EDC 3 (523 9) P3  
 
 
 
 
 
 
 
 
 
 
 
 
DRAFT TANZANIA STANDARD  
 
Mini-Grid System s –  
 
Part 7: Underground Power Cables for rated voltages 
0.6kV/1kV (Um 1.2kV)   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
TBS 2017                                                                         First Edition 2017  
 
 
 
  
 
Table of Contents  
 
0. Foreword  ................................ ................................ ................................ ...................  iii 
1. Scope  ................................ ................................ ................................ ...........................  1 
2. Normative References  ................................ ................................ ..........................  1 
3. Quality Control  ................................ ................................ ................................ .........  1 
4. Service Conditions  ................................ ................................ ................................ . 1 
5. Electrical System Parameters  ................................ ................................ ...........  2 
6. Construction  ................................ ................................ ................................ .............  2 
7. Conductor  ................................ ................................ ................................ ..................  2 
8. Insulation  ................................ ................................ ................................ ....................  2 
9. Armour  ................................ ................................ ................................ ........................  3 
10. Outer Sheath  ................................ ................................ ................................ ..........  3 
11. Marking  ................................ ................................ ................................ ....................  4 
11.1  Core Identification  ................................ ................................ ....................  ………… 4 
11.2  Jacket Identification  ................................ ................................ ..............................  4 
12. Tests  ................................ ................................ ................................ ..........................  4 
12.1  General  ................................ ................................ ................................ ........................  4 
12.2  Routine Tests  ................................ ................................ ................................ ...........  5 
12.3  Sample Tests  ................................ ................................ ................................ ............  5 
12.4  Type Tests  ................................ ................................ ................................ .................  5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
  
0. Foreword 
 
This Draft Tanzania Standard is part of an integrated set of specifications and standards 
issued to govern design and construction of mini -grid power systems in Tanzania. This 
standard aims at supporting improved residential, commercial and public services for rural 
communities of Tanzania. The mini -grid energy systems, when properly designed, will 
support affordable and reliable energy supply for remote households, community services, 
commercial and econo mic activities including shops, workshops, micro -industry, fresh 
water pumping, secondary schools, health services, public lighting, places of worship or 
cultural activities, agro -processing activities and other activities.   
 
 
 1. Scope  
 
1.1 This specification covers minimum technical requirements for the design, manufacture, 
testing, supply, and performance of single and multicore  armour ed or un armour ed 
power cables rated 0.6/1 (1.2) kV U 0/U (U m) for use  either direct buried or installed in 
conduit  on 230/400 V, 50 Hertz, three -phase four wire multiple neutral earthed 
underground distribution system for mini-grids. 
 
1.2 The rated voltage of the cable is 600/1000 V , whereas 600 volts is the rated power 
frequency voltage between conductor and earth and 1000 volts is the rated power 
frequency voltage between conductors, for which the cable shall be  designed.  
 
Note 1 This standard shall be read in conjunction with other relevant – Tanzania 
Standards,  applicable standards and specifications to have uniformity, compatibility and 
standardization in the distribution system.  
2. Normative References  
 
The cables shall conform to the latest editions of the IEC standards applicable to their 
construction, including but not limited to those listed below, and to their normative 
references:  
 
IEC 61089 , Round wire concentric lay overhead electrical stranded conductors  
 
IEC 60228 , Conductors of Insulated Cables  
 
IEC 60502 -1, Cables for Rated Voltages of 1kV (U m=1.2kV) and 3kV (Um=3.6kV) 
 
TANESCO – Specification S01 , Supply and Installation of Plant and Equipment  
 
TANESCO  engineering manuals  
3. Quality Control  
 
Cable shall be manufactured in a plant that has  an established and credible past record of 
production of cables of similar ratings and  design and that holds ISO: 9001certification for 
quality management.  
4. Service Conditions  
 
Cable shall be suitable for underground operation under the local service  condi tions in 
Tanzania, which are as follows:  
 
