What are losses in Electrical Power Systems?

What is loss?

Due to the various issues or unwanted effects such as heating of components, parasitic elements effects, skin effects, transformer core, etc, there will be power lost in electrical, electronic, or in power systems. There will be power loss that occurs while transmission of electric power through lines.

Apart from the above-mentioned issues, sometimes there is a chance of non-technical loss that affects the revenue and profits of the company. Non-technical losses include electricity used not being paid for, theft, tampering of meter, false meter readings, etc. Technical and human errors in meter readings, data processing, and billing can occur, resulting in over-or under-charging.

Types of Losses

Losses are classified into two types. They are

a) Technical Losses

b)Non - Technical Losses

Technical Losses

Technical loss occurs due to the energy scatter in the elements used in the equipment such as conductors, resistors, etc, materials used in transmission lines, transformers, distribution lines, and magnetic losses in transformers. Due to the technical loss, around 22.5% loss occurs and it directly depends on the characteristics of networks and operation modes.

In the power systems, major losses occur in primary and secondary distribution lines. Approximately 30% of total loss is carried out while transmission and sub-transmission lines. As a result, the primary and secondary distribution systems must be properly planned to ensure that they remain within limits. The unexpected increase in load resulted in an increase in technical losses above the normal level. Losses are unavoidable in electricity distribution and cannot be eliminated.

Types of Technical Losses

Technical losses are again classified into two types. They are

  • Permanent / Fixed Technical Losses
  • Variable Technical losses

a. Permanent / Fixed Technical Losses

Fixed losses on a network can be influenced in the following ways:

  • Corona Losses
  • Leakage Current Losses
  • Dielectric Losses
  • Open-circuit Losses
  • Losses due to the continuous load of measuring elements
  • Losses due to the continuous load of control elements

(b) Variable Technical losses

Not like permanent loss, variable technical losses differ with the amount of current transmitted. Variable loss is directly proportional to the square of the current flowing. We can reduce the losses by adding the cross-sectional area of lines and cables for a given load. As a result, there is a direct trade-off between the cost of losses and the cost of capital expenditure. It has been proposed that the optimal average utilization rate on a distribution network designed to account for the cost of losses could be as low as 30%.

Variable losses on a power network can be influenced in the following ways:

  • Joule losses
  • Impedance losses
  • Due to Contact resistance

What are the main reasons for Technical Losses?

The main reasons for technical losses are

  • Distribution lines length
  • Size of conductors
  • Fixing of Transformers away from Load Centers
  • Power Factor
  • Poor Workmanship
  • Feeder Phase Current and Load Balancing
  • Load Factor Effect on Losses
  • Transformer Sizing and Selection
  • Balancing Three Phase Loads
  • Switching off Transformers

Lengthy Distribution lines

The amount loss increases with the increase of distribution lines. That means the length of distribution lines is directly proportional to the amount of loss in power.

  • In rural areas, normally used 11KV lines are extended over long distances to make connections over large areas. The primary and secondary distribution lines are largely radial and typically extend over long distances. This causes high line resistance and, as a result, high losses in the line.
  • Unpredictable expansion of lines

Wrong size of conductor

Make sure the size of the conductor used in transmission lines should be based on the KVA x KA capacity of the conductor. The size of the conductor should be adequate. The wrong size conductor increases the losses while transmitting power.

Transformer away from load centers

On the secondary distribution system, distribution transformers are not located at the load center. In most cases, distribution transformers are not centrally located in relation to consumers. As a result, even though a good voltage level is maintained at the transformer’s secondary, the farthest consumers receive an extremely low voltage. This results in increased line losses. The cause of increased line losses is a result of lower voltage at the consumer end. As a result, in order to keep voltage drop within allowable limits in the line to the farthest consumers, the distribution transformer should be located at the load center.

Power Factor

The power factor in most LT distribution circuits lies between 0.65 to 0.75. A low power rate leads to high power loss. When the power factor is low, the current drawn in high and power losses is proportional to the square of the current will be more. So, we can reduce the losses by increasing the power factor. This can be done by using shunt capacitors at various points in transmission lines.

Poor Workmanship

Poor workmanship or bad workmanship leads to high distribution loss. The number of joints increases the power loss, so the number of joins always should be kept to a minimum. Make sure the proper joining techniques were used while installing distribution lines. Various connections like connection to the transformer bushing item, fuse, isolator, LT switch, etc should be checked at regular intervals, and take necessary steps to avoid sparking and heating due to contacts.

