How to Maintenance LV Capacitor Bank Rev.pdf

Low Voltage Capacitor Bank
Component, Maintenance for Capacitors
tawat.puangthong@th.abb.com, 08 Oct,2014

1. Circuit Breaker
2. Magnetic Contactor
3. Reactor
4. Capacitor Unit
5. Heater
6. Electrical Cooling Fan
7. Temperature control
8. Power Factor Controller
Component Of Capacitor Bank (1)
2

1. Circuit Breaker
- Protection for capacitor when a fault current
condition occurs.
Figure 1. Circuit Breakers
3

2. Magnetic Contactor
- For Switching on - off capacitor.
Figure 2. Magnetic Contactor
4

3. Reactor
- Installing single phase damping reactors In
series on each phase of the capacitor bank makes it
possible to reduce the switching current to value that
are acceptable for the corresponding operating
device.
Figure 3. Reactor
5

4. Capacitor unit
- Low voltage capacitors are generated the
Reactive power.
Figure 4. Capacitor Units
6

5. Heater
- For moisture removal occurs within the cabinet.
Figure 5. Heater
7

6. Electrical Cooling Fan
- For ventilation inside the cabinet when the
temperature more than the value setting.
Figure 6. Electrical Cooling Fan
8

7. Temperature Control
- For control the temperature inside the cabinet.
Figure 7. Temperature Control
9

8. Power Factor Controller
- For power factor correction control
- Measurements and monitoring
- Communication
Figure 8. Power Factor Controller
10

Figure 9. Schematic Diagram
Schematic Diagram For LV Capacitor Bank (2)
Schematic Diagram For LV Capacitor Bank (2)
11

Figure 10. Logic Diagram
Logic Diagram For LV Capacitor Bank (2)
Logic Diagram For LV Capacitor Bank (2)
12

Safety Regulation
 The installation, operation and maintenance of LV capacitor
bank must only be carried out by authorized installers.
 Wait at least 5 minutes after the power supply has been
disconnected.
 After maintenance and before re-applying the power supply
to unit, check that its enclosure is properly closed and that no
items or tools were left inside that could cause a short-circuit.
Safety Regulation
 The installation, operation and maintenance of LV capacitor
bank must only be carried out by authorized installers.
 Wait at least 5 minutes after the power supply has been
disconnected.
 After maintenance and before re-applying the power supply
to unit, check that its enclosure is properly closed and that no
items or tools were left inside that could cause a short-circuit.
Maintenance of LV Capacitor Bank (3)
13

1. Maintenance with the capacitor bank connected
 Monthly
- Records of capacitor current, power factor, system
voltage, load current and etc.
- Check the protection fuses status.
- Check all electrical connection point with the thermo
scan.
2. Maintenance with the capacitor bank disconnected
14

 Six-Monthly
- Visually inspect the capacitors.
- Check the protection fuses status.
- Check that the ventilation fan is working properly.
- Check all electrical connection point with the
thermo scan.
- Check that there is no current in any of the phases,
Is not lower than 75% neither greater than 120% of the
rated value. Check also that there is no a phase
unbalance greater than 15%.
15

Capacitor
Rating
(kVAR)
Rated Current
(A)
Rated
Voltage
(V)
Rated
Capacitance
Phase-Phase (F)
20 28.9 400 198.86
25 36.1 400 248.58
40 57.8 400 397.72
50 72.2 400 497.16
Table. 1 Nominal consumption of the capacitor steps, depending on its power
Notes:
- When the consumption of the steps is 25% less than stated in and the voltage is
within the tolerance limits, this is a sign of degradation of the capacitors. These
must be replaced with a suitable spare part if these symptoms are detected in
a step.
- When the consumption of the steps is 10% more than state in, this can be
caused by the presence of resonances. If this is detected, measure the THD(V)
of network voltage (Should be below 5%)
16

 Six-Monthly
- Check the tightness of all terminal connections on
the difference power elements.
- Inspection of the fuses. The fuses and fuse bases
should not be blackened and their connections must be
tight.
Figure 9. Fuse Link
17

 Six-Monthly
- Cleaning the dirt of the capacitor bank’s cabinet.
- Control the environmental temperature ( average of
30C. In accordance with IEC 60831 ).
- Check the capacitor’s microfarads of the different
steps. An indirect verification can be performed by checking
that the consumption matches the value stated in table1.
with a maximum deviation of ± 10%.
Figure 10. Capacitance measurement
18

 Six-Monthly
- Check the insulation resistance, is not lower than 5.0 M
- Inspection of the fuse,
- The fuse and fuse bases should not be blackened
and their connections must be tight. The tightening torques
for fuse bases are as indicated in the table below:
Figure 11. Fuse bases
19

 Six-Monthly
- Check the tightness of cables and terminals is
show in table 2
Table. 2 Tightening torques of the power cables to the fuse bases
Fuse Base Torque (Nm)
NH-00 15.2
Figure 12. Cable not tightness
20

How to check ?
1. Tightening
- Contactor (ABB)
Only use the screw driver Pozidrive type for retightening
Do not use Phillips type screw driver.
Figure 13. Screw Driver Pozidrive Type
21

How to check ?
1. Tightening
- The power cable and reactor.
- The power cable and bus bar.
Table. 3 Standard Tightening torque for screw thread.
Bolt Grade 8.8
Bolt & Nut size
Tightening Torque
(ft-lb.)
Tightening Torque
(Nm.)
M3 1.1 1.5
M4 2.58 3.5
M5 5.15 7
M6 9.58 13
M8 20.64 28
M10 36.86 50
M12 55.29 75
22

How to check ?
1. Tightening
- The cables on the capacitor terminal.
Bolt size of capacitor unit Torque
M6 3
M8 6
M10 10
M12 15.5
Table. 4 Standard Tightening torque for capacitor terminal
Figure 14. Capacitor Terminal
23

How to check ?
2. Capacitance measurement
-By LCR and Multi Meter
Figure 15. LCR Meter Figure 16. Multi Meter
μF.
497.16
x400x400
4x3.142x50
50x10
C
U
F
4π
kVARx10
C
9
9
2
N
N



24

How to check ?
3. Insulation resistance test
-By Megger Ohm Meter
Figure 17. Megger Ohm Meter
25

How to check ?
4. Current measurement
- By Digital Clamp Meter
Formula for calculating rated current of capacitor :
Figure 18. Digital Clamp Meter
Amp.
72.2
x400
3
50x1000
.V
3
kVAR
I



I
26

27 Question ?
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How to Maintenance LV Capacitor Bank Rev.pdf

How to Maintenance LV Capacitor Bank Rev.pdf

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