TYPES OF METER RELATED PROBLEMS IN POWER SYSTEM PART 2

Continuation of the types of meter related problems which causes power loss.

Misrecorded Meter Multipliers

One serious problem that sometimes occurs on metering and billing systems is that the meter multiplier is not properly recorded by the billing system. For example, if the correct multiplier is 120 and the billing system has it recorded as 80, both demand and energy billings for the involved consumer will be only two-thirds of the correct amount. Furthermore, this error will not be a one-time occurrence, but will persist month after month, year after year.

The potential for loss of revenue resulting from incorrectly recorded multipliers is so great that it is recommended that the distributor check on a two-year rotation every meter multiplier recorded on the billing system against the multipliers marked on the actual meter for all meters that use multipliers.

Misapplied Rate Schedules

Billing errors are still possible even after it is ensured that the correct kWh and kW meter readings reach the billing computer. It is possible that the billing computer is misprogrammed on the application of the appropriate rate schedules to the power and energy readings.  This possibility becomes more likely as the distributor’s rate schedules become more mathematically complicated.

It is not necessary to engage computer programmers to check existing systems. Checks can be made by taking a sample of billings, representing all types of consumers, and calculating the dollar charges from the meter readings by using a hand calculator and a copy of the rate schedules. This simple procedure could identify errors that might be causing a great amount of revenue loss. It should never be assumed that a computerized system is working properly unless it is thoroughly and repeatedly checked.

Since misapplied rate schedules can result in a very large loss of revenue, all schedules should be checked annually for proper implementation. Furthermore, all schedules should be checked the first month of implementation after any change in billing software has been made.

Low Demand Resolution

Low demand resolution results from unnecessarily large meter multipliers and from the meter demand register format. Large meter multipliers force the meter reading to be low for a given kW demand. The important Features of a kWh-Demand meter. For example, an actual demand of 62 kW reads 0.51 for a multiplier of 120 and 1.55 for a multiplier of 40. However, these two meter readings produce two different billing demands;

Meter Reading  x Meter Multiplier = Billing Demand

The lower meter multiplier improved the demand resolution and, as a result, increased the billing demand by 1kW. This is not only more accurate but also will improve the distributor's revenue. This will always be the case since demand register readings are rounded to the next lower digit. Since demand registers are reset each month, lost demand revenue is never recovered in later months.

In addition to providing better demand resolution, the smaller and lower-priced current transformers (CTs) reduce the installed meterig cost.

The appropriate CT size should be the smallest ratio that limits the meter (secondary) current to 10amperes or less without exceeding the CT thermal rating. With modern CTs, this is in the range of 10-15 amperes. The distributor will also need to verify that the actual load current does not exceed the CT current rating.

A second method for improving demand resolution on transformer-rated installations is to charge the demand register from XX.X to X.XX. A format of XX.X only provides resolution of 0.1kW. A format of X.XX provides a resolution of 0.01kW, and consequently eliminates a demand loss of 0.09kW times the meter multiplier. For meter multipliers raging from 40 to 1,200 this demand loss ranges from 3.6kW to 108kW. This demand loss translates to a revenue loss. For example, if a meter multiplier of 120 is applied to a reading of 2.5 and 2.59, the resulting billing demands are 300kW and 310kW. The higher-resolution reading increases the billing demand by 10kW.

Electronic Meters

High-accuracy electric meters increase revenue by reducing the amount of under-recording that is typically calibrated into meter to avoid over-recording when a meter happens to operate on the fast side of its accuracy band. In recent  years, electronics has been playing a greater role in the electric metering field for this and other reasons. There are two general categories of electronic meters.

Meters of the first category are normal electronmechanical meters that are equipped with electronic registers in place of the mechanical dial registers. These electronic-register meters achieve greater accuracy mostly by improved register resolution. Electronic-register meters are well-proven devices based on many years of satisfactory field performance. The cost of these devices tends to be somewhat higher than that of electromechanical meters, so this should be considered when evaluating the overall economics associated with their use.

The second category of electronic meters consists of meters of a completely solid-state design that encompasses the metering module as well as the register. Fully solid-state meters are still in the early stages of implementation. They are not recommended for widespread use by distributors until they accumulate more years of satisfactory field performance. The cost of fully solid-state meter is significantly higher than that of an electromechanical meter. Nevertheless, fully solid-state meters can be the metering device of choice for many specialty situations.

Poor Meter Security

For many distributors, there may be an alarming lack of meter security. Many demand meters may not have a seal installed on the demand reset. Also, a significant percentage of meter bases might not be sealed. Lack of meter security allows anyone to reset the demand register and to tamper with the meter. Resetting the demand register can result in lost revenue, particularly if the register is reset just before a meter reading day. A knowledgeable person tampering with the meter can slow dthe disk revolutions ormake the meter run backwards. In both cases, the meter will register an incorrect kWh reading and reduce the distributor’s revenue. To discourage meter tampering, all meter bases should be sealed with an employee-identified seal. Each month, the meter reader should check for signs of tampering. In addition, all demand resets should be sealed.

TYPES OF METER RELATED PROBLEMS IN POWER SYSTEM PART 1