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Network Model Terminology

The HCM reads its network model from the Energy Workbench, which uses the IEC Common Information Model (CIM). Many column names and log messages use CIM terms directly. This page explains the ones you are most likely to see and how they relate to each other. For the full data model, see the CIM model profile.

Identifiers​

mRID​

The mRID (Master Resource Identifier) is the unique ID of an object in the network model. Every piece of equipment, terminal, feeder and usage point has one. Columns ending in _mrid (e.g. conducting_equipment_mrid, usage_point_mrid) hold mRIDs, and these are the keys used to join HCM results back to the network model.

CPI, NMI and ICP​

A CPI (Connection Point Identifier) is the external identifier of a customer's connection point, as used in metering and billing systems. It is called the NMI in Australia and the ICP in New Zealand. Meter data is keyed by CPI.

The CPI is not necessarily the same as the usage point mRID in the network model. The cpi_usage_point table maps one to the other. Where possible, the two values should be identical.

Customers and Loads​

CPI / NMI  --->  Usage Point  --->  Energy Consumer  --->  Terminal  --->  Network
(meter data)     (where load is     (the electrical
                  measured)          connection point)

Usage Point​

A Usage Point is the point where a customer's energy use is measured, i.e. the network model's representation of a metered customer. It holds no electrical connection itself; instead it is linked to one or more pieces of equipment (normally Energy Consumers) that connect it to the network.

Customer load and generation data is stored and fetched per usage point. Where results tables refer to a "customer" (e.g. included_customer_count, customer_allocations), they generally mean a usage point.

Energy Consumer​

An Energy Consumer is the piece of equipment where load is physically connected to the network. It represents the closest electrical connection point to the customer premises, typically where the network responsibility boundary sits. It is what appears as a load in the OpenDSS model.

How they relate​

The relationship can be many-to-many:

  • One Energy Consumer, several usage points. For example, a connection supplying an apartment building, other multi-unit housing or a commercial property. The Energy Consumer carries the combined load of all of them, which is why calibration results can show several NMIs against one simulated voltage.
  • One usage point, several Energy Consumers. Technically supported, although uncommon in practice. Eg a customer supplied from more than one point. By default (loadPlacement = PER_USAGE_POINT) the usage point's load is split evenly across its Energy Consumers.

Virtual usage points​

Some usage points do not represent a real customer. These virtual usage points hold load aggregated to a point in the network, such as a distribution transformer or feeder head, and typically have an mRID ending in -AGG. They are used where load data is aggregated rather than per customer (see Load Tables) and are not modelled as individual customer loads.

Equipment and Connectivity​

Conducting Equipment​

Conducting Equipment is any equipment that carries current and connects to the network, such as lines (ACLineSegment), transformers (PowerTransformer), switches and Energy Consumers. Results reported per asset use conducting_equipment_mrid to identify it.

Terminal​

A Terminal is a connection point on a piece of conducting equipment. A line has two terminals (one at each end), a two-winding transformer has two (HV and LV side), and an Energy Consumer has one. Equipment connects to other equipment through its terminals.

Each terminal has a sequence number (1, 2, ...) that identifies it on its equipment. The HCM uses conducting_equipment_mrid plus terminal_sequence_number to identify exactly where a measurement zone starts or where a result was recorded, as one asset can have different results at each terminal.

Network Hierarchy​

From the top of the HCM's scope down:

  • Zone Substation: the substation where the HV supply is transformed down to MV. The top of the HCM model.
  • Feeder: an MV feeder, starting at the feeder head (the circuit breaker at the zone substation). The HCM runs one feeder at a time; adjacent feeders on the same zone substation are represented as proxy feeders (see Measurement Zones).
  • Distribution Transformer: transforms MV down to LV, e.g. a pole-top or pad-mount transformer.
  • LV Circuit: a section of LV feeder starting at an LV circuit head switch (e.g. a fuse). The finest level of measurement zone.
  • Energy Consumer: the customer connection point at the bottom of the hierarchy.