like it does in case of lower occupancy in offices during evenings, it is wise to choose a current transformer with a broad current sensing range.

How important is accuracy in measurement?

Current transformers are classified into metering and protection types, with metering CTs veins especially built for accurate energy measurement. In applications such as billing for tenants, having high accuracy in power measurement becomes important.  Power monitoring equipment such as current transformers is often classified as ‘revenue grade” to indicate that it has better than 1% accuracy in power measurement. This could be in the range of 0.5% or better. The user must check the accuracy standard of the current transformer

A common revenue-grade accuracy standard is IEC 60044-1 0.5 Class.

In many developed countries, there is the practice of using current transformers that are suitable for both metering and protection. However, such CTs are not highly accurate, and can only measure the overall power consumption.

Should I use a split-core or a solid core CT? 

Current transformers are classified into two types based on their appearance: Split-core and solid-core CTs. The nature of the application is vital to determining which form of current transformer is to be used.

Solid core CTs: Solid core current transformers feature a permanently closed core, and the conductors must be disconnected in order to install the current transformer. Solid core CTs generally cost less than split-core current transformers. They are more accurate than the latter and are generally used in new installations.

Split core: Split-core current transformers have a core that can be opened so that the CT could be split, and installed around an existing conductor without disconnecting the same. Split-core CTs work better with retrofit applications. They cost more than solid-core CTs, but are easier to install in tricky places.

Conclusion

Current transformers are highly critical pieces of equipment in a power network. Failure of a current transformer could affect the entire network, resulting in financial losses as well as downtime. Newtek Electricals provides durable and reliable current transformers and multifunction meters to businesses in the shortest possible lead time. Innovations in production technology also mean that Newtek CTs are produced faster and cost lower than conventional current transformers.

Apart from the general consideration mentioned here, other performance parameters of the current transformer also play a vital role in the selection process. Read more about these considerations here.