1. What is an IFD?
The Internal Fault Detector (IFD™) is a high value, low-cost, reliable sensor that is installed in oil filled pole type transformers.

The IFD signals the presence of an internal fault inside a transformer. This allows line crews to make a fast and reliable identification of an internally faulted transformer from the ground without climbing the pole.

The IFD deters line crews from attempting to re-energize faulted transformers, thus reducing the risk of injury to the line crew and damage to equipment, and saves line crew response time in the process. 

2. When will the IFD activate?
The IFD will only activate when the internal pressure in the airspace in a transformer increases at a rate of at least 0.5 psi in 5-7 milliseconds. Research shows that during an internal fault (where the fault current is 500A or above), this rate is the typical pressure rise experienced inside a pole type transformer.

The IFD will NOT activate during normal pressure changes inside the transformer.

3. Why should utilities buy the IFD?
It saves money…the investment in the IFD pays a considerable return across a broad range of current utility operating expenses:

When there are transformer outages, utilities know the many budget areas that are affected, and how expensive it can get. Of course, this includes loss of service to customers, and the related revenue.

4. What do line crews need to do?
When the transformer is initially installed they simply remove the orange shipping lock by pulling firmly on the lock when the transformer is on the pole, and before they connect the transformer to the network.

When the transformer has an internal fault the IFD will have activated and the safety orange indicator will be visible and the line crew simply removes the transformer from service without further inspection.

5. How do I train my line crews?
IFD Corporation provides a training video and Line Crew Information Guide to assist utilities to train their line crews and update their training documentation.

6. What transformer types is the IFD suitable for?
All certification testing was conducted in oil filled, round, single phase pole type transformer tanks with the following parameters:

Although certification was performed on the above transformers, the IFD may also be suitable for other transformers with similar characteristics as those tested.  Please contact IFD Corporation for other transformers.

7. What size products are available?
|The one IFD device is suitable for installation in all pole type distribution transformers as outlined in Question 6 above.

The IFD is available with a choice of 3 various pressure relief devices (PRD). A 5psi, 7psi and a 10psi PRD are available (customer specified). 

8. Can the IFD be used in 3-Phase transformers?
Yes, the IFD has been installed on 3-phase transformers. Their fault environment and conditions are similar to single-phase pole type transformers.

9. Can the IFD be used in padmounted transformers?
The IFD has not been designed for or tested in padmounts. IFD Corporation is currently developing a padmounted version.

10. Is it difficult for transformer manufacturers to install the IFD?
No.  IFD Corporation has prepared an IFD Installation Guide to assist manufacturers with the installation of the IFD.  IFD Corporation will also visit the manufacturers plant to certify the transformer manufacturer and ensure the IFD is installed correctly with minimal changes to the manufacturer’s current procedures.

11. Can the IFD be retrofitted?
Yes, the IFD can be retrofitted. It requires a hole with a 1.34” diameter, the same size as a small busing or tap switch. When the IFD is installed you no longer require a separate PRD, so it should be removed and the PRD hole plugged with a standard hole plug.  

In any retrofit situation, the utility should contact IFD engineering for guidance and specific support if required. There is an installation guide for the correct installation process.

12. Can the IFD unit be re-used?
No. IFD Corporation certifies the device for a single use. Even if a transformer has faulted at low current level, there could be damage to the sensor that is not obvious.

The IFD cannot be reset once activated; this further deters any attempt at re-fusing a faulty transformer.

13. How long will an IFD last?
The IFD is designed to last for the life of the transformer.

The IFD showed no signs of operational fatigue or failure over a 30-year time frame in materials analysis.

The IFD should not be re-used once a transformer has faulted. The sensitive detection components may have been damaged in the fault event.

14. Will it false activate, or not activate even if there is an internal fault?

The IFD is a mechanical device and so it is possible that it could fail for some reason, as is the case with any mechanical device. However, the IFD’s reliability is achieved through:

Based on the actual field experiences, the IFD has operated, as it should in field fault events. Even if the IFD does not operate, the utility is always guided to rely on its standard safe operating procedures.

15. What about other internal fault detecting technologies?
Tools and procedures such as current limiting fuses, off-line impedance testing systems, or ‘black boxes’ are all useful tools, and for some time they will still be required. However, the customer concerns with these tools are:

The IFD detects the ‘first occurrence’ of the internal fault when the transformer fails. By the time the line worker gets to the transformer he simply looks up, sees the orange flag and replaces the transformer. There is no further problem identification required on the transformer. 

16. Who was involved in the development of the IFD?

Together with utilities, transformer manufacturers and others IFD Corporation designed, built and tested various units to arrive at the current product. A detailed version of the certified test report is available from CEA Technologies who sponsored the report itself.

17. “This is such a good idea, why didn’t someone think of it before?”

The development of the IFD to achieve the necessary sensitivity and satisfy the many requirements of electric utilities and transformer manufacturers required an innovative idea and then over 10 years of investigation, research and development, testing and prototyping before the IFD was ready for large scale manufacturing and installation in pole type transformers.

18. What testing was done?

These tests are always on-going as part of the IFD Quality Control process. For details on the testing please see the IFD Technical Specifications.

19. How were tests conducted?

All tests were completed successfully. For details on the testing please see the IFD Technical Specifications.

20. How often do distribution transformers experience an internal fault?
From one large utility study, between 2% and 5% of the total pole type distribution transformers are re-energized every year, which equates to approximately 20,000 re-energizing / year.  Of this, 4,500 (or about 20%) have internal faults. More than 5% of those has violent tank explosions.

Numbers will vary from utility to utility depending on frequency and severity of storms, lightning and other such factors.

Importantly however, the IFD will provide line crew guidance in all re-energizing attempts. If the IFD has not activated the transformer should be safe to re-energize, and the fuse cutout operated for reasons other than a faulted transformer.

21. What are the customer field experiences?

.22. How do I order the IFD?
The IFD is packaged on pallets containing 1224 IFD units complete with 1224 PRD (5psi, 7psi or 10psi – customer specified) and 1224 shipping locks.

The PRD’s and shipping locks are packaged separately to the IFD body to allow transformer manufactures to install the body, PRD and shipping lock at separate locations during the manufacturing of the transformer.

Contact  IFD Corporation for further information on specifying the Internal Fault Detector (IFD™) in your utility.