It's all about pole-mounted distribution transformers. Like every other utility, line crews at Hydro-Québec (Montreal, Canada) find reclosing on distribution transformers both potentially dangerous and time consuming. With fuses blown and reclosers open, deciding when to re-fuse a transformer and put it back in service can be difficult. Is it just the fuse, or has the transformer faulted?

The Internal Fault Detector (IFD) from IFD Corp. (Vancouver, Canada) was in development for more than a decade, and represents the result of a collaborative research and development effort involving financial and technical support by the National Research Council, a group of utilities and CEA Technologies Inc. (Montreal). The objectives for the IFD were to improve worker productivity, enhance customer service and increase overall safety associated with transformer failures. More than 45% of all new pole-mounted transformers in Canada are now shipped with an IFD.

Until recently, there had not been a sound, reliable test — without disconnecting the transformer and applying voltage — to detect faulted pole-mounted transformers. Hydro-Québec now uses IFDs that physically flag faulted pole-mounted transformers.

The IFD has two functions. It incorporates the pressure-relief device (PRD) and provides a visual indication on whether the transformer has faulted internally. The PRD conforms to ANSI's PRD standard, and the sensor inside the IFD detects pressure changes in the airspace above the oil that are caused by internal faults.

The IFD sensor is calibrated to respond only to pressure changes due to faults, not to normal pressure changes due to increased load or rising ambient temperatures. When a fault is detected, an orange indicator, which can be seen from the ground, pops out. The line crew knows immediately that the transformer needs to be replaced. No time is wasted even considering the bad decision to reclose on the transformer. No one is placed in danger, and the utility saves time and money.

Like all utilities, Hydro-Québec continuously looks for ways to increase efficiency. So, if you consider the time it takes to properly reclose on a potentially dangerous transformer, there is a real operational advantage to using IFDs because they remove the time-consuming decision-making process (return to service or replace) to determine if the transformer is faulted. Our experience has been that only one out of four transformers is usually faulty.

When an IFD has activated, a line worker or scout can call the dispatcher and report that the transformer has faulted, the size of the transformer and the location. Hydro-Québec then sends a replacement team. When the line worker determines the transformer has not faulted, the worker can look to different causes for the fuse operating before starting the process of safely re-energizing, which leads to a faster, safer resolution of the problem. So, in all circumstances where the fuse has operated and an IFD is installed, the line worker saves time.

Hydro-Québec has an objective of zero accidents. The utility also has some of the strongest safety-oriented policies in the utility industry. The decision to use the IFD is one of the many policies that address this objective. When you try to increase the efficiency of your process, you have to maintain, if not increase, the safety level.

Before including the IFD in its transformer specification, Hydro-Québec toured the manufacturing facility. IFDs are manufactured with stringent quality control, and each IFD is tested in the lab before being shipped. Therefore, it is highly unlikely an IFD device would give a false negative. Even so, mechanical failures are possible. To be on the safe side, IFD Corp. recommends that transformers where the IFD has not operated be reclosed following each utility's standard safety procedures.

Customer service is important to Hydro-Québec. By making diagnoses faster and improving the efficiency of trouble crews, utilities can reduce the system average interruption duration index. Restoration is quicker because time is not spent restoring what is faulty. All the information is rapidly being sent to the dispatcher, who then decides how many transformers to send and how many work crews to assign.

Hydro-Québec is considering launching a public-awareness campaign to let customers know about IFDs. The company would ask the public to check for an IFD on their transformers and, if they do see the orange indicator of an IFD, to let Hydro-Québec know so it can make a no-light call. It would be easier for Hydro-Québec to know which kind of crew it has to send on the trouble call, which means faster restoration and increased customer satisfaction.

Like every other utility, Hydro-Québec finds dealing with outages, especially major storm outages, challenging — particularly if there have been many lightning strikes. In a severe lightning storm, literally thousands of fuses can operate in a limited geographic area in a period of only a few hours. This puts tremendous pressure on the linemen who are working to restore power. As transformers fail in these areas, they are being replaced by units with IFDs. So, units with IFDs are finding their way into the areas they are most needed. Annually, Hydro-Québec replaces 3000 faulty transformers, which has been the average over the last 10 years.

Hydro-Québec has more than 3.3 million customers and about 550,000 pole-mounted transformers. Each year, the utility installs between 10,000 and 12,000 new units — all of which have IFDs installed by the transformer manufacturer.

Hydro-Québec's line workers would like a higher penetration rate, but this is not possible yet. The most efficient method for getting IFDs onto a system is through the installation of new transformers (either through new construction or the replacement of existing units). It is possible to retrofit a unit with an IFD, but the costs associated with removing the transformer from the pole to do so are currently too high to make it cost effective. On the other hand, the cost to have an IFD installed in a transformer already in the shop is relatively low.