PRD/SZNS 075: 202 3  
  
ICS               Edition 1  
   
    
    
 
 
 
 
 
 
 
   
  
 ESWATINI NATIONAL STANDARD  
   
    
    
   
Mini -Grid and Off -Grid Systems   
    
   
  
      
    
    
    
 
 
    
   
  
Published by: Eswatini Standards Authority  
Marble Construction Building, Plot 247 11th Street King Mswati III Avenue West  
P. O. Box 1399, Matsapha, Kingdom of Eswatini   
Telephone: +268 2518 4633, Facsimile: +268 2518 4526   
Website: www.swasa.co.sz   
E-mail: info@swasa.co.sz    
©Eswatini Standards Authority 202 3  
 
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© Eswatini Standards Authority 202 3   
All rights reserved   
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Table of changes  
Clause Changed   Date  Change   
      
 
NATIONAL FOREWORD  
This Eswatini National Final draft Standard was prepared by Technical Committee SWASA/TC 36 Electrical 
Energy & Wiring  in accordance with procedures of the Eswatini Standards Authority, in compliance with 
Annex 3 of the WTO/TBT Agreement.  
  
  
  
  
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All rights reserved  Table of Contents  
0 Introduction  ................................ ................................ ................................ ............................  7 
1 Scope  ................................ ................................ ................................ ................................ ...... 8 
2 Normative References  ................................ ................................ ................................ ............  8 
3 Terms and Definitions  ................................ ................................ ................................ ............  8 
3.1 Definitions  ................................ ................................ ................................ ........................  8 
3.2 Abbreviati ons ................................ ................................ ................................ ...................  9 
4 General Requirements  ................................ ................................ ................................ ..........  10 
4.1 Network Information  ................................ ................................ ................................ ...... 10 
4.2 Nominal voltage and operating voltage range ................................ ................................  11 
4.3 Nominal frequency and operating frequency range  ................................ .......................  11 
5 Solar P V Generation System Components  ................................ ................................ ...........  11 
5.1 Photovoltaic (PV) modules  ................................ ................................ ............................  11 
5.2 Photovoltaic (PV) Array ................................ ................................ ................................ . 12 
5.2.1  PV array rack (mounting structure)  ................................ ................................ ........  12 
5.3 Inverters  ................................ ................................ ................................ ..........................  12 
5.3.1  Standards and certifications  ................................ ................................ ....................  12 
5.3.2  Inverter labelling  ................................ ................................ ................................ ..... 13 
5.3.3  Inverter warranty  ................................ ................................ ................................ ..... 13 
5.3.4  Inverter efficiency  ................................ ................................ ................................ ... 13 
5.3.5  Safety Compliance  ................................ ................................ ................................ .. 13 
5.3.6 Labelling  ................................ ................................ ................................ .................  13 
5.3.7  DC Cables  ................................ ................................ ................................ ...............  13 
5.3.8  DC Combiner Box  ................................ ................................ ................................ .. 14 
5.3.9  Cabling and wiring  ................................ ................................ ................................ .. 14 
5.3.10  AC Cables  ................................ ................................ ................................ ...............  14 
5.3.11  Ducting and Conduits  ................................ ................................ .............................  14 
5.3.12  Cable Connectors  ................................ ................................ ................................ .... 14 
5.3.13  Cable sizing  ................................ ................................ ................................ .............  14 
5.3.14  Cable Colouring  ................................ ................................ ................................ ...... 14 
5.4 PV charge controllers  ................................ ................................ ................................ ..... 15 
5.5 Batteries  ................................ ................................ ................................ ..........................  15 
5.5.1  Cycle li fe and warranty  ................................ ................................ ...........................  15 
5.5.2  Battery labelling  ................................ ................................ ................................ ...... 16 
5.5.3  Overcurrent protection and disconnects ................................ ................................ .. 16 
5.5.4  Battery installations  ................................ ................................ ................................  16 
6 Hydropower  ................................ ................................ ................................ ..........................  17 
6.1 Powerhouse  ................................ ................................ ................................ ....................  17 
6.2 Civil work s – concrete and steel  ................................ ................................ ....................  18 
6.3 Weir & intake  ................................ ................................ ................................ .................  18 
6.4 Channel ................................ ................................ ................................ ...........................  19 
6.5 Forebay  ................................ ................................ ................................ ...........................  19 
6.6 Penstock and  supports  ................................ ................................ ................................ .... 20 PRD/ SZNS  075: 202 3 
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All rights reserved  7 Micro -hydropower generators and controls  ................................ ................................ .........  21 
7.1 Turbine  ................................ ................................ ................................ ...........................  21 
7.2 Generator  ................................ ................................ ................................ ........................  21 
8 Electricity supply Powerhouse  ................................ ................................ .............................  21 
8.1 Protective arrangements  ................................ ................................ ................................ . 21 
8.2 On-site fuel storage  ................................ ................................ ................................ ........  22 
9 PV Array, generator, battery, and powerhouse wiring  ................................ .........................  22 
9.1 General  ................................ ................................ ................................ ...........................  22 
9.2 Wiring losse s ................................ ................................ ................................ ..................  22 
9.3 Wiring standards  ................................ ................................ ................................ ............  22 
9.4 Wiring installation  ................................ ................................ ................................ ..........  22 
9.5 Earthing  ................................ ................................ ................................ ..........................  23 
9.5.1  Equipment earthing, including PV array frame  ................................ ......................  23 
9.5.2  AC conductor earthing  ................................ ................................ ............................  23 
9.5.3  DC conductor earthing  ................................ ................................ ............................  23 
10 Other Generation Technologies  ................................ ................................ ............................  24 
11 Distribution Line  ................................ ................................ ................................ ..................  24 
12 Metering  ................................ ................................ ................................ ...............................  24 
Bibliography  ................................ ................................ ................................ ................................ . 25 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  PRD/ SZNS  075: 202 3 
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All rights reserved  0 Introduction   
This document outlines the minimum technical specifications that must be followed in 
development of new mini -grid plants in Eswatini. These technical specifications are drafted with 
the purpose of ensuring safety and reliability of mini grids.  
   
