AT&C Losses in the Power Distribution Network
The word AT&C loss covers technical losses and commercial losses in which together contribute to revenue losses and hence required attention from the energy accounting point of view.
As electric current flows from the power plant by the transmission lines to the distribution segment, each element in the power system (e.g., a line or a transformer, etc.) offers resistance to it and the electrical energy is converted to heat energy, which is lost to the system. The cumulative energy lost through all the elements in a power system is categorized as Technical Loss.
Technical losses in the network occur on account of:
- Losses in conductors due to the conversion of electrical energy to heat energy (technically termed the copper losses or I2R losses);
- Transformer losses;
- overloading of existing lines and substation equipment;
- Poor maintenance and repair of equipment;
- Inadequate reactive compensation;
- Lack of modernization of old lines and equipment;
- Low HT: LT ratio, etc.
Low capital investment is also a main purpose for increase in technical losses in the power distribution sector.
Commercial losses in the network occur because of:
- Underperforming, Non performing and defective meters;
- Erroneous multiplying factors;
- Defects in circuitry;
- Non-reading of meters;
- Pilferage by manipulating or by-passing of meters;
- Tampering of meter reading by mechanical jerks, placement of powerful magnets or disturbing the disc rotation by foreign materials; and
- Theft by direct tapping.
These are all because of non-metering of actual consumption. Besides these factors, low accountability of employees, absence of energy accounting and auditing mechanisms also contribute to these losses. The sum total of "Technical" and "Commercial" losses is termed as T&D loss. It is the difference among the units input and units for those bills are raised.
T&D loss does not capture revenue losses on account of factors like as non realization of payment for the billed units because of purpose such as non-billing, defective billing and poor collection.
The aggregate of T&D loss and revenue loss is called as the "AT&C loss" (Aggregate Technical and Commercial loss). It is the difference among the units input within the system and units for that the payment is collected (payment realized).
Let us take an example to explain this point.
Example: Estimating AT&C losses
1. Units input 100 MU
2. Units billed 70 MU
3. T & D Losses 30 MU
4. Suppose revenue collection with reference to billed demand is - 90%
5. This means that out of 70 MU billed, payment is realised for 90% of 70 MU, i.e., for 63 MU
6. AT&C losses = 100 MU - 63 MU = 37 MU
So far you have learnt in which energy accounting is quite same to financial accounting: In the case of financial accounting, we measure the flow of funds through several ledgers and account books. In energy accounting, we measure the flow of energy at several points and maintain a record. Therefore, for proper understanding of the energy accounting mechanism you must also grasp the fundamentals of the metering, billing and collection system in the power distribution sector.