2.. compensación reactiva

CARGAS INDUSTRIALES - COMPENSACION REACTIVA ING. HUBER MURILLO
Expositor : Huber Murillo M.

TIPOS DE CARGAS
Three categories of loads
 RESISTIVES
 INDUCTIVES
 CAPACITIVES
Ohms Ω
Henry Hy
Farad F
R
L
C

 RESISTIVE
 Furnaces
 Electrical heaters
 Electrical irons
 Light bulbs
 ....
 INDUCTIVE
 Transformers
 Induction motors
 Fluorescent lighting
 Induction furnaces
 Welding machines
 Drivers
 ........
 CAPACITIVE
 Capacitors
TIPOS DE CARGAS

OHMIC LOAD.
 RESISTIVE
VAC R
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
Corriente IR = U/R Amper
Potencia P = RI² = U²/R Watts

OHMIC LOAD.
 RESISTIVE
IR
VAC R
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
IR
VAC
IR
ω

INDUCTIVE LOAD.
 INDUCTIVE
VAC L
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
Corriente IL = U / ωL Amper.
Potencia P = U² / ωL var or kvar

INDUCTIVE LOAD.
 INDUCTIVE
IL
VAC L
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
IL
VAC
IL
ω
90°

CAPACITIVE LOAD.
 CAPACITIVE
VAC C
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
Corriente Ic = ω C U Amper.
Potencia P = ω C U² var or kvar

CAPACITIVE LOAD.
 CAPACITIVE
IC
VAC C
-400
-300
-200
-100
0
100
200
300
400
0
45
90
135
180
225
270
315
360
405
450
495
540
VAC
IC
VAC
IC
ω90°

MIXED LOADS.
 Main industrial loads
I
V L
VR
VL
R
The majority of industrial
loadscan be regarded as
comprising resistor and
inductor in series.
V : supply voltage
VR: resistance voltage drop
VL: inductance voltage drop
I : total supply current

I
V L
VR
VL
R
VR
VL
90°
ω
I
V
φ
"I" lags "V" by some angle φ
MIXED LOADS.

φ
MIXED LOADS.

 CAPACITOR CONNECTION
I
L
R
V
IRL
IRL : current through the load
IC : current through the
capacitor
I : total current drawn from
supply
C
IC
MIXED LOADS.

 CAPACITOR CONNECTION
I
V L
R
IC ω
V
IRL
C
IRL
IC
I
ϕ1
ϕ2
ϕ1 ϕ2
ϕ cos ϕ I
MIXED LOADS.

k
W
- Active power (kW)
 performs the work (useful power)
kVA
- Apparent power (kVA)
 total power consumed
kv
ar
- Reactive power (kvar)
 sustains electromagnetic field (non useful power)
REACTIVE POWER COMPENSATION.

BASIC CONCEPTS.
kVA
Apparent power
φ
Active or useful power
kW
Reactive
power
kvar
kvar
Power factor
cos φ = kW / kVA
HOW CAN WE IMPROVE THE PF
CORRECTION AND THUS REDUCE THE
CONSUMED POWER?

kW
Kvar2
The capacitor connected in parallel will
draw kvar in the same way than the
load but in phase opposition (leading)
kVA
kvar1
BASIC CONCEPTS.

BASIC CONCEPTS.
φ1
kW
kvar
kVA1
φ2
kVA2
kvar2
kvar1

)2tan1kW(tankvarc
kW
kvar
tan
kvar²kW²
kW
cos
kvar²kW²kVA
kVA
kvar
sin
kVA
kW
cos
−=
=
+
=
+=
=
= kW
kvar
kVA
φ
BASIC CONCEPTS.
φφ
φφ
φ
φ
φ φ

