Transcript Slide 1

Integrated Testing and Field Certification of
Revenue Metering Sites For PQsynergy 2011
Ming T. Cheng
Director of Asian Operations
10737 Lexington Drive
Knoxville, TN USA 37932
Phone:1.865. 218.5837
[email protected]
www.powermetrix.com
Taking from Bill Howe’s presentation yesterday
Smart Grid can……..
• Precise measurement and verification
Otherwise, it will be garbage in and Garbage
out…….
Poor PQ -> Metering Error -> Lost revenue….
Why do we test a site?
• Verify accuracy to protect OUR revenue
stream.
• Verify accuracy to ensure we fairly bill the
customer.
• Assure site is wired safely and to codes.
Integrated Site Test Philosophy
Site Analysis
Meter Testing
CT Testing
Site Testing is an Investment.
One with a very good return!
What are the costs? (The Investment)
Testing Equipment
Vehicles (Vans, Trucks)
Fuel
Metermens’ Pay
Time
Site Testing is an Investment!
What is the Return for the Investment?
Increased Revenue!
$ $ $
3 Year Study from a US Municipal with
35,000 Transformer Rated Installations
Total Problems Found after 10% of Sites Tested:
96
Percentage of Sites found to have a Problem:
96 ÷ 3,500 ≈ 2.7%
Annualized Revenue Recovery:
$ 2,248,354
Annualized Revenue Recovery per Problem:
≈ $ 23,420
Annualized Revenue Recovery per Test:
≈ $ 642
Wiring Error
8%
6%
12%
Wiring
Error
CT Problem
Problems
Encountered
12%
14%
12%
8%
8%
6%
6%
14%
8%
12% 12%
14% 22%
14%
14% 22%
12%
8%
6%
8%
22%
14%
22%
22%
12%
8%
6%
6%
38%
6%
CT
Problem
Administrative
Wiring
Error
Error
Administrative
Administrative
Error
Faulty
Meter
CT
Problem
Wiring Wiring
Error
Error
38%
Error
Faulty
Meter
PT
Problem
PT
Problem
Administrative
CT
Problem
38%CT Problem
Error
PT
Problem
Theft
ofMeter
Service
Faulty
Faulty
Meter
Administrative
Wiring
Error
Administrative
38%Error
Error
Theft
of Service
PT
Problem
Faulty Meter
CT
CT
Faulty Problem
Meter
38%
Theft
ofError
Service
PT Problem
Administrative
Wiring
Error
Wiring
PT
Problem
Error
CT
Problem
Theft ofFaulty
Service
Theft
ofMeter
Service
Theft
of Service
38%
Administrative
PT
Problem
14%
Error
Any
guesses???
Most problems
result
in
revenue
loss.
22%
Faulty Meter
38%
Theft of Service
PT Problem
What are we testing for:
• Wiring problems
• Transformer Issues


CT
PT
• Meter problems
Consider a Typical Metering Installation
Wiring problems show up in many ways.
Often as PT or CT issues.
Bad Wiring on Voltage Circuit
• Can reduce available current to meter so it doesn’t
have VA to operate properly
• Current drawn by meter reduces voltage seen at
meter
R1
I
Vm
UTILITY
CONNEC
TION
Vu
Rm
R2
V m  Vu  I * ( R1  R 2)
METER
Bad Wiring on Voltage Circuit
• For 50 ft of #14 wire to the meter,
normally we would have:

Vu = 120V, I = 0.2A, R1+R2 = 0.036Ω => 0.0075V
=>0.006% Error
• Consider a bad connection with resistance
4.0 Ω, then

Vu = 120V, I = 0.2A, R1+R2 = 4.036Ω => 0.843V
=>0.7% Error
• A significant error
V m  Vu  I * ( R1  R 2)
Bad Wiring on Voltage Circuit
Wiring errors can
drastically
reduce metered
power.
A simple phase
reversal reduces
measured power
by 33%.
Faulty Wiring on the Current Circuit
• A faulty connection can easily add a few
tenths of an Ohm burden
• Improper wiring
• Missing commons
• Multiple Grounds
• Almost all wiring errors result in reduced
billing.
Wiring on the Current Circuit
• Even a little extra resistance in a CT circuit can
cause large errors
• Using too small a gauge wire can result in over
burden


