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 Remote monitoring technology will enable a utilities mangement system
that will automatically record metered consumption data for major utilities at
an activity and send data to a central PC. The PC will receive the data, and
automatically generate utility bills for tenants. In addition, remote
monitoring equipment installed at major steam, electric, compressed air, and
chilled water generating plants will provide detailed information on equipment
status and performance. This data, along with utility company cost and
consumption data, operations and maintenance personnel cost data, material
cost data, and other information, will be used to automatically generate
various analyses of utilities costs and performance. These analyses will
allow managers to make decisions that will result in optimized operations in
the present and future.
1.3.1 Remote Interfacing Kilowatt Meters. There are two reasons for
providing a kilowatthour meter with a pulse initiator. The pulse initiator
allows for monitoring of the load center on a temporary basis or collecting
remote data on a permanent basis. In either case, pulse initiators are
manufactured with a variety of output signal parameters and care must be taken
to ensure compatibility of components. For applications requiring a distance
between the pulse device and data collection point of over 50 feet, the signal
may require reinforcement. Increased voltage and the use of signal repeaters
are two common methods used. Do not attempt any signal manipulation without
first referring to the manufacturer's instructions of all equipment involved.
1.3.2 Transmission to TWO Points. The need to have data transmitted to two
remote points is frequently necessary in the wholesaling or custody transfer
of the commodity. In these applications, both the supplier and the end user
must have meter data readily available to them. Figure 10-5 depicts a means
of accomplishing the task with one telemetry transmitter. Figure 10-6 shows a
system with two data channels if the channels must be isolated.
1.3.3 Repeater Transmission. Repeater data transmission systems provide the
user with a relatively inexpensive means of sending data to a remote point, as
shown in Figure 10-7. Although repeaters accomplish the transfer of data from
local to remote points at a cost of approximately 10 percent of what other
transmission systems cost, they do have limitations. The primary
consideration when a repeater is contemplated is its requirement for a
dedicated wire pair. When using a repeater, no other signals may be on the
wire pair. Repeaters also have finite distance limitations, usually expressed
in ohms rather than distance, because the gauge of transmission lines varies.
Typically, a repeater system is limited to a maximum transmission loop
resistance of 4,000 ohms. Another means of data transmission is the use of a
modem through existing telephone lines which is cost effective since the cost
is only the price of a telephone call.
1.4 Computer Management. The system shown in Figure 10-8 usually requires
telemetry of data from a number of meters in a system, to a central point
where the data is converted into a computer compatible signal (RS-232C). In
this system, the computer continuously monitors the data lines. It
immediately warns the operator when a signal is not within programmed limits.
10-3
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