1. ECE 476 POWER SYSTEM ANALYSIS
Lecture 5
Power System Operation, Transmission Lines
M.E.E. Muhammad Al-Badri
Department of Electrical and Computer Engineering

2. Reading and Homework 1st Exam moved to Oct 11 (in class)
For lectures 4 through 6 please be reading Chapter 4
we will not be covering sections 4.7, 4.11, and 4.12 in detail though you should still at least skim those sections.
HW 1 is 2.9, 22, 28, 32, 48; due Thursday 9/8
For Problem 2.32 you need to use the PowerWorld Software. You can download the software and cases at the below link; get version 15.
Direct PowerWorld download page is

3. Substation Bus

4. Power Transactions
Power transactions are contracts between areas to do power transactions.
Contracts can be for any amount of time at any price for any amount of power.
Scheduled power transactions are implemented by modifying the area ACE: ACE = Pactual,tie-flow - Psched

5. 100 MW Transaction Scheduled 100 MW Transaction from Left to Right
Net tie-line
flow is now
100 MW

6. Security Constrained ED
Transmission constraints often limit system economics.
Such limits required a constrained dispatch in order to maintain system security.
In three bus case the generation at bus 3 must be constrained to avoid overloading the line from bus 2 to bus 3.

7. Security Constrained Dispatch
Dispatch is no longer optimal due to need to keep line
from bus 2 to bus 3 from overloading

8. Multi-Area Operation
If Areas have direct interconnections, then they may directly transact up to the capacity of their tie-lines.
Actual power flows through the entire network according to the impedance of the transmission lines.
Flow through other areas is known as “parallel path” or “loop flows.”