1.3 Dispatch Signal / LMP

Question 1

Dispatch Rate:

• units
• purpose
• what is it based on

Answer 1

$/MWh

• directs output of generators to where PJM wants them to be loaded economically
• based on in incremental offer data previously rec’d from generators.

Question 2

What PJM program calculates the dispatch rate?

Answer 2

Security Constrained Economic Dispatch Program (SCED)

Question 3

What is the Economic Basepoint?

• units?
• what two factors determine it?

Answer 3

• MW
• value sent to unit indicating how much to generate
• based on SCED solution and unit’s incremental price curve

Question 4

What happens if SCED is not available?

Answer 4

Manual dispatch is used.

Question 5

What is the Loss Penalty Factor or Penalty Factor?

Answer 5

This adjusts the incremental cost of each generator to include the effects of losses.

Question 6

What does it tell you if the penalty factor is less than 1?

Answer 6

An increase in generation would result in a decrease in system losses.

• unit offer curve multiplied by penalty factor
• unit looks more attractive to dispatch.

Question 7

What is Security Constrained Re-Dispatch?

Answer 7

When constraints occur preventing use of least-cost generator. Higher cost generator closer to load must be used.

Question 8

What is used to determine which units should be re-dispatched in constrained situations?

Answer 8

$/MW effect on a transmission line:

$/MW effect = (System marginal price - Marginal Cost of Unit) / Unit shift factor

• Units with lowest $/ MW effect are used to redispatch during constraints.

Question 9

Locational Marginal Price - what is it based on ? what is it used for?

Answer 9

• Physical, flow-based pricing system. (not based on contract paths)
• Generators get paid at gen bus LMP, Loads pay at load bus LMP

Question 10

LMP equation

Answer 10

LMP = SMP + Congestion component + Marginal Loss component

Question 11

System Marginal Price (SMP)

Answer 11

Same price for every PJM bus (no location aspect).

LMP w/o losses or congestion.

Question 12

Congestion component - positive vs negative

Answer 12

When bus is upstream of a constraint, CC is NEGATIVE (results in - revenues to unit)

• When bus is downstream of congestion, CC is POSITIVE (results in + revenues to unit)

Question 13

Marginal Loss Component

Answer 13

• Represents $ of marginal transmission losses, based on penalty factors (% increase in losses for increase in injection or withdrawal).

Question 14

Marginal Loss component - +/-

Answer 14

When bus is DISTANT from load, MLC is NEGATIVE

• When bus is CLOSE to load, MLC is POSITIVE