|
| DISCLOSURE |
| WHAT IS SMART GRID |
| HISTORY OF SMART GRID |
| DIFFERENCE BETWEEN SMART METERS AND THE SMART GRID |
| SYSTEM RELIABILITY AND THE SMART GRID |
| DISTRIBUTED RENEWABLE GENERATION AND THE SMART GRID |
| ELECTRICITY STORAGE AND THE SMART GRID |
| ELECTRIC VEHICLES AND THE SMART GRID |
DISCLOSURE GREEY EPC is under contract with S&C Electric Canada Ltd. The information
on this website has a full bias towards the products and approaches offered by S&C Electric and should not be considered objective.
Many of the Smart Grid solutions discussed here are based on North American
electrical systems and are not particularly applicable elsewhere. |
WHAT IS SMART GRID Smart Grid is the term used to talk about intelligence being added to the
electrical power system. The electrical power system is often referred to as
a "grid". It consists of three major parts;
generation, transmission and distribution. Generation and transmission are
not connected as a "grid" but are often included in Smart Grid
discussions.. |
HISTORY OF SMART GRID I
personally believe that the Smart Grid began in 2005 when the DOE (US Department of Energy),
after working closely with industry partners such as IBM, formalized the term. Smart Grid came after Smart
Meters and Smart Homes and sometimes the public is confused as to what the difference is.
Utilities do not change quickly
and for a good reason. The primary
goal of many utilities is to have a cost effective reliable electric system.
There is a risk
to this goal by
adopting change too quickly. Understandably utilities did not fully embrace
the Smart Grid
initially. To expedite this the US government created a $4.2 billion
Smart Grid fund to incent US utilities into beginning Smart Grid projects
more quickly. Canada also created a $400 million Smart Grid fund to incent
Canadian utilities to begin Smart Grid projects. Ten years later many utilities
in North America have acknowledged the value of Smart Grid and have
implemented many Smart Grid solutions. |
DIFFERENCE BETWEEN SMART METERS AND THE SMART GRID
Customers are connected to the electrical power system with a meter. The
electrical meter was invented well over a hundred years ago and was based on
electro mechanics. This meter is like an electric motor. The
more electricity that is used, the faster the meter spins and the higher the
bill. Electro mechanical meters are quite accurate and reliable.
The problem is that these meters are read manually. Consequently billing
cycles are long. Meters have to be read and then
the readings are manually
entered into a billing system.
Electromechanical meters are also not able to handle
TOU (Time Of Use) billing. TOU billing works by charging different electricity
rates depending on the time of use.Ideally when the system is at its peak load,
electricity should be expensive.Conversely when there is excess generation, electricity rates
should be less expensive.
TOU is used to match the load to the generation to
increase the efficiency and reduce the
total cost of the electrical system.By design
it also gives electricity customers an opportunity for more control over their electricity
bill.
Smart meters are able to provide very accurate TOU meter reads directly
to the billing system. As the meter readings can be sent directly
through wired or wireless communication to the billing system computer.
This
speeds up the entire process and eliminates errors.
However, neither automatic meter reading nor TOU billing are considered part of
the Smart Grid. The value to the Smart Grid of Smart Meters is the
additional data provided by the Smart Meters. Today's advanced Smart
Meters can provide very accurate "power quality data", "reliability data" plus
remote disconnect/reconnect capability in addition to remote TOU meter reads.
Thus Smart Meters are considered a nice addition to a Smart Grid but not
actually part of the Smart Grid.
|
SYSTEM RELIABILITY AND THE SMART GRID Most
transmission and generation systems are fully redundant such that a single
isolated fault will not cause an interruption to customers. Conversely,
large transmission or generation issues can affect large numbers of customers. Consequently generation and
transmission interruptions are normally not included in reliability statistics.
System reliability indices are normally only based on the distribution system's
performance.
