User's Manual

Bridges Hardware Guide Silver Spring Networks 28
Glossary
trical distribution devices such as reclosers, switch-
es, transformers and capacitor banks.
dB Decibels. A logarithmic unit of measurement that
expresses the magnitude of radio power.
dBm The power ratio in decibels (dB) of radio power
relative to one milliwatt (mW).
dead area Locations from which effective transmis-
sion cannot be established because the transmitted
signal is blocked by clutter. Also known as shadow.
decimal degrees A numerical way of expressing de-
grees, minutes, and seconds longitude from Green-
wich, England and latitude from the equator:
decimal degrees = degrees +
(minutes / 60) + (seconds / 3600)
Positive numbers indicate East longitude or North
latitude. Negative numbers indicate West longitude
or South latitude. For example, W 122° 28’, 39.3”
longitude by N 37° 49’, 11.2 latitude expressed in
decimal degrees is:
-122.477583 longitude by 37.819778
latitude
demand The highest requirement for power, that is,
the amount of power required to satisfy the de-
mand. There is no time element involved. The high-
est requirement for power can occur in an instant. In
practice, most demand meters measure the aver-
age peak demand over the 15 or 30 minute period.
This definition of demand differs from energy in that
energy is the usage of power over time whereas
there is no time element in measuring demand. De-
mand is measured in kilowatts (kW) and energy is
measured in kilowatt-hours (kWh).
For example, a demand for 100 kW continuous for
an hour equals 100 kWh. If the demand rose to 400
kW continuous for the next hour, the demand for
that hour equals 400 kWh. For the two hour period,
the demand is 400 kW because that is the highest
requirement for power. The energy used is 500 kWh
because that is the actual usage of power over time.
See also energy and time of use.
device Access Point, Relay, or meter. Meters can be
electric, gas, or water. See also IMU.
dissimilar neighbor A neighbor device that, be-
cause of its dissimilarity, maximizes the odds of re-
ceiving a last gasp from another device.
distance vector One of the two major classes of
routing protocols, distance vector routing requires
that a router periodically inform its immediate neigh-
bors of any changes in its topology. A distance vec-
tor means that routes are advertised as a vector
comprising several characteristics, including next
hop address, egress interface, and metrics such as
hop count. routers using such a protocol do not
have knowledge of the entire path to a destination
unless that destination is directly connected to
them. Routing in the Silver Spring system uses a
distance vector protocol on Layer 2.
distributed generation A distributed generation sys-
tem involves small amounts of generation or pieces
of generation equipment applied to a utility’s distri-
bution system for the purpose of meeting local peak
loads and/or displacing the need to build additional
infrastructure. Distributed generation may be in the
form of gas or propane generators, fuel cells, or so-
lar.
distribution automation (DA) The computerized or
intelligent control of the electrical power grid down
to the distribution level. In recent years, DA has be-
come nearly synonymous with SCADA.
distribution power A packaged power unit located
at the point of demand. While the technology is still
evolving, examples include fuel cells and photovol-
taic cells.
DNS Domain Name System. An Internet service that
translates alphanumeric domain names into numer-
ic IP addresses. For example, the alphanumeric do-
main www.silverspringnet.com translated
to its IP address through DNS is 64.207.187.4.
downstream / upstream Refers to the relationship
between devices along the route. Downstream re-
fers to moving toward a meter. Upstream means
moving toward an Access Point. See also child and
parent.
E
eBridge A Silver Spring device that routes between
an RF interface, an ethernet port and a serial port.