EMA Outcome 3 PDF

OUTCOME 3 Discuss the different losses in transmission and distribution system, demand side management and harmonics  Assessment of Transmission and Distribution (T&D) Losses in Power Systems For an electric utility the distribution losses which are more predominant, can be categori...

OUTCOME 3 Discuss the different losses in transmission and distribution system, demand side management and harmonics  Assessment of Transmission and Distribution (T&D) Losses in Power Systems For an electric utility the distribution losses which are more predominant, can be categorized as ❑Technical Losses ❑Commercial Losses  Technical Losses The technical losses primarily take place due to the following factors Transformation Losses (at various transformation levels) High I2R losses in distribution lines due to inherent resistance and poor power factor in the electrical network  Estimation of Technical Losses in Distribution System The first and important step in reduction of energy losses is to carry out energy audit of power distribution system. There are two methods of determining the energy losses namely ✓direct method and ✓indirect method.  Direct method ▪ Involves placement of energy meters at all locations starting from the input point of the feeder to the individual consumers. ▪ The difference between input energy and sum of all consumers over a specific duration is accounted as distribution loss of the network. ▪ This calls for elaborate and accurate metering and collection of simultaneous data.  The Indirect method essentially involves: Energy metering at critical locations in the system such as substation and feeders. Compiling the network information, such as length of the line/feeders, conductor size, DTR details, capacitor details etc. Conducting load flow studies (all electrical parameters) on peak load durations as well as normal load durations. Application of suitable software to assess the system losses. This software can also be used for system simulation, identifying improvements and network optimization.  Causes of technical losses in distribution system The factors contributing to the increase in the distribution losses are ❖Lengthy distribution lines ❖Inadequate Size of Conductors ❖Distribution Transformers (DTR) not located at load center on the Secondary Distribution System ❖Low Power Factor  Lengthy distribution lines: In practice, 11 KV and 415 volts lines, in rural areas are extended radially over long distances to feed loads scattered over large areas. This results in high line resistance and therefore high I2R losses in the line. Inadequate Size of Conductors: On account of load growth, many distribution feeders end up being under sized for the loads to be catered to the consumers. The size of the conductors should be selected/upgraded/transformers to be relocated on the basis of KVA Kilometer capacity of standard conductor to maintain voltage regulation within limits.  Distribution Transformers (DTR) not located at load center on the Secondary Distribution System: Often, DTs are not located centrally with respect to consumer loads. Consequently, the farthest consumers receive low voltage even though a good voltage level is maintained at the transformer's secondary. This again leads to high line loss. Therefore in order to reduce the voltage drop in the line to the farthest consumers, the distribution transformer should be located near to consumer load to keep voltage drop within permissible limits.  Low Power Factor: A low PF contributes towards high distribution losses. For a given load, if the PF is low, the current drawn is high. Consequently, the losses which are proportional to square of the current will be more. Therefore, line losses owing to the poor PF can be reduced by improving the PF. This can be done by application of shunt capacitors. Shunt capacitors can be connected in the following locations: ✓On the secondary side (11 KV side) of the 33/11 KV power transformers in substation. ✓On the secondary side of distribution transformers  The following example shows how the improvement in power factor in 11 KV lines results in considerable reduction in losses: Reduction of Line Losses with improvement in Power Factor Load (kW) PF kVA Current (A) Line Loss (kW) Remarks 300 0.7 428 38.9 27.2 Before 300 1.0 300 27.2 13.4 After