Power factor correction chart
Kvar = k * kW
Desired PF
InitialPF

0.46
Nomogram
Kvar = k * kW

kW=410
kVA1=586
kvar1=419
φ1
Ejemplo

kW=410
kVA1=586
kvar1=419
φ1
284
Carga compensada

kW=410
kVA1=586
kvar1=419
φ1
kvar2=135284
Carga compensada

kW=410
kVA1=586
kvar1=419
φ1 φ2
kVA2=432
kvar2=135284
Carga compensada

Advantages of a good power factor

Transformers and distribution cables
lightened ( I )
0.70.95
27%

Reduced Joule losses ( RI² )
46
cos φ final values
cos φ initial values
% reduction in losses
CABLES

1150
6000
TRANSFORMER

kVA output reduced
cos φ initial
% kVA recovered
0.75

Voltage drop in transformer
5.1
Voltage drop
cos φ
0.6
Low losses
Normal losses
VOLTGE DROP
Cos ? = 0.6 * 5.1%
Cos ? = 0.6306
Cos φ = 0.6306
φ = 50.906

Typical PF encountered in industry

Energy saving calculation.
400 kVA
400 V
P=80 kW
cos φ = 0.75
P=170 kW
cos φ = 0.75
1 cable
70 mm²
20 m
2 cables
70 mm²
100 m
A B

Consumer's electricity bill:
• Monthly kWh consumed = 70125
• Monthly kvarh consumed = 63081
• Assuming an activity of :
340 days/year
15 hours/day
• Average kW = 70125/425 = 165 (66% of the full load)
• Average kvar = 63081/425 = 148
• Average kVA = √165² + 148² = 222
• Average P.F. = kW/ √kW² + kvar² = 0.744

Min P.F. value to avoid penalty : 0.93
capacitor required = kW (tgφ1 - tgφ2)
=165 (0.898 - 0.395) = 83kvar
(in practice cap. size is increased by 5 to 10% to ensure a
P.F.> 0.93)
New situation
kW = 165 (unchanged)
kvar = 148 - 83 = 65 ()
kVA = √165² + 65² = 177 () (222 previously)
Monthly demand (kVA) is reduced by 20%

Cable losses
Cos φ = 0.75
Workshop A :
I = P*0.66/ √3 V cos φ
= 80000 * 0.66/ √3 400 0.75 = 102A
Cable losses : P = 3 RI²L (R= ρ1/S)
= 3 * 246.10-6
Ω/m * (102)² * 20 =154W
5100 h/year P = 785kWh
Workshop B :
I = 170000 * 0.66/√3 400 0.75 = 216A
Cable losses : P = 2 (3RI²L)
= 2 * 3 * 246.10-6
* (216/2)² * 100 = 1722W
5100h/year P = 8782 kWh

Cable losses
Cos φ : 0.93
Workshop A:
- I = 102 (0.75/0.93) = 82A
- Cable losses = 154 (82/102)² = 100W
- Cable losses/year = 150kWh
Workshop B:
- I = 216 (0.75/0.93) = 174A
- Cable losses = 1722 (174/216)² = 1117W
- Cables losses/year = 5697kWh

Transformer losses
Before correction:
Total losses = 1000 + 5000 [(80+170) 0.66]² / (0.75 * 400)= 2513W
Total losses/year = 2513X5100 = 12814kWh
Total kWh = 785 + 8782 + 12814 = 22381
After correction:
Total losses = 1000 + 5000 [(80+170) 0.66]²/ (0.93 * 400) = 1984W
Total losses/year = 10118kWh
Total kWh/year = 510+5697+10118 = 16325
kWh reduction/year = 22381 - 16325 = 6056kWh
27% reduction

POWER FACTOR CORRECTION
The main reason for installing power capacitors is to
reduce reactive power costs and avoid the penalties.
Typical pay back period is less than 1-2 years.
Sometimes as little as a few months.
TYPICAL INSTALLATION
• Individual compensation of large motors (>50kW ≈ 70hp)
• Fixed compensation of transformers (+/-10 % of transformer rating)
• Automatic capacitor bank to compensate varying load

Locating capacitors on your system
Capacitors may be installed at various locations on your
electrical system.
1 : Capacitors on the incoming plant service
2 : Capacitors on the main bus
3 : Capacitors on the bus for various feeders
4 : Capacitors a the individual load point
Capacitor location
1 2 &3 4
Technical approach Best
Flexibility Least Less Best
Savings Least less Max.
Cost per kvar Least Lower Highest

TRANSFORMER COMPENSATION
- Increased useful capacity
- Reduced losses
- Reduced voltage drop
Degree of compensation :
1. "Rule of thumb" : +/- 10 % of transformer's nominal rating.
2. Calculation based on the individual transformer and its load pattern.
Note : check for resonance between transformer and capacitor.

