Direct Connected or Current Transformer Operated Meter what do you need and what are the differences?

There is a big difference when it comes to finding out what version of meter you would need whether this works as CT operated or Direct Connected, not to be confused with Direct Current. A Direct Connected Meter has two sets of terminals, one for the voltage input and the other for the load output. The load current passes through the meter itself. Most residential meters are of this type. A Current Transformer Operated Meter uses the Current Transformers (CTs) to convert the primary current input into the secondary current output and then communicates this with the meter, sending the data of what current readings are passing through the cable that the CT is clamped round. Many industrial meters are of this type.

At Smart process we offer single and three phase meters that can be either Direct Connected or CT Operated. These come in various module sizes and can be put in an enclosure with the required terminals for a neater installation. They can also just be mounted straight into your consumer unit if room is available.

 

A Directed Connected Meter is often used in residential properties because most of the residentials use only a small load, allowing it to be wired directly. The load refers to the current and the voltage flowing from the grid to the appliances in the property. Single phase Meters are more often than not direct connected due to them being used in small residential properties and the load being smaller. Direct Connected Meters are mostly rated to 100A meaning they can measure any load that is 100A or less. If your load is over 100A, you will need a CT Operated Meter

 

A Current Transformer Operated Meter is often used in commercial / industrial properties because in demanding environments like factories, the load is much greater than 100A. When the load is greater than 100A, the meter requires a CT to convert the current to a readable value for the meter, most commonly being 5A. The secondary output can differ between meters and CTs but you must ensure your secondary output on your CT matches to your CT input on your meter. As mentioned, this will mainly be 5A but can also be 1A, 100mA, 333mV, 85mV, 100mV and more.

Split Core CTs allow you to complete an installation live as the CTs can open up and wrap round the live cable. Split Core CTs are ideal to use when retrofitting. Solid Core CTs cannot be opened and therefore are better suited to a new installation, where the tails can be fed through the CTs.

 

Single Phase CT Operated Meters need one singular current transformer, whether this be split core or solid core. A Three Phase CT Operated meter require either three Single Phase Split Core or Solid Core CTs or alternatively, one Three Phase Block CT which is like three Single Phase Solid Core CTs moulded together in one case.

At Smart Process we strive to offer the best possible solution for you. This means personalising the solution to be perfect for your application. The solutions we offer have been carefully curated by our metering experts who can assist you in product selection, whether its CT operated, Direct Connected or if you’re unsure, get in touch and we will give you guidance.

SDM120 Series, SDM230 Series, SDM54 Series, SDM72 Series, SDM630 100A Series,

SDM120-CT Series, SDM72CT Series, SDM630MCT Series, SMART-X96 Series

 

Overall, you will need to confirm the maximum current you are measuring in order to choose CT operated or Direct Connected. If its over 100A, you will need a CT Operated meter. If its under 100A, you have the choice of Direct Connected or CT Operated. Generally, when retrofitting, you will use CT Operated with split core CTs. On brand new installs, Direct Connected in a good option. Residential often need a direct connected single-phase meter due to their small amps and industrial will need a three phase current transformer operated meter as they have a larger amperage demand.