Good Voltage Regulation and Justified Power Factor Correction

Power factor correction and voltage regulation are closely related. In many cases, the desired voltage regulation is costly to obtain. Larger or paralleled conductors to reduce voltage drop under load are, in many cases, the proper solution.
However, power factor correction may also be justified for four reasons:

1. To improve voltage
2. To lower the cost of electric energy, when the electric utility rates vary with the power factor at the metering point
3. To reduce the energy losses in conductors
4. To utilize the full capacity of transformers, switches, overcurrent devices, buses, and conductors for active power only, thereby lowering the capital investment and annual costs

Location of Current Transformers in HV Substation

Power flow

Current transformers are used for protection, instrumentation, metering and control. It is only the first function that has any bearing on the location of the current transformer.

Ideally the current transformers should be on the power source side of the circuit breaker that is tripped by the protection so that the circuit breaker is included in the protective zone.

An example of calculating the technical losses of T&D lines

Introduction to Losses

There are two types of losses in transmission and distribution line.

1. Technical Losses and
2. Commercial Losses.

It’s necessary to calculate technical and commercial losses. Normally technical losses and commercial losses are calculated separately.

Transmission (technical) losses are directly effected on electrical tariff, but commercial losses are not implemented to all consumers.

Technical losses of the distribution line mostly depend upon electrical load, type and size of conductor, length of line etc.
Let’s try to calculate technical losses of one of following 11 KV distribution line

Vector Group of Transformer

Introduction:

Three phase transformer consists of three sets of primary windings, one for each phase, and three sets of secondary windings wound on the same iron core. Separate single-phase transformers can be used and externally interconnected to yield the same results as a 3-phase unit.
The primary windings are connected in one of several ways. The two most common configurations are the delta, in which the polarity end of one winding is connected to the non-polarity end of the next, and the star, in which all three non-polarities (or polarity) ends are connected together. The secondary windings are connected similarly. This means that a 3-phase transformer can have its primary and secondary windings connected the same (delta-delta or star-star), or differently (delta-star or star-delta).
It’s important to remember that the secondary voltage waveforms are in phase with the primary waveforms when the primary and secondary windings are connected the same way. This condition is called “no phase shift.” But when the primary and secondary windings are connected differently, the secondary voltage waveforms will differ from the corresponding primary voltage waveforms by 30 electrical degrees. This is called a 30 degree phase shift. When two transformers are connected in parallel, their phase shifts must be identical; if not, a short circuit will occur when the transformers are energized.”

 Basic Idea of Winding:

Calculate Voltage Regulation of Distribution Line

Introduction:

• Voltage regulation or Load Reguation is to maintain a fixed voltage under different load.Voltage regulation is limiting factor to decide the size of either conductor or type of insulation.
  
• In circuit current need to be lower than this in order to keep the voltage drop within permissible values. The high voltage circuit should be carried as far as possible so that the secondary circuit have small voltage drop.

Voltage Regulation for 11KV, 22KV, 33KV Overhead Line (As per REC):

• % Voltage Regulation= (1.06xPxLxPF) / (LDFxRCxDF)

Total Losses in Power Distribution and Transmission Lines-Part 2

(2) Non-Technical (Commercial Losses):

• Non-technical losses are at 16.6%, and related to meter reading, defective meter and error in meter reading, billing of customer energy consumption, lack of administration, financial constraints, and estimating unmetered supply of energy as well as energy thefts.

 Main Reasons for Non-Technical Losses:

(1)  Power Theft :

• Theft of power is energy delivered to customers that is not measured by the energy meter for the customer. Customer tempers the meter by mechanical jerks, placement of powerful magnets or disturbing the disc rotation with foreign matters, stopping the meters by remote control.

(2)  Metering Inaccuracies:

• Losses due to metering inaccuracies are defined as the difference between the amount of energy actually delivered through the meters and the amount registered by the meters.
• All energy meters have some level of error which requires that standards be established. Measurement Canada, formerly Industry Canada, is responsible for regulating energy meter accuracy.
• Statutory requirements5 are for meters to be within an accuracy range of +2.5% and – 3.5%. Old technology meters normally started life with negligible errors, but as their mechanisms aged they slowed down resulting
• in under-recording. Modern electronic meters do not under-record with age in this way.
• Consequently, with the introduction of electronic meters, there should have been a progressive reduction in meter errors. Increasing the rate of replacement of mechanical meters should accelerate this process

(3)  Un metered Losses for very small Load:

Total Losses in Power Distribution & Transmission Lines-Part 1

Introduction:

• Power generated in power stations pass through large & complex networks like transformers, overhead lines, cables & other equipments and reaches at the end users. It is fact that the Unit of electric energy generated by Power Station does not match with the units distributed to the consumers. Some percentage of the units is lost in the Distribution network. This difference in the generated & distributed units is known as Transmission and Distribution loss.
• Transmission and Distribution loss are the amounts that are not paid for by users.
• T&D Losses= (Energy Input to feeder(Kwh)-Billed Energy to Consumer(Kwh)) / Energy Input kwh x100
• Distribution Sector considered as the weakest link in the entire power sector. Transmission Losses is approximate 17% while Distribution Losses is approximate 50%.
• There are two types of Transmission and Distribution Losses

1. Technical Losses
2. Non Technical Losses (Commercial Losses)