50 ft of #14 wire is 0.14Ω this is more burden than is allowable
for a 0.1B class CT.
50 ft of #12 wire is 0.09Ω this is almost the total burden
allowable for a 0.1B class CT.
• Without any bad connections or other problems
using too small a wire size can insure you get the
worst performance from your CTs.
Errors with Instrument Transformers
• Many CTs are only
rated at B0.1 and B0.2
•
•
•
•
•
#16 wire is 4.5 mΩ/ft
#14 wire is 2.8 mΩ/ft
#12 wire is 1.8 mΩ/ft
#10 wire is 1.1 mΩ/ft
#8 wire is 0.7 mΩ/ft
• 50ft of #12 wire is 0.09 Ω. That
is 90% of the allowed burden
for a B0.1 CT.
CT – Accuracy – Burden - Load
0.3B1.8 CT
0.6
Percentage Accuracy
0.5
1.8
0.4
0.3
Ohm
s
0.9 Ohm
s
0.2
0.2 Ohms
0.1
0.05 Ohms
1
2
5
10
100
Percent Rated Load
400
Saturation
Meter Performance under Real
World Conditions
• The fact that a meter is accurate in the
lab does not mean it is accurate in the
field
 Harmonics
 Rapidly changing loads
 Power factor variations
• Can all affect accuracy
Meter Performance under Real
World Conditions
• Large “errors” can occur in the calculation
of VA and VARS when PF≠1



There is no “official” definition in the presence
harmonics.
Different meters may implement different
definitions
Variations can be as large as 15-30 percent
between two meters each of which is “working
properly”
Field Testing Philosophy
Site Analysis
Meter Testing
Step 1
Step 2
CT Testing
Step 3
Integrated Site Test Philosophy
CT Burden Testing
Site Analysis
Meter Testing
PHASE
0.0 Ω
0.1 Ω
0.25 Ω
0.5 Ω
1.0 Ω
2.0 Ω
4.0 Ω
A
2.358
2.360
2.353
2.361
2.349
2.358
NA
B
2.227
2.181
2.167
2.179
2.156
2.172
NA
C
2.556
2.545
2.562
2.533
2.556
2.530
NA
Secondary Amps
CT
Testing
CT
Testing
Integrated Site Test Philosophy
CT ERROR PLOT
Site Analysis
Meter Testing
Amplitude AND
Phase Angle Error
CT
Testing
CT
Testing
Instrument Transformers Control Metered Values
… What If They Do Not Produce The Expected Outputs
Traditionally Only The Meter Is Tested
… But the meter measures only what reaches its terminals
Errors with Instrument Transformers
• CTs installations can be fully verified in the field
Questionable!
Good
We can verify that the ratio is correct
and constant as burden changes.
Wiring And Junctions Connect The Meter
… What If There Are Wiring Errors Or Poor Connections
Poor Junctions Will Over-Burden The CTs And Reduce Revenue
Integrated Site Test Philosophy
Site Analysis
Site Analysis
Meter Testing
True 3 Phase
Vector Diagram
Power Quantities
CT Testing
True 3 Phase
Voltage and
Current Waveforms
Integrated Site Test Philosophy
Site Analysis
Site Analysis
True 3 Phase
Voltage and Current
Harmonic Analysis
Meter Testing
CT Testing
Integrated SiteSite
Test
Philosophy
Analysis
Meter Testing
Meter Testing
Customer Load Test
Real - World Conditions
Voltage and Current Harmonics
CT Testing
Current and Phase Angle Balance
Load Box Test
Ideal Current and Voltage Waveforms
ANSI Full Load, Power Factor & Light Load
CT – Accuracy – Burden - Load
0.3B1.8 CT
0.6
Percentage Accuracy
0.5
1.8
0.4
Ohm
s
0.3
Site Analysis
Meter Testing
0.2
0.9 Ohm
s
0.2 Ohms
0.1
0.05 Ohms
1
2
5
10
100
Percent Rated Load
CT
Testing
CT
Testing
400
Saturation
Errors with Instrument Transformers
• CTs require a lot of care to insure
accurate measurements.
Burden – Over burden reduces CT accuracy.
 Wiring – Faulty or improper wiring reduces
accuracy by increasing burden.
 Shunt – Failure to remove the safety shunt will
not keep the CT from operating but it will reduce
the readings by 50-80%

Errors with Instrument Transformers
CT was OK
Meter Registration Error
Nameplate=100:5
CT Degraded Wiring
 B, C
Shorted
No
Ground
Installed CT Ratio Error
Wiring Error
Integrated Site Test Philosophy
Site Analysis
Site Analysis
$
Meter Testing
Meter Testing
CT
CT Testing
Questions?