   
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 
 
 
 
 
 
  
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All rights reserved  Eswatini Mini -Grid and Off -Grid Systems Standard  
 
1 Scope    
This standard specif ies the technical requirements for mini -grid and off -grid system design, 
construction, installation, operation and maintenance. Th is standard  is meant to ensure safe, reliable 
and quality supply of electricity to consumers. Th is standard also cover s but not l imited to  stand -
alone systems such as solar home systems , micro  and pico -systems.  
2 Normative References   
The following referenced documents are indispensable for the application of this document.  
3 Terms and Definitions    
For the purpose of this standard the following definitions and abbreviations apply.   
3.1 Definitions   
Battery  
a source of electric power consisting of one or more electrochemical cells with external connections 
for powering electrical device. Battery is syn onymous with batteries.  
Depth of Discharge  
indicates the percentage of the battery that has been discharged relative to the overall capacity of the 
battery.  
Distribution Network  
any connection of cables, service lines and overhead lines,  electrical apparatus/equipment and having 
design voltage equivalent to distribution voltage  used to transport electric power from an undertaking 
to a Consumer.  
Distributor  
a person distributing electricity . 
Isolated Mini -Grid   
a Mini -Grid which is not connected to any Distribution.  
Isolated Mini -Grid Operator  
a person who is appointed by the system controller to be responsible for the isolated mini -grid. 
Mini -grid system  
any electricity supply system with its own power generation  capacity, supplying electricity to more 
than one cconsumer  through its own distribution  network , with defined geographical and electrical PRD/ SZNS  075: 202 3 
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All rights reserved  boundaries, metering system and which  can operate in isolation from or be connected to a 
ddistributor’s  network or main grid.  
Pico-systems  
a small PV -system with a power output of 1 to 10W, mainly used for lighting and thus able to replace 
unhealthy and inefficient sources such as kerosene lamps and candles.  
Stand -alone system  
A stand -alone power system, al so known as remote area power supply, is an off -the-grid electricity 
system for locations that are not fitted with an electricity distribution system which may include one 
or more methods of electricity generation.  
Solar home system  
a small -scale, autonomous electricity supply for households that are off -grid or have unreliable access 
to energy . 
Off- Grid Project  
Electricity network not connected to the main national electricity  supply grid network.  
3.2 Abbreviations   
AC  Alternating Current  
DC  Direct Current  
DOD  Depth of Discharge  
IEC    International Electro -technical Commission  
IGC  Induction Generator Controller   
IP  Ingress Protection  
kV  Kilovolt  
LV  Low Voltage   
MCB  Miniature Circuit Breaker  
MPPT  Maximum Power Point Tracking  
MV  Medium Voltage   
O&M  Operation and Maintenance  
PV Photovoltaic  
PWM  Pulse Width Modulated  
STC Standard Test Conditions (25 degrees C and 1000 watts per m2) 
V Volt PRD/ SZNS  075: 202 3 
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All rights reserved  W Watt  
Wh Watt hour  
Wp Watt peak (unit of nominal power of photovoltaic devices)  
4 General Requirements   
4.1 Network Information  
The following information shall be readily available from the Isolated Mini -Grid Operator, and 
provided on -site at all times:  
a) A single -line diagram of the generating plant and the distribution network, showing:  
i) all gen eration components, conversion components, storage components, 
monitoring/communication components and isolation and protective devices with Connection 
Points clearly marked;  
ii) As-built distribution network with pole positions, pole spans, single or three p hase network (or 
DC network), conductor size, isolation points/devices, earthing points, major customer locations 
and protection measures clearly indicated.  
b) A mini -grid system inventory showing quantities, sizes, manufacturers and technical 
specifications  on:  
i) Civil works (mounting structures, power house, office, fence etc.)  
ii) Generation system (solar PV panels, hydro generator, inverters, batteries, combination boxes, 
safety and protection devices, monitoring equipment etc.)  
iii) Distribution system (pole schedule, conductors, switches, isolators, stays, customer connection 
and protection equipment etc.)  
iv) Metering and vending system (meter boxes, meters, vending system hardware and software etc.)  
c) A customer database showing:  
i) Name  and address of each customer, including phone number and date of connection  
ii) Type of customer (household, business, public facility, industrial etc.)  
iii) Connection type (single phase, 3 phase, DC)  
iv) Pole number where customer is connected from  
v) Meter number and allocated power (if applicable)  PRD/ SZNS  075: 202 3 
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All rights reserved  4.2 Nominal voltage and operating voltage range  
a) For AC mini grids, the nominal voltage at customer service drops shall be 400 V (line to line) or 
230 V (line to neutral). The operating voltage shall not vary b eyond ± 10% of the nominal voltage.  
b) For DC mini grids, the nominal voltage shall be 48 volts or less.  
