My current series of articles (which isn’t really a series at all) is focused on topics I’ve been asked about by more than 10 utilities. I figured this signifies there being enough interest to dive into a topic and to document our experiences at SSP Innovations. This month I wanted to write about Telvent’s Extended Feeder Manager (EFM), what it is, what it does, and how it can be used in some cool ways at US-based electric utilities.
The vast majority of US-based utilities manage a two-level electric distribution network. The source of the network is typically identified by a distribution circuit breaker within a substation which feeds primary voltage electricity downstream to distribution transformers. which then steps the primary voltage down to secondary voltage, which then feeds the customer. Many years ago Telvent released the original Feeder Manager which is designed to manage the connectivity from the source circuit breaker all the way to the service point where the meter is located. I won’t spend much time talking about Feeder Manager because I am assuming most of the readers out there already use standard Telvent Feeder Manager to manage their GIS electric distribution networks and are familiar with the details. It’s a great tool and a focal point of the value that the Telvent ArcFM™ suite brings to an electric utility.
As Telvent grew their business overseas they began to encounter challenges in using standard Feeder Manager at European utilities that commonly have multi-level networks that span different voltages. An example might be a feeder that starts out at 60kV is then stepped down to 10kV and then further stepped down to .4kV before being fed out to the service points. Standard Feeder Manager could certainly manage the connectivity of the feeder from the source to the service point but it did not provide the utilities the granularity they were looking for in being able to relate any given point on the network to the various upstream locations where the voltage was stepped down along the way. To state it another way, the requirement was to be able to explicitly identify the multiple voltage tiers within the electric network. In 2009 Telvent introduced Extended Feeder Manager (EFM) to meet this requirement.
EFM provides support for the multi-level networks by establishing a hierarchy of circuit sources to differentiate the voltage levels. The original, top-level source is deemed the "ultimate source" and each voltage tier below the ultimate source is defined by a "sub source" which represents the device/location where the feeder is split after the voltage is stepped down. In this picture the ultimate source feeds a high voltage (HV) tier. The HV feeder is then stepped down to a medium voltage (MV) tier and is split into multiple sub sources. Each of those MV feeders are then eventually stepped down even further to a low voltage (LV) tier which is further split into multiple sub sources. The cool part about EFM is that this pattern can be established for as many voltage levels/tiers as you need to define. Each sub source acts as the originating point of its voltage tier but also has a relationship to its parent source which is either another sub source or at the highest level, the ultimate source. Like standard Feeder Manager, each electric feature in the network still manages a "feeder id" which contains the id of the ultimate source but they also now track the id of their immediate parent sub source feature which defines the voltage level. This establishes the voltage hierarchy.
This approach worked wonderfully for the European utilities and allowed them to effectively create, maintain, and trace out their multi-level networks. The concept was intriguing to many utilities in the US as well but there wasn’t a totally clear direction on how it could be applied to gain the most business value. At the most basic level you could define a two level network with the ultimate sources being your circuit breakers in the substations and the sub sources being your distribution transformers but this doesn’t add much more value than a standard Feeder Manager implementation. In speaking with many US utilities we’ve documented that to get the maximum value from EFM, we have to find a way to bridge the connectivity gap between our transmission grid and the distribution circuits.
In a simplified US model we will have a high voltage (ex 138kV) transmission line feeding into a substation, connecting via a transmission bus to one or more power transformers that step the voltage down to primary voltage (ex 12.5kV) which then connect via a distribution bus to multiple distribution circuit breakers. There are always additional devices in the mix here but we’re going to keep it simple here to facilitate the discussion. If EFM can provide the ability to trace upstream through the circuit breaker to a power transformer this could be valuable. And even more so if we can trace downstream from a power transformer into multiple distribution circuits to capture the connected service points (i.e. the customers) we can start getting some really useful results. In the case of an outage in the substation we could quickly and accurately get all downstream customers. And if we are using an outage management prediction engine it can now predict upstream of a circuit breaker based on a large scale outage.
So with the goal identified, we set out to find the best way to implement EFM to meet this goal and to provide the most useful information to the users along the way. The ultimate source of a transmission grid is going to be a generating station. The transmission grid is then interconnected and feeds from multiple different directions. Within GIS the transmission feed very often feeds into substation #1 and then also continues out of substation #1 and on to substation #2 and so on until it eventually makes a complete circle. One or more generating stations may feed the transmission power onto this large loop ensuring that if a failure occurs at any point on the transmission loop, the electricity continues to flow to the substations.
So at first we considered making the ultimate EFM source a generating station, but that would imply that a very large contingent of the transmission and distribution features would be tied back to a single ultimate source id. As we explored this option it didn’t seem like this would provide enough granularity to make it valuable. So we started looking further at how utilities labeled and identified segments of the transmission grid. What we found was that utilities typically assigned a unique id to the transmission line that connected each substation to the next substation. For example they might identify a transmission segment with a Sub1-Sub2 formatted name.
