Transcript Reactive Power - Myron Zucker, Inc.

2008 DTE/ESD Energy Conference and Exhibition
Energy Efficiency Implementation Case Study
Power Factor Correction Case Study
-Power Overview
- Power Factor Penalties
-Case Study
May 6, 2008
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What is Power Factor
Power Factor is a measure of how effectively power is used
Inductive loads require two types of power to operate:
Active Power
Reactive Power
Apparent Power
Active Power – Performs the work
Reactive Power – Maintains the electro-magnetic field
Apparent Power – Vector sum of Active and Reactive power
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What is Power Factor
Vector summing power
Active
kW
Power
θ
90˚
Apparent
kVA
Power
Reactive
kVAr
Power
Power factor is the ratio of
active power
kWtotoapparent
kVA
power
kW
kVA
= pf
cos θ = pf
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arctan
kVAr
kW
=θ
What is Power Factor
Perfect
Good
Poor
ThePower
Power
Difference
PowerFactor
Factor
Factor
kW
θ>
= 32˚
<
0
kVAr = 0
kVA
No Penalty
kVAr
kVA
Unity
kVA
kVAr
Penalty
kW
kVA
= .85
>
<
1
cos
cosθ 0<
> =.85
1
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arctan
kVAr
0
kW
= 32
<
>
0
Power Factor Penalty
Example of DTE penalty rates (issued January 1994)
Power Factor
Penalty
.850 and higher
None
.800 to .849
1%
.750 to .799
2%
.700 to .749
3%
<.700
25%
•Penalty is applied to all metered quantities
•Power Factor less than .700 is not permitted and corrective
equipment must be installed.
•25% penalty applied after two consecutives months below .700
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Power Factor Penalty
The Mechanics of Power
= kW
= kVAr
The Utility Company
Your Facility
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Power Factor Penalty
The
The
Mechanics
MechanicsWithout
With Capacitors
Capacitors
400 kW
447 kVA
Power
Power Factor
Factor == .80
.89
1% Penalty
500 kVA
100 kVAr
200 kVAr
300 kVAr
Your
Capacitor
Bank
Catches and stores
the kVAr before it
gets back on to the
utilities grid
The Utility
Your Facility
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Power Factor Penalty
Example of DTE Utility Bill
Charges for 03/22/2008 through 04/19/2008
Power Supply Charges:
Power Supply Demand
Power Supply Energy:
Power Supply Energy
Off-Peak Discount
Surcharges:
Regulatory Asset Recovery Surcharge
Power Supply Cost Recovery Factor
1,080 KW
@ $
10.93
(See 1 Above)
653,047 KWH
480,247 KWH
@ $
@ $
.0236400 Per Total KWH
-.0030000
15,438.03
-1,440.74
653,047 KWH
653,047 KWH
@ $
@ $
.0008980 Per Total KWH
.0086900 Per Total KWH
586.44
5,674.98
Sub Total:
Delivery Charges:
Service Charge
Distribution:
Distribution Demand -PV
Distribution Energy -PV
Surcharges:
Nuclear Decommissioning
U-14838 Rate Reduction Credit
Securitization Bond Charge
Securitization Bond Tax Charge
Choice Implementation Surcharge
11,804.40
32,063.10
275.00
1,080 KW
653,047 KWH
@ $
@ $
653,047
653,047
653,047
653,047
653,047
@
@
@
@
@
KWH
KWH
KWH
KWH
KWH
Sub Total:
Invoice Subtotal
3% Power Factor Penalty Based On 0.746 Power Factor
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$
$
$
$
$
4.55 (See A Above)
.0070300 Per Total KWH
.0012340
-.0020410
.0036600
.0012100
.0005000
Per Total KWH
Per Total KWH
Per Total KWH
Per Total KWH
Per Total KWH
4,914.00
4,590.92
805.86
-1,332.87
2,390.15
790.19
326.52
12,759.77
44,822.88
1,336.44
Power Factor Penalty
Example of DTE Utility Bill
Detail Charges
For Service at: xxxxxx
Outage Contact Number: xxxxxx
Invoice: xxxxxx
Billing Period: 03/22/2008 through 04/19/2008
Days Billed: 29
Metering Information
Meter
Number
xxxxxxx
xxxxxxx
Start
Date
03/22
03/22
Start
Read
1,932.0A
2,297.3A
Stop
Date
04/19
04/19
Stop
Read
2,129.0A
2,518.0A
Read
Difference
197.0
220.7
Total KVARH
Total KWH
Units
Multiplier
5,600.000
5,600.000
Usage
Used
1,103,200.0
1,235,920.0
Type
P-KVARH
P-KWH
kVARH = 1,103,200.0
1,103,200
1,235,920.0
kWH = 1,235,920
kWH = 1,235,920
kVARH = 1,103,200
kW
kVA
kVAH = 1,656,668
= .746
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Sizing Power Factor Capacitors
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Sizing Power Factor Capacitors
Avg Kilowatthours Used Per Day This Period
22,519 KWH
Billing Status Information