c) If the Mini -Grid requires medium voltage distribution, it will use a nominal voltage of 1 1 kV, and 
the allowed operational voltage variation is ± 10%. T he nominal generating voltage, however, 
may be different to the nominal voltages of the distribution network.  
4.3 Nominal frequency and operating frequency range  
For AC mini grids, the nominal operating frequency of the mini grid shall be 50 Hz. The allowed 
operating range shall be within + 5% (5 2.5 Hz) and -5% (4 7.5 Hz), beyond which the protection 
relays at generation should operate to shut down the Mini -Grid, after a time delay of 500 ms from 
the time the frequency crosses the allowed boundaries .  
5 Solar P V Generation System Components  
The mini and off -grid solar PV systems shall conform to the SZNS 07 6 Solar PV Systems – 
Design, Equipment and Installation Standard . 
5.1 Photovoltaic (PV) modules  
a) Solar modules shall conform to the following International Electro -Technical Commission (IEC) 
standards.   
i) IEC 61215 Crystalline silicon terrestrial photovoltaic (PV) modules – Design qualification and 
type approval.   
ii) IEC 61730 Photovoltaic (PV) modules s afety qualification – Requirements for construction and 
requirement for testing.    
iii) PV modules must also be compliant with IEC 61730 and IEC 61215 and  IEC 61727 standards .  
b) All PV modules should have following product warranty levels.   
i) Manufacturing warra nty (material and workmanship): must have at least a ten -year warranty on 
physical manufacture of module itself, i.e. the frame, encapsulant, glass, module junction box etc. 
The module will be replaced by manufacturer if it has defects or produces less pow er than it 
should.  
ii) Panel output Wp capacity ≥ 90% of design nominal power after 10 years and ≥ 80% of design 
nominal power after 20 years.   PRD/ SZNS  075: 202 3 
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All rights reserved  c) Bypass diodes shall be installed in each module to prevent hot -spots in modules, which occur 
often because of partial shading of modules.   
d) Junction box should be thermos -plastic, IP65 and UV resistant  
e) The label of the PV module shall have the following de tails. Name of the manufacturer, model 
number, serial number, short circuit current (I sc), Open circuit voltage (V oc), Current at maximum 
power (I mp), Voltage at maximum power (V mp), and power rating of panel at standard test 
condition (STC).  
5.2 Photovoltaic (PV) Array  
5.2.1 PV array rack (mounting structure)  
a) The mounting structure used for the solar panels shall be made of corrosion resistant material such 
as aluminium  alloy or hot dip galvanized steels. If hot dip galvanized, thickness of galvanizati on 
shall exceed 80 microns.   
b) The array rack shall be constructed as earth mounted, top -of-pole, or roof -mounted type.  
c) Minimum thickness of the structural material which is used for mounting structure should be 2mm.   
d) Bolts, nuts, fasteners, panel mountin g clamps including joining the sections of structure should be 
with galvanized or stainless -steel bolts (Stainless steel SS 304) or by welding. Bolts shall be 
secured with locking washers or locknuts.  
e) In case of a welding structure, galvanization should b e done after the fabrication work.  
f) Any contact between unlike materials shall be avoided by using insulation between any alumin ium 
and galvanized sections.  
5.3 Inverters  
5.3.1 Standards and certifications  
Inverters, whether PV inverters or battery inverters, used for mini -grids shall be supplied with 
complete data sheets and comply with the following standards:  
a) IEC TS 62257 -9-7 Recommendations for renewable energy and hybrid systems for rural 
electrificati on-Part -9-7 Recommendation on selection of inverters  
b) IEC TS 62257 -7-4 Recommendations for renewable energy and hybrid systems for rural 
electrification -Part 7 -4 Generators -Integration of solar with other forms of power generation 
within hybrid systems  
c) IEC TS 62257 -2 Recommendations for renewable energy and hybrid systems for rural 
electrification -Part -2 From requirements to a range of electrification systems  PRD/ SZNS  075: 202 3 
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All rights reserved  d) IEC TS 62257 -7-1 Recommendations for small renewable energy and hybrid systems for rural 
electrifi cation -Part 7 -4 Generators -Photovoltaic generators  
5.3.2 Inverter labelling   
Each inverter device must be labelled according to EN 50524 (Data sheet and name plate for 
photovoltaic inverte rs, with the minimum  following information:  
a) Manufacturer name and model   
b) Serial number  
c) Input and output voltage and rated power  
d) IP 65 for outdoor mounting and IP 54 for indoor mounting    
5.3.3 Inverter warranty  
Inverters must be warranted against manufacturing defects for at least five years (standard 
warranty for quality inverters).  
5.3.4 Inverter efficiency  
Maximum Inverter efficiency ≥ 98% and weighted inverter efficiency ≥ 95% .  The efficiency of 
battery inverter s (if used) shall be equal to or greater than 90% over 75% of the power range.     
5.3.5 Safety Compliance  
1. IEC 62109 -1 (Safety of Power Converters for Use in Photovoltaic Power Systems – Part 1: 
General Requirements) .  
2. IEC 62109 -2 (Safety of power converters for use in photovoltaic power systems - Part 2: Particular 
requirements for inverters  
5.3.6 Labelling  
All cables should be label led refer ring to the Inverter Number and String Number i.e . “I3-S4”, 
means the cable connects the fourth string in the third inverter.  