• Altitude above mean sea level (MSL): Up to 3,000 metres  
• Maximum/record yearly high ambient temperature: +40°C  
• High humidity promoting the growth of fungi  
• Extended periods of intense sun exposure  
 
In accordance with  the IEC standards, altitude s not exceeding 1000 m are considered as 
normal service conditions.  Altitudes higher than 1000 m are considered as abnormal 
service conditions, which may require special considerations in the design, manufacture 
or application of the materials or equipment and shall be called to the attention of the 
manufacturer.   
 5. Electrical System Parameters  
 
Mini-grids may be single or three -phase but regardless, s ystem parameters of mini-grids 
for low voltage underground  power distribution network are as follows:  
 
a) Nominal system  voltage (U): 230/400V ( ±10%)  
b) Maximum permissible system  voltage (U m): 253/440V  
c) Minimum permissible system  voltage:   215/374V  
d) System frequency: 50 Hz  
e) Neutral grounding  arrangement: multi - grounded  
f) Power frequency withstand voltage for 5 minutes: 3kV p 
6. Construction  
 
The cables construction shall comply  with the following : 
 
a) Cables may be armour ed or un armour ed at the discretion of the purchaser . 
 
b) The cable shall be designed for a maximum permis sible continuous  conductor  
temperature of 90°C, emergency loading  conductor  temperature of 105°C and 
maximum conductor short circuit withstand temperature of 250°C for 5 seconds.  
 
c) Cables shall be Category C per IEC 60502 -1, that is , the insulation system may be 
exposed to full phase -phase voltage appl ied between any phase and earth.  
 
d) Cables shall be rated for outdoor installation in wet locations either directly buried or 
installed in conduit . 
 
e) Any portion of the cable may be exposed  to full sun while in service, so all insulation, 
sheath, and filler materials shall be certified sun/UV resistant.  Black insulation shall 
be filled with carbon black or other suitable UV protection, and colored materials shall 
be filled with appropriatel y colored UV protectants.   
7. Conductor  
 
The cable conductor shall comply with the following:  
 
a) The conductor shall be uncoated soft drawn annealed copper or aluminum  as may be 
specified  in the tender document .  
 
b) Conductors shall be class 2 as per IEC 60228 . 
 
c) Conductor nominal cross secti on shall be as specified by the purchaser , subject to the 
tolerances allowed by applicable standards.  
 
d) For conductor,  cross sections greater than 10  mm2 conductors shall be stranded . 
 
e) For conductors with cross sections greater  than 16  mm2 conductors shall be 
compacted . 
 
f) Stranded conductors shall have the minimum number of strands as specified in the 
relevant IEC standard.  
8. Insulation  
 
The cables insulation shall comply with the following:   
  
a) LV Power cables insul ation shall be extruded  cross -linked polyethylene (XLPE). 
Insulation shall comply with the appropriate requirements specified in IEC 60502 -1.  
Except for UV resistance agents such as carbon black, the XLPE insulation shall be 
otherwise unfilled.  
 
b) The nominal insulation t hickness shall be as per values specified in IEC60502 -1, with 
respect to voltage rating and cable cross -section.  
 
c) The average insulation thickness shall not be less than the specified nominal value.  
 
d) The minimum thickness of the insulation at any point sha ll not fall below the nomi nal 
value by more than 0.1 mm + 10% of the specified nominal value.  
 
e) XLPE insulation shall be certified sun/UV resistant, including insulation on cores  
whether black or colored . 
 
f) For un armour ed cables, an  inner covering  over the cores  is not required;  however, the 
outer shape of the cable shall remain practically circular  using non -hygroscopic film 
fillers to fill out the circular shape.    
 
g) Multi -core, sector shape cables may have non-hygroscopic  film fillers in order to  form 
a compact circular outer shape . 
 
h) For armour ed cables, an inner covering over the assembled cores shall be extruded 
consisting of a material in accordance with section 7.1 of IEC 60502 -1. 
 
