Switchboard Manufacturers Test Assembly to SANS 61439-1&2

Due to increased inquiries and requests from customers in the electrical industry, it has become advantageous to transition from the current SANS 60439-1 to the new SANS 61439-1&2.

Switchboard Manufacturers KZN have tested their upgraded assembly system at the South African Bureau Of Standards (SABS) NETFA Laboratory in Bronkhorstspruit. 

Shane O’Reilly and Andrew MCarthy lead the team that designed and developed the assembly that passed the tests with ease.
The tests were completed under the auspices of the Short-Circuit Laboratory Manager, Seth Mnisi.
The following tests were completed:
1) Strength of Materials-10.2
  • Resistance to corrosion.
  • Thermal stability and resistance to abnormal heat and fire of insulting materials.
  • resistance to ultra-violet (UV) radiation.
  • resistance to mechanical impact.
  • durability of marking.
  • lifting and transport.

2) Degree of Protection of Enclosures- 10.3 

Validate protection against direct contact with live parts, as well as protection against ingress of solid foreign objects and liquids, in accordance with IEC 60529.

3) Clearances and Creepage Distances – 10.4 

Verify that the clearance and creepage distance enable the assembly to withstand the following:

  • Exceptional, transient overvoltage (lighting, HV operations),
  • Operating voltage and temporary overvoltage.

4) Protection against electrical shock and integrity of protective circuits- 10.5

Verify that:

  • The effective continuity between the exposed conductive parts of the assembly and the protective circuit.
  • The short-circuit withstand strength of protective circuit.

5) Incorporation of switching devices and components-10.6-

Ensure the compliance of equipment implementation in accordance with the rules of manufacture and EMC regulations, if applicable.

6) Internal electrical circuits and connections- 10.7

Verify the conformity of implementation and dimensioning of internal circuits and connections. The following should be carefully checked:

  • Short-circuit withstand strength.
  • Temperature-rise withstand.
  • The section of the neutral conductor.
  • Identification of conductors.

7) Terminals for external conductors-10.8

Verify the compliance of implementation and dimensioning of terminals for external conductors.

8) Dielectric properties-10.9

Test each type of circuit in the assembly to ensure:

  • Power-frequency withstand voltage.
  • Impulse withstand voltage.

9) Verification of temperature rise -10.10

Ensure:

  • Thermal stability of the loaded assembly,
  • That the temperatures are controlled on accessible parts, connections and equipment devices.

10) Short -circuit withstand strength-10.11

In comparison to a tested reference design or by testing, verify the level of withstand assigned to the reported short circuit current (unless excluded)

11) Electromagnetic compatibility -10.12

Verify EMC requirements via tests, Except if:

  • The incorporated devices and components comply with ECM requirements for the environment that has been specified;
  • Their installation and cabling comply with the specifications of the manufacturers.

12) Mechanical operation – 10.13

Verify via tests the mechanical operation of removable parts (including any insertion locking). Enclosures, partitions and fastenings should be able to withstand the wear-and-tear of normal use under short circuit condition.

All of the above test were completed and comply with SANS/IEC 61439-2012/2011 Edition 2- part 1 & 2 

The Tesla Microgrid solution to power Jouberton Community Health Centre

Jobourton’s Community Health Care Centre’s low voltage distribution boards are currently being built by Switchboard Manufacturers JHB. The facility will use a Tesla Microgrid to supply the facility with a reliable source of power if the grid supply were to fail.

The Tesla Microgrid turnkey solution has been used in many different environments around the world to supply reliable off-grid power to a vast array of different facilities.

[A typical PV array.]

What is the Tesla Microgrid?

The Tesla Microgrid is a turnkey solution provided by Tesla to enable a facility the capability of creating its own independent power grid, called a microgrid. The microgrid provides power with the use of a diesel generator, PV arrays and Tesla’s own Powerpacks which operate as battery supplies. These systems provide reliable power solutions to facilities which either have limited or no access to grid based power supplies.

The Tesla microgrid achieves this with the use of a set of controllers which monitor the power quality of the grid supply, generator, PV array and Powerpack. When one or more of these supplies aren’t outputing the desired power, the other supplies take over to support the facility. These controllers thus ensure that there is a continuous supply of power even when grid based power fails.

[Block diagram representing the interactions between the Microgrid controllers and the Distribution board. Image created by Author]

The Proposed System

The proposed system to be built can be seen in the above image. A 200kVA diesel generator, a PV array of 28 panels and a Tesla PowerPack system will make up the supplies to the microgrid. The control system consists of the Islanding Controller, Microgrid Controller and the Site Master Controller. These controllers ensure normal operation of the microgrid.

The flow of control in the Microgrid

As can be seen in the block diagram above, the microgrid control is a fairly complex system. The islanding controller is responsible for cutting the grid supply when it detects that the grid supply is under-performing. The Islanding Controller establishes the microgrid by opening the Islanding MCCB. By opening this MCCB the facility is completely cut off from the grid supply. To re-establish the grid supply the Islanding Controller needs to first ensure that the microgrid voltage is synchronised with the grid voltage before engaging the Islanding MCCB. Equipment damage could incur if the voltages are not synchronised.

The Microgrid controller controls the generator and PV inverters. Thus, as the name suggests, the Microgrid Controller ensures that the microgrid is operating optimally. The Site Master Controller controls the entire power system and processes input from the Microgrid and Islanding controllers. The Site Master Controller also controls the Powerpack inverters and thus engages the battery supply when need be. The Site Master Controller also thus ensures that all the inverter outputs are synchronised with each other and the grid supply and that the power produced is of optimal quality.

The Distribution Board

The main distribution board shown in the diagrams above is similar in working to a solar distribution board, as the flow of power is in reverse to a normal distribution board. This is an important factor to note as certain circuit breakers and current transformers (CT’s) are direction sensitive. The distribution board takes the various power sources feeding into it and then feeds them all onto a single bus-bar. The bus-bar then feeds into eighteen smaller distribution boards which serve the various buildings of the Health Centre. The Main distribution board and the smaller distribution boards will all be made by Switchboard Manufacturers. The other systems in place are either provided by Tesla or by the supplier of the PV contractor.

Article by: Jannes Smit, 3rd  year Electrical Engineering student at the University of the Witwatersrand.

jannes9000@gmail.com

25-Meter-Long MCC panel for the extension to Reeston WWTW

‘Switchboard Manufacturers’ Natal has completed a 25-meter-long MCC panel for the extension to Reeston Waste Water Treatment Works (WWTW) in Mdantsane, Eastern Cape.

The contract was awarded by S.A.M.E Water (Pty) Ltd who have worked on projects such as Olivantsvlei and Bushkoppies WWTW. The panels were manufactured under the guidance of SM Natal’s directors Shane O’reilly and Mark Rabie.

SM Natal utilised Siemens equipment for the project and ensured that each motor starter was equipped with a Simicode Electronic Overload. Both the motor starters and the Variable Speed Drives (VSD’s) were connected via Profinet to the PLC and Scada system.

SM Natal have been manufacturing MCC’s and MV panels in addition to their regular Low Voltage panels since 1997 and are fully equipped to handle low voltage projects of all sizes.

Contact Details:

Switchboard Manufacturers Natal                : 031 508 1520

Switchboard Manufacturers Cape Town      : 021 534 3313

Switchboard Manufacturers JHB                   : 011 827 5705