RCUC

1
RCUC The Dispatch Process

• Donal Connolly (Eirgrid)
• Michael Preston (SONI)

2
Introduction

• Scheduling versus Dispatch
• Immediate Priorities
• Medium Term Priorities and Inputs into the
  decision to Reschedule or Redispatch
• Why Dispatch and Schedule may differ
• Load Rise and Night Valley

3
Scheduling and Dispatch

• The output of the scheduling process is
• A Unit Commitment schedule
• A set of discrete MW set points for each unit at
  30 minute intervals
• A reserve schedule for each jurisdiction
• A tie-line flow schedule
• The dispatch process
• Adheres to Operational Priorities (safety,
  security, economy)
• Aims to match demand with generation on a second
  by second basis
• Maintains tie-line flow schedules
• Maintains adequate levels of operating reserve at
  all times
• Plans for credible generation and transmission
  contingencies
• Manages real time system disturbances that cause
  frequency deviations, transmission overloads or
  voltage problems
• The Control room operators use the output of the
  scheduling process to guide them in the dispatch
  process

4
Operating the System

• When assessing whether the current schedule is
  adequate to feed into the dispatch process the
  Operator will give consideration to
• Immediate Priorities
• Frequency, Voltage and Flows on Line within
  limits
• Reserve check
• Tie Line Flow (actual to RCUC schedule)
• Medium Term Priorities
• Load comparison (actual to latest forecast to
  RCUC schedule)
• Wind comparison (actual to latest forecast to
  RCUC schedule)
• Generator Availability Changes
• Tie Line Flow
• Margin Check
• If the schedule is not adequate the Operator will
  prepare a new schedule

5
Load Comparison
April
Summer
Winter
Summer B/H
6
Wind Comparison
7
Tie Line Schedule
8
Margin Check

• MW
• MWs Available 4673
• Short Available 4464
• To/From SONI 311
• Wind 114
• 4889
• Est. Peak 4000
• Margin 889
• Reserve
• POR 308 MW (75 of largest in feed, 5 15 sec)
• SOR 308 MW (75 of largest in feed, 15 90 sec)
• TOR1 410 MW (100 of largest in feed, 90 sec 5
  min)
• TOR2 410 MW (100 of largest in feed, 5 min 20
  min)

9
Reschedule or Dispatch
10
RCUC to EDIL
11
Unit Trip
49.94 Hz
78 MW
TH4 Sync
-207 MW
49.29 Hz
12
Dispatch Instructions (Unit Trip)
13
Frequency Response
14
Load Comparison
Previous Day
Previous Week
Current Day
Cold Front
Match
15
Wind Forecast

• Divergent Forecasts
• Forecast Different from Wind
• Forecast Timing

16
Met Information
17
Wind Rising
18
Contingency Analysis
19
Load Rise 07 Apr 08

• RCUC looks at 30 minute intervals but demand is
  changing on a second by second basis and the
  dispatcher must consider how the demand changes
  when issuing instructions

0600 0900 1348 MW Wind Output and Loss of
largest in-feed
20
Dispatch Instructions 07 Apr 08

• As can be seen here, to manage a typical morning
  load rise the operator had to issue 55 separate
  MW instructions over a 2 and ½ hour period.

21
Night Valley 06 May 07

• This table shows the problems faced by the
  operator when all plant is dispatched to Minimum
  Load.
• The operator may have to de-commit plant in an
  unscheduled way due to unexpected increases in
  wind output, decreases in system demand,
  generator limitations or a combination of all of
  these.

22
Summary

• The Scheduling Process feeds into the Dispatch
  Process
• Operators take a number of real-time factors into
  account when issuing dispatch instructions
• Time permitting, Operators will re-schedule if
  the current schedule cannot be followed
• Operators will face unplanned issues when
  dispatching
• At all times operators give priority to safety
  and security