What’s best: “TR CU” or “EAC” Certification?

Sometimes we get questions regarding TRCU & EAC and which is best. I thought it would be good to try to help our customers with this short post on what they are and how they are interpreted.

The compliance with current standards of the technical regulation is critical for importing products subject to conformity to Russia and other Eurasian Economic Union member states.

Many manufactures are confused by the conformity assessment process with what's the difference between TR CU Certificate and EAC Certificate?

It is two different names for the same process of conformity assessment, whereby both terms are wrong or incomplete and misleading translation.

The background of the names is historical when the standardisation originated in the former Soviet Union. The new system of standardisation covers a large part of Eurasia.

This system was known as GOST an abbreviation of "Государственный Стандарт", which translates into "state-standard". and was umbrella standardisation in the Soviet economy. 

With the disintegration of the Soviet Union in the 1990s, several of the member states started developing their standard and conformity assessment procedures, to simplify the confusing GOST system.

Around 2002/2003, the "On technical regulation" law passed in the Russian Federation declaring that new technical guidelines are developed. Subsequently, the "Technical Regulation" "TR" formed containing fixed requirements for products, services & manufacturing processes.

Russia, Belarus & Kazakhstan founded their Free-Trade-Association which eventually became known as a "Customs Union" "CU". Allowing a single technical regulation to facilitate the sale of goods & services between the member countries underpinned by a common standard "TR CU"

Later when Kyrgystan & Armenia joined an opportunity to enhance standardisation further, Europes "CE" mark would be an appropriate model in which to combine with, developing into what today is the "EurAsian Confirmaity" or EAC certificate.

Now EAC is the proper standardised name but is commonly interchanged when TR CU, GOST standard is mentioned/required.

Transformers supplied from ITL destined for the EurAsian market will have the correct EAC certification attached. If you need a copy of our certificate for your project, feel free to reach out to us at marketing@itl-uk.com where one of our team will assist.

Getting the best value out of your CT purchase (Pt.1)

Bit of a wordy headline but as part of my getting the best value out of your purchase series, in this weeks post I am focussing on Metering or Measurement Current Transformers.

When a customer asks for a quotation, he/she may have a price in mind. That might be based on previous purchases or a hunch, but none the less a price is ingrained.

Current Transformers (CT's) while a relatively simple product in nature, sometimes customers are not always sure about what they need and give you a specification that is wildly over-specified for the application. As a CT manufacturer, we understand you are not experts. However, loaded with some knowledge on the factors that can influence price, then there is an opportunity to extract the higher value from your purchase.

RATIO: Primary (input) & Secondary (output) Current Ratio (e.g. 200/5A)

VA: Total instrument burden, including the length of any pilot wires along with square mm of the cable (e.g. 4sqmm).

CLASS: Accuracy required for operation (Tariff, Measurement or Indication

DIMENSIONS: Maximum & Minimum ( the space you have available to fit the current transformer, e.g. for a ring-type Inside Diameter ID, Outside Diameter OD, Axial Length AL).

  1. By specifying a higher VA or ACCURACY CLASS than necessary will likely result in a more expensive product.
  2. Cost generally increases as the Current Transformers inside diameter (ID) increases.
  3. 1A Current Transformers are typically more costly than 5A, why I hear you say - 200/1A has 200 turns of copper whereas 200/5A has 40 turns of copper thus an 80% cost saving on copper, not to mention a reduction in the overall dimensions).
  4. Potentially unnecessary accessories such as mountings which are chargeable extras. (Most customers have their own preferred and cheaper method of mounting inside the switchgear).

Considering the above plays a big part in getting the right product for the right price.

For this post, we will consider IEC 61869 as the default standard, as this is our usual customer requirement. However, should you need IEEE/ANSI or AS (Australia) we are just as at home with these specifications?

IEC 61869 standard:

There is also Class 3 & Class 5 but rarely used, most people opting for a Class 1 as a better alternative.

High accuracy classes like 0.2s & 0.5s often require a special type of core material which in itself very expensive, so this accuracy class should only be selected when a tariff application is required.

We appreciate our customers are not specialist in transformer design but have found that one of the most common misunderstood factors about specifying a current transformer (CT) is the Burden or VA. For example, if you double the burden from 5 to 10VA, you will increase the electrical steel content and thus have a significant impact on the unit price so you must get this right.

The burden is the load imposed on the secondary of the CT at rated current and is measured in VA (product of volts and amps). The accuracy class applies only to loads at rated VA and below, down to one-quarter VA. The burden on the secondary of a CT includes the effect of pilot leads, connections etc. as well as the instrument burden itself.

In situations where the meter is remote from the current transformer, the resistance of the pilot wires may exceed the meter impedance many times in these cases it is often economical to use 1 amp meters and CTs.

The diagram shows the burden imposed on the CT due to a run of pilot wire, so a pilot loop of 2.5mm2 wire, 60 metres long (30 metres distance) has a load of 12.5 VA on a 5 amp CT but only 0.5VA on a 1 amp CT.

Typical Meter Burdens (depending on the pilot lead length):

Moving iron meter 1-2VA

Moving coil meter 1-2.5VA

Digital instrument 1-5VA

Maximum demand indicator 3-6VA

 

Want to find out more about the Principles of Measurement Accuracy? Download our FREE application note.

Got a project where you need help with your CT or VT requirement? Reach out to our engineering team and share your requirements. We're here to help.