5.3.7  DC Cables  
XLPE or XLPO insulated and sheathed UV stabilised single core flexible copper cables shall be 
sued. The power outdoor cabling shall be made of copper conductors with double sheath type 
HO7RNF inside XLPE or PC pipes and inside cable tray, all comp lete with mounting and fixing 
accessories, junction and connection boxes as well as nay necessary accessories.  PRD/ SZNS  075: 202 3 
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All rights reserved  5.3.8  DC Combiner Box  
A DC Combiner Box shall be used to combine the DC cables of the solar module arrays with DC 
fuse protection for the outgoing DC cable(s) to the DC Distribution Box  
5.3.9  Cabling and wiring  
All cables shall be supplied conforming to IEC 60227 & IEC 60502, Voltage rating: 1,000V DC 
considering the following specs:  
5.3.10   AC Cables  
For the AC cabling, PVC or XLPE insulated and PVC sheathed single or multi -core flexible copper 
cables shall be used. Outdoor AC cables shall have a UV -stabilized outer sheath.  
5.3.11   Ducting and Conduits  
The DC cables from the solar PV module array shall run through a UV -stabilized PVC conduit 
pipe of adequate diameter  with a minimum wall thickness of 1.5mm. Cables and conduits that 
have to pass through walls or ceilings shall be taken through a PVC pipe sleeve.  
5.3.12  Cable Connectors  
Cables and wires used for the interconnection of solar PV modules shall be provided with sol ar 
PV connectors (MC4) and couplers.  
5.3.13  Cable sizing  
All cables and conduit pipes shall be clamped to the rooftop, walls and ceilings with 14hermos -
plastic clamps at intervals not exceeding 50 cm. The minimum DC cable size shall be 4.0 mm2 
copper. The minimum AC cable size shall be 4.0 mm2 copper. In three phase systems, the size of 
the neutral wire size shall be equal to the size of the phase wires. PV wiring and cabling shall be 
rated at 125% of the rated operating DC/AC current of PV array at 25oC cell tempe rature and 1000 
W/m2 solar irradiance.  
5.3.14  Cable Colouring  
The following colour coding  shall be used for cable wires: DC positive: red (the outer PVC sheath 
can be black with a red line marking) − DC negative: black − AC single phase: Phase: red; neutral: 
black − AC three phase: Phases: red, yellow /white , blue; neutral: black − Earth wires: green & 
yellow . PRD/ SZNS  075: 202 3 
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All rights reserved  5.4 PV charge controllers  
Charge controllers shall be certified according to IEC 62509 (Battery charge controllers for 
photovoltaic systems – performance and fu nctioning)  and IEC 62903 - Design qualification of 
power conversion equipment 9PCE) suitable for long term operation in terrestrial photovoltaic 
(PV) systems . 
PV charge controllers, if present, shall have the following characteristics:  
a) Maximum Power Point Tracking (MPPT) or Pulse Width Modulated (PWM)  
b) PV charging efficiency at least 90% based on IEC 61683: Photovoltaic System -Power  
Conditioners - Procedure for Measuring Efficiency  
c) Rated current at 50o C must be at minimum 120% of peak array current (Isc)  
d) Protected from dust ingress (IP55 or higher).   
e) Controllers to be certified to meet at least one of the following standards:  
i) CE or UL 1741 Marking  
ii) IEC 62509  
iii)  IEC 62093  
5.5 Batteries  
5.5.1 Cycle life and warranty  
Batteries shall be in compliance with:  
i.  IEC 61427 -1 (Secondary cells and batteries for renewable energy storage -General 
requirements and methods of test Part 1: Photovoltaic off -grid application.  
ii.  IEEE Std 937 Recommended Practice for Installation and Maintenance of Lead -Acid Batteries 
for Phot ovoltaic Systems . 
iii.  IEEE Std 1013 Recommended Practice for Sizing of Lead -Acid Batteries for Stand -Alone PV 
Systems . 
iv.  IEEE Std 1361 IEE Guide for Selection, Charging, Testing and Evaluation of Lead -Acid 
Batteries for Stand -Alone PV Systems . 
All batteries to  be warranted to at least 2 years under the operational conditions on site, to 80% of 
original rated capacity.  
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All rights reserved  5.5.2 Battery labelling  
a) Each battery/cell shall be engraved with the date of manufacture.  
b) For each battery type, the battery must be label led indicating at minimum: Manufacturer, Model 
Number, operating temperature, Voltage and Capacity.  
5.5.3 Overcurrent protection and disconnects  
a) Positive cables between batteries and inverters shall be protected with DC -rated overcurrent 
protection and disco nnect (either circuit breaker or fused disconnect) of appropriate rating to protect 
cables in the event of a short circuit.  
5.5.4 Battery installations   
a) Space shall be provided around batteries to allow for safe maintenance, testing, battery 
replacement, and inspection.  Space shall also be provided above the cells to allow for operation 
taking measurements, adding water (if cells are flooded type), and fo r lifting equipment when 
required.  
b) Storage batteries shall be located in an area accessible only to qualified persons or within a 
protective enclosure such as a fence, battery room, case, or cage that limits the chances of contact 
with energized parts.   
c) To limit hydrogen accumulation and explosion risk in flooded lead -acid batteries, the battery area 
shall be ventilated either by a fan or by a natural ventilation system.   
d) Racks that support battery cells shall be firmly anchored, preferably to the floor.  Racks made of 
metal shall be earthed.   
