The Electrical Engineer - Institute of Integrated Electrical Engineers ...

TECHNICAL PAPER
Figure: 1 – Existing Distribution System Diagram of STG Building with Conventional
Sub-Meters
Figure 3 presents the proposed energy submeters
for the tenant offices of STG Building
Establishment. Each sub-meter is located inside
the office area which is accessible to each office
tenant in order that the prepayment meter with
prepaid energy user card can be accessed and
utilized conveniently. Each prepaid sub-meter is
protected with over-current protection to avoid
extensive damage of internal circuitry. Each
prepaid energy meters is connected through
the rerouted sub-feeder lines toward the panel
board. These prepaid sub-meters are then
connected and supplied by main feeder system
of the STG Building to individual panel board.
If a prepaid sub-meter is fully exhausted, no
power therefore is transmitted to the tenant’s
electrical panel. It may resume only when the
KW-HR denomination through energy user card
is reloaded once again.
Prepaid KW-HR Denomination
Figure 4 below demonstrate how a prepayment
energy system can be used by each tenant of
STG Building using a magnetic strip card to be
validated in a prepaid sub-meter. The strip card
is used to validate the “KW-HR prepaid card”
through the loading machine to be provided
by the landlord. Each tenant office will have
an allotted equivalent prepaid denomination
depending on operating energy. Table 1 presents
the different electrical load appliances typically
used by the tenant offices of STG Building while
Table 2 reflects the daily average energy usage
by the tenants. The energy usage is evaluated
based on the quantity of equipment and its
power rating in a given period of time based on
regular working hours per day and it is evaluated
using the equation hence, Total Energy Usage
(TEU) = No. of Units x Power Rating x (1/1000)
x Average Working Hours, Kw-hr.
30 THE ELECTRICAL ENGINEER MAGAZINE 3RD QUARTER 2010
Figure:2 – Concept Diagram for the Proposed Prepayment Energy Sub-
Metering System
Figure: 3 – Proposed Prepayment Energy Sub-Meters for Commercial
Establishment Designed with Multi-Tenant Offices and Rented Accommodation