Meter Operation (Energy Limiting Mode) Released
25/35
Cashpower Gemini HMI
– User Guide
© Gyr (Pty) Ltd
11
Meter Operation (Energy Limiting Mode)
The Energy Limiting Mode of operation allows utilities to distribute a fixed amount of energy to
customers over a period of time (typically on a monthly basis). It encourages the rational use of
energy without severely inconveniencing customers.
11.1 Daily Allocation of Energy (DAE)
This is the amount of energy that a utility will allocate to a customer over a 24-hour period. The value
may be changed at any stage by entering a suitable set DAE token.
A
„daily‟ value was chosen to prevent confusion when accounting for months
having differing numbers of days. Reference to „months‟ elsewhere in this
document assumes a 30-day period.
11.2 Operation
Assume that a monthly energy allowance of 150kWh has been allocated to a customer. The Gemini
HMI meter allocates this energy in regular, equal portions, over a thirty-day period i.e. by incrementing
the kWh credit level with a value of 0.000870kWh every 15 seconds.
Assuming that the customer draws no power at all, the credit level will continue to increase. However,
as soon as energy starts to be used, the credit level is proportionately decremented. If the rate at
which energy is being used is less than the rate at which it is being incremented, the credit level will
slowly continue to increase. If the rate at which energy is being used is greater than the rate at which
it is being incremented, the credit level will slowly decrease. It is in the customer‟s interest to ensure
that electricity is not wasted and that unnecessary appliances are turned off. By conserving energy, it
will be possible to use it at a high rate for periods when required.
In the event of the customer exceeding the allocated allowance (credit level reduced to zero), the load
is disconnected. However, the next allocation of credit will be available within a very short period of
time (15 seconds) and the supply of electricity to the customer quickly restored. Providing the
customer takes immediate steps to disconnect unnecessary appliances, it will be possible to have at
least basic services available e.g. lighting. With a 150kWh monthly allocation of energy, it will be
possible to maintain a continuous load of 200W whilst still maintaining a positive credit balance.
Figure 12: Graphical representation of Energy Limiting Mode of operation
Timing for the dispensing of the DAE is synchronised to the mains supply
frequency. During a power failure the DAE does not continue to increment.
Accumulated
Energy
Accumulated Energy Less
Energy Used by Customer
Energy Used
by Customer
A
:
Customer starts using energy
B
:
Customer depletes accumulated
energy and load is disconnected
C
:
Customer starts using energy again
after load is reconnected
A : Consumer starts using energy.
B : Consumer depletes accumulated energy and is disconnected.
C : Consumer starts using energy again after reconnection.
0
500
1000
1500
2000
2500
3000
00
:0
0
02
:0
0
04
:0
0
06
:0
0
08
:0
0
10
:0
0
12
:0
0
14
:0
0
16
:0
0
18
:0
0
20
:0
0
22
:0
0
Time in hours
En
er
g
y
in
k
W
/h
B
C
A