e) The floor material in battery areas shall be of a material that resists corrosion from electrolyte. 
Provision should be made to keep spilled electrolyte from leaking to areas where it can cause 
damage.   
f) Battery are as shall be provided with go ggles or face shield, acid -resistant gloves, and protective 
aprons.  
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All rights reserved  6 Hydropower    
6.1 Powerhouse  
a) The floor area of the powerhouse should be sufficient to safely place the equipment and carry out 
routine maintenance work conveniently. Adequate spacing and easy access to the electrical and 
electromechanical equipment from all sides should be maintained for ease of operation and 
maintenance.  
b)  The powerhouse natural ventilation area shall be equivalent to at least 10% of the powerhouse 
floor area to ensure adequate passive ventilation in the absence or failure of automatic temperature 
control equipment.   
c) The minimum height between floor and ceiling should be 3 meters. Roofing material should be 
made of fire -resistant materials such as tile or corrugated sheets. In case of corrugated sheets, the 
minimum thickness should be 0.47mm. The roof should be watert ight and should extend at least 
1 meter over walls to prevent water from  entering through ventilation  portals. The power house 
door shall be designed with adequate spacing for easy installation and removal of equipment. For 
safety reasons,  an additional em ergency door equipped with mechanical mechanism (or Panic 
door) which allows the door to be opened from inside without the use of a lock or key.  The door s 
should be outward -opening (i.e. able to open from the inside). All metal structural elements shall 
be connected to an earth point separate from the electrical circuit main earth.  
d) An appropriate lifting mechanism such as a gantry crane should be provided for the convenience 
of operation and maintenance in case the system components are unwieldy or otherwis e difficult 
to access safely.   
e) Ablution facilities should accompany the powerhouse design or any other requirements in OHS 
Act, 2001.   
f) The Powerhouse must be painted with at least two top coats of durable washable paint both inside 
and outside for all wa lls.  
g) The name and capacity of the plant must be displayed clearly on the front of the building.  
h) Electrical Danger warning signs must be installed at all access points to the yard and building.  
i) Fire extinguishers and all required safety equipment must be  installed and maintained in the 
building.  
j) Sufficient lighting must be installed to do safe work on any equipment by day or night.  PRD/ SZNS  075: 202 3 
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All rights reserved  k) The powerhouse should be equipped with sufficient emergency lighting in the case of a power 
outage.  
6.2 Civil works – concrete  and steel  
Concrete mixtures in hydropower civil works structures should follow the gradings as described 
below:   
- For base (screed) concretes: 15  MPa    
- For water -bearing structures such as the forebay tank, weir and channel of a hydropower facility: 
25 MPa   
- For foundations and other structures: 20  MPa    
- Tor steel or rebar used for construction should comply with BS 4449 -2005  and bends should 
comply with BS 8666 .  Also comply to SANS 10400 – Concrete mix design for different building 
components such as foundations, flooring, columns etc.   
6.3 Weir & intake  
a) The weir should be located at a river section with short width, with an exposed bedrock or where 
depth to the bedrock is minimum, along with considerable upstream storage (in the case that flows 
are restr icted during the dry season).  
b) Intake should be selected such that minimum debris will enter the system during flooding period.  
c) Intake should be equipped with a trash rack to prevent clogging; a control gate to control the water 
flow to the channel and fl ood barrier wall to make the control gate operations possible during high 
flow periods. Trash rack should have preferably iron rods or flat iron; welded with a gap decided 
based on the turbine supplier’s recommendation; rod orienting upward (vertical) dire ction without 
cross bars, making it easy for the plant personnel to clean efficiently with a rake.  
d) The intake shall be located such that it can be accessed during high flood period.   
e) An unregulated (without a valve to regulate flow) environmental flow re leasing pipe, of which 
diameter and location (height from the top of weir) determined by the Environment  Authority, 
must be placed to release environmental flow to safeguard the downstream ecosystem.  
f) A sluice gate (flush gate), shall be designed based on the maximum silt load of the stream. The 
sluice gate shall be located at the lowest point of the weir with a proper controlling mechanism.  
g) Erosion and deepening of downstream riverbed (due to scouring action) of weir and spillways 
should be considered in design phase and should be protected with suitable mechanism/ structures 
incorporated in weir design.     PRD/ SZNS  075: 202 3 
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All rights reserved  6.4 Channel  
a) Freeboard allowance of 30% should be kept when designing the channel dimensions.  
b) To limit erosion in the channel, maximum channel velocity shall conform to the specifications 
below. In case of silty water, channel velocity should be maintained at the minimum velocity  of 
0.3 m/s to prevent clogging of the channel.    
Table 1: Maximum ch annel velocity of different types of hydro channels   
 
