Solid-State Revenue Meters

[meterman3]

I would like to replace all the electromechanical residential meters (1600ish) in our system most 20+ years old. I have been asked what the approximate payback period is. Has anyone had first-hand experience with this or have an idea of a average accuracy increase. I realize there are many variables here but just looking for a ballpark figure.

 

[davidbeach]

In terms of terminology, I believe you want a numeric meter rather than a solid state meter. I believe that we can classify meters the same way relays are classified; a progression from electromechanical to solid state to numeric. Most solid state relays are now considered obsolete. As a quick reference, in an electromechanical device the AC analog quantities do something, turn a disk, resist the turning of a disk, etc. In a solid state device, the AC analog quantities are rectified to DC, filtered (either before or after rectification) and operated on using comparators. In a numeric device, the AC analog quantities are digitized and assigned numeric values; all operations are mathematical equations. Numeric is often referred to as microprocessor, but that can be misleading as some solid state relays include microprocessors for some functions but do not have numeric representations of the system values.

As far as payback, if you're successful at keeping your electromechanical meters calibrated and all you want from the new meters is the same old stuff there won't be any payback to speak of. But if you want to do something else, like automatic meter reading or providing fancy usage snapshot graphs to the customers, then the meter replacement payback calculation must include the value of those benefits. The elimination of the whole meter-reading department could make for a short payback period, but if you're going to still be manually reading each meter, the payback may well be negative.

 

[itsmoked]

As with all meters there is usually an industry legal statement about the accuracy the revenue payer is expected to accept. +/-X%.

Modern meters are often made with newer tech that greatly increases the available accuracy. Knowing this the entities using the meters to charge their customers try to have the meters use whatever part of X% their new meters can offer-up by offsetting their meter herd to reap/harvest/steal that extra percentage.

As an example if the legal limit is 2% overage and the new meters are accurate to 0.5% you can bet the new meters are offset to read 1.5% over which still keeps the readings "legal" via the outdated and never updated original error statement. Depending on your situation you could always use this legal ruse to "payback" the meters.


Keith Cress
kcress -

http://www.flaminsystems.com