Data processing: financial – business practice – management – or co – For cost/price – Utility usage
Reexamination Certificate
1999-09-02
2001-04-17
Trammell, James P. (Department: 2161)
Data processing: financial, business practice, management, or co
For cost/price
Utility usage
C340S870020
Reexamination Certificate
active
06219655
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the metering of the consumption of electrical energy. More particularly, the present invention relates to providing advanced metering functions when power is temporarily lost at the meter.
BACKGROUND OF THE INVENTION
The advanced metering functions that must be accommodated by a radio frequency (RF) transmitting meter include both demand and time-of-use metering. A review the basics of both demand and time-of-use metering is provided by way of background.
With respect to demand metering, the following paragraph comes from the Handbook for Electricity Metering, Edison Electric Institute:
“Kilowatt demand is generally defined as the kilowatt load averaged over a specified interval of time. The meaning of demand can be understood from
FIG. 1
, which shows an example power curve over time. In any one of the time intervals shown, the area under the dotted line ‘demand’ is exactly equal to the area under the power curve. Since energy is the product of time and power, either of these two areas represents the energy consumed in the demand interval.
The equivalence of the two areas shows that the demand for the interval is that value of power which, if held constant over the interval, will account for the same consumption of energy as the real power. Demand can then be defined as the average of the real power over the interval.”
Referring to
FIG. 1
, the horizontal axis is time and the vertical axis is units of power in kilowatts (kW). Typical electric meters record consumption in units of kilowatt-hours (kWh), which is an energy value. For instance, in a first case an electrical meter would register one kWh consumption if one kW were used constantly for one hour. Similarly, in a second case the meter would show one kWh consumption at the end of an hour if two kW were used constantly for the first half hour with no energy used in a second half hour. Finally, in a third case the meter would also show one kWh consumption at the end of an hour if twelve kW were used constantly for the initial five minutes of the one hour interval and no energy was used in the remaining 55 minutes.
FIG. 1
illustrates the foregoing over four demand intervals having a varying power curve. Demand is the area under the dotted line in each of the demand intervals. The area under the dotted line equals the area under the power curve equals total energy for the interval. Demand then for each of the four demand intervals equals the average power over the individual demand intervals.
The aforementioned three cases are depicted in Table
1
. The bottom entry in Table 1, labeled “Electric Meter Value Registered at End of Time Period”, shows the increase in consumption which would be recorded on the electric meter at the end of each hour for each of the three cases presented. All of the three cases. are shown to have the same consumption. From a pure consumption point of view all cases would then have the same electric bill for the one hour demand interval.
TABLE 1
Scenarios Showing Consumption Recorded by an Electric
Meter for Different Power Levels and Times of Usage
Case 1
Case 2
Case 3
Constant Power Level
1 kW
2 kW
12 kW
Time at Constant Power
60 minutes
30 minutes
5 minutes
Usage
Time at Zero Power Usage
0 minutes
30 minutes
55 minutes
Total Time Period Evaluated
1 hour
1 hour
1 hour
Electric Meter Value
1 kWh
1 kWh
1 kWh
Registered at End of Time
Period
Demand billing is related to demand as distinct from the aforementioned consumption billing. The electric utility must be geared to meeting demand, not just average consumption. There are a number of different types of demand billing. Block demand is a frequently used form of demand billing. Referring to
FIG. 2
, time is displayed on the horizontal axis and power is displayed on the vertical axis. As displayed on the horizontal axis there are four intervals, A-D, that comprise a single block. Block demand calculates demand over the intervals A-D comprising the block. Consumption is recorded over the interval and divided by a time period, in hours, that the interval comprises. Repeating this for all the intervals in a block would allow billing based on the average demand over the block. Most often, however, the maximum demand is billed for the entire period of the block.
FIG. 2
illustrates the demand for each interval as being indicated by the area under the dashed line. In practice, the maximum demand, depicted in interval C, is the demand that would be billed to the customer over the entire period comprising the block.
Rolling demand is another frequently used form of demand billing. Rolling demand may be thought of as a sliding window of block demands. As indicated in
FIG. 3
, for rolling demand the time scale on the horizontal axis is still divided into individual intervals. However, the time scale is further divided into At sub-intervals, as depicted. Instead of calculating the demand at the end of each at interval, the calculation is performed by -adding the consumption for a set number of sub-intervals and then dividing by the time period, in hours, of the composite interval. Rolling demand permits greater accuracy in demand billing. Total demand, average demand, maximum demand, and average maximum demand during a full interval are all types of demand billing that are supported by calculating rolling demands. Once the rolling demand is known, any of the aforementioned types of demand billing-may be used.
Table 2 presents the same three cases as previously presented with respect to Table 1. Assuming that the demand sub-interval for billing is five minutes, the demand over the total hour billing period would be calculated for each interval with each interval being comprised of three successive five minute periods. Over the whole billing period, all demand value from these intervals will be compared with the largest one being used for billing purposes. As depicted in
FIG. 3
, the maximum demand is calculated in the eighth interval from the beginning of the one hour time period.
TABLE 2
Scenarios Showing Consumption and Demand Recorded by an
Electric Meter for Different Power Levels and Times of Usage
Case 1
Case 2
Case 3
Constant Power Level
1 kW
2 kW
12 kW
Time at Constant Power
60 minutes
30 minutes
5 minutes
Usage
Time at Zero Power Usage
0 minutes
30 minutes
55 minutes
Total Time Period Evaluated
1 hour
1 hour
1 hour
Consumption Value
1 kWh
1 kWh
1 kWh
Registered at End of Time
Period
Demand Interval Period
5 minutes
5 minutes
5 minutes
Max Consumption During
1 kWh
2 kWh
12 kWh
Interval
Maximum Demand Recorded
12 kW
24 kW
144 kW
at End of Time Period
To find the maximum demand calculation for the same three cases that were presented with reference to Table 1, assume that the time interval commences at the start of the hour. With twelve distinct five minute demand sub-intervals throughout the hour, demand for each interval must be calculated. The calculations for the cases presented in
FIG. 2
are simple since an assumption of level power consumption is made.
For case
1
, each of the twelve minute sub-intervals would have the same demand value of 12 kW. Accordingly, the maximum demand for this case is 12 kW and the billing would be for 12 kWh.
For case
2
, six of the intervals have a demand value of 24 kW while the remaining six intervals have a demand of 0 kW. So, for case
2
, the maximum demand is 24 kW over the entire period of billing and the billing would be for 24 kWh.
For case 3, only one of the five minute intervals has a demand value of 144 kW. The other eleven have 0 kW demand. Accordingly, the maximum demand in this case is 144 kW and the customer would be billed 144 kWh for the hour.
The bold text in Table 2 compares the different billing approaches. From a straight consumption perspective, all three cases are billed the same as indicted in Table 1. However, when the demand is billed, it is clear that a maximum demand
Myers Gregory K.
Schleich Michael G.
Dixon Thomas A.
Itron, Cin.
Patterson Thuente Skaar & Christensen P.A.
Trammell James P.
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