Intial Verification (Before Testing) Flashcards
- Connection of conductors
Ensure all connections are mechanically secure
- use a tug test
- use a torque driver for the connections
- visual examination
- connection too tight causing mechanical damage at the cable
Poor connections can cause arcing, will give a high resistance on r1+r2 test
- Identification of conductors
All conductors to be numbered or coloured to ID the cable
- T&E CPC must have green and yellow sleeving
- The use of sleeving or tape to ID strappers or switch wires
Used to correctly ID line, neutral and CPC for termination conductors.
- Routing of cables
Cables should be placed behind walls in straight lines, cable on the surface should be protected in trunking or conduit.
- Visual inspection of trunking/conduit to ensure it is complete and there is no damage
- Cables behind walls should be examed during consturction
- Cable in a wall must be within 150mm of a corner or ceiling
- Selection of conductors
Cables should be selected to ensure they can carry the current to the load without an overload of excessive volt drop
- Volt drop 3% for lights, 5% for everything else
- Check protective device’s current against the current carrying capacity of the cable
- Check the length of the run with the mV/A/M value of the cable and the load current
- Connection of Single Pole Devices
Visual inspection to ensure on single pole circuits the line conductor (not the neutral) is switched)
- Correct connection of accessories (Polarity)
Visual inspection to ensure the polarity of any connected accessory is correct
- Presence of fire barriers (not for domestic)
Visual inspection of barriers used to block holes for cable runs between areas of buildings that require fire barriers
- Methods of protection agains electric shock A
- SELV - 50v AC without an earth
- PELV - 50v AC or below with earth
- Visual inspection of transformer to ensure it is correctly rated
- Visual inspection to ensure correct earthing arrangement is present
- Double insulation - 2 layers of PVC, visual inspection to ensure there are no cracks
- Methods of protection agains electric shock B - Basic Protection
- Physical inspection of insulation of live parts and insulation around the cable to ensure there is no exposed conductor
- Visual inspection to ensure adequate protection by barrier or enclosure and protection of PVC single core cable using trunking or conduit, preventing them from being touched
- Visual inspection to ensure enclosure is complete and undamaged
- Physical inspection to ensure there are barriers over exposed bars preventing touch
- Methods of protection agains electric shock C - Fault Protection
Alternative sources
- Ensure there are no alternative sources such as solar panels, make sure there is additional isolation if they are present
Setting of protective devices
- Ensure the correct circuit breaker and overload rely are present
- Ensure the correct rating of protective devices is used
- Overload relys should be set to the current rating of the motor
Automatic disconnetion of the supply
Earth fault loop impedence
- A low impedence is needed to give a high fault current, the large over current flows through the circuit rupturing the protective device in 0.4 or 5s
- If earth loop impedance value is to high the circuit will either take to long to trip or won’t trip at all
Earthing arrangements
Earth electrode - visual inspection of earth rod
Earthing conductor - earth supply from supply company
Circuit protective conductor - visual inspection of CPC
Protective bonding conductor - visual inspection
Supplementary bonding conductors - visual inspection
Exposed conductive parts are connected to earthing arrangements - visual inspection
Electrical seperation
Protection through a transformer where the earth stops on the primary side
- must be used in bathrooms
Additional protection RCDs
must be a 30mA RCD - visual inspection
Prevention of mutual detrimental influence
Visual inspection to ensure -
Seperation of electrical cables and telecom cables
Consumer units should be away from water pipes
Presence of appropriate devices for isolation and switching correctly located
visual inspection to ensure devices are there and appropriately located
Presence of undervoltage protection devices (not domestic)
For specalist areas, particularly used with 3ph motors, when these motors are switched on they can induce a volt drop which would increase current potentially tripping the supply breaker, these sense the volt drop and trip before it happens.
Visual inspection
Labelling of protective devices, switches
Visual inspection to ensure correct labelling is in place
Selection of equipment and protective measures appropriate to external influences
Entrances for vermin should be filled particularly holes for cables to enter buildings
Adequacy of access to switchgear and equipment (including consumer unit)
Access to switch gear should not be restricted, doors open to 90
Consumer unit front face should be able to be open and be removed
Presence of danger notices and other warnings
Visual inspection of test date labels, earth clamps label, voltage warning for 400v or higher
Presence of diagram, instructions and similar info
3 main drawings - lighting, power, containment
OM (operating and maintenance manual)
Selection and erection of wiring systems
Visual inspection to ensure trunking, conduit or containment has been correctly installed and that metal conduit or trunking has an earth link.
Selection and installation of suitable surge protection device
visual inspection to ensure SPD is there is necessary.
