The Electrical Control and Energy Management System of a University

The Electrical Control
and Energy
Management System of
a University
University of Texas a Case Study
Introduction

University of Texas at Austin (UT)
– Founded in 1883 has the 5th largest enrollment in the
country
– Over 50,000 undergraduate and graduate students
– More the 16,500 faculty and staff
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 2
Why UT Wanted the ECS

Main Campus Power Plant and Chilling Stations
– 112 MW installed capacity
– 40, 000 Tons capacity

In 2005 the campus had 2 blackouts causing
disturbances to power system
– The existing system was not capable of load shedding
during the power outage and they needed tighter
demand control

UT officials wanted to get the generation plant
ready to sell power
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 3
University of Texas Steam and Power
OIL
MSCFH
GAS
MSCFH
MSCFH
45 MW
35 MW
MSCFH
MSCFH
MSCFH
MSCFH
MSCFH
CTG 8
CTG 10
AUTO
DROOP
HRSG 8
MSCFH
AUTO
DROOP
UB1
UB2
UB7
UB3
HRSG 10
75 KLB/H
PRESS
75 KLB/H
150 KLB/H
500 KLB/H
TEMP 420# STEAM
500 KLB/H
300 KLB/H
25 MW
STG 9
270 KLB/H
PRESS
165# STEAM
180 KLB/H
180 KLB/H
25 MW
6.25 MW
STG 7
STG 4
AUTO
DROOP
MAN
DROOP
150 KLB/H
450 KLB/H
6.25 MW
STG 5
150 KLB/H
TEMP
POWER
TIE
120 MVA
ELECTRIC CHILLERS
System Conditions

The campus can generate power and buy power
– Currently power demand is satisfied with internal
generation
– May change if price of gas increases
– May be financially wise to sell power in the future

If load exceeds available generation – must shed

Varying reactive power demand

Penalty if imported MW exceeds agreed value

Penalty for low power factor on imported power
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 6
Components of the new ECS

Tie-line power monitoring

Demand Control

High speed contingency analysis and load
shedding

Reactive power control
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 7
System Configuration
SCADA System
OPC LINK
MMI
ENG
REDUNDANT PC
Load Shed Logic
HSR
Data
Highway
CONTROLLER
Remote I/O to Load Shed Breakers
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 8
High Speed
Load Shed Controller
50 msec
CONTROLLER
Demand Control
Reactive Power
Control
Tie-Line Monitoring
Tie-Line Power Monitoring
Sliding Window Control
Predict Average MW Consumption at End of Demand Period
DEMAND MW
ERROR
DEMAND LIMIT
MW (15-t)
15
)
MW
t
A
4*
0
0
15
t
TIME MINUTES
A
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 9
MWH
Load Control

Performs Demand Control
– Keeps tie power equal to setpoint
– If cheaper to generate – value should be close to zero
– If cheaper to buy – value should be close to the
demand limit
– To sell power value should be negative

Adjust MW amount on generators
– RAISE/LOWER Pulse or MW Value (4-20ma)
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 11
Contingency Analysis Load Shedding

Multiple Power Producers

Low Bus Frequency

Some combination is required to satisfy plant
load

If plant demand exceeds available capacity must
shed to prevent overload of remaining power
sources
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 14
Contingency Analysis / Load
Shedding

Load Shed Features
– High Speed (<100ms )
– Capable of monitoring hundreds of discrete loads
– Control loads dispersed over large area
– Capable of changing load priority
– Capable of inhibiting loads from being shed
– Capable of analyzing system configuration to determine
load connections
– Capable of switching machines to Isochronous mode
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 15
Load Shed Program Components

Redundant “What If” Program
– Determines amount of power and loads to
shed if a contingency case occurs
– Runs in a redundant PC

In Ovation Controller every 50msec check
is made to see if a contingency occurred
– If yes – shed load determined by the “What If”
program
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 16
69KV
Electrical Overview
University of Texas at Austin
GRID
HA-855
HA-857
WWW
WWW
WWW
HE-1
WWW
HNM
HWM
HARRIS SOUTH
HEST
HA-853
WWW
HSM
HARRIS EAST
HA-852
WWW
HEWT
HA-851
WWW
HEM
12KV
HA-850
WWW
HA-856
HSET
HS-5
HARRIS NORTH
HSNT
HNST
HN-5
HARRIS WEST
HNWT
HWNT
HW1
HWET
{
{
{
{
{
{
{
{
ANNEX WEST
ANNEX EAST
12KV
C8
AWM
12KV
AW-10
AWET
AEWT
AEM
WW-4
X
WEAVER EAST
WEAVER WEST
C6
WWM
AE-1
3.6 MVAR
Cap Bank
S7
WWNT
WWET
WEWT
WEST
WE-4
WEM
{
{
WEAVER NORTH
4.16KV SOUTH
4.16KV NORTH
WEAVER SOUTH
}
{
6 MVAR
X
Cap Bank
WN-1
WWW
WWW
WN-3
5NM
5N-9
S5
5NST
5S-3
5SM
WS-1
WS-2
WWW
S4
S9
WWW
WNWT
WSNT
WSET
Load Shed Cases

13 Possible Contingency Cases:
– Loss of a main generator (6 cases)
– Loss of grid connection
– Under-frequency of generation buses (6 cases)
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 18
Amount to Shed Calculation
 For loss of power producer
– Amount_to_shed
= [Lost_MW_amount –
(Total_spare_capacity * Correction_factor)] *
OverShed_factor

For Low Bus Freq
– SHED_AMT = ((Base_Freq/Act_Freq)^2 –
1)*Bus_MW_Dmd
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 19
Why Reactive Power Control is
Important
 Stable system operation requires bus
voltages stay within assigned limits
 Ensure transformer and connecting cables
do not become overloaded
 Generators run within their reactive
capability
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 23
Capacitor Bank Advisory

Recommends if capacitor banks should be ON or
OFF
– Annex East – 3.6 MVAr
– Weaver North – 3.0 MVAr
– Power Station North – 1,2 or 3 MVAr

Improve power factor of plant

Reduce VArs generators must make

Reduce import of VAr from grid
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 24
Generator VAr Control

Ensure the voltage on the 12kV and 5kV buses is
maintained

Keep generators within their reactive capabilities

Reduce import of VArs from grid

Raise/Lower pulses to generator AVR adjusts the
VArs

All generators are controlled
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 25
Conclusion

The ECS allows the operator to enter the amount of
power he would like to buy or sell
– Provides a cost saving

Load shed system constantly running and will shed in
<100 msec after a disturbance
– Operator can change priority on loads at anytime
– Will Keep system stable after a disturbance

Reactive power control maximizes the use of capacitor
banks giving more MW capacity to generators and
minimizes the import of VArs

System was installed in April 2008
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 29