system load calculation for aep-texas

Kirk Schneider

American Electric Power

Tulsa, Oklahoma

AEIC Annual Load Research Conference Reno, Nevada

September 10-13, 2006

System Load System Load Calculation for AEP-Calculation for AEP-

TexasTexas

• What We Did

• Why We Did It

• How We Did It

• What We Found

• So What?

Introduction

The American Electric Power System

•ERCOT became single Control Area 7/31/01

•Companies stopped checking tie lines.

•Installed IDRs on a Number of Tie-Lines

•Verified IDR Data for generation and tie-lines

•Rate filing for TCC and TNC later this year.

•Update loss studies.

•Update demand studies

What We Did

What is System Load?

• Total power consumption on system

• Measure Power Received from Generators

• Measure Power Flow at Interconnect Points

• Can directly measure load, but not losses

“Top-Down” System Load Calculation

I

II

G

G30

0 M

W

20

0 M

W

10 MW

20 M

W

40 MW

Generation: 300 + 200

Interchange: -10-20

+40 --------

Net Load: 510 MW

“Bottom-Up” Load Calculation

I

II

G

G

Load: RES 190 COM + 100 IND + 60 WHL + 140

Losses: + 30 ------------------Load: 520 MW

UFE: - 10 MW

Power Consumption in North American Grid

• No Boundary Metering

• Power is consumed the instant it is generated

• Power Consumed = Power Generated

• Power Consumed = Power used + power “lost”

ERCOT Transmission System

ERCOT System Load

• Connected to grid with 3 DC ties

• System Load = generation + power

imported over DC ties – power exported

over DC ties

• SYSTEM LOAD = GENERATION – NET

INTERCHANGE

• EPS Meters on Generation and DC Ties

AEP-Texas System Load

• Texas Central Co. (South Texas)

• Texas North Co. (West Texas)

• TCC ~ 30 Gens, 50 Interconnects

• TNC ~ 20 Gens, 40 Interconnects

Texas Central Transmission System

Texas North Transmission System

•Demand Studies

• Σ Sales * Loss Factor = Estimated System Load

•Loss Studies

• Losses = System Load – Σ Sales

• Transmission Settlements

• Unbilled Sales

• Checks and Balances

• All Assume System Load is Correct

Why AEP Needs System Load

•About 12 complete – meter and CT / PTs

•About 24 meter only using existing CT / PTs

•Accuracy of Meters

•Leveraging Existing Metering In South Texas

How did We Implement AEP-Texas Tie-Line Metering?

TCC Ties to South Texas EC

How Are We Collecting and Analyzing the Data?

•Collecting Data Using MV-90 System

•Data Validation

•Analyzing Data Using SAS

•Sent to CEAS System

PROBLEMS!

• Gaps in IDR Data

• Suspicious Looking Data

• Missing Meters

• Problems Getting Data from ERCOT

SCADA to the Rescue!

• PI Database Installed Oct 2004

• Analog Measurements

• Accessible with ODBC or OLE

• SAS Table Containing SCADA Data

Data Validation

•Use SCADA Data to Validate IDR Data

•SCADA Strengths Complement IDR Data

•Use SCADA Data to Fill IDR Data Gaps

•Examples

Everything’s All Right – Generator 1

Everything’s All Right – Generator 2

Everything’s All Right – Tie 1

Everything’s All Right – Tie 2

Good Enough – SCADA at opposite end of line

Better than Nothing – SCADA at opposite end, load along

line

Load Outside Boundary of Meters

Gap In IDR Data - Generator

Gap in IDR Data - Line

SCADA Goes “Flat-Line” for Short Period – Gen

SCADA Goes “Flat-Line” for Short Period – Line 1

SCADA Goes “Flat-Line” forShort Period – Line 2

SCADA Goes “Flat-Line” for Short Period – Line 3

SCADA Goes “Flat-Line” for Long Period – Line 1

SCADA Goes “Flat-Line” for Long Period – Line 2

SCADA Goes “Flat-Line” – Long Period - Gen

SCADA Resolution Problem – Small Line

SCADA Resolution Problem – Line

Time-Synch or Resolution??

No SCADA Available – Wholesale POD’s

General SCADA Failure – Example 1 Gen

General SCADA Failure – Example 2 Gen

General SCADA Failure – Example 3 Line

General SCADA Failure – Example 4

General SCADA Failure – Example 5 Line

Suspicious Generator Data

Impact on System Load Calc

Meter Configuration

Using Alternate SCADA Points

IDR Data vs. SCADA

• IDR Strengths

•True integrated values

•Distributed data collection

•Lower cost than SCADA

• SCADA Strengths

•Time synch extremely accurate

•Data available real-time

•Multiple backup measurements

• Together Provide Very Reliable, Accurate Data

Top Down vs. Bottom UpSummer

Top Down vs. Bottom Up Winter

Top Down System vs. Bottom Up At Meter

System Losses

Percent Losses

Summary of Results

• SCADA Bailed Us Out

• Strengths of IDR Data and SCADA Complementary

• Customer Load Aggregation Matches System Load

• Able to Perform Loss Study

So What?

• We Can Measure AEP-Texas System Load

• Two Measurements Better Than One

• Understand Your System Load Data

• Accurate System Load = $$$

• Let’s Work Together Again!