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Meters
Overview
The general problems addressed by the meter ontology are:
- modeling meters
- modeling submeters and their relationships
- modeling the flow of energy
- modeling equip and point loads on meters
Meters
Meters are modeled as equip
entities with the meter
tag along with the phenomenon measured. The following meter subtypes are defined:
Flow meters should always be tagged with the substance they are metering. Common examples include:
All meters must additionally define exactly one of these two tags:
siteMeter
: marker applied to the main site level metersubmeterOf
: Ref to parent meter
Electric Meters
Haystack models AC and DC electric meters using ac-elec-meter
and dc-elec-meter
. There is support to model these meters and their points for simple use cases (e.g., just a demand
and energy
point) and complex use cases (e.g., three-phase AC power quality meters). For a common application involving electric utility data see the provided example.
Electricity meter points are described by combining tags from the lists given below. The tags in each set are mutually exclusive. For example, a point cannot have two primary quantities, or have both the volt
and power
tags.
DC electrical measurements are described using a combination of the types of tags below:
AC electrical measurements are described using a combination of the types of tags below:
elec
marker tag- Primary quantity
ac
marker tag- Characteristic of the primary quantity
- Direction (if applicable)
- Location
Note: The primary quantity freq
does not use tags to distinguish a characteristic, direction, or location.
Primary Quantities for AC and DC measurements
Both ac-elec-meter
and dc-elec-meter
support measurements of the following electrical primary quantities:
power
: Instantaneously measured in "kW" units fordc
measurements. Instantaneously measured in "kW", "kVAR", or "kVA" units forac
measurements depending on the characteristicactive
,reactive
, orapparent
.demand
: Measurements indicate an average of instantaneous power values over a defined time interval (e.g., 5, 15, or 30 minutes) and have the same units that are used forpower
measurements.energy
: Similar todemand
, measurements indicate an average of instantaneous power values over a defined time interval (e.g., 60 minutes). Measured in "kWh" units fordc
measurements. Measured in "kWh", "kVARh", or "kVAh" units forac
measurements depending on the characteristicactive
,reactive
, orapparent
.volt
: Instantaneously measured in "V" units for bothac
anddc
measurements.current
: Instantaneously measured in "A" units for bothac
anddc
measurements.
The following primary quantities apply only to AC electrical measurements:
freq
: Instantaneously measured in "Hz" units.pf
: Instantaneously measured as a percentage of AC active power to AC apparent power.
Some electric meters log interval-based data, demand or energy, using a monotonically increasing value in time. The difference of these values between two intervals is used to determine the actual value for an interval. Haystack distinguishes data logged this way using the hisTotalized
tag on the point entity.
Directions for AC and DC measurements
Some electric meters track and report electricity imported from the electric grid separately from electricity exported to the electric grid. The tags import
and export
differentiate these phenomenons. More broadly, export
indicates electricity flowing toward the grid (in the direction of the siteMeter
), and import
indicates electricity flowing toward the load.
These measurements register electricity transfer, involving the primary quantities current
, power
, demand
, and energy
only, in their associated direction and always have positive values.
- For instantaneous measurements (i.e.,
current
andpower
),import
andexport
are mutually exclusive. One will report a positive value and the other will report zero. - For interval-based measurements (i.e.,
demand
andenergy
), it is possible that bothimport
andexport
may report a positive quantity for that interval, which means that some energy flowed in each direction during that interval.
The net
tag indicates the difference between import
and export
:
net = import - export
Haystack uses the load convention for net electricity flow.
- Positive net quantities indicates electricity consumed.
- Negative net quantities indicates electricity produced.
Note: Direction related tags do not apply to angle
, imbalance
, and thd
characteristics used to describe current and voltage.
Characteristics of AC Measurements
AC power, demand, and energy measurements are further qualified by characteristics:
active
: Describes real work being performed. Haystack's standard unit of active power and active demand is "kW". Haystack's standard unit of active energy is "kWh".reactive
: Describes electricity circulated in an AC electrical system that does not result in real work being performed. Haystack's standard unit of reactive power and reactive demand is "kVAR". Haystack's standard unit of reactive energy is "kVARh".apparent
: Describes the overall magnitude of energy movement. Haystack's standard unit of apparent power and apparent demand is "kVA". Haystack's standard unit of apparent energy is "kVAh".