Type of channel  Maximum  
velocity (m/s)  
Concrete channels with no internal plaster   2 
Rubble and masonry channel with smooth plaster   1.8 
Clay channel   1.5 
Earth Channel   0.7 
6.5 Forebay  
The purpose of the forebay is to provide a constant head (water pressure) to the turbine, while a 
settling tank slows the velocity of the water to allow sediment to settle, reducing abrasion on the 
turbine. In micro -hydro and mini -hydropower projects, it i s common to combine forebay and settling 
tank functions in the form of a forebay with a settling tank section.  
a) The Settling Tank section should settle and filter particles above 0.3 mm in diameter.    
b) A manually operated sluice gate (flush gate) and spill way shall be incorporated to the settling 
section to flush the silt collected from time to time.  
c) A second trash rack shall be included in the forebay section with rod spacing at similar proportions 
to the weir intake trash rack.   
d) The penstock penetration  through the forebay shall be deep enough to avoid vortex formation, yet 
be positioned at least 150mm above the forebay tank floor to prevent silt and small stones from 
entering the penstock.  
e) A Vent pipe with a sufficient diameter should be fixed to the penstock or bell mouth section to 
prevent implosion of the penstock due to surge pressure.   
 
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All rights reserved  6.6 Penstock and supports  
a) Penstock should have constant gradient in each section; i.e. straight from o ne anchor to the next.  
b) An air release valve shall be fitted to highest point if air is likely to be trapped due to the layout 
of the penstock.     
c) Penstock material and thickness shall take into account pressure due to normal operation as well 
as any surg e that might occur do to blockage, with a safety factor of at least 2.   
d) Penstocks laid above ground should be supported at every 6m intervals with a slide block or 
support block. In the event of support blocks, minimum of 120 deg of the penstock circumfer ence 
should be firmly in contact to the support block. These supports and slide blocks can be made with 
concrete, rubble and masonry   
e) In all bends, an anchor block made of reinforced concrete and/or should constructed to 
counterbalance the forces occurs d ue to cause by change of momentum of water. Possible penstock 
failing scenarios like toppling, sliding, sinking/lifting forces should be considered when sizing the 
anchor blocks   
f) Underground steel and PVC penstocks should be buried at least 300mm beneath the ground and 
should be on a sand bed. No slide or support blocks apart from anchor blocks at the bends are 
required in underground penstocks.   
g) Thermal expansion and Expansion joints: rubber sheets or tar sheets (graphite asbestos sheet) of 
minimum thick ness of 3mm must be placed between penstock and supports to prevent abrasion 
due to thermal expansion and contraction.    
h) Expansion joints are required in steel penstocks just below anchor blocks and forebay tank to 
minimize the stress created due to therm al expansion and contraction.    
i) A tailrace should be constructed with reinforced concrete and should create a safe passage of water 
back to the stream downstream of the power house. Steps or rock protuberance should incorporate 
to break the water speed an d to minimize erosion.   
 