It then seemed that if we could use that Sub1-Sub2 id as the source that fed the power transformer we might be onto something. The only issue was that to uniquely identify each sub-to-sub transmission segment we would have to break the transmission grid connectivity at each substation to begin a new segment with a new id. If I’ve totally confused you at this point, stick with me a little bit further as I illustrate this concept in the GIS (I’m close to confusing myself as I write this so don’t feel bad).
So in EFM terms, we want to create an ultimate source that identifies each sub-to-sub transmission segment. Since there isn’t really a device in the field that represents the source of each of these segments (because the grid is interconnected) we added a new feature class called a TransmissionSegmentNamer. Its sole purpose is to name the transmission segment from sub to sub and to act as the ultimate EFM source. The following GIS picture shows a simple transmission model using the TransmissionSegmentNamer ultimate sources. The ultimate sources are shown as the stars in the picture and I have labeled the lines with their transmission feeder id which identifies the segment in a sub-to-sub format:
As you can see, the connectivity of the transmission lines is broken at each substation which allows us to individually name the segments. It also prevents us from creating a feeder manager multi-feed condition which would mean that a single line is being fed by two sources. This condition can cause some issues with tracing, etc and we definitely want to stay away from it. If we inspect the attributes of the transmission line between sub A and sub B we can see that it has picked up the transmission segment id:
The next step is to model a simplified inside connectivity model within each substation. We will model the incoming transmission segment connected to a transmission bus that feeds multiple power transformers. The power transformers are configured as our first EFM sub source in the model:
The power transformers are being fed by the incoming 138kV A-B line. They are being labeled on their power transformer id but note that their feeder ids are set to the incoming A-B transmission id:
This is the first level where we can see the EFM hierarchy. Because the power transformer is a sub source it acts as the source of everything downstream but also maintains the relationship to the upstream parent ultimate source (A-B in this example). Next we will model the downstream distribution bus for each of the power transformers which will then connect to one or more distribution circuit breakers:
In this example each power transformer feeds three distribution circuit breakers labeled SubB-1 through SubB-6. These circuit breakers are also modeled as sub sources. They will act as the source of the individual distribution circuits but will also maintain the tie back to their immediate parent source - the power transformer AND to the ultimate source - the transmission segment name of A-B. The attributes of the circuit breakers show this information:
This screenshot shows the distribution feeder id which will act as the ID for the downstream distribution circuit and the transmission feeder id which shows the transmission segment name. The relationship to the power transformer is managed via a hidden field which maintains a numeric foreign key to the power transformer circuit source record. To make this hierarchy information available to the users we added a small SSP customization to the solution that provides a right click Extended Feeder Manager Details within the ArcFM™ Attribute Editor:
This then brings up a simple message box that shows the hierarchy between the selected device all the way back to the ultimate source:
This message clearly tells us that there are two parent levels in the hierarchy for this circuit breaker. The first is B-1 which represents the power transformer and the second parent is the ultimate source of A-B which represents the transmission sub-to-sub segment.
Now we will continue to build out the distribution circuit just as we would using standard Feeder Manager. In our simplified example we have added primary overhead, a fuse, a distribution transformer, secondary overhead and finally a single service location:
The important thing to note in this picture is that both the transmission segment name AND the distribution feeder id are being maintained on all features in the distribution circuit. To accomplish this at the actual attribute level of the features, we added one more SSP customization with an additional AutoUpdater to set the distribution feeder id in addition to the ultimate source feeder id on all electric networked features. This makes both ids available all the way down to the service location. By default EFM will only maintain the ultimate source feeder id and this small enhancement adds a lot of additional value:
And to drive home the point we can now bring up the Extended Feeder Manager Details on the Service Location to show the hierarchy from the customer all the way back to the transmission segment name:
The Parent Level 1 shows the distribution breaker ID, the Parent Level 2 shows the power transformer ID, and the Parent Level 3 shows the transmission segment ID. Using the configurable EFM approach, we could have easily added another voltage tier at the distribution transformer if desired.
And finally we can now demonstrate how the ArcFM™ tracing works with this model. If we run an upstream trace from the service location, the trace does not stop at the distribution breaker but will continue all the way to the ultimate source at Sub A:
If you just want to get to the distribution breaker that feeds the service location, you can still run the upstream protective device trace (shows the fuse and the breaker):
And finally as we noted earlier in the article, we can do some very useful downstream traces from the power transformer which will include ALL of distribution circuits downstream of the transformer:
And/Or we can go one level higher to trace out ALL distribution circuits fed from the substation:
I hope this US-based Extended Feeder Manager article has helped to show how we can use Telvent’s EFM in some powerful ways without any booking any travel costs to Europe! If you’ve implemented EFM in the US, we’d love to hear from you about your implementation as well. Where did you identify the value-added components and how did you configure the model? And finally, this article would be incomplete without giving a shout out to the main brain behind both standard Feeder Manager and EFM. John Bennett has been one of Telvent’s leading utility software powerhouses dating back well into the Miner & Miner days. His work is being used around the world and has given many of us plenty of inspiration to push the envelope even further.