AC voltage and current measurements are further qualified by the following characteristics:
magnitude
: magnitude (assumed as default)angle
: phase angle, typically measured in "deg"imbalance
: imbalance between phases, measured in "%"thd
: total harmonic distortion, measured in "%"
Similarly AC power factor measurements are further qualified using a pfScope
choice:
pfTrue
: True power factorpfDisplacement
: Displacement power factorpfDistortion
: Distortion power factor
Note: The primary quantity freq
does not have characteristic related tags.
Locations for AC Measurements
Generic tags are used to describe three types of ac
electrical measurements that do not involve aggregation of multiple measurements:
elecLine
: for electrical line measurements "L1", "L2", and "L3"elecLineToLine
: for electrical line-to-line measurements "L1-L2", "L2-L3", and "L3-L1"elecLineToNeutral
: for electrical line-to-neutral measurements "L1-N", "L2-N", and "L3-N"
Non-aggregated ac
electrical measurement locations are qualified by:
lineVolt
:elecLineToLine
phaseVolt
:elecLineToNeutral
lineCurrent
:elecLine
phaseCurrent
:elecLineToLine
linePower
:elecLineToLine
phasePower
:elecLine
linePf
:elecLineToLine
phasePf
:elecLine
lineEnergy
:elecLineToLine
phaseEnergy
:elecLine
ground
: for electrical current measurement of the electrical ground conductorneutral
: for electrical current measurement of the electrical neutral conductor
Note: In the future phaseDemand
and lineDemand
tags may be defined. For now phasePower
or linePower
tags may be used to describe point entities with the demand
tag.
Aggregated three-phase ac
electrical measurement locations are qualified by:
lineAvg
: When applied to a point entity with thecurrent
tag, indicates the average of the values for thecurrent
primary quantity characteristic at all locations defined inelecLine
. When applied to point entities with thevolt
,power
,pf
, orenergy
tags, indicates the average of the values for the primary quantity's characteristic at all locations defined inelecLineToLine
.phaseAvg
: When applied to a point entity with thevolt
tag, indicates the average of the values for thevolt
primary quantity characteristic at all locations defined inelecLineToNeutral
. When applied to a point entity with thecurrent
tag, indicates the average of the values for thecurrent
primary quantity characteristic at all locations defined inelecLineToLine
. When applied to point entities with thepower
,pf
, orenergy
tags, indicates the average of the values for the primary quantity's characteristic at all locations defined inelecLine
.total
: Applies only to point entities withpower
,demand
, orenergy
tags. Indicates the sum of the values for the primary quantity's characteristic at all locations defined inelecLine
.
Aggregated split-phase ac
electrical measurement locations are qualified by:
lineAvg
: When applied to a point entity with thecurrent
tag, indicates the average of the values for thecurrent
primary quantity characteristic at the "L1" and "L2" locations defined inelecLine
.phaseAvg
: When applied to a point entity with thevolt
tag, indicates the average of the values for thevolt
primary quantity characteristic at the "L1-N" and "L2-N" locations defined inelecLineToNeutral
. When applied to point entities with thepower
,pf
, orenergy
tags, indicates the average of the values for the primary quantity's characteristic at the "L1" and "L2" locations defined inelecLine
.total
: Applies only to point entities withpower
,demand
, orenergy
tags. Indicates the sum of the values for the primary quantity's characteristic at the "L1" and "L2" locations defined inelecLine
. This tag is also used in conjunction with theelecLineToLine
tag that has a value "L1-L2" to help describe the complete flow of electricity in a common way for three-phase and split-phase electrical systems.
Note: The primary quantity freq
does not have location related tags.
An Example Utility Application
Many electric utilities commonly use three AC electricity measurements for computing a monthly bill:
- Peak active demand (kW)
- Total energy consumption (kWh)
- Peak apparent demand (kVA)
It might be desired to monitor these data points using a granular interval (e.g., 5 minutes) on a siteMeter
to better understand or help validate these metrics used by the electric utility for billing. In some cases the electric utility might offer this interval data. Otherwise customer owned electric metering may be used to obtain it.