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All rights reserved  7 Micro -hydropower generators and controls  
7.1 Turbine  
a) Turbine shall be able to operate at runaway speed (loss of load condition) for two hours without 
mechanical failure.  
b) Water flow must be able to be fully stopped by a valve or guide vanes to allow for turbine 
maintenance. The valve shall be slow closing (at least 10 seconds) to prevent a pressure wave in 
the penstock pipe.  
c) Bearings should be capable of continuous operati on and have a warranty period of at least 2 years.  
d) The turbine shall have a sealing mechanism to prevent water from flowing along the shaft and 
entering the generator.  
e) In configurations where the turbine is coupled directly to the generator, a flexible c oupling is 
advised to protect against bearing failure from misalignment.  
7.2 Generator  
a) Generators must have means of controlling voltage and frequency within limits specified in 
sections 4.2 and 4.3 under all conditions from 0% to 100% load.  
b) If the generator type is induction, excitation capacitor banks should have an over -current device 
to stop the generation of excessive voltage and damage to the alternator in the case of turbine 
overspeed  (12) / runaway speed. Various generator protection schemes may be applicable (over  
or under frequency  (810/U) , over voltage (59) , loss of excitation  (40), time/voltage restraint  
overcurrent  (51V) / ground overcurrent (51G), stator earth fault (27TN/59N) ). 
8 Electricity supply Powerhouse   
8.1 Protective arrangements  
a) Spaces in which electric supply conductors or equipment are installed shall be protected from 
entrance of unauthorized persons.  
b) Floors shall have even surfaces and secure footing.  
c) Each room with working electrical equipment shall have means of exit that is kept clear of 
obstructions.  
d) Mechanical parts such as pulleys, belts, or other parts that transmit mechanical power shall have 
guards installed to prevent injury.  PRD/ SZNS  075: 202 3 
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All rights reserved  e) Suddenly moving parts of equipment that operate in such a way that persons in the vicinit y are 
likely to be injured by such movement shall be guarded or isolated.  
8.2 On-site fuel storage  
a) All tanks, pipes, valves and pipe fittings shall be designed and built in accordance with an 
approved standard (for example API STD 650: Welded  steel tank for oil storage ) and shall have a 
safety factor that is adequate for the conditions of service.  
b) The storage facility shall incorporate spillage control such as remote impounding, impounding 
around tanks, bunding or by a combination. In both ty pes of impounding, the impoundment area 
shall be protected by adequately designed systems to prevent the contamination of ground water 
if such a risk exists.  
9 PV Array, generator, battery, and powerhouse wiring  
9.1 General  
a) All outdoor exposed wiring and junction boxes must be protected from UV radiation and terminals 
protected against dust and moisture  and shall comply with IEC 529 – Ingress Protection standard . 
The wiring installation shall be both physically robust against bumping and tugging, and 
elect rically robust.  
b) Outdoor wiring shall have UV resistant insulation or be protected by UV -resistant plastic or metal 
conduit.  
9.2 Wiring losses  
a) PV array to battery circuit(s) shall be sized for maximum 5% voltage drop at rated array current.  
b) Wire shall be de rated for climatic conditions.   
9.3 Wiring standards  
a) Cables may be copper or aluminium . Cables shall comply with IEC 60227: Polyvinyl chloride 
insulated cables of rated voltages up to and including 450/750 V or appropriate standard.  
9.4 Wiring installation  
a) Cables terminations shall be identifiable by colour  and/or lettering/numbering unless there is no 
possibility of confusion (e.g. where cables are pre -fitted with purpose -made polarized plug and 
socket connectors).  
b) All wiring must be neatly installed and s ecured by means of appropriate fasteners at regular 
intervals.   PRD/ SZNS  075: 202 3 
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All rights reserved  c) Wiring lengths shall be sufficiently looped to allow ease of connection and disconnection in the 
case of component replacement or maintenance.  
9.5 Earthing  
9.5.1 Equipment earthing, including PV arra y frame  
a) Exposed metal parts such as metallic module frames, electrical equipment, and conductor 
enclosures must be bonded through an equipment earthing conductor, connected to an earth rod 
sized sufficiently to ensure that the earth loop impedance is less  than 25 Ohms.  
