Installation and troubleshooting of solar pv power plants

1. Installation and troubleshooting of
solar PV power plants
S.Gomathy M.E.,M.B.A
Assistant Professor
Department of EEE
Kongu Engineering College

2. Preparation for Installation
• Obtain necessary permits from the building and
electricity authorities before installation.
– Keep all safety equipment ready to be used during
installation.
– Ensure all equipment inclusive of spares is
received, tested and available at hand for
installation.
– Review installation instructions for each
component and become familiar with the
installation process.

3. General Considerations for Installation
• Ensure the roof area or other installation site is capable of handling the desired
system size.
• If roof mounted, verify that the roof is capable of handling additional weight of PV
system.
• Install equipment according to manufacturers specifications, using installation
requirements and procedures from the manufacturers’ specifications.
• Observe specifications for external mounting of modules, combiner boxes and DC
cabling (IP protection, weather resistance etc.).
• Pay particular attention to DC installation of PV array.
• Properly ground the system parts to reduce the threat of shock hazards and induced
surges.
• Check for proper PV system operation by following the checkout procedures on the
PV System Installation Checklist.
• Ensure the design meets local utility interconnection requirements.
• Have final inspections completed by the concerned authority and the utility if
required.

4. Installation of Array Support Structure
• PV array support structure is pre-fabricated and surface treated ready to be
installed on the roof or on ground.
• The rooftop support structure is typically embedded into concrete blocks
cast on the roof.
• A number of PV modules are installed on one support structure called PV
panel. The PV modules in one panel are usually connected in a series
string.
• The PV panel is designed for small (1 cm) gaps between modules when
assembled. This arrangement results in higher wind resistance.
• Two PV panels are installed in a row with sufficient space (0.5 – 1.0 m)
between them for maintenance access.
• Two rows of PV panels are mounted with space adequate to avoid shadow
of one row of panels onto the other.

5. • As a rule of thumb, minimum width between two rows is equal
to the height of the panel structure.
• The support structure is oriented to south with a tilt angle
equal to the latitude of the plant location.
• This arrangement results in maximum annual yield.
• We should leave vacant space around parapet wall when
installing array on rooftop.
• The minimum width of the space to be left vacant should be
equal to the height of the parapet wall.

6. General Notes on DC Installation
• The modules are electrically live when installed and cannot be switched off.
• Therefore, modules without shrouded connectors should be covered with
lightproof material during installation.
• The level of module DC current output is proportional to the amount of solar
radiation, however, the nominal output voltage is attained even when radiation is
low.
• The module/array DC current can cause permanent arc if there is an insulation fault.
• All installations above 50 V DC must be ground fault and short circuit proof.
• The short circuit current of PV module/array is around 20% above nominal current.
• DC fuses/circuit breakers should take this into account.
• Ensure correct polarity when connecting PV modules, strings, arrays, combiner
boxes, DC circuit breakers and DC cables.
• If the polarity is reversed, bypass diodes and inverter’s input stage may be
damaged.

7. Installation of Modules
• Monitor module Voc and Isc and check that they are within specified limits
before installing the module.
• Modules with shrouded (touchproof) MC4 connectors are preferred as they
are electrically safe to install and convenient to isolate from the string.
• The installation of modules should be done in dry weather conditions using
dry tools to avoid risk of electrical shock.
• Use mounting system (clamp/fastener, mounting points) recommended by
manufacturer.
• Use predrilled mounting holes. Additional holes drilled in the frame may
void the warranty.

8. • Modules should not be stepped on during installation. No
heavy or sharp edge items should be placed on them to avoid
damage to the glass cover.
• Ensure accessibility of roof structure after modules are
installed for maintenance.
• Preassembled and prewired modules may be used for roof
areas difficult to access.
• The corners and edges of frameless modules (typically thin
film types) are particularly sensitive and are subject to high
level of breakage risk during transport and installation.
• Extreme care in handling these modules during installation is
required.
• When installing multiple modules on a support structure, lay
out all modules before fastening to ensure they are aligned
leaving gaps between them.

9. Interconnection of Modules, Strings and Combiner Boxes
• To avoid losses due to mismatching of modules, ensure that modules with
similar MPP currents are interconnected in a series string.
• Interconnect module connectors under open circuit. Do not short circuit
module outputs to avoid arcing and damage to connectors.
• For modules without connectors, use suitable clamp terminals, strain relief
and waterproof cable feed-through when connecting cables into the module
junction box. Ensure that the junction box cover is sealed and watertight.
• Do not disconnect module connectors under load. Switch off the inverter
and trip the DC circuit breaker to isolate load before disconnecting module
connectors. The module connectors can be disconnected under open circuit
voltage.
• Measure string open circuit voltage before connecting in parallel with other
strings. Ensure that string open circuit voltages are matched within specified
limits.

