7.1.2 The breakdown tree diagram used for the diagnosis of the breakdown in the studied system

During corrective interventions, most of the workers overcome the breakdown without trying to eliminate their causes or without investigating on the causes of the breakdown. The exploitation of maintenance files shows that many elements were replaced within a short period of time. This situation led to frequent breakdown of the system even though the bad element was replaced. It became very important to put in place a breakdown diagnosis method in order to eliminate breakdown and causes. The breakdown tree technique helps to graphically represent the possible combinations of the events that permit the realization of a non-needed predefined event. The breakdown tree is then made of levels of events linked by gate (initially logic gate). By using this representation and a logical deduction (moving from


effects to causes), it is possible to cast out the causes from the effects, from the nonneeded event to base events, independent to one another and probable (Figure 15).

In PV water pumping systems, the main objective is to collect data, diagnosing the system and proposing and implementing solutions that will optimize the operation of the system in order to satisfy the water need of the population all over the year. Indeed from the collected and measured data, Tables 4 and 5 show the

Failure of the photovoltaic pumping systems (events E1, E2, E3, and E4 are shown in Figures 17–20).

7.2 Photovoltaic water pumping systems

Components Failures Possible causes Solution

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

diodes

flaw

• Diode bypass short circuit • Defective module in serial

• Cutting connection wires • Defective anti-return

• Shadow-related design

• Corrosion or looseness of the connection terminals

• Dirt of the panels

• Defective fuse

• Inverter failure • Defective power cables or poor tightening at the Inverter input

• Clogged strainer • Defective wheels • Lowering of the water

• Defective phases • Low voltage

• Defective mechanical sea

Their solutions to the possible failures in a photovoltaic pumping system according to FMECA.

level

• Replace the diode

• Replace the faulty diode

• Clean the modules

• Replace the inverter

• Unclog the strainer • Change the wheels

during operation

• Replace the phases • Change the seals

terminals • Change the fuse

• Check and replace the faulty module

• Check and replace the connection wire

• Clear the objects causing the shadow

• Tighten or change the connection

• Remove or replace the power cable

• Check the water level is at least 1 m above the suction body of the pump

Vm,PV <Vref,PV T = 25°C E = 800 W/m<sup>2</sup>

DOI: http://dx.doi.org/10.5772/intechopen.83730

Im,PV < Iref,PV T = 25°C E = 800 W/m<sup>2</sup>

PmPV <PrefPV T = 25°C E = 800 W/m<sup>2</sup>

Pm,PV ¼ 0 T = 25°C E = 800 W/m<sup>2</sup>

T = 25°C E = 800 W/m<sup>2</sup>

Not functioning (pumping stop) E = 800 W/m<sup>2</sup>

Not starting E = 800 W/m<sup>2</sup>

Inverter PInv ¼ 0

Pump Qm ¼ 0

Engine Qm ¼ 0

Table 5.

Figure 16.

129

Photovoltaic generator (PVG)

Table 4. Possible failures on the photovoltaic pumping system according to FMECA.


On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon DOI: http://dx.doi.org/10.5772/intechopen.83730

#### Table 5.

are Figure 14(b): dust deposit, bad fixing on their supports, and accidental cracking. The first two causes which do not lead to the stop of the system decrease the efficiency of the system (output energy), while the third cause leads to the stop of

7.1.2 The breakdown tree diagram used for the diagnosis of the breakdown in the studied

During corrective interventions, most of the workers overcome the breakdown without trying to eliminate their causes or without investigating on the causes of the breakdown. The exploitation of maintenance files shows that many elements were replaced within a short period of time. This situation led to frequent breakdown of the system even though the bad element was replaced. It became very important to put in place a breakdown diagnosis method in order to eliminate breakdown and causes. The breakdown tree technique helps to graphically represent the possible combinations of the events that permit the realization of a non-needed predefined event. The breakdown tree is then made of levels of events linked by gate (initially logic gate). By using this representation and a logical deduction (moving from

the system

• Decrease of tension

• Decrease in current and flow

• Low water flow

• No water flow

• No flow of water

• No flow of water Observable parameter

• Voltage • Current

• Current

• Input power • Power output

• Voltage • Current

• No power • Voltage

Criticality GOD C

5 5 4 100

9 7 4 252

9 7 4 252

9 7 4 252

• Flow rate 9 7 4 252

• Voltage 5 2 2 20

• Current 3 5 2 30

the system which necessarily needs a replacement.

Components Failures Possible causes Effects on

circuit

serial

wires

diodes

flaw

• Diode bypass short

• Defective module in

• Cutting connection

• Defective anti-return

• Shadow-related design

• Corrosion or looseness of the connection terminals • Defective fuse

• Dirt of the panels

• Inverter failure • Defective power cables or poor tightening at the inverter input

• Clogged strainer • Defective wheels • Lowering of the water

• Defective phases • Low voltage • Defective mechanical

level

sea

Possible failures on the photovoltaic pumping system according to FMECA.

Vm,PV <Vref,PV T = 25°C E = 800 W/m<sup>2</sup>

Im,PV < Iref,PV T = 25°C E = 800 W/m<sup>2</sup>

PmPV <PrefPV T = 25°C E = 800 W/m<sup>2</sup>

Pm,PV ¼ 0 T = 25°C E = 800 W/m<sup>2</sup>

T = 25°C E = 800 W/m<sup>2</sup>

Not functioning (pumping stop) E = 800 W/m<sup>2</sup>

Not starting E = 800 W/m<sup>2</sup>

Inverter PInv ¼ 0

Pump Qm ¼ 0

Engine Qm ¼ 0

Table 4.

128

system

Maintenance Management

Photovoltaic generator (PVG)

Their solutions to the possible failures in a photovoltaic pumping system according to FMECA.

effects to causes), it is possible to cast out the causes from the effects, from the nonneeded event to base events, independent to one another and probable (Figure 15).

#### 7.2 Photovoltaic water pumping systems

In PV water pumping systems, the main objective is to collect data, diagnosing the system and proposing and implementing solutions that will optimize the operation of the system in order to satisfy the water need of the population all over the year. Indeed from the collected and measured data, Tables 4 and 5 show the

Figure 16. Failure of the photovoltaic pumping systems (events E1, E2, E3, and E4 are shown in Figures 17–20).

failures we may encounter in our installation as well as the possible causes and solutions.

To facilitate the procedure of these pumping stations, breakdown tree diagram is constructed in a deductive manner as highlighted in the Figure 16. For each event E1, E2, E3 and E4 in the Figure 16, breakdown tree diagram for failures encountered are presented respectively in the Figures 17–20.

Figure 19. Pump failure tree.

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

DOI: http://dx.doi.org/10.5772/intechopen.83730

Figure 20.

131

Pump unit failure diagram.

Figure 17. Photovoltaic generator failure tree.

Figure 18. Inverter failure tree.

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon DOI: http://dx.doi.org/10.5772/intechopen.83730

Figure 19. Pump failure tree.

failures we may encounter in our installation as well as the possible causes and

tered are presented respectively in the Figures 17–20.

To facilitate the procedure of these pumping stations, breakdown tree diagram is constructed in a deductive manner as highlighted in the Figure 16. For each event E1, E2, E3 and E4 in the Figure 16, breakdown tree diagram for failures encoun-

solutions.

Maintenance Management

Figure 17.

Figure 18. Inverter failure tree.

130

Photovoltaic generator failure tree.

Figure 20. Pump unit failure diagram.