On-peak Billing Demand
65% High OP Bill Dmd June-Oct prec 11 mths
Rate Minimum Demand (Site)
Highest Single Billing Demand
80
Current PV High Monthly Demand
50% of the Contract Capacity for PV
68 0.328
Primary Voltage Maximum Demand
69 0.299
Coincidental Max Onpk KW Dmd at Site
70 0.270
Primary Voltage Maximum OnPeak Demand Reactive Demand
71 0.242
Percent Change
72 0.214
Avg Kilowatthours Used Per Day A year Ago
73 0.186
Power Factor (ratio) for all voltage
74 0.159
Total Number of days in the Billing Period
75 0.132
Excess KVAR for PF less than .8
Contract Capacty for Location
76 0.105
Avg
Avg Kilowatthours
Kilowatthours Used
Used Per
Per Day
Day This
This Period
Period 77
0.079
(KVAR) Coincidental Max Demand at Site
1,080 KW
ESTABLISHED
Average kW = 22,519
938
702 KW/ 24 = ESTABLISHED
50 KW
Desired Power
(%)
1,080Factor
KW
Original Power Factor (%)
1
3
6
8
A
B
C
W
85 = 938
90
1,080
kW
540
0.459
0.429
0.400
0.372
0.344
0.316
0.289
0.262
0.235
0.209
0.183
0.156
0.130
θ
kVA = 1,257
78
79
80
0.052
0.026
0.000
KW 95
0.594 KW
0.750
1,080
KW
0.565
0.720
1,080 KW
0.536
0.692
0 KVAR
0.508
0.663
56 PCT
0.480
0.635
144,406 KWH
0.452
0.608
74 PCT
0.425
0.580
29 DAYS
0.3980 KVAR
0.553
1,080
KW
0.371
0.526
22,519
KWH
22,519
KWH
0.344
0.500
0 KVAR
0.318
0.292
0.266
0.474
0.447
0.421
ESTABLISHED
ESTABLISHED
100
ESTABLISHED
ESTABLISHED
1.078
ESTABLISHED
1.049
ESTABLISHED
1.020
0.992
0.964
0.936
0.909
0.882
ESTABLISHED
0.855
0.829
0.802
0.776
0.750
11:30
11:30
00:00
00:30
00:30
22:30
00:30
11:30
02/20/2007
00:00
kVAr = 837
938 * 0.398 = 373 or 375 kVAR
required to improve power factor from .75 to .90
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03/22/2008
09/21/2007
01/22/1994
03/22/2008
03/22/2008
05/19/2007
03/22/2008
03/22/2008
Sizing Power Factor Capacitors
Information Required to Size and Locate Capacitors
• 12 months of electrical utility bills
• Electrical layout of facility
–Motor location and sizes
–Transformer sizes
• Variable Frequency / Speed Drives
• Harmonic study
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Case Study
Oaks Correctional Facility
Manistee, Michigan
• 4 housing units; 4 large buildings which include food services,
health care, recreation, maintenance, warehouse storage,
administrative offices.
• HVAC, compressors, lighting, hydraulic motors
• Poor power factor
• $650 average power factor penalty/month
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Case Study
Oaks Correctional Facility
Solution for Oaks Correctional Facility
• 320 kVAr was calculated for facility to reach the target power factor
• 30 kVAr installed at the switchgear in each of the 4 housing units
• 50 kVAr capacitor installed at the switchgear in each large building
• Total cost of capacitors: $6000
• Penalty eliminated plus rebate of $200/month = $850 savings/month
• Payback of less than one year achieved, even considering installation
costs.
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Benefits of Improving Power Factor
• Elimination of Power Factor Penalties
• Where applicable
• Increase Capacity in Electrical System
• Reduction of I2R Losses
• When capacitors are located close to inductive load
• Up to 4% savings for that load
• Improves Voltage on System
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Power Factor Capacitors
• Capacitor Tolerances
– United States: IEEE 18-2002
• Capability
–
–
–
–
Line to Neutral
Line to Line
Current
Var Output
110% Continuous
120% Continuous
180% Continuous
135% Continuous
– Europe: CE Standards call for 8 hour period
• Remember that these standards are
Recommendations, not Code, and can
therefore be ignored by manufacturers
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Power Factor Capacitors
• Electric Power Research Institute (EPRI)
•
“You can only save energy that is wasted”
• Infrastructure (system) losses generally 1-4%
• Includes I2R losses (Line Losses)
• Beware of large energy saving claims where
capacitor are used
• Claims of large savings on your “losses” is NOT equal
to large savings on your entire energy bill. A claim of
15% savings on energy “losses” at a facility with 2%
line losses would total at most a .3% savings on the
entire energy bill. (e.g. 15% x 2% = 0.3%)
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