PRESENTED BY:
RAYMOND KATAMBA

---

[attachment=14993]
Optimization of Distribution Systems To Transmit Power Under Single Phase Faults
INTRODUCTION
As Electricity industry continuously grows availability, quality, capacity and safety of electricity increasingly become a concern
Conservative expansion of existing structures not possible due to economic, social and technical factors new techniques to increase capability and reliability of lines devised.
Single phase faults are most frequent, and presently resulting to total outages, damage to machines (NSS) and living things (ZSS)
Power electronics devices (symmetrization compensators) enable continued safe and reliable operation of power systems under single phase faults
INTRODUCTION
FAULT STATISTICS
Primary Automatic and Forced Manual Outages by Fault Type, 11kV Voltage level , Europe and Africa, 1987-2009 (Sourced from: International Power Systems Journal, June 2010 release)
PROBLEM STATEMENT
Single phase faults are the most frequently occurring in power distribution systems. The resulting asymmetrical conditions are of concern to rotating synchronous machines and safety of personnel. Presently, the whole line section is disconnected from the grid in case of a fault. However, utilization of the sound phases is an economically and ecologically viable alternative.
JUSTIFICATION
Compensated systems are suitable for emergency and high-profit commercial consumers (hospitals, industries, military and government)
Case study involved Mulago hospital and UBL
UBL consumed total power of 1085.4MWH (approx. Ugx 210m) in Feb 2011.
Total power outages were 17of which power line faults were 13, and average rectification time was 50minutes.
Optimized systems will enable instant switching to emergency consumers while keeping low-end consumers off.
LOAD FLOW DIAGRAM AT THE 8 BUS DISTRIBUTION N/W
SIMULATION RESULTS FOR 8 BUS NETWORK
SIMULATING SINGLE PHASE FAULT ON SYSTEM
SVC OPERATION PRINCIPLE
A Static VAR Compensator (or SVC) fast-acting reactive power on high and medium voltage.
The SVC is an automated impedance matching device, designed to bring the system closer to unity power factor.
If the power system's reactive load is capacitive (leading), the SVC will use reactors (usually in the form of Thyristor-Controlled Reactors to consume
Under inductive(lagging) conditions, the capacitor banks are automatically switched in, thus providing a higher system voltage
By means of phase angle modulation switched by the thyristors, the reactor may be variably switched into the circuit and so provide a continuously variable MVAr injection (or absorption) from network
In doing this the thyristors vary the firing angle between 0 < α < 90.
voltage control is provided by the capacitors; the thyristor-controlled reactor is to provide smooth control
COMPENSATOR CIRCUIT COMPONENT DIAGRAM
SVC OPERATION MODES
THE BY PASS MODE (α = 0 ) : The thyristor valve is triggered continuously the basic circuit behaves like a parallel connection of a series capacitor and inductor.
INDUCTIVE BOOST MODE (0 < α < αres) for alpha below the resonance angle the equivalent circuit reactance Xeq is positive corresponding to an inductance
CAPACITIVE BOOST MODE. ( αres < α < 90) for alpha a greater than the resonance angle the equivalent reactance is negative resulting in capacitive behavior.
BLOCKING MODE ( α = 90 ) the thyristor is not triggered and therefore kept in non conducting state . simply the fixed capacitor contributes to the reactance
BASIC CONSTRUCTION OF A UPFC
Consists of two switching GTO converters
Shunt-connected
Series-connected
Both converters can operate in a rectifier mode or in an inverter mode
A DC branch links these two converters by a storage capacitor.
OPERATION PRINCIPLE
Conceptually, a generalized SVS
Converter2 injects a voltage Vpq with phase angle in series with TX line via an insertion transformer
Main function of converter1 is to supply the real power demanded by converter2 at the DC link
No reactive power flow through DC link
UPFC has three operating modes:
uncontrolled mode
inductive mode
capacitive mode
COMPENSATED NETWORK PROTOTYPE
SIMULATION RESULTS
GRAPH SHOWING SYSTEM BUS VOLTAGE PROFILES
CONCLUSION
Power reliability for high-end consumers is enhanced by this technique.
With the additional equipment installed at substations, a line can operate safely during fault conditions
The other advantages are that it is faster to implement and requires less approval procedures.