Feeder Phase Current and Current Balancing

Current (Load) balancing is considered one of the easiest and simplest ways to reduce power loss in three-phase circuits. Feeder phase balancing also tends to balance voltage drop between phases, resulting in less voltage unbalance for three-phase customers. The magnitude of the current at the substation does not guarantee that the load is balanced throughout the feeder length. Feeder phase unbalance can change throughout the day and with the seasons. Feeders are considered “balanced” when the magnitudes of the phase currents are within a factor of ten. Similarly, balancing load among distribution feeders will reduce losses if the conductor resistance is the same. This may necessitate the installation of additional switches between feeders to allow for proper load transfer.

Load Factor Effect on Losses

Consumer power consumption differs day by day and over seasons. In residency, the usage of power is high in the evening time (peak time) and in the summer seasons. In commercial buildings, the usage becomes high in the afternoon.

The variation of the load is called load factor and it varies from 0 to 1.

Load Factor=Average load in a specified time period/peak load during that time period.

Energy losses and lower power can be reduced by increasing the load factor, which, evens out feeder demand variation throughout the feeder.

Size of transformer

we use a copper conductor to induce a magnetic field into a grain-oriented steel core in a distribution transformer. Due to the copper conductor, the transformer will have both load loss and no-load cross loss. The copper loss in the transformer differs with load based on the resistive power loss (Ploss = I2R).

When a transformer is energized, it experiences no-load excitation loss (iron loss) due to a changing magnetic field in the core. Although core loss varies slightly with voltage, it is essentially constant. The fixed iron loss is determined by the transformer core design and the molecular structure of the steel lamination. Core losses have been reduced as a result of improved steel core manufacturing and the use of amorphous metals (such as metallic glass).

Balancing Three Phase Loads

We can reduce the loss by balancing three-phase loads regularly throughout a network. It is relatively simple to implement on overhead networks, and thus offers significant potential for cost-effective loss reduction if appropriate incentives are provided.

Switching off Transformers

Can reduce fixed loss by turning off transformer when the demand is low.

For ex: Assume there are two identical transformers are required at the sub-station during peak hours and only one is required when the demand is low, so the operator can turn off the one transformer to reduce fixed loss. This may lead to the origin of some offsetting and it may affect the security and service quality and the operational condition of the transformer too. However, unless the cost of losses is considered, these trade-offs will not be explored and optimized.

Other Reasons for Technical Losses

  • Leaking and power loss
  • Overload in lines
  • Anomalous operational conditions
  • Low voltage
  • Poor quality of instruments
  • In the L.T system, unequal load distribution among the three phases causes high neutral currents.

Non-Technical / Commercial Losses

Non-technical losses are related to meter reading, defective meters and meter reading errors, billing of customer energy consumption, lack of administration, financial constraints, estimating unmetered energy supply, and energy thefts.

Main Reasons for Non-Technical Losses

  • Power Theft
  • Metering Inaccuracies
  • Unmetered Losses for very small Load
  • Unmetered Supply
  • Error in Meter Reading
  • Billing Problems

Power Theft

Power theft of energy delivered to consumers is not calculated by the energy meter. Customers bypass the energy meter by different methods like mechanical jerks, placement of a strong magnet near to meter, stopping the meter by using remotes, etc.

Metering Inaccuracies

Metering inaccuracies are defined as the difference between the total energy delivered and the total energy calculated by the meters. All meters have some inaccuracies. Metering inaccuracies are rapidly decreased by the development of advanced digital meters. Due to this, the rate of changing mechanical meters to advanced digital meters increases.

Unmetered Losses for very small Load

Unmetered losses occur when energy consumption is estimated rather than measured with an energy meter. This occurs when the loads are very small and the installation of an energy meter is economically impractical. Streetlights and cable television amplifiers are two examples of this.

Unmetered Supply

Unmetered supply is one of the main problems faced by companies. Usually, companies sanction the power loads depending upon the instruments used in commercial places. Once the owner got the sanctions from the concerned authority, the consumers increase their connection load without informing the authorities.

What are the methods for reducing technical losses?

  • Converting LV Line to HV Line
  • Give direct Line from Feeder
  • Adopting High Voltage Distribution Service (HVDS)
  • Adopting Arial Bundle Conductor (ABC)
  • Reduce the Number of Transformers
  • Utilize Feeder on its Average Capacity
  • Replacements of Old Conductor or Cables
  • Feeder Renovation / Improvement Program

Converting LV Line to HV Line

Actually, many low voltage lines in town are surrounded by feeders with high voltage. At lower voltages, more conductor current flows for the same amount of power delivered, resulting in higher I2R losses. Changing old LV lines to higher voltage costs high. However, installing multiple step-down transformers in the 430-volt area helps to reduce the copper loss by injecting load current at many points (That is, lowering the overall conductor current and the distance the current travels to serve the load.)

