Cable Group Rating - IEC287 vs ERA 69-30 Part 3

[KJvR]

Hi,

Does anyone have some experience with ERA 69-30 and how their derating factors were derived. I do not have access to this document.

I have modeled some 11kV XLPE cables according to IEC287 and confirmed the values with the cable manufacturer. However, most cable manufacturers refer to ERA 69-30. The IEC287 models provides ampacity levels up to 15% lower than the manufacturer's derating tables that refer to ERA 69-30 Part 3. I will appreciate any thoughts on this. What method/tables is the correct method.

 

[duki]

KJvR,
See my post 1May06. I too am looking for information on this topic. I have the the IEC 60287 standards but do not have the ERA 60-30 part 3 report. You are correct that most of the IEC cable companies prefer to invoke the ERA report and say that it is based on the IEC 60287 standards.

I'm still hoping some Eng-Tips IEC cable guru is listening.

 

[KJvR]

Hi duki,

Thanks for your feedback. I have given up on this thread. Some feedback on what I have learned. Maybe this will get more people involved in this discussion. I have used both hand calcs and EDSA's new ampacity module (based on IEC). Both provide smaller results than the ERA table / manufacturers data sheets. I have obtain the following info since the posting:
(a) The ERA 69-30 Part 3 report heading refer to PVC cables. PVC cables operate at lower temp and therefore provide less losses in the trench and higher rating for a group of cables - IEC equations is not directly proposional. (THIS IS JUST A GUESS - I can not image all the cable companies are using the wrong tables)
(b) I have contacted a Univ doing research on Cable Ampacity for at least 10 years. Their cable expert told me that the IEC is the international recognised method and should be used. They are busy with their own investigation on a simmilar topic.
(c) The body that compiled the ERA tables was also represented on the commitee that compile the IEC 287 document. This make it more difficult to explain the discrepency.

This is not much but at this stage I have decided to stick to the IEC method for complex duct/ U/G cable designs untill I can obtain more info. I am still waiting for some feedback from the Univ and will let you know once I recieved more information.