b) Earthing conductors for equipment, raceways, cable, and other metal enclosures for wires shall 
have ampacities adequate for the available fault current over the operating time of the fault -
protective device.  
c) If the circuit has no overcurre nt or fault protection, the earthing conductor ampacity shall be 
determined by the design and operating conditions of the circuit. If the conductor enclosures and 
attachments to equipment enclosures are continuous and adequate, the circuit path formed by t hese 
metallic surfaces may constitute the equipment earthing conductor.  
d) Earthing conductor wires shall be connected via a suitable lug, terminal, or device that is not 
disturbed in the course of normal operation, inspection, or maintenance.  
9.5.2 AC conductor earthing  
a) System electrical earthing shall only occur on the AC side of a system, where the AC neutral 
conductor is connected to the consumer earth conductor, at a single location at the generation 
facility site.  This typically occurs within the system’s main AC di stribution panel. The site of the 
neutral/earth bonding shall be clearly labelled and indicated on the installations’ single line 
diagram.   
b) Alternating current conductors shall be earthed according to REG standards  : Reticulation 
Standards for Electricity Distribution Planning, Construction and Maintenance  available at: 
http://www.reg.rw/fileadmin/user_upload/REG_Reticulation_S tandards.pdf .  
Note: Local appropriate  standard – SZNS SANS 10142 -1:2017 , 
9.5.3 DC conductor earthing  
a) DC systems, or the DC portion of mini grids with AC may remain une arthed.  PRD/ SZNS  075: 202 3 
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All rights reserved  10 Other Generation Technologies  
The electrical design, operation and maintenance of mini -grid and off -grid systems  supplied from 
other  generation  technologies not specified in this standard shall comply with the components 
manufacturer’s guidelines and prevailing applicable national technical, safety, environmental and 
quality standards.  
The standards shall be specified in the specific licenses/per mit granted to the mini -grid or off -grid 
system owner/operator by the Regulator.  
11 Distribution Line  
MV and LV lines that the developer intends to possibly interconnect at a later time with the national 
grid or has no intention to be interconnected to the n ational grid shall be built in accordance with 
Eswatini Electricity Safety Standard . 
12 Metering  
Meters used in mini grids that the developer intends to possibly interconnect at a later time with the 
national grid  or has no intention to be inter -connected wi th the national grid  shall be in compliance 
with the Eswatini Metering Standard  - SZNS NRS 057 . 
List of IEC standards Adopted:  
1. IEC TS 62257 -100:2022 – Technical specification – Renewable energy off -grid systems – part 100: 
Overview of the IEC 62257 series.  
2. IEC 62933 -1:2018 – Electrical energy storage (EES) systems – part 1: Vocabulary.  
3. IEC 62933 -2-1:2017 – Electrical energy storage (EES) systems – part 2 -1: Unit parameters and testing 
methods – general specification.  
4. IEC TS 62933 -4-1:2017 – Electrical energ y storage (EES) systems -part 4 -1: Guidance on environmental 
issues – general specification.  
5. IEC TS 62933 -5-1:2017 – Technical specification – Electrical energy storage (EES) systems – part 5 -1: 
Safety considerations for grid -integrated EES systems – gener al specifications.  
6. IEC 62933 -5-2:2020 – Electrical energy storage (EES) systems -part 5 -2: Safety requirements for grid -
integrated EES systems – Electrochemical -based systems.  
7. IEC TS 62933 -2-2:2022 – Technical specification – Electrical energy storage (EES ) systems – part 2 -2: 
Unit parameters and testing methods – Application and performance testing.  
8. IEC TS 62933 -3-1:2018 – Technical specification – Electrical energy storage (EES) systems – part3 -1: 
Planning and performance assessment of electrical energy s torage systems – general specifications  
9. IEC TS 62933 -3-2:2023 – Technical specification – Electrical energy storage (EES) systems – part 3 -2: 
Planning and performance assessment of electrical energy storage systems – Additional requirements for 
power inten sive and renewable energy sources integration related applications.  
10. IEC TS 62933 -3-3:2022 – Technical specification – Electrical energy storage (EES) systems – part 3 -3: 
Planning and performance assessment of electrical energy storage systems – Additional requirements for 
energy intensive and backup power applications.  PRD/ SZNS  075: 202 3 
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