10. • The measurement of short circuit current and insulation resistance to frame/ ground
are recommended for safe and secure installation.
• The measurement of string I/V characteristics ensures that string MPP
voltages and currents are matched within specified limits.
• The locations of string/array combiner boxes are determined to minimize DC cable
lengths. Ensure ease of access for interconnections and maintenance while installing
the boxes.
• String fuses, blocking diodes and DC surge/lightning protection devices are
installed and wired inside combiner box.
• When connecting DC main cable into the combiner box, ensure that Combiner box
is isolated from PV string/array to avoid high risk of arc as a result of DC power input.
• For systems using string inverters without combiner boxes, isolate the String at a
module cable using DC disconnect switch to avoid risk of DC Arcing when connecting
DC main cable.
• When connecting DC main cable into inverter DC input, ensure that inverter DC
input is isolated using DC circuit breaker.

11. DC and AC Cable Layout and Connection Guidelines
• DC and AC cables should be installed in separate conduits or enclosures and
labelled.
• Careful attention is required to the cable’s permitted bending radius.
• For roof mounted installations, fix cables to the roof supports using suitable
fastenings.
• Cables should be laid in shadow areas where possible and they should not impede
rain water runoff.
• Cables, fasteners and cable ties should be weather resistant.
• Cables should stay away from lightning conductors.
• Avoid sharp edges and mechanical damage to cable insulation.
• Use proper recommended tools and follow cable termination guidelines.
• Cable termination should be either crimped or soldered to suit terminal design.
Avoid combination of crimping and soldering the same joint.
• Crimped terminals are preferred over soldered joints.
• All terminations should use proper terminals, no cable to cable joints
Should be used.
• Ensure DC and AC circuits are isolated when cables are interconnected.

12. Grounding Considerations
• Equipment and system grounding is required to provide earth as common
reference point for various voltages, to limit voltages due to lightning, line
surges or accidental contact with high voltage lines and to provide current path
for operation of over-current protection devices.
• The grounding consists of grounding electrode, grounded conductor and
grounding conductor. Grounded conductor is grounded at one point via
grounding electrode and grounding conductors connect all equipment
enclosures to grounding electrode via grounded conductor.
• Equipment grounding provides protection from shock caused by ground
Fault and is mandatory in all PV systems.
The equipment chassis is connected to grounding electrode via grounding
conductor. PV array, combiner box, inverter, DC and AC distribution box
require grounding. The grounding conductor must not be fused or switched.

13. • Array support structure should have equipotential bonding and grounding
arrangements for safe conduction of capacitive discharge currents to ground.
• All grid-connected PV systems have DC voltage (400 – 800 V) well over 50 V
and require system ground. DC system grounding is done by connecting negative
conductor to ground at one single point. The single point ground is located near the PV
array for better system protection from voltage surges.
• AC system can use the same grounding electrode. If two separate electrodes are
used for DC and AC systems, they need to be bonded together.
• Jumpers may be installed for equipment and system grounding conductors to
maintain ground continuity in the event, one of the equipment is removed from the
system.
• Ground fault detector and interrupter (GFDI) is used to isolate grounded negative
conductor from ground under ground fault condition. GFDI also isolates ungrounded
positive conductor. Most Grid-tied inverters provide built-in ground fault protection. If
not, external ground fault protection is required.

14. Installation of DC and AC Power Distribution Boxes
• The DC and AC distribution boxes are located near the inverter.
• The array output wires from combiner box are routed to DC distribution box along
the shortest route.
• Ensure that the installation of wiring to the DC or AC isolator switch and surge
protection devices is ground fault and short circuit proof.
• For DC voltages > 50 V, the two pole DC isolator switch must have at least 5 mm
gap between the contacts in order to enable safe and reliable isolation.
• Ensure that the type plate of the DC isolator clearly states the DC voltage level of
operation.
• The inverter input should be isolated when connecting to DC distribution Box and
inverter output should be isolated when connecting to AC distribution box.
• The AC distribution box may be combined with Load distribution box. If separate,
it should be located near load distribution box.
• The DC PV energy meter is installed inside DC distribution box and the AC PV
energy meter is installed inside AC distribution box.
• The DC and AC distribution box enclosures should be connected to ground

15. Installation of Inverter
• The inverters should be installed in a location where faultless operation is
guaranteed. Factors to consider are ambient temperature, humidity, ventilation,
heat dissipation capability, noise emission as well as possible ingress of dust,
water and pests.
• The inverters must be easily accessible with sufficient space around for
maintenance and servicing.
• The inverter mounted on ground or wall should be at a height convenient
for reading its display.
• The inverter for large power application is mounted on ground and is
Securely bolted to concrete floor.
• The inverter for small power application is mounted on wall and is securely
bolted to wall.

16. • Ensure adequate open space is provided around ventilation
panels for heat dissipation.
• The string inverter installed outdoors is IP65 rated. The
string/central inverter installed in semi-controlled environment
is IP54 rated.
• The central inverter installed in controlled environment is
typically IP21 rated.