Challenges And Issues Related To Interconnection

 Challenges And Issues Related To Interconnection

Challenges and Issues related to Interconnection

Challenges and issues are classified into two parts as technical and non-technical which are given below

1.Technical Issues

1. Power Quality: It involves mainly three things : Harmonics, Frequency fluctuations and Voltage fluctuations.
2. Power Fluctuations : It concerns with Small time power fluctuations and Long time or seasonal power fluctuations
3. Power storage,
4. Optimal locations,
5. Islanding,
6. System protection,
7. Thermal limits,
8. Stability limit,
9. Synchronisation,
10. Available transmission capacity (ATC)
11. Surge voltage

2. Non-Technical Issues

1. Non-availability of skilled workers
2. Availability of land at lower cost
3. Availability of transmission line

Thermal Limits

Power transfer capacity of transmission lines, transformers and other equipment is depend upon temperature limit. If it exceeds then the equipment can get damaged or became inoperative.

Transmission lines carries more current if heat is dissipated properly. When transmission get heated, metal expands and line sags.

It sag becomes larger, it can make or get contact with neighbouring object resulting into fault.

Thermal limits are not functions of transmission line length. Thermal limit determines the maximum power transfer for lines less than 50 miles in length.

Stability Limits

Stability limit of a transmission line is the largest amount of power that can be transferred without losing synchronism if any disturbance occurred.

Power flow can be given as

P =VR× Vs  Sinδ ÷ x

Where VR - Receiving end voltage

             Vs- is the sending end voltage 

             X-  transfer reaction

             δ - Angle between  VR and  Vs

Power transmission increased if δ approaches toward 90° and decreases if δ approaches towards 0°.  

Stability limit indicates the power angle value that allows maximum power transfer by maintaining in stability or synchronism.

Frequency Variations

Allowed value of frequency variation is  ±3% i.e. if system is operating at frequency of

50 Hz, then allowed value of frequency deviation be 48.5 Hz to 51.5 Hz.

If frequency variations are larger it lower down the power factor of the system.

If transformer operates at lower value of frequencies leads increase in flux in the

transformer.

It pushes transformer to operate at near to the saturation causing larger losses and increase in VAR consumption.

Frequency larger than specified limit can damage the electrical equipment. Sometimes it leads to the collapse of the power system.

Voltage Regulations

Voltage regulation indicates the allowable value of the voltage fluctuations. These variations are decreasing the life of equipments.

Surge Voltage

It is the value of voltage that cause damage to the electrical equipment like Vacuum tubes, relays and semiconductor devices, etc.

Power Quality

Power quality is term represents the deviation of sinusoidal waveforms of supply voltage or load current.

This deviation is due to the impulsive and oscillatory transients, voltage dips, short interruption, harmonics and flickers.

Grid Fault

Gird faults are lowered down in numbers by placing impedance or reactors or reactance or resistance in the transformer neutral or by reducing transformer size.

Available Transmission Capacity (ATC)

It is the maximum value of the transfer power through the transmission line without loos

of synchronism.

Synchronization

Synchronism is the matching of voltage magnitude, phase angle and frequency between the grids which are connected to each other.

Un-Required Islanding

It occurs when distributed generators are supplying power to the electrical network even after circuit breakers disconnects the part from the gird.

It creates various problems like safely issues of operating persons, damages to the

equipments, maintenance of faulty parts.

Economic Issues

Here cost benefits are considered from avoided fuel, capacity improvement and smooth operation of electrical networks lower cost of both fuel and capital expenditure, earnings from interconnections, better load levelling, install capacity and spinning reserve requirement gets lower, economic optimization of power exchanges.

Environmental Issues

It provides environmental benefit performance by avoiding greenhouse gas emission, lesser regional, local and indoor air pollution etc.

In case of HVDC interconnections, there is no need for common frequency control and

stable operation at low power interconnection.