Solar PV systems

**ians** · 05-Dec-21, 01:18 PM

This is a topic I will be exploring in great detail over the next few weeks as we prepare to start 1 of 5 installs from the beginning of next year.

Hence all the sudden interest in alterative supplies.

Had a few site visits already as we prepare to design and fit multiple solar/inverter battery systems.

First question to the customer ... do you have spare roof tiles.

**ians** · 05-Dec-21, 01:40 PM

I need to explore the earthing requirements for the panels and supports.

Do I "have" to install lightning protection for the system ... I know it would be advisable ... but if you look at the SANS 10142 7.12 ... there is only mention of "can" be and not "must" be SPD's

7.12.3.1 Neutral bar earthing
7.12.3.1.1 Protection in accordance with the requirements of 6.7 shall be
provided for the electrical installation in such a manner as to ensure correct
operation of the protection devices, irrespective of the source of supply or
combination of sources of supply. Operation of the protection devices shall
not rely upon the connection to the earthed point of the main supply when the
generator is operated as a switched alternative to the main supply.
Where there is no existing earth electrode installed in the electrical installation,
a suitable earth electrode may be installed in accordance with SANS 10199.
When installed, the electrode shall be bonded to the consumer's earth terminal
and to the earthing point on the alternate supply by a conductor of at least half
the cross-section of that of the phase conductor, but not less than 6 mm2
copper, or equivalent. This also applies to a single-phase supply
(see also 5.2.3.1).
NOTE 1 In a TN system earthing of electricity supply, an earth electrode is normally
not required in an electrical installation.
NOTE 2 Protection of photovoltaics can be by means of or surge protective device
(SPD).

**ians** · 05-Dec-21, 04:25 PM

Selecting over current protection for for a system ... this has been discussed on more than one occasion.

Over current protection for the conductors and the device ... we generally only consider the breaker size per the conductor.

7.12.5 Protection against overcurrent
7.12.5.1 Overcurrent protection
7.12.5.1.1 Overcurrent protection and isolation shall be located as near as
possible to the output terminals of each alternative supply unit, except where
the cable connecting the unit to the distribution board is mechanically
protected and is regarded to be within the fault-free zone of the distribution
board where protection is installed. The circuit-breaker magnetic characteristic
shall have a low threshold value in view of the high impedance in the case of
a generator or of the current-limiting characteristics in the case of a static
inverter UPS. Downstream coordination shall take this into account. To be
consistent with the rest of this part of SANS 10142, overcurrent protection is
required for the protection of the conductors, but might also provide protection
to the alternative supply unit.

**ians** · 05-Dec-21, 04:34 PM

Would you need a piece of test equipment to measure the harmonics and record the results ... before issuing the COC ... am I correct in saying this is the case were you have a hybrid or grid tied installation ... the panels would be producing power and operating in parallel with the mains?

7.12.5.1.2 Where an alternate supply system is intended to operate in parallel
with the main supply or where two or more alternate supply system may
operate in parallel, circulating harmonic currents shall be limited so that the
thermal rating of conductors is not exceeded. The effects of circulating
harmonic currents can be limited by
a) the selection of alternate supply system with compensated windings,
b) the provision of suitable impedance in the connection to alternate supply
system generator star position,
c) the provision of switches which interrupt the circulatory circuit but are
interlocked so that at all times protection is not impaired,
d) the provision of filtering equipment, and
e) other suitable means.

**ians** · 05-Dec-21, 04:39 PM

Lets say you install a hybrid inverter ... you have an earth leakage feeding the inverter ... but when the inverter is pushing power from the inverter back into the non essential side ... are the protective devices we buy off the shelf decide to operate as line and load and the opposite direction ... or do you have to use specific breakers designed for this type of application?

**ians** · 05-Dec-21, 05:10 PM

I take it all the inspectors signing over installations are taking note of this reg ?

7.12.7.3 The rated voltage of each circuit shall be clearly indicated at all ends
of the circuit.

In the case of combined circuits, every circuit shall be easily identifiable.
Where single core conductors are used, such conductors for each circuit shall
be tied together at intervals to ensure identification, unless another suitable
arrangement is employed

**ians** · 05-Dec-21, 05:13 PM

How would you define a hybrid system ... running in parallel with the mains ?

The little knowledge I have about this type of installation ... the direction of flow is determined by the frequency ?

**ians** · 05-Dec-21, 05:17 PM

Time to a call it a day ... I thought I would spend the weekend understanding 7.12 ... instead I have questions than answers

**Justloadit** · 05-Dec-21, 06:24 PM

Originally Posted by ians

How would you define a hybrid system ... running in parallel with the mains ?

The little knowledge I have about this type of installation ... the direction of flow is determined by the frequency ?

Not frequency.
The Hybrid electronics, use the mains as a reference to generate the AC. What the electronics does is that it measures the incoming mains voltage, and then it ups its own voltage by a point or two above the incoming voltage, this in turn means that the inverter then supplies the load. When the load exceeds the inverter capacity, it scales back and allows the mains to power the load.

Its like having two batteries in parallel, the one with more capacity supplies the higher current.

**ians** · 05-Dec-21, 08:04 PM

Just finished reading another 70 page draft ... I know what I will be doing for the whole of December ... man I have a lot to learn.

Also going to be looking at another set of hands ... I tried something different on Thursday ... I used a 3 man team instead of just 2 of us ... I focused on the design setup and connecting ... the other 2 pulled cables and mounted the equipment 6 hours and we managed to install 7 socket outlets ... conduits along the wall and cabling along the factory steel frame work ... its the first time in many years that the labour bill was less than the material cost (only 60 % of the material cost) ... I still havent been able to beat installing 4000 m of cabling in 4 days (ok I had 6 staff member working with me) we were allocated 2 weeks to complete the able installation ... I got every job after that.

My only concern for starting with solar installs in Jan/Feb ... man it will be hot on the roof.