An electrical utility's
reliability is measured using two industry specific indices: SAIFI (System
Average Interruption Frequency Index) and SAIDI (System Average Interruption
Duration Index) which are then combined into CAIDI (Customer Average
Interruption Duration Index). A good SAIFI value would be 2 times.
This indicates that on average, across the system, every customer
has had two
power interruptions. A good SAIDI value would be 100 minutes. This
indicates that on average across the system customers were interrupted for 100
minutes. These are combined with CAIDI such that customers had an average
interruption of 50 minutes, 2 times. However, these are averages
and are actually quite misleading.
Electric utilities are only now moving towards being
able to measure reliability on a customer by customer basis.Unlike the
telephone system for example, it is not possible to say that a cutomer has "four
nines" reliability or 99.99% telephone availability. The reason for this
is that the typical Canadian urban distribution utility only experiences interruptions on
roughly a third of the system. The other two thirds of these systems
are very reliable due to underground construction and short protected lines.
Consequently a SAIDI of 100 minutes is actually closer to 5 hours of
interruption a year for the customers that had interruptions. The best way
to improve distribution reliability, although an expensive solution, to
bury the cables and thereby protect it from outages.This is often the
case in the
downtown areas of major cities where the power never goes out.
In Canada, if an interruption
is less than a minute it is considered a momentary outage and is not included in
the SAIDI and SAIFI indices. This is because the majority of faults on the
overhead distribution are transient and will self-clear by simply reclosing.
Reclosing is like turning the circuit back on. This practice of
reclosing has been used for over 70 years and creates
momentary outages.This is also one of the best ways of decreasing SAIDI
and SAIFI. |
DISTRIBUTED RENEWABLE GENERATION AND THE SMART GRID A primary
role of Smart Grid is as an enabler for small, distributed, renewable generation such as
photovoltaics or solar panels, wind and small hydro.
Today's power system is fundamentally designed to have large remote generating
facilities feeding the load. This is often from remote locations.
The generation is connected to High Voltage Transmission to reduce losses and
deliver large amounts of power over long distances. The high voltage
transmission requires large insulators on high towers travelling down wide
corridors. The Transmission then connects to large transformer substations
which then transforms the voltage down to levels that can be distributed to
customers on poles or underground on main streets or roads. A final
pole-mounted or pad-mounted transformer is then used to reduce the voltage to
the 120 Volts used by the customers. The challenge then becomes to connect
the solar panels to the 120 Volts. This portion of the system was designed
to be supplying load not supporting generation. Such
that there is little
impact at the 120 volt level but large amounts of local generation
can create problems on the distribution system. |
ELECTRICITY STORAGE AND THE SMART GRID Until recently there was no
way of storing large amounts of electricity. Electricity
needs to be produced when it is consumed.
In
2006, AEP installed North America's first large battery and it is still operating.Featuring a 1 MW (Million Watts) inverter and 5 MWH (Million
Watt Hours). Almost enough power to run a million homes for an hour in
Canada. Although the technology was not inexpensive, this originally appeared to be a
real solution to the intermittent nature of solar and wind generation plus a
simple way to match the load to the generation.
For utilities electricity storage is ideal. The customer buys 10-15% more power
than is needed due to the inefficiencies of the battery and inverter. If TOU is
in place, the customer either pays less to buy it at a good time for the utility
or pays a premium to buy it at a convenient time for the customer.
Despite the huge expectation that utilities would install electricity storage
across all of their systems many utilities still have very little storage on their
system. The value of Electricity Storage to the Smart Grid is still not
well understood. |
ELECTRIC VEHICLES AND THE SMART GRID Electric vehicles require electricity storage typically batteries charged from the grid. From a
Smart Grid standpoint, electric vehicles provide a new load for utilities and
electric vehicles demand a much better reliability than many conventional loads.
Where large numbers of electric vehicles are tightly clustered on the system,
distribution utilities may need to make significant changes and improvements to
their systems and Smart Grid will be part of the solution. |
Return to top |