6. Maintenance and fault detection techniques in PV systems

The field inspection process is a key to the development of healthy and safe PV systems. Many works consolidated the most important aspects of a field inspection

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

of photovoltaic system which is the competency of the contractor and installer without taken into account life service of each element and their implication on the failure of the system [33, 34]. Diagnosis procedures consist on visual inspection procedures (array inspection, wire inspection, inverter inspection, inspection of module, and array grounding) and performance monitoring (performance verification, displays, design software, data acquisition systems, sensors) [34]. One of the most valuable techniques for identifying existing problems and preventing future problems is to walk to the site and conduct a thorough visual and hands-on


Table 3.

Parameters to be measured in PV systems in real time [35].

sun. The configuration of a field is performed as follows: 51 solar panels all divided into 03 strings of 17 panels. Two pumps P1 and P2 were associated. The characteristics of the PV module used, inverter and motor pump, are specified in Tables 1 and 2.

Max DC input voltage 750 V Rated voltage 3 380–400–415 V Recommended MPP voltage 500–600 V Rated current 13.0–13.0–13.4 A Adapting motor power 9.2–11 kW Starting current 480–530–550%

Rated AC output current 24A Rated speed 2850–2860–

Output frequency 0–50/60 Hz Starting method Direct online Conversion efficiency Max 98% Rated flow 71 m3

Ambient temperature 10 to 50°C Rated head 81 m

Denomination Symbol Value Rated maximum power (Pmax) Pmax 255 Wp Maximum power current (Imp) Imax 8.13 A Short circuit current (Isc) Isc 8.61 A Maximum power voltage (Vmp) Vmp 31.52 V Open circuit voltage (Voc) Voc 37.92 Maximum system voltage 1000 V Operating temperature (40 + 85)°C Temperature coefficient of Isc αIsc 0.58%/°C Temperature coefficient of Voc βVoc 0.33%/°C Temperature coefficient of power 0.41%/°C

Inverter Solartech PB11KH Grundfos SP17-10 pump Denomination Value Denomination Value Rated power 11 kW Motor type MS4000 Max solar input power 16 kW Rated power—P2 5.5 kW

pump

15 A Mains frequency 50 Hz

Cos phi—power factor 0.85–0.81–0.76

5.5 kW

2870 rpm

/h

Input string 4 Power (P2) required by

380-440 V

Table 1.

Characteristics of the PV module used in PVWPS.

Adapting motor voltage 3PH

Characteristics of the inverter and the motor pump.

Max input current of each

Maintenance Management

string

Table 2.

122

The field inspection process is a key to the development of healthy and safe PV systems. Many works consolidated the most important aspects of a field inspection

6. Maintenance and fault detection techniques in PV systems

inspection of the PV system components. During these inspections, the parameters to be measured in real times are specified in Table 3.

When problems are identified, we can use breakdown tree diagrams [36, 37]. Breakdown tree diagram gives a graphical description of the different events that lead to a breakdown resulting to the non-reliability and the stop of the system [37]. The breakdown tree diagram is constructed in a deductive manner. It starts with the peak event right up to the elementary event in arborescence. The peak event for which we seek the probability is often called "feared." We generally use AND and OR logic gates to define the probability of what is at the cause of the event, to put the situation (what is to be resolved) at the head of the diagram and link it to its causes (events that can be at the origin) by the gate. Once the diagram has been archived, if there is any breakdown, interventions are done from the bottom of the diagram to the top where the problem is detected in the system. Figure 10 shows that for the "feared" event to archived, either event E1 or E2 must have been archived. In the same manner, for the event E1 to be archived, either the base event e1 or e2 must have been archived, and for the event E2 to be archived, both base events e1 and e2 must have been archived at the same time.

The failure modes, effects and criticality analysis (FMECA) which is a rigorous and preventive method for identifying potential failures of a system and elements, actions have been defined to be taken to eliminate these failures, reduce their effects, and detect and prevent causes. The method is part of an eight-step process [38] as seen in Figure 11. Several criteria can be used to determine the criticality index. In practice, we assign three notes (each on a scale of 1–10) for each trio cause-mode-effect:


The criticality index is obtained by C ¼ G ∗ O ∗ D (1)

7. Case study

Figure 11. FMECA approach.

125

7.1 Photovoltaic backup systems

which were kindly followed.

In order to better study the impact of the two types of maintenance on the system, Figure 12 shows the frequent preventive and corrective maintenance operations carried out on installed PV backup systems during the period 2012–2015,

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

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

Figure 12(a) presents the number of preventive and corrective interventions realized on one site within a period of 4 years. This illustration shows the importance of preventive maintenance on PV systems. In effect, the more preventive maintenance are done, the less there are corrective operation realized. It is the case for the years 1, 3, and 4. To estimate the element lifetime before failure, the exploitation of the maintenance files indicated that 25 batteries were damaged on the 82 installed as shown in Figure 12(b); thus, batteries contributed to 64.9% of the breakdowns

Figure 10. Breakdown tree method.

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

Figure 11. FMECA approach.

inspection of the PV system components. During these inspections, the parameters

When problems are identified, we can use breakdown tree diagrams [36, 37]. Breakdown tree diagram gives a graphical description of the different events that lead to a breakdown resulting to the non-reliability and the stop of the system [37]. The breakdown tree diagram is constructed in a deductive manner. It starts with the peak event right up to the elementary event in arborescence. The peak event for which we seek the probability is often called "feared." We generally use AND and OR logic gates to define the probability of what is at the cause of the event, to put the situation (what is to be resolved) at the head of the diagram and link it to its causes (events that can be at the origin) by the gate. Once the diagram has been archived, if there is any breakdown, interventions are done from the bottom of the diagram to the top where the problem is detected in the system. Figure 10 shows that for the "feared" event to archived, either event E1 or E2 must have been archived. In the same manner, for the event E1 to be archived, either the base event e1 or e2 must have been archived, and for the event E2 to be archived, both base

The failure modes, effects and criticality analysis (FMECA) which is a rigorous and preventive method for identifying potential failures of a system and elements, actions have been defined to be taken to eliminate these failures, reduce their effects, and detect and prevent causes. The method is part of an eight-step process [38] as seen in Figure 11. Several criteria can be used to determine the criticality index. In practice, we assign three notes (each on a scale of 1–10) for each trio

• The grade G: severity of the effect, the consequences on the client/user

• The grade O: the probability of occurrence, the frequency of occurrence

• The grade D: the probability of non-detection, the risk of non-detection

The criticality index is obtained by C ¼ G ∗ O ∗ D (1)

to be measured in real times are specified in Table 3.

events e1 and e2 must have been archived at the same time.

cause-mode-effect:

Maintenance Management

Figure 10.

124

Breakdown tree method.
