Monitoring the low voltage grid: How AMI can help

Distribution system operators with AMI systems can leverage the technology to shine light below the substation level. Expert NES tells Engerati more.

There is a joke in energy circles that if you left a group of engineers in a room, they would come up with 40 use cases for smart meters. And rightly so. Distribution operators have long had poor visibility on the low voltage grid compared to its heavily automated and real-time monitored cousins - the high and medium voltage networks - so why not leverage these new sensors.

Seeing a smart meter as just a measurement tool for the meter-to-cash function is a wasted opportunity, says Lars Molske, Product Manager, Low Voltage Grid Analytics & Distribution Outcomes at Networked Energy Solutions (NES).

Molske says NES has always considered smart meters as a communication and distribution sensor, which when combined with power line communication (PLC) and analytics software is capable of making distribution companies “grid aware”.

“At the 400V level, most European distribution system operators (DSOs) are blind,” says Molske. “One function of smart meters is to measure energy but they have another possibility - to monitor power.”

DSOs that have deployed advanced metering infrastructure (AMI) supported by PLC can leverage the technology to monitor power voltage, power factor, average values and power flow.

Molske maintains that the benefits of grid topology mapping to a DSOs business and operational functions are immense, from updating geographic information system (GIS) records to the identification of phase imbalancing.

In a European three-phase context, distribution companies can use AMI to map the voltage on feeder lines from the transformer to smart meters with the added benefit of overlaying the voltage profile.

“Imagine how much you can reduce your operational costs,” says Molske, “if during peak load, you have 60A on one phase and 5A on another. By examining data from smart meters along the line, you can determine which customers are contributing to the high load and send an electrician to shift large power consumers onto another phase.”

Essentially smart meters can offer a phase view of the grid by measuring the power flow on each line rather than a grand average allowing the DSO to identify assets that are being under or over utilised.

Smart Grid Gotland

Swedish DSO Vattenfall has recently completed Smart Grid Gotland - a research project initially focused on the medium voltage grid but latterly on building phase true monitoring.

NES has worked with the utility since November 2016 on the low-voltage part of the pilot to see if Vattenfall can cover capacity by assessing imbalances on the low-voltage grid in real time.

Lars Garpetun, who is responsible for smart meter development at Vattenfall Eldistribution, confirmed that the project had helped the DSO to “understand what is possible to achieve with smart meters.”

Garpetun cites reducing operational costs through better insight in assets utilisation and the grid mapping functionality - to gain a better understanding of the grid’s actual structure - as two benefits.

AMI and distributed generation - what benefits?

Another key application of leveraging AMI for better grid awareness is managing the impact of distributed generation on the distributor’s network.

Upgrid is a European pilot project with the aim of finding “real proven solutions” to enabling active demand and the flexible integration distributed generation through a fully controllable low and medium voltage distribution grid.

The project, which is funded under the European Union’s Horizon 2020 innovation programme, involves 19 partners working on four demonstrations.

Two of the project team - Alexander Babs, Department Manager, Institute of Power Engineering, Poland, and Ana González Bordagaray, Control Systems, Iberdrola Distribución, the leader DSO on the project - told Engerati that AMI is a prerequisite for each achieving high observability of the LV grid.

Babs says the goal of Upgrid is to “turn AMI into a truly multifunctional network, capable of providing a lot of smart grid functions beyond traditional metering.”

Grid functions could be real-time operations and maintenance management through an update of the LV network diagram in the network management system (NMS) and the detection of local outages due to a blown LV fuse or damaged feeder cable.

Other applications would be fault detection, isolation and recovery; support for identifying and eliminating technical and non-technical losses; analysis and adjustment of voltage levels in problematic network nodes; electric power quality tracking, and transformer overload protection.

The pair also believes AMI can provide a communication infrastructure for other smart devices.

A first use case is solar PV inverter controllers to monitor and optimise energy generation. Electric vehicle charger controllers could also use AMI to avoid network congestions through grid-friendly charging process simultaneity, and residential energy storage controllers would benefit by facilitating centrally-controlled demand side response functions.

AMI for LV grid awareness - 3 essentials

Thinking again about that room of engineers and the smart metering use cases, chances are they would have anticipated obstacles to extending the technology beyond billing, and Babs confirms this.

The success of leveraging an AMI system to monitor the LV grid depends on three factors.

First, having a highly available and sufficiently stable PLC communication infrastructure, resistant to interferences in the grid.

Second, having up-to-date and precise LV grid schematics down to the single meter/single smart device.

And third, financing. DSOs will need to find enough investments for a state of the art NMS and advanced LV supervision.

Babs concludes by advising DSOs to: “Choose and install a software package capable of utilising many data sources – like AMI, GIS and SCADA – in order to combine and aggregate this data to provide new LV grid functions.”

Low voltage analytics - webinar

NES's Lars Molske will talk more about the company's project with Vattenfall to achieve visibility beyond the medium voltage grid into the low voltage grid in the webinar 'Low voltage grid analytics: A Vattenfall case study'.