Monitoring
The EPMS monitors the electric loads of major equipment. Inputs to the mon-
itoring unit can be current or potential transformers as well as other sensors or
monitoring devices. Current transformers are used to provide information
regarding electric current while potential transformers are used to provide
information for electric voltage meters.
Typically the monitoring units are microprocessor based, have onboard
memory, and can be programmed or have preset factors for monitoring, test-
ing, and reporting sets. Some monitoring units can display locally and/or com-
municate via the EPMS network.
The monitoring unit may have inputs for specific distribution components
such as electrical breakers. Addressable relays may be used for sensing and
the monitoring of devices where information is simply in an open/closed or
on/off state. The monitoring of critical equipment such as switchboards and
switchgear may include digital metering and the capability to monitor power
quality. For power quality most EPMS implementations adhere to the IEEE
categories for power quality problems, including sags, swells, harmonics,
interruptions, under- and over-voltages and transients.
Display Units
Display units typically connect to the monitor of an electrical load or equip-
ment. The displays can be local, specific to particular equipment, or allow
for viewing and monitoring of multiple loads and devices. Some larger display
units may connect to multiple monitors and are able to communicate with an
operator’s workstation via a standard data network.
Central Operator Workstation
A central operator workstation for the EPMS is usually a personal computer
with special application software. It uses data from the system components
to analyze and take action regarding power usage in a facility. The operator
workstation can have the following features:
n Distribution system graphics
n Real-time reports
n Trend reportsElectric Power Management Systems 61