Individual transformer compensation
The resonant frequency can be calculated from the following
formula :
f fp
Psc
Pc
=
f = resonant frequency
fp = power frequency
Psc = short circuit power of the transformer (kVA)
Pc = power of the capacitor (kVAR)
If the frequency obtained is too close to that of a harmonic, the
value of the capacitor rating should be modified.
Most common harmonic frequencies, 3rd, 5th, 7th, etc...

MOTOR COMPENSATION
Methods for determining capacitor
rating for motor compensation
1.- Rule of thumb Qc = 40% of motor KW .
rating.
2.- Use of table the speed and motor power .
into acount
3.- Calculation based on exact individual
. motor charasteristics.

AUTOMATIC BANK COMPENSATION
Advantages of automatic capacitor banks :
- Regulation of cos φ.
- Better utilisation of the capacitor compared to individual compensation.
- Eliminates the possibility of overcompensation.

AUTOMATIC BANK COMPENSATION
Points to consider for automatic banks
• Choice of regulator characteristics (c/k and tolerance) and step size to
avoid hunting.
• Correlation between minimum interval between switching and discharge
device of capacitor to avoid energising a charged capacitor.
• Disconnecting of all steps in case of a mains outage.
• Insensitivity to harmonics.
• Possibility to extend existing banks without changes in the control
equipment.

LVCP
THE NEW CHOICE FOR POWER
FACTOR CORRECTION
BANCO DE CONDENSADORES ING. HUBER
Compact
Modular
Safe
Reliable

Compact Small dimensions
210 mm
200 mm78 mm
Compact High
power density
 20 kvar
@ 400/415 V

Modular
Terminals sized for
common cable shoes
Built-in safety discharge
resistors (<75V in 3 min.)
Enclosure with double
casing insulation

Modular
Interconnection bars
Fixation holes
Clips system for group
assembly

Modular
Easy and quick assembly
of capacitor modules
DIN rail fixation

Examples of LVCP module assembly
30 kvar = 15 kvar + 15 kvar
400V/50Hz

Examples of LVCP module assembly
400V/50Hz
45kvar =
15kvar + 15kvar + 15kvar
50kvar =
16.7kvar + 16.7kvar + 16.7kvar
60kvar =
20kvar + 20kvar + 20kvar

Modular
External discharge device
Safe discharge
< 50V in 1
minute
Protective cover IP20

Safe
Built in safety discharge resistors
Fuse
Pressure sensitive disconnector
Thermo-setting resin
Dry type self healing capacitor winding
Insulating enclosure

system
Self-healing +
Internal fuse +
Pressure sensitive disconnector

Reliable
In-house
metallized film
 Voltage withstand capability
 Peak current
 Capacitance stability
 Life
 Self-healing
 Losses

Reliable
Automatized
manufacturing
process
 Controlled performance
 Repeatable quality
IEC 60831 1&2
ISO 9001
ISO 14001

Reliable
Comprehensive
testing
• Ageing
• Temperature
• Humidity
• Dielectric
• Self-healing
• Current
• Voltage

Range (50Hz)
0
2.5
5
7.5
10
12.5
15
17.5
20
230
400
415
450
465
KVAR

Range (60Hz)
0
2.5
5
7.5
10
12.5
15
17.5
20
220
240
380
440
450

THEN YOU ABB
YOUR choice for
Power Factor Correction

2.. compensación reactiva

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