i) Care shall be taken so that no adhesion occurs between cores and either the inner 
layer ( armour ed cables only) or the outer sheath.  
9. Armo ur 
 
Cables specified with armour  shall comply with the following:  
 
a) Armour shall consist of galvanized steel wires applied over the inner covering specified 
in 8.h).  
 
b) The dimensions of the armo ur wires shall conform to the requir ements of IEC 60502 -
1, Part 12.5 . 
10. Outer Sheath  
 
All cables shall be supplied with an outer sheath.  If the cable is armoured, the sheath shall 
be applied over the armour. The cables outer sheath  shall comply with the following:  
 
a) The outer  sheath  material  shall be black PVC, type  ST2 as per  IEC 60502 -1. The  
nominal thickness  of the  outer  sheath  shall be as per  IEC 60502 -1. Mini mum thickness  
at any point  shall not be less than value specified  as per IEC 60502 -1. 
 
b) The PVC o uter sheath  shall be  certified  sun/UV  resistant .  
 
  
 11. Marking  
11.1 Core Identification  
 
a) The XLPE insulation of the four-core cable shall be colored : Brown, Black, Grey 
and Blue . 
 
b) The XLPE insulation of a single core cable shall be colored:  Black. 
 
c) The XLPE insulation of a three -core cable shall be colored Brown and Black  
11.2 Jacket Identification  
 
a) The jacket for all cables shall be marked by raised embossing at intervals not 
exceeding one meter with the following minimum information:  
 
i) The manufacturer ’s name  (in English  or trade mark) 
ii) Voltage  designation  (in English)  
iii) Type  of insulation,  XLPE (in  English)  
iv) Conductor  size and material  (in English)  
v) Year  of manufacture  (in English)  
vi) Cumulative  length  at every  one meter with the highest  length  mark on 
the outer  end of the  cable  
 
b)  All marking/numbering shall be embossed; marking by matri x print shall not be 
acceptable . 
12. Tests  
 
The tests required by this standard include:  
 
12.1 General  
 
a) All cables  shall be tested  in accor dance  with the latest  standards  and as specified 
herein.  Supplier  shall provide all test results for review  and acceptance  by the 
purchaser . 
 
b) The full range  of routine,  sample and type tests  specified  in IEC 60502 -1, clause  14, 
15, 16 , 17 and 18  shall be carried  out as applicable.  
 
c) All XLPE  insulations , whether colored or  black,  and the  PVC sheath material shall 
have pas sed a sun resistance test consisting of exposure to either a carbon arc or a 
Xenon arc lamp  in accordance with ISO 4892 -3 for a peri od of 720 hours while 
retaining 80% of their tensile and elongation properties.    
 
d) Routine and/or special tests shall be carried out in the supplier’s factory. Certified 
test reports shall be supplied for each test unit of cable prior to delivery.  
 
e) Sample tests shall be carried out during the course of manufacture on the frequency 
and with the sample size specified by IEC 60502 -1.  Sample test reports shall be 
available to the purchaser for review prior to delivery of the cables.  
 
f) Type test report/certificate from Tanzani a Bureau of Standards or an independent 
testing laboratory shall be submitted with proposal .  
 12.2 Routine Tests  
 
a) Electrical resistance of conductors, resistance values shall be in accordance with 
IEC 60228.  
 
b) AC voltage test, cable shall be tested per IEC 60502 -1. 
 
12.3 Sample Tests  
 
a) Conductor  examination  shall be in accordance  with IEC 60228.  
 
b) Other sample tests  shall be in accordance with IEC 60502 -1. 
12.4 Type Tests  
 
Complete test (electrical and non -electrical) shall be carried out as per the relevant 
IEC standards.  Type test reports  and certificates of sun resistance, or  certificates of 
qualification shall be provided at the time of tender from Tanzania Bureau of 
Standards or an independent accredited testing laboratory.