Install direct line from the feeder for large users

Arrange a dedicated transmission line network for large users that helps to give direct power from the feeder.

Adopting High Voltage Distribution Service (HVDS)

HVDS has lower distribution losses due to shorter distribution lines, a high-quality power supply with no voltage drops, less motor burnout due to less voltage fluctuation, and good power quality to avoid transformer overloading.

Adopting Arial Bundle Conductor (ABC)

LT lines are unavoidable actually, so in those cases install ABC (Arial Bundle Conductor) to reduce the faults in the line that also prevents theft (tampering of line).

Reduce Number of Transformers

  • Minimize the number of transformation steps
  • Transformers play a major role in network loss.
  • Install high efficient transformer can reduce the distribution losses

Utilize Feeder on its Average Capacity

Distribution losses will be high if the distribution feeder overloads. The load on power is directly proportional to the variable loss which means If the load on a power line is high, then the variable loss amount also increases. So, don’t overload the feeder.

Replacements of Old Conductor or Cables

The higher the cross-section area of the conductor/cable, the lower the losses, but at the same time cost will be high. As a result, by forecasting future load, an optimal balance between investment cost and network losses can be maintained.

Feeder Renovation / Improvement Program

  • Change the transmission and distribution line based on load.
  • Improving the line strength of area with high distribution loss
  • Minimize the LT line’s length by implementing new substations and distribution transformers
  • Implement distribution transformer with lower capacity at each consumer premises against cluster formation.
  • To improve power factor, install shunt capacitors
  • Install advanced digital type transmitter instead of old sluggish meters
  • Separate lines for both rural and industrial feeders
  • Implement new armored cable instead of old service cable
  • By renovating feeder, can reduce T&D loss to 20% from 70%.

What are the methods to reduce non-technical losses?

The methods to solve non-technical losses are

  • Collect data from distribution lines
  • Execution of energy audit program
  • Power theft detection drives are used to reduce power theft.
  • Billing issues rectification
  • Meter reading issues rectification

Distribution Line’s data/ Mapping

  • Make a data of all distribution systems (primary and secondary) with all parameters like the size of the conductor, line length, etc.
  • Mapping of data includes loads, operating conditions, expected loads forecast, etc.
  • Long-term plans for phased strengthening and improvement of distribution and transmission systems are being developed.

Energy Audits Schemes Implementation

An energy audit scheme should make mandatory for all industries and take the necessary steps for a realistic assessment of T&D losses into technical as well as non-technical losses.

The realistic assessment of a utility’s T&D loss is greatly influenced by the sample size chosen, which in turn influences the level of confidence desired and the tolerance limit for variation in results. In light of this, it is critical to set a sample size limit for realistic quick estimates of losses.

Power theft checking Drives

  • Electric power theft is one of the major problems faced by all electric utilities. Take a serious step regarding power theft
  • Implement proper seal management at the terminal of the meter, at CT/PT terminal.
  • Implement MVD (medium voltage distribution) in theft-prone areas
  • Replace advanced digital meters instead of old/sluggish ones
  • Test meter at regular intervals and replace if any issues are noticed.
  • Meter boxes are used and properly sealed to ensure that the meters are properly sealed and cannot be tampered with.

Errors in Meter Reading

The advanced meter should be installed to calculate the use of electrical energy and take the necessary steps to replace the faulty meters.

Billing Problems

  • Non-technical losses should be primarily attributed to erroneous and untimely bill serving.
  • The most common billing complaints are not receiving a bill, receiving a bill late, receiving the wrong bill, incorrect meter reading, incorrect tariff, and incorrect calculations.

What is eddy’s current loss?

According to Faraday’s law of electromagnetic induction, an emf is induced in a material when an alternating magnetic field is applied to a material with the magnetic property.

The EMF’s current flow rotates all around the magnetic material’s body due to the magnetic property of the conducting material. This rotating current is known as Eddy Current. They will happen when the conductor is subjected to a changing magnetic field.

Because these currents aren’t doing any useful work, they cause a loss (I2R loss) in the magnetic material known as an Eddy Current Loss.

Eddy current loss occurs because of the relative motion between the core and the magnetic flux.

What is Hysteresis loss?

The magnetization and demagnetization of the core as current flows forward and backward causes hysteresis loss. The magnetic flux increases as the magnetizing force (current) increases. When the magnetizing force (current) is reduced, the magnetic flux decreases more gradually rather than at the same rate. As a result, even when the magnetizing force is zero, the flux density remains positive. To achieve zero flux density, the magnetizing force must be applied in the negative direction.