At a site with a 3-phase electric utility service, these data points would be modeled as follows:
- For peak active demand - a point with the tags
ac
,total
,active
,import
, anddemand
- For total energy consumption - a point with the tags
ac
,total
,active
,import
, andenergy
- For peak apparent demand - a point with the tags
ac
,total
,apparent
,import
, anddemand
Also, all three of these data points should have a hisMode
tag with a value of consumption
applied to indicate they model interval based data.
Flow Meters and Thermal Meters
Flow meters measure flow rate and total volume of fluids. Thermal meters (sometimes called BTU meters) also use temperature sensors and can provide power and energy calculations. Points for flow meters include:
flow
: rate of volume flowing through the meter per unit timevolume
: total volume consumption of the meterpower
: energy consumed per unit time such as "BTU/h"energy
: energy consumption such as "BTU"
Note that thermal meters should use the same power
and energy
tags as elec meters.
Flow meters must always be tagged with the fluid they are metering. For example a natural gas meter must be tagged with naturalGas
. If a meter measures flow/volume then add the flow
tag. If the meter measures power/energy then add the thermal
tag.
Examples:
// Natural gas meter id: @gasMeter naturalGas flow meter equip // Steam thermal meter id: @steamMeter steam thermal flow meter equip
Energy Flow to Loads
We use the suite of <phenomenon>Ref
tags to model the relationship of energy flows from the meters to their load. Commonly used relationship tags include:
elecRef
: model flow of electricitynaturalGasRef
: model flow of natural gaschilledWaterRef
: model flow of chilled water for coolinghotWaterRef
: model flow of hot water for heatingsteamRef
: model flow of steam for heating
These tags are placed on the loads and reference their upstream meter. For example, a boiler would use the naturalGasRef
to reference its upstream meter as follows:
id: @gasMeter naturalGas flow meter equip id: @boiler steam boiler equip naturalGasRef: @gasMeter
Example Model
Let's illustrate a more complete example using a "tree" of meters and loads:
Main Elec Meter +- Luminaire (equip load) +- HVAC Elec Submeter +- RTU-1 (equip load) +- Fan (point load) +- DischargeTemp (not a load) +- RTU-2 (equip load) +- Fan (point load) +- DischargeTemp (not a load)
The entities and their tags would look like this:
id:@A, dis: "Main Elec Meter", ac, elec, meter, siteMeter, equip dis: "Main Elec Meter Demand", equipRef @A, elec, power, unit:"kW", sensor, point, ... dis: "Main Elec Meter Consumption", equipRef:@A, elec, energy, unit:"kWh", sensor, point, ... id:@B, dis: "Luminaire", equip, elecRef:@A, luminaire id:@C, dis: "HVAC Elec Submeter", ac, elec, meter, submeterOf:@A, equip dis: "HVAC Elec Submeter Demand", equipRef:@C, elec, power, unit:"kW", sensor, point, ... dis: "HVAC Elec Submeter Consumption", equipRef:@C, elec, energy, unit:"kWh", sensor, point, ... id:@D, dis: "RTU-1", equip, elecRef:@C, ahu dis: "RTU-1 Fan", equipRef:@D, elecRef:@C, fan, cmd, point, ... dis: "RTU-1 DA Temp", equipRef:@D, discharge, air, temp, sensor, point, ... id:@E, dis: "RTU-2", equip, elecRef:@C, ahu dis: "RTU-2 Fan", equipRef:@E, elecRef:@C, fan, cmd, point, ... dis: "RTU-2 DA Temp", equipRef:@E, discharge, air, temp, sensor, point, ...
In the example above we have a top-level main electrical meter with the id @A
. Note it is tagged as ac-elec-meter
to model an AC electric meter. It is also tagged as siteMeter
to indicate its the main site-level meter. It has two associated points for power (kW) and energy (kWh).
Next, since we don't have a lighting submeter, the lighting load references the main meter directly via its elecRef
tag.
After that, we have an HVAC submeter with the id @C
. Note it is tagged as ac-elec-meter
also. But it is not a siteMeter
; instead it is associated as a submeter of the main meter using the submeterOf
tag. You can model submeter trees of arbitrary depth (submeters of submeters). It also has two points for kW and kWh.
Lastly, we have three electrical equipment loads defined. The two RTUs are associated with HVAC submeter via elecRef
which references the HVAC submeter via id. We also tag one or more points under the equipment that are meaningful for the load. Motors would often be tagged as loads since they draw energy, but sensors would typically not be considered loads.