Tecnoserve Sells, Installs and does Maintenance on Medium Voltage Equipment

Medium Voltage (MV) is defined as: 1000V< MV ≤ 44kV


Over the past decade or more, it has become evident that the skills and competencies of personnel in the electrical field in the South African coal mining industry, such as artisans, supervisors and engineers, have diminished.

Technoserve is qualified to undertake specialised electrical work: 

- Inspection and maintenance of explosion protected apparatus
- Reading electrical drawings and fault finding
- Testing, phasing and working with Medium Voltage electrical systems
- Power supply from Eskom 
- Primary reticulation; typically 22 kV or 33 kV
- Secondary reticulation; typically 6.6 kV or 11 kV.


Hazards associated with reticulation networks:

- Back feeds from dual, parallel or ring feeds
- Old oil filled switchgear 
- Inadequately maintained switchgear 
- Manual switching, old switchgear that is not arc vented or arc contained 
- Incorrect or out of date reticulation drawings 
- Reticulation components not to standard or of adequate specification 
- Electrical protection is not adequate, i.e. settings, relay operation, ratings

Further Hazards:

- The ‘assumption’ that the power is OFF
- The use of incorrect test equipment 
- Inadequate test procedures 
- Inadequate isolation and locking out procedures 
- Inadequate safety procedures

The use of correct and approved testing apparatus

For voltages greater than 1000 volt, testing to prove the circuit is dead or alive should be by means of a voltage detecter which has been certified

for the correct application 

For phasing, phase comparators should be used that have been certified for the correct application 

Training on the correct use of voltage detectors and phase comparators should be implemented

Technoserve's electricians doing the testing are competent and authorised.


1)    Has the Permit to Work been obtained? 
2)    Has the PPE been checked? 
3)    Has the High Voltage Megger been tested? 
4)    Has the Low Voltage Megger been tested? 
5)    Has the Voltage Detector been tested? 
6)    Has the Voltage Detector been cleaned correctly? 
7)    Has the Phase Comparator been tested? 
8)    Has the Phase Comparator been cleaned correctly? 
9)    Have the Earthing Straps been checked and tested? 
10)  Has the Fire Extinguisher been checked? 
11)  Has the First Aid Box and Stretcher been checked? 
12)  Have you check the Reticulation Drawing for this Substation? 
13)  Have you identified the correct cables, circuit breakers and isolators? 
14)  Have you recorded all information and Permit to Work number into the Logbook? 
15)  Has the Time Setting been set to minimum on the CDG before Voltage Detection or Phasing is done? (Only in a no-load situation). 
16)  Has the Lockout Procedure been adhered to? 
17)  Has the Switching Procedure been adhered to? 

No work should be done on systems operating at voltages greater than 1000 volt until the apparatus has been isolated and made safe by a competend and authorised electrician to do MV switching in accordance with the code of practice and procedures for locking out and for MV switching.