Transmission Expansion Planning in Deregulated Power ... - tuprints

4 Market Based Criteria 32

4.2 Market Based Criteria

Fig. 4.1 – L**in**e No. i of a network

In this section two probabilistic criteria, average congestion cost and standard deviation of

mean of LMP, are proposed to measure how much a specific plan facilitates competition

among customers. Average congestion cost shows how **in**tensive transmission constra**in**ts are

and consequently shows how competitive electric market is. Standard deviation of mean of

LMP shows how mean of LMP spreads throughout the network. Therefore, it shows how

discrim**in**ative and consequently how competitive electric market is.

4.2.1 **Transmission** Congestion

A l**in**e is congested if its power has reached to its limit. Transmitt**in**g more power through this

l**in**e is not allowed. In other words, a l**in**e is congested if its associated constra**in**t **in** (3.3) is

active. Under transmission congestion next MW of some loads can not be supplied by the

cheapest undispatched generation. The next MW of these loads, depend**in**g on their places **in**

the network, is supplied by other more expensive generations. Hence, under congestion buses

have different LMPs.

Congestion cost of a l**in**e is def**in**ed as the opportunity cost of transmitt**in**g power through it.

Consider figure 4.1, l**in**e i of a network is depicted **in** this figure. The end buses of this l**in**e

numerated with i1 and i2.

Pl MW electric power transmits from bus i1 to bus i2 through this

i i

1 2

l**in**e. LMPs of buses i1 and i2 are

lmp i and

1

lmp i **in** $/MWhr. Buy**in**g 1 MW electric power

2

from bus i1 costs lmp i $/hr and buy**in**g 1 MW power from bus i2 costs 1

i2

lmp $/hr. Therefore,

the opportunity cost of transmitt**in**g 1 MW electric power from bus i1 to bus i2 is equal to

( i2

i1

lmp − lmp ) $/hr. Thus, congestion cost of l**in**e i or the opportunity cost of transmitt**in**g

Pl MW electric power from bus i1 to bus i2 through l**in**e i is equal to:

i i

1 2

lmp i

lmp

1

i2

i1

Pl i i

1 2

L**in**e No. i

i2